title: Reduction of Cr(VI) to Cr(III) using silicon nanowire arrays under visible light irradiation.
abstract: We report an efficient visible light-induced reduction of hexavalent chromium Cr(VI) to trivalent Cr(III) by direct illumination of an aqueous solution of potassium dichromate (K2Cr2O7) in the presence of hydrogenated silicon nanowires (H-SiNWs) or silicon nanowires decorated with copper nanoparticles (Cu NPs-SiNWs) as photocatalyst. The SiNW arrays investigated in this study were prepared by chemical etching of crystalline silicon in HF/AgNO3 aqueous solution. The Cu NPs were deposited on SiNW arrays via electroless deposition technique. Visible light irradiation of an aqueous solution of K2Cr2O7 (10(-4)M) in presence of H-SiNWs showed that these substrates were not efficient for Cr(VI) reduction. The reduction efficiency achieved was less than 10% after 120 min irradiation at λ>420 nm. Addition of organic acids such as citric or adipic acid in the solution accelerated Cr(VI) reduction in a concentration-dependent manner. Interestingly, Cu NPs-SiNWs was found to be a very efficient interface for the reduction of Cr(VI) to Cr(III) in absence of organic acids. Almost a full reduction of Cr(VI) was achieved by direct visible light irradiation for 140 min using this photocatalyst.
authors.affiliation: Institut d'Electronique, de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, Avenue Poincaré-BP 70478, 59652 Villeneuve d'Ascq Cedex, France; Centre de Recherche en Technologie des Semi-conducteurs pour l'Energétique-CRTSE 02, Bd Frantz Fanon, BP. 140, Alger 7 Merveilles, Algeria.
authors.forename: Ouarda
authors.initials: O
authors.lastname: Fellahi
authors.affiliation: Institut d'Electronique, de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, Avenue Poincaré-BP 70478, 59652 Villeneuve d'Ascq Cedex, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Barras
authors.affiliation: State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, 3888 Dong Nanhu Road, Changchun 130033, China.
authors.forename: Guo-Hui
authors.initials: GH
authors.lastname: Pan
authors.affiliation: Institut d'Electronique, de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, Avenue Poincaré-BP 70478, 59652 Villeneuve d'Ascq Cedex, France.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Coffinier
authors.affiliation: Centre de Recherche en Technologie des Semi-conducteurs pour l'Energétique-CRTSE 02, Bd Frantz Fanon, BP. 140, Alger 7 Merveilles, Algeria.
authors.forename: Toufik
authors.initials: T
authors.lastname: Hadjersi
authors.affiliation: Laboratoire de Physique Quantique et Systèmes Dynamiques, Département de Physique, Université de Sétif, Sétif 19000, Algeria.
authors.forename: Mustapha
authors.initials: M
authors.lastname: Maamache
authors.affiliation: Institut d'Electronique, de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, Avenue Poincaré-BP 70478, 59652 Villeneuve d'Ascq Cedex, France.
authors.forename: Sabine
authors.initials: S
authors.lastname: Szunerits
authors.affiliation: Institut d'Electronique, de Microélectronique et de Nanotechnologie (IEMN), UMR CNRS 8520, Avenue Poincaré-BP 70478, 59652 Villeneuve d'Ascq Cedex, France. Electronic address: rabah.boukherroub@iemn.univ-lille1.fr.
authors.forename: Rabah
authors.initials: R
authors.lastname: Boukherroub
keywords: Chromium(III); Chromium(VI); Copper nanoparticles; Organic acids; Photocatalysis; Silicon nanowires; Visible light