Surface Preparation And Research Of Infrared Spectrum Materials

Molecules adsorbed on metal island films exhibit10～1000times more intense infrared absorption than would be expected from conventional measurements without metals. This effect is called surface-enhanced infrared absorption(SEIRA).The SEIRA-activity greatly depends on the morphology of the metal nanoparticles, therefore, the preparation of the SEIRA substrate is important to enhanced performance.Ag is one of the most important metals used in SEIRA and SERS analysis. Now people focus on how to develop an economic and facile approach to fabricate surface-enhanced substrate. In this paper, Ag was prepared as a template for SEIRA. The substrates were characterized and analysed enhancement mechanism by Fourier infrared spectrometer, Raman spectrometer, Scanning electron microscope and Ultraviolet-visible spectrometer. And the substrates were also applicated in practical detection.Some important results were deseribed as follows:1. The silver nanoparticles on glass, CaF2salt slice and indium tin oxid (ITO) conductive glass were respectively prepared by the silver mirror method, sol-gel method and plating method. O-nitranline and benzoyl peroxide were used as probe molecules. The results exhibited the most obvious enhancement effect on Ag/galss substrates.The optimized conditions for preparing silver nanoparticles were as follows:1%mass concentration of AgNO3at temperature of60℃, and more evenly dispersed silver nanoparticles would be obtained by the addition of some surfactants The enhancement factor was61. These SEIRA-active templates were also promised for SERS application, as demonstrated with high enhanced effect.2. The morphology of the Ag/glass substrate, Ag/CaF2substrate and Ag/ITO substrate were characterized by scanning electron microscopy. O-nitranline and benzoyl peroxide were used as probe molecules.Comparison of the normal infrared spectra and SEIRA spectrum for both probe molecules, the infrared spectra peak did not shift.We conjectured that its main reasons were the electromagnetic field effect and the physical adsorption. Different substrate morphology had a great impact on enhanced effect. The ball-shaped nanoparticles exhibited the greatest enhancement effect.The substrate was prepared by sol-gel method exhibit different enhanced mechanism by the different experimental approaches. Ag/glass as a template was analysed for SERS. The Raman peak had shifted, which indicated that the mechanisms for SERS and SEIRA were different.3. The method for detecting food additive by SEIRA technology was explored. BPO was quantitative analysed with SEIRA material by silver mirror method. The results showed that the calibration curve for pure BPO was y=1.0961x+0.0127in range of5×10-4mol/l～2.5×10-2mol/l, correlation coefficient was0.9945, measurement of concentration was between2.35×10-6g/l and1.18×10-4g/l, average recovery rate was101.7%,RSD was1.33%.In the practical application of flour, the calibration curve was y=4.0555x-0.0721in range of6.6×10-4mol/l～1.033×10-2mol/l, correlation coefficient was0.9927, measurement of concentration was between3.1×10-6g/1and4.85×10-5g/l. The results were less than quantitative range of the infrared spectra in general.Improve the sensitivity of the infrared spectrum.