Green Synthesis of Ag 2 S Quantum Dots as Sensing Probe: An Optical Sensor for the Detection of Cholesterol

In this study, an environmental‐friendly method of preparation is adopted for the synthesis of NIR emitted Ag 2 S quantum dots (QDs) with bovine serum albumin (BSA) as a functional capping agent. According to the experimental results, the QDs with an average size of 4.5 nm exhibit their emission peak at 820 nm when excited at 420 nm. Furthermore, these QDs are used for the easy and fast detection of cholesterol (Ch) using the fluorescence (FL) spectroscopic method. These Ag 2 S QDs show signs of Ch concentration dependent FL enhancement after Ch‐QD complexation and Ch concentration. These QDs are either unchanged or underwent FL quenching in the presence of other studied analytes. Under the optimal conditions, the selectivity and sensitivity of BSA capped QDs for Ch are found to be significantly higher compared with other bioanalytes. In this case, the limit of detection is determined as 50 × 10 −9 m . Moreover, this assay demonstrated such advantages as cheap affordability, simplicity, and specificity in terms of Ch sensing.