TNT sensor based on accumulation layer and effective distance of FRET mechanism with ultra-high sensitivity

Common methods of 2,4,6-trinitrotoluene (TNT) detection are based on direct detection to the concentration of TNT. If TNT can be accumulated first to increase partial concentration near the sensor and detected by sensing materials then, the detection performance can be significantly improved. As we know, fluorescence resonance energy transfer (FRET) is widely used as the sensing mechanism in TNT detection, which has an effective range of 10 nm. Based on this, we built an accumulation layer between sensing materials and TNT within effective range of FRET, where exists a large quantity of amino groups. The Amino groups can adsorb TNT and realize accumulation function. The accumulation and sensing layer played different roles in the detection of TNT based on distinct mechanism. Accumulation layer was realized by forming Meisenheimer complex between TNT and amino groups while sensing layer was realized by FRET. Via both two layers and mechanisms, the sensors achieved ultra-high sensitivity to TNT, with a limit of detection (LOD) of 0.6 nM and a linear range of 1-20 nM. Compared with pure graphene quantum dots (GQDs), the K-SV of sensor in this work to TNT increased for about 14 times. The accumulation-detection path provides an effective method for the measurement of TNT with ultra low concentration.