121 Novel Engineered Nanoparticle Cluster Array (NCA) SERS Substrates for Biological Applications

Wednesday, November 4, 2009: 8:40 AM
Longhorn (Camino Real Hotel)
Saraf Nawar , Davis Senior High School, Davis, CA
Bo Yan , Department of Chemistry, Boston University, Boston, MA
Björn Reinhard , Chemistry, Boston University, Boston, MA
Surface Enhanced Raman Spectroscopy (SERS) has grown as a promising tool for biological applications, including the spectroscopic detection of infectious pathogens. Yet even today many noble metal nanoparticle-based SERS substrates suffer from the lack of rational design criteria, thus making it difficult to control their structural parameters and reproducibly produce large SERS enhancements at defined locations. Particularly, hollow Ag-Au alloy nanoparticles have gained interest as SERS substrates due to the ability to easily tune their Plasmon resonance. However, it remains challenging to create efficient engineered SERS substrates using these nanostructures.

Here, Ag-Au alloy hollow nanoparticles with tunable optical properties were synthesized from Ag colloids using a galvanic replacement approach. Afterwards, both Ag nanoparticles and the hollow particles were used for the assembly of SERS substrates with rational design using template-guided self-assembly on top of gold-coated glass slides. This protocol allowed for the fabrication of nanoparticle cluster arrays (NCAs) with defined structural parameters such as edge-to-edge separation up to 50 nm between nanoparticle clusters with defined particle numbers. The NCAs were then systematically characterized through measurements of Raleigh scattering spectra and Raman scattering (SERS) signal intensities. Both the Ag colloidal and Ag-Au hollow NCAs provided prominent signals with para-mercaptoaniline (pMA) as test substance, with the latter providing SERS enhancement factor up to ~105. The Ag-Au hollow NCA substrates also provide strong, reproducible signals for the detection of the Staphylococcus aureus bacteria species, indicating that such substrates hold promise for rapid and reliable identification of bacterial pathogens with high sensitivity.

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