Rational regulating the Zn/Cd-S-Sn bond and oxygen vacancy environment of CdZnS/Eu2Sn2O7 heterointerface luminophore for highly efficient ratiometric electrochemiluminescence intelligent monitoring of sunset yellow

Inspired by the metal coordination bond structure of interface engineering strategy, CdZnS/Eu2Sn2O7 with heterointerfaces and enrich oxygen vacancies (OVs) were elaborately designed as cathode luminophores. The ratiometric electrochemiluminescence (RECL) system was reasonably constructed though incorporating biomass-derived nitrogen-doped carbon dots (BD-NCDs) as the anode luminophore, and H2O2 installed as co-reagent. We showed here that the formation of Zn/Cd-S-Sn bonds at the interface was induced, which promoted electron transfer and electrochemical reaction kinetics. Both experiments and density functional theory (DFT) calculations systemically revealed that CdZnS/Eu2Sn2O7 possessed the ability to achieve self-reinforced RECL though employing Zn/Cd-S-Sn bond and OVs as the main catalytic active sites, respectively. The numerous •OH was formed to significantly amplify the ECL intensity of the cathode by 4.7 and 14.4 times respectively, compared to CdZnS and Eu2Sn2O7. Interestingly, it was also confirmed that the OVs directly participate in the electrochemical reaction as the active site for catalyzing H2O2 to generate an abundance of O2•- to accomplish sharp amplification of the anode signal by 5.7-fold. Additionally, benefiting from the outstanding performance of the CdZnS/Eu2Sn2O7/GCE+BD-NCDs+H2O2 RECL system, the sensing system was designed for the detection of sunset yellow from 0.1 to 4000 nM. More importantly, the successful construction of machine learning-assisted portable devices integrated with smartphones also provides a novel strategy for SY on-site detection. This work not only guides further elucidation of the self-enhanced RECL catalytic mechanism but also facilitates the future development of rational luminophore designs for the point-of-care test.