Dual-channel sensing system for p-nitrophenol based on Rhodamine 6G-Sulfur quantum dots

Based on the biocompatibility and excellent photoluminescence, sulfur quantum dots (SQDs) have been applied to detect metal ions, lactate dehydrogenase, tartrazine and other compounds. But most of the reported sensing SQDs have a single emission, which is greatly affected by external conditions such as sensing environment, photobleaching, and other factors, and then decreasing the accuracy of sensing system, especially for the sensing in real samples. This often requires more accurate and reliable ratio fluorescent detection to overcome these drawbacks based on its self-correction to environmental interference. (86 words).

Herein, Rhodamine 6G modified SQDs (Rho-6G-SQDs) with dual emission at 414 nm and 516 nm were synthesized, which are independent on the excitation wavelength and possess great stability. The emission of Rho-6G-SQDs at 414 nm can be significantly quenched by p-nitrophenol through the static quenching and photoinduced electron transfer, along with a visible color change of solution from blue to green under ultraviolet light. Based on this, a dual-channel sensing system was developed for the ratio fluorescent and colorimetric sensing of p-nitrophenol. The system has a rapid fluorescence response towards p-nitrophenol in the linear range of 0.117-20.0 μM and LOD as 35.6 nM (3σ/k) and colorimetric sensing with the linear correlation up to 200 μM and LOD of 9.90 nM (3σ/k). The sensing application for p-nitrophenol in sewage water sample achieved the spiked recovery from 99.3 % to 110 %. (138 words).

This is the first attempt to prepare fluorescent SQDs using small organic dye molecules as passivators instead of polymers. The developed dual-channel sensing system based on Rho-6G-SQDs provides great convenience for more accurate and effective p-nitrophenol detection in real water samples at low concentrations. (44 words).