Enhancement in SERS intensities of azo dyes adsorbed on ZnO by plasma treatment
Version of Record online: 20 MAR 2014
Copyright © 2014 John Wiley & Sons, Ltd.
Journal of Raman Spectroscopy
Volume 45, Issue 5, pages 332–337, May 2014
How to Cite
Liu, C.-S., Li, B.-H., Chen, C.-H., Peng, J.-W. and Lee, S. (2014), Enhancement in SERS intensities of azo dyes adsorbed on ZnO by plasma treatment. J. Raman Spectrosc., 45: 332–337. doi: 10.1002/jrs.4465
- Issue online: 9 MAY 2014
- Version of Record online: 20 MAR 2014
- Manuscript Accepted: 24 FEB 2014
- Manuscript Revised: 11 FEB 2014
- Manuscript Received: 21 NOV 2013
- National Science Council of Taiwan. Grant Numbers: NSC 100–2113–M–033–004–MY3, NSC 100–2632–M-033–001–MY3
- azo dye;
Surface-enhanced Raman scattering (SERS) spectra of azo dyes (methyl orange and p-methyl red) adsorbed on ZnO nanoparticles were observed. Hydrothermally synthesized ZnO nanoparticles were characterized by powder X-ray diffraction and X-ray photoelectron spectroscopy. The ZnO nanoparticle size, monitored with X-ray diffraction, was tuned by calcination to optimize SERS intensities. The observed SERS effect of azo dyes adsorbed on ZnO can be ascribed to charge-transfer resonance effect. Time-dependent density functional theory was used to calculate the optical spectra and interpret the chemical enhancement observed in the experiment. The SERS enhancement factors for methyl red on ZnO were boosted by nearly four times and twice with O2 plasma and H2 plasma, respectively. However, plasma treatment showed no effect on the enhancement factors of methyl orange on ZnO. We conclude that plasma-induced defect formation and band gap shift in ZnO and the coupling of energy levels between ZnO and azo dye molecules are responsible for the observed enhancement of SERS intensities. Copyright © 2014 John Wiley & Sons, Ltd.