▎ 摘　　要

Whenthe body temperature rises above 40.6 degrees C, heat stressin the cells causes mitochondrial damage. This damage can lead toapoptosis, multiple organ failure, and even death. The dysregulationof SO2 levels in the mitochondria is linked to this heatstress, and its detection may act as an early indicator of heat stroke.Graphene quantum dots (GQDs), a common class of zero-dimensional carbon-basedfluorescent nanomaterials, have shown immense potential as sensoryprobes, and it is a prospective candidate for monitoring SO2 levels in living cells. Herein, we report a combination of a donor-twoacceptor (D2A) red-emissive di-picolinium salt (PPy-Br) and hydroxy-functionalizedgraphene quantum dots (GQDs-OH) as the fluorescence resonance energytransfer (FRET)-based ratiometric sensor for bisulfite ions detectionin aqueous media. The dye-GQD nanoconjugate displays excellent photostabilityand good aqueous dispersibility allowing the monitoring of SO2 levels in living cells during heat stress. The PPy-Br:GQDnanoconjugate is indifferent to a large number of cations, anions,or biologically relevant species and displays a detection limit of36 nM for the solution phase detection of bisulfite. PPy-Br is biocompatiblewith human cell lines and endocytoses into the cells to ensure monitoringof SO2 levels in the mitochondrial milieu. PPy-Br-treatedhuman breast cancer cells displayed a gradual decrease in fluorescenceat temperatures above 40 degrees C, indicating an increase in SO2 levels in heat-stressed cells. The PPy-Br:GQDs sensing conjugateis efficient in the real-time monitoring of intracellular SO2 levels and demonstrates enough prospects for further explorationsas a diagnostic kit for heat stroke monitoring.