Synthesis Of Nano-metal Colloids And Surface Spectroscopy Study On These Colloids

Metal colloids, employed as the high efficient substrates in the field of surface spectroscopy, especially in the field of the rapid development of the surface-enhanced Raman spectroscopy, their preparation, as well as the study of their optical characteristic, have always been the focal research program. Biology molecules, especially dye molecules(such as the series of Rodamine laser dyes), because of their strong fluorescence and low solvency in water, normal Raman (NR) technique can not obtain their perfect Raman spectrum. The NIR-SERS technique , combined SERS with FT-Raman, due to the advantages such as high sensity, a little amount of sample and quenching fluorescence, should be the best detective way to obtain the perfect Raman spectrum of those above molecules.We reported UV-visible-NIR light absorption properties of silver colloid, employed as the substrate in SERS(surface-enhanced Raman spectra), under various conditions. Experimental results revealed that the new absorption band in the longer wavelength region was related with chemisorption of molecules on colloidal silver surface. When the chemisorption occurred, this new band would appear. Once the molecules were desorbed from silver surface, it could not been observed. We infered that this new absorption band was associated with the effect of charge-transfer transition between adsorbates and colloidal silver particles, not the effect of the surface plasma resonance due to the silver particles aggregation which was usually attributed to in previous research work.In this thesis the preparation of "chemically pure" metal colloids by Nd: YAG laser ablation of metal plate is introduced. The measurement result of TEM of the nanoparticle systems obtained the experiment is reported that the size of these colloids were between 5 to 35nm. We also report the UV-visible optical absorption spectra of these colloids. To the metal plate prepared simultaneously, the measurement result of SEM and AFM of this plate is also reported and the roughness of the silver plate surface is about 60nm.Both the colloids and the nano-scale metal surface can become the very perfect SERS substrates.Rhodamine B, a kind of strong fluorescence laser dye, with gold colloidal surface, has been studied by surface-enhanced Raman spectroscopy (SERS) with near-infrared (NIR) excitation in the presence of the halide ions (CF,Br-,F). The results reveal that the interaction strength of halide ions with gold surface increases in the order of CF Br-< F. Under the condition of that these three kind halide ions coexist, F ion will be adsorbed with the gold surface in priority. This conclusion is also been proved indirectly by the UV-visible spectroscopy of the systems above.When exciting at 1064nm, the fluorescence of the crystal violet (CV) in the CV-Au sol system will be quenched rapidly and meanwhile its Raman signals willalso be enhanced at least 105. After addition of some drops HNO3(1+10-2M), due to the chemical interaction between some CV molecules and HNO3, some HCV derivatives will be formed. Compared with CV, HCV can be adsorbed on metal surface more easily and tightly so there is some extra enhancement in this condition. This phenomena also shows that the SERS enhancement factor of some molecules can be modified by changing the PH of the molecules-sols system.