Optical and structural changes of silver nanoparticles during photochromic transformation

Abstract

Silver nanoparticles embedded in titanium oxide change their color upon irradiation with visible light. Here we investigate the origin of this photochromic effect. The color change is found to result chiefly from a reduction of the optical extinction peak of the photoexcited particle plasmons. From a comparison with x-ray diffraction experiments, we conclude that this reduction is caused by a photoinduced decrease of the mean size of the silver nanocrystals.

Photocatalytic Activity of Vis-Responsive Ag-Nanoparticles/TiO2 Composite Thin Films Fabricated by Molecular Precursor Method (MPM)

“…Although the synthesis of Ag/TiO 2 heterostructures was intensively reported in large quantities [8][9][10][11][12][13][14]23,24], there are few reports about Ag/TiO 2 composite thin films with amounts of Ag > 18 mol%, prepared by chemical methods such as sol-gel, so far in the literatures. It is well reported that incorporating larger amount of Ag particles was limited by the sol-gel dip-coating method of up to 18 mol% due to Ag particles coalescing with each other into huge particles during sintering [25].…”

“…The early methods [17][18][19], to produce noble-metal nanoparticles are still used today and continue to be the standard by which other synthesis methods are compared [20][21][22]. In particular, silver as a noble metal has attracted considerable attention, as a result of its remarkable role in the improvement of the photo-activity of semiconductors [9,13,23]. They could be reused, and handled more easily and economically if impregnated on substrates.…”

“…They could be reused, and handled more easily and economically if impregnated on substrates. Therefore, many researchers have focused on modifying TiO 2 with Ag by synthesis Ag/TiO 2 heterostructures [8][9][10][11][12][13][14]23,24].…”

“…These noble metals act separately or simultaneously depending on the photoreaction conditions, experimental methods used and they may (i) enhance the electron-hole separation by acting as electron traps [8][9][10][11], (ii) extend the light absorption into the visible range and enhance surface electron excitation by sizeand shape-dependent plasmon resonances excited by visible light [7,[12][13][14] and/or (iii) modify the surface properties of TiO 2 [15,16]. The early methods [17][18][19], to produce noble-metal nanoparticles are still used today and continue to be the standard by which other synthesis methods are compared [20][21][22].…”

Contrôle optique de la croissance et de la déformation de nanoparticules métalliques au sein de matrices mésoporeuses de TiO2

“…L'argent s'avère quant à lui être le métal noble le plus favorable à l'obtention de couleurs variées. Différents travaux rapportent un comportement photochromique avec des particules d'argent réduites au sein de matrices poreuses de TiO 2 de manière photocatalytique [5,[7][8][9][10], chimique [11,12] ou thermique [12,13] tout autant qu'avec des particules d'argent déposées par pulvérisation magnétron [14,15] ou par voie électrochimique [10]. On trouve des matrices poreuses préparées à partir de NPs de TiO 2 commerciales cristallisées dans la phase anatase [5,7,8,10] ou bien élaborées par voie sol-gel sous forme de films mésoporeux de TiO 2 amorphe [9,[11][12][13].…”