Fabrication of micro-patterned TiO 2 thin films incorporating Ag nanoparticles Kazuya Nakata a , Keizo Udagawa a,b , Donald A. Tryk c , Tsuyoshi Ochiai a , Shunsuke Nishimoto a , Hideki Sakai b , Taketoshi Murakami a , Masahiko Abe b , Akira Fujishima a, ⁎ a Kanawaga Academy of Science and Technology, Kawasaki 213-0012, Japan b Department of Pure and Applied Chemistry, Tokyo University of Science, Noda 278-8510, Japan c Fuel Cell Nanomaterials Center, University of Yamanashi, Koufu 400-8510, Japan abstract article info Article history: Received 3 April 2009 Accepted 24 April 2009 Available online 3 May 2009 Keywords: Sol–gel preparation Thin film TiO 2 Silver nanoparticles Patterning A photosensitive TiO 2 thin film embedded with Ag nanoparticles has been prepared from a Ti(OBu) 4 – acetylacetone solution, containing dispersed Ag nanoparticles, by the sol–gel method. UV–visible absorption spectra showed that the thin film obtained has two absorption bands, characteristic of the acetylacetone chelate rings and plasmon resonance from Ag nanoparticles. After the irradiation of UV light, the absorption band from the chelate rings almost disappeared, ascribed to structural changes associated with dissociation of the chelate rings. The thin film after the UV irradiation exhibited a broad absorption band in the IR spectrum, indicating that a Ti–O–Ti network was formed in the thin film. HRTEM and EDX spectra revealed that Ag nanoparticles were present and dispersed in the TiO 2 thin film. Micro-patterns of 50 μm dots have been fabricated by UV irradiation through a corresponding photomask, followed by leaching. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Patterned TiO 2 thin films have attracted much attention for potential applications for diffraction gratings [1], wettability patterns [2], photocatalytic lithography [3] and electroless metal deposition [4]. One of the preparation methods for patterned TiO 2 thin films is the sol–gel process, which utilizes photosensitive TiO 2 gel, followed by UV irradiation through a photomask, with subsequent leaching with alcohol or acidic aqueous solution [5]. The sol–gel process is a highly versatile technique that also enables the incorporation of noble metal nanoparticles such as Ag into the TiO 2 film [6]; such films can be applied as optical materials, for example, those exhibiting multi-color photochromism [7] as well as plasmonic photocatalysts [8] utilizing the plasmon resonance of Ag nanoparticles. It is expected that a patterned TiO 2 thin film embedded with Ag nanoparticles could potentially be applied for new functional materials and devices. In this work, we have fabricated micro-patterns of a TiO 2 thin film embedded with Ag nanoparticles, and characterized them by UV–visible spectra, IR spectra, HRTEM images and EDX spectra. 2. Experimental 2.1. Preparation of Ag nanoparticles Ag nanoparticles were synthesized according to the literature with a slight modification [9]: a 2-propanol solution (100 ml) containing titanium(triethanolaminate)isopropoxide (75 mM) was added to DMF (50 ml) and an aqueous solution (50 ml) of silver nitrate (30 mM), and was stirred for 20 min at room temperature. After refluxing for 90 min, the solution was cooled to room temperature and allowed to stand for 24 h. A black powder appeared and was collected with a centrifuge. The final product powder was obtained after washing with toluene and drying in vacuo. 2.2. Preparation of TiO 2 thin films embedded with Ag nanoparticles The preparation process was performed inside a N 2 -filled glove box. A 2-propanol solution (18 ml) containing titanium tetrabutoxide (2.1 g, 6 mmol) was added to acetylacetone (1.2 g,12 mmol) and was stirred for 24 h at room temperature. The resulting solution was added to a 2-propanol solution (18 ml) containing Ag nanoparticles (0.3 g) dissolved by sonication for 24 h. The solution was then coated on a glass substrate by the dip-coating technique at a rate of 2.5 mm/s. 2.3. Micro-patterning of TiO 2 thin film embedded with Ag nanoparticles The TiO 2 thin film embedded with Ag nanoparticles described above was irradiated with UV light (He–Xe lamp, 26 mW/cm 2 ) for Materials Letters 63 (2009) 1628–1630 ⁎ Corresponding author. Postal address: 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan. Tel.: +81 44 819 2040; fax: +81 44 819 2070. E-mail address: fujishima@newkast.or.jp (A. Fujishima). 0167-577X/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2009.04.035 Contents lists available at ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/matlet