Temperature Effect on Hydrogen Evolution Reaction at Au Electrode

The temperature dependence of hydrogen evolution reaction （HER） at a quasi-single crystalline gold electrode in both 0.1 mol/L HCl04 and 0.1 mol/L KOH solutions was investigated by cyclic voltammetry. HER current displays a clear increase with reaction overpotential （η） and temperature from 278-333 K. In 0.1 mol/L HClO4 the Tafel slopes are found to increases slightly with temperature from 118 mV/dec to 146 mV/dec, while in 0.1 mol/L KOH it is ca. 153±15 mV/dec without clear temperature-dependent trend. The apparent activation energy （Ea） for HER at equilibrium potential is ca. 48 and 34 kJ/mol in 0.1 mol/L HC104 and 0.1 mol/L KOH, respectively. In acid solution, Ea decreases with increase in η, from Ea-37 kJ/mol （η=0.2 V） to 30 kJ/mol （η=0.35 V）. In contrast, in 0.1 mol/L KOH, Ea does not show obvious change with U. The pre-exponential factor （A） in 0.1 mol/L HC104 is ca. 1 order higher than that in 0.1 mol/L KOH. Toward more negative potential, in 0.1 mol/L HC104 A changes little with potential, while in 0.1 mol/L KOH it displays a monotonic increase with U. The change trends of the potential-dependent kinetic parameters for HER at Au electrode in 0.1 mol/L HClO4 and that in 0.1 mol/L KOH are discussed.

Electrochemical Behavior and Determination of Trifluoperazine at Decanethiol Self-Assembled Monolayer Modified Gold Electrodes

The electrochemical behavior of trifluoperazine at decanethiol self-assembledmonolayer (SAM) modified gold electrodes (i. e. C_(10) H_(21) SH/Au) has been studied,Trifluoperazine can effectively accumulate on C_(10) H_(21) SH/Au electrodes and generate asensitive anodic peak at about 0.63 V (vs. SCE) in 0.05 mol/L pH 9.4 Na_2 B_4 O_7 buffer solution.Under the selected conditions, the anodic peak current was linear to trifluoperazine concentrationin the range of 5.0 X 10^(-7)-3.O X 10^(-3) mol/Lwith correlation coefficient of 0.997, thedetection limit was 3.0 X 10^(-5) mol/L. This method was applied to the determination oftrifluoperazine in drug samples and the recovery was 97.3%-104.0% It was found that sodium dodecylsulfate (SDS) could make the anodic peak current increase. In the presence of SDS, the peak at about0.63 V turned into two peaks, resulting from the change of the electrochemical mechanism.

The Molecular Recognition Characteristics of ω-MercaptoMethoxy Poly(Ethylene Glycol) Self-assembled Monolayer at Gold Electrode and the Detection of Dopamine in Serum

Self assembled monolayers (SAMs) of to-mercapto methoxy poly(ethylene glycol)(MPEG) on gold electrode were used as a means to detect dopamine. Dopamine (DA) had good response at the MPEG film electrode and ascorbic acid (AA) was repelled from the SAMs. TheMPEG film is a biocompatible film, there was no adsorption of biosample and no inactivation atelectrode surface when it was used to detect DA in biosamples.

pH Effect on Oxidation of Hydrogen Peroxide on Au(111) Electrode in Alkaline Solutions

The hydrogen peroxide oxidation reaction (HPOOR) on Au(111) electrode in alkaline solutions with pH values ranging from 10 to 13 was examined systematically. HPOOR activity increased and the slope of the i-E curve decreased with increasing pH. HO2- is suggested to be the main reactive intermediate for HPOOR in alkaline media. The fast kinetics for HPOOR in alkaline solution is facilitated by the electrostatic interaction between the positively charged electrode and the reactive anions (i.e., HO2- and HO-), which increases the concentration of these reactants and the thermodynamic driving force for HO2- oxidation at the reaction plane.

Direct Electrochemistry and Electrocatalysis of Hemoglobin at PAMAM Dendrimer-MWNTs-Au Nanoparticles Composite Film Modified Glassy Carbon Electrode

The direct electron transfer of hemoglobin at the PAMAM-MWNTs-AuNPs composite film modified glassy carbon electrode was studied. In a phosphate buffer solution（PBS, pH=7.0）, the formal potential（E^0） of Hb was -0.105 V versus SCE, the electron transfer rate constant was 4.66 s-1. E^0＇ of Hb at the modified electrode was linearly varied in a pH range of 5.0-8.0 with a slope of-49.2 mV/pH. The Hb/PAMAM-MWNTs-AuNPs/GCE gave an excellent electrocatalytic response to the reduction of hydrogen peroxide. The catalytic current increased linearly with H2O2 concentration in a range of 1.0× 10^-6 to 2.2× 10^-3 mol/L. The detection limit was 2.0× 10^-7 mol/L at a signal to noise ratio of 3. The Michaelis-Menten constant（Km^app） was 2.95 mmol/L.

Preparation and electrocatalytic property of Au-Pt/SnO_2/GC composite electrode

Au-Pt/SnO2/GC composite electrode was prepared by self-assembling Au-Pt nanoparticles on SnO2 film, which was deposited on actived glassy carbon （GC）. Atomic force microscopy （AFM） and scanning electron microscopy （SEM） images revealed that dense and uniform Au-Pt particles with 25-nm diameter were dispersed on SnO2 film. X-ray photoelectron spectroscopy （XPS） results proved that there was an interaction between Au-Pt nanoparticles and SnO2 support. Electrochemical experiments showed that Au-Pt/SnOz/GC composite electrode had a good electrocatalytic activity to the oxidation of methanol

Anion Adsorption on an Au Colloid Monolayer Based Cysteamine-Modified Gold Electrode

Anion adsorption behavior on Au colloid surface was investigated in virture of depositing monolayers of Au colloid on the self-assembled monolayers of cysteamine on a gold electrode. Po- tential-dependent anion adsorption-desorption waves via the nonfaradaic current were obtained by means of cyclic voltammetry at Au coltoid-modified gold electrodes in the potential range of -2 00-600 mV. The adsorption sequence in the order of adsorption peak potentials (Epa) is OH- >citrate3 ->H2PO4- >Cl->SO42->ClO4->NO3-. Among them, citrate3- exhibited an en- tirely irreversible adsorption. A rise in temperature can increase the rates of adsorption-desorp- tion and improve the reversibility of the adsorption-desorption of Cl-, SO42-, ClO4-, NO3- and H2PO-4. The adsorption peak potentials shifted more negatively for Ca. 63 mV as the anion con- centrations were increased by a decade factor. The change of pH from 7 to 1 slightly affected the adsorption peak potentials of Cl- and NO3-. Au colloids with a smaller size (16 nm) gave rise to a better reversibility of the adsorption-desorption process and lower adsorption currents. The ex- perimental results of citrate ions adsorption on Au colloid surface show that Au colloids with a smaller size prepared by sodium citrate method exhibited a higher stability in the solution in com- parison to those with larger sizes because of its higher ratio of charge/mass. In other words, the smaller gold nanoparticles are covered with citrate ions monolayer that can also be formed at larg- er gold nanoparticles by means of electrochemical scan.

The Self-Assembling Growth of Copper Nanowires for Transparent Electrodes

Long(15-40 μm), thin(diameter of 20 ± 5 nm), and well-dispersed CuNWs Cu nanowires were prepared. The high-resolution TEM and selected area electron diffraction showed that the CuNWs were single-crystalline. To investigate the growth mechanism, we examined the microstructure of these CuNWs at different reaction time. It was found that the CuNWs were actually formed through the self-assembling of Cu nanoparticles along the [110] direction. The transparent electrodes fabricated using the CuNWs achieved a high transparency of 76 % at 31±5 Ω/□.

A New Thionine Modified Electrode by Anchorage to Bi-(2-aminoethyl)-aminodithiocarboxyl Acid Self-assembled Monolayers through Coordination with Cu^(2+#)

A new method for preparing chemically modified gold electrode by anchoring thionine to self-assembled bi - (2 -aminoethyl) -aminodithiocarboxyl acid(BANTC) monolayers through coordination with Cu2+ is described. This thionine modified electrode exhibits two-new redox couples.Two protons were involved in the electrochemical process undergone by the couple I in the pH range of 5.0-10.0. The apparent surface electron transfer rate constant is about 0.050s-1.

A Gold Electrode QCM Study on the Self-Assembling Process of Thioglycollic Acid in Aqueous Solution

In this letter, the self-assembling process of thioglycollic acid on gold in aqueous solutions was studied by QCM technique. Frequency information suggests bilayer or multilayer adsorbate formation in 0.5 mol/L HCl solution but only monolayer one in 0.5 mol/L KOH solution. This phenomenon is explained by hydrogen bond effect.

Study of enzyme biosensor based on carbon nanotubes modified electrode for detection of pesticides residue

The paper describes a controllable layer-by-layer （LBL） self-assembly modification technique of multi-walled carbon nanotubes （MWNTs） and poly（diallyldimethylammonium chloride） （PDDA） towards glassy carbon electrode （GCE）, Acetylcholinesterase （ACHE） was immobilized directly to the modified GCE by LBL self-assembly method, the activity value of AChE was detected by using i-t technique based on the modified Ellman method. Then the composition of carbaryl were detected by the enzyme electrode with 0.01U activity value and the detection limit of carbaryl is 10^- 12 g L ^-1 so the enzyme biosensor showed good properties for pesticides residue detection.

Enhanced Hole-Injection Property in an OLED with a Self-assembled Monolayer of Hole-Transporting TPD on Thin Au as the Anode

A thioester-functionalized triphenylamine hole-transporting molecule （TPD-SAc） was synthesized and self-assembled to form a monolayer on an ultra-thin Au film supported on indium-tin oxide glass. The modified surface was characterized by aqueous contact angle, ellipsometer, atomic force microscopy, X-ray photoelectron spectroscopy, and ultraviolet pho- toelectron spectrometer to substantiate the formation of compact and pinhole-free monolayers. The modified organic light emitting diode device [indium-tin oxide/Au （5 nm）/self-assembled monolayers （SAM）/TPD （50 nm）/Alq3 （40 nm）/TPBI （15 nm）/LiF （1 nm）/A1 （100 nm）] showed a luminance of 7303.90 cd/m^2 and a current efficiency of 8.49 cd/A with 1.78 and 2.29-fold increase, respectively, compared to the control device without SAM. The improvements were attributed to the enhanced compatibility of the organic-inorganic interface, matched energy level by introduction of an energy mediating step and superior hole-injection property of SAM molecules.

Environment-Friendly Determination of Low Concentration Azobenzene β-Cyclodextrin-Modified Electrode

Objective To study environment-friendly determination of azobenzene in trace amounts using β-cyclodextrin （β-CD）-modified Au electrode. Methods β-CD-modified Au electrode was fabricated with a two-step approach, and then a gold electrode modified with β-CD was used to detect azobenzene by employing Osteryoung square wave voltammetry. Results The modified electrode could detect azobenzene, showing a good linearity between the electrochemical current and concentration. Conclusion Although the electrochemical current is related with concentration, the detection limit is around 1 .0 ×10^-10 mol/L. This study may provide a new environment-friendly approach for monitoring water quality.

An EQCM Study of the Electrochemical Behaviors of Polycrystalline Gold Electrode in Sulfuric Acid Solution

The electrochemical quartz crystal microbalance (EQCM) was applied to study the electrochemical behaviors of polycrystalline Au in sulfuric acid solution. The large mass change observed in the doublelayer region was attributed to the partly discharged adsorption of sulfate anions with the co-adsorption of H2O. According to the observed EQCM frequency response, the formation mechanism of surface oxide was reasonably postulated, in which the roles of the adsorbed anions and the co-adsorbed H2O were particularly emphasized.

A Study on a Partially Immersed Gold Electrode Using an Electrochemical Quartz Crystal Impedance System

The electrochemical quartz crystal impedance system (EQCIS) has been used for the study of a partially immersed Au electrode in 0.2 mol/L NaClO4 aqueous solution. The influences of the immersed area and height of the electrode on the EQCIS responses were evaluated, showing the highest response sensitivity to liquid loading at the center of the piezoelectric quartz crystal electrode. The increase in the immersed height of the Au electrode at oxygen reduction potentials during potential cycling was measured by this technique.

Thermo-controllable self-assembled structures of single-layer 4,4"-diamino-p-terphenyl molecules on Au(110)

Here we report the thermo-controllable self-assembled structures of single-layer 4, 4＇＇-diamino-p-terphenyl（DAT）molecules on Au（110）, which are investigated by scanning tunneling microscopy（STM） combined with density functional theory（DFT） based calculations. With the deposition of monolayer DAT molecules on Au（110） and subsequent annealing at 100℃, all DAT molecules adsorb on a（1×5） reconstructed surface with a ladder-like structure. After annealing the sample at about 200℃, STM images show three distinct domains, including DAT molecules on a（1×3） reconstructed surface, dehydrogenated molecules with two hydrogen atoms detached from one amino group（–2H-DAT） on a（1×5）reconstructed surface and dehydrogenated molecules with four hydrogen atoms detached from two amino groups（–4HDAT） on a（1×3） reconstructed surface through N–Au bonds. Furthermore, after annealing the sample to 350℃, STM image shows only one self-assembled structure with –4H-DAT molecules on a（1×3） reconstructed surface. Relative STM simulations of different self-assembled structures show excellent agreements with the experimental STM images at different annealing temperatures. Further DFT calculations on the dehydrogenation process of DAT molecule prove that the dehydrogenation barrier on a（1×5） reconstructed surface is lower than that on（1×3） one, which demonstrate the experimental results that the formation temperature of a（1×3） reconstructed surface is higher than that of a（1×5） one.

Fabrication of ferrocenyl glutathione modified electrode and its application for detection of cadmium ions

l＇-cysteaminecarbonyl-1-glutathionecarbonyl-ferrocene （Fc-GSH） was synthesized from ferrocene dicarboxylic acid and reduced glutathione （GSH） with 4 steps. IR and 1^H-NMR were used to characterize the products. Then Fc-GSH was immobilized on the surface of gold electrode. Cyclic votammetry （CV） was adopted to investigate the electrochemical properties of this Fc-GSH modified electrode in the absence and presence of Cd^2＋ aqueous solutions. The peak oxidation potential （Ea） and reduction potential （Ec） of Fc-GSH modified electrode were observed at Ea= 0.74 V and Ec= 0.64 V （vs Ag/AgCl） before the accumulation of Cd^2＋. This redox process is a monoelectron chemical reaction. The anodic shift is about 80 mV in the presence of 20 nmol/L of Cd^2＋ aqueous solution. Moreover, this shift is in proportion to the concentration of Cd^2＋ when the concentration of Cd^2＋ is lower than 20 nmol/L. So the modified electrode can be used as probes to detect cadmium ions with the limit of 0.1 nmol/L by cyclic voltammetry.

SnO_(2)-Au-PANI复合材料改性商用NH_(3)传感墨水及其性能研究

采用点胶印刷技术,以商用墨水(kz-sense-103)在棉布基底上考察电极指间距和电极对数对氨气(NH_(3))传感性能的影响,确定了指间距为1 mm、传感器性能最佳的6对叉指电极。研究了以SnO_(2)-Au-PANI复合物改性商用墨水获得的改性墨水的传感性能。结果表明:经改性墨水制备的传感器实际检测限可达到5×10^(-6)的NH_(3),性能远远优于商用墨水,且具有优异的时间、温度和湿度稳定性,并能够从H_(2)、CO、SO_(2)和NH_(3)中区分出NH_(3),表明该传感器墨水适合在日常及工业环境中对NH_(3)的监测应用。

Nafion-Au-Nafion修饰玻碳电极循环伏安法测定莱克多巴胺

用Nafion-Au-Nafion修饰玻碳电极,探讨莱克多巴胺的电化学行为,建立了检测莱克多巴胺的循环伏安电化学传感方法。实验结果表明,在pH值2.0,B-R为支持液,富积时间120 s,扫描速度50 mV·s^(-1),电位为1.1 V的条件下,循环伏安法测定莱克多巴胺检测限可达2μg·L^(-1),线性范围为0.02～20 mg^(-1),操作简便,检测迅速(检测时间不超过5 min),适合大批量样品检测,具有很好的应用前景。

Sb在Au电极上不可逆吸附的电化学过程(英文)

用电化学循环伏安法和电化学石英晶体微天平(EQCM)技术研究了Sb在Au电极上不可逆吸附的电化学过程.研究结果表明,在-0.25V到0.18V(vs SCE)范围内,Sb可在Au电极上稳定吸附,并且在0.15V附近出现特征氧化还原峰.根据EQCM实验数据,在电位0.18V时,Sb在Au电极上的氧化产物是Sb2O3;同时Sb的吸附阻止了电解液中阴离子和水在Au电极上的吸附.当电极电位超过0.20V时,Sb2O3会被进一步氧化成Sb5+化合物,同时逐渐从Au电极表面脱附.