Quantum Effects Enter Semiconductor-Based SERS: Multiresonant MoO3•xH2O Quantum Dots Enabling Direct, Sensitive SERS Detection of Small Inorganic Molecules

There is keen research interest in building highly effective semi-conductor-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 MoO3middotxH2O quantum dots (QDs), to achieve direct andsensitivefingerprinting of the inorganic species hydrazine, which is afirst attempt insemiconductor-based SERS research, as well as various other probe molecules. Theresulting SERS platform that uses QDs with average size of 2.2 nm could successfullydetect the signal of hydrazine with a limit of detection estimated to be around 4x10-5M, significantly lowering the detectable concentration by at least 1000-fold, insharp 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 MoO3middotxH2O. 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 a strong research interest in constructing highly effective semiconductor-based SERS platforms, but current tuning methods have not been successful in creating sensors for small inorganic molecules. This study demonstrates the use of MoO3 middotxH2O quantum dots for sensitive detection of hydrazine and other probe molecules, utilizing the quantum size effect to enhance SERS activity.