We report a one-step route for the synthesis of Au@TiO2, Au@ZrO2, Ag@TiO2, and Ag@ZrO2 particles in nanometer dimensions, with controllable shell thickness. This scalable procedure leads to stable and freely dispersible particles, and bulk nanocomposite materials have been made this way. The procedure leads to particles of various morphologies, with a crystalline core in the size range of 30−60 nm diameter and an amorphous shell of ∼3 nm thickness in a typical synthesis. The core diameter and shell thickness (in the range of 1−10 nm) can be varied, leading to different absorption maxima. The material has been characterized with microscopic, diffraction, and spectroscopic techniques. The metal particle growth occurs by the carbamic acid reduction route followed by hydrolysis of the metal oxide precursor, resulting in the oxide cover. The particles could be precipitated and redispersed. The shell, upon thermal treatment, gets converted to crystalline oxides. Cyclic voltammetric studies confirm the core−shell structure. The E 1/2 value is 0.250 V (ΔE ≈ 180 mV) for the quasi-reversible Ag m /Ag m + couple and 0.320 V (ΔE ≈ 100 mV) for the Au n /Au n + couple for Ag and Au particles, respectively. Adsorption on the oxide surface blocks electron transfer partially. Nonlinear optical measurements in solutions show that these materials are strong optical limiters with a high laser damage threshold.

Among the several phases of vanadium oxide, mixed phases of VO2 and V2O5 are preferred for uncooled micro-bolometers with low noise. The aim of this investigation is to achieve mixed phase VO2 and V2O5 thin films with nanometre grain sizes and high temperature coefficient of resistance (TCR). Since the phase depends upon the oxygen reactivity, these vanadium oxide thin films are prepared by reactive electron beam evaporation at different oxygen flow rates and substrate temperatures. The mixed phases have been evaluated through x-ray diffraction and x-ray photo emission studies. The temperature dependence of resistance has shown that the films grown at 473 K with 2.8 × 10−5 mbar chamber pressure of oxygen (VO2 : V2O5 ratio of 36 : 64) have the highest TCR of −3.2 K−1 with a reasonable low resistance (120 Ω/square).

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