Europium-Functionalized Graphitic Carbon Nitride for Efficient Chemiluminescence Detection of Singlet Oxygen

Enhancing the sensitivity and selectivity of chemiluminescence(CL) sensors for detecting chemical species in complex samples posesa significant challenge in nanoparticle surface engineering. Graphiticcarbon nitride (CN) shows promise but suffers from weak CL intensityand unknown luminescence mechanisms. In this study, we propose a nitrogendefect strategy to enhance the CL efficiency of europium-functionalizedgraphitic carbon nitride (Eu-CNNPs). By controlling the dosage ofthe europium modification, we can adjust the nitrogen defect contentto reduce the energy gap and improve the CL performance. Remarkably,Eu-CNNPs with rich nitrogen defects exhibit strong chemiluminescenceemission specifically for singlet oxygen (O-1(2)) without responding to other reactive oxygen species (ROS). Buildingupon this finding, we developed a direct, selective, and sensitiveCL sensing platform for O-1(2) in PM2.5 and monitored O-1(2) production in photosensitizerswithout interference from metal ions. Through extensive experiments,we attribute the O-1(2)-driven CL response to thepresence of abundant nitrogen defects in the CN material, acceleratingelectron transfer and yielding a high generation of O-1(2). Furthermore, chemiluminescence resonance energy transfer(CRET) between (O-1(2))(2)* (O-1(2) dimeric aggregate) and Eu-CNNPs contributes to strongCL emission. This work provides insights into enhancing the CL performanceof CN and offers new possibilities for advancing the practical analysisof nanomaterials using the intriguing mechanism of nitrogen defects.