A hydrothermal route to water-stable luminescent carbon dots as nanosensors for pH and temperature

Carbon dots (CDs) as a class of heavy-metal-free fluorescent nanomaterials has drawn increasing attention in recent years due to their high optical absorptivity, chemical stability, biocompatibility, and low toxicity. Herein, we report a facile method to prepare stable CDs by hydrothermal treatment of glucose (glc) in the presence of glutathione (GSH). With this approach, the formation and the surface passivation of CDs are carried out simultaneously, resulting in intrinsic fluorescence emission. The influence of reaction temperature, reaction time and feed ratio of GSH/glc on the photoluminescence property of CDs is studied. The as-prepared CDs are characterized by UV–Vis, photoluminescence, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscope, from which their structural information and property are interpreted. These CDs may be useful as pH sensors or as versatile nanothermometry devices based on the pronounced temperature dependence of their steady-state fluorescence emission spectra, which changes considerably over the physiological temperature range (15–60 °C).