Quantum Effects Enter Semiconductor-Based SERS: Multiresonant MoO3middotxH2O Quantum Dots Enabling Direct, Sensitive SERS Detection of Small Inorganic Molecules

ABSTRACT: There is keen research interest in building highly effective semiconductor-based surface-enhanced Raman scattering (SERS) platforms, due to their selectivity for many probe molecules and suitability for complex scenario applications. However, current tuning approaches have not yet been successful in creating semiconductor-based SERS sensors for small inorganic molecules, due to the challenge of creating sufficient SERS enhancement in semiconductors. Here, we demonstrate the use of MoO3 center dot xH2O quantum dots (QDs), to achieve direct and sensitive fingerprinting of the inorganic species hydrazine, which is a first attempt in semiconductor-based SERS research, as well as various other probe molecules. The resulting SERS platform that uses QDs with average size of 2.2 nm could successfully detect the signal of hydrazine with a limit of detection estimated to be around 4 x 10-5 M, significantly lowering the detectable concentration by at least 1000-fold, in sharp contrast to the weak performance of 10 and 100 nm particles, demonstrating that quantum size effect triggered by small particle size below the Bohr radius is crucially responsible for high SERS activity. The significantly enhanced SERS activity is a result of vibronically coupled multipathway, highly efficient charge-transfer resonances induced by the divergence of energy states in quantum-sized MoO3 center dot xH2O. This is a proof-of-concept demonstration of the exploitation of quantum size effect, toward significantly enhanced intrinsic SERS activity in semiconductor-based SERS materials.

Automated summary

There is great research interest in building semiconductor-based SERS platforms, and this study demonstrates the use of MoO3·xH2O quantum dots to achieve highly efficient SERS sensing of small inorganic molecules. The study highlights the crucial role of the quantum size effect in enhancing SERS activity in semiconductor-based materials.