As a continuation of our effort to understand degradation mechanisms of a eutectic mixture of bis(2,2-dinitropropyl)acetal (BDNPA) and bis(2,2dinitropropyl)formal (BDNPF) (referred to as NP) under various environmental conditions, we investigated the thermal stability of NP under water and 74% relative humidity (RH) environments at temperatures below 70 °C. Based on a comprehensive characterization of samples aged over a period of two years, we conclude that in the presence of water the reaction pathways of the NP degradation are different from those observed in air or under nitrogen atmosphere. We found that the physical state of water molecules plays an important role as it determines the ability of oxygen to participate in the NP aging process. Based on the results obtained in Parts A and B of these studies, we conclude that the rate of NP degradation increases in the order: nitrogen < water < air < water vapor + air.

The aging behavior of a eutectic mixture of bis (2,2-dinitropropyl) acetal and formal [called NP here] has been studied in various atmospheres [dry (air or nitrogen) versus wet] at temperatures 70°C and below. The properties of aged samples were analyzed using Fourier transform infrared (FTIR) spectroscopy, Karl Fischer (KF) titration, liquid chromatography/mass spectrometry (LC/MS), and thermogravimetric analysis (TGA) over a period of three years. The results indicate that at aging temperatures up to 55°C, the initial rates of water production from nitrous acid (HONO) formation and decomposition into the water, NO, and NO 2 follows a 1 st order rate law and the rate constants follow an Arrhenius law as a function of temperature. The activation energies and pre-factors for water and volatiles production yield a single linear kinetic compensation plot, suggesting a common degradation pathway between NP and the various combinations of its constituents. Within a narrow temperature range, around 55°C, a trace amount of water in NP stabilizes its properties by preventing HONO elimination. When the aging temperature is substantially higher than 55°C, the nature of the degradation mechanism changes. It is suspected that the degradation products of NO x , water, and HNO 3 serve as catalysts to auto-catalyze (kinetics beyond the 1 st order) and further degrade NP. The effect of headspace volume on this auto-catalytic process will be discussed.

Narrow dispersity organically modified silica nanoparticles (SiNPs), diameter ~30 nm, entrapping a hydrophobic two-photon absorbing fluorenyl dye, were synthesized by hydrolysis of triethoxyvinylsilane and (3-aminopropyl)triethoxysilane in the nonpolar core of Aerosol-OT micelles. The surface of the SiNPs were functionalized with folic acid, to specifically deliver the probe to folate receptor (FR) over-expressing Hela cells, making these folate two-photon dye-doped SiNPs potential candidates as probes for two-photon fluorescence microscopy (2PFM) bioimaging. In vitro studies using FR over-expressing Hela cells and low FR expressing MG63 cells demonstrated specific cellular uptake of the functionalized nanoparticles. One-photon fluorescence microscopy (1PFM) imaging, 2PFM imaging, and two-photon fluorescence lifetime microscopy (2P-FLIM) imaging of Hela cells incubated with folate-modified two-photon dye-doped SiNPs were demonstrated.

Efficient, stable, and narrowband red-emitting fluorophores are needed as down-conversion materials for next-generation solid-state lighting that is both efficient and of high color quality. Semiconductor quantum dots (QDs) are nearly ideal color-shifting phosphors, but solution-phase efficiencies have not traditionally extended to the solid-state, with losses from both intrinsic and environmental effects. Here, we assess the impacts of temperature and flux on QD phosphor performance. By controlling QD core/shell structure, we realize near-unity down-conversion efficiency and enhanced operational stability. Furthermore, we show that a simple modification of the phosphor-coated light-emitting diode device-incorporation of a thin spacer layer-can afford reduced thermal or photon-flux quenching at high driving currents (>200 mA).