Cd1−xZnxS nanoparticles with different compositions (0⩽x⩽1) embedded in silica matrix were prepared in thin film form by the sol–gel technique. The film texture and structural transformation with increasing x value were studied from transmission electron micrographs and electron diffraction patterns. Optical study indicated increase in optical bandgap and decrease in refractive index with increasing zinc content (x value). Photoluminescence studies showed emission from surface states with emission energy blue shifted with increasing zinc content in the films. Annealing behaviour of the films with increasing annealing temperature and time was studied.

The combustion, oxidation, and pyrolysis chemistry of even simple light hydrocarbons can be extremely complex, involving hundreds or thousands of kinetically significant species. Even relatively minor species can play an important role in the formation of undesirable emissions and byproducts, and their properties and reactions need to be modeled in some detail in order to make accurate predictions. In many technologically important applications, the reaction chemistry is closely coupled with the mixing and heat flow, dramatically increasing the computational difficulty. The most reasonable way to deal with this complexity is to use a computer not only to solve the simulation numerically, but also to construct the model in the first place. We are developing the methods needed to make this sort of computer-aided kinetic modeling feasible for real systems. The computer is used to calculate most of the molecular properties and rate parameters in the model by a variety of quantum- and group-additivity-based techniques. We summarize our new computer methods for modeling the pressure dependence (falloff and chemical activation) of gas-phase reactions. Our approach to determining the optimal reduced kinetic models for various reaction conditions is discussed. Adaptive-chemistry methods that allow one to solve detailed macroscopic reacting flow simulations involving hundreds of species are outlined.

Synthesis and characterization of undoped and Mn 2+ doped ZnS nanocrystallites (radius 2-3 nm) embedded in a partially densified silica gel matrix are presented. Optical transmittance, photoluminescence (PL), ellipsometric and electron spin resonance measurements revealed manifestation of quantum size effect. PL spectra recorded at room temperature revealed broad blue emission signal centred at ~ 420 nm and Mn 2+ related yellow-orange band centred at ~ 590 nm while ESR indicated that Mn in ZnS was present as dispersed impurity rather than Mn cluster.

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