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Preparation Of Core-Shell SERS Substrates And Their Application In Detecting Trace Pesticide Residue

Posted on:2011-09-06Degree:MasterType:Thesis
Country:ChinaCandidate:J J LuFull Text:PDF
GTID:2121360305972878Subject:Physical chemistry
Abstract/Summary:PDF Full Text Request
It is an important international concerned research to detect trace persistent organic pollutants (POPs). Core-shell structures are composed of nuclears and shells, whose physical and chemical properties have been well-improved comparing to single component. Due to high sensitivity, surface-enhanced Raman spectroscopy (SERS) is used to detect trace substances widespread.In our study, we focused on the preparation and application of SERS substrates (SiO2@Au, SiO2@Au and Ag@C@Ag core-shell structure), and developed a simple and efficient method to detect trace pesticide residue. Noble metal Au, Ag, Cu and Pt have the SERS effects, in which Au and Ag are the best. When SiO2 nanospheres as nuclears, noble metals Au and Ag were coated on their surfaces, forming SiO2@Au, SiO2@Ag core-shell nanoparticles. Based on research of preparation of carbon nanosphere in our lab, the method of synthesis of Ag@C nanoparticles were improved and the sizes of Ag@C nanoparticles were smaller than carbon nanosphers. Ag@C@Ag core-shell nanostructures were also synthesized. The trace pesticide residue methyl-parathion was detected using SERS.The main contents and results of the work are as follows:(1) Using SiO2 nanosphere as the support body the effects on the morphology of SiO2 nanosphere were discussed in the paper. Herein the surfaces of SiO2 were modified with-SH of MPTES and amomproply groups of APTES respectively. In the system of PVP adding Ag(NH3)2+ solution, Ag+ ions interacted with-SH and were absorbed on the surfaces of SiO2 nanospheres. The absorbed Ag+ ions were reduced to Ag nanoparticles by PVP, forming SiO2@Ag core-shell nanoparticles. Au nanoparticles interacted with aminopropyl groups and were absorbed on the surface of SiO2. Adding HAuCl4 and citrate sodium into the reaction solution, the absorbed Au nanoparticles on the surfaces of SiO2 growed up, then the SiO2@Au core-shell nanoparticles were formed. The effects on the morphologies of SiO2, SiO2@Au and SiO2@Ag were discussed. The properties and morphologies of particles were investigated by scanning electron microscopy(SEM), transmission electron microscopy(TEM), FI-IR, XRD, XPS.(2) Preparation of Ag@C nanoparticle and Ag@C@Ag core-shell nanoparticles. Ag@C nanoparticles were also modified with-SH of MPTES. Adding Ag(NH3)2+ solution, Ag+ ions interacted with-SH and were absorbed on the surfaces of Ag@C nanospheres. The absorbed Ag+ ions were reduced by PVP and Ag@C@Ag core-shell nanoparticles formed. The properties and morphologies of particles were investigated by SEM, TEM.(3) SERS was used to detect trace pesticide residue methyl-parathion. Due to interactions between the amido groups of L-cysteine and the nitryl groups of methyl-parathion and interactions between the-SH and carboxyl groups of L-cysteine and metals, SiO2@Ag,SiO2@Au,Ag@C@Ag core-shell structures were modified by L-cysteine, forming sensitive monolayers on the core-shell substrates to capture target molecule methyl-parathion.
Keywords/Search Tags:Core-Shell substrate, Surface-Enhanced Raman Spectroscopy (SERS), Methyl-parathion
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