Photodeposited Ag-wires on TiO2 films

Abstract

Highly conducting films of Ag are photodeposited onto commercial self-cleaning glass (Pilkington, Activ™), as well as in-house prepared sol-gel TiO2 films, using an aqueous solution of AgNO3 containing a sacrificial electron donor, glycerol. Wire tracks are created by irradiating the photocatalytic surface through a stencil, promoting Ag-deposition only on the exposed/irradiated areas. The ability of the Ag-wires to conduct, and so heat up the underlying glass, is investigated initially for demisting purposes. The photodeposited Ag-wires on Activ™ glass are found to have a resistance of ca. 150 Ω after 2 h irradiation (I = 4 mW cm−2, 352 nm BLB), whereas the Ag-wires on sol-gel film, prepared under the same conditions, are ca. 3 times less resistive (55 Ω). Repeat heating-cooling cycles are achieved by applying a voltage, 12 V, across the Ag wires and demonstrate the robustness of the Ag-wires on Activ™ and sol-gel films, which produce a consistent rise in temperature above ambient room temperature of 20 °C, and 40 °C, respectively. A Scanning Electron Microscopy (SEM) study of Ag-particle growth on sol-gel TiO2 films demonstrates island growth of the Ag-particles, producing Ag ‘wires’ that are only able to conduct once the Ag ‘islands’ overlap; typically this is after ca. 9 min of irradiation (I = 4 mW cm−2), with R = 200 kΩ and Ag’ island’ particle size = ca. 100 nm. Upon further irradiation, the particles eventually grow sufficiently large that most Ag particles overlap and the resulting Ag wires are highly conducting (R = 55 Ω after 2 h).