Colloidal lenses as universal Raman scattering enhancers

Abstract

SiO₂ microspheres were tested as micro-lenses in a series of Raman experiments, in order to evaluate their potential application in analysis of thin films and molecular species. We demonstrate that colloidal lenses can act as versatile, universal Raman scattering enhancers, that can be easily implemented into conventional microspectroscopy experiments. Our results indicate that colloidal lenses can strongly enhance Raman scattering of all the analytes under investigation, extending their detection limits by several orders of magnitude. Colloidal lenses can be exploited as non-destructive, disposable tools for Raman detection of ultra-thin films. They can also be coupled to either metal- or all-oxide-based SERS active substrates to further boost Raman sensitivity, offering exciting perspectives for ultrasensitive detection and in situ monitoring of chemical and biochemical reactions under real-working conditions.