A dual-mode fluorometric and smartphone-based colorimetric sensor for cyanide detection using tungsten disulfide quantum dots and silver nanoparticles

In this study, tungsten disulfide quantum dots (WS2 QDs) and silver nanoparticles (AgNPs) were applied to establish a dual-mode fluorometric and smartphone-based colorimetric sensor for the determination of cyanide ions (CN-). We indicated that the fluorescence intensity of WS2 QDs was quenched by AgNPs as a result of the inner filter effect (IFE) mechanism. Moreover, the quenched fluorescence intensity of WS2 QDs switched on again in the presence of CN- due to the interaction between AgNPs and CN-, leading to destroy AgNPs, diminishing their yellow color and reducing their IFE on WS2 QDs. Based on these facts, we established a turn-off-on fluorometric (with a range of 0.5-30 and detection limits of 0.17 mu M) and smartphone-based colorimetric sensor (with 5-500 mu M and detection limits of 1.2 mu M) for CN- measurement. The sensor was exploited for CN- analysis in water and food samples with satisfactory results. The established dual sensor benefits from both methods advantages such as the high sensitivity of fluorometric sensors as well as simple and visual detection of smartphone-based colorimetric sensors. Additionally, our developed smartphone-based colorimetric sensor can be used as a portable sensor for the sensitive, rapid and low-cost analysis of CN- in the field.