Piezochromic luminescent materials have shown great potential in advanced optoelectronic applications. However, most of luminescent materials usually undergo emission quenching under external stimuli. Herein, we demonstrate for the first time that the photoluminescence of carbon dots (CDs) confined within sodium hydroxide can be enhanced when high pressure is applied. They exhibit a 1.6-fold fluorescence enhancement compared with pristine CDs. Importantly, the enhanced fluorescence intensity can be retained after the release of pressure to ambient conditions. A combination of experimental analysis and theoretical simulations indicates that such an enhanced emission is mainly attributed to the strong confinement resulting from the sodium hydroxide matrix, which can separate the CDs spatially and restrict the nonradiative pathway. These results provide a rational strategy for manipulating the optical properties of CDs with enhanced and retainable photoluminescence (PL) performance, thus opening up a venue for designing luminescent CDs-based materials.

Phosphorescent carbon nanodots (CNDs) have various attractive properties and potential applications, but it remains a formidable challenge to achieve large-scale phosphorescent CNDs limited by current methods. Herein, a large-scale synthesis method for phosphorescent CNDs has been demonstrated via precursors’ self-exothermic reaction at room temperature. The as-prepared CNDs show fluorescence and phosphorescence property, which are comparable with that synthesized by solvothermal and microwave method. Experimental and computational studies indicate that exotic atom doped sp² hybridized carbon core works as an emissive center, which facilities the intersystem crossing from singlet state to triplet state. The CNDs show phosphorescence with tunable lifetimes from 193 ms to 1.13 s at different temperatures. The demonstration of large-scale synthesis of phosphorescent CNDs at room temperature opens up a new window for room temperature fabrication phosphorescent CNDs.