Ultrasensitive protein detection in terms of multiphonon resonance Raman scattering in ZnS nanocrystals

Ultrasensitive protein detection was realized using multiphonon Resonance Raman scattering in ZnS nanocrystals. The longitudinal optical phonon line of ZnS and its overtones, which are called multiphonon Raman lines (MRLs), were used as the Raman probe signals. MRLs have a narrow bandwidth, high stability in aqueous solution, and strong resistance to interference from surface variations. Our results show that these features allow for reliable biodetection with good selectivity and high specificity. The detection limit is about 5 fM. This Raman scattering-based methodology will greatly extend the potential applications for ZnS in the biomedical sciences.