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Surface-enhanced Raman scattering; magnetic nanoparticles; core-shell nanostructure; bio-diagnosis.

We report the optimization and usage of surfactantless, water dispersible Ag and Au-coated 𝛾 –Fe₂O₃ nanoparticles for applications in surface-enhanced Raman scattering (SERS). These nanoparticles, with plasmonic as well as super paramagnetic properties exhibit Raman enhancement factors of the order of 10⁶ (10⁵) for Ag (Au) coating, which are on par with the conventional Ag and Au nanoparticles. Raman markers like 2-naphthalenethiol, rhodamine-B and rhodamine-6G have been adsorbed to these nanoparticles and tested for nonresonant SERS at low concentrations. Further, to confirm the robustness of Ag-coated nanoparticles, we have performed temperaturedependent SERS in the temperature range of 77–473 K. The adsorbed molecules exhibit stable SERS spectra except at temperatures >323 K, where the thermal desorption of test molecule (naphthalenethiol) were evident. The magnetic properties of these nanoparticles combined with SERS provide a wide range of applications.

G V Pavan Kumar¹ N Rangarajan¹ B Sonia¹ P Deepika¹ Nashiour Rohman¹ Chandrabhas Narayana¹

1. Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560 064, India

Published

April 2011

Manuscript received

23 August 2008