Preparation Of Water-dispersed Semiconductor Nanomaterials And Its Application On Pesticide Residues Detection

Semiconductor nanomaterials, with unique physical, chemical, and optical properties, are now emerging as a revolutionary means for imaging and optical detection and achieving more and more attention in many scopes. In our paper, we prepared Mn doped ZnOxS1-x QDs, Te nanowires and so on, and discussed the pesticide residue detecting potential application value. The main contents were as follows:1. The interaction between TGA-CdTe QDs and protamine sulfate was investigated. The results showed that the fluorescent intensity of CdTe QDs decreased when the concentration of protamine sulfate increased. The fluorescence quenching constant (Ksv), thermodynamics enthalpy change (△Hθ), standard entropy change (△Sθ) and free energy change (△Gθ) of the process at291K,298K and305K were acquired by analysing Stern-Volmer equation and thermodynamics equations. The mechanism of the combining process was studied by UV-vis spectrum, fluorescent lifetime and Zeta surface potential, which showed that the fluorescent quenching process of the system is dynamic and spontaneous electrostatic interaction. The results demonstrated that CdTe QDs with surface positive charged could be synthesized, which showed potential application value for detecting organophosphorus pesticide-chlorpyrifos-methyl.2. Water-soluble Mn-doped ZnOxS1-x QDs was prepared in nitrogen atmospheric conditions with one-step synthetic route using ZnNO3·6H2O、MnCl2·4H2O and Na2S as starting material. The as-prepared products were characterized by XRD, UV-vis, FL, HRTEM and Raman spectrum. The result showed that, the size of the QDs is about3.2±0.7mm, and the doped QDs have two distinct emission bands:the defect-related emission and the Mn-related emission, which exhibit a competing process. A good FL signal of the transition of Mn (4T1-6A1) is observed when the doping amounts are1.0%and20%respectively. The as-prepared solutions are stable for more than six months at4℃. Manganese emerges in the form of rivalent manganese (Mn+)(ZnMn2O4/MnO(OH)-ZnSxO1-x), which is the intermediate of the reaction. This method has the advantages of good stability and environment-friendly stabilizer, for involving no heavy metal ions or toxic reagents. At the same time, when the dBSA modifies the surface of QDs, the sample will improve Raman signals at the wavelength band of1054cm-1indicating that this material possesses the potential SERS activity and can be used as SERS material in the future. 3. We developed convenient method synthesizing uniform nanowires of hexagonal Te from3.3nm CdTe QDs using EDTA as shape controller under hydrothermal condition. The nanowires exhibited noticeable variance while increasing the concentration of EDTA, the product possesses excellent morphology and good monodispersity in solution. The images of TEM and SEM suggested that the uniform and long nanowires with high aspect ratios were obtained, with an average diameter of30nm, and lengths up to micrometer scale, when the concentration of EDTA was0.10g/L. However, the maximum content of Te in nanowires emerged when the concentration of EDTA was0.5g/L. Based on above results, we further translated it into high SERS activity of Ag2Te nanowires and studied the SERS effect when the surface of the nanowires modified with the pestcide of emamectin benzoate and atrazine, respectively, which showed potential application value.