Three-dimensional fibrous mats comprising copper-doped titanium dioxide, and methods of making and use thereof

Abstract

The disclosed subject matter relates to three-dimensional fibrous mats comprising copper-doped titanium dioxide, and methods of making and use thereof. For example, disclosed herein are 3D nanotech blankets for photocatalysis. For example, disclosed herein are three-dimensional fibrous mats comprising a plurality of fibers, each of the fibers comprising Cu-doped TiO2. In some examples, each of the fibers comprises a first plurality of crystallites and a second plurality of crystallites, the first plurality of crystallites being anatase and the second plurality of crystallites being brookite. In some examples, the three-dimensional fibrous mat floats on water. In some examples, the three-dimensional fibrous mat has an absorption band that overlaps with at least a portion of the solar spectrum. Also disclosed herein are methods of making and use of any of the three-dimensional fibrous mats disclosed herein.

Description

[0001] THREE-DIMENSIONAL FIBROUS MATS COMPRISING COPPER-DOPED TITANIUM DIOXIDE, AND METHODS OF MAKING AND USE THEREOF CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to U.S. Provisional Application No.

[0003] 63 / 789,020 filed April 15, 2025, which is hereby incorporated herein by reference in its entirety.

[0004] STATEMENT OF GOVERNMENT SUPPORT

[0005] This invention was made with government support under grant / contract no. 2014506 awarded by the National Science Foundation. The government has certain rights in the invention.

[0006] BACKGROUND

[0007] Titanium dioxide (TiO?) is a widely used functional oxide with a broad range of applications including solar cells, gas sensors, photocatalysis, and self-cleaning technologies. The bandgap of TiCh requires excitation by ultraviolet light, rendering visible light unusable to create electron-hole pairs. Second, the short lifetime of the photogenerated electrons and holes in TiO2 nanoparticles hinders their effective utilization. Finally, the lack of an ideal selfsupported nanostructure that can be easily recovered remains a challenge for TiCh nanostructures. The compositions, devices, and methods discussed herein address these and other needs.

[0008] SUMMARY

[0009] In accordance with the purposes of the disclosed compositions, methods, and systems as embodied and broadly described herein, the disclosed subject matter relates three-dimensional fibrous mats comprising copper-doped titanium dioxide, and methods of making and use thereof. For example, disclosed herein are 3D nanotech blankets for photocatalysis.

[0010] For example, disclosed herein are three-dimensional fibrous mats comprising a plurality of fibers, each of the fibers comprising Cu-doped TiCh.

[0011] In some examples, the Cu dopant is present in an amount of from greater than 0 to 10%, for example 2%.

[0012] In some examples, the plurality of fibers are substantially free of copper oxides (e.g., CuO, Cu2O, or a combination thereof).

[0013] In some examples, the plurality of fibers are substantially free of impurities and / or organic contaminants.

[0014] In some examples, the distribution of Ti, O, and Cu elements is substantially uniform throughout the plurality of fibers (e.g., throughout each of the fibers).

[0015] In some examples, each of the fibers comprises a plurality of crystallites.In some examples, each of the fibers comprises a first plurality of crystallites and a second plurality of crystallites, the first plurality of crystallites being anatase and the second plurality of crystallites being brookite. In some examples, the first plurality of crystallites and the second plurality of crystallites as each substantially uniformly distributed within each of the fibers. In some examples, the anatase crystallites have an average crystallite size of from 5 to 30 nm, such as from 5 to 15 nm, such as from 9 to 15 nm. In some examples, the brookite crystallites have an average crystallite size of from 5 to 30 nm, such as from 10 to 30 nm.

[0016] In some examples, the plurality of fibers have an average diameter of from 30 to 500 nanometers, such as from 60 to 190 nm.

[0017] In some examples, the plurality of fibers have an average length of 10 nanometers to 10 meters, such as from 100 nanometers to 100 micrometers, such as from 100 nanometers to 10 micrometers.

[0018] In some examples, the plurality of fibers have an average aspect ratio (e.g., average length divided by average outer diameter) of greater than 1.

[0019] In some examples, the plurality of fibers have a high average aspect ratio (e.g., an aspect ratio of 100 or more).

[0020] In some examples, the three-dimensional fibrous mat floats on water.

[0021] In some examples, the three-dimensional fibrous mat has an absorption band that overlaps with at least a portion of the solar spectrum.

[0022] In some examples, the three-dimensional fibrous mat has an absorption band that overlaps with at least a portion of the visible light portion of the electromagnetic spectrum, such as at least a portion of the visible light portion of the solar spectrum.

[0023] In some examples, photogenerated electrons and holes have a longer lifetime in the plurality of fibers relative to those in a plurality of fibers without Cu-doping.

[0024] In some examples, the three-dimensional fibrous mat is non-woven.

[0025] In some examples, the three-dimensional fibrous mat is self-supported.

[0026] In some examples, the three-dimensional fibrous mat is electrospun.

[0027] Also disclosed herein are methods of making any of the three-dimensional fibrous mats disclosed herein.

[0028] In some examples, the method comprises electrospinning, such as blend electrospinning. In some examples, the method comprises high-throughput electrospinning.

[0029] In some examples, the method further comprises heat treating.

[0030] In some examples, the method comprises preparing a Cu-doped TiCh precursor solution, electrospinning the Cu-doped TiCh precursor solution to form a precursor three-dimensionalfibrous mat comprising a plurality of precursor fibers, and heat treating the plurality of precursor fibers to form the three-dimensional fibrous mat comprising the plurality of Cu-doped TiCh fibers.

[0031] Also disclosed herein are methods of use of any of the three-dimensional fibrous mats disclosed herein.

[0032] In some examples, the method comprises using the three-dimensional fibrous mat as a photocatalyst.

[0033] In some examples, the method comprises using the three-dimensional fibrous mat as a photocatalyst for photocatalytic fuel generation.

[0034] In some examples, the method comprises contacting the photocatalyst with a fuel precursor to form a mixture and illuminating the mixture with light that overlaps with at least a portion of the absorption band of the photocatalyst, thereby converting the fuel precursor to a fuel.

[0035] In some examples, the fuel precursor comprises water.

[0036] In some examples, the light is provided by a light source, such as an artificial light source or a natural light source.

[0037] In some examples, the light comprises sunlight.

[0038] In some examples, the fuel comprises hydrogen and the method comprises using the three-dimensional fibrous mat as a photocatalyst for photocatalytic hydrogen generation.

[0039] In some examples, the fuel precursor comprises water, the fuel comprises hydrogen, and the method comprises using the three-dimensional fibrous mat as a photocatalyst for photocatalytic water splitting for hydrogen generation.

[0040] In some examples, the method comprises using the three-dimensional fibrous mat as a photocatalyst for water splitting, hydrogen generation, or a combination thereof.

[0041] In some examples, the method comprises using the three-dimensional fibrous mat as a photocatalyst for solar water splitting, solar hydrogen generation, or a combination thereof.

[0042] In some examples, the method comprises using the three-dimensional fibrous mat as a photocatalyst for water purification and / or water remediation.

[0043] In some examples, the method comprises contacting the photocatalyst with contaminated water to form a mixture and illuminating the mixture with light that overlaps with at least a portion of the absorption band of the photocatalyst, thereby degrading at least a portion of the contamination to purify the water.In some examples, the method comprises using the three-dimensional fibrous mat as a photocatalyst for decomposition of an organic compound, such as a complex organic pollutant, such as petroleum hydrocarbons and / or dyes.

[0044] In some examples, the method comprises using the three-dimensional fibrous mat as an advanced battery electrode.

[0045] In some examples, the method comprises using the three-dimensional fibrous mat as an antimicrobial and / or smart (e.g., self-cleaning) coating.

[0046] Additional advantages of the disclosed compositions, systems, and methods will be set forth in part in the description which follows, and in part will be obvious from the description. The advantages of the disclosed compositions, systems, and methods will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosed compositions, systems, and methods, as claimed.

[0047] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

[0048] BRIEF DESCRIPTION OF THE FIGURES

[0049] The accompanying figures, which are incorporated in and constitute a part of this specification, illustrate several aspects of the disclosure, and together with the description, serve to explain the principles of the disclosure.

[0050] Figure 1. XRD spectra of Pure and Cu-doped TiO2 nanofibers heat-treated at 500°C [the phases are identified using the PDF file no. 98-000-0081, 98-000-0128, and 98-000-0375 for anatase (A), brookite (B), and rutile (R) respectively].

[0051] Figure 2a-Figure 2b. (Figure 2a) High-resolution TEM Image showing (101) plane of anatase phase of pure TiCh nanofibers; (Figure 2b) the SAED pattern of the nanofibers.

[0052] Figure 3a-Figure 3c. Figure 3a) TEM image of Cu-doped TiCh heat-treated nanofiber; Figure 3b) SAED pattern of Cu-doped TiCh nanofibers; Figure 3c) high-resolution TEM depicts crystallites of brookite and anatase phase, respectively.

[0053] Figure 4. Dark Field image of the brookite phase in the Cu-Doped TiCh Nanofibers. Figure 5a-Figure 5c. Figure 5a-Figure 5b) Cu-doped TiCh heat-treated nanofiber blankets, Figure 5c) SEM image of the nanofiber.

[0054] Figure 6. EDX elemental mapping of the Cu Doped TiCh electrospun nanofibers.Figure 7a-Figure 7h. Figure 7a) Survey XPS spectrum of pure TiCh nanofibrous mat, Figure 7b- Figure 7d) High-resolution deconvoluted XPS spectra of Ti 2p, O ls, and Cu 2p for pure TiO?; Figure 7e) wide scan XPS survey of Cu-doped TiO2 nanofibrous mats; and Figure 7f-Figure 7h) deconvoluted XPS spectra of Ti 2p, O ls, and Cu 2p for Cu-doped TiO2 nanofibrous mat, respectively.

[0055] Figure 8a-Figure 8b. Figure 8a, Figure 8b) Chronoamperometry of undoped and Cu-doped TiO2 nanofibers, respectively.

[0056] Figure 9a-Figure 9d. Degradation of Methylene blue. Figure 9a) Qualitative comparison between the Cu-doped TiO2 and the commercial P25 Degussa TiO2 and a container with no photocatalyst; Figure 9b) UV Filter On and Figure 9c) UV Filter Off -240 min total Comparing mixed anatase and brookite of Cu-doped TiO2, anatase of undoped TiO2 and P25 Degussa powder; Figure 9d) Visible light versus Full Spectrum comparison of Cu-doped TiO2 with P25 powder.

[0057] Figure 10. (Left) Pure TiO2 Nanofibrous Mat (Mid) 2% Cu Doped TiO2 (Right) Commercial P25 Degussa Nano powder TiO2 on aluminum foils.

[0058] Figure lla-Figure 11b. EDX Spectra of (Figure Ila) as-prepared and (Figure 11b) heat-treated Cu-doped TiCh nanofibers.

[0059] Figure 12. UV - VIS spectra of heat-treated pure and Cu-doped TiCh nanofibers.

[0060] Figure 13. Cyclic voltammetry study of undoped and Cu-doped TiCh within 0.1 KOH solution.

[0061] DETAILED DESCRIPTION

[0062] Before the present compositions, methods, and systems are disclosed and described, it is to be understood that the aspects described below are not limited to specific synthetic methods or specific reagents, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

[0063] Also, throughout this specification, various publications are referenced. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which the disclosed matter pertains. The references disclosed are also individually and specifically incorporated by reference herein for the material contained in them that is discussed in the sentence in which the reference is relied upon.

[0064] In this specification and in the claims that follow, reference will be made to a number of terms, which shall be defined to have the following meanings.Throughout the description and claims of this specification the word “comprise” and other forms of the word, such as “comprising” and “comprises,” means including but not limited to, and is not intended to exclude, for example, other additives, components, integers, or steps. As used in the specification and in the claims, the term “comprising” can include the aspects “consisting of’ and “consisting essentially of.”

[0065] As used in the description and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a composition” includes mixtures of two or more such compositions, reference to “an agent” includes mixtures of two or more such agents, reference to “the component” includes mixtures of two or more such components, and the like.

[0066] “Optional” or “optionally” means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event or circumstance occurs and instances where it does not.

[0067] Ranges can be expressed herein as from “about” one particular value, and / or to “about” another particular value. By “about” is meant within 5% of the value, e.g., within 4, 3, 2, or 1% of the value. When such a range is expressed, another aspect includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0068] “Exemplary” means “an example of’ and is not intended to convey an indication of a preferred or ideal embodiment. “Such as” is not used in a restrictive sense, but for explanatory purposes.

[0069] Values can be expressed herein as an “average” value. “Average” generally refers to the statistical mean value.

[0070] By “substantially” is meant within 5%, e.g., within 4%, 3%, 2%, or 1%.

[0071] It is understood that throughout this specification the identifiers “first” and “second” are used solely to aid in distinguishing the various components and steps of the disclosed subject matter. The identifiers “first” and “second” are not intended to imply any particular order, amount, preference, or importance to the components or steps modified by these terms.

[0072] References in the specification and concluding claims to parts by weight of a particular element or component in a composition denotes the weight relationship between the element or component and any other elements or components in the composition or article for which a part by weight is expressed. Thus, in a compound containing 2 parts by weight of component X and 5parts by weight component Y, X and Y are present at a weight ratio of 2:5, and are present in such ratio regardless of whether additional components are contained in the compound.

[0073] A weight percent (wt. %) of a component, unless specifically stated to the contrary, is based on the total weight of the formulation or composition in which the component is included.

[0074] The term “or combinations thereof’ as used herein refers to all permutations and combinations of the listed items preceding the term. For example, “A, B, C, or combinations thereof’ is intended to include at least one of: A, B, C, AB, AC, BC, or ABC, and if order is important in a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB.

[0075] Continuing with this example, expressly included are combinations that contain repeats of one or more item or term, such as BB, AAA, AB, BBC, AAABCCCC, CBBAAA, CAB ABB, and so forth. The skilled artisan will understand that typically there is no limit on the number of items or terms in any combination, unless otherwise apparent from the context.

[0076] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0077] Compositions, Systems, and Methods

[0078] Disclosed herein are compositions, systems, and methods. For example, disclosed herein are three-dimensional fibrous mats comprising copper-doped titanium dioxide, and methods of making and use thereof. For example, disclosed herein are compositions, systems, and methods for 3D nanotech blankets for photocatalysis.

[0079] For example, disclosed herein are three-dimensional fibrous architectures of nanostructured Cu-TiCh.

[0080] As used herein, “nanostructured” means any structure with one or more nanosized features. A nanosized feature can be any feature with at least one dimension less than 1 micrometer (pm) in size. For example, a nanosized feature can comprise a nanowire, nanotube, nanoparticle, nanopore, and the like, or combinations thereof. As such, the nanostructured material can comprise, for example, a nanowire, nanotube, nanoparticle, nanopore, or a combination thereof. In some examples, the nanostructured material can comprise a material that is not nanosized but has been modified with a nanowire, nanotube, nanoparticle, nanopore, or a combination thereof.

[0081] For example, disclosed herein are three-dimensional fibrous mats comprising a plurality of fibers, each of the fibers comprising Cu-doped TiCh. In some examples, the fibers are nanostructured.In some examples, the Cu dopant is present in an amount of greater than 0% (atomic percent) (e.g., 0.1% or more, 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, or 9% or more). In some examples, the Cu dopant is present in an amount of 1% or more. In some examples, the Cu dopant is present in an amount of 2% or more. In some examples, the Cu dopant is present in an amount of 10% or less (e.g., 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less). In some examples, the Cu dopant is present in an amount of 5% or less. In some examples, the Cu dopant is present in an amount of 3% or less. The amount of Cu can range from any of the minimum values described above to any of the maximum values described above. For example, the Cu dopant can be present in an amount of from greater than 0 to 10% (e.g., from greater than 0% to 5%, from 5% to 10%, from greater than 0% to 2%, from 2% to 4%, from 4% to 6%, from 6% to 8%, from 8% to 10%, from greater than 0% to 8%, from greater than 0% to 6%, from greater than 0% to 4%, from 0.1% to 10%, from 1% to 10%, from 2% to 10%, from 4% to 10%, from 6% to 10%, from 0.1% to 9%, from 1% to 8%, or from 1% to 3%). In some examples, the Cu dopant is present in an amount o from greater than 0 to 5%. In some examples, the Cu dopant is present in an amount of from 1% to 3%. In some examples, the Cu dopant is present in an amount of 2%.

[0082] In some examples, the plurality of fibers are substantially free of copper oxides (e.g., CuO, Cu2O, or a combination thereof).

[0083] In some examples, the plurality of fibers are substantially free of impurities and / or organic contaminants.

[0084] In some examples, the distribution of Ti, O, and Cu elements is substantially uniform throughout the plurality of fibers (e.g., throughout each of the fibers).

[0085] In some examples, each of the fibers comprises a plurality of crystallites.

[0086] The crystallites can have an average crystallite size. “Average crystallite size” and “mean crystallite size” are used interchangeably herein, and generally refer to the statistical mean crystallite size of the particles in a population of crystallites. For example, the average crystallite size for a plurality of crystallites with a substantially spherical shape can comprise the average diameter of the plurality of crystallites. As used herein, the diameter of a crystallite can refer to the largest linear distance between two points on the surface of the crystallite. For an anisotropic crystallite, the average crystallite size can refer to, for example, the average maximum dimension of the crystallite (e.g., the length of a rod shaped crystallite, the diagonal of a cube shape crystallite, the bisector of a triangular shaped crystallite, etc.) Mean crystallite size can bemeasured using methods known in the art, such as evaluation by electron microscopy (e.g., scanning electron microscopy, transmission electron microscopy, etc.).

[0087] In some examples, the crystallites can be substantially monodisperse. “Monodisperse” and “homogeneous size distribution,” as used herein, and generally describe a population of crystallites where all of the crystallites have the same or nearly the same crystallite size. As used herein, a monodisperse distribution refers to crystallite distributions in which 80% of the distribution (e.g., 85% of the distribution, 90% of the distribution, or 95% of the distribution) lies within 25% of the average crystallite size (e.g., within 20% of the average crystallite size, within 15% of the average crystallite size, within 10% of the average crystallite size, or within 5% of the average crystallite size).

[0088] In some examples, each of the fibers comprises a first plurality of crystallites and a second plurality of crystallites, the first plurality of crystallites being anatase and the second plurality of crystallites being brookite. In some examples, the first plurality of crystallites and the second plurality of crystallites as each substantially uniformly distributed within each of the fibers.

[0089] In some examples, the anatase crystallites have an average crystallite size of 5 nanometers (nm) or more (e.g., 6 nm or more, 7 nm or more, 8 nm or more, 9 nm or more, 10 nm or more, 11 nm or more, 12 nm or more, 13 nm or more, 14 nm or more, 15 nm or more, 16 nm or more, 17 nm or more, 18 nm or more, 19 nm or more, 20 nm or more, 21 nm or more, 22 nm or more, 23 nm or more, 24 nm or more, 25 nm or more, 26 nm or more, 27 nm or more, 28 nm or more, or 29 nm or more). In some examples, the anatase crystallites have an average crystallite size of 9 nanometers (nm) or more. In some examples, the anatase crystallites have an average crystallite size of 30 nm or less (e.g., 29 nm or less, 28 nm or less, 27 nm or less, 26 nm or less, 25 nm or less, 24 nm or less, 23 nm or less, 22 nm or less, 21 nm or less, 20 nm or less, 19 nm or less, 18 nm or less, 17 nm or less, 16 nm or less, 15 nm or less, 14 nm or less, 13 nm or less, 12 nm or less, 11 nm or less, 10 nm or less, 9 nm or less, 8 nm or less, 7 nm or less, or 6 nm or less). In some examples, the anatase crystallites have an average crystallite size of 15 nm or less. The average crystallite size of the anatase crystallites can range from any of the minimum values described above to any of the maximum values described above. For example, the anatase crystallites can have an average crystallite size of from 5 to 30 nanometers (e.g., from 5 to 17 nm, from 17 to 30 nm, from 5 to 10 nm, from 10 to 15 nm, from 15 to 20 nm, from 20 to 25 nm, from 25 to 30 nm, from 5 to 25 nm, from 5 to 20 nm, from 5 to 15 nm, from 10 to 30 nm, from 15 to 30 nm, from 20 to 30 nm, or from 10 to 25 nm). In some examples, the anatase crystallites can have an average crystallite size of from 5 to 15 nm (e.g., from 5 to 10 nm, from 10 to 15 nm,from 5 to 7 nm, from 7 to 9 nm, from 9 to 11 nm, from 11 to 13 nm, from 13 to 15 nm, from 7 to 15 nm, from 9 to 15 nm, from 11 to 15 nm, from 5 to 13 nm, from 5 to 11 nm, from 5 to 9 nm, from 6 to 14 nm, or from 7 to 13 nm). In some examples, the anatase crystallites have an average crystallite size of from 9 to 15 nm.

[0090] In some examples, the brookite crystallites have an average crystallite size of 5 nm or more (e.g., 6 nm or more, 7 nm or more, 8 nm or more, 9 nm or more, 10 nm or more, 11 nm or more, 12 nm or more, 13 nm or more, 14 nm or more, 15 nm or more, 16 nm or more, 17 nm or more, 18 nm or more, 19 nm or more, 20 nm or more, 21 nm or more, 22 nm or more, 23 nm or more, 24 nm or more, 25 nm or more, 26 nm or more, 27 nm or more, 28 nm or more, or 29 nm or more). In some examples, the brookite crystallites have an average crystallite size of 10 nm or more. In some examples, the brookite crystallites have an average crystallite size of 30 nm or less (e.g., 29 nm or less, 28 nm or less, 27 nm or less, 26 nm or less, 25 nm or less, 24 nm or less, 23 nm or less, 22 nm or less, 21 nm or less, 20 nm or less, 19 nm or less, 18 nm or less, 17 nm or less, 16 nm or less, 15 nm or less, 14 nm or less, 13 nm or less, 12 nm or less, or 11 nm or less). The average crystallite size of the brookite crystallites can range from any of the minimum values described above to any of the maximum values described above. For example, the brookite crystallites can have an average crystallite size of from 5 to 30 nanometers (e.g., from 5 to 17 nm, from 17 to 30 nm, from 5 to 10 nm, from 10 to 15 nm, from 15 to 20 nm, from 20 to 25 nm, from 25 to 30 nm, from 5 to 25 nm, from 5 to 20 nm, from 5 to 15 nm, from 10 to 30 nm, from 15 to 30 nm, from 20 to 30 nm, or from 10 to 25 nm). In some examples, the brookite crystallites can have an average crystallite size of from 10 to 30 nm (e.g., from 10 to 20 nm, from 20 to 30 nm, from 10 to 15 nm, from 15 to 20 nm, from 20 to 25 nm, from 25 to 30 nm, from 15 to 30 nm, from 20 to 30 nm, from 10 to 25 nm, from 10 to 20 nm, from 12 to 28 nm, or from 15 to 25 nm).

[0091] In some examples, the anatase crystallites can have an average crystallite size of from 5 to 30 nm, such as from 5 to 15 nm, and the brookite crystallites can have an average crystallite size of from 5 to 30 nm, such as from 10 to 30 nm.

[0092] In some examples, the anatase crystallites have an average crystallite size that is smaller than that of the brookite crystallites. In some examples, the anatase crystallites can have an average crystallite size of from 5 to 15 nm and the brookite crystallites can have an average crystallite size of from 10 to 30 nm. In some examples, the anatase crystallites can have an average crystallite size of from 9 to 15 nm and the brookite crystallites can have an average crystallite size of from 10 to 30 nm.In some examples, the plurality of fibers have an average diameter of 30 nm or more (e.g., 40 nm or more, 50 nm or more, 60 nm or more, 70 nm or more, 80 nm or more, 90 nm or more, 100 nm or more, 110 nm or more, 120 nm or more, 130 nm or more, 140 nm or more, 150 nm or more, 160 nm or more, 170 nm or more, 180 nm or more, 190 nm or more, 200 nm or more, 225 nm or more, 250 nm or more, 275 nm or more, 300 nm or more, 325 nm or more, 350 nm or more, 375 nm or more, 400 nm or more, 425 nm or more, 450 nm or more, or 475 nm or more). In some examples, the plurality of fibers have an average diameter of 60 nm or more. In some examples, the plurality of fibers have an average diameter of 500 nm or less (e.g., 475 nm or less, 450 nm or less, 425 nm or less, 400 nm or less, 375 nm or less, 350 nm or less, 325 nm or less, 300 nm or less, 275 nm or less, 250 nm or less, 225 nm or less, 200 nm or less, 190 nm or less, 180 nm or less, 170 nm or less, 160 nm or less, 150 nm or less, 140 nm or less, 130 nm or less, 120 nm or less, 110 nm or less, 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 50 nm or less, or 40 nm or less). In some examples, the plurality of fibers have an average diameter of 190 nm or less. The average diameter of the plurality of fibers can range from any of the minimum values described above to any of the maximum values described above. For example, the plurality of fibers can have an average diameter of from 30 to 500 nanometers (e.g., from 30 to 250 nm, from 250 to 500 nm, from 30 to 100 nm, from 100 to 200 nm, from 200 to 300 nm, from 300 to 400 nm, from 400 to 500 nm, from 30 to 400 nm, from 30 to 300 nm, from 30 to 200 nm, from 50 to 500 nm, from 100 to 500 nm, from 200 to 500 nm, from 300 to 500 nm, from 40 to 450 nm, from 50 to 400 nm, from 50 to 300 nm, from 50 to 200 nm, or from 60 to 190 nm). In some examples, the plurality of fibers can have an average diameter of from 60 to 190 nm.

[0093] In some examples, the plurality of fibers have an average length of 10 nanometers or more (e.g., 20 nanometers or more, 30 nanometers or more, 40 nanometers or more, 50 nanometers or more, 60 nanometers or more, 70 nanometers or more, 80 nanometers or more, 90 nanometers or more, 100 nanometers or more, 125 nanometers or more, 150 nanometers or more, 175 nanometers or more, 200 nanometers or more, 300 nanometers or more, 400 nanometers or more, 500 nanometers or more, 600 nanometers or more, 700 nanometers or more, 800 nanometers or more, 900 nanometers or more, 1 micrometer or more, 2 micrometers or more, 3 micrometers or more, 4 micrometers or more, 5 micrometers or more, 10 micrometers or more, 15 micrometers or more, 20 micrometers or more, 25 micrometers or more, 30 micrometers or more, 35 micrometers or more, 40 micrometers or more, 45 micrometers or more, 50 micrometers or more, 60 micrometers or more, 70 micrometers or more, 80 micrometers or more, 90 micrometers or more, 100 micrometers or more, 125 micrometers ormore, 150 micrometers or more, 175 micrometers or more, 200 micrometers or more, 300 micrometers or more, 400 micrometers or more, 500 micrometers or more, 600 micrometers or more, 700 micrometers or more, 800 micrometers or more, 900 micrometers or more, 1 millimeter or more, 2 millimeters or more, 3 millimeters or more, 4 millimeters or more, 5 millimeters or more, 10 millimeters or more, 15 millimeters or more, 20 millimeters or more, 25 millimeters or more, 30 millimeters or more, 35 millimeters or more, 40 millimeters or more, 45 millimeters or more, 50 millimeters or more, 60 millimeters or more, 70 millimeters or more, 80 millimeters or more, 90 millimeters or more, 100 millimeters or more, 125 millimeters or more, 150 millimeters or more, 175 millimeters or more, 200 millimeters or more, 300 millimeters or more, 400 millimeters or more, 500 millimeters or more, 600 millimeters or more, 700 millimeters or more, 800 millimeters or more, 900 millimeters or more, 1 meter or more, 2 meters or more, 3 meters or more, 4 meters or more, or 5 meters or more). In some examples, the plurality of fibers have an average length of 100 nanometers or more. In some examples, the plurality of fibers have an average length of 10 meters or less (e.g., 5 meters or less, 4 meters or less, 3 meters or less, 2 meters or less, 1 meters or less, 900 millimeters or less, 800 millimeters or less, 700 millimeters or less, 600 millimeters or less, 500 millimeters or less, 400 millimeters or less, 300 millimeters or less, 200 millimeters or less, 175 millimeters or less, 150 millimeters or less, 125 millimeters or less, 100 millimeters or less, 90 millimeters or less, 80 millimeters or less, 70 millimeters or less, 60 millimeters or less, 50 millimeters or less, 45 millimeters or less, 40 millimeters or less, 35 millimeters or less, 30 millimeters or less, 25 millimeters or less, 20 millimeters or less, 15 millimeters or less, 10 millimeters or less, 5 millimeters or less, 4 millimeters or less, 3 millimeters or less, 2 millimeters or less, 1 millimeter or less, 900 micrometers or less, 800 micrometers or less, 700 micrometers or less, 600 micrometers or less, 500 micrometers or less, 400 micrometers or less, 300 micrometers or less, 200 micrometers or less, 175 micrometers or less, 150 micrometers or less, 125 micrometers or less, 100 micrometers or less, 90 micrometers or less, 80 micrometers or less, 70 micrometers or less, 60 micrometers or less, 50 micrometers or less, 45 micrometers or less, 40 micrometers or less, 35 micrometers or less, 30 micrometers or less, 25 micrometers or less, 20 micrometers or less, 15 micrometers or less, 10 micrometers or less, 5 micrometers or less, 4 micrometers or less, 3 micrometers or less, 2 micrometers or less, 1 micrometer or less, 900 nanometers or less, 800 nanometers or less, 700 nanometers or less, 600 nanometers or less, 500 nanometers or less, 400 nanometers or less, 300 nanometers or less, 200 nanometers or less, 175 nanometers or less, 150 nanometers or less, 125 nanometers or less, 100 nanometers or less, 90 nanometers or less, 80 nanometers or less, 70 nanometers or less, 60 nanometers or less, 50 nanometers or less, 45nanometers or less, 40 nanometers or less, 35 nanometers or less, 30 nanometers or less, 25 nanometers or less, or 20 nanometers or less). In some examples, the plurality of fibers have an average length of 100 micrometers or less. In some examples, the plurality of fibers have an average length of 10 micrometers or less. The average length of the plurality of fibers can range from any of the minimum values described above to any of the maximum values described above. For example, the plurality of fibers have an average length of from 10 nanometers to 10 meters (e.g., from 10 nanometers to 1 millimeter, from 1 millimeter to 10 meters, from 10 nanometers to 10 micrometers, from 10 micrometers to 10 millimeters, from 10 millimeters to 10 meters, from 100 nanometers to 10 meters, from 1 micrometer to 10 meters, from 10 micrometers to 10 meters, from 100 micrometers to 10 meters, from 100 millimeters to 10 meters, or from 100 nanometers to 100 micrometers). In some examples, the plurality of fibers have an average length of from 100 nanometers to 100 micrometers (e.g., from 100 nanometers to 1 micrometer, from 1 micrometer to 100 micrometers, from 100 nanometers to 500 nanometers, from 500 nanometers to 1 micrometer, from 1 micrometer to 50 micrometers, from 50 micrometers to 100 micrometers, from 100 nanometers to 50 micrometers, from 100 nanometers to 10 micrometers, from 500 nanometers to 100 micrometers, from 200 nanometers to 90 micrometers, from 300 nanometers to 80 micrometers, or from 500 nanometers to 50 micrometers). In some examples, the plurality of fibers have an average length of from 100 nanometers to 10 micrometers.

[0094] In some examples, the plurality of fibers can have an average diameter of from 30 to 500 nanometers and an average length of from 10 nanometers to 10 meters. In some examples, the plurality of fibers can have an average diameter of from 60 to 190 nm and an average length of from 10 nanometers to 10 meters.

[0095] In some examples, the plurality of fibers can have an average diameter of from 30 to 500 nanometers and an average length of from 100 nanometers to 100 micrometers. In some examples, the plurality of fibers can have an average diameter of from 60 to 190 nm and an average length of from 100 nanometers to 10 micrometers.

[0096] In some examples, the plurality of fibers have an average aspect ratio (e.g., average length divided by average outer diameter) of greater than 1. In some examples, the plurality of fibers have a high average aspect ratio (e.g., an aspect ratio of 100 or more).

[0097] In some examples, the three-dimensional fibrous mat floats on water.

[0098] In some examples, the three-dimensional fibrous mat has an absorption band that overlaps with at least a portion of the solar spectrum.In some examples, the three-dimensional fibrous mat has an absorption band that overlaps with at least a portion of the visible light portion of the electromagnetic spectrum, such as at least a portion of the visible light portion of the solar spectrum.

[0099] In some examples, photogenerated electrons and holes have a longer lifetime in the plurality of fibers relative to those in a plurality of fibers without Cu-doping.

[0100] In some examples, the three-dimensional fibrous mat is non-woven.

[0101] In some examples, the three-dimensional fibrous mat is self-supported.

[0102] In some examples, the three-dimensional fibrous mat is electrospun.

[0103] Also disclosed herein are methods of making any of the three-dimensional fibrous mats disclosed herein. In some examples, the method comprises electrospinning, such as blend electrospinning. In some examples, the method comprises high-throughput electrospinning. In some examples, the method further comprises heat treating. In some examples, the method comprises preparing a Cu-doped TiCh precursor solution, electrospinning the Cu-doped TiCh precursor solution to form a precursor three-dimensional fibrous mat comprising a plurality of precursor fibers, and heat treating the plurality of precursor fibers to form the three-dimensional fibrous mat comprising the plurality of Cu-doped TiCh fibers.

[0104] In some examples, the precursor solution can be a sol. In some examples, the methods can comprise using a sol-gel based slurry to cover fibers and then heat treating (e.g., calcining).

[0105] Also disclosed herein are methods of use of any of the three-dimensional fibrous mats disclosed herein. In some examples, the method comprises using the three-dimensional fibrous mat as a photocatalyst.

[0106] In some examples, the method comprises using the three-dimensional fibrous mat as a photocatalyst for photocatalytic fuel generation. In some examples, the method comprises contacting the photocatalyst with a fuel precursor to form a mixture and illuminating the mixture with light that overlaps with at least a portion of the absorption band of the photocatalyst, thereby converting the fuel precursor to a fuel. In some examples, the fuel precursor comprises water. In some examples, the light is provided by a light source, such as an artificial light source or a natural light source. In some examples, the light comprises sunlight. In some examples, the fuel comprises hydrogen and the method comprises using the three-dimensional fibrous mat as a photocatalyst for photocatalytic hydrogen generation. In some examples, the fuel precursor comprises water, the fuel comprises hydrogen, and the method comprises using the three-dimensional fibrous mat as a photocatalyst for photocatalytic water splitting for hydrogen generation.In some examples, the method comprises using the three-dimensional fibrous mat as a photocatalyst for water splitting, hydrogen generation, or a combination thereof.

[0107] In some examples, the method comprises using the three-dimensional fibrous mat as a photocatalyst for solar water splitting, solar hydrogen generation, or a combination thereof.

[0108] In some examples, the method comprises using the three-dimensional fibrous mat as a photocatalyst for water purification and / or water remediation. In some examples, the method comprises contacting the photocatalyst with contaminated water to form a mixture and illuminating the mixture with light that overlaps with at least a portion of the absorption band of the photocatalyst, thereby degrading at least a portion of the contamination to purify the water.

[0109] In some examples, the method comprises using the three-dimensional fibrous mat as a photocatalyst for decomposition of an organic compound, such as a complex organic pollutant, such as petroleum hydrocarbons and / or dyes.

[0110] In some examples, the method comprises using the three-dimensional fibrous mat as an advanced battery electrode.

[0111] In some examples, the method comprises using the three-dimensional fibrous mat as an antimicrobial and / or smart (e.g., self-cleaning) coating.

[0112] A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of the following claims.

[0113] The examples below are intended to further illustrate certain aspects of the systems and methods described herein, and are not intended to limit the scope of the claims.

[0114] EXAMPLES

[0115] The following examples are set forth below to illustrate the methods and results according to the disclosed subject matter. These examples are not intended to be inclusive of all aspects of the subject matter disclosed herein, but rather to illustrate representative methods and results. These examples are not intended to exclude equivalents and variations of the present invention which are apparent to one skilled in the art.

[0116] Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.) but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in °C or is at ambient temperature, and pressure is at or near atmospheric. There are numerous variations and combinations of measurement conditions, e.g., component concentrations, temperatures, pressures and other measurement ranges and conditions that can be used to optimize the described process.Example 1- 3D self-supported visible light photochemical nanocatalysts Abstract. This work focuses on 3D, self-supported, nanofibrous TiCh structures (nanogrids) prepared using blend electrospinning. The presence of anatase and brookite phases in Cu-doped TiCh nanogrids significantly enhances the photocatalytic properties of the titania system. The absorption edge in Cu-doped TiCh shifts to the visible due to the narrowed bandgap and efficient separation of photogenerated charge carriers facilitated by Cu doping. The presence of the brookite phase further contributes to the enhanced performance, by reducing electron-hole recombination. A wide range of characterization techniques, including cyclic voltammetry and chronoamperometry studies, which show that the Cu doped TiCh sample generates a significant photocurrent under visible light, are employed to elucidate the role of Cu doping in enhancing the visible light photocatalytic efficiency of TiCh nanogrids, offering valuable insights for developing advanced photochemical catalysts for environmental and energy applications. The nanogrids studied here are far superior to P25 Degussa and are activated by natural sunlight and do not require a filtration system to remove nanoparticles from the water. These self-supported nanofibrous photochemical catalysts offer all the benefits of nanomaterials while suffering from none of their drawbacks.

[0117] Introduction. Titanium dioxide (TiCh) is a widely used functional oxide with a broad range of applications including solar cells, gas sensors, photocatalysis, and self-cleaning technologies [1], As highlighted in the review on ideal photocatalysts by McKone et al., the development of solar fuel systems faces significant constraints related to the efficiency, stability, and scalability of their photocatalysts [2],

[0118] The bandgap of TiCh (~ 3.2 eV) requires excitation by ultraviolet light (below 400 nm), rendering visible light unusable to create electron-hole pairs [3], Second, the short lifetime of the photogenerated electrons and holes in TiCh nanoparticles hinders their effective utilization [4], Finally, the lack of an ideal self-supported nanostructure that can be easily recovered remains a challenge [5],

[0119] To overcome these limitations and enhance the photocatalytic properties of TiCh under visible light, numerous studies have been explored doping with various metal ions such as Ag, Fe, Pd, Pt, Zn, Mn, B, and Zr [6], Cu doping has shown promise [7]; however, it is required to reduce the optical bandgap further and to increase the surface area to volume ratio of Cu-doped titania to achieve the desirable photocatalytic activity [8], Incorporation of Cu into the lattice of TiC>2 though leads to the formation of unwanted CuO and Cu2O byproducts [9], Copper oxide systems, CU2O and CuO, are abundant, nontoxic, natural p-type semiconductors with bandgaps (-2.1 eV for Q12O and -1.2 eV for CuO) suitable for photoinduced water splitting under visiblelight

[0010] , However, these materials exhibit instability in electrolytic solutions due to their tendency to undergo photooxidation. Siripala et al. prepared a O / TiCh heterojunction by electrodeposition of copper oxide, but the combination of TiCh and CuO crystallites proved problematic due to inconsistent band bending, varying crystallite sizes, and the issue of CuO crystallite sulfidation

[0011] , Therefore, designing a system that incorporates Cu ions as intercalants or substitutions in the TiO2 lattice is important.

[0120] This work offers a viable route to obtain stable Cu-doped TiO2 nanoparticles with a high surface area-to-volume ratio by means of nanofiber-based processes.

[0121] Electrospinning is a commonly used technique for preparing long, continuous nanofibers [8b], While there are several reports on rare-earth-doped TiCh nanofiber structures in the literature

[0012] , synthesizing self-supported 3D mats of Cu-doped TiCh nanofibers is seldom reported. TiCh nanomats doped with Cu (called nanogrids) are studied here on how they alter the optical and electronic properties of the titania system.

[0122] Results and Discussion. The undoped and Cu-doped TiCh nanofibrous mats were analyzed using the XRD method to confirm their crystallinity and phase composition after the heat treatment process, as shown in Figure 1. The analysis reveals that both samples comprise anatase phase with a prominent peak of (101) plane, with almost no rutile formation

[0013] , The anatase (101) peak shifted toward a lower diffraction angle for 2 at% Cu-doped TiCh compared to pristine TiCh. The decrease of this peak is due to the presence of brookite (210) peak overlapping with the (101) of anatase due to the Cu- doping of TiCh. The notable shift in the diffracting angle and absence of any peaks for pure Cu or Cu-(I or II) oxides indicate the successful incorporation of Cu into the TiCh lattice, a crucial signature for ensuring the doping of Cu in the TiCh lattice. The presence of the metastable brookite phase alongside anatase is also confirmed by the characteristic (211), (102), (202), (221), (302), (312), (231) peaks at 30.89°, 36.28°, 40.2°, 42.33°, 46.1°, 49.2°, 57.4° and a shoulder peak of plane (111) at 25.7° originated near the anatase (101) peak

[0014] , Brookite is a desirable polymorph due to its unique electron trap depth, which prolongs electron-hole pairing and maintains high energy levels necessary for efficient photochemical reactions. This combination of phases enhances the photocatalytic properties of the material, making it suitable for advanced applications

[0015] ,

[0123] High-resolution TEM analysis was conducted on the undoped TiCh samples. Figure 2a-Figure 2b shows the high-resolution TEM image and the corresponding selected area electron diffraction (SAED) pattern of the undoped TiCh nanofibers after heat treatment. The TEM image reveals uniform crystallites of anatase phase TiCh, with no evidence of brookite or rutile phases. The SAED pattern further confirms the exclusive presence of anatase crystallites, as indicated bythe distinct diffraction rings corresponding to the anatase phase. Unlike the doped samples, as shown in Figure 3a-Figure 3c, no additional phases were observed in the undoped TiCh, suggesting that it was the introduction of Cu dopants that stabilized the brookite phase. The crystallites of the undoped TiCh are evenly distributed and maintain the anatase structure. The absence of other polymorphs in the undoped sample suggests that the observed photocatalytic behavior is solely attributed to the anatase phase, providing a baseline for comparing the effects of Cu doping on the structural and photocatalytic properties of TiCh. The high-resolution TEM and SAED analyses collectively confirm that the undoped TiCh maintains a stable and pure anatase phase.

[0124] High-resolution TEM and selected area diffraction patterns were obtained to characterize the Cu-doped samples, as shown in Figure 3a-Figure 3c. The SAED ring pattern of the doped sample matches the d-spacing observed in the high-resolution TEM image, with a d-spacing of 2.91 nm corresponding to the (2 1 1) plane of the brookite phase, validating the XRD results. Brookite crystallites are uniformly distributed across the nanofibers, in close proximity to anatase crystallites, as shown in the dark field images. This even distribution ensures that the unique properties of brookite are effectively integrated into the overall photocatalytic performance of the material.

[0125] To fully map the location of the brookite phase in the doped sample, an objective aperture was used around the ring pattern associated with the brookite phase. By doing so, an image was captured in dark field mode in the TEM, brightening the crystallites of brookite. The results, shown in Figure 4, indicate that brookite crystallites are uniformly distributed around the fiber with no preferential growth direction. Furthermore, the brookite crystallites appear larger in diameter compared to the surrounding anatase crystallites. This observation is consistent with the natural tendency of brookite to form larger crystallites (10-30 nm) compared to anatase (9-15 nm) due to its lower surface energy. The presence of brookite in this size range and distribution profile contributes to the overall increase in photocatalytic efficiency by providing additional active sites for electron-hole separation.

[0126] The heat-treated and doped TiCh mats are self-supported and can be shaped into various forms as photocatalytic mats and blankets, as shown in Figure 5a-Figure 5b. Their microstructure comprises nonwoven fibers with diameters ranging from 60-190 nm and lengths extending to several microns. This nanofibrous mat floats on water. It is a porous polycrystalline grid of interconnected grains with a texture of potato chips, as shown in Figure 5a. It is very light and robust, making these mats suitable for applications in water remediation or water splitting. The high aspect ratio of the nanofibers is crucial for efficient photocatalysis, as it increases theinterface area between light, semiconductor, and solution, thereby enhancing the interaction and efficiency of the photochemical catalytic process. The distinct yellow color of the mats, in contrast to the white color of pure TiCh (Figure 10), suggests a shift toward visible light absorption, which is indicative of successful Cu doping and its impact on the electronic properties of the material.

[0127] To map the distribution of dopants, high magnification EDX mapping and spectral analysis of both heat-treated and non-heat-treated fibers were performed. EDX spectra of Figure lla-Figure 11b indicate the complete removal of carbon from the PVP carrier polymer during heat treatment. This ensures that the final product is free from organic contaminants that could affect its photocatalytic performance. High-resolution EDX mapping across a single nanofiber in Figure 6 shows uniform distribution of Ti, O, and Cu elements, confirming successful doping at the atomic scale without forming CuO, Q12O, or other impurities. This uniform distribution is critical for maintaining the electronic and structural integrity of the nanofibers, ensuring consistent and reliable photocatalytic activity across the material.

[0128] To fully understand the oxidation states and the chemical environment of the Cu dopant in the TiCh lattice, X-ray photoelectron spectroscopy (XPS) analysis was conducted on both the doped and undoped TiCh nanofibers. Figure 7a and Figure 7e presents a wide scan survey containing peaks for Ti, Cu, O, and C of the undoped and doped samples, respectively. Also, a comprehensive analysis is performed for the oxidation states of Ti 2p, O ls, and Cu 2p lines of XPS spectra for both samples and presented in Figure 7b-Figure 7d for undoped, and Figure 7f-Figure 7h for Cu-doped samples, accordingly. The corresponding peak energies, and full width at half maxima (FWHM) are summarized in Table 1. The data was analyzed in CasaXPS software, where C is peak at 284.8 eV was used for calibrating excess charges of the states.

[0016] Table 1. XPS results on peak energies, and full-width half-maxima (FWHM) of Ti 2p, O ls, and Cu 2p lines of pure TiO2 and Cu-doped TiO2 nanofiber mats.

[0129] Samples Component Peak Energy [eV] FWHM [eV]

[0130] TiCh Ti 2p3 / 2 459.09 1.02

[0131] Ti 2pi / 2 464.71 1.87

[0132] O Is Lattice O2' 530.29 1.08

[0133] Hydroxyl 531.68 1.50

[0134] H2O 533.14 1.18

[0135] Cu-doped TiO2 4 2p3 / 2 458.34 1.19

[0136] Ti 2pi / 2 464.04 2.00

[0137] Cu 2p3 / 2 934.16 2.01

[0138] Cu 2pi / 2 953.97 2.67

[0139] O Is Lattice O2' 529.64 1.18

[0140] Hydroxyl 531.07 2.06

[0141] H2O 533.31 2.42

[0142]

[0143] The undoped TiO2 nanofibers show no Cu 2p signals as observed from Figure 7d, as expected since no copper was introduced into the system. In Figure 7b, the Ti 2p spectrum of the undoped sample reveals peaks at binding energies of 459.09 and 464.71 eV, corresponding to Ti 2p3 / 2 and Ti 2pi / 2 states, respectively. These peaks slightly shifted toward the lower binding energies at 458.34 and 464.04 eV in the Cu-doped TiO2 nanofiber mat as shown in Figure 7f. These binding energies correspond to the Ti4+oxidation state of TiCh and provide insight into the absence of Ti3+states in the materials

[0017] , Also, the presence of Cu2+state in doped TiCh mat is confirmed by the Cu 2p3 / 2 and Cu 2pi / 2 peaks at 934.16 and 953.97 eV respectively in Figure 7h, further confirming the absence of pure Cu (Cu°-state) or Q12O (Cu+state).

[0018] In addition, the shift of Ti 2p3 / 2 and Ti 2pi / 2 peaks toward lower energy can be attributed to the incorporation of Cu2+ions into the TiCh lattice. The incorporation of Cu into TiCh causes changes in the electronic environment around the Ti4+ions. The shift suggests that Cu doping introduces new electronic states and modifies the local structure, potentially creating oxygen vacancies or altering the bond lengths and angles within the TiCh lattice.

[0144] The O ls spectra of undoped TiO2 in Figure 7c contains a well-formed peak at 530.29 eV, and two shoulders at 531.68 and 533.14 eV. The binding energy around 530.29 eV corresponds to the lattice oxygen of TiO2 whereas the peak energies at 531.68 and 533.14 eV are attributed to the presence of hydroxyls and physisorbed water on the surface

[0019] , In the Cu-doped TiO2sample, the lattice oxygen peak of TiCh switches toward lower binding energy at 529.64 eV, presented in Figure 7g. A similar type of shift is also observed in Ti 2p peaks. The downward peak shifts of both Ti 2p and lattice oxygen in the Cu-doped TiCh sample further confirm that the electronic states and local structure of TiCh lattice are changing from Cu-doping.

[0145] The Cu°, Cu+oxidation states, and CuO are absent in the doped sample as confirmed from XPS and XRD spectra respectively, providing insight that Cu is only incorporated into the TiC>2 lattice as a substitution of Ti. The calculated chemical formula for pure TiCh and Cu-doped TiC>2 samples are TiOi.92 and Cu0.08Ti0.92O1.88, respectively. This suggests that the Cu2+is substituting Ti4+ions and increasing the oxygen vacancies in the doped sample.

[0146] The UV-vis analysis performed on both samples aimed to determine their bandgaps and confirm the visible light photocatalysis capability of the Cu-doped TiO2. Figure 12 shows the UV-vis spectra in reflectance-mode. Pure TiO2 fibers absorb light at wavelengths of 400 nm or less, while the Cu-doped TiO2 exhibits a broader absorption spectrum extending to 500 nm, indicating successful engineering for visible light activity. The Tauc plot in reference [5] using the Kubelka-Munk transformation reveals bandgaps of 3.1 eV for pure TiCh and 2.62 eV for Cu-doped TiC>2, confirming the enhanced visible light activity of the doped sample. This shift in bandgap is a direct result of Cu doping, which modifies the electronic structure and allows the material to utilize a broader range of the solar spectrum, thereby improving its photocatalytic efficiency under visible light.

[0147] Cyclic voltammetry (CV) was used to establish a baseline during chronoamperometry. The CV curve in 0.1 M KOH solution (Figure 13). Chronoamperometry in Figure 8a also shows no photocurrent increase under UV-filtered xenon lamp illumination, as expected due to the TiO2 bandgap of 3.2 eV. In contrast, the doped sample in Figure 8b shows clear current generation under visible light, with a maximum current of 180 nA, indicating electron-hole pair generation from visible light excitation. This demonstrates the enhanced photocatalytic activity of the doped sample under visible light, confirming the effectiveness of Cu doping in modifying the electronic properties of TiCh.

[0148] The photocatalytic activity of Cu-doped TiCh was qualitatively compared with commercial P25 TiCh. The experiment was performed using a control sample in a petri dish containing 10 mL of 50 ppm Methylene Blue (MB) as shown in Figure 9a. AUV-filtered xenon lamp was used to block wavelengths below 400 nm. The P25 sample showed minimal degradation, while the doped sample fully degraded Methylene Blue over 360 min. This qualitative analysis highlights the superior performance of the Cu-doped sample under visible light conditions, emphasizing the impact of Cu doping on the photocatalytic efficiency of TiCh.To quantitatively assess the photocatalytic performance of Cu-doped TiCh, pure TiCh, and the commercial P25 photocatalyst, a series of controlled experiments were conducted under both full-spectrum light and UV-filtered conditions. These experiments aimed to provide a comprehensive comparison of the degradation efficiency of Methylene Blue, a common dye used as a model pollutant. Each sample was tested in a petri dish containing 10 mL of 50 ppm Methylene Blue solution. The degradation of Methylene Blue was monitored over a 240-min period, with samples collected every 30 min. The collected samples were analyzed using UV-vis spectroscopy to measure the absorbance of Methylene Blue at its characteristic wavelength, allowing for the calculation of the concentration of MB remaining in the solution. Under visible light conditions (UV-filter blocked light below 400 nm), the Cu-doped TiCh nanofibers exhibited a significantly higher degradation rate of Methylene Blue compared to both pure TiCh and the commercial P25 photocatalyst. The degradation efficiency was quantified using the Cn / C ratio, where Cn represents the initial concentration of Methylene Blue and C represents the concentration at specific time intervals.

[0149] As shown in Figure 9b, the Cu-doped TiCh reduced the Methylene Blue concentration more effectively than the P25 and undoped samples, achieving a degradation efficiency of over 90% within the 240-min period. This enhanced performance can be attributed to the extended absorption range into the visible spectrum and improved charge separation provided by Cu doping. When tested under full-spectrum light, which includes both UV and visible light, the Cu-doped TiC>2 again demonstrated superior photocatalytic activity as shown in Figure 9c. Figure 9c illustrates that the degradation rate of Methylene Blue was higher for the Cu-doped sample compared to pure TiCh, and P25 photocatalyst - which is known for its high activity under UV light but limited performance under visible light. The doped sample achieved nearly complete degradation of Methylene Blue within the same time frame, highlighting the effectiveness of Cu doping in enhancing the photocatalytic properties of TiCh. To further analyze the impact of light spectrum on photocatalytic performance, a direct comparison between the degradation rates under UV-filtered and full-spectrum light was conducted, as shown in Figure 9d. The results revealed that while the P25 photocatalyst performed better under full-spectrum light due to its UV activity, it was still outperformed by the Cu-doped TiCh under both conditions. This indicates that the Cu-doped sample’s activity is primarily driven by its ability to utilize visible light, making it more effective for applications where visible light is the primary light source.

[0150] Additionally, the undoped TiCh sample, which predominantly comprises the anatase phase, showed limited degradation capability under visible light, achieving less than 20% degradation over 240 min. This was expected given the large bandgap of anatase TiCh, whichrestricts its activity to the UV range. However, under full-spectrum light, the undoped sample showed improved performance but still lagged behind both the Cu-doped TiCh and the P25 photocatalyst, as depicted in Figure 9c.

[0151] The quantitative analysis underscores the significant impact of Cu doping on the photocatalytic efficiency of TiCh. The introduction of Cu2+ions into the TiCh lattice not only narrows the bandgap, allowing for visible light absorption, but also promotes better charge separation and reduces recombination rates. This combination of factors results in a markedly improved photocatalytic performance, making Cu-doped TiCh a promising candidate for environmental remediation and solar-driven hydrogen production.

[0152] Cu-doped TiC>2 shows efficient photocatalytic activity to the degradation of methylene blue due to its improved charge separation ability credited to the presence of the brookite phase. The significant contribution of Cu-doping into TiCh is to stabilize the brookite phase, and reduce of optical bandgap from 3.2 to 2.63 eV compared to pristine TiCh. As a result, the absorption edge of the Cu-doped nanofibrous mat switches from UV to visible light of the spectrum. This allows to absorb remarkable amount of visible light by the Cu-doped nanofibrous mat and creates electron and hole pairs. Vequizo et al. reported the presence of moderate electron-trap depth, compared to anatase and rutile phases, in the brookite phase which reduces the electronhole recombination process as well as promotes both photocatalytic oxidation and reduction reactions by the material [15a], Thus, the photogenerated electrons and holes have a longer lifetime in Cu-doped TiCh nanofibrous mat and the ability to contribute to both oxidation and reduction reactions for the degradation of methylene blue. Here, the hole works as a powerful oxidizing agent that converts H2O into highly reactive hydroxyl ( OH) radicals. The ( OH) and hole reacts with methylene blue and produces CO2 and H2O. On the other hand, the negatively charged electrons oxidize the O2 and turn into superoxide ions ( O2 ). The O2 radicals take part in a chain reaction and convert into OH radicals, which degrade the methylene blue into CO2 and H2O.[6a,20]

[0153] Conclusion. In this study, Cu-doped TiO2 and pure TiO2 nanofiber mats were synthesized using a combination of sol-gel and electrospinning methods and characterized. The key achievements in this study include: 1) the creation of a self-supported nanostructure with an exceptionally high aspect ratio, enhancing both photo-absorption and photocatalytic efficiency; 2) the stabilization of the brookite phase, which reduces recombination rates and further boosts photocatalytic performance; 3) a reduction in the bandgap and broadening of light absorption, expanding the range of the photocatalyst’s activity; 4) the avoidance of common contaminantssuch as CuO and Q12O, which negatively impact photocatalytic efficiency; and 5) the demonstration of effective dye degradation under natural sunlight alone.

[0154] The introduction of Cu as a dopant was intended not only to enhance the photocatalytic properties of TiCh under visible light by narrowing its bandgap and improving charge separation efficiency but also to lead to the stabilization of a mixed-phase structure. A revolutionary observation in this work is the successful stabilization of the brookite phase, which, along with anatase, emerged as a primary structural component in the doped nanofibers. This discovery is significant as brookite is rarely seen in TiCh nanostructures and is known for its unique photocatalytic properties. The comprehensive analyses, including XRD, SEM, TEM, UV-vis spectroscopy, and XPS, provided detailed insights into the structural, morphological, and electronic modifications induced by Cu doping.

[0155] The XRD analysis confirmed that both the doped and undoped samples predominantly exhibited the anatase phase, with the doped samples showing additional presence of the brookite phase. The TEM analysis further supported these findings, highlighting the uniform distribution of brookite crystallites in the doped samples, which contributed to their enhanced photocatalytic properties. SEM and morphology analysis revealed that the electrospun nanofibers had diameters ranging from 60-190 nm, with a high aspect ratio beneficial for photocatalytic applications.

[0156] The UV-vis analysis demonstrated that Cu doping effectively shifted the absorption spectrum of TiCh into the visible light region, with the bandgap reduced from 3.1 eV (pure TiCh) to 2.62 eV (Cu-doped TiCh). This shift was crucial for enabling visible light photocatalysis. The XPS analysis confirmed the successful incorporation of Cu2+ions into the TiCh lattice, which created electronic states favorable for enhanced photocatalytic activity.

[0157] The cyclic voltammetry and chronoamperometry studies showed that the doped TiCh samples generated a significant photocurrent under visible light, indicating efficient electronhole pair generation and separation. The qualitative and quantitative analyses of Methylene Blue degradation further underscored the superior photocatalytic performance of Cu-doped TiCh. Under both UV-filtered and full-spectrum light, the Cu-doped samples achieved higher degradation efficiencies compared to pure TiCh and commercial P25 photocatalysts.

[0158] Overall, the Cu-doped TiO2 nanofibers exhibited significantly enhanced photocatalytic activity under visible light, attributed to the combined effects of bandgap narrowing, improved charge separation, and the presence of the brookite phase. These findings suggest that Cu-doped TiO2 is a promising material for photocatalytic applications, including environmental remediation and solar-driven hydrogen production. Future work will focus on optimizing thedoping levels and exploring the mechanistic aspects of photocatalysis in greater detail to further improve the efficiency and stability of these materials.

[0159] Supporting Information

[0160] Materials and Methods. Pure TiCh and Cu-doped TiCh nanofiber mats were synthesized using a combination of sol-gel and electrospinning methods (blend electrospinning). To prepare the pure TiCh precursor, a 10% poly(vinyl pyrrolidone) (PVP) (Supplier: Sigma Aldrich) solution in ethanol (with a molecular weight of 1,300,000 gm / mol) was magnetically stirred for one hour to completely dissolve the PVP as a carrier polymer in the electrospinning process. Separately, Titanium Isopropoxide (TTIP) (Supplier: Aldrich) was diluted in anhydrous ethanol inside a nitrogen glovebox to create a 30% weight per volume solution. This homogeneous precursor solution was then mixed with acetic acid to control and delay the hydrolysis step before being combined with the PVP solution. The final precursor mixture was ultrasonicated until a homogeneous, yellow-colored sol was achieved.

[0161] For the Cu-doped precursor, Copper (II) nitrate hemi(pentahydrate) (Sigma Aldrich) was dissolved in ethanol and then mixed with the TTIP solution to achieve a 2% doping level. The resultant sol solutions were immediately transferred into syringe for electrospinning. Using a 22-gauge stainless steel needle as the electrospinning nozzle, the electrospinning parameters were set to a flow rate of 1.6 ml / hour, a working distance of 15 cm, and a voltage of 18 kV. A high-voltage power supply was attached to the needle, with aluminum foil serving as the ground to generate the necessary electric field for the electrospinning process. The collected fibers were subsequently heat-treated in a tube furnace at 500°C for 4 hours to decompose PVP, and further oxidize and crystallize the TiCE and Cu-doped TiCE samples.

[0162] Characterization and Property Measurements. The crystal structure and phase composition of the samples were analyzed using a Rigaku Miniflex 6000 X-ray diffractometer, recording XRD patterns in the 29 range of 20° to 60° with Cu-Ka radiation (1 = 1.5406 A) at 40 kV and 15 mA, a step size of 0.02°, and a scan speed of 2° / min. Raw data for XRD were analyzed using MDI Jade software from CEMAS. Surface morphology and microstructure were examined with a Thermo Fisher Scientific Apreo FESEM in secondary electron (SE) mode, with samples sputter-coated with gold to prevent charging. Elemental composition was determined via energy-dispersive X-ray spectroscopy (EDS) using an ED AX detector on the FESEM setup. High-resolution transmission electron microscopy (HR-TEM) was conducted using a Tecnai 20 microscope at 200 kV, with samples prepared by dispersing material in ethanol and placing a drop onto a carbon-coated copper grid. Surface chemical composition and electronic states were analyzed using a Kratos X-ray photoelectron spectrometer (XPS), recording spectra withmonochromatic Al Ka X-rays (energy = 1486.7 eV), a pass energy of 200 eV for survey scans, and 50 eV for high-resolution scans, with charge neutralization and calibration using the C Is peak at 284.8 eV.

[0163] Optical properties were investigated using a UV-Vis spectrophotometer (HR 4000 High-Resolution Spectrometer, Ocean Optics Inc) recording spectra in the 200 to 800 nm range, with samples prepared by dispersing material in a suitable solvent and using a quartz cuvette with a 1 cm path length, performing baseline correction with the solvent as a reference. The photocatalytic activity of the samples was evaluated through the degradation of methylene blue under UV-Vis light. A methylene blue solution (10 mg / L) was prepared, and the initial concentration (Co) was measured by recording the intensity of the characteristic absorption peak at 665 nm. The photocatalyst was then added, and the solution was irradiated under UV-Vis light, with aliquots taken at 15-minute intervals. The concentration of methylene blue (C) at each time point was determined by measuring the intensity of the 665 nm absorption peak, and the degradation efficiency was calculated using the ratio C / Co.

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[0186] Example 2 - 3D nanotech blankets offer new path to clean drinking water

[0187] When titanium dioxide absorbs light, electrons are formed that oxidize water and attack pollutants, slowly destroying them until they become benign. When copper is added, the process is supercharged, making it even more effective.

[0188] To determine this, the nanomat’s updated properties were characterized to understand how it behaved and what made it different from other self-cleaning nanoparticles.

[0189] Surprisingly, it was found that compared to traditional solar cells, these nanomats can be more successful at power generation when placed under natural sunlight.

[0190] These nanomats can be used as a power generator, or as water remediation tools. In both ways, these nanomats include a catalyst with the highest efficiency reported to date. These lightweight, easy-to-remove fiber mats can float and operate atop any body of water and are even reusable through multiple cleaning cycles. Because nanomats are so effective, it is envisioned that they could be used to rid water of industrial pollutants in developing countries, turning otherwise contaminated rivers and lakes into sources of clean drinking water.

[0191] Additionally, because this technology doesn’t generate any toxic byproducts like some solar cell systems, nanomats are extremely environmentally friendly.

[0192] Example 3 - 3D nanotech blankets offer new path to clean drinking water

[0193] Fiber tech could eliminate pollutants, generate sustainable energy.Disclosed herein is a new material that, by harnessing the power of sunlight, can clear water of dangerous pollutants.

[0194] Created through a combination of soft chemistry gels and electrospinning - a technique where electrical force is applied to liquid to craft small fibers - thin fiber-like strips were constructed of titanium dioxide (TiCh), a compound often utilized in solar cells, gas sensors, and various self-cleaning technologies.

[0195] Despite being a great alternative energy source, solar fuel systems that utilize TiCh nanoparticles are often power-limited because they can only undergo photocatalysis, or create chemical reactions, by absorbing non-visible UV light. This can cause significant challenges to implementation, including low efficiency and the need for complex filtration systems.

[0196] Yet, when copper was added to the material to improve this process, the new structures, called nanomats, were able to absorb enough light energy to break down harmful pollutants in air and water.

[0197] Prior to this disclosure, there has not been an easy way to create something like a blanket that can be laid on water and start creating energy. Disclosed herein is the first demonstration of these structures and demonstration that they actually work.

[0198] When titanium dioxide absorbs light, electrons are formed that oxidize water and attack pollutants, slowly destroying them until they become benign. When copper is added, the process is supercharged, making it even more effective.

[0199] To determine this, researchers worked to characterize the nanomat’s updated properties to understand how it behaved and what made it different from other self-cleaning nanoparticles. Surprisingly, it was found that, compared to traditional solar cells, these nanomats can be more successful at power generation when placed under natural sunlight.

[0200] These nanomats can be used as a power generator, or as water remediation tools. In both ways, the nanomats include a catalyst with the highest efficiency reported to date.

[0201] These lightweight, easy-to-remove fiber mats can float and operate atop any body of water and are even reusable through multiple cleaning cycles. Because nanomats are so effective, it is envisioned that they could be used to rid water of industrial pollutants in developing countries, turning otherwise contaminated rivers and lakes into sources of clean drinking water.

[0202] Additionally, because this technology doesn’t generate any toxic byproducts, like some solar cell systems do, the nanomats are extremely environmentally friendly. The nanomats are a safe material, don’t hurt anything, and are as clean as it can be.The technology is incredibly efficient. The tools exist to make the nanomats in large quantities and translate them to various industries.

[0203] The findings suggest that the nanomats could be a promising tool in many future photocatalytic applications, including long-term sustainability efforts like environmental remediation as well as solar-driven hydrogen production.

[0204] Further optimization of the material is being investigated.

[0205] Example 4 - Revolutionary 3D Nanotech Blankets pave the way for sustainable clean drinking water solutions

[0206] In a groundbreaking advancement that intertwines nanotechnology and environmental science, disclosed herein is an innovative material capable of purifying water by harnessing the power of sunlight. This approach presents a promising solution to mitigating various pollutants in water bodies, leveraging the unique properties of titanium dioxide (TiCh) in an unprecedented manner. The implications of this development are vast, particularly in areas grappling with water quality issues arising from industrial contamination.

[0207] A significant challenge in utilizing titanium dioxide as a photocatalyst is its traditional reliance on non-visible ultraviolet (UV) light for chemical reactions. While effective in theory, this limitation hampers the efficiency of solar fuel systems and necessitates complex filtration methods. Researchers encountered these challenges head-on by implementing an innovative methodology that combines soft chemistry gels with electrospinning. This technique applies an electrical force to liquid to crease extremely thin, fiber-like structures known as nanomats, which are imbued with titanium dioxide.

[0208] The introduction of copper into the nanomats enhances their ability to absorb light energy, significantly improving the degradation of harmful pollutants. This advancement represents a pivotal shift in photocatalytic processes, as it enables the nanomats to function effectively under natural sunlight conditions. The successful synthesis of these materials is a demonstration of their untapped potential as both energy -generating systems and water remediation tools.

[0209] The mechanics of how these nanomats operate are rooted in the photocatalytic properties of titanium dioxide. Upon exposure to light, the material produces electrons that facilitate the oxidation of water molecules, leading to the breakdown of contaminants into benign byproducts. By incorporating copper into the structure, a method was found to supercharge this reaction, boosting the materials’ overall efficiency. This synergy between titanium dioxide and copper creates an effective catalyst - one that could revolutionize both environmental cleanup and renewable energy production.In comparison to conventional solar cells, which primarily rely on UV light, these nanomats exhibit superior power generation capabilities when exposed to natural sunlight. This not only opens avenues for enhancing the efficiency of solar technologies but also provides a dual-functionality that could be instrumental in addressing water scarcity and pollution. Their ability to float on water surfaces, coupled with their lightweight and reusable characteristics, positions them as a practical and sustainable solution for treating polluted water bodies.

[0210] The broader implications of this technology are particularly compelling for developing countries, where access to clean water remains a pressing challenge. By deploying these nanomats in contaminated rivers and lakes, a future is envisioned where polluted water can be transformed into a source of safe drinking water. The environmentally friendly nature of the material, which produces no toxic byproducts, adds another layer of desirability to its potential applications.

[0211] Moreover, the significance of this research extends beyond immediate environmental benefits. The study serves as a paradigm shift towards sustainable manufacturing practices as well. The material can be produced in large quantities, making it feasible for industrial applications once there is substantive interest from relevant industries. The crystal-clear clarity of the material, with its self-supporting structure, facilitates both regular cleaning cycles and ease of deployment, enhancing its practicality for real-world applications.

[0212] The research has already demonstrated impressive proof-of-concept results. The timeline for commercial scalability will hinge on industry engagement. The tools for large-scale fabrication are available; effective outreach and partnership with industries that could benefit from this technology can transition this material from laboratory settings to practical use in environmental cleanup and renewable energy sectors.

[0213] Researchers are also committed to further exploring the material’s parameters to optimize performance and explore additional functionalities. This commitment to innovation ensures that the study does not merely represent a peak achievement but rather the beginning of a broader exploration into nanotechnology’s roles in sustainable environmental initiatives. The teams’ excitement about these developments is palpable, reaffirming their commitment to advancing the field of photocatalysis.

[0214] In conclusion, the development of these nanomats represents a significant breakthrough in utilizing sunlight for environmental remediation and energy generation. This innovative technology stands poised to improve water quality in polluted ecosystems while offering a clean, renewable energy source. As research continues and more attention is drawn to this intersectionof nanotechnology and environmental science, the benefits could extend far beyond the realms of academic research, influencing industries and communities worldwide.

[0215] EXEMPLARY ASPECTS

[0216] In view of the described compositions, devices, systems, and methods, herein below are described certain more particularly described aspects of the inventions. The particularly recited aspects should not, however, be interpreted to have any limiting effect on any different claims containing different or more general teachings described herein or that the “particular” aspects are somehow limited in some way other than the inherent meanings of the language and formulas literally used therein.

[0217] Example 1: A three-dimensional fibrous mat comprising a plurality of fibers, each of the fibers comprising Cu-doped TiCh.

[0218] Example 2: The three-dimensional fibrous mat of any example herein, particularly example 1, wherein the Cu dopant is present in an amount of from greater than 0 to 10%, for example 2%.

[0219] Example 3 : The three-dimensional fibrous mat of any example herein, particularly example 1 or example 2, wherein the plurality of fibers are substantially free of copper oxides (e.g., CuO, Cu2O, or a combination thereof).

[0220] Example 4: The three-dimensional fibrous mat of any example herein, particularly examples 1-3, wherein the plurality of fibers are substantially free of impurities and / or organic contaminants.

[0221] Example 5: The three-dimensional fibrous mat of any example herein, particularly examples 1-4, wherein the distribution of Ti, O, and Cu elements is substantially uniform throughout the plurality of fibers (e.g., throughout each of the fibers).

[0222] Example 6: The three-dimensional fibrous mat of any example herein, particularly examples 1-5, wherein each of the fibers comprises a plurality of crystallites.

[0223] Example 7: The three-dimensional fibrous mat of any example herein, particularly examples 1-6, wherein each of the fibers comprises a first plurality of crystallites and a second plurality of crystallites, the first plurality of crystallites being anatase and the second plurality of crystallites being brookite.

[0224] Example 8: The three-dimensional fibrous mat of any example herein, particularly example 7, wherein the first plurality of crystallites and the second plurality of crystallites as each substantially uniformly distributed within each of the fibers.Example 9: The three-dimensional fibrous mat of any example herein, particularly example 7 or example 8, wherein the anatase crystallites have an average crystallite size of from 5 to 30 nm, such as from 5 to 15 nm, such as from 9 to 15 nm.

[0225] Example 10: The three-dimensional fibrous mat of any example herein, particularly examples 7-9, wherein the brookite crystallites have an average crystallite size of from 5 to 30 nm, such as from 10 to 30 nm.

[0226] Example 11 : The three-dimensional fibrous mat of any example herein, particularly examples 7-10, wherein the plurality of fibers have an average diameter of from 30 to 500 nanometers, such as from 60 to 190 nm.

[0227] Example 12: The three-dimensional fibrous mat of any example herein, particularly examples 1-11, wherein the plurality of fibers have an average length of from 10 nanometers to 10 meters, such as from 100 nanometers to 100 micrometers, such as from 100 nanometers to 10 micrometers.

[0228] Example 13: The three-dimensional fibrous mat of any example herein, particularly examples 1-12, wherein the plurality of fibers have an average aspect ratio (e.g., average length divided by average outer diameter) of greater than 1.

[0229] Example 14: The three-dimensional fibrous mat of any example herein, particularly examples 1-13, wherein the plurality of fibers have a high average aspect ratio (e.g., an aspect ratio of 100 or more).

[0230] Example 15: The three-dimensional fibrous mat of any example herein, particularly examples 1-14, wherein the three-dimensional fibrous mat floats on water.

[0231] Example 16: The three-dimensional fibrous mat of any example herein, particularly examples 1-15, wherein the three-dimensional fibrous mat has an absorption band that overlaps with at least a portion of the solar spectrum.

[0232] Example 17: The three-dimensional fibrous mat of any example herein, particularly examples 1-16, wherein the three-dimensional fibrous mat has an absorption band that overlaps with at least a portion of the visible light portion of the electromagnetic spectrum, such as at least a portion of the visible light portion of the solar spectrum.

[0233] Example 18: The three-dimensional fibrous mat of any example herein, particularly examples 1-17, wherein photogenerated electrons and holes have a longer lifetime in the plurality of fibers relative to those in a plurality of fibers without Cu-doping.

[0234] Example 19: The three-dimensional fibrous mat of any example herein, particularly examples 1-18, wherein the three-dimensional fibrous mat is non-woven.Example 20: The three-dimensional fibrous mat of any example herein, particularly examples 1-19, wherein the three-dimensional fibrous mat is self-supported.

[0235] Example 21: The three-dimensional fibrous mat of any example herein, particularly examples 1-20, wherein the three-dimensional fibrous mat is electrospun.

[0236] Example 22: A method of making the three-dimensional fibrous mat of any example herein, particularly examples 1-21.

[0237] Example 23 : The method of any example herein, particularly example 22, wherein the method comprises electrospinning, such as blend electrospinning.

[0238] Example 24: The method of any example herein, particularly example 22 or example 23, wherein the method comprises high-throughput electrospinning.

[0239] Example 25: The method of any example herein, particularly example 23 or example 24, wherein the method further comprises heat treating.

[0240] Example 26: The method of any example herein, particularly examples 22-25, wherein the method comprises preparing a Cu-doped TiCh precursor solution, electrospinning the Cu-doped TiC>2 precursor solution to form a precursor three-dimensional fibrous mat comprising a plurality of precursor fibers, and heat treating the plurality of precursor fibers to form the three-dimensional fibrous mat comprising the plurality of Cu-doped TiCh fibers.

[0241] Example 27: A method of use of the three-dimensional fibrous mat of any example herein, particularly examples 1-21.

[0242] Example 28: The method of any example herein, particularly example 27, wherein the method comprises using the three-dimensional fibrous mat as a photocatalyst.

[0243] Example 29: The method of any example herein, particularly example 28, wherein the method comprises using the three-dimensional fibrous mat as a photocatalyst for photocatalytic fuel generation.

[0244] Example 30: The method of any example herein, particularly example 29, wherein the method comprises contacting the photocatalyst with a fuel precursor to form a mixture and illuminating the mixture with light that overlaps with at least a portion of the absorption band of the photocatalyst, thereby converting the fuel precursor to a fuel.

[0245] Example 31: The method of any example herein, particularly example 30, wherein the fuel precursor comprises water.

[0246] Example 32: The method of any example herein, particularly example 30 or example 31, wherein the light is provided by a light source, such as an artificial light source or a natural light source.Example 33: The method of any example herein, particularly examples 30-32, wherein the light comprises sunlight.

[0247] Example 34: The method of any example herein, particularly examples 30-33, wherein the fuel comprises hydrogen and the method comprises using the three-dimensional fibrous mat as a photocatalyst for photocatalytic hydrogen generation.

[0248] Example 35: The method of any example herein, particularly examples 30-34, wherein the fuel precursor comprises water, the fuel comprises hydrogen, and the method comprises using the three-dimensional fibrous mat as a photocatalyst for photocatalytic water splitting for hydrogen generation.

[0249] Example 36: The method of any example herein, particularly examples 28-35, wherein the method comprises using the three-dimensional fibrous mat as a photocatalyst for water splitting, hydrogen generation, or a combination thereof.

[0250] Example 37: The method of any example herein, particularly examples 28-36, wherein the method comprises using the three-dimensional fibrous mat as a photocatalyst for solar water splitting, solar hydrogen generation, or a combination thereof.

[0251] Example 38: The method of any example herein, particularly examples 28-37, wherein the method comprises using the three-dimensional fibrous mat as a photocatalyst for water purification and / or water remediation.

[0252] Example 39: The method of any example herein, particularly example 38, wherein the method comprises contacting the photocatalyst with contaminated water to form a mixture and illuminating the mixture with light that overlaps with at least a portion of the absorption band of the photocatalyst, thereby degrading at least a portion of the contamination to purify the water.

[0253] Example 40: The method of any example herein, particularly examples 28-39, wherein the method comprises using the three-dimensional fibrous mat as a photocatalyst for decomposition of an organic compound, such as a complex organic pollutant, such as petroleum hydrocarbons and / or dyes.

[0254] Example 41: The method of any example herein, particularly examples 28-40, wherein the method comprises using the three-dimensional fibrous mat as an advanced battery electrode.

[0255] Example 42: The method of any example herein, particularly examples 28-41, wherein the method comprises using the three-dimensional fibrous mat as an antimicrobial and / or smart (e.g., self-cleaning) coating.

[0256] Other advantages which are obvious and which are inherent to the invention will be evident to one skilled in the art. It will be understood that certain features and sub-combinationsare of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of the claims. Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

[0257] The compositions, systems, and methods of the appended claims are not limited in scope by the specific compositions, system, and methods described herein, which are intended as illustrations of a few aspects of the claims and any methods that are functionally equivalent are intended to fall within the scope of the claims. Various modifications of the compositions, systems, and methods in addition to those shown and described herein are intended to fall within the scope of the appended claims. Further, while only certain representative composition elements, system elements, and method steps disclosed herein are specifically described, other combinations of the composition elements, system elements, and method steps also are intended to fall within the scope of the appended claims, even if not specifically recited. Thus, a combination of steps, elements, components, or constituents may be explicitly mentioned herein or less, however, other combinations of steps, elements, components, and constituents are included, even though not explicitly stated.

Claims

CLAIMSWhat is claimed:

1. A three-dimensional fibrous mat comprising a plurality of fibers, each of the fibers comprising Cu-doped TiCh.

2. The three-dimensional fibrous mat of claim 1, wherein the Cu dopant is present in an amount of from greater than 0 to 10%, for example 2%.

3. The three-dimensional fibrous mat of claim 1 or claim 2, wherein the plurality of fibers are substantially free of copper oxides (e.g., CuO, Q12O, or a combination thereof).

4. The three-dimensional fibrous mat of any one of claims 1-3, wherein the plurality of fibers are substantially free of impurities and / or organic contaminants.

5. The three-dimensional fibrous mat of any one of claims 1-4, wherein the distribution of Ti, O, and Cu elements is substantially uniform throughout the plurality of fibers (e.g., throughout each of the fibers).

6. The three-dimensional fibrous mat of any one of claims 1-5, wherein each of the fibers comprises a plurality of crystallites.

7. The three-dimensional fibrous mat of any one of claims 1-6, wherein each of the fibers comprises a first plurality of crystallites and a second plurality of crystallites, the first plurality of crystallites being anatase and the second plurality of crystallites being brookite.

8. The three-dimensional fibrous mat of claim 7, wherein the first plurality of crystallites and the second plurality of crystallites as each substantially uniformly distributed within each of the fibers.

9. The three-dimensional fibrous mat of claim 7 or claim 8, wherein the anatase crystallites have an average crystallite size of from 5 to 30 nm, such as from 5 to 15 nm, such as from 9 to 15 nm.

10. The three-dimensional fibrous mat of any one of claims 7-9, wherein the brookite crystallites have an average crystallite size of from 5 to 30 nm, such as from 10 to 30 nm.

11. The three-dimensional fibrous mat of any one of claims 7-10, wherein the plurality of fibers have an average diameter of from 30 to 500 nanometers, such as from 60 to 190 nm.

12. The three-dimensional fibrous mat of any one of claims 1-11, wherein the plurality of fibers have an average length of 10 nanometers to 10 meters, such as from 100 nanometers to 100 micrometers, such as from 100 nanometers to 10 micrometers.

13. The three-dimensional fibrous mat of any one of claims 1-12, wherein the plurality of fibers have an average aspect ratio (e.g., average length divided by average outer diameter) of greater than 1.

14. The three-dimensional fibrous mat of any one of claims 1-13, wherein the plurality of fibers have a high average aspect ratio (e.g., an aspect ratio of 100 or more).

15. The three-dimensional fibrous mat of any one of claims 1-14, wherein the three-dimensional fibrous mat floats on water.

16. The three-dimensional fibrous mat of any one of claims 1-15, wherein the three-dimensional fibrous mat has an absorption band that overlaps with at least a portion of the solar spectrum.

17. The three-dimensional fibrous mat of any one of claims 1-16, wherein the three-dimensional fibrous mat has an absorption band that overlaps with at least a portion of the visible light portion of the electromagnetic spectrum, such as at least a portion of the visible light portion of the solar spectrum.

18. The three-dimensional fibrous mat of any one of claims 1-17, wherein photogenerated electrons and holes have a longer lifetime in the plurality of fibers relative to those in a plurality of fibers without Cu-doping.

19. The three-dimensional fibrous mat of any one of claims 1-18, wherein the three-dimensional fibrous mat is non-woven.

20. The three-dimensional fibrous mat of any one of claims 1-19, wherein the three-dimensional fibrous mat is self-supported.

21. The three-dimensional fibrous mat of any one of claims 1-20, wherein the three-dimensional fibrous mat is electrospun.

22. A method of making the three-dimensional fibrous mat of any one of claims 1-21.

23. The method of claim 22, wherein the method comprises electrospinning, such as blend electrospinning.

24. The method of claim 22 or claim 23, wherein the method comprises high-throughput electrospinning.

25. The method of claim 23 or claim 24, wherein the method further comprises heat treating.

26. The method of any one of claims 22-25, wherein the method comprises preparing a Cu-doped TiC>2 precursor solution, electrospinning the Cu-doped TiCh precursor solution to form a precursor three-dimensional fibrous mat comprising a plurality of precursor fibers, and heat treating the plurality of precursor fibers to form the three-dimensional fibrous mat comprising the plurality of Cu-doped TiCh fibers.

27. A method of use of the three-dimensional fibrous mat of any one of claims 1-21.

28. The method of claim 27, wherein the method comprises using the three-dimensional fibrous mat as a photocatalyst.

29. The method of claim 28, wherein the method comprises using the three-dimensional fibrous mat as a photocatalyst for photocatalytic fuel generation.

30. The method of claim 29, wherein the method comprises contacting the photocatalyst with a fuel precursor to form a mixture and illuminating the mixture with light that overlaps with at least a portion of the absorption band of the photocatalyst, thereby converting the fuel precursor to a fuel.

31. The method of claim 30, wherein the fuel precursor comprises water.

32. The method of claim 30 or claim 31, wherein the light is provided by a light source, such as an artificial light source or a natural light source.

33. The method of any one of claims 30-32, wherein the light comprises sunlight.

34. The method of any one of claims 30-33, wherein the fuel comprises hydrogen and the method comprises using the three-dimensional fibrous mat as a photocatalyst for photocatalytic hydrogen generation.

35. The method of any one of claims 30-34, wherein the fuel precursor comprises water, the fuel comprises hydrogen, and the method comprises using the three-dimensional fibrous mat as a photocatalyst for photocatalytic water splitting for hydrogen generation.

36. The method of any one of claims 28-35, wherein the method comprises using the three-dimensional fibrous mat as a photocatalyst for water splitting, hydrogen generation, or a combination thereof.

37. The method of any one of claims 28-36, wherein the method comprises using the three-dimensional fibrous mat as a photocatalyst for solar water splitting, solar hydrogen generation, or a combination thereof.

38. The method of any one of claims 28-37, wherein the method comprises using the three-dimensional fibrous mat as a photocatalyst for water purification and / or water remediation.

39. The method of claim 38, wherein the method comprises contacting the photocatalyst with contaminated water to form a mixture and illuminating the mixture with light that overlaps with at least a portion of the absorption band of the photocatalyst, thereby degrading at least a portion of the contamination to purify the water.

40. The method of any one of claims 28-39, wherein the method comprises using the three-dimensional fibrous mat as a photocatalyst for decomposition of an organic compound, such as a complex organic pollutant, such as petroleum hydrocarbons and / or dyes.

41. The method of any one of claims 28-40, wherein the method comprises using the three-dimensional fibrous mat as an advanced battery electrode.

42. The method of any one of claims 28-41, wherein the method comprises using the three-dimensional fibrous mat as an antimicrobial and / or smart (e.g., self-cleaning) coating.

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