Plasmonic gold nanostars (NSts) demonstrate an enhanced electric field in their surrounding due to large number of ‘hot spots’ on their surface resulting in a unique ability to confine light within a nanometric volume. We are demonstrating beneficial properties of NSts as signal enhancers for tissue and cell imaging using optical coherence tomography (OCT), microscopy, surface-enhanced vibration spectroscopy (SEVS), including surface-enhanced Raman scattering (SERS), and surface-enhanced infrared absorption spectroscopy (SEIRAS) with an attenuated total reflectance (ATR) and infrared reflection-absorption spectroscopy (IRRAS) configurations.
Scattering ability of gold NSts with various sizes was investigated by OCT capillary imaging and light and confocal microscopy in vitro. The variation of NSts sizes allows one to shift plasmon resonance up to 1300 nm. The most intensive scattering signals were found from the largest NSts.
NSts were applied in SEVS scenarios using plasmonic chip-based systems containing self-assembled NSts on a silicon substrate both by evaporation and subsequent immobilization mediated by a gold layer and modified-dimercapto polyethylene glycol. The plasmonic substrates are able to concomitantly enhance Raman and mid-infrared signals. SERS and SEIRAS properties of such substrates were demonstrated. For SERS, by using crystal violet as a model analyte. The IR absorbance of analyte molecules placed on NSt-film deposited on a Si ATR crystal was up to 10 times higher for thioglycolic acid and 2 times higher for bovine serum albumin compared to a bare Si waveguide. For the best of our knowledge, this is the first attempt to use NSt-based substrate for SEIRAS studies.
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