A novel “on-off-on” fluorescent sensor based on TSPP-Ag+ for S2− detection in real samples

As a new fluorescence sensor for S[Formula: see text]detection, TSPP-Ag[Formula: see text]-based “on-off-on” switches were designed. 5,10,15,20-(4-sulphonatophenyl) porphyrin (TSPP) is used as a good fluorescent probe due to its high quantum yield, good water solubility and good biocompatibility. At room temperature, the TSPP releases the optimal fluorescence emission wavelength at 642 nm when the excitation wavelength is set to 515 nm. This indicates the “turn on” mode and the color of the solution demonstrated is pink at this time. The strong fluorescence of TSPP can be firstly quenched by Ag[Formula: see text] as it can chelate with N atoms in the TSPP cavity, which causes the fluorescence intensity to become weak and the color of the solution changes from pink to light green. At this point, the fluorescence signal for the study system is in the “turn-off” state. When S[Formula: see text]are added to the TSPP-Ag[Formula: see text] sensing system, the fluorescence signal is recovered again due to the generation of silver sulfide (Ag 2 S), correspondingly, the solution color changed from light green to yellow-black. At this point, the fluorescence emission for the study system is in the “turn-on” state. Moreover, TSPP-Ag[Formula: see text] showed good selectivity and sensitivity towards S[Formula: see text]than other metal ions, and the limit of detection (LOD) is lowererd to 1.77 [Formula: see text]M, the linear range is 0 - 29.21 [Formula: see text]M. In addition, the concentration of S[Formula: see text]is detected in rabbit serum. Both of the recoveries and RSDs are within satisfactory range, which indicates that the promoted “on-off-on” fluorescent sensor can be applied to detect S[Formula: see text]in real samples.