Indium tin oxide (ITO) is a semiconductor that is highly transparent to the visible light wavelengths, electrically conductive at room temperature, resistant to high temperatures, and easily deposited as a thin film. These properties of ITO have led to its wide use in applications requiring a transparent, conductive coating, including LCD and touch screens, window de-icing coatings, and smart windows. Researchers are increasingly synthesizing ITO nanoparticles to deposit into ITO films, since the electrical and optical properties of ITO nanoparticles can be tuned with nanoparticle size and the amount of tin dopant. This study attempted to elucidate the effect of tin dopant concentration and adsorbed organic ligand on two environmentally relevant nanoparticle characteristics: aggregation rate and optical band gap. Uncapped commercial samples with SnO2:I2O3 ratios of 0, 5, and 10% by mass were purchased from mknano (Mississauga, ONT) and used either as-received (no ligand) or introduced to a solution of organic ligand, including natural organic matter (NOM). Aqueous stability and aggregation kinetics of particles were determined in various electrolyte solutions with time-resolved dynamic light scattering, and optical band architecture determined through UV-Vis spectroscopy and ultraviolet photoelectron spectroscopy. The characteristics of organic ligand and tin dopant level both affected aggregation kinetics and apparent band gap of these nanoparticles. In the absence of organic ligands, the aqueous stability decreased with increasing tin dopant concentration, but the apparent band gap increased. This trend was confirmed with a different set of ITO nanoparticles synthesized in the Milliron group at the University of Texas and capped with poly(acrylic acid)-poly(ethylene oxide) random block copolymer. These results indicate that the level of tin and organic ligand both affect the fate and transport of ITO nanoparticles in the environment and the possibility to produce reactive oxygen species when illuminated with UV light.

Effect of organic ligands and tin dopant concentration on apparent band gap and aggregation of indium tin oxide nanoparticles in aqueous systems

254th National Meeting (2017)

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