Functionalized Fluorescent Nanodots for Discrimination of Nitroaromatic Compounds

Multiplexing the sensor array can save the time and sensor elements in detection of various unknowns. However, sometimes, that method compromises the sensitivity of a sensor system. Alternatively, a sequential on-off strategy can be applied in a sensor array to enhance the sensitivity. In this strategy, instead of separating individual sensor elements, sequential addition of quenching and masking agents to the pre-established sensor array can enhance the signal output information, sensitivity, and classification accuracy. Herein, three different quantum dots, that is, gold nanoclusters (AuNCs), MoS2 quantum dots (MQD) and WS2 quantum dots (WQD) were used as fluorescent receptors for the sensing of nitroaromatic compounds. These electron-rich quantum dots with versatile surface property provide an array based on the quenching efficiency of nitroaromatic compounds. By using standard array-based sensing, we were not able to classify a large number of nitroaromatic compounds, whereas 100% classification was achieved by employing the suitable surface functionality and sequential on-off strategy. Furthermore, we have studied the mechanism of sequential sensing. According to the optical study, the primary inner-filter effect plays an important role in the quenching of fluorescence intensity of quantum dots. Fluorescence lifetime measurement suggests that AuNCs exhibit the dynamic mode of quenching and transition-metal dichalcogenide quantum dots (MQD and WQD) exhibit the static mode of quenching. This developed methodology can be extended to sensing of other analytes.