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Figure 13. Typical spectral radiant flux obtained using the PLN technology. This light source was a neutral white color. Figure 12. Through a judicious choice of nanofiber properties and luminescent particle coatings, virtually any point on the chromaticity axis can be produced. In this example, a blue (450 nm) LED is used to pump green and red PLNs to produce various colors. Figure 2. SEM images of (A) smooth PMMA nanofibers and (B) porous PMMA nanofibers produced through electrospinning.A BAs the solution flows to the electrode, the high electric field deforms each drop of the polymer solution into a conical shape known as a Taylor cone. Above a threshold limit, the electrical forces overcome the surface tension of the solution, and a fine, charged jet is ejected from the electrode and ultimately deposits nanofibers on a grounded substrate.In SSL applications, we have found that nanofiber mats serve the following functions:Provide optical filtering of the pump radiation ElectrospinningPolymer nanofibers are macro-sized objects with nanoscale features. The length (>> microns) of the nanofibers imparts macro-scale properties, while their diameter (50 nm-500 nm) imparts nanomaterial behavior. In addition, other nanoscale features such as surface pores or nanoparticles (e.g., luminescent quantum dots [QDs]) can be incorporated into the nanofiber to provide special physical and optical properties.Nanofibers are typically formed using the process of electro spinning, which involves applying a high voltage to an electrode in contact with a reservoir of polymer solution. The quantum dots used in the spray coating solution have the following properties:The QD consists of a semiconducting CdSe core that absorbs short wavelengths and emits longer • wavelengths. The emission color depends on the size of this core.A ZnS shell surrounds the core and provides environmental stability. • A long-chain amine coordination sphere is attached to the ZnS shell to provide compatibility • with various solvents and polymers. AbstractPhotoluminescent nanofibers (PLNs) can be formed by combining electrospun polymeric nanofibers and luminescent particles such as quantum dots (QDs). The physical properties of PLNs are dependent upon many different nanoscale parameters associated with the nanofiber, the luminescent particles, and their interactions. By understanding and manipulating these properties, the performance of the resulting optical structure can be tailored for desired end-use applications. For example, the quantum efficiency of QDs in the PLN structure depends upon multiple parameters including QD chemistry, the method of forming the PLN nanocomposites, and preventing agglomeration of the QD particles. This is especially important in solution-based electrospinning environments where some common solvents may have a detrimental effect on the performance of the PLN. With the proper control of these parameters, high quantum efficiencies can be readily obtained for PLNs. Achieving high quantum efficiencies is critical in applicatio...

Methyl esters of Kemp's tri-acid and cyclohexanetricarboxylic acid are structurally similar to acrylate polymers, having the same functionalities and stereoregularities as poly(methylmethacrylate) and poly(methylacrylate), respectively. The photochemistry and free radicals from these model systems have been studied using time-resolved electron paramagnetic resonance spectroscopy with laser flash photolysis at 248 nm. Chemically induced electron spin polarization from the triplet mechanism (net emission) is observed. Well-resolved spectra are obtained at all temperatures for the model system radicals, which are determined to be in the slow motion condition, that is, there is no interconversion of chair conformations. The temperature dependence of the spectra is minimal; some hyperfine lines shift as the temperature increases, but without much broadening. Density functional theory calculations are presented and discussed in support of the experimental data.