Research Article Study of Band Gap of Silver Nanoparticles—Titanium Dioxide Nanocomposites P. Barone, 1,2 F. Stranges, 1,2 M. Barberio, 1,2 D. Renzelli, 1 A. Bonanno, 1 and F. Xu 1 1 Physics Department, University of Calabria, Via Bucci 31C, 87036 Rende, Italy 2 Biology, Ecology and Earth Science Department, University of Calabria, Via Bucci 4B, 87036 Rende, Italy Correspondence should be addressed to P. Barone; pasquale.barone@fs.unical.it Received 8 January 2014; Accepted 21 March 2014; Published 9 April 2014 Academic Editor: Mallikarjuna N. Nadagouda Copyright © 2014 P. Barone et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Te optical and chemical properties of Ag/TiO 2 nanocomposites were investigated to explore the possibilities of incorporating these new materials in Gratzel photoelectrochemical cells. Te nanocomposites were obtained doping TiO 2 , in both allotropic species anatase and rutile, with silver nanoparticles (grown by laser ablation process). X-ray photoelectron data indicate the absence of Ag-Ti chemical bonds, while measurements of photoluminescence and optical absorbance in UV-visible range show a quench in photoluminescence emission of about 50% and an increase in visible absorbance of about 20%. Measurements of optical band gap, obtained by Tauc’s equation, indicate a variation of about 1.6 eV. 1. Introduction In recent decades, the scientifc community has devoted much efort to the enhancement of the feld of energy savings through the use of renewable energy. Although solid state junction devices with high efciency dominate the commercial market, these photovoltaic tech- nologies still receive constraints in market development due to both of expensive materials and complex manufacturing process. Consequently, the emerging photovoltaic technolo- gies, such as organic and inorganic cells, quantum dots, and dye sensitized solar cells, have attracted extensive attention because of their promising inexpensive technique based on the solution-processed materials. However, these new devices seem to be associated with unsatisfactory efciency (with value which ranges between 7% and 20% on laboratory prototypes) due of chemical and physical characteristics of employed materials. Recently, the interest has been focused on the application of nanostructured materials on dye sensitized solar cells (DSSCs). DSSCs mainly consist of a dye-sensitized TiO 2 flm deposited onto a transparent conducting substrate as the photoanode (working electrode), a redox active electrolyte, and a Pt cathode (counter electrode CE). Te use of TiO 2 (in both of its mineral phases, rutile and anatase) in DSSCs is suggested by its high chemical stability, excellent functional- ity, nontoxicity, optical proprieties (absorption of UV solar radiation), and relatively low cost [1–3]. However, the low efciency of DSSCs is linked to diferent factors as dye deterioration, electron/hole recombination in TiO 2 -dye substrate, and contact resistance between CE and electrolyte [1–3]. Moreover, the employ of titanium dioxide in solar cells is limited due of its transparency to visible light (only UV radiation is adsorbed and can be useful for photocatalytic activity) [4–8]. So, it is of great interest to extend the absorption wavelength of TiO 2 to the visible region. Tis objective can be reached introducing various dopants into titanium dioxide lattice [9–12]. Tis generates additional electronic states in the dioxide energy band gap causing changes in optical bands and, so, in absorbance [12]. Several studies on TiO 2 doping with heteroatoms (C, N, and S) have shown that it can reduce the TiO 2 optical band up to 0.8 eV [12]. Particularly, study on C-doping lead to growth of more reactive photocatalytic materials [5–7]. In a previous study, we used a simple mixing method to make CNTs/TiO 2 microcomposites [13–18]. Te luminescence emission of these composites is strongly modifed compared to pure Hindawi Publishing Corporation Journal of Chemistry Volume 2014, Article ID 589707, 6 pages http://dx.doi.org/10.1155/2014/589707