Transition State Analysis of the Reaction Catalyzed by the Phosphotriesterase from Sphingiobium sp. TCM1

Organophosphorus flame retardants are stable toxic compounds used in nearly all durable plastic products and are considered major emerging pollutants. The phosphotriesterase from Sphingobium sp. TCM1 (Sb-PTE) is one of the few enzymes known to be able to hydrolyze organophosphorus flame retardants such as triphenyl phosphate and tris(2-chloroethyl) phosphate. The effectiveness of Sb-PTE for the hydrolysis of these organophosphates appears to arise from its ability to hydrolyze unactivated alkyl and phenolic esters from the central phosphorus core. How Sb-PTE is able to catalyze the hydrolysis of the unactivated substituents is not known. To interrogate the catalytic hydrolysis mechanism of Sb-PTE, the pH dependence of the reaction and the effects of changing the solvent viscosity were determined. These experiments were complemented by measurement of the primary and secondary 18-oxygen isotope effects on substrate hydrolysis and a determination of the effects of changing the pKa of the leaving group on the magnitude of the rate constants for hydrolysis. Collectively, the results indicated that a single group must be ionized for nucleophilic attack and that a separate general acid is not involved in protonation of the leaving group. The Brønsted analysis and the heavy atom kinetic isotope effects are consistent with an early associative transition state with subsequent proton transfers not being rate limiting. A novel binding mode of the substrate to the binuclear metal center and a catalytic mechanism are proposed to explain the unusual ability of Sb-PTE to hydrolyze unactivated esters from a wide range of organophosphate substrates

Alternating Current Electrohydrodynamic Printing of Microdroplets

This paper discusses the technology of orderly printing of microdroplets by means of electrohydrodynamic print (EHDP) with alternating current (AC). The AC electric field induces charges to reciprocate in the electrohydrodynamic charged jet and generates periodic alternation of electric field force, which facilitates the breakup of charged jets and injection of microdroplets. Microdroplets with a diameter of 100~300 μm can be printed with a frequency of 5~25 Hz via AC EHDP. Effects of process parameters on the microdroplet injection behaviors were investigated. A higher frequency of applied AC voltage led to a higher deposition frequency, but smaller diameters of printed droplets. Deposition frequency and droplet diameters increased with the increase of duty cycle and solution supply rate. AC pulse voltage has provided a novel way to study the control technology in EHDP, which would accelerate the application of inkjet printing in the field of micro/nanosystem production

Electrohydrodynamic Direct-Write Orderly Micro/Nanofibrous Structure on Flexible Insulating Substrate

AC pulse-modulated electrohydrodynamic direct-writing (EDW) was utilized to direct-write orderly micro/nanofibrous structure on the flexible insulating polyethylene terephthalate (PET) substrate. During the EDW process, AC electrical field induced charges to reciprocate along the jet and decreased the charge repulsive force that applied on charged jet. Thanks to the smaller charge repulsive force, stable straight jet can be built up to direct-write orderly micro/nanofibrous structures on the insulating substrate. The minimum motion velocity required to direct-write straight line fibrous structure on insulating PET substrate was 700 mm/s. Moreover, the influences of AC voltage amplitude, frequency, and duty cycle ratio on the line width of fibrous structures were investigated. This work proposes a novel solution to overcome the inherent charge repulsion emerging on the insulating substrate, and promotes the application of EDW technology on the flexible electronics

Electrohydrodynamic direct-writing of conductor-insulator-conductor multi-layer interconnection

Key Program of the National Natural Science Foundation of China [51035002]; National Natural Science Foundation of China [51305373]; Specialized Research Fund for the Doctoral Program of Higher Education of China [20120121120035]A multi-layer interconnection structure is a basic component of electronic devices, and printing of the multi-layer interconnection structure is the key process in printed electronics. In this work, electrohydrodynamic direct-writing (EDW) is utilized to print the conductor-insulator-conductor multi-layer interconnection structure. Silver ink is chosen to print the conductor pattern, and a polyvinylpyrrolidone (PVP) solution is utilized to fabricate the insulator layer between the bottom and top conductor patterns. The influences of EDW process parameters on the line width of the printed conductor and insulator patterns are studied systematically. The obtained results show that the line width of the printed structure increases with the increase of the flow rate, but decreases with the increase of applied voltage and PVP content in the solution. The average resistivity values of the bottom and top silver conductor tracks are determined to be 1.34 x 10(-7) Omega.m and 1.39 x 10(-7) Omega.m, respectively. The printed PVP layer between the two conductor tracks is well insulated, which can meet the insulation requirement of the electronic devices. This study offers an alternative, fast, and cost-effective method of fabricating conductor-insulator-conductor multi-layer interconnections in the electronic industry

Electrohydrodynamic direct - Writing of conductor - Insulator-conductor multi-layer interconnection

A multi-layer interconnection structure is a basic component of electronic devices, and printing of the multi-layer interconnection structure is the key process in printed electronics. In this work, electrohydrodynamic direct-writing (EDW) is utilized to print the conductor - insulator - conductor multi-layer interconnection structure. Silver ink is chosen to print the conductor pattern, and a polyvinylpyrrolidone (PVP) solution is utilized to fabricate the insulator layer between the bottom and top conductor patterns. The influences of EDW process parameters on the line width of the printed conductor and insulator patterns are studied systematically. The obtained results show that the line width of the printed structure increases with the increase of the flow rate, but decreases with the increase of applied voltage and PVP content in the solution. The average resistivity values of the bottom and top silver conductor tracks are determined to be 1.34 × 10-7 Ω·m and 1.39 × 10-7 Ω·m, respectively. The printed PVP layer between the two conductor tracks is well insulated, which can meet the insulation requirement of the electronic devices. This study offers an alternative, fast, and cost-effective method of fabricating conductor - insulator - conductor multi-layer interconnections in the electronic industry. ? 2014 Chinese Physical Society and IOP Publishing Ltd

Electrocatalytic oxidation of glucose on carbon nanotube/nanocrystalline TiO2 film loaded Pt complex electrode

Electrocatalytic oxidation of glucose on carbon nanotube/nanocrystalline TiO2 film loaded Pt (CNT/nanoTiO(2)/Pt) complex electrode was investigated by cyclic voltammetry and chronopotentiometry. The results indicated that CNT/nano-TiO2/Pt complex electrode has high catalytic activity to the electrochemical oxidation of glucose in alkaline media, and the peak current density of oxidation of glucose is up to 13 mA/cm(2), which is one time higher than that on a platinum electrode. The complex electrode performance is stable, and it is strong resistant to poisoning and difficult to oxidize oscillatory. It is a highly catalytic electrode for using in glucose fuel cell and glucose sensor

Electrocatalytic oxidation of ethanol on Pt/nanoTiO(2)-CNT complex catalysts

Pt/nanoTiO(2)-CNT complex catalysts were prepared by direct hydrolysis of Ti(OEt)(4) and electrochemical scan electrodepositing method. The results of XRD and SEM showed that the nanoTiO(2) (anatase) and Pt nanoparticles (size about 5 similar to 10 nm) were dispersed uniformly on CNT film surface. The electrocatalytic activity of Pt/nanoTiO(2)-CNT electrode was investigated by cyclic voltammetry and chronopotentiogram. The results indicated that Pt/nanoTiO(2)- CNT electrode (Pt loading was 0.32 mg . cm(-2)) exhibited high electrochemical activity surface area (51.8 m2. g(-1)) and very high electrocatalytic activity and stability for the electro-oxidation of ethanol at room temperature in atmosphere pressure. The oxidation peak potentials of ethanol were 0.59, 0.96, and 0.24 V, and the corresponding oxidation peak current sdensities were - 115, -113, and -75 mA . cm(-2). The high electrocatalytic activity and good stability can be attributed to the synergistic catalytic effect among nanocomposite