Multi-purpose nitrogen and phosphorous codoped carbon nanodots for fluorescence-based sensing and bioimaging

A single-step, straightforward hydrothermal method is put forward to synthesize multi-purpose nitrogen and phosphorous co-doped carbon nanodots (N,P-CNDs). Endowed with excellent water-solubility, chemical, and optical stability, the synthesized CΝDs showed high prospects for utilization in chemical and physicochemical probing and bioimaging. Specifically, the CNDs were successfully applied as a pH and benzophenone-1 probe with satisfactory precision and accuracy, as well as to assess the activity of urease. The fluorescence intensity of CNDs decreases linearly with the pH rising within the range of 3.0–12.0. Based on the benzophenone-induced fluorescence quenching of the CNDs, an acceptable linear regression for detecting benzophenone-1 was achieved over the concentration range of 1.7–76 μM. Furthermore, the synthesized CNDs demonstrated exceptional potential for cell imaging, especially by selectively labeling cell nuclei. Capitalizing on the bioimaging capabilities and pH-sensing properties of the CNDs, we developed an integrated system for intracellular pH monitoring, which can enable improved understanding of cellular processes. This versatile system opens up new opportunities for the application of CNDs in sensing various chemical and physicochemical parameters, thereby expanding the horizons of their utilization in diverse fields. The fact that the synthesized CNDs exhibit all the above capabilities enables the development of a multi-purpose probing system. The findings of this study contribute to the expanding body of knowledge of CNDs applications, whereas the CNDs can be used in diverse fields, such as environmental monitoring and analysis, as well as in biological and medical research. To date, there have been reports about the endocrine-disrupting properties of benzophenones and their bioaccumulation in human tissues, genotoxicity, etc. Despite the importance in their detection, the number of analytical methods developed for the analysis of benzophenones is limited. In this study, the development of a fluorescence probe for the sensitive and selective determination of benzophenone-1 is described. Moreover, the developed carbon dots could also serve as a pH probe. This property was utilized for monitoring cellular pH changes, which may alter due to environmental conditions. Benzophenones have raised concerns due to their reported endocrine-disrupting properties, bioaccumulation in human tissues, and genotoxicity. Addressing the gap of limited analytical methods, our study focuses on the development of a highly sensitive and selective fluorescence probe for the determination of benzophenone-1. By successfully synthesizing carbon dots with unique optical properties, we not only enable the detection of benzophenone-1 but also harness the pH-sensing capabilities of these carbon dots. This dual functionality allows the monitoring of cellular pH changes, which can be influenced by environmental conditions. Through our research, we provide a valuable tool for the detection of benzophenones and pH monitoring, thereby supporting efforts towards environmental monitoring and risk assessment.