Colloids and Surfaces B: Biointerfaces 77 (2010) 82–89 Contents lists available at ScienceDirect Colloids and Surfaces B: Biointerfaces journal homepage: www.elsevier.com/locate/colsurfb Nanocharacterization and bactericidal performance of silver modified titania photocatalyst Xubin Pan a , Iliana Medina-Ramirez b , Ray Mernaugh c , Jingbo Liu d,∗ a Environmental Engineering, Texas A&M University-Kingsville, Kingsville, TX 78363, USA b Department of Chemistry, Universidad Autonoma de Aguascalientes, Aguascalientes, Ags. 20100, Mexico c Department of Biochemistry, Vanderbilt University, Nashville, TN 37232, USA d Department of Chemistry, Texas A&M University-Kingsville, 700 University Blvd., MSC 161, Kingsville, TX 78363, USA article info Article history: Received 7 October 2009 Received in revised form 25 December 2009 Accepted 13 January 2010 Available online 21 January 2010 Keywords: Ag–TiO2 Colloidal chemistry Nanostructural characterization Bactericidal performance abstract An environmental-friendly procedure for manufacturing silver (Ag) and titania (TiO 2 ) nanocomposites in an aqueous solution is presented. This green synthetic approach results in the successful production of nanomaterials with high dispersion and crystallinity. The colloidal suspensions of the nanocomposites composed of metal and ceramic (Ag–TiO 2 ) were found to be extremely stable over a prolonged time period. Morphologically, nanocomposites were found to be composed of near-spherical particles that were highly crystalline. The nanocomposites were mono-dispersed with particles varying in size from 20 to 50 nm, depending upon nanocomposite solution pH. Indexed metallic nanoscale silver exhibited a face- centered cubic (fcc) crystalline phase structure. Nanocomposite elemental composition studies indicated that the molar ratio of Ag and Ti was approximately 1–20. The binding energies and energy differences of Ag, Ti and O were well-indexed with their associated standard spectra. Nanocomposite optical absorption properties were consistent with noble metal nanoparticles. The zetapotential for the nanocomposites was higher at acidic pH and exhibited an absolute negative charge that apparently inhibited particle agglomeration. Escherichia coli (E. coli), a Gram-negative model microorganism was effectively inactivated using the nanocomposites under visible light at ambient temperature and pressure. The ‘green chemistry’ derived Ag–TiO 2 composites are applicable for the removal of biological impurities from drinking and underground water supplies. The results of the study indicated that nanocomposites could be specifically designed to prevent growth of bacteria in water. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Numerous investigations have been conducted to design and manufacture heterogeneous photocatalysts with high chemical activities for environmental applications [1,2]. Titanium dioxide (TiO 2 ) photocatalysts have been extensively studied since they are chemically stable and exhibit strong catalytic activity [3,4]. TiO 2 mineralize recalcitrant pollutants and exhibit antibacterial and self-cleaning properties [5,6]. Most importantly, TiO 2 catalysts have been proven to be excellent and efficient photocatalysts for the degradation and inhibition of numerous toxic environmental contaminants [7,8]. Diverse applications of TiO 2 include (a) air and water cleaning (e.g. sterilization, removal of odor and hazardous substances) and (b) surface cleaning (antimicrobial activity, self- cleaning, etc.) [9]. ∗ Corresponding author. Tel.: +1 361 593 2919; fax: +1 361 593 3597. E-mail address: kfjll00@tamuk.edu (J. Liu). It is also known that loading of a noble metal onto the surface of TiO 2 powder or thin film enhances the material’s quantum effi- ciency and decreases the band gap of TiO 2 [10,11]. Noble metal Ag is an important disinfectant agent and its use in the purification of both water and air has been established [12,13]. The photocat- alytic activity of thin TiO 2 films and bactericidal activity of metal doped (silver (Ag), gold (Au), copper (Cu), and platinum (Pt)) and anion doped (nitrogen (N), fluorine (F), and phosphorous (P)) TiO 2 under visible light illumination have been reported [14,15]. TiO 2 and Ag nanostructured composites can also be used for water and air quality control [16,17]. TiO 2 thin films modified by metal ions can be fabricated using through a colloidal approach [18]. How- ever, ultraviolet (UV) illumination is generally required to promote colloidal-fabricated TiO 2 photocatalytic and antibacterial activi- ties; but there are reports that visible light can also promote TiO 2 photocatalytic activity [19]. Although nanocomposites that use noble metals have shown promise for use as catalysts and bactericidal agents, the manufac- turing costs used to produce such reagents are high and preclude their common use for such applications. In an attempt to overcome 0927-7765/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfb.2010.01.010