Magnetic Induction Of Noble Metal Composite Microspheres Assembled SERS Substrate And Properties Of Organic Pollutants Detected

In the recent years, with the rapid development of industry and agriculture in China, living environment has been severely damaged, especially industrial and agricultural production waste water into rivers and groundwater which has posed a serious threat to human health and ecosystem. Organic pollutants in water such as pesticides enter into the body through the food chain. Through accumulation will lead to endocrine disorders, reproductive, immune dysfunction and even cancer. So the rapid detection of pesticides in water is imminent. Based on the noble metal nanostructure of the surface enhanced Raman scattering（SERS） technique can quickly obtain organic undamaged "fingerprint" characteristic peaks, it is expected to achieve high sensitivity and rapid detection of pesticide residues in water. Since the structure of the noble metal SERS substrate has a decisive influence on the detection performance, thus design and synthesis around the noble metal nano-structured materials become a research hotspot. Such thiram pesticide molecules for detect objects. Based on Our previous research in this field, we propose to functional magnetic noble metal composite monodisperse microspheres as building block. Firstly, the magnetic composite microspheres were synthesize and used to capture residual pesticide in water. Secondly, it is realized by applying a magnetic field induced assembled on a glass substrate. Finally obtained a uniform film substrate SERS. Pesticide molecules are expected to achieve high sensitivity and reproducibility of probe. To this end, we design and synthesize Fe₃O₄@SiO₂@Ag and Fe₃O₄@SiO₂@TiO₂@Ag monodisperse Composite microspheres from different angles, and its unit is assembled by magnetic induction of assembling to build SERS substrate, then the two kinds of SERS substrate properties were characterized. Preliminary results show that a uniform film based on monodisperse Fe₃O₄@SiO₂@Ag composite microspheres for R6 G and thiram molecules with high sensitivity and reproducibility of detection performance. On this basis, through the introduction of TiO₂ shell（Fe₃O₄@SiO₂@TiO₂@Ag）, by the photocatalytic shell to achieve self-cleaning surface of the composite microspheres and reuse. Specific results are as follows:1. Particle type SERS substrate has the advantage of high sensitivity detection, the film-type SERS substrate has good repeatability, but how to effectively integrate the two advantages becomes current research focus. Monodisperse magnetic composite microspheres induced assembly would be an effective way to achieve a combination of both. Based on this idea, monodisperse magnetic noble metal composite microspheres will be our target,we proposed monodisperse Fe₃O₄ as a core, template-activated strategy toward one-step coating silica colloidal microspheres with sliver, we control and synthesize Fe₃O₄@SiO₂@Ag monodisperse composite microspheres. The introduction of the magnetic core not only pre-dispersed in the solution by separating the capture molecule pesticide easier but also laid the foundation for a magnetic induction of assembly. Experimental results show that the idea can be realized by the rapid assembly of monodisperse microspheres of uniform unit SERS substrate film. Because noble metal microspheres assembly closer to the distance between the particles produced additional active hot spot, so sensitivity is further improved. Furthermore, by SERS substrate obtained by this method can be achieved for molecules in solution pesticide thiram high detection sensitivity, the detection limit can reached 10-8 M, and the position detection signal throughout the different film substrate with good repeatability.2. Based on the monodisperse Fe₃O₄@SiO₂@Ag composite microsphere SERS film can only achieve a single detection of organic molecules. This greatly increased the detection of costs, based on the above findings,we propose the introduction of TiO₂ photocatalytic coating shell in the shell, the use of TiO₂ in the case of UV irradiation of photocatalytic degradation of organic silver shell surface, with self-cleaning function microspheres unit to achieve SERS substrate reuse. Based on this idea, we synthesized monodisperse Fe₃O₄@SiO₂@TiO₂@Ag composite microspheres, and the microspheres assembled building blocks to achieve a uniform film SERS substrate. Experimental results show that the use of the substrate to detect organic molecules R6 G after degradation by UV irradiation and repeated characterization found that the microspheres assembled SERS substrate was still able to detect organic molecules R6 G efficiently, and therefore by introducing light catalytic shell initially realized the development of self-cleaning SERS substrate.