| Surface-enhanced Raman scattering(SERS)spectroscopy,a highly sensitive analytical tool,are widely used in the fields of surface adsorption,biomedical research,environmental science monitoring,chemical and biological sensors,trace detection and analysis.Due to their unique physical and chemical properties,noble metals(such as gold and silver)have drawn great attention in the field of SERS.The composition,structure and size of gold/silver nanomaterials directly affect the SERS properties.It is imperative to develop a novel method to prepare new high Raman-active substrates to improve the sensitivity of detection.In this thesis,we successfully prepared three binary gold/silver-based nanomaterials with different morphologies and compositions by one-step wet chemical method,and deeply investigated the growth mechanism of these materials.These fabricated nanomaterials were employed as the active substrate to construct SERS sensors,eventually achieving highly sensitive detection of common pollutants in the environment.The main content of this thesis are as follows:(1)Controlled synthesis of highly branched gold-palladium alloy nanobrambles and the applications for SERSIn this work,highly branched gold-palladium alloy nanobrambles(Au46Pd54 NBs)were fabricated by a facile,eco-friendly and controlled one-pot aqueous approach,using thymine as the weak stabilizing,capping and structure-directing agents.The synthesized architectures were mainly characterized by scanning electron microscopy(SEM),transmission electron microscopy(TEM),energy dispersive X-ray spectroscopy(EDS),X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS),and their formation mechanism was discussed in some detail.Using crystal violet as the typical Raman probe,the obtained Au46Pd54 NBs displayed superior SERS performance when compared with Au30Pd70 NCs and Au60Pd40 NCs,owing to the unique structure and morphology of Au46Pd54 NBs as well as the synergistic effects between Au and Pd.(2)Controlled synthesis of multi-branched AgPt alloyed nanoflowers and the applications for SERSThe uniform multi-branched AgPt alloyed dendritic nanoflowers(AgPt DNFs)are fabricated with the assistance of 3-aminopyrazine-2-carboxylic acid(Apzc)as a structure-director via a one-pot successive aqueous co-reduction strategy.The formation mechanism of AgPt DNFs is investigated in details.Their morphology,structure,size,and composition are confirmed by a series of characterization technique.The hierarchical nanostructures exhibit strong SERS enhancement and excellent stability by using 4-nitrothiophenolate as a typical Raman probe.The improved SERS performance for 4-nitrothiophenolate is mainly attributed to the synergistic effects between the bimetals,together with the enriched hot spots at the sharp corners and/or edges of the architectures.This synthetic strategy provided a facile and environment-friendly method to prepare other metallic architectures with novel properties.(3)Controlled synthesis of AgPt@Ag core-shell nanoparticles and the applications for SERSThe well-defined bimetallic AgPt@Ag core-shell nanoparticles(AgPt@Ag NPs)were prepared by a seed-less and template-free wet-chemical method,using poly(ethylene imine)(PEI)as the shape-directing and stabilizing agents.The concentration of PEI played the key role in the current synthesis.The obtained AgPt@Ag NPs exhibited superior SERS enhancement for 4-mercaptopyridine with the enhancement factor(EF)of 5.0×107and a low detection limit of 0.008 ?M(S/N=3),coupled with the significant SERS enhancement for the other Raman probes(e.g.4-nitrothiophenolate,4-mercaptobenzoic acid,and 4-mercaptophenylboronic acid).AgPt@Ag NPs can be employed as a promising candidate for in-situ SERS determination of trace analytes in environment,food and even clinical analysis.The dramatically improved SERS performances were mainly attributed to the specific core-shell structures and electromagnetic coupling effects between the bimetallic AgPt alloyed core and the Ag shell. |
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