Orange emissive carbon nanodots for fluorescent and colorimetric bimodal discrimination of Cu2+ and pH.

We have facilely synthesized orange emissive carbon nanodots (O-CDs) via a hydrothermal method using citric acid and 5-aminosalicylic acid. The obtained O-CDs show the excellent characteristics of excitation independence, low toxicity, fabulous photostability and superior biocompatibility. Based on these captivating properties, as-prepared O-CDs have been successfully implemented as a multi-functional sensing platform for fluorescent and colorimetric bimodal recognition of Cu2+ and pH. Upon adding Cu2+, the orange fluorescence of the O-CDs is evidently quenched with a linear range of 0 µM-300 µM, and a detection limit of 28 nM. Additionally, as the pH increases from 7.0 to 10.2, the O-CDs manifest an obvious decrease in orange fluorescence, which shows a pKa value of 8.73 and excellent linearity in the pH range of 8.0-9.2. Appealingly, the laser confocal imaging of O-CD-stained cells demonstrates that the fluctuations of Cu2+ and pH can be visualized in living cells.

Dual-excitation and dual-emission carbon dots for Fe3+ detection, temperature sensing, and lysosome targeting.

Dual-excitation and dual-emission carbon dots (CDs) have been prepared by simple one-step hydrothermal treatment of p-phenylenediamine and 5-aminosalicylic acid. The as-prepared CDs emit bright green fluorescence under excitation at 320-400 nm and bright orange fluorescence under excitation at 490-560 nm. Interestingly, the CDs can be employed as a dual-excitation and dual-emission fluorescent probe for Fe3+ detection in aqueous solution and living cells. Furthermore, the obtained CDs can function as a promising dual-excitation and dual-emission temperature sensor. Additionally, the CDs can be utilized for lysosomal targeting.