Construction And Detection Performance Of Ag-based Composite SERS Substrates

Owing to the characteristic localized surface plasmon resonance（LSPR）properties of Ag nanocrystals,a variety of Ag-based SERS sensors were prepared by constructing nanogaps,optimizing morphology and combining molecular imprinting technique（MIT）in this dissertation.In addition,the enhancement mechanism of SERS and the application value of substrate were evaluated with three-dimensional finite difference time domain（FDTD）simulation.The main contents for this thesis are listed as follows:（1）A multi-hot spot magnetic microsphere has been designed and a simple and rapid SERS based detection method of trace amounts of phenolic estrogen has been proposed.As a result of the coupling reaction,there is the formation of strong SERS activity of azo compound.the detection limits are as low as 0.2×10^-4 mol/L for bisphenol A（BPA）.This method is universal because certain phenolic estrogens produce a specific azo compound by coupling reaction.Therefore,the use of this method is applicable for the testing of phenolic hormones through coupling reactions,and the investigation of other phenolic molecules.（2）In this work,a molecularly imprinted polymers（MIPs）-based SERS sensor for selective,sensitive,quantitative and recyclable detection of paclobutrazol residue in complex environments has been proposed.In this strategy,nanocomposites with tunable nanogaps are constructed.Then by tuning the nanogaps and investigating the SERS enhancement mechanism,we achieve the optimal SERS substrates.After combination with MIPs,we can selectively detect the paclobutrazol in soil with a detection limit of 0.075μg/g.When the paclobutrazol concentration ranges from 0.075 to 12.75μg/g,the SERS intensity shows linear correlation,which opens the possibility in quantitative detection.（3）Combining two-dimensional nanoarray and molecular imprinting technology,a highly ordered MIPs-based SERS substrate has been prepared.Firstly,silver cap nanoarrays with different nanogaps are prepared by controlling the etching time of polystyrene nanoarrays.Combined with FDTD simulation,the substrate with the highest SERS activity is selected and the molecularly imprinted polymer is polymerized on its surface.Finally,the sensitive detection of benzopyrene as low as 10^-11mol/L is achieved.The substrate with good signal reproducibility,sensitivity,specificity,and reusability is expected to expand the application range of SERS in practice.