Morphology Engineering of SnS₂ Nanostructures to Stimulate PICT Resonance for Ultra-Sensitive SERS Sensors

Recent advances indicate the surface-enhanced Raman scattering (SERS) sensitivity of semiconductors is generally lower than that of noble metal substrates, and developing ultra-sensitive semiconductor SERS substrates is an urgent task. Here, SnS₂ with better SERS performance is screened out from sulfides and selenides by density functional theory (DFT) calculations. Through adjusting the concentration of reactants to control the growth driving force without any surfactants or templates, SnS₂ nanostrctures of stacked nanosheets (SNSs), microspheres (MSs) and microflowers (MFs) are developed, which all exhibit ultra-low limit of detections (LODs) of 10^-12, 10^-13, and 10^-11 M, respectively. To the best of our knowledge, the SERS sensitivity of these three kinds of SnS₂ nanostrctures are superior to most of the reported pure semiconductors and even can be parallel to the noble metals with a "hot spot" effect. This extraordinary SERS enhancement of SnS₂ nanostrctures is originated from the dominated contribution of photo-induced charge transfer (PICT) resonance with different wavelength excitation lasers. Benefitting to the excellent SERS enhanced uniformity, generality, stability, ultra-high sensitivity of SnS₂ nanostrctures, and the advantages that the PICT resonance enhancement excited for different probe molecules is not limited by its morphology, it is expected to provide a class of potential commercial SERS-active materials for the practical application of semiconductor-based SERS technology.