## 3 Application of AIEgens in the Detection of Pesticide Residues in Fluorescence Sensors
### Detection of pesticides Using Organic Fluorescent Small-Molecule Sensors Based on AIEgens
The reaction of the ester group with CESs increases the carboxyl group's electronegativity, leading to enhanced fluorescence. However, the presence of carbamate pesticides inhibits carboxylesterase 1 (CES1), preventing  
Figure 1: (**a**) Structures of A1-1 and A1-2; (**b**) Fluorescence intensity at emission wavelengths of 446 nm and 593 nm for different water contents. Inset: Fluorescence images at varying water fractions (0%, 20%, 40%, 60%, 80%, and 90%); (**c**) Fluorescence intensity of A1-1 at different pH values at 446 nm and 593 nm. (**l**ex = 365 nm); (**d**) Detection mechanism of A1-1 for OPs. (Reproduced with permission from ref. [27]. copyright 2019 Elsevier). the hydrolysis reaction in A2 and resulting in reduced fluorescence intensity, thus enabling the detection of carbamates (Figure 2c). Probe A2 achieved a limit of detection (LOD) of 27.8 ng/mL for carbamate pesticides, demonstrating its effectiveness and providing a useful method for pesticide detection. [PERSON] et al. synthesized the AIegens-based small-molecule fluorescent probe TPETPy (A3) through a one-step reaction (Figure 3a) [70]. The fluorescence properties of A3 were investigated in THF/H2O mixed solvents with varying water fractions, and its sensing performance for trifuralin was evaluated (Figure 3b,c). The detection mechanism of trifuralin using probe A3 relies on the PET mechanism. Upon ultraviolet light excitation, A3 and trifuralin exhibit well-matched energy levels, facilitating effective electron transfer from the excited-state A3 molecule to the ground-state trifuralin molecule. This electron transfer results in the fluorescence quenching of A3, enabling the detection of trifuralin. Additionally, a smartphone-integrated sensing platform was developed based on A3 for trifuralin detection, which allowed for real-time output of the RGB (red, green, and blue)  
Figure 2: (**a**) Relative absorbance and fluorescence spectra of A2 (10 \(\upmu\)M) in CH3 CN/PBS buffer (\(v/v=1/1\)) at 25 \({}^{\circ}\)C. Inset: Structure of compound A2; (**b**) Fluorescence images of A2 under UV light and daylight; (**c**) Schematic illustration of the binding mechanism for A2 in the detection of carboxylesterases and carbamates. (Reproduced with permission from ref. [69]. copyright 2021 Elsevier). values in the fluorescence mode (Figure 3d). This platform enabled real-time and on-site quantitative monitoring of trifluralin, and its practical applicability was confirmed through standard addition experiments. [PERSON] et al. synthesized the AIE-active small-molecule probe TPS (A4) using benzyl, aniline, and \(p\)-acetamidobenzaldehyde as starting materials (Figure 4c) [71]. A4 exhibits a pronounced AIE effect and demonstrates significant \"turn-on\" and \"color change\" fluorescence responses to paclobutrazol, with a LOD of 9.3 \(\times\) 10\({}^{-8}\) M (Figure 4a,b). The detection mechanism involves the formation of a new aggregation effect when A4 interacts with paclobutrazol through hydrogen bonding, which reduces the energy gap and results in enhanced fluorescence (Figure 4c). To assess the practical applicability of A4 for simple, real-time, and in situ detection of paclobutrazol in agricultural production and daily life, its selective detection capability was evaluated in real sample environments (Figure 4d,e). The results confirmed the high effectiveness of A4, highlighting its potential for practical pesticide detection applications. Figure 3: (**a**) Structure of compound A3; (**b**) PL spectra of A3 in THF/water mixtures with varying water fractions.