A facile synthesis of long-wavelength emission nitrogen-doped carbon dots for intracellular pH variation and hypochlorite sensing

Abstract

Intracellular pH and hypochlorite (ClO⁻) concentration play an important role in life activities, so there is an urgent need to develop a valid strategy to monitor pH and ClO⁻ in biological systems with high sensitivity and specificity. In this study, we report long-wavelength emission nitrogen-doped carbon dots (N-CDs) and their potential applications in intracellular pH variation, ClO⁻ sensing and cell imaging. The N-CDs were prepared via a facile one-pot hydrothermal method of neutral red (NR) and glutamine (Gln). N-CDs exhibited a pH-sensitive response in the range of 4.0–9.0 and a good linear relationship in the range of 5.6–7.4, which indicated that N-CDs are an ideal agent for monitoring pH fluctuations in living cells. In addition, ClO⁻ was capable of reducing the photoluminescence of N-CDs based on static quenching. The linear range is 1.5–112.5 μM and 112.5–187.5 μM, and the LOD is 0.27 μM. Besides, the as-fabricated N-CDs have been smoothly achieved to monitor pH and ClO⁻ in PC-12 living cells due to their great biocompatibility and lower cytotoxicity, demonstrating their promising applications in the biomedical field. Compared with other CD-based methods, the as-proposed N-CDs have a longer fluorescence emission, which makes them potentially valuable in biological systems. The results pave a way towards the construction of long-wavelength carbon-based nanomaterials for fluorescence sensing and cell imaging.