Nanoparticle ligands for polar host environments

Abstract

Quantum dots are provided that include 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; and at least one species of capping ligand upon a surface of the quantum dots whereby the quantum dots are characterized as having solubility in polar host environments. Each species of capping ligands includes a mercapto group. The quantum dots are further characterized by exhibiting a photoluminescence upon excitation with a light source and the quantum dots exhibiting a quantum yield of greater than 30 percent. Compositions including the quantum dots and a polar host environment as also provided.

Description

NANOPARTICLE LIGANDS FOR POLAR HOST ENVIRONMENTS FIELD

[0001] Various embodiments are directed to nanoparticle formulations wherein the nanoparticles include ligands capping the nanoparticles such that the nanoparticles have solubility in a number of polar materials whether polar solvents or polar polymers. In various embodiments, these formulations and can maintain high quantum yield above 70% including in some instances even under pHs of from about 6 up to pHs of 11 or more. Such nanoparticles can be photoluminescent nanoparticle materials such as quantum dots. BACKGROUND OF THE DISCLOSURE

[0002] Colloidal semiconductor nanoparticles, commonly known as quantum dots (QDs), provide various size-tunable optical properties, including photoluminescence (PL), and may be inexpensively processed from liquids. In particular, such QDs can be very effective at absorbing a broad spectrum of light and then converting or re-emitting light of a single color that is determined by the size of the QDs. Optical properties (such as, for example, absorption and emission spectra, PL lifetimes, and Stokes shifts) of these materials can be controlled or tailored via manufacturing conditions to obtain different sizes, shapes, compositions, and / or heterostructures. This fundamental property of QDs has spurred research and development of fluorescence biolabeling, color-specific light-emitting diodes and vibrant QD containing displays. Numerous non-toxic QDs are now being developed as active elements of luminescent composites for various applications, including, e.g., lighting, solar cells, safety, security inks and agriculture. However, Photoluminescent materials or quantum dots including long insulating carbon chain capping ligands such as oleic acid, stearic acid., and the like, are often found insoluble or mostly insoluble in polar solvents. BRIEF SUMMARY

[0003] In one aspect, quantum dots are provided. In an example embodiment, the quantum dots having at least a pair of selected capping ligands upon the surface of the quantum dots whereby the quantum dots are characterized as having solubility in a polar solvent. The quantum - 1 - AttyDktNo: 074644 / 605937dots are further characterized by exhibiting photoluminescence upon excitation with a light source with a quantum yield of greater than 30 percent.

[0004] In another aspect, quantum dots are provided. In an example embodiment, the quantum dots have a capping ligand upon the surface of the quantum dots whereby the quantum dots are characterized as having solubility in a polar solvent. The quantum dots are further characterized by exhibiting photoluminescence upon excitation with a light source with a quantum yield of greater than 30 percent.

[0005] In another aspect, a composition is provided. In an example embodiment, the composition includes a polar solvent and quantum dots having at least a pair of selected capping ligands upon the surface of the quantum dots whereby the quantum dots have solubility in the polar solvent. The composition is further characterized by the quantum dots exhibiting photoluminescence upon excitation with a light source such that the quantum dots exhibit a quantum yield of greater than 30 percent.

[0006] In still another aspect, a composition is provided. In an example embodiment, the composition includes a polar polymeric material and quantum dots having one or more selected capping ligands upon the surface of the quantum dots. The polar polymeric material encompasses the quantum dots, whereby the composition is characterized by the quantum dots having dispersibility in the polar polymeric material. The composition is further characterized by the quantum dots exhibiting photoluminescence upon excitation with a light source such that the quantum dots exhibit a quantum yield of greater than 1 percent.

[0007] In an example embodiment, such a composition is provided as an extruded product having a quantum yield of greater than 1 percent, and an improved lifetime in comparison to quantum dots without the one or more selected capping ligands upon the surface of the quantum dots. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Fig.1 provides a schematic diagram of a quantum dot including capping ligands, in accordance with an example embodiment.

[0009] Fig.2 shows a picture of an example composition including quantum dots and a polar solvent, in accordance with an example embodiment. - 2 - AttyDktNo: 074644 / 605937

[0010] Fig.3 shows a plot of the quantum yield of visible emitting CuInS2 / ZnS quantum dots in an ethanol / water mixture at different pHs, the quantum dots including a 1:1 mixture of mercaptoethanol and mercaptohexanol as capping ligands, in accordance with various embodiments.

[0011] Fig.4 shows a plot of the absorption and photoluminescence spectra of visible emitting CuInS2 / ZnS quantum dots both in toluene before addition of capping ligands and then in an ethanol / water mixture, following admixing with a 1:1 mixture of mercaptoethanol and mercaptohexanol as capping ligands, in accordance with an example embodiment.

[0012] Fig.5 shows photoluminescence spectra of visible emitting CuInS2 / ZnS quantum dots in an ethanol / water mixture under different pH conditions, in accordance with an example embodiment.

[0013] Fig.6 shows a picture of visible emitting CuInS2 / ZnS quantum dots in a dimethyl sulfoxide, the quantum dots including a 1:1 mixture of mercaptoethanol and mercaptohexanol as capping ligands, in accordance with an example embodiment.

[0014] Fig.7 shows a plot of photoluminescent intensity against illumination time showing expected lifetime in years for (a) native ligand capped CuInS2 / ZnS quantum dots and (b) mercaptohexanol (MCH) as capping ligands of H171B EVOH (38 mol % Ethylene Vinyl- Alcohol Copolymer) in comparison, in accordance with an example embodiment.

[0015] Fig.8 shows a plot of photoluminescent intensity against illumination time showing expected lifetime in years for CuInS2 / ZnS quantum dots including various capping ligands extruded in a polymer matrix of F171B EVOH (32 mol % Ethylene Vinyl-Alcohol Copolymer), in accordance with various embodiments, and native ligand CuInS2 / ZnS quantum dots as a standard in comparison.

[0016] Fig.9 shows a plot of photoluminescent intensity against illumination time showing expected lifetime in years for CuInS2 / ZnS quantum dots including mixture of various capping ligands extruded in a polymer matrix of F171B EVOH (32 mol % Ethylene Vinyl-Alcohol Copolymer), in accordance with various embodiments, and native ligand CuInS2 / ZnS quantum dots as a standard in comparison.

[0017] Fig.10 provides a flowchart illustrating various processes, procedures, and / or operations for forming a composition comprising quantum dots having capping ligands, in accordance with various embodiments. - 3 - AttyDktNo: 074644 / 605937DETAILED DESCRIPTION

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

[0019] As used herein, “comprising” means “including,” and the singular form “a” or “an” or “the” include plural references unless the context clearly indicates otherwise. Unless the context clearly indicates otherwise, the term “or” is inclusive, and thus refers to both a single element of stated alternative elements and a combination of two or more of those elements.

[0020] Unless explained otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one or ordinary skill in the art to which this disclosure relates. Suitable methods and compositions are described herein for the practice or testing of the systems, methodologies and compositions described herein. However, it is to be understood that other methods and materials similar, or equivalent to, those described herein may be used in the practice or testing of these systems, methodologies and compositions disclosed herein. Consequently, the systems, methodologies, compositions, and examples disclosed herein are illustrative only, and are not intended to be limiting. Other features of the present disclosure will be apparent to those skilled in the art from the following detailed description and the appended claims.

[0021] Unless otherwise indicated, all numbers expressing quantities of components, percentages, temperatures, times, and so forth as used in the specification or claims are to be understood as being modified by the term “about.” Unless otherwise indicated, non-numerical properties such as colloidal, continuous, crystalline, and so forth as used in the specification or claims are to be understood as being modified by the term “substantially,” meaning to a great extent or degree. Accordingly, unless otherwise indicated implicitly or explicitly, the numerical parameter and / or non-numerical properties set forth herein are approximations, and the optimal values of these properties and parameters may depend on the desired properties sought, the limits of detection under standard test conditions or methods, the limitations of the processing methods, and / or the nature of the property or parameter. When directly and explicitly distinguishing embodiments from disclosed prior art, the embodiment numbers are not approximations unless the word “about” is recited. - 4 - AttyDktNo: 074644 / 605937I. Definitions

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

[0023] Colloidal suspension: A mixture consisting of a disperse phase (the suspended particles) and a continuous phase (the liquid medium of suspension), wherein the mixture either does not settle, or would take a very long time to settle appreciably.

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

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

[0026] Flocculation: A process whereby the disperse 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 size of less than 500 nanometers in dimension. The nanoparticles disclosed herein may form a colloidal suspension. Embodiments of the disclosed nanoparticles may be of a single material or may include an inner core and an outer shell of differing materials. The nanoparticles may further include a plurality of ligands bound to the nanoparticle outer surface. Exemplary nanoparticles which may be utilized in the compositions, systems and methodologies described herein may comprise metals, metal oxides, metal chalcogenides, semiconductors, and insulators. Nanoparticles may be crystalline (i.e., nanocrystals), amorphous, or mixtures thereof.

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

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

[0030] Polymers (as well as polar polymers): A large molecule, or macromolecule, composed of many repeating subunits. Polymers range from familiar synthetic plastics such as - 5 - AttyDktNo: 074644 / 605937polystyrene or poly (methyl methacrylate) (PMMA), to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers, both natural and synthetic, are created via polymerization of many smaller molecules, e.g., monomers. Exemplary polymers include poly (methyl methacrylate) (PMMA), polystyrene, silicones, epoxy resins and the like.

[0031] Polar polymers: Polymers containing only carbon and hydrogen atoms are non-polar polymers. Polar polymers typically contain other atoms such as chlorine, fluorine, oxygen, nitrogen, and sulfur whereby the polymer will contain a permanent electric dipole called a polar polymer. Exemplary polar polymers include poly vinyl alcohol, an ethylene vinyl alcohol copolymer, polyvinyl acetate, polyurethane, ethylene vinyl acetate, an acrylic polymer, polyvinyl butyral, and polyamides, e.g., nylons.

[0032] Quantum Dots: 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 may be colloidal quantum dots. Some of the quantum dots which may be utilized in the compositions, systems and methodologies described herein are made from a binary semiconductor material having a 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 which may be used in the compositions, systems and methodologies described herein include CdS, CdSe, CdTe, PbS, PbSe, PbTe, ZnS, ZnSe, ZnTe, InP, InAs, Cu2S, and In2S3.Other quantum dots which may be utilized in the compositions, systems and methodologies 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, CuAlGaSexS2-x(0 ≤ x ≤ 2), CuAlSexS2-x(0 ≤ x ≤ 2), CuAlTe2, CuFeS2, CuFeSe2, CuFeTe2, CuInS2, CuInSe2, CuInTe2, CuInGaSe2, CuInGaS2, CuInGaTe2, CuInZnS2, CuZnSnSe2, CuZnSexS2-x (0 ≤ x ≤ 2), CuInSexS2-x (0 ≤ x ≤ 2), CuInGaSexS2-x (0 ≤ x ≤ 2), CuInZnSexS2-x (0 ≤ x ≤ 2), AgInS2, AgInSe2, AgInGaSexS2-x(0 ≤ x ≤ 2),and AgInSexS2-x(0 ≤ x ≤ 2), quantum dots, although the use of non-toxic quantum dots is preferred. For example, in various embodiments, the quantum dots include ternary, quaternary, and / or alloyed quantum dots including, but not - 6 - AttyDktNo: 074644 / 605937limited 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 free, e.g., of cadmium, lead and mercury. Embodiments of the disclosed quantum dots may be of a single material or may include an inner core and an outer shell of differing materials. The outer shell may be a thin shell or layer formed by any suitable method, such as cation exchange. The quantum dots further include a plurality of ligands bound to the quantum dot surface.

[0033] Ligand: A ligand is an ion or molecule that binds to another, usually larger, molecule. In general, a ligand bonds to a metal atom, which in the case of the present disclosure, is part of a quantum dot and / or nanoparticle. A ligand may be configured to bind to a particular receptor, interact with various types of matter in prescribed ways, and / or the like. Capping ligands are configured to stabilize the interface where nanoparticles, such as quantum dots, interact with their surrounding medium.

[0034] Solubility: When used in reference to QDs, the ability of QDs to form a clear colloidal suspension without haze caused by formation of aggregates.

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

[0036] The present disclosure is concerned with capping ligands for nanoparticles such as quantum dots where the capping ligands allow for the solubility of the nanoparticles 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 including quantum dots in a polar solvent. Various embodiments provide quantum dots embedded in an extrusion formed of a polar polymer.

[0038] Nanoparticle quantum dots of the I-III-VI class of semiconductors, such as, CuInS2, are of growing interest for applications 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 through composition and quantum size effects. In fact, Gratzel cells sensitized by specifically engineered I-III-VI quantum dots have recently been shown to offer excellent stability and certified power conversion efficiencies of >5%. Alloyed - 7 - AttyDktNo: 074644 / 605937CuInSexS2-x / ZnS QDs are particularly attractive materials because of their low toxicity, long term stability, nearly ideal PL lifetime and other unique optical properties.

[0039] Toxicity remains an issue encountered in QD applications. The use of cadmium-based fluorophores is a non-starter for most applications since cadmium is a known carcinogen that bio-accumulates in the human body. Similarly, the most common cadmium-free QD material, indium phosphide, is also a known carcinogen. For near-IR emission, lead-based QDs are typically used, despite the fact that the toxicity of lead-based materials is well known. The continued development of non-toxic and non-carcinogenic QD fluorophores useful within a variety of systems such as within polar solvent systems remains. While the present disclosure is preferably directed towards non-toxic quantum dots, the developments in incorporating any quantum dot, including toxic or carcinogenic quantum dots, into polar materials is contemplated.

[0040] Many desirable applications for such quantum dots require the quantum dots to be soluble in polar solvents such as alcohols, water, acetonitrile, dimethylforamide, or dimethyl sulfoxide for subsequent encapsulation and / or anchoring of the quantum dots with secondary structures while maintaining high quantum yields. Some conventional ligands or capping agents (such as dihydrolipoic acid) capable of making quantum dots soluble in polar solvents significantly reduce their quantum yields and decrease their utility in many applications.

[0041] Typically, colloidal nanoparticles are synthesized in long chain organic surfactant solutions. Consequently, the resultant nanoparticles are capped with the surfactant ligands that provide dispersibility in non-polar organic solutions. For dispersibility into polar solvents such as water or alcohols, the initial capping ligands may be replaced with short chain ligands. Among the well-known examples of short chain ligands providing dispersibility in polar solvents are 3- mercaptopropionic acid (MPA), thioglycerol, dihydrolipoic acid. Unfortunately, these ligands often resulted in a significant reduction in the quantum yield (QY) thereby limiting their utility for incorporation into different media for various applications.

[0042] Therefore, despite prior efforts, technical challenges remain to develop suitable capping ligands whereupon the nanocrystals have solubility in polar solvents or even polar polymers while still providing high quantum yield.

[0043] Various embodiments provide technical solutions to these technical challenges. Various embodiments provide novel QD formulations having solubility within a number of polar materials, e.g., polar solvents or polar polymers while maintaining high quantum yields are - 8 - AttyDktNo: 074644 / 605937disclosed herein. These novel QD formulations have often been found stable within pH ranges of from about 6 to about 11. Further, such non-toxic, non-carcinogenic QD formulations have tunable PL spectra with peaks in the visible (400-650 nm) to near-IR (650-1400 nm) and spectrally varying PL lifetimes which are preferably within the range of 100 to 1000 ns. In some embodiments, multiple sizes and / or compositions of QD emitters may be used in various ratios to achieve mixtures having desired spectral and / or temporal characteristics that differ from those of the individual component QDs. It will be thus appreciated that the addition of a second QD composition to a first QD composition may be utilized to modify the spectrum and / or temporal characteristics of the first QD. CuInS2 / ZnS QDs and analogous QDs also containing selenium, e.g., CuInSexS2-x / ZnS QDs where 0 < x < 2, are preferred (though non-limiting) photoluminescent materials for this purpose. Thus, various embodiments provide technical improvements in the fields of quantum dots and compositions including quantum dots and polar solvents or polar polymers. III. Example Quantum Dots and Compositions Comprising Quantum Dots

[0044] Figure 1 provides a cross-sectional schematic diagram of an example quantum dot 100 of an example embodiment. In various embodiments, a 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 example embodiment, the quantum dot body 110 only includes a quantum dot core 112. In an example embodiment, the quantum dot body 110 only includes a quantum dot shell 114.

[0045] In various embodiments, the quantum dot core 112 is formed of or comprises CuInS2or CuInSexS2-x, where 0 < x < 2. In various embodiments, the quantum dot shell 114 is formed of or comprises ZnS. In various embodiments, the quantum dot core 112 and / or quantum dot shell 114 may include various other materials and / or formulations, as appropriate for the application.

[0046] In the present disclosure, the solubility of quantum dots in polar solvents is provided by use of a one or more individual capping ligands 120, either selected individual ligands or a variety of pairs of capping ligands upon the surface of the quantum dots 100. In various embodiments, the capping ligands 120 comprise a mercapto group (also known as a thiol group). As should be understood, mercapto group is a functional group containing a sulfur atom bonded to a hydrogen atom. In various embodiments, the capping ligands 120 are provided as pairs of - 9 - AttyDktNo: 074644 / 605937species of capping ligands. For example, the first capping ligands 120A are different molecules than the second capping ligands 120B. In various embodiments, each of the first capping ligands 120A and the second capping ligands include a mercapto group. In an example embodiment, only of the first capping ligands 120A or the second capping ligands 120B include a mercapto group.

[0047] In various embodiments, a number of capping ligand species pairs may be used as the first capping ligands 120A and the second capping ligands 120B. Some examples of such species 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 are generally preferred 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.3-(trimethoxysilyl)-1- propanethiol has been found to be an especially preferred capping ligand.

[0048] In various embodiments, the capping ligands may include more than a pair of ligands and may include three or more species of ligands (e.g., capping ligands that are of three or more distinct molecules).

[0049] In various embodiments, compositions are provided that comprise and / or consist of quantum dots 100 and a polar solvent. Figure 2 provides a picture 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 polar solvent 210 that is an ethanol / water mixture and the quantum dots 100 include a 1:1 mixture of - 10 - AttyDktNo: 074644 / 605937mercaptoethanol (MCE) and mercaptohexanol (MCH) as capping ligands 120 (e.g., 120A, 120B).

[0050] Polar solvents 210 are generally any solvent containing an electric dipole. Some non- limiting examples of polar solvents include ethanol, an ethanol / water mixture, isopropanol, an isopropanol / water mixture, methanol, a methanol / water mixture, dimethyl sulfoxide, diethyl sulfoxide, tetrahydrofuran, and a tetrahydrofuran / water mixture. Preferred polar solvents with the ligand capped quantum dots of this invention can include an ethanol / water mixture, dimethyl sulfoxide, methanol, and isopropanol.

[0051] It has been found that use of such combinations of capping ligands 120 allows photoluminescence by the capped quantum dots upon excitation with a light source. Such photoluminescence has been found to generally be stable over time periods of a week or longer even under pH ranges of from about 6 to about 11. Figure 3 shows a plot 300 of the quantum yield of visible emitting CuInS2 / ZnS quantum dots 100 in a polar solvent 210 that is an ethanol / water mixture at different pHs, where the quantum dots 100 include a 1:1 mixture of mercaptoethanol and mercaptohexanol as capping ligands 120. Further, as shown by plot 300, the quantum dots 100 can exhibit quantum yields of greater than 30 percent, of greater than 50 percent, of greater than 80 percent and in some instances of greater than 90 percent.

[0052] Figure 4 shows a plot 400 of the absorption and photoluminescence spectra of visible emitting CuInS2 / ZnS quantum dots 100 in toluene before addition of capping ligands and then in a polar solvent 210 (an ethanol / water mixture), following admixing with a 1:1 mixture of mercaptoethanol and mercaptohexanol as capping ligands 120. As shown in plot 400, it was seen that addition of the capping ligands showed essentially no reduction in the quantum yield or photoluminescence.

[0053] Figure 5 provides a plot 500 showing the photoluminescence spectra of visible emitting CuInS2 / ZnS quantum dots 100 in a polar solvent 210 (an ethanol / water mixture) under different pH conditions, in accordance with an example embodiment. As shown in plot 500, the peak photoluminescence emission was essentially unchanged by the change in pH of the polar solvent 210.

[0054] Figure 6 shows a picture of a compound 600 comprising visible emitting CuInS2 / ZnS quantum dots 100 in a polar solvent 210 that comprises dimethyl sulfoxide. In the illustrated - 11 - AttyDktNo: 074644 / 605937embodiment, the quantum dots 100 include a 1:1 mixture of mercaptoethanol and mercaptohexanol as capping ligands 120.

[0055] In various embodiments, compositions are provided that comprise or consist of quantum dots 100 and a polar polymer or polar polymeric material. In various embodiments in which the quantum dots are to be blended with polar polymers or polar polymeric materials, a single species of capping ligand 120 may be used and can be from among the following ligands, e.g., 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). The preferred capping ligand can be from among 3-(trimethoxysilyl)-1-propanethiol, mercaptohexanol, mercaptoethanol, mercaptoundecanol, thioglycerol, mercaptopropionic acid. In some instances, more than a single species of capping ligands may be employed. The capping ligand allows dispersibility in the polar polymeric material. The capping ligand quantum dot composition is desired to have good compatibility with the polar polymeric material. Where good compatibility is achieved, the resultant blend generally exhibits reduced haze or hazing in the final composition.

[0056] Some non-limiting examples of polar polymers or polar polymeric materials include poly vinyl alcohol, an ethylene vinyl alcohol copolymer, polyvinyl acetate, ethylene vinyl acetate, polyurethane, an acrylic polymer, and polyamides, (e.g., nylons).

[0057] The ligand-capped quantum dots can be combined with the polar polymers by co- blending and eventually extrusion of the blend. Such extruded material can provide the properties of the quantum dots with the capping ligands described herein. Any suitable process can be employed.

[0058] Figure 7 shows a plot 700 of photoluminescent intensity against illumination time showing expected lifetime in years for (a) native ligand capped CuInS2 / ZnS quantum dots and (b) mercaptohexanol (MCH) as capping ligands of H171B EVOH (38 mol % Ethylene Vinyl- Alcohol Copolymer) in comparison, in accordance with an example embodiment.

[0059] Figure 8 shows a plot 800 of photoluminescent intensity against illumination time showing expected lifetime in years for CuInS2 / ZnS quantum dots 100 including various capping - 12 - AttyDktNo: 074644 / 605937ligands 120 extruded in a polymer matrix of F171B EVOH (32 mol % Ethylene Vinyl-Alcohol Copolymer), and native ligand CuInS2 / ZnS quantum dots as a standard in comparison.

[0060] Figure 9 shows a plot 900 of photoluminescent intensity against illumination time showing expected lifetime in years for CuInS2 / ZnS quantum dots 100 including mixture of various capping ligands 120 extruded in a polymer matrix of F171B EVOH (32 mol % Ethylene Vinyl-Alcohol Copolymer), and native ligand CuInS2 / ZnS quantum dots as a standard in comparison. IV. Example Methods for Making Compositions Including Quantum Dots

[0061] Figure 10 provides a flowchart illustrating various processes, procedures, and / or operations for making compositions including quantum dots 100 and a polar host environment. In various embodiments, the polar host environment includes a polar solvent 210 or a polar polymer or a polar polymeric material. Starting at step 1002, quantum dots having native ligands are obtained. In various embodiments, the quantum dots having native ligands are obtained by forming the quantum dots having native ligands. Various processes may be used for forming the quantum dots having native ligands, as appropriate for the application. In some embodiments, quantum dots having native ligands may be obtained (e.g., purchased) from a manufacturer thereof.

[0062] At step 1004, the native ligands are replaced with the capping ligands 120 to provide quantum dots 100. In various embodiments, the capping ligands 120 include at least one species of ligand having a mercapto group. In various embodiments, the capping ligands 120 include a pair of species of ligands or more than two species of ligands (e.g., three species of ligands or more). In an example embodiment, the capping ligands 120 are added to in excess to a solution containing the quantum dots having native ligands. For example, the capping ligands 120 may be added in excess to the reaction solution in which the quantum dots were formed. The capping ligands 120 may then bond to the surface of the quantum dots 100, replacing the native ligands. In another example embodiment, a solution including the quantum dots may be purified to remove excess native ligands from the solution. The purification process may include heating, stirring, waiting, and / or the like. For example, in an example embodiment, the quantum dots having native ligands may be admixed with a mixture including the desired capping ligands 120 in an appropriate temperature range for an appropriate amount of time. For example, in an - 13 - AttyDktNo: 074644 / 605937example embodiment, Copper Indium Disulfide / Zinc Sulfide quantum dots are admixed with a 1:1(v / v) mixture of mercaptoethanol and mercaptohexanol as capping ligands 120 within a temperature range of about 100 °C to 150 °C for from about 1 hour to about 24 hours to form the quantum dots 100 having capping ligands 120 of the species pair mercaptoethanol and mercaptohexanol.

[0063] At step 1006, a composition is formed by suspending the quantum dots 100 in a polar solvent or a polar polymer or polar polymeric material. For example, the quantum dots 100 and the polar solvent or polar polymer or polar polymeric material may be blended together via mixing while heated to or maintained at an appropriate temperature for blending of the composition for an appropriate amount of time. As should be understood by one of ordinary skill in the art, the appropriate temperature and appropriate amount of time may be determined based at least in part on the characteristics of the polar solvent, polar polymer, or polar polymeric material.

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

[0065] At step 1010, the blended material may be extruded to form an extrusion and / or an extruded product. In various embodiments, the extruded product has a quantum yield of greater than 1 percent, and an improved lifetime in comparison to quantum dots without the one or more selected capping ligands 120 upon the surface of the quantum dots. The extruded products may 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 merely intended to further illustrate the compositions, systems and methodologies described herein.

[0067] EXAMPLE 1

[0068] Copper Indium Disulfide / Zinc Sulfide (CuInS2 / ZnS) Quantum dots (available from Strem Chemicals, Inc. as Catalog # 29-8520 with a peak emission of 630 nm + / - 10 nm) were - 14 - AttyDktNo: 074644 / 605937admixed with a 1:1(v / v) mixture of mercaptoethanol and mercaptohexanol as capping ligands within a temperature range of about 100oC to 150oC for from about 1 hour to about 24 hours.

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

[0070] EXAMPLE 2

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

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

[0073] EXAMPLE 3

[0074] The quantum dots from example 1 were examined and found to have a mixture of mercaptoethanol and mercaptohexanol capping ligands upon the shell of the core / shell CuInS2 / ZnS quantum dots. These quantum dots were found to have solubility in polar solvents - 15 - AttyDktNo: 074644 / 605937such as dimethyl sulfoxide, methanol, isopropanol, varying ratios of ethanol / water and the various alcohols under different pH conditions. These particular quantum dots were found insoluble in solvents such as ethyl acetate, tetrahydrofuran, 1,4-dioxane, acetonitrile and acetone.

[0075] EXAMPLE 4

[0076] The initial quantum dots from example 1 were capped with only mercaptohexanol capping ligands and those quantum dots were encapsulated in PVOH as described below. Procedural Details: Material Quantity Notes E l 1 D 1 λ 2 PL Y 2%;1) 1.00 g of the quantum dots was dissolved in 20 mL EtOH (w / NH4OH) in a 40 mL vial. 2) In a separate 20 mL vial, PVOH, THF (seemed to assist PVOH solubility in H2O), and H2O were added and sonicated until a clear homogeneous solution formed. 3) The PVOH solution was transferred to a 250 mL round bottom flask and fitted with a stir bar. 4) Under stirring of the PVOH solution, the solution of the quantum dots in EtOH was added 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) before being heated to 70 °C and continued heating for 2 hours. 6) The resultant red colored clear solution was dried in vacuo @ 100 °C. 7) Drying resulted in the production of a red film-like material, which was broken into a fine powder using a spatula and utilized in a subsequent extrusion.

[0077] EXAMPLE 5 - 16 - AttyDktNo: 074644 / 605937

[0078] Using the PVOH encapsulated quantum dots prepared in example 4, the quantum dots were extruded in PVA as follows.

[0079] In an extruder, 18.4g of ethylene vinyl acetate (EVA) pellets and 1.2g of the quantum dots encapsulated with PVOH from Example 6 were extruded at 200 °C at 50 rpm. The resulted QD-EVA string was chopped to produce pellets of blended material. The pellets were hot pressed to form ~100 µm thick films for optical characterization. The resulted films showed factor of two improvement in photostability. Extrusion Details: Polymer Temp RPM PL QY Haze Est. QD loading Thickness (°C) peak (%) (%) i EVA

[0080] EXAMPLE 6

[0081] An additional experiment was carried out to explore if quantum dots capped with mercaptohexanol alone could be extruded within EVOH.

[0082] In an extruder, 18.4g of ethylene vinyl alcohol (EVOH, H171B grade, purchased from Kuraray America, Inc, 38 mol % Ethylene Vinyl-Alcohol Copolymer) pellets and 1.2g of quantum dots capped with MCH were extruded at 220 °C at 50, 150 and 250 rpm. The resulted QD-EVOH string was chopped to produce pellets of blended material. The pellets were hot pressed to form ~100 µm thick films for optical characterization. The optical properties are given in table below. The resulted films showed improved haze and photostability indicating better compatibility in EVOH. The resulted films showed improved photostability (Fig 6) indicating better compatibility in EVOH. POLYMER QD QY HAZE HAZE HAZE TYPE (%) @50 @150 @250 EVOH NATIVE 85 22 19 13 AttyDktNo: 074644 / 605937

[0083] EXAMPLE 7

[0084] An additional example was carried out to explore if quantum dots capped with mercaptoethanol alone could be extruded within EVOH.

[0085] In an extruder, 18.4g of ethylene vinyl alcohol (EVOH, F171B grade, purchased from Kuraray America, Inc, 32 mol % Ethylene Vinyl-Alcohol Copolymer) pellets and 1.2g of quantum dots capped with MCE were extruded at 220 °C at 50, 150 and 250 rpm. The resulted QD-EVOH string was chopped to produce pellets of blended material. The pellets were hot pressed to form ~100 µm thick films for optical characterization. The resulted films showed improved photostability (Figure 8) indicating better compatibility in EVOH.

[0086] EXAMPLE 8

[0087] An additional example was carried out to explore if quantum dots capped with mercaptopropionic acid alone could be extruded within EVOH.

[0088] In an extruder, 18.4g of ethylene vinyl alcohol (EVOH, F171B grade, purchased from Kuraray America, Inc, 32 mol % Ethylene Vinyl-Alcohol Copolymer) pellets and 1.2g of quantum dots capped with MPA were extruded at 220 °C at 50, 150 and 250 rpm. The resulted QD-EVOH string was chopped to produce pellets of blended material. The pellets were hot pressed to form ~100 µm thick films for optical characterization. The resulted films showed improved photostability (Figure 8) indicating better compatibility in EVOH.

[0089] EXAMPLE 9

[0090] An additional example was carried out to explore if quantum dots capped with 3- (trimethoxysilyl)-1-propanethiol (MPTMS) alone could be extruded within EVOH.

[0091] In an extruder, 18.4g of ethylene vinyl alcohol (EVOH, F171B grade, purchased from Kuraray America, Inc, 32 mol % Ethylene Vinyl-Alcohol Copolymer) pellets and 1.2g of quantum dots capped with MPTMS were extruded at 220 °C at 50, 150 and 250 rpm. The resulted QD-EVOH string was chopped to produce pellets of blended material. The pellets were hot pressed to form ~100 µm thick films for optical characterization. The resulted films showed improved photostability (Figure 8) indicating better compatibility in EVOH.

[0092] EXAMPLE 10 - 18 - AttyDktNo: 074644 / 605937

[0093] An additional example was carried out to explore if quantum dots capped with mixture of mercaptohexanol and mercaptopropionic acid could be extruded within EVOH.

[0094] In an extruder, 18.4g of ethylene vinyl alcohol (EVOH, F171B grade, purchased from Kuraray America, Inc, 32 mol % Ethylene Vinyl-Alcohol Copolymer) pellets and 1.2g of quantum dots capped with mixture MCH and MPA were extruded at 220 °C at 50, 150 and 250 rpm. The resulted QD-EVOH string was chopped to produce pellets of blended material. The pellets were hot pressed to form ~100 µm thick films for optical characterization. The resulted films showed improved photostability (Figure 9) indicating better compatibility in EVOH.

[0095] EXAMPLE 11

[0096] An additional example was carried out to explore if quantum dots capped with mixture of mercaptoethanol and mercaptopropionic acid could be extruded within EVOH.

[0097] In an extruder, 18.4g of ethylene vinyl alcohol (EVOH, F171B grade, purchased from Kuraray America, Inc, 32 mol % Ethylene Vinyl-Alcohol Copolymer) pellets and 1.2g of quantum dots capped with mixture MCE and MPA were extruded at 220 °C at 50, 150 and 250 rpm. The resulted QD-EVOH string was chopped to produce pellets of blended material. The pellets were hot pressed to form ~100 µm thick films for optical characterization. The resulted films showed improved photostability (Figure 9) indicating better compatibility in EVOH.

[0098] EXAMPLE 12

[0099] An additional example was carried out to explore if quantum dots capped with mixture of mercaptohaxanol and mercaptoethanol could be extruded within EVOH.

[0100] In an extruder, 18.4g of ethylene vinyl alcohol (EVOH, F171B grade, purchased from Kuraray America, Inc, 32 mol % Ethylene Vinyl-Alcohol Copolymer) pellets and 1.2g of quantum dots capped with mixture MCH and MCE were extruded at 220 °C at 50, 150 and 250 rpm. The resulted QD-EVOH string was chopped to produce pellets of blended material. The pellets were hot pressed to form ~100 µm thick films for optical characterization. The resulted films showed improved photostability (Figure 9) indicating better compatibility in EVOH.

[0101] EXAMPLE 13

[0102] Due to the similarities in the surface chemistry and optical properties of blue-emitting CuAlS2QDs, an additional example involves using CuAlS2 / ZnS QDs extruded within EVOH.

[0103] In an extruder, 20g of ethylene vinyl alcohol (EVOH, F171B grade, purchased from Kuraray America, Inc, 32 mol % Ethylene Vinyl-Alcohol Copolymer) pellets and 1g of - 19 - AttyDktNo: 074644 / 605937CuAlS2 / ZnS quantum dots capped with mixture MCH, MCE, or MPTMS are extruded at 220 °C at 50, 150 and 250 rpm. The resulted QD-EVOH string is chopped to produce pellets of blended material. The pellets are hot pressed to form ~100 µm thick films for optical characterization. The resulted films will show improved photostability (similar to Figure 9) indicating better compatibility and reliability in EVOH.

[0104] In an example embodiment, quantum dots are provided. The quantum dots include at least one inorganic material selected from the group consisting of CuFeSe2, CuFeS2, CuInZnS2, CuZnSnSe2, CuInS2, CuInSe2, CuInSexS2-x, CuInGaSexS2-x, AgInS2. AgInSe2, AgInGaSexS2-x, CuAlS2, CuAlSe2, CuAlGaSexS2-x, CdS, CdSe, ZnS and ZnSe; and at least one species of capping ligands upon a surface of the quantum dots whereby the quantum dots are characterized as having solubility in polar host environments. The at least one species of capping ligands comprises a mercapto group. The quantum dots are further characterized by exhibiting a photoluminescence upon excitation with a light source and the quantum dots exhibiting a quantum yield of greater than 30 percent.

[0105] In an example embodiment, the at least one species of capping ligands is at least a pair of species of capping ligands.

[0106] In an example embodiment, the at least a pair of species of capping ligands is selected from among the pairs of 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 thioglycolic acid, 3- (trimethoxysilyl)-1-propanethiol and mercaptohexanol, 3-(trimethoxysilyl)-1-propanethiol and mercaptoethanol, and 3-(trimethoxysilyl)-1-propanethiol and mercaptopropionic acid.

[0107] In an example embodiment, the at least a pair of species of capping ligands are selected from among the pairs of mercaptohexanol and mercaptoethanol, mercaptopropionic acid and mercaptoethanol, and mercaptopropionic acid and mercaptohexanol. - 20 - AttyDktNo: 074644 / 605937

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

[0109] In an example embodiment, a composition is provided. The composition includes a polar solvent; and one or more quantum dots having at least a pair of species of capping ligands upon the surface of the quantum dots whereby the quantum dots have solubility in the polar solvent. The composition is further characterized by the quantum dots exhibiting photoluminescence upon excitation with a light source and the quantum dots exhibiting a quantum yield of greater than 30 percent.

[0110] In an example embodiment, each species of the at least a pair of species of capping ligands comprises a mercapto group.

[0111] In an example embodiment, the at least a pair of species of capping ligands are selected from among the pairs of 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 example embodiment, the polar solvent is selected from the group consisting of ethanol, an ethanol / water mixture, isopropanol, an isopropanol / water mixture, methanol, a methanol / water mixture, dimethyl sulfoxide, diethyl sulfoxide, tetrahydrofuran, and a tetrahydrofuran / water mixture.

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

[0114] In an example embodiment, the quantum dots include at least one inorganic material selected from the group consisting of CuFeSe2, CuFeS2, CuInZnS2, CuZnSnSe2, CuInS2, - 21 - AttyDktNo: 074644 / 605937CuInSe2, CuInSexS2-x, CuInGaSexS2-x, AgInS2. AgInSe2, AgInGaSexS2-x, CuAlS2, CuAlSe2, CuAlGaSexS2-x, CdS, CdSe, ZnS and ZnSe.

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

[0116] In an example embodiment, a composition is provided. The composition includes a polar polymeric material; and one or more quantum dots having at least one species of capping ligands upon the surface of the quantum dots. The polar polymeric material encompasses the quantum dot whereby the composition is characterized by the quantum dots having dispersibility in the polar polymeric material. The composition is further characterized by the quantum dots exhibiting photoluminescence upon excitation with a light source and the quantum dots exhibiting a quantum yield of greater than 1 percent.

[0117] In an example embodiment, the at least one species of capping ligands comprises a mercapto group.

[0118] In an example embodiment, the at least one species of capping ligands 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 example embodiment, the at least one species of capping ligands comprises two or more species of capping ligands, and each species of ligand of the two or more species of capping ligands includes a mercapto group.

[0120] In an example embodiment, the at least one species of capping ligands is a pair of species of capping ligands selected from among the pairs of 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. - 22 - AttyDktNo: 074644 / 605937

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

[0122] In an example embodiment, the quantum dots include at least one inorganic material selected from the group consisting of CuFeSe2, CuFeS2, CuInZnS2, CuZnSnSe2, CuInS2, CuInSe2, CuInSexS2-x, CuInGaSexS2-x, AgInS2. AgInSe2, AgInGaSexS2-x, CuAlS2, CuAlSe2, CuAlGaSexS2-x, CdS, CdSe, ZnS and ZnSe.

[0123] In an example 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 should be regarded as limitations upon the scope of the invention. Various modifications, substitutions, combinations, and ranges of parameters may be made or utilized in the compositions, and methodologies described herein.

[0125] Many modifications and other embodiments of the disclosure set forth herein will come to mind to one skilled in the art to which this disclosure pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the claims are not to be 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 generic and descriptive sense only and not for purposes of limitation. - 23 - AttyDktNo: 074644 / 605937

Claims

THAT WHICH IS CLAIMED:

1. Quantum dots comprising: at least one inorganic material selected from the group consisting of CuFeSe2, CuFeS2, CuInZnS2, CuZnSnSe2, CuInS2, CuInSe2, CuInSexS2-x, CuInGaSexS2-x, AgInS2. AgInSe2, AgInGaSexS2-x, CuAlS2, CuAlSe2, CuAlGaSexS2-x, CdS, CdSe, ZnS and ZnSe; and at least one species of capping ligands upon a surface of the quantum dots whereby the quantum dots are characterized as having solubility in polar host environments, wherein the at least one species of capping ligands comprises a mercapto group, wherein the quantum dots are further characterized by exhibiting a photoluminescence upon excitation with a light source and the quantum dots exhibiting a quantum yield of greater than 30 percent.

2. The quantum dots of claim 1, wherein the at least one species of capping ligands is at least a pair of species of capping ligands.

3. The quantum dots of claim 2, wherein the at least a pair of species of capping ligands is selected from among the pairs of 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 thioglycolic acid, 3- (trimethoxysilyl)-1-propanethiol and mercaptohexanol, 3-(trimethoxysilyl)-1-propanethiol and mercaptoethanol, and 3-(trimethoxysilyl)-1-propanethiol and mercaptopropionic acid.

4. The quantum dots of claim 2, wherein the at least a pair of species of capping ligands are selected from among the pairs of mercaptohexanol and mercaptoethanol, mercaptopropionic acid and mercaptoethanol, and mercaptopropionic acid and mercaptohexanol. - 24 - AttyDktNo: 074644 / 6059375. The quantum dots of claim 1, wherein the at least one species of capping ligand is selected from among 3-(trimethoxysilyl)-1-propanethiol, mercaptohexanol, mercaptoethanol, and mercaptopropionic acid.

6. A composition comprising: a polar solvent; and one or more quantum dots having at least a pair of species of capping ligands upon the surface of the quantum dots whereby the quantum dots have solubility in the polar solvent, the composition further characterized by the quantum dots exhibiting photoluminescence upon excitation with a light source and the quantum dots exhibiting a quantum yield of greater than 30 percent.

7. The composition of claim 6, wherein each species of the at least a pair of species of capping ligands comprises a mercapto group.

8. The composition of claim 6, wherein the at least a pair of species of capping ligands are selected from among the pairs of 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 of claim 6, wherein the polar solvent is selected from the group consisting of ethanol, an ethanol / water mixture, isopropanol, an isopropanol / water mixture, - 25 - AttyDktNo: 074644 / 605937methanol, a methanol / water mixture, dimethyl sulfoxide, diethyl sulfoxide, tetrahydrofuran, and a tetrahydrofuran / water mixture.

10. The composition of claim 6 wherein the polar solvent is an ethanol / water mixture that includes a ratio of ethanol to water of about 4 to 1.

11. The composition of claim 6, wherein the quantum dots include 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.

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

13. A composition comprising: a polar polymeric material; and one or more quantum dots having a capping ligand upon the surface of the quantum dots, wherein the polar polymeric material encompasses the quantum dot whereby the composition is characterized by the quantum dots have dispersibility in the polar polymeric material, the composition further characterized by the quantum dots exhibiting photoluminescence upon excitation with a light source and the quantum dots exhibiting a quantum yield of greater than 1 percent.

14. The composition of claim 13, wherein the capping ligand comprises a mercapto group.

15. The composition of 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. - 26 - AttyDktNo: 074644 / 60593716. The composition of claim 13, wherein the capping ligand comprises two or more species of capping ligands, and each species of ligand of the two or more species of capping ligands includes a mercapto group.

17. The composition of claim 13, wherein the capping ligand is a pair of species of capping ligands selected from among the pairs of 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 of claim 13 wherein the polar polymeric material is selected from the group consisting of poly vinyl alcohol, an ethylene vinyl alcohol copolymer, polyvinyl acetate, ethylene vinyl acetate, polyurethane, polyamides, and an acrylic polymer.

19. The composition of claim 15 wherein the quantum dots include 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.

20. The composition of claim 15, wherein the composition is extruded into an extruded product. - 27 - AttyDktNo: 074644 / 605937

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