Defect minimized Ag-ZnO microneedles for photocatalysis
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RESEARCH ARTICLE
Defect minimized Ag-ZnO microneedles for photocatalysis Sanjay Gopal Ullattil 1
&
M. J. Jabeen Fatima 2 & Ahmed Abdel-Wahab 1
Received: 30 October 2019 / Accepted: 25 May 2020 # The Author(s) 2020
Abstract A facile solution processing strategy has been developed for the formation of Ag-modified ZnO microneedles at various calcination temperatures such as 300, 500, and 700 °C (AZ3, AZ5, and AZ7 respectively). Due to the heavy doping of AgNO3, Ag+ ions have been incorporated in to the crystal lattice of ZnO in all the Ag-ZnO samples, which facilitated the formation of Ag-ZnO microneedle morphology with minimized defect states, and obviously, the plasmon peaks were observed due to Ag modification. These Ag-ZnO microneedle structures have been evaluated for their photocatalytic performance using methylene blue as model target contaminant and their activity was compared with the commercially available titania P25 photocatalyst. The photoactivity of all the Ag-ZnO microneedle structures was significantly higher than that of the commercially available P25 photocatalyst with the most active Ag-ZnO material having a photocatalytic activity ~ 1.4 times greater than that of P25 titania. Keywords Heavy Ag loading . Ag-ZnO microneedles . Surface plasmon . Electron density . Solar energy . Photocatalysis
Introduction ZnO has been widely used as a photocatalyst in its pure form or after modification by the incorporation of foreign materials such as metals (Vaiano et al. 2018), non-metals (Kumari et al. 2019), and organics (Ansari et al. 2013). ZnO is a semiconductor with a large band gap of 3.37 eV. It is a suitable candidate in photocatalysis due to its ecofriendly nature, low cost, and high catalytic efficiency (Ong et al. 2018). When a photon energy of higher than or equal to its band gap energy is irradiated onto ZnO, the electrons in the valance band (VB) jump to the conduction band (CB) leading to the formation of
Responsible editor: Suresh Pillai Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11356-020-09433-5) contains supplementary material, which is available to authorized users. * Sanjay Gopal Ullattil [email protected] * Ahmed Abdel-Wahab [email protected] 1
Chemical Engineering Program, Texas A&M University at Qatar, 23874, Education City, Doha, Qatar
2
Department of Nanoscience and Technology, University of Calicut, Malappuram, Kerala 673635, India
electron-hole pairs (Ong et al. 2018). These electron-hole pairs can recombine within nanoseconds, which limits the photocatalytic efficiency of ZnO material. This unfavorable situation can be overcome by introducing a noble metalsemiconductor interface that can generate a Schottky barrier effect to inhibit the electron-hole recombination and thereby increase the photocatalytic efficiency (Yan et al. 2014). Silver is one of the prominent candidates that can be used as dopant/modifier which generate Ag-loaded ZnO nanostructures (Ag-ZnO) with a lower Fermi level (Ef) than the CB
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