Enhancing hybrid metal-semiconductor systems beyond SERS with PIERS (photo-induced enhanced Raman scattering) for trace analyte detection

Abstract

Hybrid metal-semiconductor systems are promising substrates for field Raman analysis due to their ability to use both electromagnetic and chemical enhancement pathways for surface enhanced Raman spectroscopy (SERS). Photo-induced Raman spectroscopy (PIERS) has previously been shown to be a promising method utilizing an additional enhancement route through photo-inducing atomic surface oxygen vacancies in photocatalytic metal-oxide semiconductors. The photoinduced vacancies can form vibronic coupling resonances, known as charge transfers, with analyte molecules, enhancing the signal beyond conventional SERS enhancements. However, conventional UV sources most often used for excitation of the PIERS substrate are impractical in combination with portable Raman systems for field analysis. In this work we show how a small UVC LED, centered at 255 nm, can replicate the same results previously reported with the benefit of allowing greater in-situ real time measurements under constant UV exposure. The UV LED source can be controlled more easily and safely, making it a practical UV source for field PIERS analysis.