Enhancement of photochromic properties of MoO3 and WO3 by plasma treatment of sols

Abstract

Molybdenum (MoO3) and tungsten (WO3) oxides have pronounced photo- and electrochromicproperties due to reversible reduction to the +5 oxidation state. These properties manifest themselvesdepending on the size and structure of the material. By changing the structure of nanoparticles, onecan control the transition rate (lifetime of the reduced state). One of the ways to change the structureis doping or the creation of mixed materials (binary, ternary, etc. oxides), which is successfullyproduced by the action of electric discharges burning in the liquid phase volume. Studies on the effectof an underwater diaphragm discharge of alternating current on molybdenum and tungsten oxidesols stabilized with polyvinylpyrrolidone with different molecular weights have been carried out.Transmission electron microscopy data showed that the action of a diaphragm discharge led to theformation of binary structures based on MoO3–x/WO3–x, the size of which depends on the molecularweight of the stabilizer. Plasma treatment enhances the effect of photocoloring due to transitionsbetween multilevel multivalent states of tungsten and molybdenum, accelerates the discolorationprocess due to the formation of hydrogen peroxide under the action of an electric discharge,and increases the number of cycles of reversibility of photochromism due to the modificationof the polymer stabilizer and the creation of conditions for retaining the oxygen bridge in theoctahedral structure of oxides. Obtained results are the basis for creating composites based on polymersand photochromic materials that can be used in modern architectural structures or the automotiveindustry.