## 3 Application of AIEgens in the Detection of Pesticide Residues in Fluorescence Sensors
### Detection of Pesticides by Nanocomposite Sensors Based on AIEgens  
Combining AIEgens with nanocomposites can utilize the unique fluorescence characteristics of AIEgens and the special properties of nanocomposites to achieve high-sensitivity and high-selectivity pesticide detection [87; 88]. The detection mechanisms of such sensors generally fall into three types: (i) Fluorescence change of AIEgens: When pesticides interact with AIEgens within the nanocomposite, they may alter the aggregation state of AIEgens, leading to changes in fluorescence intensity or wavelength. These changes can be used to quantitatively or qualitatively detect pesticides by monitoring the fluorescence signal. (ii) Nanomaterial properties: Nanocomposites can enhance the fluorescence of AIEgens through various mechanisms. For instance, the surface plasmon resonance effect of metal nanoparticles can amplify AIEgens' fluorescence, while the conductivity of carbon nanomaterials can be utilized in electrochemical sensors. Pesticides are detected by measuring changes in current or potential. (iii) Multiple signal detection: By combining the fluorescence signal of AIEgens with other properties of nanomaterials (such as resistance or capacitance), multiple signal detection can be achieved. This approach improves the accuracy and reliability of pesticide detection. For example, [PERSON] et al. developed the MnO\({}_{2}\)-AuNCs-SiO\({}_{2}\) composite material (A5) through the self-assembly of Au nanoclusters (AuNCs), silica nanoparticles (SiO\({}_{2}\) NPs), and manganese dioxide (MnO\({}_{2}\)) nanosheets (Figure 5a) [72]. This composite was used for dual-mode fluorescence and colorimetric detection of OPs. The detection mechanism involves the electrostatic adsorption of weakly fluorescent **AuNCs** onto the surface of SiO\({}_{2}\), which enhances their AIE properties and amplifies the fluorescence signal. In the presence of alkaline phosphatase (ALP), sodium L-ascorbyl-2-phosphate (AAP) is dephosphorylated to produce ascorbic acid (AA). AA decomposes MnO\({}_{2}\), causing the solution to change from brown to colorless, thereby restoring the fluorescence of AuNCs-SiO\({}_{2}\). When OPs, such as acephate, are present, they inhibit ALP activity, reducing AA production and preventing the complete decomposition of MnO\({}_{2}\). This results in weakened fluorescence recovery and increased absorbance. The practical performance of A5 was demonstrated by applying it to fresh vegetables and test papers for in situ imaging (Figure 5b,c) and visual semi-quantitative detection of OPs, showcasing the significant potential of AIEgens-based nanocomposites for practical applications. [PERSON] et al. synthesized an amphiphilic polymer (PTD) containing AIE-active fluorophores and quaternary ammonium salt groups via free radical copolymerization, which self-assembled into AIE-active nanoparticles (A6) (Figure 6a) [73]. A sensor A6@AuNPs for highly sensitive OP detection was developed using A6 as the fluorescence signal reporter and gold nanoparticles (AuNPs) as the nanoquencher (Figure 6b). Electrostatic interactions between A6 and AuNPs caused FRET, which quenched the fluorescence of A6. In the presence of ATCh, AChE hydrolyzed it to produce thiocholine. Thiocholine then competitively bound to AuNPs, preventing FRET and thereby enhancing fluorescence However, when OPs are present, the activity of AChE is effectively inhibited, resulting in the absence of thiocholine production. The inhibition of AChE activity leads to the obstruction of the FRET effect, and no enhanced fluorescence can be detected, thereby achieving the detection of OPs (Figure 6c). This work advances high-performance AIE nanoparticles and broadens their application scope. [PERSON] et al. prepared a silver cluster (Ag\({}_{24}\), denoted as A7) by combining the AIE-active ligand 1,1,2-triphenyl-1-buten-3-yne (TPBA) with silver ions, which was used to detect ethion among OPs [74]. TPBA exhibits AIE characteristics. Emitting cyan fluorescence in both its aggregated and solid states.