I. Tuzovskaya

FORMATION OF GOLD NANOPARTICLES IN ZEOLITES

The formation of gold nanoparticles in mordenites has been studied by the methods of FTIR spectroscopy of adsorbed CO and diffuse reflectance UV-visible spectroscopy. Different states of ionic and metallic gold were detected in the zeolite cavities and on the external surface of the zeolite – Au+ and Au3+ ions, charged clusters Aunδ+, and neutral nanoparticles Aum. The relative amount of these states depends on the method of sample preparation, type of redox treatment and the SiO2/Al2O3 molar ratio.

Catalytic activity in the hydrocarbon conversion of systems containing platinum, nickel, iron, and zinc nanoparticles (communication 2)

The catalytic activity of metal-containing zeolites modified by nanosized Pt, Ni, Fe, and Zn powders was studied in the process of upgrading the petroleum straight-run gasoline fractions. It was found that the introduction of metal nanoparticles into the zeolite increases the catalyst activity and allows the desired product to be obtained at a lower processing temperature. An enhancement of the aromatization reactions of the hydrocarbon feedstock was revealed on the catalyst samples deactivated in the first reaction cycle and calcined in air.

Catalytic activity in hydrocarbon conversion of pentasil containing platinum, nickel, iron, or zinc nanoparticles

Catalyst samples containing nanosized Pt, Ni, Fe, or Zn powder were prepared on the basis of high-silica zeolite ZSM-5 by mechanical mixing. The structure and state of active centers of zeolite catalysts (freshly prepared or calcined after the reaction cycle of upgrading the petroleum straight-run gasoline fraction) were studied by means of the X-ray diffraction, UV spectroscopy, and X-ray photoelectron spectroscopy techniques. It was shown that the oxidized forms of the metals are practically absent from the freshly prepared zeolite samples. After the heat treatment of the catalysts in air, nanosized metal powders transform into oxides on the zeolite surface, with iron and nickel producing the greatest variety of oxidized forms.

The Influence of the Peptide Molar Ratios on the Functionalization of Gold Nanoparticles

Au nanoparticles (NPs) functionalized with L-cysteine (Cys) and cysteine-glycine (Cys-Gly) were synthetized. The AuNPs were prepared using sodium citrate as reducing agent. The influence of the molar concentrations of Cys and Cys-Gly, as well as the sodium citrate is studied on particle size and particle size distribution. TEM measurements revealed the formation of AuNPs with diameter in the range 5-35 nm which corresponds to nontoxic sizes [we should add a reference here, perhaps number one]. The optimal particle size for biomedical application along with narrow particle size distribution was observed for samples prepared with molar ratio of CAu:Ccitrate = 1:10. The results of UV-Vis spectroscopy revealed the interaction of the AuNPs with Cys and Gly-Cys demonstrated by a visible change in the absorption intensities of the plasmon peak located at 520 nm after AuNP functionalization and a slight shifting of this gold nanoparticles plasmon peak. Thus, any dielectric shell on surface of particles with more refraction index (and, correspondingly, dielectric function) can produce the particles with the red shift. Such effect of the surface shell with red-shift in the range of few nanometers observed for the AuNPs functionalized with Cys and Cys-Gly (Fig. 4) can be interpreted as thin or discontinuous layer of aminoacid molecules according to the data of optical spectra simulation.

Study of electronic state of supported gold nanospecies by IR spectroscopy

The nature of different Au species supported on hexagonal mesoporous silica has been studied by infrared spectroscopy of adsorbed CO. Experiments revealed existence of the following states of supported gold: neutral metal particles Au°, ions Au⁺ and a number of partly charged states Au^δ+ with different effective charge. Redox pretreatments (vacuum, O₂ and H₂) of Au/SiO₂ at the different temperatures (100, 300 and 500°C) exert a significant effect on the electronic state of supported Au species. The experiments showed high stability of Au^δ+ states under all treatments; that may prove their active role in catalytic properties of gold.