Highly photoactive Au-TiO2 nanowires for improved photo-degradation of propiconazole fungicide under UV/sunlight irradiation

Lengthy TiO2 nanostructures exhibiting improved physicochemical properties have been recently investigated for many useful applications. In this context, elongated TiO2 nanowires (TNW) of length 1.9-8 mu m; diameter 80-270 nm are prepared and 1 wt% Au was photodeposited onto TNW for enhanced photo-degradation of propiconazole fungicide under UV/visible light irradiation. The phase composition of TNW (anatase = 72%, rutile = 28%) was almost similar to commercially available P25 TiO2 (anatase = 70%, rutile = 30%). TEM analysis reveals uniform dispersion of spherical Au nanoparticles (3-5 nm) deposits over entire TNW surface. The specific surface area 148 m(2) g(-1) of TNW is notably higher than 59 m(2) g(-1) of P25 TiO2 which is reduced slightly to 136 m(2) g(-1) after Au loading. TNW exhibited increased (45-64 mu s) relaxation time of photoexcited e(-)/h(+) pairs as compared to P25 TiO2 due to its elongated structure and after Au loading further improves the charge separation efficiency (79 mu s). The complete photodecomposition of propiconazole to CO2 by bare and Au-loaded TNW under light irradiation through formation of various intermediate products was monitored through HPLC, GC and GC-MS analysis. It revealed that Au-loaded TNW always exhibited 3.5-40 times higher photocatalytic activity than mostly used P25 TiO2 because of more anatase phase, larger specific surface area and a higher lifetime of excited charge species where Au loading enhanced the visible light absorption capacity due to surface plasmon interaction. (C) 2017 Elsevier Ltd. All rights reserved.