| Summary: | Carbon based dots capped tin oxide nanosheets (SnO₂/CDs) were synthesized by liquid exfoliation of tin oxide (SnO₂) nanoparticles in the presence of single-layer carbon based (CDs). The obtained SnO₂/CDs have lateral sizes of about 20–50 nm and heights of about 3–4 nm. A thin layer of CDs of about 1–2 nm in thickness are presence on the surface of the SnO₂ nanosheets. The SnO₂/CDs present excellent surface enhanced Raman spectroscopy (SERS) activity due to the chemical enhancement (CM) led by the charge transfer between SnO₂/CDs and the target molecules. The enhancement factor (EF) of the SnO₂/CDs is 1.42 × 10⁵, taking rhodamine 6G as a model target molecule. The SnO₂/CDs are further hybridized with silver nanoparticles (AgNPs) using an in situ synthesis method. The obtained homogeneous nano-hybrids (SnO₂/CDs@AgNPs) have a lot of nanogaps. The nanogaps among the AgNPs/CDs create strong electromagnetic enhancement (EM) due to the “hot spots” effect. The nanogaps among the SnO₂/CDs and AgNPs/CDs allow the target molecules to be embedded, and thus gained both the CM effect of SnO₂/CDs and the EM effect of AgNPs/CDs. As a result, the as-prepared SnO₂/CDs@AgNPs exhibits excellent SERS activities, with an ultrahigh enhancement factor of 3.27 × 10¹¹.
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