The Research Of Biomoleculars Functionalized Nanomaterials In Heavy Metals Micropollutants Trace Analysis

Heavy metal contaminations have been becoming one of the most challenging environment problems in the21st century. With the highly developed industrializing and the urban sprawling,Heavy metal pollution problems have worsened continuously. At present heavy metal pollution has severely threatened ecological environment,food safety,public health and human survival environment in our country.Thereby, it is no time to delay that looking for effect means to heavy metal solve pollution.Carring out the rapid and trace detection of heavy metal ion provide a powerful guarantee for the effective preventing and administering for heavy metal pollution. In recent years, with the rapid development of nanosicience, nano-technology and nanomaterials are more and more used to the actual environmental analysis experiment and bring the new vitality for detection of heavy metal pollutants. In this paper,the gold nanoparticles/graphene (AuNPs/rGO) heterojunction SERS active substrates and luminescent quantum dots nanomaterials were successfully synthesized.The prepared nanomaterials were functionalized by biomolecules for trace optical detection of mercury and arsenic in water.The main contents can be summarized as follows:(1) We chose improved Hummers method that using concentrated sulfuric acid, sodium nitrate and potassium permanganate etal powerfull oxidants for flake graphite oxidation alternately.This can connecte a lot of oxygen containing functional groups on the surface of graphite to get highly oxidized graphite.Then we can get monolayer graphene oxide (GO).after ultrasonic and centrifugal which was then coated onto SiO2surface. The synthesized monolayer graphene oxide was characterized by ultraviolet-visible spectroscopy, atomic force microscopy, scanning electron microscope, optical microscope, Raman spectra, XPS and IR methods. Results show that the GO synthetized by the modified Hummers method with0.8nm thickness was monolayer graphene oxide,and was successfully self-assmblied onto SiO2surface.(2) The rGO film substrates are achieved by reducing the GO substrate in a hydrazine vapor environment,then based on the seed-assisted growth methods, we have developed high performance gold nanoparticles/graphene (AuNPs/rGO) heterojunction SERS active substrates via the gold nanoparticles in-situ direct growth onto the surface of reduced graphene oxide (rGO) substrates. SEM and optical images reveal that AuNPs can be densely and uniformly grown on the rGO substrates. In control experiments, the four substrates (SiO2/Si, rGO/SiO2/Si, AuNPs/SiO2/Si and AuNPs/rGO) were designed to characterizate common Raman probe molecule,it prove that the AuNPs/rGO/SiO2/Si heterojunctions substrate can be used as an effective SERS substrate. At last, we utilized two noncomplementary probes (Probe A: SH-A10-GCT TTG CTT ACT TCG; and Probe B:TAMRA-CGT TGT TTG CTT TGC). As mentioned in experimental details, using DNA probe A can be immobilized on the AuNPs/rGO/SiO2/Si heterojunctions substrates by strong interaction between SH and Au, the SERS labels TAMRA tagged probe B can be binded to the heterojunctions substrates via T-Hg2+-T. We can indirectly detect mercury ions by characterization of Raman probe molecules. This mothed displays ultrasensitivity (0.1nM or20ppt) and high selectivity.(3) Three different stabilizer (reductive glutathione, L-cysteine, mercaptopropi-onic acid) modified quantum dots were synthesized by aqueous phase method. We can get the QDs solution by first added the NaHTe precursor to the cadmium ion and corresponding stabilizers mixture with appropriate pH value and then heated reflux for a period of time to let CdTe nucleation growth.Fluorescence properties of these QDs can be observated by ultraviolet, fluorescence spectrum.The experimental results show that response of trivalent arsenic by glutathione modified quantum dots is the most sensitive. Finally through influence on fluorescence intensity of QDs by different pH buffer, different concentration of quantum dots, different reaction time,we know that GSH QDs are stable in alkaline conditions,and when the quantum dots within the certain concentration range, the fluorescence intensity and the concentration of the quantum dots show good linear relationship, and the quenching of quantum dot As (Ⅲ) need a period of time. Thus we obtained the most suitable experiment condition for the As (Ⅲ) detection, the optimized conditions with15μM of quantum dots in the pH value of7.4of Tris buffer for30min for As (Ⅲ) response.This reaction system showed good selectivity to As (Ⅲ), and the detection limit is7.5ppb.