Synthesis of photochromic nanoparticles and determination of the mechanism of photochromism

Abstract

Photochromic nanoparticles of zinc-silicon oxide were synthesized using plasma enhanced chemical vapor deposition. These particles turned black upon irradiating with ultraviolet light. We investigated this phenomenon using density functional theory calculations. Silicon inclusions create trap levels and oxygen defects that reduce the ionization potential of ZnO. This forms a quantum potential between ZnO and zinc-silicon oxide, and the excited electron is stable. Because oxygen defects also increase the bond overlap population between the zinc atoms in a ZnO crystal, they introduce further defects and help in the formation of quantum potentials. Growth of a perfect crystal of ZnO prevents the formation of oxygen defects, which is not desirable for photochromism.

Recovery of W–Mo Alloy Scrap and the Photochromic Properties of WO3/MoO3 Composite Products

“…These electrons are subsequently captured by WO 3 and MoO 3 , forming W 5+ and Mo 5+ , while H + ions from the surrounding air or the sample’s surface are incorporated into WO 3 and MoO 3 , , resulting in the generation of H x WO 3 and H x MoO 3 , accompanied by the reduction of W 5+ and Mo 5+ . The blue coloration of the sample stems from the electron’s transition within the valence band. , WO 3 false( MoO 3 false) + hv → WO 3 * false( MoO 3 * false) + normalh + + normale − .25ex2ex normalW 6 + false( Mo 6 + false) + normale − → normalW 5 + false( Mo 5 + false) .25ex2ex normalH 2 O + normalh + → normalH + + normalO 2 .25ex2ex WO 3 false( MoO 3 false) + x e − + x h + → normalH x WO 3 false( H…”

“…These electrons are subsequently captured by WO 3 and MoO 3 , forming W 5+ and Mo 5+ , while H + ions from the surrounding air or the sample’s surface are incorporated into WO 3 and MoO 3 , , resulting in the generation of H x WO 3 and H x MoO 3 , accompanied by the reduction of W 5+ and Mo 5+ . The blue coloration of the sample stems from the electron’s transition within the valence band. , …”

UV Photochromism in Transition Metal Oxides and Hybrid Materials

“…Zinc‐silicon oxide (ZnSiO) synthesized using chemical vapor deposition exhibits UV photochromism which converts the color of the film to blackish and is thermally reversible by exposure to heat (30 min). [ 227 ] The photochromic response is attributed to charge transfer and injection efficiency created by the trap levels and oxygen defects that reduce the ionization potential of ZnO. This forms a quantum potential between ZnO and ZnSiO, and the excited electron is stable.…”

Fabrication of solid-state secondary battery using semiconductors and evaluation of its charge/discharge characteristics

“…[21][22][23] In recent years, studies on the use of photochromism utilizing the accumulation of carriers at the trap levels of semiconductors have been performed. 24,25) Furthermore, there have been some reports on the use of batteries using the trap levels of oxide semiconductors. [26][27][28][29] A device of particular interest is the Guera battery, which accumulates carriers at the trap levels of oxide semiconductors formed by UV irradiation.…”