Research On Methods For Quick Scanning Of Organic Pollutants Based On Nanomaterials

The rapid development of modern industry and agriculture results in increasingly serious problem of environmental pollution, especially organic pollution situation is worrying. On the one hand, the organic compounds are increasing and some persistent organic pollutants （POPs） have long been lacked of effective governance; more importantly, though the existing methods （mainly based on large instruments ）are widely used by the advantage of accuracy,they can not meet the requirements of rapidness, on-field and simpleness because of expensive instrument usage and time-consuming processes. The research on methods for quick scanning of organic pollutants based on nanomaterials is of great significance.This paper selects trinitrotoluene （TNT）, pentachlorophenol （PCP） and polycyclic aromatic hydrocarbons （PAHs） three typical organic pollutants as the research objects to validate quantum dots and TiO₂ NTs based sensors, the mechanism of which is general on the target or intermediate product induced quenching or enhancement of the signal. The nanomaterial application provides a new idea for analysis method development. The specific contents are as follows:（1） Developed a new fluorescence method for TNT detection based on the fluorescence quenching of quantum dots （QDs） by TNT: CdTe QDs were synthesized by hydrothermal method with L-cysteine as the stabilizer. L-cysteine is an electron-rich reagent and TNT is electron-deficient, the two can combine to form Meisenheimer complex. Thus the TNT molecules are closed to the quantum dots, leding to fluorescence quenching because TNT can absorb the electrons of QDs. TNT concentrations are linearly related to the fluorescence quenching efficiency in the range of 1.1×10-9 4.4×10-6 M, with a low detection limit of 1.1 nM, which is lower than the limit level of 0.5 mg/L （2.2μM） in water. The QDs concentration and the reaction time were optimized. Interference experiment and the real sample analysis results show good selectivity and practicability of the method, opening a new perspective in the field of TNT assay.（2） Proposed a direct electrochemiluminescence （ECL） method for quick scanning of PCP using CdTe/TiO₂ NTs/Ti composite electrode. CdTe/TiO₂ NTs/Ti composite electrode was obtained by a simple absorbing procedure. Pentachlorophenol shows a strong enhancing effect on the ECL signal. Under the optimum conditions, the developed sensor allows the linear measurement of pentachlorophenol in a range from 4.0×10-11 to 3.0×10-7 M with a detection limit of 5 pM. Selectivity of the sensor is evaluated by investigating analogs of pentachlorophenol, such as phenol, 1,2-dichlorobenzene （DCB）, 3-chlorophenol （CP）, 2,4,6-trinitrophenol （TNP） and 2,4,6-trichlorophenol （TCP）. The response mechanism is also further discussed and validate by the experiments.（3） Constructed a competitive photoelectronchemical immunoassay for the detection of PAHs. PAH antibodies were covalently conjugated on the TiO₂ NTs, which can generates photocurrent under light irradiation. Gold nanoparticles were coated with HRP and BSA-PAH, acting as the enhancer and competitive antigen, respectively, namely BGNPs. The detecting mechanism is the specific combination of BGNPs to antibodies results in photocurrent increase, but on the contrary, the competitive binding of PAHs restrains that increase. Benzo（a）pyrene （BaP） was selected as the model compound of PAHs. Amplified by the reaction between HRP on gold nanoparticles and H2O₂ in the test solution, the photocurrent intensity of TiO₂ NTs is highly dependent on the competitive binding of BGNPs and BaP molecules. BaP could be linearly quantified over the range of 3.5 nM to 0.35 pM, with a detection limit of 0.11 pM, much lower than the quality criteria （15.1 pM） in drinking water set by US Environment Protection, indicating the proposed immunosensor can be adapted for fast scanning of PAHs.