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International Journal of Spectroscopy
Volume 2011 (2011), Article ID 989504, 9 pages
Research Article

Improving SERS Detection of Bacillus thuringiensis Using Silver Nanoparticles Reduced with Hydroxylamine and with Citrate Capped Borohydride

1Department of Chemistry, ALERT-DHS Center of Excellence, Center for Chemical Sensors Development, University of Puerto Rico-Mayagüez, P.O. Box 9000, Mayagüez, PR 00681-9000, Puerto Rico
2Microbial Biotechnology and Bioprospecting Laboratory, Department of Biology, University of Puerto Rico-Mayagüez, P.O. Box 9000, Mayagüez, PR 00681-9000, Puerto Rico

Received 1 May 2011; Accepted 14 June 2011

Academic Editor: Ahmed Aamouche

Copyright © 2011 Hilsamar Félix-Rivera et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The development of techniques that could be useful in fields other than biological warfare agents countermeasures such as medical diagnostics, industrial microbiology, and environmental applications have become a very important subject of research. Raman spectroscopy can be used in near field or at long distances from the sample to obtain fingerprinting information of chemical composition of microorganisms. In this research, biochemical components of the cell wall and endospores of Bacillus thuringiensis (Bt) were identified by surface-enhanced Raman scattering (SERS) spectroscopy using silver (Ag) nanoparticles (NPs) reduced by hydroxylamine and borohydride capped with sodium citrate. Activation of “hot spots”, aggregation and surface charge modification of the NPs, was studied and optimized to obtain signal enhancements from Bt by SERS. Slight aggregation of the NPs as well as surface charge modification to a more acidic ambient was induced using small-size borohydride-reduced NPs in the form of metallic suspensions aimed at increasing the Ag NP-Bt interactions. Hydroxylamine-reduced NPs required slight aggregation and no pH modifications in order to obtain high spectral quality results in bringing out SERS signatures of Bt.