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Enhancement of ZnO Photocatalytic Activity by Incorporation of Silver Nanoparticles
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Reena George, Michael K Seery and Suresh C Pillai
DT203/4 Forensic and Environmental Analysis
School of Chemical and Pharmaceutical Sciences, DIT
[email protected]
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Introduction
Results and Discussion
ZnO is a wide band gap semiconductor whose photocatalytic activity has been
widely studied. This work reports a study of the incorporation of silver
nanoparticles into the ZnO matrix with the aim of enhancing the photocatalytic
activity. The mechanism is studied by monitoring the excitonic emission of ZnO.
• XRD confirmed formation of nano-sized ZnO at T > 400 °C with no change in
spectral shape on addition of Ag (Figure 3a) – indicating Ag depositing along
grain boundaries.
• DSC analysis showed formation of crystalline ZnO at 405 °C, and in the case of
Ag-ZnO the decomposition of Ag2O at 395 °C (Figure 3b). IR and Raman spectra
confirmed the formation of ZnO at T>400 °C (Figure 3c and 3d).
Figure 1: Incorporation of silver facilitates electron trapping, with consequent reduction
in emission intensity, which allows hole to oxidise water to produce hydroxyl radicals
Experimental Details
Figure 3: (a) XRD of Ag-Zno; (b) DSC of Ag-ZnO, (c) IR of Ag-Zno at 80, 300 and 400 °C and
(d) Raman spectrum of Ag-ZnO
• Emission intensity reduced on increasing Ag loading indicating electron
trapping by silver (Figure 4a). Strong excitonic emission (390 nm) indicates
good crystalline quality (cf. Raman)
0 – 5 mol % Ag-ZnO was synthesised by adding increasing amounts of silver
• Photocatalytic activity significantly increases on addition of silver, up to 5
nitrate to an ethanolic solution (700 mL) of zinc acetate (10.98 g) and oxalic acid
mol%. Above this loading silver covers catalyst surface and provides
(12.55 g) at 60 °C. The sol was stirred for 2 h to give a gel, which was calcined at a
recombination sites. (Figure 4b)
range of temperatures from 300 – 1000 °C to give Ag-ZnO nanopowder.
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Figure 4: (a) Emission spectra of Ag-ZnO. (Inset: Stern-Volmer Plot) (b) variation in
degradation rate consant of rhodamine 6g on increasing silver loading
Acknowledgments
RG thanks HEA for funding
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Figure 2: Experimental procedures carried out to synthesise and
characterise Ag-ZnO and study its photocatalytic activity and mechanism of – just remember to have
the extra details at hand
enhancement
References
Key references
related directly to
poster
M. J. Height, S. E. Pratsinis, O. Mekasuwandumrong, P. Praserthdam, Appl. Cat. B.
Environmental, 2006, 63, 305.
M K Seery, R George, P Floris, S C Pillai, J. Photchem. Photobiol. A. 2007,189 (2-3), 258.