Ethanol phase transition: A pivotal factor in pressure-responsive fluorescence modulation of carbon dots

Fluorescent carbon dots (CDs) have garnered considerable attention owing to their distinctive chemical structure and tunable luminescence. Although numerous studies have established the pressure-tunable luminescence properties of CDs, a systematic investigation of ethanol effects on their pressure-induced emission changes has yet to be conducted. In this study, the pressure-responsive behavior of red-emitting carbon dots (R-CDs) dispersed in ethanol as a model system was investigated. We undertake a study on pressure regulation of R-CDs dispersed in ethanol. The current results indicate that across the 0.11–3.05 GPa pressure range where ethanol maintains its liquid phase, R-CDs display opposing pressure responses: carbon core fluorescence enhancement accompanied by surface state emission quenching. When the pressure exceeds 3.05 GPa, ethanol begins to crystallize, leading to aggregation-induced quenching of the overall fluorescence of R-CDs; within the pressure range of 3.05–9.60 GPa, the further compression of ethanol polycrystals results in a significant increase in the aggregation degree of R-CDs, thereby causing a more pronounced quenching effect on their overall fluorescence. This study provides critical insights for optimizing the optical characteristics of CDs and broadening their functional applications.