Browsing by Author "Kumar, R.V."
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Item H2O2 rejuvenation-mediated synthesis of stable mixed-morphology Ag3PO4 photocatalysts(Heliyon, 2018-04) Agbe, H.; Raza, N.; Dodoo-Arhin, D.; Chauhan, A.; Kumar, R.V.Ag3PO4 photocatalyst has attracted interest of the scientific community in recent times due to its reported high efficiency for water oxidation and dye degradation. However, Ag3PO4 photo-corrodes if electron accepter such as AgNO3 is not used as scavenger. Synthesis of efficient Ag3PO4 followed by a simple protocol for regeneration of the photocatalyst is therefore a prerequisite for practical application. Herein, we present a facile method for the synthesis of a highly efficient Ag3PO4, whose photocatalytic efficiency was demonstrated using 3 different organic dyes: Methylene Blue (MB), Methyl orange (MO) and Rhodamine B (RhB) organic dyes for degradation tests. Approximately, 19 % of Ag3PO4 is converted to Ag0 after 4.30 hours of continuous UV-Vis irradiation in presence of MB organic dye. We have shown that the Ag/Ag3PO4 composite can be rejuvenated by a simple chemical oxidation step after several cycles of photocatalysis tests. At an optimal pH of 6.5, a mixture of cubic, rhombic dodecahedron, nanosphere and nanocrystals morphologies of the photocatalyst was formed. H2O2 served as the chemical oxidant to re-insert the surface metallic Ag into the Ag3PO4 photocatalyst but also as the agent that can control morphology of the regenerated as-prepared photocatalyst without the need for any other morphology controlling Agent (MCA). Surprisingly, the as- regenerated Ag3PO4 was found to have higher photocatalytic reactivity than the freshly made material and superior at least 17 times in comparison with the conventional Degussa TiO2, and some of TiO2 composites tested in this work.Item Microwave- and Formaldehyde-Assisted Synthesis of Ag−Ag3PO4 with Enhanced Photocatalytic Activity for the Degradation of Rhodamine B Dye and Crude Oil Fractions(ACS Omega, 2020-06-01) Nyankson, E.; Amedalor, R.; Chandrabose, G.; Coto, M.; Krishnamurthy, S.; Kumar, R.V.The release of crude oil and water-soluble dyes into our marine environment is a major global problem. An efficient semiconductor Ag–Ag3PO4 photocatalyst was synthesized using formaldehyde as a reducing agent to form surface active Ag on Ag3PO4 under microwave radiation for heating, and its potential in destroying environmental pollutants has been examined. The diffuse reflectance spectroscopy of Ag–Ag3PO4 revealed an enhanced absorption in the visible light region. The rate of photocatalytic degradation of rhodamine B by Ag–Ag3PO4 was over 4-fold compared to Ag3PO4. The potential application of Ag–Ag3PO4 in oil spill remediation was also examined through photocatalytic degradation of benzene, n-hexane, and 1:1 v/v benzene/methanol crude oil-soluble fractions. UV–vis and gas chromatography–mass spectrometry analysis of the crude oil components after visible light irradiation showed excellent degradation. The photocatalytic efficiency enhancement of Ag–Ag3PO4 is attributed to the excellent electron trapping of silver nanoparticles deposited on the surface of Ag3PO4. This work will motivate future studies to develop recyclable visible light photocatalysts for many applicationsItem A simple sensing of hazardous photo-induced superoxide anion radicals using a molecular probe in ZnO-Nanoparticles aqueous medium(Environmental Research, 2019-03-25) Dodoo-Arhin, D.; Agbe, H.; Raza, N.; Kumar, R.V.; Kim, K.The generation of reactive oxygen species (ROS) during the photolysis of sunscreens and sun blockers poses consumer safety concerns while necessitating proper identification and quantitation of ROS species. Here, a colorimetric sensing approach has been developed based on a molecular probe (2,3-bis-(2-methoxy-4-nitro-5- sulfophenyl)-2-H-tetrazolium-5-carboxanilide (XTT) tetrazolium salt) to quantitatively measure the photo-induced superoxide anion radicals (%O2 .) generated from the photocatalysis of zinc oxide nanoparticles (ZnO-NPs) in aqueous solutions. Note that superoxide anion radicals are assumed to be the main reactive oxygen species (ROS) generated from such photocatalysis. The characterisation of ZnO-NPs before and after irradiation showed average particle sizes of 616.5 and 295.3 nm and ζ-potential values of 0 and -24.4 mV, respectively. It is hoped that this proposed protocol can be further developed to efficiently detect other ROS present in inorganic sun blockers and to optimize the utility of various sunscreen formulations.