Amorphous‐Crystalline Synergy in CoSe2/CoS2 Heterostructures: High‐Performance SERS Substrates for Esophageal Tumor Cell Discrimination

Although surface-enhanced Raman scattering (SERS) spectroscopy is applied in biomedicine deeply, the design of new substrates for wider detection is still in demand. Crystalline-amorphous CoSe₂/CoS₂ heterojunction is synthesized, with high SERS performance and stability, composed of orthorhombic (o-CoSe₂) and amorphous CoS₂ (a-CoS₂). By adjusting feed ratio, the proportion of a-CoS₂ to o-CoSe₂ is regulated, where CoSe₂/CoS₂-S50 with a 1:1 ratio demonstrates the best SERS performance due to the balance of two components. It is confirmed through experimental and simulation methods that o-CoSe₂ and a-CoS₂ have unique contribution, respectively: a-CoS₂ has rich vacancies and a higher density of active sites, while o-CoSe₂ further enriches vacancies, enhances electron delocalization and charge transfer (CT) capabilities, and reduces bandgap. Besides, CoSe₂/CoS₂-S50 achieves not only SERS detection of two common esophageal tumor cells (KYSE and TE) and healthy oral epithelial cells (het-1A), but also the discrimination with high sensitivity, specificity, and accuracy via machine learning (ML) analysis.