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We present a new colloidal synthesis of gallium-doped zinc oxide nanocrystals that are transparent in the visible and absorb in the near-infrared. Thermal decomposition of zinc stearate and gallium nitrate after hot injection of the precursors in a mixture of organic amines leads to nanocrystals with tunable properties according to gallium amount. Substitutional Ga(3+) ions trigger a plasmonic resonance in the infrared region resulting from an increase in the free electrons concentration. These nanocrystals can be deposited by spin coating, drop casting, and spray coating resulting in homogeneous and high-quality thin films. The optical transmission of the Ga-ZnO nanoparticle assemblies in the visible is greater than 90%, and at the same time, the near-infrared absorption of the nanocrystals is maintained in the films as well. Several strategies to improve the films electrical and optical properties have been presented, such as UV treatments to remove the organic compounds responsible for the observed interparticle resistance and reducing atmosphere treatments on both colloidal solutions and thin films to increase the free carriers concentration, enhancing electrical conductivity and infrared absorption. The electrical resistance of the nanoparticle assemblies is about 30 kΩ/sq for the as-deposited, UV-exposed films, and it drops down to 300 Ω/sq after annealing in forming gas at 450 °C, comparable with state of the art tin-doped indium oxide coatings deposited from nanocrystal inks.

Abstract. Sol-gel derived films can be deposited on metals to improve their resistance to oxidation and corrosion or to modify their surface properties. However, practical applications are limited by problems intrinsic to sol-gel processing or specific of coating/metal systems.Coatings aimed to improve oxidation and wet corrosion resistance have been the most studied. The results published in the literature Show that sol-gel coatings may offer good protection against oxidation. More difficult is to achieve a protection against wet corrosion.An important aspect of the application of the sol-gel method for coating metallic objects is also the deposition technique.

Hybrid organic-inorganic materials have been obtained by cohydrolysis of (3-glycidoxypropyl)trimethoxysilane (GPTMS) and tetraethyl orthosilicate (TEOS) in acidic conditions. Boron trifluoride diethyl etherate (BF 3 OEt 2 ) has been used to catalyze the epoxide polymerization. The effect of BF 3 OEt 2 has been studied by multinuclear magnetic resonance (NMR) in the precursor sol and by Fourier transform infrared spectroscopy in the final material. The addition of BF 3 OEt 2 to a prereacted sol of GPTMS and TEOS has allowed the epoxide ring opening at room temperature, without formation of diol units or boric acid precipitation in the final material. The prereaction time of GPTMS with TEOS has been found to be an important parameter. The catalytic effect of BF 3 OEt 2 with respect to other commonly used catalysts in sol-gel processing of GPTMS-based hybrid organic-inorganic materials, such as zirconium butoxide and 1-methylimidazole, has been studied.

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