(R,R)-DPEN-modified Ru/gamma-Al2O3 - An efficient heterogeneous catalyst for enantioselective hydrogenation of acetophenone

An efficient enantioselective catalyst of 5 wt.% Ru/-gamma-Al2O3 modified with R,R-1,2-diphenylethylene-diamine ((R,R)-DPEN) for the hydrogenation of a non-activated aromatic ketone of acetophenone has been investigated, a relatively high enantiomeric excess (ee) of 60.5% was obtained at both the conversion and selectivity larger than 99%, it was about three times higher than the ee values reported up to now for acetophenone hydrogenation with the supported transition metal catalysts modified by chiral reagents. The influences of some reaction parameters such as phosphine ligand, substrate/catalyst/modifier molar ratios, base, solvent, pressure and reaction temperature have been discussed. The chiral modifier of (R,R)-DPEN was very important in controlling the enantioselectivity through adsorption competing with other substrates on the surface of active metal species. The phosphine ligand and base were also important and indispensable in the present reaction.

Electrogenerated chemi luminescence from Ru(BPY)(3)(2+) ion-exchanged in carbon nanotube/perfluorosulfonated ionomer composite films

The electrochemistry and electrogenerated chemiluminescence (ECL) of ruthenium(II) tris(bipyridine) (Ru(bpy)(3)(2+)) ion-exchanged in carbon nanotube (CNT)/Nafion composite films were investigated with tripropylamine (TPA) as a coreactant at a glassy carbon (GC) electrode. The major goal of this work was to investigate and develop new materials and immobilization approaches for the fabrication of ECL-based sensors with improved sensitivity, reactivity, and long-term stability. Ru(bpy)(3)(2+) could be strongly incorporated into Nafion film, but the rate of charge transfer was relative slow and its stability was also problematic. The interfusion of CNT in Nafion resulted in a high peak current of Ru(bpy)(3)(2+) and high ECL intensity. The results indicated that the composite film had more open structures and a larger surface area allowing faster diffusion of Ru(bpy)(3)(2+) and that the CNT could adsorb Ru(bpy)(3)(2+) and also acted as conducting pathways to connect Ru(bpy)(3)(2+) sites to the electrode. In the present work, the sensitivity of the ECL system at the CNT/Nafion film-modified electrodes was more than 2 orders of magnitude higher than that observed at a silica/Nafion composite film-modified electrode and 3 orders of magnitude higher than that at pure Nafion films.

Electrochemical and electrogenerated chemiluminescence of clay nanoparticles/Ru(bpy)(3)(2+) multilayer films on ITO electrodes

The electrochemical and electrogenerated chemiluminescence of Ru(bpy)(3)(2+) immobilized in {clay/Ru(bpy)(3)(2+)}(n) multilayer films by layer-by-layer assembly were investigated. The stable multilayer films of clay and Ru(bpy)(3)(2+) were assembled by alternate adsorption of negatively charged clay platelets and positively charged Ru(bpy)(3)(2+) from their aqueous dispersions. UV-vis spectroscopy, quartz crystal microbalance (QCM), cyclic voltammetry, and electrogenerated chemiluminescence (ECL) were used to monitor the immobilization of Ru( bpy)(3)(2+) and the regular growth of the {clay/Ru( bpy)(3)(2+)}(n) multilayer films. The multilayer films modified electrode was used for the ECL detection of tripropylamine ( TPA) and oxalate. The proposed novel immobilized method exhibited good stability, reproducibility and high sensitivity for the determination of TPA and oxalate, which mainly resulted from the contributing of clay nanoparticles with appreciable surface area, special structural features and unusual intercalation properties.

固相反应法制备Pt-Ru/C催化剂对乙醇氧化的电催化活性研究

引言近年来,直接甲醇燃料电池(DMFC)由于其燃料来源丰富、价格低廉、甲醇携带和储存安全方便等独特的优越性而越来越受到重视[1]。但是甲醇具有一定的毒性,因此要想实现DMFC在诸如手机、笔记本电脑以及电动车等可移动电源领域的应用,必须探索新的液体燃料以替代有毒性的甲醇。其中乙醇很易从农作物中大量生产,又无毒,因此很有可能用作替代甲醇的质子交换膜燃料电池燃料。近年来乙醇的电催化氧化已被众多的研究者从电催化和乙醇燃料电池的角度进行了广泛的研究[2,3]。但是乙醇在Pt电极上的氧化易导致强吸附物种CO毒化催化剂,Pt鄄Ru合金是目前强吸附毒化物种CO易氧化为CO2的最有效的电催化剂,因此近年来也有一些关于Pt鄄Ru合金催化剂对乙醇的电化学氧化的研究[4~6]。我们研究组首次用固相反应法制备了Pt/C催化剂,发现所制得的Pt/C催化剂对甲醇[7]和乙醇[8]氧化的电催化性能要比用传统的液相反应法制得的Pt/C催化剂好很多。但Pt/C催化剂对甲醇和乙醇氧化的电催化活性还是较低,因此,本文首次研究了用固相反应法制备Pt鄄Ru/C催化剂及这种催化剂对乙醇氧化的电催化性能,发现用固相反应法制备的Pt鄄Ru/C催化剂对乙醇氧...

Pt nanoparticles: Heat treatment-based preparation and Ru(bpy)(3)(2+)-mediated formation of aggregates that can form stable films on bare solid electrode surfaces for solid-state electrochemiluminescence detection

A simple thermal process for the preparation of small Pt nanoparticles is presented, carried out by heating a H-2-PtCl6/3- thiophenemalonic acid aqueous solution. The following treatment of such colloidal Pt solution with Ru( bpy)(3)(2+) causes the assembly of Pt nanoparticles into aggregates. Most importantly, directly placing such aggregates on bare solid electrode surfaces can produce very stable films exhibiting excellent electrochemiluminescence behaviors.

Electrogenerated chemiluminescence sensors using Ru(bpy)(3)(2+) doped in silica nanoparticles

A novel electrogenerated chemiluminescence (ECL) sensor based on Ru(bpy)(3)(2+)-doped silica (RuDS) nanoparticles conjugated with a biopolymer chitosan membrane was developed. These uniform RuDS nanoparticles ( similar to 40 nm) were prepared by a water-in-oil microemulsion method and were characterized by electrochemical and transmission electron microscopy technology. The Ru( bpy)(3)(2+)-doped interior maintained its high ECL efficiency, while the exterior nanosilica prevented the luminophor from leaching out into the aqueous solution due to the electrostatic interaction. This is the first attempt to branch out the application of RuDS nanoparticles into the field of ECL, and since a large amout of Ru(bpy)(3)(2+) was immobilized three-dimensionally on the electrode, the Ru( bpy)(3)(2+) ECL signal could be enhanced greatly, which finally resulted in the increased sensitivity. This sensor shows a detection limit of 2.8 nM for tripropylamine, which is 3 orders of magnitude lower than that observed at a Nafion-based ECL sensor. Furthermore, the present ECL sensor displays outstanding long-term stability.

Synthesis of PtNPs/AQ/Ru(bpy)(3)(2+) colloid and its application as a sensitive solid-state electrochemiluminescence sensor material

The facile synthesis of the novel platinum nanoparticles/Eastman AQ55D/ruthenium(II) tris( bipyridine) (PtNPs/ AQ/Ru(bpy)(3)(2+)) colloidal material for ultrasensitive ECL solid-state sensors was reported for the first time. The cation ion-exchanger AQ was used not only to immobilize ECL active species Ru(bpy)(3)(2+) but also as the dispersant of PtNPs. Colloidal characterization was accomplished by transmission electron microscopy (TEM), X-ray photoelectron spectrum (XPS), and UV-vis spectroscopy. Directly coating the as-prepared colloid on the surface of a glassy carbon electrode produces an electrochemiluminescence (ECL) sensor. The electronic conductivity and electroactivity of PtNPs in composite film made the sensor exhibit faster electron transfer, higher ECL intensity of Ru(bpy)(3)(2+), and a shorter equilibration time than Ru(bpy)(3)(2+) immobilized in pure AQ film. Furthermore, it was demonstrated that the combination of PtNPs and permselective cation exchanger made the sensor exhibite excellent ECL behavior and stability and a very low limit of detection (1 x 10(-15) M) of tripropylamine with application prospects in bioanalysis. This method was very simple, effective, and low cost.

Kinetic study of paracetamol on prolidase activity in erythrocytes by capillary electrophoresis with Ru(bpy)(3)(2+) electrochemiluminescence detection

We explored the CE with Ru(bpy)(3)(2+) electrochemiluminescence detection for the kinetic study of drug-enzyme interaction. Effects of four nonsteroidal anti - inflammatory drugs including aspirin, paracetamol, sodium salicylate and phenacetin on prolidase (PLD) activity in erythrocytes were investigated. Aspirin enhanced PLD activity whereas the other three had inhibiting effects. This may reveal their different effects on the collagen biosynthesis and catabolism that influence tumor invasiveness. Kinetic study of paracetamol on PLD showed that the value of Michaelis constant Km for PLD was 1.23 mM. The mechanism of PLD inhibition by paracetamol is noncompetitive inhibition, and the inhibitor constant K-i value obtained in our research was 9.73 x 10(3) mu g/L.

Electrogenerated chemiluminescence sensing platform using Ru(bpy)(3)(2+) doped silica nanoparticles and carbon nanotubes

An effective electrogenerated chemiluminescence (ECL) sensor was developed by coimmobilization of the Ru(bpy)(2)(3+)-doped silica (RuDS) nanoparticles and carbon nanotubes (CNTs) on glassy carbon electrode through hydrophobic interaction. The uniform RuDS nanoparticles were prepared by a water-in-oil (W/O) microemulsion method and Ru(bpy)(3)(2+) doped inside could still maintain its high ECL efficiency. With such unique immobilization method, a great deal of Ru(bpy)(3)(2+) was immobilized three-dimensionally on the electrode , which could greatly enhance the ECL response and result in the increased sensitivity. On the other hand, CNTs played dual roles as matrix to immobilize RuDS nanoparticles and promoter to accelerate the electron transfer between Ru(bpy)(3)(2+) and the electrode. The as-prepared ECL sensor displayed good sensitivity and stability.

Novel chemical synthesis of Pt-Ru-P electrocatalysts by hypophosphite deposition for enhanced methanol oxidation and CO tolerance in direct methanol fuel cell

A novel method was developed to prepare the highly active Pt-Ru-P/C catalyst. The deposition of phosphorus significantly increased electrochemical active surface (EAS) area of catalyst by reduces Pt-Ru particle size. TEM images show that Pt-Ru-P nanoparticles have an uniform size distribution with an average diameter of 2 nm. Cyclic voltammetry (CV), Chronoamperometry (CA), and CO stripping indicate that the presence of non-metal phosphorus as an interstitial species Pt-Ru-P/C catalyst shows high activity for the electro-oxidation of methanol, and exhibit enhanced performance in the oxidation of carbon monoxide compared with Pt-Ru/C catalyst. At 30 degrees C and pure oxygen was fed to the cathode, the maximum power density of direct methanol fuel cell (DMFC) with Pt-Ru-P/C and Pt-Ru/C catalysts as anode catalysts was 61.5 mW cm(-2) and 36.6 mW cm(-2), respectively. All experimental results indicate that Pt-Ru-P/C catalyst was the optimum anode catalyst for direct methanol fuel cell.

Room temperature preparation of carbon supported Pt-Ru catalysts

A carbon supported Pt-Ru (Pt-Ru/C-T) catalyst can be prepared by a chemical reduction method in an aqueous solution with tetrahydrofuran (THF) at room temperature. The Pt-Ru particles possess high alloying, small average size and a low relative crystallinity. The electrocatalytic activity of the prepared Pt-Ru/C catalyst for methanol oxidation is much higher than that of commercial Pt-Ru/C (Pt-Ru/C-E) catalysts which have a similar average size and relative crystallinity, but the alloying extent is much lower than that in our Pt-Ru/C-T catalyst. The results illustrate that the alloying extent of Pt and Ru in the Pt-Ru/C catalyst plays an important role in the electrocatalytic activity of the Pt-Ru/C catalyst for methanol oxidation.

Electrogenerated chemiluminescence biosensor based on Ru(bpy)(3)(2+) and dehydrogenase immobilized in sol-gel/chitosan/poly(sodium 4-styrene sulfonate) composite material

A new electrogenerated chemiluminescence biosensor was fabricated by immobilizing ECL reagent Ru(bPY)(3)(2+) and alcohol dehydrogenase in sol-gel/chitosan/poly(sodium 4-styrene sulfonate) (PSS) organically modified composite material. The component PSS was used to immobilize ECL reagent Ru(bpy)(3)(2+) by ion-exchange, while the addition of chitosan was to prevent the cracking of conventional sol-gel-derived glasses and provide biocompatible microenvironment for alcohol dehydrogenase. Such biosensor combined enzymatic selectivity with the sensitivity of ECL detection for quantification of enzyme substrate and it was much simpler than previous double-layer design. The detection limit was 9.3 x 10(-6) M for alcohol (S/N = 3) with a linear range from 2.79 x 10(-5) to 5.78 x 10(-2) M. With ECL detection, the biosensor exhibited wide linear range, high sensitivity and good stability.

Highly sensitive electrogenerated chemiluminescence produced at Ru(bpy)(3)(2+) in Eastman-AQ55D-carbon nanotube composite film electrode

The electrochemistry and electrogenerated chemilurninescence (ECL) of tris(2,2-bipyridyl)ruthenium(II) ion-exchanged in Eastman-AQ-carbon nanotube (CNT) composite films were investigated at a glassy carbon (GC) electrode. Eastman-AQ55D is a poly (ester sulfonic acid) cation exchanger available in a commercial dissolved form. It is much more hydrophilic than Nafion due to its unique structure, so Ru(bpy)(3)(2+) does not diffuse into the hydrophobic region where it may lose its electroactivity as that in Nafion. The interfused CNT could act as electronic wires that connect the electrode with Ru(bpy)(3)(2+), which made the composite film much more electronically which finally led to the increasing of Ru(bpy)(3)(2+) conductive. Besides, the negatively charged CNT could also absorb some Ru(bpy)(3)(2+). Moreover, the strong electrostatic interaction between AQ and Ru(bpy)(3)(2+) made the composite films much more stable. The combination of AQ and CNT brings excellent sensitivity with the detection limit as low as 3 x 10(-11) M for TPA.

合金化程度对炭载Pt-Ru催化剂性能的影响

在含四氢呋喃(THF)的水溶液中,室温下用NaBH4还原H2PtC l6和RuC l3制得Pt-Ru/C催化剂.其Pt-Ru粒子的合金化程度较高,平均粒径较小,相对结晶度较低.因此对甲醇氧化的电催化活性远高于Pt-Ru粒子的平均粒径和相对结晶度相似的,而且Pt-Ru合金化程度低的商业化的E-TEK的Pt-Ru/C催化剂,表明Pt-Ru的合金化程度对Pt-Ru/C催化甲醇氧化的电催化活性有很大的影响.