Cent. Eur. J. Phys. • 9(2) • 2011 • 542-546 DOI: 10.2478/s11534-010-0069-x Central European Journal of Physics Sensitizing of Sm 3+ fluorescence by silver dopant in the TiO 2 films ∗ Research Article Leonid Dolgov †‡ , Valter Kiisk, Valter Reedo, Siim Pikker, Ilmo Sildos, Jaak Kikas Institute of Physics, University of Tartu, Riia 142, 51014, Tartu, Estonia Received 16 June 2010; accepted 26 July 2010 Abstract: Composite material based on a TiO 2 matrix doped with Sm 3+ ions and co-doped with silver was inves- tigated. Samarium ions together with nano- and micro-aggregates of silver were incorporated into the titanium alkoxide during the sol-gel process. Samarium ions were excited either directly (λ exc = 488 nm) or through the TiO 2 host (λ exc = 355 nm). It was revealed that samarium fluorescence (λ exc = 488 nm) in gelled TiO 2 films is enhanced by up to 20 times in the vicinity of silver inclusions. Sensitizing and plasmonic mechanisms of enhancement in Sm 3+ fluorescence are discussed. PACS (2008): 82.70.Gg, 78.67.-n, 78.67.Bf, 73.20.Mf Keywords: titanium dioxide • rare earth fluorescence • silver nanoparticles © Versita Sp. z o.o. 1. Introduction Nanoparticles of noble metals are frequently used as plas- monically active dopants in optical materials [1, 2]. The incident light can create electronic oscillations (plasmon polaritons) on the surface of the nanoparticles at the res- onant wavelength. As a result of this, in the vicinity of the nanoparticles, typically at 5-15 nm, electric field of light is strongly enhanced [3, 4]. Consequently the rate of radiative transitions and quantum yield of fluorescence for fluorescent molecules placed near surface of noble ∗ presented at the 6th International Conference on Functional Materials and Nanotechnologies, March 17-19, 2010, Riga, Latvia † E-mail: dolgov@fi.tartu.ee ‡ on leave of absence from Institute of physics, NASU, prospect Nauki 46, 03028 Kyiv, Ukraine metal particles may be enhanced. This effect is frequently used for enhancement of fluorescence from different or- ganic molecules in liquid media [3, 5, 6]. But effective plasmonic enhancement of fluorescence in solid films or waveguides was obtained mainly for near the infrared re- gion [1, 7]. Recently in a paper [8] we proposed sol-gel prepared TiO 2 films doped with silver nanoparticles. These films have effective plasmonic light absorption band with a maxi- mum near 400 nm. Doping of these films with lumines- cent markers that emit in the visible range can be con- sidered as a way to implement novel photonic materials. Previous investigations demonstrated that fairly efficient host-sensitized luminescence from Sm 3+ ions in TiO 2 ma- trix can be obtained [9–11]. Moreover, rare earth fluores- cence can serve as identification of a crystalline phase of a surrounding TiO 2 matrix [11]. Thus emitting prop- erties of Sm 3+ ions confined in the TiO 2 :Ag host matrix 542 Author copy