Chemical Growth and Photochromism of Silver Nanoparticles into a Mesoporous Titania Template

Abstract

Elaboration of mesoporous titanium oxide film supporting silver nanoparticles is described. Mesoporous titanium oxide films are characterized by TEM analysis. Titania films are infiltrated with a silver salt solution and chemical reduction treatments are performed using either a NaBH(4) or a formaldehyde solution. Infiltrated films are then characterized by TEM, SEM, AFM, UV-visible spectroscopy, X-ray diffraction, and Rutherford Backscattering Spectrometry (RBS). The utilization of a mesoporous titania substrate allows to control the nanoparticle size and the interparticle distance. RBS experiments provide the evidence that NaBH(4) treatment induces a strong accumulation of silver nanoparticles in the subsurface of the layer, while formaldehyde treatment induces the formation of silver nanoparticles embedded into almost the whole depth of the titania film. Large silver nanocrystals are also formed at the film surface whatever the reducer used. A broad visible absorption band related to the surface plasmon resonance (SPR) is obtained in both cases and is strongly red-shifted compared to the SPR obtained for silver nanoparticles inside a silica matrix. Moreover, irradiation with visible light causes the photooxidation of silver nanoparticles by titania and a complete discoloration of the material. The photooxidation is related to a drastic decrease in the silver nanoparticle size and is found to be reversible, particularly in the case of the material obtained by the formaldehyde reduction.

Optical Properties of Hybrid Organic‐Inorganic Materials and their Applications

“…is still a subject of extensive investigation. Numerous papers reporting smart photochromic properties of Ag [211][212][213][214][215] species deposited onto TiO 2 substrates have appeared in the last years. Interesting properties are developed in titanate nanotubes loaded with AgCl or Ag NPs.…”

“…In the case of composite materials, basically two approaches can be found, either in situ synthesis of metal nanostructures in the matrix using chemical, thermal or photoinduced reductions; or incorporation of nanoparticles colloidal dispersions during the matrix preparation. The matrix can typically be inorganic, [496][497][498][499] sol-gel based matrix [215,[500][501][502][503][504][505][506][507][508][509][510] or polymers. [511][512][513][514] Regarding the in situ growth, the main drawbacks are the limitations in terms of control of the shape of the particles, which are often spherical or wire-type structures and the homogeneity in size and dispersion.…”

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

“…Ce dernier, le copolymère tribloc P123 dans le cas présent, est ensuite éliminé pour laisser place à une porosité de taille nanométrique (∼10 nm) homogène organisée au sein du film de TiO 2 . Le détail de protocoles de synthèse pouvant être utilisés se trouve par exemple dans les références [9,11,12]. Ces films mésoporeux, de 150 à 300 nm d'épaisseur, sont ensuite imprégnés d'un précurseur ionique métallique (nitrate d'argent ammoniacal), rincés puis séchés.…”

“…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]. Plusieurs expériences ont aussi été menées à la surface de substrats de TiO 2 monocristallin [16][17][18].…”

Synthesis of silver nanoparticles in DMSO solutions of starch: a comparative investigation of native and soluble starches

“…Chemical methods of AgNPs synthesis in aqueous solutions, using reductants such as sodium borohydride, quercetin, etc. are most frequently used [7][8][9]. Among the chemical techniques of AgNPs synthesis, it should be especially noted that ecologically safe biomineralization methods exist which are based on the use of saccharides (glucose, fructose, and so on) and polysaccharides (cellulose, cellulose ethers) as reducing agents [10][11][12][13][14][15][16].…”