BandGap‐Tunable Carbon Quantum Dots for Surface‐Enhanced Raman Scattering

ABSTRACT Carbon dots (CDs) with photoluminescence properties have been widely recognized; however, their inherent surface‐enhanced Raman scattering (SERS) performance is rarely reported. Herein, we propose a type of bandgap‐tunable carbon quantum dots (CQDs) derived from metal‐phenolic network (MPN) that exhibits excellent and controllable SERS performance. MPN‐CQDs may be the ideal non‐metallic SERS substrates to accurately elucidate the chemical mechanism (CM) due to their simply controllable bandgap structure. By screening the coordinated metal ions of MPN, MPN‐CQDs can realize the optimal SERS effect with the maximum Raman enhancement factor of 5.5 × 10 4 , and also exhibit outstanding SERS reproducibility and stability. We then systematically disclose the interfacial photo‐induced charge transfer process and corresponding migration pathways between bandgap‐tunable MPN‐CQDs and the analyte. This class of nonmetallic SERS substrates is finally applied for the detection of hemoglobin with high sensitivity; further combined with a machine learning algorithm, we have successfully achieved precise identification of the heterogeneity of hemoglobin. This is the first evidence for the tunable SERS performance in CQDs, which also offers a facile avenue for in‐depth understanding of CM in nonmetallic materials.