聚乙撑二氧噻吩导电聚合物上吗啡的电化学检测

在水相中电沉积制备得到了聚乙撑二氧噻吩(PEDOT)导电聚合物膜,研究了沉积电量、沉积电位等因素对聚合物膜的电化学活性及其在水溶液中检测吗啡的电化学响应的影响.结果表明,沉积电量为20～40mC,沉积电位为1.2V(相对于Ag/AgCl电极)时所得的聚合物膜对吗啡具有最高的电化学响应.在此基础上,研究了PEDOT膜修饰电极在不同浓度的吗啡水溶液中的电化学检测,发现在0.05～6mmol·L-1浓度范围内具有很好的线性响应,最低检测限为0.05mmol·L-1,相关系数达0.995.

AC measurements of spray-deposited CdS:In thin films

Indium doped cadmium sulfide thin films （CdS：In） were produced by the spray pyrolysis technique on glass substrates. AC measurements were used to investigate the electrical properties of the films depending on Brick-layer model for polycrystalline materials. The measurements were performed at room temperature in the dark and room light in the frequency range from 20 Hz to 1 MHz using coplanar indium electrodes. The data were analyzed by using Bode plots for the impedance Z and dielectric loss tang with frequencyf It is found that the impedance has no dependence on frequency in the low frequency region but has 1/f dependence in the high frequency region. One dielectric loss peak is obtained, which means the presence of a single relaxation time, and hence the films are modeled by just one RC circuit which represents the grains. This means that there is just one conduction mechanism that is responsible for the conduction in the bulk, due to electronic transport through the grains. Real values of the impedance in the low frequency region and relaxation times for treated and as-deposited fihns were estimated.

Preparation of calcium phosphate coatings on Mg-1.0Ca alloy

The calcium phosphate coatings were prepared by virtue of electrochemical deposition in order to improve the corrosion resistance of Mg-1.0Ca alloys in simulated body fluids.The chemical compositions,structures and morphologies of the coatings were investigated by energy dispersive spectroscopy(EDS),X-ray diffractometry(XRD)and scanning electron microscopy(SEM), respectively.The potentiodynamic electrochemical technique was employed to investigate the bio-degradation behavior of Mg-1.0Ca alloys with Ca-P coatings in Hank's solutions.The experimental results show that the deposited coatings predominately consist of flake-shape brushite(DCPD,CaHPO4·2H2O)crystallites.The corrosion resistance of the substrates with coatings is improved in Hank's solutions significantly.

Impact of Climate Change and Deforestation on Stream Discharge and Sediment Yield in Phu Luong Watershed, Viet Nam

The purpose of this paper is to apply ＂Soil and Water Assessment Tool （SWAT）＂ model to assess the impacts of climate change and deforestation on stream discharge and sediment yield from Phu Luong watershed in Northern Viet Nam. Among the three climate change scenarios B 1, B2, and A2, representing low, medium, and high levels of greenhouse gas emission, respectively were set up for Viet Nam, the B2 scenario was selected for this study. Two land use scenarios （S1-2030 and $2-2050） were formulated combination with climate change in WSAT simulation. In B2 climate change scenario, mean temperature increases 0.7℃（2030） and 1.3 ℃ （2050）; annual rainfall increases 2.1% （2030） and 3.80% （2050） respect to baseline scenario. The results show that the stream discharge is likely to increase in the future during the wet season with increasing threats of sedimentation.

Electrochemical Behavior of Electrodeposited Sn Films： Possible Negative Electrode for Na^＋ Rechargeable Batteries

Tin films on copper substrate, obtained by electrodeposition procedure, were structural and electrochemical characterized. In particular to investigate the possibility to use such metal as possible negative electrode in Na＋ rechargeable batteries, EPS （electrochemical potential spectroscopy） and galvanostatic charge/discharge cycling of the electrodes were investigated, at room temperature in organic electrolyte. Three crystalline and one amorphous phases were identified as well as high discharge capacity （738 mAb/g） was obtained after 4 cycles. Unfortunately material fading, due to the internal stress during sodiation/desodiation process, causes poor cyclability.

Evolution of Electron Velocity Distribution during ECRH and Heating Effect Analysis

1 Electron velocity distributions and energy deposition of ECW Two set of soft X-ray spectra detection system consist of high performance sillicon drift detectors （SDD） , high speed A/D transform and processing software, software pulse height analyzer （SPHA）. They are installed at mid plane （ r=0 ） and undermid plane （ r=-16.4 cm ） of HL-2A tokamak respectively to measure the time evolution of soft X-ray spectra. According to spectrum, the thermal electron and superthermal electron temperatures are derived. Because of the ratio of peak counts to background counts is very high （p/b 〉1 400-3000 ） ,

CdTe量子点敏化TiO_2纳米棒光电极的制备及分析

利用电化学沉积法在TiO2纳米棒阵列上沉积了CdTe量子点,通过调节沉积时的电量使整个TiO2纳米棒上覆盖了致密均匀的CdTe量子点,CdTe和TiO2形成了核壳结构。研究了沉积电量对FTO/TiO2/CdTe光电极的结构及光电性能的影响,发现随着沉积电量的增大,FTO/TiO2/CdTe光电极的吸收边发生红移。当沉积电量为0.9C时,在光强为0.1 W/cm2、AM 1.5 G标准模拟太阳光照射下,所制光电极产生最大的饱和光电流密度3.23×10–3A/cm2。

4H-SiC trench gate MOSFETs with field plate termination

Field plate(FP)-terminated 4H-SiC trench gate MOSFETs are demonstrated in this work.N+/P?/N?/N+multiple epitaxial layers were grown on 3-inch N+type 4H-SiC substrate by chemical vapor deposition(CVD),and then the 4H-SiC trench gate MOSFETs were fabricated based on the standard trench transistor fabrication.Current-voltage measurements in forward and reverse bias have been performed on different devices with and without FP protections.It is found that more than 60%of the devices protected with FP termination are able to block 850 V.The measurements also show that the devices have the small leakage currents 0.15 nA at 600 V and 2.5 nA at 800 V,respectively.The experimental results also were compared with the simulated results,which show good agreement with each other in the trend.The limited performance of the devices is mainly because of the damage induced on the trench sidewalls from the etching process and the quality of the SiO2 films.Therefore,the 4H-SiC trench gate MOSFETs are expected to be optimized by reducing the etching damage and growing high-quality SiO2 dielectric films.

An Electrochemically Assisted Mechanically Controllable Break Junction Approach for Single Molecule Junction Conductance Measurements

We report an electrochemically assisted mechanically controllable break junction （EC-MCBJ） approach to investigating single molecule conductance. Electrode pairs connected with a gold nanobridge were fabricated by electrochemical deposition and then mounted on a homebuilt MCBJ platform. A large number of Au- molecule-Au junctions were produced sequentially by repeated breaking and reconnecting of the gold nanobridge. In order to measure their single molecule conductance, statistical conductance histograms were generated for benzene-l,4-dithiol （BDT） and 4,4＇-bipyridine （BPY）. The values extracted from these histograms were found to be in the same range as values previously reported in the literature. Our method is distinct from the ones used to acquire these previously reported literature values, however, in that it is faster, simpler, more cost-effective, and changing the electrode material is more convenient.

Synergy effects on Sn-Cu alloy catalyst for efficient CO2 electroreduction to formate with high mass activity

To acquire the synergy effects between Sn and Cu for the jointly high Faradaic efficiency and current density,we develop a novel strategy to design the Sn-Cu alloy catalyst via a decorated co-electrodeposition method for CO2 electroreduction to formate.The Sn-Cu alloy shows high formate Faradaic efficiency of 82.3%±2.1% and total C1 products Faradaic efficiency of 90.0%±2.7% at^-1.14 V vs.reversible hydrogen electrode(RHE).The current density and mass activity of formate reach as high as(79.0±0.4)mA cm^-2 and(1490.6±7.5)m A mg^-1 at^-1.14 V vs.RHE.Theoretical calculations suggest that Sn-Cu alloy can obtain high Faradaic efficiency for CO2 electroreduction by suppressing the competitive hydrogen evolution reaction and that the formate formation follows the path of CO2→HCOO*→HCOOH.The stepped(211)surface of Sn-Cu alloy is beneficial towards selective formate production.

Realization of low contact resistance close to theoretical limit in graphene transistors

Realizing low contact resistance between graphene and metal electrodes remains a well-known challenge for building high-performance graphene devices. In this work, we attempt to reduce the contact resistance in graphene transistors and further explore the resistance limit between graphene and metal contacts. The Pd/graphene contact resistance at room temperature is reduced below the 100 Ω·μm level both on mechanically exfoliated and chemical-vapor-deposition graphene by adopting high-purity palladium and high-quality graphene and controlling the fabrication process to not contaminate the interface. After excluding the parasitic series resistances from the measurement system and electrodes, the retrieved contact resistance is shown to be systematically and statistically less than 100 Ω·μm, with a minimum value of 69 Ω·μm, which is very close to the theoretical limit. Furthermore, the contact resistance shows no clear dependence on temperature in the range of 77-300 K; this is attributed to the saturation of carrier injection efficiency between graphene and Pd owing to the high quality of the graphene samples used, which have a sufficiently long carrier mean-free-path.