| Due to the broad-spectrum insecticidal activity, organophosphorus pesticides (OPs) are widely used in agriculture for pest control. However, their toxic residuals in environment and food supplies would cause the disfunction of neurotransmitter enzyme, acetylcholinesterase (AChE), and thus harm the human health. Therefore, for the purposes of environmental protection and human health safety, it is necessary to restrict the recommend level of OPs and at the same time develop sensitive and portable device to monitor OPs infield. Traditional analytical methods such as GC-MS and LC-MS/MS are powerful tools to offer high sensitivity and specificity for simultaneous determination of multiple OP analogues. However, the associated high-costs, complicated sample pre-treatment processes, and time-consuming labor requirements impede their further applications in field-screening scenarios. In the current stage, there remains an urgent need for the development of OPs assay method which could satisfy the demand of point-of-care (POC) analysis. To solve this problem, a photoelectrochemical (PEC) method and a fluorescent/colorimetric dual readout method were developed herein, which both posses the advantages of easily minized instrument, high sensitivity, and low cost. Detailed work is described as follows:1. The synthesis and characterization of triphenylamine (TPA) functional dyes and their application for PEC sensing of OPsA series of TPA functional dyes, including TTA、 TCA、 T(TA)2、 TDA and T(DA)2 were synthesized, characterized, and employed for the fabrication of PEC sensors for OP detection. As characterized by NMR, MS, and PEC methods, all these TPA molecules possessed a typical D-π-A structure, could transfer photoelectron to the TiO2 nanoparticle modified electrode under the irradiation of visible light, and exhibited high PEC catalytic activity towards the oxidation of thiocholine, the enzymatic hydrolysis product of AChE. In comparison, the T(TA)2 which involved a thiophene group in both arms had the strongest affinity to TiO2 and the highest catalytic activity towards the PEC oxidation of thiocholine. Thus, it was employed to assemble with TiO2 for the fabrication of PEC biosensors for OPs detection. Under optimal conditions, the PEC sensor showed good analytical performance towards the detection of parathion, a typical OP with high toxicity, with a wide linear range from 1.0x10-11 to 4.0x10-6 g?ml-1 and a low limit of detection of 1.0x10-11 g?mL-1. In addition, as proved by both experimental methods and theoretical calculations, the high hydrophobicity the T(TA)2 possessed was regarded as the possible reason influencing the stability and catalytic activity of the molecule on TiO2 interface.2. The synthesis of squaraine molecule and its application for fluorescent/colorimetric dual readout sensing of OPs.A squaraine molecule was synthesized and applied for the fluorescent/colorimetric dual readout sensing of OPs. As characterized by UV-vis spectra and fluorescent spectra, the as-synthesized squaraine molecule showed a high molar extinction coefficient at 620 nm and a strong emission at 646 nm. In addition, it could recognize TCh via a typical blue to colorless color change and a significant fluorescence quenching, which was originated from the addition reaction between squaraine and TCh and the corresponding destroy of the conjugated-structure. Because of the specific property, it was integrated with AChE and used for the fluorescent/colorimetric dual readout sensing of parathion. Under optimal conditions, the sensor with fluorescence as signal readout showed a low limit (LOD) of detection of 4.0x10-7 g?mL-1, and the one with the color change as signal readout showed a LOD of 7.2x10-6 g?mL-1. It should be noted that both the LODs are comparable to the national criterion for OPs analysis, which indicated the practical application potential of the method. |
PDF Full Text Request