Reda M. Mohamed 1,2,3 Elham S. Aazam 1 1 Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia 2 Nanostructured Material Division Advanced Materials Department, Central Metallurgical R&D Institute, Helwan, Cairo, Egypt 3 Center of Excellence in Environmental Studies, King Abdulaziz University, Jeddah, Saudi Arabia Research Article New Visible-Light Pt/PbS Nanoparticle Photocatalysts for the Photocatalytic Oxidation of Thiophene PbS nanoparticles were prepared using a hydrothermal route, and Pt was deposited onto the PbS nanoparticles via a photo-assisted deposition route. The photocatalytic performances of the PbS and Pt/PbS samples were examined for the photocatalytic oxidation of thiophene under visible light. Deposition of Pt onto the surface of PbS led to a shift in the absorption of PbS to a higher wavelength (red shift). The 0.15 wt% Pt/PbS nanoparticles had the highest photocatalytic efficiency % (100%) for the degradation of thiophene under visible light after 40 min of reaction time. The 0.15 wt% Pt/PbS nanoparticles can be used six times for the degradation of thiophene without a loss of photocatalytic activity. Keywords: Oil pollution; Photo-assisted deposition; Photostability; Visible photocatalysts Received: February 9, 2014; revised: March 2, 2014; accepted: March 28, 2014 DOI: 10.1002/clen.201400115 1 Introduction The removal of dangerous organic pollutants by photocatalysis is of great importance and interest for environmental safety [1–5]. It is difficult to remove pollutants from fuel oils that contain sulfur- containing organic compounds [6]. One of the main compounds in oil pollutants is thiophene, which is very difficult to remove by a conventional oxidation process such as the desulfurization process. The low electron density on the sulfur atom and the aromaticity of the thiophene molecule make it difficult to oxidize. Therefore, researchers must develop an efficient photocatalyst to oxidize thiophene. The efficiency of the photocatalyst depends on its stability, particle size, surface area, band gap, and electron–hole recombination lifetime [7]. Many researchers have tried to develop photocatalysts by changing preparation methods, doping with metals, and oxide mixing [8–12]. The most famous photocatalyst is TiO 2 , which has a band gap of approximately 3.2 eV, and many published papers have attempted to increase its photocatalytic activity and surface area and increase its e–h recombination lifetime and band gap [13–19]. The semiconductor silver sulfide has a narrow band gap with excellent optical properties and good chemical stability [20–24]. Silver sulfide has been prepared by many methods, such as using organometallic precursors [25], using gamma irradiation [26], sonochemical methods [27], templating meth- ods [28], sol–gel and ion-implantation techniques [29], micro- emulsions [30], etc. To the best of our knowledge, there are no published papers about enhancement of photocatalytic activity of lead sulfide. In this work, PbS and Pt/PbS nanoparticles were prepared and characterized. The photocatalytic performance of PbS and Pt/PbS nanoparticles was studied for the oxidation of thiophene under visible light. 2 Experimental 2.1 Synthesis of PbS All chemicals used are of analytical grade and are used without further purification. The PbS nanoparticles were prepared by the following procedure. 10 mM thioacetamide and 2.5 mM PbCl 2 were dissolved in deionized water (40 mL). The resulting mixture was placed into an autoclave for 24 h at 200°C. The material produced was separated by centrifugation and then washed several times by deionized water and absolute ethanol. Finally, the PbS nanoparticles were dried in a vacuum oven for 3 h at 80°C. 2.2 Synthesis of Pt/PbS The Pt/PbS nanoparticles were prepared by the photo-assisted deposition (PAD) method according to the following procedure. A certain amount of PbS was dispersed in an aqueous solution of H 2 PtCl 6 , and then the resulting mixture was irradiated by UV light for 24 h. The material produced was dried for 24 h at 100°C. Using the PAD method, various wt% values of Pt (0.05, 0.10, 0.15, and 0.20 wt% of Pt metal) were deposited onto the PbS. 2.3 Characterization techniques X-ray diffraction (XRD) analysis was performed at room temperature (Bruker AXS D8) using Cu Ka radiation (l ¼ 1.540 Å). The specific surface area was calculated from measurements of the N 2 adsorption using a Nova 2000-series Chromatech apparatus at Correspondence: Professor R. M. Mohamed, Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, P.O. Box 80203, Saudi Arabia E-mail: mhmdouf@gmail.com Abbreviations: BET, Brunauer–Emmett–Teller; PAD, photo-assisted deposition; PL, photoluminescence; TEM, transmission electron microscopy; XPS, X-ray photoelectron spectroscopy; XRD, X-ray diffraction 1 © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.clean-journal.com Clean – Soil, Air, Water 2014, 42 (9999), 1–6