Abstract: A fluorescent liquid penetrant is provided which includes a liquid medium having a plurality of fluorophores disposed therein. Upon excitation with a suitable light source, the penetrant exhibits a quantum yield greater than 40% (or in some embodiments, greater than 90%). In some embodiments, the fluorophore is a low-toxicity quantum dot. In some embodiments, the fluorophore has significantly reduced self-absorption, which allows for surface discontinuity depth measurement. Also disclosed are apparatuses for using these fluorescent liquid penetrants for non-destructive testing purposes. In some embodiments, these tests include measuring the depth of a discontinuity by analyzing photoluminescence intensity and/or photoluminescence peak position shift.

Abstract: Disclosed herein are embodiments of a composition comprising a polymer or sol-gel matrix and one or more nanocrystals. The composition is useful for making various products, including a luminescent solar concentrator. The nanocrystals are dispersed in the polymer or sol-gel matrix to reduce or substantially prevent nanocrystal-to-nanocrystal energy transfer and a subsequent reduction in the emission efficiency of the composition. The nanocrystals may comprise an antenna portion and an emitter portion, and in some embodiments the materials for the antenna and emitter portions are selected to produce a large Stokes shift between the absorption and emission wavelengths. In some embodiments, the polymer matrix comprises an acrylate polymer. Also disclosed herein is a method for making the composition, which may comprise a pre-polymerization step before the nanocrystals are introduced. Devices comprising the composition and a photovoltaic cell also are disclosed. In some examples, the device is a window.

Abstract: A method is provided for verifying the authenticity of an article which bears a security mark. The method includes irradiating the security mark with a time-varying light source, ascertaining at least one portion of the emissions spectrum of the irradiated security mark with at least one photodetector, determining the photoluminescence lifetime of the security mark by monitoring the time or frequency response of the photodetector, and verifying the authenticity of the article only if the security mark exhibits a photoluminescence which has a lifetime that falls within the range of appropriate values for each portion of the photoluminescence spectrum for which the photoluminescence lifetime of said security mark was ascertained.

Abstract: A security ink is provided which includes a liquid medium having a plurality of quantum dots disposed therein. Upon excitation with a suitable light source, the ink exhibits a quantum yield greater than 30%, and a photoluminescence which has a lifetime of more than 40 nanoseconds and which varies by at least 5% across the emission spectrum of the quantum dots. Also disclosed are apparatuses for using the same for anti-counterfeit or authentication purposes, which uniquely identifying the presence of photoluminescent materials by spectrally resolving their photoluminescence lifetime.

Abstract: Disclosed herein are embodiments of a composition comprising a polymer or sol-gel and one or more nanocrystals. The composition is useful as a luminescent solar concentrator. The nanocrystals are dispersed in the polymer or sol-gel matrix so as to reduce or substantially prevent nanocrystal-to-nanocrystal energy transfer and a subsequent reduction in the emission efficiency of the composition. In some embodiments, the polymer matrix comprises an acrylate polymer. Also disclosed herein is a method for making the composition. Devices comprising the composition are disclosed. In some cases the polymer is the waveguide, in others the polymer is applied as a coating on a waveguide. In some examples, the device is a window.

Abstract: A security ink is provided which includes a liquid medium having a plurality of quantum dots disposed therein. Upon excitation with a suitable light source, the ink exhibits a quantum yield greater than 30%, and a photoluminescence which has a lifetime of more than 40 nanoseconds and which varies by at least 5% across the emission spectrum of the quantum dots. Also disclosed are apparatuses for using the same for anti-counterfeit or authentication purposes, which uniquely identifying the presence of photoluminescent materials by spectrally resolving their photoluminescence lifetime.

Abstract: Embodiments of photoanodes and quantum dot-sensitized solar cells (QDSSCs) comprising colloidal, cation-exchanged quantum dots are disclosed. The quantum dots include a core and an outer cation-exchanged layer having a cation composition that differs from a cation composition of the core. Methods of making the quantum dots, photoanodes, and QDSSCs also are disclosed.

Abstract: Common approaches to synthesizing alloyed quantum dots employ high-cost, air-sensitive phosphine complexes as the selenium precursor. Disclosed quantum dot synthesis embodiments avoid these hazardous and air-sensitive selenium precursors. Certain embodiments utilize a combination comprising a thiol and an amine that together reduce and complex the elemental selenium to form a highly reactive selenium precursor at room temperature. The same combination of thiol and amine acts as the reaction solvent, stabilizing ligand, and sulfur source in the synthesis of quantum dot cores. A non-injection approach may also be used. The optical properties of the quantum dots synthesized by this new approach can be finely tuned for a variety of applications by controlling size and/or composition of size and composition. Further, using the same approach, a shell can be grown around a quantum dot core that improves stability, luminescence efficiency, and may reduce toxicity.

Abstract: Common approaches to retroreflectors rely on absorptive materials that waste light energy that could be utilized for visibility. Disclosed photoluminescent retroreflectors filter reflected light, like traditional colored retroreflectors, but down-convert photons of the wrong color into a glow visible from more directions. The glow enables visibility for more observers or observers whose light source is far from their line of sight. The color of the glow can be adjusted by choice of luminescent material as a design feature or safety purpose. Certain embodiments utilize photoluminescent additives within a retroreflector while other embodiments utilize a photoluminescent coating on top of a pre-made retroreflector. An exemplary photoluminescent material for these optical devices is CuInZnS2 quantum dots.

Abstract: Embodiments of linkers for binding semiconductor quantum dots (QDs) to metal oxides are disclosed. The linkers have a general formula F1-A-(F2)z wherein F1 is —COOH, —COO?, —PO3H2, —PO3H?, —B(OH)2, —BO2H?, —SO3H, —SO3?, —NH2, —SH, or —S?; A is aryl, heteroaryl, aliphatic, or heteroaliphatic; and z?1 and each F2 independently is —PO3H2, —PO3H?, —B(OH)2, —BO2H?, —SO3H, —SO3?, or z?2 and each F2 independently is —COOH, —COO?, —PO3H2, —PO3H?, —B(OH)2, —BO2H?, —SO3H, or —SO3?, or z?2 and (F2)z collectively is an oxysilane moiety comprising z lower alkoxy groups bound to silicon. Methods of binding QDs to metal oxides with the disclosed linkers also are disclosed, as well as devices including the QD-functionalized metal oxides.