Synthesis of Mugwort Leaves-derived Carbon Quantum Dots and Their Application in Intracellular pH Sensing and Imaging

This study advocates the concept of green chemistry and sustainable development. Nitrogen-doped carbon quantum dots (N-CQDs) with blue-green fluorescence were synthesized via a hydrothermal method using mugwort leaves as both carbon and nitrogen sources. Various analytical techniques were used to characterize the optical, electrochemical, stability and pH sensing properties of N-CQDs and undoped CQDs. The as-prepared N-CQDs were further applied as nano-fluorescent probes for intracellular pH sensing and fluorescence imaging. The results demonstrated that nitrogen doping significantly enhanced the quantum yield of N-CQDs to 32.25% (vs. 16.29% for undoped CQDs), induced a red-shifted emission, and endowed N-CQDs with strong fluorescence intensity, favorable excitation-dependent behavior, excellent stability and photoelectric performance. N-CQDs showed sensitive pH response with a good linear relationship between fluorescence intensity and pH in the range of 4.0-8.5, and also exhibited good sensing performance and linear fluorescence response in living cells. With wide detection range and high sensitivity, N-CQDs hold great promise for biomedical applications especially in intracellular pH sensing.