A small molecule fluorescent probe for mercury ion analysis in broad low pH range: Spectral, optical mechanism and application studies

Development of new fluorescent probes for mercury ion analysis in environmental or living organism is undergoing quick growth due to its detrimental toxicity to environmental safety, ecological security, and human being. However, in most cases, the industrial waste water is acidic whereas it remains a great challenge to real-time monitor mercury ion directly at low pH using small molecule fluorescence probe. In this study, we have successfully designed and synthesized the Naph (1, 8-Naphthalimide derivative) -based small molecule probe termed as Naph-NSS capable of monitoring mercury ion in a broad range at low pH (from 2.0 to 7.0). The solid spectral studies demonstrated the high sensitivity and selectivity of the probe towards mercury ion among various species. After binding with Hg2+, the fluorescence of Naph-NSS greatly enhanced, and the mechanism of which was investigated by DFT studies. The probe was able to be loaded on paper strip for instant and fast detection of mercury ions. In addition, the probe is also suitable for detection of mercury ion in environmental samples, living cells and in vivo.