Controlled Synthesis Of Gold Silver Nanomaterials And Their Applications In Surface Enhanced Raman Spectroscopy Detection

Surface enhanced Raman spectroscopy (SERS) is one kind ofultrasensitive fast general analytical tool, exhibits intensive applicationprospects in environment monitoring, biological medicine, food safety etc.In the course of real SERS application, one main obstacle is to lack one kindof high efficient, flexible method to prepare high stable SERS substrates viarepeatable, large-scale means. With fast development of modernnanotechnology, it has become possible to synthesize large scale, highsensitive, repeatable SERS substrates. In the thesis, we established threekinds of controllably synthesized gold silver nanomaterials and used thosesynthesized nanomaterials for ultrasensitive SERS detection. Main contentsand results are as follows: (1) The first system is to synthesize hollow silver microsphere withnanoscale surface roughness by using streptococcus thermophiles andEscherichia coli as templates under the condition of no surfactants. Scanningelectron microscope (SEM), atomic force microscopy (AFM), transmissionelectron microscopy (TEM), dynamic light scattering (DLS) were used tocharacterize the size, morphology and microstructure of the silvermicrospheres. Using thermogravimetric analysis (TGA), infraredspectroscopy and X-ray diffraction (XRD) to further analyze the surfacechemical composition of silver microspheres. The performance of hollowsilver microspheres used in SERS research indicates its SERS enhancementfactor effect reached1011, making it one kind of novel highly efficient SERSsubstrate to own the great prospects in the biomedical environment detection.(2) The second system is to self-assembly gold nanoparticles to thesurface of solid silver microspheres as highly efficient3D SERS substrates.The3D silver microspheres (AgMSs) were synthesized by a simple one-stepmethod in aqueous phase at room temperature without surfactants.Successfully self-assembling of gold nanoparticles and solid silvermicrospheres was verified by SEM, DLS and UV. The performance ofprepared gold silver compound microspheres used in SERS researchindicates its higher SERS enhancement effect compared with generalAgMSs SERS substrate, showing this novel method is also suitable for othernanomaterials self-assembly, prepared self-assembly nanomaterials own potential in applications such as SERS detection, catalysis and photo-electricdevices.(3) The third system is to prepare gold-silver core-shell nanorods SERSprobe by using gold nanorods as template, and ascorbic acid as reducingreagent, and adding AgNO3at room temperature, which was used forultrasensitive detection of mercuric ion. The thickness of silver layer on thegold-silver core-shell nanorods (Au@AgNRs) were controlled by usingdifferent concentration of AgNO3. TEM, DLS and UV verified successfullycontrolled synthesis of Au@AgNRs. The self-assembled materials had highSERS sensitivity and selectivity, which could be used as an ideal Hg2+detection probe for SERS detection. The Hg2+detection limit of this methodis1pM. Compared with traditional Hg2+detection methods, it exhibitedhigher sensitivity with three orders of magnitude. Sufficient experiment datasuggest that, it can be used as a novel SERS probe for detection of extremelylow concentrations of Hg2+in biomedical environment detection..(4) The fourth system is to prepare anti-EGFR antibody conjugatedAu@Ag NRs, which was used as SERS probes for targeted detection ofbreast cancer cells. Upon bovine serum albumin (BSA) was conjugated toAu@Ag NRs, the BSA modified Au@Ag NRs exhibited enhancedbiological safety. BSA could be activated by using carbodiimide (EDC)followed by covalent coupling of the epidermal growth factor (EGFR) monoclonal antibody, resultant anti-EGFR antibody conjugated Au@AgNRs were used as SERS probes, which could target breast cancer cells withEGFR overexpression. The method is applicable to SERS targeted detectionfor EGFR overexpressed cancer cells.