Surface Enhanced Raman Spectroscopy in a Microfluidic Device

David Dunmire, Danilo Romero, Guangjun Cheng, Angela Hight Walker
Physics Laboratory, National Institute of Standards and Technology (NIST), Gaithersburg, MD, USA

Surface enhanced Raman spectroscopy (SERS) is employed to study the solution phase vibrational structure of molecules on gold and silver colloids. Gold and silver colloids show large enhancement factors enabling sub-micromolar detection limits. Using a Raman microscope and microfluidics device, very small probe volumes are achieved while using a small sample size. Gold and silver colloids are prepared in situ in the device or injected already synthesized. Due to diffusion based mixing in the device, a streamline of the colloids can be maintained in the device allowing for a clearly defined sample region to be probed. The intensity enhancements for our samples are 106 when using the gold and silver colloids prepared in situ or injected. It is found the injection of pre-synthesized particles yields more desirable experimental conditions and the largest enhancement factors occur after significant aggregation has occurred.

David Dunmire

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