The Synthesis And Application Of The Rough Au Nanoparticles And The Quantitative Test Of The Core-shell Nanoparticles

The last century seventy’s, Fleischmann found that copper, silver, gold nanostructure metal has 104-107 effect of surface enhanced Raman scattering (SERS).The enhancement effect is not only limited to nanostructured, free-electron-like metals, but also the size, the shape or the distance of metals.People know whether the SERS technique is extended to the transition metal and its sensitivity and reproducibility of SERS substrate can become the key to universal detection technology of SERS spectrum. Go up century ninety time, tian groups who worked for the transition metal SERS technology to expand into the platinum, palladium, ruthenium, rhodium, iron with catalytic activity on the extensive, in-depth, systematic work, had attract people’s attention performance.The paper is main about the sensitivity and reproducibility of SERS substrate.For the issue of SERS sensitivity, we synthetize the rough Au nanoparticle to achieve high sensitivity as its "hot spot".For the issue of SERS reproducibility, the most notable is whether it can do SERS quantitative experiment.Compared with the normal Raman spectrum, SERS intensity is influenced by the electromagnetic enhancement, adsorption orientation of molecule, uniformity and of substrate. There is not a simple linear relationship with molecular concentration. It is difficult for SERS substrate used in the quantitative analysis. Internal standard method may be the most appropriate, can eliminate the influence brought the difference of the substrate. But the competitive adsorption of internal standard of molecular and analyte, it will challenge the stability and reliability of the detection process of the internal standard. So we synthesized Au-M-Ag core-shell structure nanoparticles.It can be effective to avoid the problem of molecular adsorption.The main research contents of this paper can be summarized as follows:l.We synthesized the rough gold nanoparticles, through the regulation of the surface roughness(SPR peak position), to achieve the double resonance enhancement effect among the laser, the maximum absorption wavelength of molecule and nanoparticles of SPR peak position. This paper used the 633nm laser and the molecule of malachite green isothiocyanate(MGITC).It is maximum absorption wavelength is about 620nm.We synthetized a series of different roughness of nanoparticles to realize the matching the laser and the molecule to achieve the ultra-high SERRS effect. The results showed that, testing condition is:MGITC concentration is 10-7 sol spectrum.While the rough nanoparticles SPR peak is larger than 605nm, the resonance enhancement effect was not obvious.And it can get the strong SERS effect in the range of conditions.2.We synthesized rough nanoparticles(SPR peak around 620nm) for single particle SERS experiment. We chose MGITC as the probe molecule to explore the single particle’s "hot spot" and the resonance enhancement of the SERS effect.The results showed that we can measure the better Raman signals. We also studied whether it can detect signal by the nanoparticles themselves "hot spots".So we chose 4-thiol 4-(4-biphenyl) pyridine as a probe molecule, results showed, we can also get the signal, although the signal is much weaker compared with the resonance molecule.However, it can prove that the rough nanoparticles still has great advantages in SERS detection.3.We used the rough gold nanoparticles to the actual test.In fact, we detected the molecular which had weak adsorption.And it was very difficult to achieve low concentration detection, relying on monodisperse rough gold nanoparticles.So we need to optimize the conditions in the detection process. Our target molecule was clenbuterol molecules. We achieved the low concentration detection of the clenbuterol through optimizing agglomeration agent, concentration and the ratio of material. Finally, the result showed that the agglomerating agent selected 0.1M NaCl molecules, molecules and particles in the proportion of 3:1, SERS effect was strongest. And the lowest concentration we detected was 30ng/ml through using the optimization of conditions.4.We synthesized Au-M-Ag nanoparticles with core-shell structure for SERS quantitative analysis. It showed that the internal standard molecular 4-mercaptopyridine was indeed wrapped in gold and silver meta through TEM, STEM characterizationl.We chose 1,4-Phenylene diisocyanide as the probe molecule, and the final concentration of analyte molecule was from 10-9mol/L to 10-8mol/L.The results showed that, if we didn’t use the internal standard molecules to correct, the linearity of SERS signal change with the concentration was not controllable, if we use the calibration of internal standard, SERS signal and its concentration is linear.So the core-shell nanoparticles Au-M-Ag can achieve quantitative detection of SERS as using the internal standard calibration.