## 3 Application of AIEgens in the Detection of Pesticide Residues in Fluorescence Sensors
### Detection of Pesticides by Nanocomposite Sensors Based on AIEgens
The cluster A7 consists of twelve TPBA ligands, eight tert-butylthiol ligands, and two encapsulated NO ions (Figure 7a). The presence of sulfur in OPs, such as ethion, can effectively disrupt A7 and release the AIE-active fragments. This disruption leads to a \"turn-on\" fluorescence emission change, enabling the successful detection of ethion (Figure 7b). A7 demonstrated high selectivity for ethion, with a LOD of 0.96 mmol/L. Figure 5: (**a**) Schematic illustration of the detection mechanism for OPs using A5; (**b**) Visible imaging of acephate at various concentrations on the surface of fresh cabbage; (**c**) Color changes on A5 test paper [i] and in an A5 solution in a tube [ii] at different acephate concentrations, with the presence of ALP and AAP. (Reproduced with permission from ref. [72]. copyright 2020 Elsevier). [PERSON] et al. developed a fluorescent sensor (TPE-SiO\({}_{2}\)-MnO\({}_{2}\), denoted as A8) for OP detection, combining tetraphenylethylene derivative (BSPOTPE), SiO\({}_{2}\) nanoparticles (SiO\({}_{2}\) NPs), and MnO\({}_{2}\) nanosheets (Figure 8a) [75]. BSPOTPE and SiO\({}_{2}\) NPs, being oppositely charged, form a stable electrostatic assembly and emit strong fluorescence. However, the presence of MnO\({}_{2}\) nanosheets quenches the fluorescence of the BSPOTPE-SiO\({}_{2}\) nanocomposites. When thiocholine (Tch) is present, it decomposes the MnO\({}_{2}\) nanosheets, restoring the fluorescence of the BSPOTPE-SiO\({}_{2}\) nanocomposites. This interaction enables the detection of OPs through their inhibitory effect on AChE, which is translated into a \"turn-off\" fluorescence signal. To streamline the detection process, the researchers also created a fluorescent test strip for OP measurement (Figure 8b). This \"switchable\" fluorescent sensor shows great potential for in-situ and field inspections. Figure 6: (**a**) Schematic representation of A6 fabrication through the self-assembling strategy; (**b**) Schematic illustration of the interaction between A6 and AuNPs; (**c**) Schematic of A6@AuNPs biosensors for highly sensitive detection of AChE and OPs. (Reproduced with permission from ref. [73]. copyright 2019 American Chemical Society). [PERSON] et al. developed a TPE-based AIE star polymer (TPE-Pn), with the optimized polymer TPE-P50 (A9) being utilized as a multifunctional nanocarrier for simultaneous delivery of the pesticide dinotefuran (DIN) and double-stranded RNA (dsRNA) [28]. The A9 polymer features a TPE core, which is hydrophobic, and poly(2-(dimethylamino) ethyl methacrylate) (PDMAEMA) arms, which are hydrophilic (Figure 9a). The positively charged PDMAEMA arms facilitate the formation of hydrogen bonds and electrostatic interactions with DIN and dsRNA, resulting in the dsRNA/DIN/A9 complex (Figure 9b). The combination of the twisted TPE core and the positively charged PDMAEMA arms enhances the encapsulation of DIN and dsRNA, significantly improving the co-loading efficiency of these agents. This complex effectively facilitates the uptake and delivery of DIN and dsRNA to target pests, resulting in enhanced pest control. The loading efficiency of DIN using A9 was increased by 28% compared to commercial pesticides. By incorporating AIEgens, this approach not only improves the co-delivery efficiency of the drug and genetic material but also provides a new strategy for synergistic pest control, overcoming the limitations of traditional chemical and genetic insecticides. Figure 7: **(a)** The structure and coordination mode of the A7 cluster; **(b)** Proposed mechanism for the interaction between A7 and ethion. (Reproduced with permission from ref. [74]. copyright 2021 Chinese Chemical Society). All the aforementioned studies utilize fluorescent sensors designed with AIE molecules and nanomaterials that possess unique properties, such as AIE polymers, nanocomposites, and silver clusters. By utilizing various mechanisms--including AIE characteristics, FRET, IFE, and enzymatic reactions--these sensors achieve highly sensitive and selective detection or imaging of pesticides.