Gas Phase Catalysis by Metal Nanoparticles in Nanoporous Alumina Membranes

Nanoporous alumina membranes, loaded with palladium and ruthenium nanoparticles of various size, were used for gas phase hydrogenation of 1, 3‐butadiene and for oxidation of carbon monoxide, respectively. Those membranes contain 10⁹ ‐ 10¹¹ pores per cm², all running perpendicular to the surface. Membrane discs of 20 mm in diameter and only 60 μm thick, incorporated in a reactor in which the reactants can be pumped in a closed circuit through the pores, turned out to very actively catalyze hydrogenation of butadiene (Pd) and oxidation of CO (Ru). The activity of the Pd catalysts depends characteristically on the particles size, the gas flow, and of the educts ratio. As could be expected, larger particles are less active than smaller ones, whereas increasing gas flows in case of hydrogenation accelerates the reactions. Excessive hydrogen reduces selectivity with respect to the various butenes, but favours formation of butane.     

Effect of WO3 particle size on the type and concentration of surface oxygen

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Investigation on relation between TL and OSL of Li2B4O7:Cu, In

Polycrystal Li₂B₄O₇ (LBO) doped with Cu and In was prepared and then sintered at different temperatures. X-ray diffraction (XRD) was applied to get the parameters of the LBO structure, thermoluminescence (TL) and optically stimulated luminescence (OSL) were measured, and a second-order exponential decay model was fitted to the OSL decay curves. The results indicate that the original number of OSL traps that have captured electroncs is linearly related with the sum of TL decay during the OSL process. Mean decay constant of OSL is related to the sintered temperature. The possible reason is that the sintered temperature affects the crystal sizes of the polycrystal, and consequently affects the stimulating lights’s intensity and the photoionization cross-section of the electrons, which have been captured by the traps. __________ Translated from Acta Scientiarum Naturalium Universitatis Sunyatseni, 2005, 44(4) (in Chinese)     

Plasmid DNA isolation using amino-silica coated magnetic nanoparticles (ASMNPs)

A simple and efficient approach for the rapid isolation of plasmid DNA from crude cell lysates has been described. The approach took advantage of the amino-modified silica coated magnetic nanoparticles (ASMNPs) with positive zeta potential at neutral pH and superparamagnetism under the external magnetic fields. As a demonstration, the pEGFP-N3 plasmid has been concentrated and isolated from the E. coli DH5α transformed with pEGFP-N3 plasmid through electrostatic binding between the positive charge of the amino group of ASMNPs and the negative charge of the phosphate groups of the plasmid DNA. Then the pEGFP-N3 plasmid has been released easily and quickly from the pEGFP-N3 plasmid-ASMNPs complexes with 3 M NaCl. The entire procedure could be carried out by the aid of external magnetic fields in 15 min and eliminate the need of phenol, cesium chloride gradients or other noxious reagents and complexes operation. Moreover, the pEGFP-N3 plasmid obtained by this approach retains biological activity that can be suitable for restriction enzyme digestion and cells transfection with expression of green fluorescence protein.     

Effect of the coordination sphere of d<Superscript>0</Superscript> metallocene on triplet-triplet energy transfer

The triplet nature of rare long-lived states of d⁰ metallocenes formed upon ligand-to-metal energy transfer was confirmed by studies of triplet-triplet charge transfer in biscyclopentadienyl complexes Cp₂MCl₂ (M = Zr (1), Hf (2)). The interaction between precatalysts and substrates of catalytic polymerization systems, viz., complexes 1 and 2 and unsaturated hydrocarbons (alkenes and dienes), was studied in the region of concentrations close to catalytic values. For organometallic π-complexes, it has been shown for the first time that, in the case of the unsaturated hydrocarbons, the efficiency of energy transfer obeys the Perrin equation. The process occurs at distances R ₀ close to the diameter of the interacting molecules and is well described by the exchange-resonant mechanism of interaction. In the case of the cyclopentadiene-Cp₂MCl₂ (M = Zr, Hf) systems, R ₀ = 14.6 Å. A linear relationship between the critical radius of the quenching sphere R ₀ and the number of carbon atoms in a linear α-olefin has been revealed for the first time and evidences the formation of a π-complex between the precatalyst and substrate molecules. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 35–39, January, 2007.     

A method to construct polyelectrolyte multilayers film containing gold nanoparticles

Gold nanoparticles in polyelectrolyte multilayers film can be easily prepared by repeating immersion of a substrate in poly(diallyl dimethylammonium) chloride (PDDA)-AuCl₄⁻ complexes solution followed by reduction Au³⁺ through heating. UV-vis spectroscopy, cyclic voltammetry (CV) and tapping-mode atomic force microscopy (AFM) are used to confirm the successful construction of the polyelectrolyte multilayers film and the formation of gold nanoparticles. The multilayers film shows electrocatalytic activity to dioxygen reduction.     

New silver(i) thiazole-based coordination polymers: structural and photophysical investigation

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Singlet Energy Transfer as the Main Pathway in the Sensitization of Near‐Infrared Nd3+ Luminescence by Dansyl and Lissamine Dyes

In general, sensitization of lanthanide(III ) ions by organic sensitizers is regarded to take place via the triplet state of the sensitizers. Herein, we show that in dansyl‐ and lissamine‐functionalized Nd³⁺ complexes energy transfer occurs from the singlet state of the sensitizers to the Nd³⁺ center. No sensitized emission was observed in the corresponding complexes with Er³⁺, Yb³⁺, and Gd³⁺ ions. Furthermore, the fluorescence of the sensitizers was quenched only in the Nd³⁺ complex and not in the complexes with the other ions. Only Nd³⁺ centers can accept energy from the singlet state of the dyes, because the excited states of Nd³⁺ have a high spectral overlap with the fluorescence of the dansyl and lissamine sensitizers, and because the selection rules allow a fast energy transfer, which apparently is competitive with the fluorescence.     

纳米核壳式铜-锡双金属粉的制备及性能研究

A kind of novel core-shell Cu-Sn bimetallic nanoparticles has been prepared by a new method (displacement method), in which Sn was made to cover on the surface of Cu nano-core. The preparation method and reaction mechanism have been discussed. This reaction happened under the existence of coordinate agent-(NH₂)₂CS and protective agent PVP. The nanoparticles prepared were with a core-shell structure, granule diameter between 50～100 nm and good dispersing capability. The Cu-Sn nanoparticles proposed has better oxidation-resistant ability than Cu nanoparticles with corresponding granule diameter and can be applied as lubricant additives as well as antibacterial agent. When the additive amount is very low (0.1wt‰～0.5wt‰), it can improve the P_B of the lubricant by 92%～106%, and also enhance its antiwear characteristics and friction-reducing properties. At the concentration of 1 000 ppm, it can reach an antibacterial ratio of 99.99%.     

Photoinduced Electron Transfer between CdS and CdTe Nanoparticles in Colloidal Solutions

The photochemical behavior of solutions containing a mixture of CdS and CdTe nanoparticles under pulsed irradiation conditions was investigated. It was shown that electron transfer from the CdS particles to the CdTe nanoparticles occurs during the photoexcitation of such systems. The effectiveness of the process is increased with increase in the size of the CdTe nanoparticles. Such behavior is due to decrease in the potential of the CdTe conduction band with increase in the size of the nanoparticles as a result of the appearance of quantum-dimensional effects.