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

Abstract

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.