Carbon Dots Detect Water-to-Ice Phase Transition and Act as Alcohol Sensors via Fluorescence Turn-Off/On Mechanism

作者：Sergii Kalytchuk, Lukáš Zdražil, Zdeňěk Baďura, Miroslav Medveď, Michal Langer, Markéta Paloncýová, Giorgio Zoppellaro, Stephen V. Kershaw, Andrey L. Rogach, Michal Otyepka, Radek Zbořil · 发表于：ACS Nano · 年份：2021 · DOI：10.1021/acsnano.0c09781 · 被引用次数：50 · 研究领域：Carbon and Quantum Dots Applications、Advanced biosensing and bioanalysis techniques、Nanocluster Synthesis and Applications

Highly fluorescent carbon nanoparticles called carbon dots (CDs) have been the focus of intense research due to their simple chemical synthesis, nontoxic nature, and broad application potential including optoelectronics, photocatalysis, biomedicine, and energy-related technologies. Although a detailed elucidation of the mechanism of their photoluminescence (PL) remains an unmet challenge, the CDs exhibit robust, reproducible, and environment-sensitive PL signals, enabling us to monitor selected chemical phenomena including phase transitions or detection of ultralow concentrations of molecular species in solution. Herein, we report the PL turn-off/on behavior of aqueous CDs allowing the reversible monitoring of the water-ice phase transition. The bright PL attributable to molecular fluorophores present on the CD surface was quenched by changing the liquid aqueous environment to solid phase (ice). Based on light-induced electron paramagnetic resonance (LEPR) measurements and density functional theory (DFT) calculations, the proposed kinetic model assuming the presence of charge-separated trap states rationalized the observed sensitivity of PL lifetimes to the environment. Importantly, the PL quenching induced by freezing could be suppressed by adding a small amount of alcohols. This was attributed to a high tendency of alcohol to increase its concentration at the CD/solvent interface, as revealed by all-atom molecular dynamics simulations. Based on this behavior, a fluorescence...