DNA-templated Synthesis, Assembly, And Optical Application Of Noble-Metal Nanoparticles

With the rapid development of nanotechnology, the special structures and properties of nanomaterials have attracted much attention of scientists. The synthesis of new nanomaterials is speedy rising. Preparation methods, possessing the characteristics of non-polluting, low-cost, and green synthesis have potentially wide range of applications. Along with the social progress, there are huge requirements on how to design new green synthesis method and to detect of environmental pollutants. Researchers dedicate more and more attention on this point. In particular, bimolecule templates are resource-rich, low cost, environmental health, and have unique structures and various kinds of morphology.Thesis focused on the DNA as a template to synthesize noble metal nanopartilces, and the characteristics and applications of the as-synthesized nanomaterials were discussed as in the following four sections.The first section was on DNA as a template to synthesize the DNA-Ag nanocomposites, and to use this material for the detection of Hg2+by circular dichroism spectroscopy.In test, DNA-Ag nanocomposites were firstly prepared by the sunlight photoreduction. Then, we use circular dichroism to successfully detect Hg2+in the leve of0.1pM (or20pg per milliliter). The detection limit was at least two orders of magnitude lower than that of previously reported results by the use of organic-inorganic hybrid probe. Moreover, only1μL of contaminated water was needed in the test. In test, we chose the to aminothiophenol probe molecule to Hg2+initiative crawl on the detection of specific amplification. This reflected in the Hg2+have a good response, the point is precisely the ability to detect pM Hg2+consistent. Drinking water testing, the use of this method, the amount of sample needed is very small, thus reducing the interference of external factors. This method for Hg2+detection is simple, fast, and reliable. The second section is on the DNA as template to synthesize the gold and silver composite nanomaterials and to study their spectroscopic properties.We used a simple method to synthesize the gold and silver composite in the sunlight irradiation. The morphology of such nanomaterials can be adjusted by changing the ratio of gold ions and silver ions. During synthesis, the DNA was used not only template, but also to reflect the favorable reductant. The UV spectra and the optical waveguide techniques were used to monitor the synthesis of gold and silver in the sunlight irradiation nanocomposites reaction. DNA in the light of the first restore solution of silver ions into silver nanoparticles, with the extension of exposure time, the number of nanoparticles increased diameter growth, UV spectra and optical waveguide peak intensity gradually increased. By adding the solution of gold chloride acid, the replacement reaction between gold and silver occurred and combined effects of light reduction of gold ions, the formation of particle surface gold elements led elements of the internal silver-oriented composite structure of nanomaterials. Moreover, this new structure of nanomaterials is still a good Raman substrate.The third section is on the preparation of Raman "hot spots" using the DNA as a template for self-assembly of Au nanoparticles.The DNA molecule is negatively charged, and mixed with the synthesized positively charged gold nanoparticles to self-assemble into composite nanomaterials with "hot spots". This nanomaterial was used as a SERS substrate for the detection of small molecules of Rhodamine (R6G), pyridine (Py), and aminothiophenol (PATP). The results showed that:the preparation of SERS substrate in this method was not only high yield, uniformity, and better SERS enhancement effect. Therefore, the SERS substrate can detect low concentrations of the different stypes of small molecule compounds.The fourth section is on the in-situ optical synthesis of Au nanoparticles on the DNA template and on their assembly spectroscopic studies.We used DNA as a template to prepare single-layer gold net. By adjusting the ratio of DNA base pair and the number of AuCL4-, and its growth pattern can be controlled. We use the UV-Vis spectrometer for spectral analysis. We found that the UV spectral absorption peak had a red shift as the R value increased. These results showed that the nanoparticles grew gradually.