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Strengthen Basal Silver Nanoparticles Preparation And Molecular Raman Spectra Analysis

Posted on:2012-12-11Degree:DoctorType:Dissertation
Country:ChinaCandidate:K DongFull Text:PDF
GTID:1221330368981533Subject:Materials science
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Raman spectroscopy is an important subject in modern analysis and detection science. The solid or liquid samples can be directly tested application of Raman spectroscopy technology without any pretreatment operation, and the samples won’t be damaged with the test process. Raman spectrometer which is designed with optical fiber laser head can be applied to all kinds samples with any sizes and shapes. The analysis and test work became great convenience.But because of the Raman scattering signal is very weak, and it’s often interfered by fluorescence, It’s hard to get the samples’ Raman spectra in actual testing process; On the other hand is very difficult to detect the samples Raman signals when the concentration samples is too low, which may result in the wrong judgment. Surface-Enhanced Raman Spectroscopy (SERS) technique can restrain fluorescence, increase the intensity of Raman scattering light greatly. So Surface-Enhanced Raman Spectroscopy can be widely used in the actual testing work.The substrate which used for Surface-Enhanced Raman Spectroscopy include rough metal electrodes, metal colloid, metal island film, metal nanoparticles. With the development of SERS substrate research, we want to get more better material surface properties in order to improve SERS enhancement factor furtherly. The precious metallic material which prepared by nanometer array technology is the most popular SERS enhancement base at present. But this method is very difficult to control in the preparation process and the enhance factor is limited. So it’s very important to do further research on metallic nano material on the basis of previous research results, so the enhance factor of the SERS substrate can be improved further moreIn the second chapter, we prepared nano silver SERS substrate with the nano pits array which were formed by aluminium surface oxidation. Through the experiments we found that:The anodic alumina template nanotubes structure can be removed bu the mixed solution of chromium acid and phosphoric acid, the nano pits array will be remained on the surface of the aluminium. These nano pits array were beneficial to the growth of the silver nanoparticles. The silver nano particles will be formed in the nano pits array using alternating current(AC) electrodeposition method. Different shapes of silver nanoparticles can be prepared under different electrodeposition time, when the electrodeposition time was short, the shape of the silver nanoparticles were spherical, The enhancement effect of this kind of silver nano array structure was limited, its enhancement factor was similar with the nanowires which were grew in the aluminum oxide nanotubes, when the concentration of the probe molecules was below 10"3 mg/L we would not get SERS enhancement spectrum; When the electrodeposition time was appropriate the shapes of silver nanoparticles like trees, and this structure of the silver nanoparticles has strong Raman enhancement effects, even when the concentration of the probe molecules was low to 10-12 mg/L, we still can get the Raman spectra of the probe molecules, the enhancement substrate has reached the single molecule detection level; When electrodeposition time was too long, the film with complex structure will be formed, Due to this kind of substrate has strong Raman signals itself, therefore it is not applicable for SERS enhancement substrate.The problem of some molecules which were difficult to detect can be effective solved by using the trees like nano silver enhance substrate. After we got the Raman spectra of molecules, the next work is vibration analysis in order to get useful information from the spectroscopy. Because Raman spectroscopy technology was really applied in practical detection work only has nearly thirty years history, and the development of high performance electronic computers was only 20 years time. So ithere were no systemic analysis of Raman spectra. Quantum chemical theory is most effective way for explaining Raman spectra, By building the molecular model and simulation computation Quantum chemical theory can get all the atoms vibration information of the molecular, and give reasonable explanation with the Raman spectra. The third chapter of this paper briefly introduced the basic principle of quantum chemistry theory, and the basic concepts of function and the atom valence bond orbital, By comparing the computing calculation spectrum and experimental spectrum of acetonitrile molecular, and calculated parameters was finally choiced.In the fourth chapter, various organic molecules included halogenated monosilane, alcohols, aldehydes, organic acids, benzene and its derivatives, xylene isomers, aminobenzoic acid, phthalate, heterocyclic compounds,some food additives like ethyl maltol, "one drops delicious" and other material, about 38 kinds of molecules had been detected, These molecules have been all simulate calculated by quantum chemical theory, and the calculation spectrum was coincided with their experimental spectrum. Raman spectra has many advantages at isomers research, and we found that the ring tension has great influence in Raman spectroscopy with ring compounds molecular.In the chapter 5 of this paper, Some inorganic molecules included sulphuric acid, hydrochloric acid, nitric acid, phosphoric acid, boric acid, high chlorine acid several acids molecules were tested and vibration analysed; Some kinds of alkali molecules include lithium hydroxide monohydrate, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, copper hydroxide, aluminum hydroxide, ferric hydroxide were tested and vibration analysed; Four categories salts molecules include nitrate, carbonate, sulfate and phosphate were tested and vibration analysed, nitrate including:sodium nitrate, potassium nitrate, magnesium nitrate, calcium nitrate, copper nitrate, zinc nitrate, lead nitrate, barium nitrate, strontium nitrate, nickel nitrate, cobalt nitrate, aluminum nitrate, iron nitrate, bismuth nitrate, chromium nitrate, lanthanum nitrate, zirconium nitrate. Carbonate included:lithium carbonate, sodium carbonate, potassium carbonate, magnesium carbonate, calcium carbonate, zinc carbonate, strontium carbonate, barium carbonate. Sulfate included: sodium sulfate, potassium sulfate, magnesium sulfate, calcium sulfate, zinc sulfate, copper sulfate, ferric sulfate, alumina sulfate. Phosphate included:potassium phosphate, sodium phosphate, aluminum phosphate, calcium phosphate, iron phosphate, zinc phosphate. A total kinds of these molecules was sixty-three. On the basis of lots of experiment testing, also we analysed certain laws by comparing the Raman spectra of the similar material molecules.
Keywords/Search Tags:Raman spectroscopy, Surface-enhanced, Nano silver substrate, Density functional theory, Organic molecules, Inorganic molecules
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