Abstract: An optical element is provided which comprises a plurality of fluorophores disposed in a medium. The fluorophores have a quantum yield greater than 50% and an absorption spectrum with a maximum intensity at wavelengths less than 400 nm, and emit a spectrum of light having a maximum intensity at wavelengths within the range of 400 nm to 1200 nm. The optical element is at least partially transparent over the visible region of the spectrum. The optical element is especially useful as a window or other optical component of a greenhouse structure.

Abstract: The present disclosure relates generally to nanoparticle formulations, and more specifically to nanoparticle and ligands used for imparting low-pH solubility in a range of solvents, including photoluminescent materials such as quantum dots.

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 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: 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: 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: 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.