Preparation Of Chiral Gold Nanomaterials And Their Catalytic Properties

Chirality is one of the common and exotic phenomenon in nature. Chiral nanomaterials, especially chiral metal nanomaterials, have been paid more attention due to the normal and strange phenomenon. The chiral metal nanomaterials show unique size and optic effects, which is different from molecular chirality in nature, and will provide new chance for assymmetric sythesis and biological application. At present time, the chirality of chiral metal nanomaterials comes from chiral nucleus, chiral surface or chiral arrangement of nanoparticals. It has aroused a large amount of interests to prepare chiral nanoparticles by introducing chiral asymmetric factors into the particles, such as amino acids, peptides, and DNA. On the other hand, chiral amphiphilic molecules are a kind of functional molecules due to their unique structure, and can form various chiral assembies, such as chiral micelles, chiral vesicles. In the present work, the nucleoside type chiral amphiphilic molecules were sythesized, and then were used to combine the gold nanoparticles to prepare chiral gold nanoparticles, and the interaction between them, as well as the application in catalysis, were systematically investigated.1. Synthesis and charaterization of chiral biocompatible surfactant4-amino-l-octyl-1H-pyrimi-din-2-one (C8cyt) was synthetized by one step method. The purity of the product was measured by differential scanning calorimeter and elemental analyzer. The structure of the product was characterized by IR and 1H NMR, and the associating behavior of C8cyt in aqueous solutions was investigated by surface tension method. The chirality of the product was characterized by CD. The experimental results showed that the synthesized product was the target product 4-amino-1-octyl-lH-pyrimidin-2-one (C8cyt) with high purity. The two inflection points can be found in the curve of the surface tension, corresponding to the critical aggregation concentration (cac) and the critical micelle concentration (cmc), respectively, are 2.6 mM and 7.0 mM. Futhermore, the product shows strong chirality.2. Fabrication and charaterization of chiral gold nanomaterialsThe chiral gold nanoparticles were successfully prepared by introducing the amphiphilic C8cyt into the gold sols. The UV-vis spectroscopy, dynamic light scattering (DLS), transmission election microscopy (TEM), circular dichroism spectroscopy (CD), and fourier transformed infrared spectroscopy (FT-IR) were used to investigate the interaction between gold nanoparticles and C8cyt. It was found that the C8cyt molecules can be effectively by bound to the surface of gold nanoparticles, which transform the chirality to the surface of gold nanoparticles with the new positive CD signals. With addition of C8cyt, the Au-C8cyt complex particles grow slightly, and form Au-C8cyt clusters. TEM images indicated that when the small amount of C8cyt was added into the gold sols, halo layer of chiral gold nanoparticles were formed, and more C8cyt addition resulted in the formation of gold custers due to the bridge link between alkyl chairs of C8cyt. Based on the IR analysis, Cscyt molecules can not only bind to the gold particles via the NH2 moieties, but also result in the assembly of gold particles via the bridge link between the hydrophobic alky chains of C8cyt molecules. The above results will provide a new path to fabricate the chiral gold nanoparticles and their functional application.3. The study of atalytic property of chiral gold nanomaterialsUV spectroscopy was used to monitor the dynamic behavior when gold nanomaterials were presented in the system. The result shows that different nanomaterials (gold nanoparticles, gold nanomaterials with structure ?, ? and ?) show different catalytic properties. With the increase of the amount of gold nanomaterials and the temperature of the reaction, the rate of the reaction accelerates. The catalytic activity of chiral gold nanomaterial was significantly superior to that in the present of the gold nanoparticles when they were 2 weeks. The study of catalytic property of chiral gold nanomaterials for nitrophenol reduction provides a theoretical foundation and pioneering experimental results for the application of chiral gold nanomaterials in asymmetric synthesis.