Fabrication Of 3D SERS Substrates And Their Sensitivity To Organic Pollutants

Surface Enhanced Raman Scattering(SERS)technology is characterized by high sensitivity,rapid response,and fingerprint recognition,having great potential for rapid trace detection of molecules like persistent organic pollutants and drugs.At present,the key to realize the large-scale application of SERS technology is how to fabricate an ideal SERS substrate to obtain the SERS signal with high sensitivity and good signal reproducibility.In this paper,a variety of three dimensional(3D)SERS substrates with high sensitivity and signal uniformity are fabricated,and the performance of the 3D SERS substrates and their applications in rapid trace detection of toxic organic pollutants are systematically investigated.The main research contents and innovations of this thesis are as follows:1.A large-scale ordered ZnO nanorods arrays were prepared by the PS template method,and Ag nanoparticles were uniformly modified on the ZnO nanorods.The arrays have high-density SERS "hot spots",which is beneficial to improve the SERS sensitivity of the substrate.Besides,the chemical enhancement of ZnO combined with the electromagnetic enhancement of Ag nanoparticles,which further improves the SERS activity of the substrate.Ag-nanoparticles@ZnO-nanorods(Ag-NPs@ZnO-NRs)arrays enable the detection of rhodamine 6G(R6G),thiram and methyl parathion with high sensitivity,good signal uniformity and reproducibility.In addition,because of the photocatalytic properties of ZnO,the arrays of Ag-NPs@ZnO-NRs perform self-cleaning properties.The analyte molecules adsorbed on the substrate can be photocatalytically degraded by UV irradiation,indicating that this 3D substrate can be reused in the SERS detection,further reducing the cost.2.A 3D self-supported Ag nanorod arrays were prepared using 3D porous AAO as a template.The 3D self-supported Ag nanorod arrays solved the problem of collapse caused by the large aspect ratio of the vertical nanorods,which reduces the signal uniformity of SERS detection.The vertical and transverse Ag nanorods are interconnected to form a 3D network structure,which in turn forms high-density SERS"hot spots".Therefore,this 3D self-supported Ag nanorod arrays as substrates have excellent SERS sensitivity and can detect R6G at concentrations as low as 10-12 M.The SERS detection of trace organic pesticides thiram and 4-aminothiophenol was achieved with a good linear relationship between the characteristic peak intensity and the logarithm of concentration.The 3D interconnected Ag nanorod arrays have promising applications for the rapid quantitative detection of trace organic pollutants.3.A large-scale ordered arrays of self-supported 3D interconnected porous Au nanorod arrays were fabricated using the 3D porous AAO template.In contrast to the self-supported solid nanorods,the SERS "hot spots" of this 3D porous nanorod array arise not only from the coupled electric fields between the neighboring nanorods,but also from the local electric fields generated at a large number of mesopores smaller than 10 nm in the nanorod distribution,which results in the uniformly distributed 3D "hot spots" over the entire substrate.Besides,the porous Au nanorods have a larger specific surface area than solid Au nanorods,which facilitates the adsorption of target molecules In addition,the transverse nanorods and vertical nanorods are interconnected to form a 3D self-supported array structure,which avoids the collapse of the nanorods and thus improves the stability of the substrate.Therefore,this self-supported 3D interconnected porous Au nanorod array as a SERS substrate exhibits high sensitivity and good signal uniformity,and has great potential for rapid quantitative detection of toxic organic pollutants.4.The Ag nanoparticles modified bacterial nanocellulose(Ag-NPs@BNC)flexible composite structure as SERS substrate was obtained by in situ growth of high-density Ag-NPs on the 3D network of bacterial nanocellulose fibers through the silver mirror reaction,and the density of Ag-NPs was further increased by the volume shrinkage property of BNC.In this structure,a large number of uniformly distributed SERS "hot spots" were generated between the high-density Ag-NPs,so Ag-NPs@BNC has high SERS sensitivity and good signal reproducibility.Moreover,the hydrophilic BNC has good permeability and adsor:ption properties,which can trap the target molecules to the highly active "hot spots" region,thus further enhancing the SERS activity of this substrate.In addition,this substrate exhibits good stability and flexibility under different conditions of SERS detection.Thus,this 3D flexible Ag-NPs@BNC substrate showed promising applications in the rapid detection and analysis of molecules.