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Correlations between crystallite/particle size and the luminescent characteristics of submicrometer phosphors were investigated. Spray pyrolyzed europium doped yttrium oxide (Y2O3:Eu3+) particles were selected as a model material. Crystallite size and the particle size were controlled independently. The morphology and crystallite structure were characterized by field-emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, and selected area electron diffraction. Photoluminescence (PL) properties were examined by spectrofluorophotometry and an absolute PL quantum efficiency (QE) measurement system. Chemical analyses and elemental mapping were conducted by Fourier transform infrared spectrophotometry and STEM equipped with energy dispersive spectroscopy, respectively. The results revealed that the PL properties were strongly dependent on crystallite size, particle size, surface chemistry, and the distribution of europium inside the phosphor particles. The PL intensities and QE increased with increasing crystallite size and particle size. The effect of crystallite size on PL properties played a more important role than that of particle size.

The goal of this work was to develop a simple technique for sizing colloidal particles by means of electrospray and aerosol techniques. Size distribution of different types of colloids (oxides, metals, and polymers) such as silica, gold, palladium, and polystyrene latex particles, with different nominal sizes below 100 nm was determined online. Nanometer-sized particles were dispersed into the gas phase as an aerosol via electrosprays operating in the cone-jet mode of a colloidal solution followed by a charge reduction of the sprayed droplets to unity and subsequent evaporation of the solvent. The size distribution of the generated aerosol particles was then determined by a differential mobility analyzer combined with a condensation nucleus/particle counter. For comparison, particle sizes were determined by electron microscopy (EM) using the samples which were obtained by (i) naturally dried sols and (ii) on-line deposited on a substrate during electrospraying. The proposed technique is capable of detecting the degree of dispersity of all colloid samples, and the measured values were comparable to results obtained by EM and dynamic light scattering. The results clearly show that the method described here constitutes a convenient, reliable, and rapid tool for the size determination of colloidal nanoparticles.

Controllability of particle size,chemical composition, and crystallinity are offered by the simple, general method for the synthesis of nanoparticles described here. A modified aerosol decomposition process is utilized in which salts are added to separate the nanocrystallites, resulting in nanoparticles of narrow size distribution (see Figure) and superior properties.

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The influence of operating parameters on the morphology of particles prepared by spray pyrolysis was investigated using a temperature-graded laminar flow aerosol reactor. Experimentally, zirconia particles were prepared by spray pyrolysis using an aqueous solution of zirconyl hydroxide chloride. Hollow particles were formed if the reactor temperature was high, the temperature gradient was too large, the flow rate of carrier gas was high, and the initial solute concentration was low. A numerical simulation of the pyrolysis process was developed using a combination of two previous models. The simulation results compared well with the experimental results.