Nanoparticle ligands for polar host environment

Abstract

In one embodiment, a quantum dot is provided, the quantum dot comprising at least one inorganic material selected from the group consisting of CuFeSe2, CuFeS2, CuInZnS2, CuZnSnSe2, CuInS2, CuInSe2, CuInSexS2-x, CuInGaSexS2-x, AgInS2. AgInSe2, AgInGaSe2S2-x, CuAlS2, CuAlSe2, CuAlGaSexS2-x, CdS, CdSe, ZnS, and ZnSe, the quantum dot comprising at least one inorganic material selected from the group consisting of: CuFeSe2, CuFeS2, CuInZnS2, CuZnSnSe2, CuInS2, CuInSe2, CuInSexS2-x, CuInSe2, CuInSe2, CuInGaSexS2-x, CuInSe2, and at least one capping ligand species on the surface of the quantum dot, whereby the quantum dot is characterized by solubility in a polar host environment. Each of the capping ligand species comprises a mercapto group. The quantum dots are further characterized by exhibiting photoluminescence upon excitation with a light source, and the quantum dots exhibit a quantum yield greater than 30%. Compositions comprising quantum dots and a polar host environment are also provided.

Description

Technical Field

[0001] Various embodiments relate to nanoparticle formulations wherein the nanoparticles include ligands that cap the nanoparticles to render them soluble in many polar materials, whether polar solvents or polar polymers. In various embodiments, including some cases where the pH ranges from about 6 to 11 or higher, these formulations can maintain high quantum yields exceeding 70%. Such nanoparticles can be photoluminescent nanoparticle materials, such as quantum dots. Background Art

[0002] Colloidal semiconductor nanoparticles, commonly referred to as quantum dots (QDs), offer a variety of size-tunable optical properties, including photoluminescence (PL), and can be processed inexpensively from liquids. In particular, such QDs can very efficiently absorb a wide spectrum of light and then convert or re-emit monochromatic light determined by the size of the QD. The optical properties of these materials (such as, for example, absorption and emission spectra, PL lifetime and Stokes shift) can be controlled or customized by manufacturing conditions to obtain different sizes, shapes, compositions and / or heterostructures. This fundamental property of QDs has stimulated the research and development of fluorescent biomarkers, color-specific light-emitting diodes and displays containing vibrational quantum dots. Many non-toxic QDs are now being developed as active ingredients in luminescent composites for various applications (including, for example, lighting, solar cells, security, anti-counterfeiting inks and agriculture). However, it is generally found that photoluminescent materials or quantum dots comprising long insulating carbon chain end-capping ligands (such as, oleic acid, stearic acid, etc.) are insoluble or mostly insoluble in polar solvents. Summary of the Invention

[0003] In one aspect, quantum dots are provided. In exemplary embodiments, the quantum dots have at least one pair of selected capping ligands on the surface of the quantum dots, whereby the quantum dots are characterized by solubility in polar solvents. The quantum dots are further characterized by exhibiting photoluminescence when excited by a light source, with a quantum yield greater than 30%.

[0004] In another aspect, quantum dots are provided. In exemplary embodiments, the quantum dots have capping ligands on their surface, whereby the quantum dots are characterized by solubility in polar solvents. The quantum dots are further characterized by exhibiting photoluminescence when excited by a light source, with a quantum yield greater than 30%.

[0005] In another aspect, a composition is provided. In an exemplary embodiment, the composition includes a polar solvent and quantum dots having at least one pair of selected capping ligands on a surface of the quantum dots such that the quantum dots are soluble in the polar solvent. The composition is further characterized in that the quantum dots exhibit photoluminescence when excited by a light source, such that the quantum dots exhibit a quantum yield greater than 30%.

[0006] In yet another aspect, a composition is provided. In an exemplary embodiment, the composition includes a polar polymeric material and quantum dots, the quantum dots having one or more selected capping ligands on their surfaces. The polar polymeric material encompasses the quantum dots, whereby the composition is characterized in that the quantum dots are dispersed in the polar polymeric material. The composition is further characterized in that the quantum dots exhibit photoluminescence when excited by a light source, such that the quantum dots exhibit a quantum yield greater than 1%.

[0007] In exemplary embodiments, such a composition is provided as an extruded product having a quantum yield greater than 1% and an improved lifetime compared to quantum dots without one or more selected capping ligands on the quantum dot surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 Schematic diagrams of quantum dots including capping ligands according to exemplary embodiments are provided.

[0009] Figure 2 A diagram illustrating an exemplary composition including quantum dots and a polar solvent according to an exemplary embodiment.

[0010] Figure 3 Graph showing the quantum yield of visible-emitting CuInS2 / ZnS quantum dots in ethanol / water mixtures at different pH according to various embodiments, the quantum dots including a 1:1 mixture of mercaptoethanol and mercaptohexanol as capping ligands.

[0011] Figure 4 Graphs showing the absorption and photoluminescence spectra of visible-emitting CuInS2 / ZnS quantum dots in toluene before addition of capping ligands and then in an ethanol / water mixture after blending with a 1:1 mixture of mercaptoethanol and mercaptohexanol as capping ligands according to an exemplary embodiment.

[0012] Figure 5 Shown are photoluminescence spectra of visible-emitting CuInS2 / ZnS quantum dots in ethanol / water mixtures at different pH conditions according to an exemplary embodiment.

[0013] Figure 6 A photograph showing visible emission CuInS2 / ZnS quantum dots in dimethyl sulfoxide according to an exemplary embodiment is shown. The quantum dots include a 1:1 mixture of mercaptoethanol and mercaptohexanol as capping ligands.

[0014] Figure 7Graphs of photoluminescence intensity versus irradiation time are shown according to exemplary embodiments, showing, as a comparison, the expected lifetime (in years) of (a) native ligand-capped CuInS2 / ZnS quantum dots and (b) mercaptohexanol (MCH) as the capping ligand for H171B EVOH (38 mol% Ethylene Vinyl-Alcohol Copolymer).

[0015] Figure 8 A graph of photoluminescence intensity versus irradiation time is shown, showing the expected lifetime (in years) of CuInS2 / ZnS quantum dots with various end-capped ligands extruded in a polymer matrix of F171B EVOH (32 mol% ethylene vinyl alcohol copolymer) according to various embodiments and natural ligand CuInS2 / ZnS quantum dots as a standard as a comparison.

[0016] Figure 9 A graph of photoluminescence intensity versus irradiation time is shown, showing, as a comparison, the expected lifetime (in years) of CuInS2 / ZnS quantum dots comprising a mixture of various end-capping ligands extruded in a polymer matrix of F171B EVOH (32 mol% ethylene vinyl alcohol copolymer) according to various embodiments and native ligand CuInS2 / ZnS quantum dots as a standard.

[0017] Figure 10 Flowcharts are provided illustrating various processes, procedures, and / or operations for forming compositions comprising quantum dots having capping ligands according to various embodiments. DETAILED DESCRIPTION

[0018] The following definitions of terms and abbreviations are provided to better describe the present disclosure and to guide one of ordinary skill in the art in practicing the systems, methods, and compositions disclosed herein.

[0019] As used herein, "comprising" means "including," and the singular forms "a," "an," or "the" include plural referents unless the context clearly dictates otherwise. Unless the context clearly dictates otherwise, the term "or" is open-ended and thus refers to both individual elements of the stated alternative elements and combinations of two or more of those elements.

[0020] Unless otherwise explained, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this disclosure relates. Suitable methods and compositions are described herein for implementing or testing the systems, methods, and compositions described herein. However, it should be understood that other methods and materials similar or equivalent to the methods and materials described herein can be used to implement or test these systems, methods, and compositions disclosed herein. Therefore, the systems, methods, compositions, and examples disclosed herein are merely illustrative and not intended to be limiting. Other features of this disclosure will be clear to those skilled in the art based on the following detailed description and the appended claims.

[0021] Unless otherwise indicated, all numbers used in the specification or claims to represent the amount of ingredients, percentages, temperatures, times, etc. should be understood to be modified by the word "about". Unless otherwise indicated, non-numerical properties such as colloid, continuous, crystalline, etc. used in the specification or claims should be understood to be modified by the word "substantially", meaning to a large extent or to a considerable extent. Therefore, unless otherwise implicitly or explicitly indicated, the numerical parameters and / or non-numerical properties set forth herein are approximate values, and the optimal values of these properties and parameters may depend on the desired properties sought, the detection limits under standard test conditions or methods, the limitations of the processing method, and / or the nature of the properties or parameters. When directly and clearly distinguishing an embodiment from the disclosed prior art, the embodiment numbers are not approximate values unless the word "about" is cited. I. Definition

[0022] Carcinogen: A material that has been shown to cause cancer, directly or indirectly, in any mammal.

[0023] Colloidal Suspension: A mixture consisting of a dispersed phase (suspended particles) and a continuous phase (the liquid medium of the suspension) in which the mixture does not settle or takes an inordinately long time to settle appreciably.

[0024] Dispersibility: The ability of QDs to form colloidal suspensions.

[0025] Emission spectrum: Those portions of the electromagnetic spectrum in which the QDs (or compositions containing them) exhibit PL (in response to excitation by a light source), the amplitude of the PL being at least 1% of the peak PL emission.

[0026] Flocculation: The process by which the dispersed phase in a colloidal suspension forms aggregates and comes out of suspension.

[0027] Nanoparticle: A nanoscale particle of a solid material. The nanoparticles disclosed herein are preferably crystalline and have a dimension less than 500 nanometers. The nanoparticles disclosed herein can form a colloidal suspension. Embodiments of the disclosed nanoparticles can be a single material, or can include an inner core and an outer shell of different materials. The nanoparticles can further include a plurality of ligands bonded to the outer surface of the nanoparticle. Exemplary nanoparticles that can be used in the compositions, systems and methods described herein can include metals, metal oxides, chalcogenides, semiconductors and insulators. The nanoparticles can be crystalline (i.e., nanocrystals), amorphous, or mixtures thereof.

[0028] Photoluminescence (PL): The emission of light (electromagnetic radiation, in the form of photons) following absorption of light. It is a form of luminescence (light emission) and is initiated by light excitation (photon excitation).

[0029] Polar solvents: A polar solvent is any solvent that contains an electric dipole. Exemplary polar solvents include acetone, ethanol, water, ethanol / water mixtures, isopropyl alcohol, isopropyl alcohol / water mixtures, methanol, methanol / water mixtures, dimethyl sulfoxide, diethyl sulfoxide, tetrahydrofuran, and tetrahydrofuran / water mixtures.

[0030] Polymer (and polar polymer): A large or macromolecule composed of many repeating subunits. Polymers range from familiar synthetic plastics such as polystyrene or poly(methyl methacrylate) (PMMA) to natural biopolymers such as DNA and proteins, which are the basis of biological structure and function. Both natural and synthetic polymers are produced by the polymerization of many smaller molecules (e.g., monomers). Exemplary polymers include poly(methyl methacrylate) (PMMA), polystyrene, silicone, epoxy resins, etc.

[0031] Polar polymers: Polymers containing only carbon and hydrogen atoms are non-polar polymers. Polar polymers often contain other atoms, such as chlorine, fluorine, oxygen, nitrogen, and sulfur, which result in the polymer having a permanent electric dipole and are referred to as polar polymers. Exemplary polar polymers include polyvinyl alcohol, ethylene vinyl alcohol copolymers, polyvinyl acetate, polyurethane, ethylene vinyl acetate, acrylic polymers, polyvinyl butyral, and polyamides (e.g., nylon).

[0032] Quantum dot: A nanoparticle that exhibits size-dependent electronic and optical properties due to quantum confinement. The quantum dots disclosed herein preferably have at least one dimension less than about 50 nanometers. The disclosed quantum dots can be colloidal quantum dots. Some quantum dots that can be used in the compositions, systems and methods described herein are made of binary semiconductor materials having the formula MX, where M is a metal and X is typically selected from sulfur, selenium, tellurium, nitrogen, phosphorus, arsenic, antimony, or mixtures thereof. Exemplary binary quantum dots that can be used in the compositions, systems and methods described herein include CdS, CdSe, CdTe, PbS, PbSe, PbTe, ZnS, ZnSe, ZnTe, InP, InAs, Cu2S, and In2S3. Other quantum dots that can be used in the compositions, systems and methods described herein are ternary, quaternary and / or alloyed quantum dots including, but not limited to, ZnSSe, ZnSeTe, ZnSTe, CdSSe, CdSeTe, CdSTe, HgSSe, HgSeTe, HgSTe, ZnCdS, ZnCdSe, ZnCdTe, ZnHgS, ZnHgSe, ZnHgTe, CdHgS, CdHgSe, CdHgTe, ZnCdSSe, ZnCdSeTe, ZnCdSTe, ZnHgSeTe, ZnHgSSe, ZnHgSTe, CdHgSSe, CdHgSeTe, CdHgSTe, CuAlS2, CuAlSe2, CuAlGaSe x S 2-x (0≤x≤2), CuAlSe x S 2-x (0≤x≤2), CuAlTe2, CuFeS2, CuFeSe2, CuFeTe2, CuInS2, CuInSe2, CuInTe2, CuInGaSe2, CuInGaS2, CuInGaTe2, CuInZnS2, CuZnSnSe2, CuZnSe x S 2-x (0≤x≤2), CuInSe x S 2-x (0≤x≤2), CuInGaSe x S 2-x (0≤x≤2), CuInZnSe x S 2-x (0≤x≤2),AgInS2,AgInSe2,AgInGaSe x S 2-x (0≤x≤2) and AgInSe x S 2-x(0≤x≤2) quantum dots, although non-toxic quantum dots are preferably used. For example, in various embodiments, the quantum dots include ternary, quaternary and / or alloyed quantum dots, including but not limited to various combinations of Cu, Fe, In, Ga, Ag and / or Al with various combinations of Se, S and / or Te. Non-toxic quantum dots include those that do not contain, for example, cadmium, lead and mercury. The disclosed embodiments of the quantum dots can be a single material, or can include a core and a shell of different materials. The shell can be a thin shell or layer formed by any suitable method (e.g., cation exchange). The quantum dot further includes a plurality of ligands bonded to the surface of the quantum dot.

[0033] Ligand: A ligand is an ion or molecule that bonds to another, typically larger, molecule. Typically, ligands bond to metal atoms, which in the case of the present disclosure are part of a quantum dot and / or nanoparticle. Ligands can be configured to bond to specific receptors, interact with various types of substances in prescribed ways, and so on. Capping ligands are configured to stabilize the interface where a nanoparticle (e.g., a quantum dot) interacts with its surrounding medium.

[0034] Solubility: When used for QDs, the ability of the QDs to form a clear colloidal suspension without turbidity due to aggregate formation.

[0035] Toxic: A material that can harm living organisms due to the presence of phosphorus or heavy metals such as cadmium, lead or mercury. II. General Overview

[0036] The present disclosure relates to capping ligands for nanoparticles, such as quantum dots, wherein the capping ligands allow the nanoparticles to dissolve in many polar materials, whether polar solvents or polar polymers.

[0037] Various embodiments provide quantum dots that are soluble in polar solvents or polar polymers. Various embodiments provide compositions comprising quantum dots in polar solvents. Various embodiments provide quantum dots embedded in extrudates formed from polar polymers.

[0038] Nanoparticle quantum dots of group I-III-VI semiconductors, such as CuInS2, are gaining increasing attention for their use in optoelectronic devices such as photovoltaics. These QDs exhibit strong optical absorption and stable, efficient photoluminescence that can be tuned from the visible to the near-infrared via composition and quantum size effects. In fact, Gratzel cells sensitized by specifically engineered group I-III-VI quantum dots have recently been shown to provide excellent stability and certified power conversion efficiencies of >5%. Alloyed CuInS2 x S 2-xZnS / ZnS QDs are particularly attractive materials due to their low toxicity, long-term stability, near-ideal PL lifetime, and other unique optical properties.

[0039] Toxicity remains an issue encountered in QD applications. The use of cadmium-based fluorophores is not feasible for most applications because cadmium is a known carcinogen that bioaccumulates in the human body. Similarly, the most common cadmium-free QD material, indium phosphide, is also a known carcinogen. For near-infrared emission, lead-based QDs are typically used, although the toxicity of lead-based materials is well known. There is still a continued development of non-toxic and non-carcinogenic QD fluorophores that are useful in various systems (e.g., in polar solvent systems). Although the present disclosure preferably relates to non-toxic quantum dots, the development of any quantum dots (including toxic or carcinogenic quantum dots) incorporated into polar materials is conceivable.

[0040] Many desired applications of such quantum dots require that the quantum dots be soluble in polar solvents (e.g., alcohols, water, acetonitrile, dimethylformamide, or dimethyl sulfoxide) so that the quantum dots can be subsequently encapsulated and / or anchored with secondary structures while maintaining a high quantum yield. Some conventional ligands or capping agents (such as dihydrolipoic acid) that can render quantum dots soluble in polar solvents significantly reduce their quantum yield and reduce their utility in many applications.

[0041] Typically, colloidal nanoparticles are synthesized in solutions of long-chain organic surfactants. Consequently, the resulting nanoparticles are capped with surfactant ligands that provide dispersibility in non-polar organic solutions. For dispersibility in polar solvents such as water or alcohol, the initial capping ligands can be replaced with short-chain ligands. Well-known examples of short-chain ligands that provide dispersibility in polar solvents are 3-mercaptopropionic acid (MPA), thioglycerol, and dihydrolipoic acid. Unfortunately, these ligands typically result in a significant reduction in quantum yield (QY), limiting their utility in incorporating them into various media for various applications.

[0042] Therefore, despite previous efforts, developing suitable capping ligands that render nanocrystals soluble in polar solvents or even polar polymers while still providing high quantum yields remains a technical challenge.

[0043] Various embodiments provide technical solutions to these technical challenges. Various embodiments provide novel QD formulations that are soluble in many polar materials (e.g., polar solvents or polar polymers) while maintaining the high quantum yields disclosed herein. These novel QD formulations are generally found to be stable within a pH range of about 6 to about 11. Additionally, this non-toxic, non-carcinogenic QD formulation has an adjustable PL spectrum (with peaks in the visible light (400 to 650 nm) to near-IR (650 to 1400 nm)) and a PL lifetime that preferably varies with the spectrum within the range of 100 to 1000 ns. In some embodiments, multiple sizes and / or compositions of QD emitters can be used in various ratios to achieve a mixture with desired spectral and / or temporal characteristics that are different from the spectral and / or temporal characteristics of the individual component QDs. Thus, it should be understood that adding a second QD composition to a first QD composition can be used to adjust the spectral and / or temporal characteristics of the first QD. CuInS2 / ZnS QDs and similar QDs that also contain selenium (e.g., CuInSe x S 2-x / ZnS QDs, where 0 < x < 2) are preferred (but non-limiting) photoluminescent materials for this purpose. Thus, various embodiments provide technical improvements in the fields of quantum dots and compositions comprising quantum dots and polar solvents or polar polymers. III. Exemplary Quantum Dots and Compositions Comprising Quantum Dots

[0044] Figure 1 A cross-sectional schematic view of an exemplary quantum dot 100 of an exemplary embodiment is provided. In various embodiments, the quantum dot 100 includes a quantum dot body 110 and capping ligands 120 (e.g., 120A, 120B). In various embodiments, the quantum dot body 110 includes a quantum dot core 112 and a quantum dot shell 114. In an exemplary embodiment, the quantum dot body 110 includes only the quantum dot core 112. In an exemplary embodiment, the quantum dot body 110 includes only the quantum dot shell 114.

[0045] In various embodiments, the quantum dot core 112 is formed of or includes CuInS2 or CuInSe x S 2-x formed of or including CuInS2 or CuInSe x S 2-x , where 0 < x < 2). In various embodiments, the quantum dot shell 114 is formed of or includes ZnS. In various embodiments, the quantum dot core 112 and / or the quantum dot shell 114 can include various other materials and / or formulations suitable for the application.

[0046] In the present disclosure, by using one or more independent end-capping ligands 120 on the surface of quantum dot 100, or the independent ligand or multiple end-capping ligand pairs of selection, the solubility of quantum dot in polar solvent is provided. In various embodiments, end-capping ligand 120 comprises sulfhydryl group (also referred to as thiol group). It should be understood that sulfhydryl group is a functional group containing a sulfur atom bonded to a hydrogen atom. In various embodiments, end-capping ligand 120 is provided as a paired end-capping ligand species. For example, the first end-capping ligand 120A and the second end-capping ligand 120B are different molecules. In various embodiments, each of the first end-capping ligand 120A and the second end-capping ligand includes a sulfhydryl group. In exemplary embodiments, only the first end-capping ligand 120A or the second end-capping ligand 120B includes a sulfhydryl group.

[0047] In various embodiments, any number of pairs of capping ligand species may be used as the first capping ligand 120A and the second capping ligand 120B. Some examples of such pairs include: mercaptohexanol and mercaptoethanol; mercaptopropionic acid and mercaptohexanol; mercapto-1-propanol and mercaptohexanol; mercapto-1-propanol and 8-mercapto-1-octanol; mercapto-1-propanol and 9-mercapto-1-nonanol; mercaptoethanol and 8-mercapto-1-octanol; mercaptoethanol and 9-mercapto-1-nonanol; mercaptoethanol and 3-mercapto-1-hexanol; mercaptopropionic acid and 8-mercapto-1-octanol; mercaptopropionic acid and 9-mercapto-1-nonanol; mercaptopropionic acid and 6-mercaptohexanoic acid; mercaptoethanol and 6-mercaptohexanoic acid; mercaptoethanol and 4-mercaptobutyric acid; mercaptohexanol and mercaptosuccinic acid; mercaptoethanol and mercaptosuccinic acid; mercaptoethanol and mercaptoundecanol; and mercaptohexanol and thioglycolic acid. Capping ligand pairs such as mercaptohexanol and mercaptoethanol, mercaptopropionic acid and mercaptoethanol, and mercaptopropionic acid and mercaptohexanol, as well as pairs including 3-(trimethoxysilyl)-1-propanethiol such as 3-(trimethoxysilyl)-1-propanethiol and mercaptohexanol, 3-(trimethoxysilyl)-1-propanethiol and mercaptoethanol, and 3-(trimethoxysilyl)-1-propanethiol and mercaptopropionic acid are generally preferred. 3-(Trimethoxysilyl)-1-propanethiol has been found to be a particularly preferred capping ligand.

[0048] In various embodiments, the capping ligand can include more than one pair of ligands, and can include three or more ligand species (eg, a capping ligand having three or more different molecules).

[0049] In various embodiments, a composition comprising and / or consisting of quantum dots 100 and a polar solvent is provided. Figure 2A picture is provided of a composition 200 comprising quantum dots 100 and a polar solvent 210 within a bottle 5. In the illustrated embodiment, the quantum dots 100 are visible-emitting CuInS2 / ZnS quantum dots in the polar solvent 210, which is an ethanol / water mixture, and the quantum dots 100 include a 1:1 mixture of mercaptoethanol (MCE) and mercaptohexanol (MCH) as the capping ligands 120 (e.g., 120A, 120B).

[0050] Polar solvent 210 is generally any solvent containing an electric dipole. Some non-limiting examples of polar solvents include ethanol, ethanol / water mixtures, isopropanol, isopropanol / water mixtures, methanol, methanol / water mixtures, dimethyl sulfoxide, diethyl sulfoxide, tetrahydrofuran, and tetrahydrofuran / water mixtures. Preferred polar solvents for the ligand-terminated quantum dots of the present invention may include ethanol / water mixtures, dimethyl sulfoxide, methanol, and isopropanol.

[0051] It has been found that such compositions using capping ligands 120 allow the capped quantum dots to photoluminesce when excited with a light source. It has been found that such photoluminescence is generally stable over a period of one week or longer, even in a pH range of about 6 to about 11. Figure 3 Graph 300 illustrates the quantum yield of visible-emitting CuInS2 / ZnS quantum dots 100 in a polar solvent 210 that is an ethanol / water mixture at various pHs, wherein the quantum dots 100 include a 1:1 mixture of mercaptoethanol and mercaptohexanol as the capping ligand 120. Furthermore, as shown in graph 300, the quantum dots 100 can exhibit quantum yields greater than 30%, greater than 50%, greater than 80%, and in some cases, greater than 90%.

[0052] Figure 4 Graph 400 shows the absorption and photoluminescence spectra of visible emitting CuInS2 / ZnS quantum dots 100 in toluene before addition of a capping ligand and then in a polar solvent 210 (an ethanol / water mixture), and subsequently after blending with a 1:1 mixture of mercaptoethanol and mercaptohexanol as the capping ligand 120. As shown in graph 400, it can be seen that the addition of the capping ligand shows substantially no reduction in quantum yield or photoluminescence.

[0053] Figure 5 A graph 500 is provided showing the photoluminescence spectra of visible emitting CuInS2 / ZnS quantum dots 100 in polar solvent 210 (ethanol / water mixture) under different pH conditions according to an exemplary embodiment. As shown in graph 500, the peak photoluminescence emission does not substantially change with changes in the pH of the polar solvent 210.

[0054] Figure 6A photograph of a compound 600 comprising visible emitting CuInS2 / ZnS quantum dots 100 in a polar solvent 210 comprising dimethyl sulfoxide is shown. In the illustrated embodiment, the quantum dots 100 comprise a 1:1 mixture of mercaptoethanol and mercaptohexanol as the capping ligand 120.

[0055] In various embodiments, compositions comprising or consisting of quantum dots 100 and polar polymers or polar polymeric materials are provided. In various embodiments in which quantum dots are mixed with polar polymers or polar polymeric materials, a single capping ligand species 120 may be used and may be selected from the following ligands, for example: mercaptohexanol (MCH), mercaptoethanol (MCE), mercaptoundecanol, thioglycerol, mercaptopropionic acid (MPA), 8-mercapto-1-octanol, 9-mercapto-1-nonanol, 6-mercaptohexanoic acid (MHA), 4-mercaptobutyric acid, mercaptosuccinic acid, thioglycolic acid (TGA), 3-(trimethoxysilyl)-1-propanethiol (MPTMS), and 3-(triethoxysilyl)-1-propanethiol (MPTES). Preferred capping ligands may be selected from the group consisting of 3-(trimethoxysilyl)-1-propanethiol, mercaptohexanol, mercaptoethanol, mercaptoundecanol, thioglycerol, and mercaptopropionic acid. In some cases, more than one capping ligand species may be used. The capping ligands allow for dispersibility in polar polymeric materials. It is desirable that the capped ligand quantum dot composition have good compatibility with polar polymeric materials. When good compatibility is achieved, the resulting mixture typically exhibits reduced haze or fogging in the final composition.

[0056] Some non-limiting examples of polar polymers or polar polymeric materials include polyvinyl alcohol, ethylene-vinyl alcohol copolymers, polyvinyl acetate, ethylene vinyl acetate, polyurethanes, acrylic polymers, and polyamides (eg, nylon).

[0057] Ligand-terminated quantum dots can be combined with polar polymers by co-blending and final extrusion of the blend. Such extruded materials can provide the properties of quantum dots with end-capped ligands described herein. Any suitable process can be used.

[0058] Figure 7 A graph 700 of photoluminescence intensity versus irradiation time is shown, showing the expected lifetime (in years) of (a) native ligand-capped CuInS2 / ZnS quantum dots and (b) mercaptohexanol (MCH) as a capping ligand for H171B EVOH (38 mol% ethylene vinyl alcohol copolymer) as a comparison, according to an exemplary embodiment.

[0059] Figure 8A graph 800 of photoluminescence intensity versus irradiation time is shown, illustrating the expected lifetime (in years) of CuInS2 / ZnS quantum dots 100 including various end-capping ligands 120 extruded in a polymer matrix of F171B EVOH (32 mol % ethylene vinyl alcohol copolymer) according to various embodiments, as well as native ligand CuInS2 / ZnS quantum dots as a standard, as a comparison.

[0060] Figure 9 A graph of photoluminescence intensity versus irradiation time is shown, showing, as a comparison, the expected lifetime (in years) of CuInS2 / ZnS quantum dots 100 comprising a mixture of various end-capping ligands 120 extruded in a polymer matrix of F171B EVOH (32 mol% ethylene vinyl alcohol copolymer) and natural ligand CuInS2 / ZnS quantum dots as a standard. IV. Exemplary Methods for Preparing Compositions Including Quantum Dots

[0061] Figure 10 A flow chart illustrating various processes, procedures and / or operations for preparing a composition comprising quantum dots 100 and a polar host environment is provided. In various embodiments, the polar host environment comprises a polar solvent 210 or a polar polymer or a polar polymer material. Beginning at step 1002, quantum dots with natural ligands are obtained. In various embodiments, quantum dots with natural ligands are obtained by forming quantum dots with natural ligands. Various processes for forming quantum dots with natural ligands may be used where applicable. In some embodiments, quantum dots with natural ligands may be obtained (e.g., purchased) from their manufacturer.

[0062] In step 1004, quantum dots 100 are provided with capping ligands 120 instead of natural ligands. In various embodiments, the capping ligands 120 include at least one ligand having a thiol group. In various embodiments, the capping ligands 120 include a pair of ligands or two or more types of ligands (e.g., three types of ligands or more types of ligands). In an exemplary embodiment, the capping ligands 120 are added in excess to a solution containing quantum dots having natural ligands. For example, the capping ligands 120 can be added in excess to the reaction solution where the quantum dots are formed. The capping ligands 120 can then be bonded to the surface of the quantum dots 100, replacing the natural ligands. In another exemplary embodiment, the solution containing quantum dots can be purified to remove excess natural ligands from the solution. The purification process can include heating, stirring, waiting, and / or the like. For example, in an exemplary embodiment, quantum dots having natural ligands can be blended with a mixture including the desired capping ligands 120 for an appropriate time within an appropriate temperature range. For example, in an exemplary embodiment, copper indium disulfide / zinc sulfide quantum dots are blended with a 1:1 (v / v) mixture of mercaptoethanol and mercaptohexanol as capping ligands 120 at a temperature ranging from about 100° C. to 150° C. for about 1 hour to about 24 hours to form quantum dots 100 having capping ligands 120 of the type mercaptoethanol and mercaptohexanol.

[0063] At step 1006, a composition is formed by suspending quantum dots 100 in a polar solvent or a polar polymer or a polar polymer material. For example, quantum dots 100 and the polar solvent or the polar polymer or the polar polymer material may be mixed together by heating to or maintaining the composition at an appropriate temperature and mixing for an appropriate time. As will be understood by one of ordinary skill in the art, the appropriate temperature and the appropriate time may be determined at least in part based on the properties of the polar solvent, the polar polymer or the polar polymer material.

[0064] At step 1008, the composition may be processed to form a blended material. For example, in an exemplary embodiment, the composition may be dried (e.g., by heating under vacuum) to form the blended material. For example, in various embodiments, the blended material may be a film-like material. In various embodiments, the blended material may be further processed such that the blended material is a powder-like material. For example, the film-like material may be crushed into a fine powder material.

[0065] At step 1010, the mixed material can be extruded to form an extrudate and / or an extruded product. In various embodiments, the extruded product has a quantum yield greater than 1% and an improved lifetime compared to quantum dots without one or more selected capping ligands 120 on the quantum dot surface. The extruded product can then be incorporated into various other products and / or used for various purposes. V. Some Examples of Compositions

[0066] The following examples are non-limiting and are intended merely to further illustrate the compositions, systems, and methods described herein.

[0067] Example 1

[0068] Copper indium disulfide / zinc sulfide (CuInS2 / ZnS) quantum dots (available from Strem Chemicals, Inc., catalog number: 29-8520, having a peak emission of 630 nm + / - 10 nm) were blended with a 1:1 (v / v) mixture of mercaptoethanol and mercaptohexanol as capping ligands at a temperature ranging from about 100°C to 150°C for about 1 hour to about 24 hours.

[0069] The resulting quantum dots were examined and found to have a mixture of mercaptoethanol and mercaptohexanol capping ligands on the shell of the core / shell CuInS2 / ZnS quantum dots. These quantum dots were found to be soluble in polar solvents such as ethanol / water and dimethyl sulfoxide, as Figure 2 and Figure 6 As shown, and when determined by photoluminescence quantum yield measurement using an integrating sphere, the quantum dots have a measured QY of about 95%. In addition, PL was measured in ethanol / water mixtures at pHs ranging from about pH 6 to about pH 11, as shown Figures 3 to 5 The stability of these dots in ethanol / water mixtures is shown in Table 1 below. It was found that the PL remained approximately the same, while the quantum yield increased.

[0070] Example 2

[0071] CuInS2 / ZnS quantum dots (from Strem Chemicals, Inc., catalog number: 29-8520) were blended with a 1:1 (v / v) mixture of mercaptohexanol and mercaptopropionic acid as capping ligands at a temperature range of about 100°C to 150°C for about 1 hour to about 24 hours.

[0072] The resulting quantum dots were examined and found to have a mixture of mercaptohexanol and mercaptopropionic acid capping ligands on the shell of the core / shell CuInS2 / ZnS quantum dots. These quantum dots were found to be soluble in polar solvents such as ethanol / water and had a measured QY of approximately 80% as determined by photoluminescence quantum yield measurements using an integrating sphere.

[0073] Example 3

[0074] The quantum dots of Example 1 were examined and found to have a mixture of mercaptoethanol and mercaptohexanol capping ligands on the shell of the core / shell CuInS2 / ZnS quantum dots. These quantum dots were found to be soluble in polar solvents such as dimethyl sulfoxide, methanol, isopropanol, different ratios of ethanol / water, and various alcohols at different pH conditions. These particular quantum dots were found to be insoluble in solvents such as ethyl acetate, tetrahydrofuran, 1,4-dimethoxybenzyl alcohol, and 1,4-dimethoxybenzyl alcohol. in solvents such as oxane, acetonitrile and acetone.

[0075] Example 4

[0076] The initial quantum dots in Example 1 were capped with only mercaptohexanol capping ligands, and those quantum dots were encapsulated in PVOH as described below. Program Details: 1) In a 40 mL vial, 1.00 g of quantum dots were dissolved in 20 mL of EtOH (w / NH4OH). 2) In separate 20 mL vials, PVOH, THF (seems to aid the solubility of PVOH in H2O), and H2O were added and sonicated until a clear homogeneous solution was formed. 3) The PVOH solution was transferred to a 250 mL round bottom flask equipped with a stir bar. 4) While stirring the PVOH solution, add the solution of quantum dots in EtOH at a rapid dropwise rate. 5) Once the addition was complete, the round bottom flask was fitted with a condenser column and blanketed in nitrogen. The mixture was briefly degassed at room temperature (~5 min) and then heated to 70°C and continued heating for 2 hours. 6) The resulting red clear solution was dried in vacuo at 100°C. 7) Drying produced a red film-like material, which was broken into a fine powder using a spatula and used for subsequent extrusion.

[0077] Example 5

[0078] Using the PVOH prepared in Example 4 to encapsulate quantum dots, quantum dots were extruded in PVA as follows.

[0079] 18.4 g of ethylene vinyl acetate (EVA) pellets and 1.2 g of the PVOH-encapsulated quantum dots from Example 6 were extruded in an extruder at 200°C and 50 rpm. The resulting QD-EVA strands were cut to produce pellets of the blended material. The pellets were hot-pressed to form ~100 μm thick films for optical characterization. The resulting films showed a two-fold improvement in photostability. Extrusion details:

[0080] Example 6

[0081] Additional experiments were performed to explore whether quantum dots capped with mercaptohexanol alone could be extruded within EVOH.

[0082] In an extruder, 18.4 g of ethylene vinyl alcohol (EVOH, H171B grade, purchased from Kuraray America, Inc, 38 mol% ethylene vinyl alcohol copolymer) pellets and 1.2 g of quantum dots capped with MCH were extruded at 220°C at 50, 150 and 250 rpm. The resulting QD-EVOH strands were cut to produce pellets of the mixed material. The pellets were hot pressed to form a film of ~100 μm thickness for optical characterization. The optical properties are given in the table below. The resulting film showed improved haze and light stability, indicating better compatibility in EVOH. The resulting film showed improved light stability ( Figure 6 ), indicating good compatibility in EVOH.

[0083] Example 7

[0084] Additional examples were performed to explore whether quantum dots capped with mercaptoethanol alone could be extruded within EVOH.

[0085] In an extruder, 18.4 g of ethylene vinyl alcohol (EVOH, grade F171B, purchased from Kuraray America, Inc., 32 mol% ethylene vinyl alcohol copolymer) pellets and 1.2 g of MCE-capped quantum dots were extruded at 220°C at 50, 150, and 250 rpm. The resulting QD-EVOH strands were cut to produce pellets of the blended material. The pellets were hot-pressed to form films approximately 100 μm thick for optical characterization. The resulting films showed improved light stability ( Figure 8 ), indicating good compatibility in EVOH.

[0086] Example 8

[0087] Additional examples were performed to explore whether quantum dots capped with mercaptopropionic acid alone could be extruded within EVOH.

[0088] In an extruder, 18.4 g of ethylene vinyl alcohol (EVOH, grade F171B, purchased from Kuraray America, Inc., 32 mol% ethylene vinyl alcohol copolymer) pellets and 1.2 g of MPA-capped quantum dots were extruded at 220°C at 50, 150, and 250 rpm. The resulting QD-EVOH strands were cut to produce pellets of the blended material. The pellets were hot-pressed to form ~100 μm thick films for optical characterization. The resulting films showed improved light stability ( Figure 8 ), indicating good compatibility in EVOH.

[0089] Example 9

[0090] Additional examples were performed to explore whether quantum dots capped with 3-(trimethoxysilyl)-1-propanethiol (MPTMS) alone could be extruded within EVOH.

[0091] In an extruder, 18.4 g of ethylene vinyl alcohol (EVOH, grade F171B, purchased from Kuraray America, Inc., 32 mol% ethylene vinyl alcohol copolymer) pellets and 1.2 g of quantum dots capped with MPTMS were extruded at 220°C at 50, 150, and 250 rpm. The resulting QD-EVOH strands were cut to produce pellets of the blended material. The pellets were hot pressed to form ~100 μm thick films for optical characterization. The resulting films showed improved light stability ( Figure 8 ), indicating good compatibility in EVOH.

[0092] Example 10

[0093] Additional examples were performed to explore whether quantum dots capped with a mixture of mercaptohexanol and mercaptopropionic acid could be extruded within EVOH.

[0094] In an extruder, 18.4 g of ethylene vinyl alcohol (EVOH, grade F171B, purchased from Kuraray America, Inc., 32 mol% ethylene vinyl alcohol copolymer) pellets and 1.2 g of quantum dots capped with a mixture of MCH and MPA were extruded at 220°C at 50, 150, and 250 rpm. The resulting QD-EVOH strands were cut to produce pellets of the blended material. The pellets were hot pressed to form films ~100 μm thick for optical characterization. The resulting films showed improved light stability ( Figure 9 ), indicating good compatibility in EVOH.

[0095] Example 11

[0096] Additional examples were performed to explore whether quantum dots capped with a mixture of mercaptoethanol and mercaptopropionic acid could be extruded within EVOH.

[0097] In an extruder, 18.4 g of ethylene vinyl alcohol (EVOH, grade F171B, purchased from Kuraray America, Inc., 32 mol% ethylene vinyl alcohol copolymer) pellets and 1.2 g of quantum dots capped with a mixture of MCE and MPA were extruded at 220°C at 50, 150, and 250 rpm. The resulting QD-EVOH strands were cut to produce pellets of the blended material. The pellets were hot pressed to form films ~100 μm thick for optical characterization. The resulting films showed improved light stability ( Figure 9 ), indicating good compatibility in EVOH.

[0098] Example 12

[0099] Additional examples were performed to explore whether quantum dots capped with a mixture of mercaptohexanol and mercaptoethanol could be extruded within EVOH.

[0100] In an extruder, 18.4 g of ethylene vinyl alcohol (EVOH, grade F171B, purchased from Kuraray America, Inc., 32 mol% ethylene vinyl alcohol copolymer) pellets and 1.2 g of quantum dots capped with a mixture of MCH and MCE were extruded at 220°C at 50, 150, and 250 rpm. The resulting QD-EVOH strands were cut to produce pellets of the blended material. The pellets were hot pressed to form ~100 μm thick films for optical characterization. The resulting films showed improved light stability ( Figure 9 ), indicating good compatibility in EVOH.

[0101] Example 13

[0102] Due to the similarity of the surface chemistry and optical properties of blue-emitting CuAlS2 QDs, an additional example involves the use of CuAlS2 / ZnS QDs extruded within EVOH.

[0103] In an extruder, 20 g of ethylene vinyl alcohol (EVOH, F171B grade, purchased from Kuraray America, Inc, 32 mol% ethylene vinyl alcohol copolymer) pellets and 1 g of CuAlS2 / ZnS quantum dots capped with a mixture of MCH, MCE, or MPTMS were extruded at 220°C at 50, 150, and 250 rpm. The resulting QD-EVOH strands were cut to produce pellets of the blended material. The pellets were hot-pressed to form films ~100 μm thick for optical characterization. The resulting films showed improved light stability (similar to Figure 9 ), indicating good compatibility and reliability in EVOH.

[0104] In an exemplary embodiment, a quantum dot is provided. The quantum dot comprises at least one inorganic material selected from the group consisting of CuFeSe2, CuFeS2, CuInZnS2, CuZnSnSe2, CuInS2, CuInSe2, CuInSe x S 2-x 、CuInGaSe x S 2-x 、AgInS2.AgInSe2、AgInGaSe x S 2-x , CuAlS2, CuAlSe2, CuAlGaSe x S 2-x , CdS, CdSe, ZnS, and ZnSe; and at least one capping ligand species on the surface of the quantum dot, whereby the quantum dot is characterized by solubility in a polar host environment. At least one capping ligand species comprises a thiol group. The quantum dot is further characterized by exhibiting photoluminescence when excited with a light source, and exhibiting a quantum yield greater than 30%.

[0105] In exemplary embodiments, the at least one capping ligand species is at least one pair of capping ligand species.

[0106] In an exemplary embodiment, at least one pair of capping ligand species is selected from the following pairs: mercaptohexanol and mercaptoethanol, mercaptopropionic acid and mercaptohexanol, mercapto-1-propanol and mercaptohexanol, mercapto-1-propanol and 8-mercapto-1-octanol, mercapto-1-propanol and 9-mercapto-1-nonanol, mercaptoethanol and 8-mercapto-1-octanol, mercaptoethanol and 9-mercapto-1-nonanol, mercaptoethanol and 3-mercapto-1-hexanol, mercaptopropionic acid and 8-mercapto-1-octanol, mercaptopropionic acid and 9-Mercapto-1-nonanol, mercaptopropionic acid and 6-mercaptohexanoic acid, mercaptoethanol and 6-mercaptohexanoic acid, mercaptoethanol and 4-mercaptobutyric acid, mercaptohexanol and mercaptosuccinic acid, mercaptoethanol and mercaptosuccinic acid, mercaptoethanol and mercaptoundecanol, mercaptohexanol and mercaptoacetic acid, 3-(trimethoxysilyl)-1-propanethiol and mercaptohexanol, 3-(trimethoxysilyl)-1-propanethiol and mercaptoethanol, and 3-(trimethoxysilyl)-1-propanethiol and mercaptopropionic acid.

[0107] In exemplary embodiments, at least one pair of capping ligand species is selected from the following pairs: mercaptohexanol and mercaptoethanol, mercaptopropionic acid and mercaptoethanol, and mercaptopropionic acid and mercaptohexanol.

[0108] In an exemplary embodiment, at least one capping ligand species is selected from the group consisting of 3-(trimethoxysilyl)-1-propanethiol, mercaptohexanol, mercaptoethanol, and mercaptopropionic acid.

[0109] In an exemplary embodiment, a composition is provided. The composition includes: a polar solvent; and one or more quantum dots having at least one pair of capping ligand species on a surface of the quantum dots, whereby the quantum dots are soluble in the polar solvent. The composition is further characterized in that the quantum dots exhibit photoluminescence when excited by a light source and the quantum dots exhibit a quantum yield greater than 30%.

[0110] In an exemplary embodiment, each species of at least one pair of capping ligand species comprises a thiol group.

[0111] In an exemplary embodiment, at least one pair of capping ligand species is selected from the following pairs: mercaptohexanol and mercaptoethanol, mercaptopropionic acid and mercaptohexanol, mercapto-1-propanol and mercaptohexanol, 3-(trimethoxysilyl)-1-propanethiol and mercaptohexanol, 3-(trimethoxysilyl)-1-propanethiol and mercaptoethanol, and 3-(trimethoxysilyl)-1-propanethiol and mercaptopropionic acid, mercapto-1-propanol and 8-mercapto-1-octanol, mercapto-1-propanol and 9- Mercapto-1-nonanol, mercaptoethanol and 8-mercapto-1-octanol, mercaptoethanol and 9-mercapto-1-nonanol, mercaptoethanol and 3-mercapto-1-hexanol, mercaptopropionic acid and 8-mercapto-1-octanol, mercaptopropionic acid and 9-mercapto-1-nonanol, mercaptopropionic acid and 6-mercaptohexanoic acid, mercaptoethanol and 6-mercaptohexanoic acid, mercaptoethanol and 4-mercaptobutyric acid, mercaptohexanol and mercaptosuccinic acid, mercaptoethanol and mercaptosuccinic acid, mercaptoethanol and mercaptoundecanol, and mercaptohexanol and thioglycolic acid.

[0112] In an exemplary embodiment, the polar solvent is selected from the group consisting of ethanol, ethanol / water mixtures, isopropanol, isopropanol / water mixtures, methanol, methanol / water mixtures, dimethyl sulfoxide, diethyl sulfoxide, tetrahydrofuran, and tetrahydrofuran / water mixtures.

[0113] In an exemplary embodiment, the polar solvent is an ethanol / water mixture comprising a ratio of about 4 to 1 ethanol to water.

[0114] In an exemplary embodiment, the quantum dots include at least one inorganic material selected from the group consisting of CuFeSe2, CuFeS2, CuInZnS2, CuZnSnSe2, CuInS2, CuInSe2, CuInSe x S 2-x , CuInGaSe x S 2-x , AgInS2.AgInSe2, AgInGaSe x S 2-x , CuAlS2, CuAlSe2, CuAlGaSe x S2-x , CdS, CdSe, ZnS and ZnSe.

[0115] In an exemplary embodiment, the composition has a pH of about 6 to about 11.

[0116] In an exemplary embodiment, a composition is provided. The composition includes: a polar polymeric material; and one or more quantum dots having at least one capping ligand species on a surface of the quantum dot. The polar polymeric material encompasses the quantum dots, whereby the composition is characterized in that the quantum dots are dispersed in the polar polymeric material. The composition is further characterized in that the quantum dots exhibit photoluminescence when excited by a light source, and the quantum dots exhibit a quantum yield greater than 1%.

[0117] In an exemplary embodiment, at least one capping ligand species includes a thiol group.

[0118] In an exemplary embodiment, at least one capping ligand species is selected from the group consisting of mercaptohexanol, mercaptoethanol, mercaptoundecanol, thioglycerol, mercaptopropionic acid, 8-mercapto-1-octanol, 9-mercapto-1-nonanol, 6-mercaptohexanoic acid, 4-mercaptobutyric acid, mercaptosuccinic acid, thioglycolic acid, 3-(trimethoxysilyl)-1-propanethiol, and 3-(triethoxysilyl)-1-propanethiol.

[0119] In an exemplary embodiment, the at least one capping ligand species includes two or more capping ligand species, and each of the two or more capping ligand species includes a thiol group.

[0120] In an exemplary embodiment, at least one of the capping ligand species is a pair of capping ligand species selected from the following pairs: mercaptohexanol and mercaptoethanol, mercaptopropionic acid and mercaptohexanol, mercapto-1-propanol and mercaptohexanol, mercapto-1-propanol and 8-mercapto-1-octanol, mercapto-1-propanol and 9-mercapto-1-nonanol, mercaptoethanol and 8-mercapto-1-octanol, mercaptoethanol and 9-mercapto-1-nonanol, mercaptoethanol and 3-mercapto-1-hexanol, mercaptopropionic acid and 8-mercapto-1-octanol, mercaptopropionic acid and 9-mercapto-1-nonanol, mercaptopropionic acid and 6-mercaptohexanoic acid, mercaptoethanol and 6-mercaptohexanoic acid, mercaptoethanol and 4-mercaptobutyric acid, mercaptohexanol and mercaptosuccinic acid, mercaptoethanol and mercaptosuccinic acid, mercaptoethanol and mercaptoundecanol, and mercaptohexanol and thioglycolic acid.

[0121] In an exemplary embodiment, the polar polymeric material is selected from the group consisting of polyvinyl alcohol, ethylene vinyl alcohol copolymer, polyvinyl acetate, ethylene vinyl acetate, polyurethane, polyamide, and acrylic polymer.

[0122] In an exemplary embodiment, the quantum dots include at least one inorganic material selected from the group consisting of CuFeSe2, CuFeS2, CuInZnS2, CuZnSnSe2, CuInS2, CuInSe2, CuInSe x S 2-x 、CuInGaSe x S 2-x 、AgInS2.AgInSe2、AgInGaSe x S 2-x , CuAlS2, CuAlSe2, CuAlGaSe x S 2-x , CdS, CdSe, ZnS and ZnSe.

[0123] In an exemplary embodiment, the composition is extruded into an extruded product. VI. Conclusion

[0124] Although the present invention has been described with reference to specific details, it is not intended that such exemplary details be considered as limiting the scope of the invention. Various modifications, substitutions, combinations, and range selections or applications of the parameters in the compositions and methods described herein may be made.

[0125] Many modifications and other embodiments of the disclosure set forth herein will occur to those skilled in the art having the benefit of the foregoing description and the teachings presented in the associated drawings. Therefore, it should be understood that the claims are not limited to the specific embodiments disclosed, and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a general, descriptive sense only and not for purposes of limitation.

Claims

1. Quantum dots, including: At least one inorganic material selected from the group consisting of CuFeSe2, CuFeS2, CuInZnS2, CuZnSnSe2, CuInS2, CuInSe2, CuInSe x S 2-x 、CuInGaSe x S 2-x 、AgInS2.AgInSe2、AgInGaSe x S 2-x , CuAlS2, CuAlSe2, CuAlGaSe x S 2-x , CdS, CdSe, ZnS and ZnSe; as well as at least one capping ligand species on the surface of the quantum dot, whereby the quantum dot is characterized by solubility in a polar host environment, wherein the at least one capping ligand species comprises a thiol group, The quantum dots are further characterized in that they exhibit photoluminescence when excited by a light source, and the quantum dots exhibit a quantum yield greater than 30%.

2. The quantum dot according to claim 1, wherein The at least one capping ligand species is at least one pair of capping ligand species.

3. The quantum dot according to claim 2, wherein The at least one pair of capping ligand species is selected from the following pairs: mercaptohexanol and mercaptoethanol, mercaptopropionic acid and mercaptohexanol, mercapto-1-propanol and mercaptohexanol, mercapto-1-propanol and 8-mercapto-1-octanol, mercapto-1-propanol and 9-mercapto-1-nonanol, mercaptoethanol and 8-mercapto-1-octanol, mercaptoethanol and 9-mercapto-1-nonanol, mercaptoethanol and 3-mercapto-1-hexanol, mercaptopropionic acid and 8-mercapto-1-octanol, mercaptopropionic acid and 9-mercapto -1-nonanol, mercaptopropionic acid and 6-mercaptohexanoic acid, mercaptoethanol and 6-mercaptohexanoic acid, mercaptoethanol and 4-mercaptobutyric acid, mercaptohexanol and mercaptosuccinic acid, mercaptoethanol and mercaptosuccinic acid, mercaptoethanol and mercaptoundecanol, mercaptohexanol and mercaptoacetic acid, 3-(trimethoxysilyl)-1-propanethiol and mercaptohexanol, 3-(trimethoxysilyl)-1-propanethiol and mercaptoethanol, and 3-(trimethoxysilyl)-1-propanethiol and mercaptopropionic acid.

4. The quantum dot according to claim 2, wherein The at least one pair of capping ligand species is selected from the following pairs: mercaptohexanol and mercaptoethanol, mercaptopropionic acid and mercaptoethanol, and mercaptopropionic acid and mercaptohexanol.

5. The quantum dot according to claim 1, wherein The at least one capping ligand species is selected from the group consisting of 3-(trimethoxysilyl)-1-propanethiol, mercaptohexanol, mercaptoethanol, and mercaptopropionic acid.

6. A composition comprising: Polar solvents; as well as One or more quantum dots, the one or more quantum dots having at least a pair of capping ligand species on a surface of the quantum dots, whereby the quantum dots are soluble in the polar solvent, the composition being further characterized in that the quantum dots exhibit photoluminescence when excited with a light source, and the quantum dots exhibit a quantum yield greater than 30%.

7. The composition according to claim 6, wherein Each species of the at least one pair of capping ligand species comprises a thiol group.

8. The composition according to claim 6, wherein The at least one pair of end-capping ligand species is selected from the following pairs: mercaptohexanol and mercaptoethanol, mercaptopropionic acid and mercaptohexanol, mercapto-1-propanol and mercaptohexanol, 3-(trimethoxysilyl)-1-propanethiol and mercaptohexanol, 3-(trimethoxysilyl)-1-propanethiol and mercaptoethanol, and 3-(trimethoxysilyl)-1-propanethiol and mercaptopropionic acid, mercapto-1-propanol and 8-mercapto-1-octanol, mercapto-1-propanol and 9-mercapto-1 -nonanol, mercaptoethanol and 8-mercapto-1-octanol, mercaptoethanol and 9-mercapto-1-nonanol, mercaptoethanol and 3-mercapto-1-hexanol, mercaptopropionic acid and 8-mercapto-1-octanol, mercaptopropionic acid and 9-mercapto-1-nonanol, mercaptopropionic acid and 6-mercaptohexanoic acid, mercaptoethanol and 6-mercaptohexanoic acid, mercaptoethanol and 4-mercaptobutyric acid, mercaptohexanol and mercaptosuccinic acid, mercaptoethanol and mercaptosuccinic acid, mercaptoethanol and mercaptoundecanol, and mercaptohexanol and thioglycolic acid.

9. The composition according to claim 6, wherein The polar solvent is selected from the group consisting of ethanol, ethanol / water mixtures, isopropyl alcohol, isopropyl alcohol / water mixtures, methanol, methanol / water mixtures, dimethyl sulfoxide, diethyl sulfoxide, tetrahydrofuran, and tetrahydrofuran / water mixtures.

10. The composition according to claim 6, wherein The polar solvent is an ethanol / water mixture comprising a ratio of about 4 to 1 ethanol to water.

11. The composition according to claim 6, wherein The quantum dots include at least one inorganic material selected from the group consisting of CuFeSe2, CuFeS2, CuInZnS2, CuZnSnSe2, CuInS2, CuInSe2, CuInSe x S 2-x 、CuInGaSe x S 2-x ,AgInS2.AgInSe2,AgInGaSe2S 2-x , CuAlS2, CuAlSe2, CuAlGaSe x S 2-x , CdS, CdSe, ZnS and ZnSe.

12. The composition according to claim 6, wherein The composition has a pH of about 6 to about 11.

13. A composition comprising: Polar polymer materials; as well as one or more quantum dots, the one or more quantum dots having a capping ligand on a surface of the quantum dot, Wherein, the polar polymer material includes the quantum dots, and thus the composition is characterized in that the quantum dots are dispersed in the polar polymer material, and the composition is further characterized in that the quantum dots exhibit photoluminescence when excited by a light source, and the quantum dots exhibit a quantum yield greater than 1%.

14. The composition according to claim 13, wherein The capping ligand includes a thiol group.

15. The composition according to claim 13, wherein The capping ligand is selected from the group consisting of mercaptohexanol, mercaptoethanol, mercaptoundecanol, thioglycerol, mercaptopropionic acid, 8-mercapto-1-octanol, 9-mercapto-1-nonanol, 6-mercaptohexanoic acid, 4-mercaptobutyric acid, mercaptosuccinic acid, thioglycolic acid, 3-(trimethoxysilyl)-1-propanethiol, and 3-(triethoxysilyl)-1-propanethiol.

16. The composition according to claim 13, wherein The capping ligand includes two or more capping ligand species, and each of the two or more capping ligand species includes a thiol group.

17. The composition according to claim 13, wherein The blocking ligand is a pair of blocking ligand species selected from the following pairs: mercaptohexanol and mercaptoethanol, mercaptopropionic acid and mercaptohexanol, mercapto-1-propanol and mercaptohexanol, mercapto-1-propanol and 8-mercapto-1-octanol, mercapto-1-propanol and 9-mercapto-1-nonanol, mercaptoethanol and 8-mercapto-1-octanol, mercaptoethanol and 9-mercapto-1-nonanol, mercaptoethanol and 3-mercapto-1-hexanol, mercaptopropionic acid and 8-mercapto-1-octanol, mercaptopropionic acid and 9-mercapto-1-nonanol, mercaptopropionic acid and 6-mercaptohexanoic acid, mercaptoethanol and 6-mercaptohexanoic acid, mercaptoethanol and 4-mercaptobutyric acid, mercaptohexanol and mercaptosuccinic acid, mercaptoethanol and mercaptosuccinic acid, mercaptoethanol and mercaptoundecanol, and mercaptohexanol and thioglycolic acid.

18. The composition according to claim 13, wherein The polar polymer material is selected from the group consisting of polyvinyl alcohol, ethylene vinyl alcohol copolymer, polyvinyl acetate, ethylene vinyl acetate, polyurethane, polyamide, and acrylic polymer.

19. The composition according to claim 15, wherein The quantum dots include at least one inorganic material selected from the group consisting of CuFeSe2, CuFeS2, CuInZnS2, CuZnSnSe2, CuInS2, CuInSe2, CuInSe x S 2-x 、CuInGaSe x S 2-x ,AgInS2.AgInSe2,AgInGaSe2S 2-x , CuAlS2, CuAlSe2, CuAlGaSe x S 2-x , CdS, CdSe, ZnS and ZnSe.

20. The composition according to claim 15, wherein The composition is extruded into an extruded product.

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