Synthesis And Sers Studies Of Noble Metal Nanoparticles With Different Morphologies

The suface plasmon resonance properties(SPR)of noble metal nanoparticles gives them large and controllable absorption and scattering cross section,and the synergistic effect of surface localization and near-field enhancement can be achieved.The field localization and field enhancement properties of noble metal nanoparticles are used to enhance the signal intensity of molecules adsorbed on the surface in surface-enhanced Raman spectroscopy(SERS).These properties are closely related to their morphology,and the synthesis of nanoparticles with specific morphology has always been the focus of research in this field.In this paper,gold nanoparticles with different morphologies were prepared by seed growth method.The extinction spectrum and morphology were characterized,The effects of reaction parameters on the morphology of the particles were analyzed,and the Raman signal enhancement effect of gold nanoparticles with different morphologies as the substrate was studied.The research contents and conclusions include the following points:1)With chloroauric acid as the precursor,gold nanorods with uniform morphology were prepared under the action of the reducing agent ascorbic acid.The influencing factors of AgNO3,seed crystals and cetyltrimethyl ammonium bromide(CTAB)were analyzed.The results show that under different preparation conditions,gold nanorods with uniform morphology,good dispersibility,aspect ratio of 3.8-4.3 were prepared,and longitudinal resonance absorption peak is adjustable between 800-900 nm.2)Gold nanospheres with uniform size were prepared by adding seed crystals into the AgNO3-free reaction system.The influences of seed crystals and ascorbic acid were analyzed.The results show that the uniform gold nanospheres with size of 15.8~27.0 nm having good growth stability were synthesized under different synthesis parameters.3)Gold nanorods with different aspect ratios(3.8 and 4.2)as enhanced substrates,and rhodamine 6G(R6G)and thiram were detected by Raman spectroscopy.The results indicate that the Raman spectrum of these two kinds of substrates to R6 G have strong enhancement ability in the range of 10-7 mol/L~10-4 mol/L under 532 nm excitation,with detection limit of10-7 mol/L.Meanwhile the gold nanorods with small aspect ratio(3.8)show better SERS enhancement effect.Using the excitation wavelength of 785 nm,the two substrates the two substrates obtained different detection concentrations of 10-6 mol/L and 10-5 mol/L under the same test conditions for R6 G.With thiram as the probe molecule,the results show that these two kinds of substrates can detect thiram as low as 10-6 mol/L and 10-5 mol/L respectively,the response range is 10-6 mol/L~10-2 mol/L.4)Gold nanospheres substrates are employed to detect the R6 G,thiram and melamine.The results show that the Raman spectrum of gold nanospheres substrate to R6 G has good enhancement effect in the range of 10-8 mol/L~10-3 mol/L under 532 nm excitation,with the detection limit as low as 10-8 mol/L.Using the excitation wavelength of 785 nm,the detection limit is 10-6 mol/L.With detecting thiram,the limit of detection is 10-9 mol/L and the testing concentration range is 10-9 mol/L~10-2 mol/L,which is far below the maximum residue limit specified in food.The results indicate that the substrate can be applied to the detection of thiram in food.With melamine as the probe molecule,it is found that gold nanospheres can detect melamine as loe as 10-5 mol/L,with testing range is 10-5 mol/L~10-2 mol/L.In the thesis,the combination of the two kinds of substrate and SERS technology can detect probe molecules quickly and sensitively.The SERS enhancement effect of the two kinds of substrate exhibits good signal stability and reproducibility.Future the SERS performance of the substrate can be optimized,the two kinds of substrate could be applied to practical detection of trace substances in food safety,environment and energy areas.