Study of salt permeation process into Vigna angularis using Ag/AgCl electrodes

In this work we report a novel method that can monitor in vivo the salt permeation process into a plant Vigna angularis using two Ag/AgCl electrodes. The method is based on the electromotive force (emf) measurement using two Ag/AgCl electrodes, one inserted into the V. angularis pith cavity and the other placed into saline ([NaCl]=1 M) surrounding the roots. Temporary change of emf ranging from 0 to ca. 0.115 V was measured in vivo using the system, and the possible physiological phenomenon during the period was discussed.     

Properties of Ag/AgCl electrodes fabricated with IC-compatible technologies

The purpose of this work is to fabricate and characterize Ag/AgCl electrodes made on a silicon chip at the wafer level with integrated circuit-compatible fabrication techniques. Such electrodes are useful as reference electrodes in several kinds of chemical sensors. Two types of electrode were investigated. The first type uses an evaporated AgCl layer that is patterned with lift-off photolithography. The second type is formed by exposing a selected part of the silver substrate to a KCrO₃Cl solution. Both types of electrode give the thermodynamically expected potential response to variations of Cl⁻ ion concentration. The potential generated by the KCrO₃Cl-formed electrodes was more stable, however. Auger electron spectroscopy depth profiles indicate that immersion in a KCrO₃Cl solution produces a thin layer of AgCl on top of a layer of AgO. The low electronic resistance of AgO then reduces the measured series resistance of the KCrO₃Cl-formed electrodes. Impedance plane plots and the impedance as a function of frequency were measured for both types of electrode, and the impedance of the evaporated AgCl electrodes was indeed considerably higher. The impedance measurements could be successfully modelled by assuming a Randles equivalent circuit for the AgCl/electrolyte interface. For the KCrO₃Cl-formed electrodes, the impedance was modified by the porosity these electrodes manifested.     

Preparation and photocatalytic activity of carbon dot/Ag/AgCl

CD (carbon dot)/Ag/AgCl compound photocatalysts with different compounding degrees were prepared via a precipitation method, and their physiochemical properties were characterized by X‐ray diffraction, FE‐SEM, UV–vis and the like. Through the degradation experiment of methyl orange (MO), the effects of different compounding amount and methyl orange concentration on photocatalytic degradation were investigated to find the best ratio. It was found the photocatalytic activity of CD/Ag/AgCl was significantly higher than Ag/AgCl, and the best compounding dosage was 6 mg/l carbon dot. The degradation rate of CD/Ag/AgCl was lower when the initial MO concentration was higher. Five repeated experiments were conducted to test the stability of the catalysts, and showed the MO degradation rates were all above 85%, indicating the CD/Ag/AgCl compound photocatalysts all showed high stability and repeatability. The reaction mechanism of CD/Ag/AgCl photocatalyst was studied by electrochemical experiments and ESR experiments. The results show that the doping of CD effectively improves the photocatalytic degradation ability of MO.     

基于Ag/AgCl丝双涂膜司帕沙星选择电极的研制与应用

以Ag/AgCl丝为基体依次外涂含0.1 mol/L KCl的琼脂凝胶膜及含四苯硼-司帕沙星缔合物的PVC膜,制备了一种双涂膜司帕沙星选择电极。采用正交设计法,研究了离子缔合物的种类、活性物在膜中的浓度及增塑剂三因素对电极的影响。电极的线性范围为1.0×10-5~1.0×10-3mol/L,检出限为2.4×10-6mol/L,斜率为28.8 mV/decade(16℃),可直接用于司帕沙星片剂的含量测定,回收率为99.6%~101.1%,结果与文献法一致。     

Ag/AgCl/GO可见光催化剂的制备及其性能

采用微乳液法成功制备了AgCl/GO复合可见光催化剂,利用XRD、TEM、FT-IR、UV-vis对复合光催化剂进行了表征.以甲基橙为目标污染物,考察AgCl/GO可见光催化降解活性.研究结果显示AgCl粒子实际上是以Ag/AgCl纳米结构形式较好地负载在石墨烯表面上.在甲基橙为20 mg·L~(-1),催化剂为0.05g的条件下,可见光照射100min后甲基橙的降解率达到91%以上.     

Ag/AgCl复合纳米粒子/聚丙烯腈纳米纤维膜的制备及可见光催化降解甲基橙

通过电纺丝法结合原位还原及原位氧化反应, 成功制备了均匀负载Ag/AgCl复合纳米粒子/聚丙烯腈(PAN)复合纳米纤维膜. 首先利用电纺丝技术制备了PAN/AgNO₃复合纳米纤维, 然后用乙二醇将硝酸银还原成银纳米粒子, 最后采用三氯化铁溶液对材料进行原位氧化. 所得纤维膜材料可以作为高效的可见光催化剂, 具有高可见光利用率, 优异的柔性和高光催化动力学等特性.     

Ag/AgCl/BiOIO3三元复合物光催化剂的性能增强机制

半导体光催化技术是一种环境友好技术,它既能在温和条件下应用于环境领域——利用光能降解有机和无机污染物,又可应用于能源领域——将低密度的太阳能转化为高密度的洁净能源,因而在解决环境污染和能源匮乏问题方面展现出巨大的应用潜力.最近,一种新型Bi基光催化剂, BiOIO3,表现出优异的紫外光催化性能.它由层状[Bi2O2]2+和[IO3]?组装而成,带隙为3.1 eV左右.然而,其较大的带隙限制了其对太阳光的利用.近年来,多种方法如金属掺杂、非金属掺杂、半导体复合、光敏化改性和加氢处理被用来提高半导体的光催化效率.其中,以Ag/AgX (X=Cl, I和Br)作为助催化剂可提高体系的可见光吸收和载流子的分离能力,从而增强光催化性能.基于此,我们设计并合成了一种新型的三元光催化剂.首先采用水热法合成了BiOIO3纳米片,然后在室温条件下原位引进Ag/AgCl,制备了Ag/AgCl/BiOIO3三元异质结构.与Ag/AgCl和纯的BiOIO3相比,该三元Ag/AgCl/BiOIO3复合物光催化剂对NO表现出优异的可见光光催化去除性能.本文采用X射线衍射(XRD)、X射线光电子能谱(XPS)、扫描式电子显微镜(SEM)、电化学测试(光电流和阻抗谱)和紫外-可见漫反射光谱(UV-Vis)等表征手段研究了Ag/AgCl/BiOIO3光催化性能增强的机制. SEM结果表明,制备的Ag/AgCl/BiOIO3三元复合物为纳米颗粒和纳米片形貌, Ag/AgCl的引入对BiOIO3形貌影响不大. XRD和XPS测试结果表明,与纯的BiOIO3相比,随着Ag/AgCl 的加入,复合物的峰位置发生了明显位移,表明Ag, AgCl和BiOIO3三组分间存在强的相互作用.光电流响应图谱表明,随着Ag/AgCl的加入, Ag/AgCl/BiOIO3的光电流强度明显增强,同时阻抗谱的圆弧直径明显减小,表明电子和空穴的分离能力增强. UV-Vis图谱中, BiOIO3在可见光区几乎没有吸收,而三元复合物表现出明显的可见光吸收,且随着Ag/AgCl量的增加,复合物的可见光吸收增强,该吸收归结于复合物中Ag的表面等离子体吸收.结合之前报道的光催化剂体系如Ag/AgCl和Ag/AgCl/TiO2,我们提出了Ag/AgCl/BiOIO3复合物光催化剂性能增强的机制.在可见光照射下, Ag0因其表面等离子体吸收而产生电子空穴对.由于功函数不同, Ag和BiOIO3之间形成肖特基势垒.电子从Ag0表面转移到BiOIO3的导带上, BiOIO3导带上电子的电势不足以把O2氧化成?O2?,但电子能以多电子的形式与O2和H+生成水.同时, Ag0表面的空穴能将AgCl表面的Cl?氧化成Cl0.光照诱导AgCl表面的部分Ag+离子被还原,所以AgCl粒子的表面带负电荷. Cl0是活性自由基,能够氧化去除NO,反应之后自身被还原成Cl?.由此可见,在三元复合光催化剂中, Ag0在可见光照射下因其表面等离子体效应产生电子空穴对,随后BiOIO3有效地分离了光生载流子,使得复合材料能有效地利用光生电子和空穴.故三元Ag/AgCl/BiOIO3复合物光催化剂增强的光催化性能可归结于Ag的表面等离子体吸收和BiOIO3的载流子分离能力.该结果有助于设计和制备具有优异的光催化性能的BiOIO3基材料.     

Evaluation of mercury coated glassy carbon electrodes for oscillographic polarography

The suitability of a mercury film electrode formed over a glassy carbon substrate for oscillographic polarography has been studied. The data obtained show that it is possible to get well-developed oscillograms characteristic of the depolariser (in the concentration range 10^∮5–3×10^?4M) in solution which are similar to those obtained with a dropping mercury electrode. For quantitative analysis the mercury film electrode has been found to have limited applicability since the indentations have been found to be time-dependent.     

Long-term equilibrium potential and electrochemical impedance study of Ag/AgCl electrodes used in Harned Cell measurements of pH

A long term study of the voltage and electrochemical impedance characteristics of Ag/AgCl electrodes used in Harned Cell measurement of pH is presented. By all the measures investigated the electrodes are shown to degrade only slowly until approximately 200 days after manufacture, after which time the rate of degradation and critical failure of the electrodes increases. The absolute voltage drift of the electrodes may not be easily measured, so parameters determined directed or indirectly by electrochemical impedance spectroscopy have been assessed as a method to produce an alternative indication of electrode integrity. In this respect, resistance to charge transfer has been shown to be a very sensitive measure of changes in the characteristics of the electrodes, and the most closely related to the observed changes in voltage. Evidence is presented to support the hypothesis that the majority of electrode degradation (excluding critical failure) comes from the increased blocking of the microporous structure of the electrodes.     

Glassy carbon electrodes coated with cellulose acetate for adsorptive stripping voltammetry

The utility of glassy carbon electrodes coated with cellulose acetate for adsorptive stripping voltammetry of oxidizable organic compounds is evaluated. This surface modification alleviates the co-adsorption problem commonly encountered at conventional electrodes. Interferences from electro-inactive surfactants and, in certain situations, from adsorbable electroactive substances, are minimized. Quantitation of the drugs, chlorpromazine and trimipramine, is not affected by the presence of up to 120 mg 1^?1 albumin or gelatin. The chlorpromazine response is not affected by the bilirubin or perphenazine peaks which overlap at uncoated electrodes. The adsorptive stripping response at the coated electrode is evaluated with respect to hydrolysis time, preconcentration time, concentration dependence, reproducibility, and other variables. The detection limit for chlorpromazine is 1.3 × 10^?8 M (5-min preconcentration). Applicability to assays of urine and serum samples is illustrated.     

Synthesis and photocatalytic performance of Ag/AgCl/ZnO tetrapod composites

Ag/AgCl is a visible-light plasmonic photocatalyst that has attracted considerable attention because of its high visible-light absorption and activity owing to the surface plasmon resonance of noble-metal nanoparticles. In this study, Ag/AgCl/ZnO tetrapod composite was prepared by introducing ZnO tetrapods into Ag/AgCl prepared by a polydopamine reduction route. Ag/AgCl was densely deposited on the three-dimensional support framework provided by the ZnO tetrapods. The framework possessed a certain degree of porosity, thereby improving the specific surface area of the Ag/AgCl/ZnO composite. The interaction of ZnO with Ag/AgCl further increased the separation and transfer of electron–hole pairs. The Ag/AgCl/ZnO composite showed excellent photocatalytic activity and good stability. Under xenon lamp irradiation for 20 min, degradation of rhodamine B reached 90%. After four recycling tests, degradation remained stable without any sign of reduction. Ag/AgCl/ZnO tetrapod composite is shown to be a kind of green photocatalyst offering high activity, good stability, and recyclability.

     

Environmentally benign chitosan as precursor and reductant for synthesis of Ag/AgCl/N-doped carbon composite photocatalysts and their photocatalytic degradation performance

In this study, we reported a novel Ag/AgCl loaded N-doped carbon composite photocatalyst (Ag/AgCl/NC) which was fabricated by a facile and green method. The composite was prepared only by two simple steps. Firstly, the Ag/N-doped carbon (Ag/NC) was prepared by one-step hydrothermal treatment; during this progress the environmentally benign and renewable natural chitosan was used as not only reducer and stabilizer, but also as a nitrogen source and carbon source. Secondly, Ag/AgCl/NC composite was synthesized via in situ oxidation reaction by adding FeCl₃. The Ag/AgCl/NC composite was characterized using X-ray diffraction, transmission electronic microscopy, energy dispersive X-ray spectra, UV-visible diffused reflectance spectra, X-ray photoelectron spectroscopy and nitrogen adsorption-desorption measurements, respectively. The obtained Ag/AgCl/NC composite exhibited a superior photocatalytic activity and stability for the degradation of rhodamine B (RhB) under visible light irradiation.     

An improved biosensor for acetaldehyde determination using a bienzymatic strategy at poly(neutral red) modified carbon film electrodes

Improved biosensors for acetaldehyde determination have been developed using a bienzymatic strategy, based on a mediator-modified carbon film electrode and co-immobilisation of NADH oxidase and aldehyde dehydrogenase. Modification of the carbon film electrode with poly(neutral red) mediator resulted in a sensitive, low-cost and reliable NADH detector. Immobilisation of the enzymes was performed using encapsulation in a sol-gel matrix or cross-linking with glutaraldehyde. The bienzymatic biosensors were characterized by studying the influence of pH, applied potential and co-factors. The sol-gel and glutaraldehyde biosensors showed a linear response up to 60 μM and 100 μM, respectively, with detection limits of 2.6 μM and 3.3 μM and sensitivities were 1.7 μA mM⁻¹ and 5.6 μA mM⁻¹. The optimised biosensors showed good stability and good selectivity and have been tested for application for the determination of acetaldehyde in natural samples such as wine.     

无液接裸露式Ag/AgCl参比电极的研制及应用

提出了一种无液接裸露式Ag/AgC l参比电极制备方法,测试了该参比电极的稳定性、重现性、可逆性、响应时间、温度影响等因素。实验结果表明,该电极电位稳定在49 mV,响应时间在30 s以内时,具有重现性、可逆性好,使用寿命长,温度影响小等特点,可替代饱和甘汞和Ag/AgC l参比电极。     

Sonochemical synthesis of Ag/AgCl nanocubes and their efficient visible-light-driven photocatalytic performance

A novel one-step sonochemical approach to synthesize a plasmonic photocatalyst of AgCl nanocubes (ca. 115 nm in edge length) with a small amount of Ag metal species is presented. The nanoscale Ag/AgCl hybrid photocatalysts with cubic morphology are readily formed under ambient ultrasonic conditions and neither external heat treatment nor reducing agents are required. The size of the Ag/AgCl photocatalysts could be controlled by changing the concentrations of Ag(+) ions and polyvinylpyrrolidone molecules in precursor solutions. The compositions, microstructures, influencing factors, and possible growth mechanism of the Ag/AgCl hybrid nanocubes were systematically investigated. The Ag/AgCl photocatalysts show excellent photocatalytic performance for degradation of various dye molecules under visible light.     

Potential(V vs Ag/AgCl,pH=7)

含有机物工业废水的处理仍然是人类实现可持续发展的重大挑战.而光催化作为一种先进的氧化环保技术,以其反应条件温和、能耗相对较低的优点在有机废水处理中受到越来越多的关注.近年来,人们设计和合成了许多不同结构和形状的光催化剂.特别是金属氧化物半导体以其适宜的能带结构、稳定的物化性质、无毒性等特点已成为光催化降解有机废水的研究热点.此外,一维纳米结构(1D)已被证实有利于光催化降解过程,其优势在于比表面积大,离子的迁移路径短,以及独特的一维电子转移轨道.尤其是TiO2纳米纤维由于其亲水性、特殊的形貌和合适的能带位置,在污染物水溶液的处理中表现出优异的光催化性能.然而, TiO2(～3.2 eV)的宽禁带、光生载流子的易复合等缺陷导致其光利用率较低,限制了其实际应用.因此,人们提出了许多提高光催化活性的策略,如掺杂金属或非金属元素、负载贵金属、构建异质结等.构建梯形(S型)异质结已被证实是提高复合材料光催化活性的一种有前途的策略.S型异质结不仅能有效地分离光生电子和空穴,而且还原能力低的半导体CB上的电子和氧化能力低的半导体VB上的空穴复合,而氧化还原能力较强的空穴和电子分别被保留.因此,这一电子转移过程赋予了复合物最大的氧化还原能力.同时,在g-C3N4中引入硫元素可以拓宽其光吸收范围,从而产生更多的光生载流子.此外,额外的表面杂质将有助于e--h+对的分离,其光催化活性明显高于单纯的g-C3N4.综合一维纳米结构、硫掺杂和S型异质结的优势,本文采用静电纺丝和煅烧法制备了一系列硫掺杂的g-C3N4(SCN)/TiO2S型光催化剂.制备的SCN/TiO2复合材料在光催化降解刚果红(CR)水溶液中表现出比纯TiO2和SCN更优越的光催化性能.光催化活性的显著增强是由于一维分布的纳米结构和S型异质结.此外, XPS分析和DFT计算表明,电子从SCN通过SCN/TiO2复合材料的界面转移到TiO2.在模拟太阳光照射下,界面内建电场、带边缘弯曲和库仑相互作用协同促进了复合物相对无用的电子和空穴的复合.因此,剩余的电子和空穴具有较高的还原性和氧化性,使复合材料具有最高的氧化还原能力.这些结果通过自由基捕获实验、ESR实验和XPS原位分析得到了充分的验证,说明光催化剂中的电子迁移遵循S型异质结机理.本文不仅可以丰富了新型S型异质结光催化剂的设计和制备方面的知识,并为未来解决环境污染问题提供一个有前景的策略.     

Biological production of acetaldehyde from ethanol using non-growingPichia pastoris whole cells

Acetaldehyde has been produced biologically using whole-cellPichia pastoris in a semibatch fermentor. Ethanol and air were fed continuously, and the product, acetaldehyde, was removed by the air stream. Operation of the reactor exceeded 100 h, maintaining high alcohol oxidase activity. Low cell-mass concentration (9.9 g/L) minimized product inhibition. Ethanol concentration in the broth, oxygen concentration in the air, and pH were evaluated for their effects on the fermentation process.     

Bucky-gel coated glassy carbon electrodes, for voltammetric detection of femtomolar leveled lead ions

Femtomolar (fM) leveled lead ions were electrochemically detected using a bucky-gel coated glassy carbon electrode and differential pulse anodic stripping voltammetry. The bucky-gel was composed of dithizone, ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate), and multi-walled carbon nanotubes (MWCNTs). The fabrication of the bucky-gel coated electrode was optimized. The modified electrode was characterized with voltammetry, electrochemical impedance spectroscopy, and chronoamperometry. After the accumulation of lead ions into the bucky-gel modified electrode at −1.2 V vs. saturated calomel electrode (SCE) for 5 min in a pH 4.4 sodium acetate-acetate acid buffer solution, differential pulse anodic stripping voltammograms of the accumulated lead show an anodic wave at −0.58 V. The anodic peak current is detectable for lead ions in the concentration range from 1.0 μM down to 500 fM. The detection limit is calculated to be 100 fM. The proposed method was successfully applied for the detection of lead ions in lake water.     

Control of Interfacial Potentials and Redox Reactions on Bipolar Electrodes Using Ag/AgCl

The interfacial potential difference on the surface of bipolar electrodes was controlled by placing Ag/AgCl on part of the electrode. Oxygen reduction on the cathodic pole was coupled with an electrochemiluminescence (ECL) reaction on the anodic pole. In an open bipolar system, the ECL intensity depended on the location of Ag/AgCl and the concentration of Cl⁻ ions. A current flowed through Ag/AgCl and the ratio of currents generated at the anodic and cathodic poles was affected by the position of Ag/AgCl. Further, the effect of Ag/AgCl placement was also demonstrated in a closed bipolar system using hydrogen peroxide (H₂O₂) and glucose as analytes. Ag/AgCl was also effective in adjusting the sensitivity to these analytes to achieve the best performance. This method of interfacial potential control is expected to contribute toward the development of reliable sensing devices and applications such as redox cycling, which require precise potential control.     

The fabrication and performance of an Ag/AgCl reference electrode in human serum

A simple set of electric circuits was used to assemble a pulse generator. With pulse potentials and under galvanostatical control, a clean silver wire was anodized electrochemically for 0.2–0.5 min in 1.0 mol l⁻¹ HCl with a pulse current density of 20 mA cm⁻², and the pulse wave parameters of t_a/t_c = 1 and a cycle of 4 s forming an Ag/AgCl reference electrode. Even though the AgCl layer was consumed during the working period when the Ag/AgCl electrode was used as a cathode, the AgCl layer could be in situ recovered electrochemically in serum used when a reversed potential was applied to the electrode system immediately after the measuring program was finished. The current response curve of the anode indicated that an AgCl layer in high density was basically accomplished during the first 6 pulse cycles in human serum. In order to keep a stable and uniform AgCl layer on the reference electrode after each measuring cycle, the ratio of the recovery time (t_r) to the working time (t_w) was measured and the smallest value was obtained at 0.03. The open-circuit potential of the Ag/AgCl electrode with respect to a SCE in 0.1 mol l⁻¹ KCl was monitored over a period of 14 days and the mean value was 40.09 mV vs SCE with a standard deviation of 2.55 mV. The potential of the Ag/AgCl reference electrode did remain constant when the measurements were repeated more than 600 times in undiluted human serum with a standard deviation of 1.89 mV. This study indicated that the Ag/AgCl reference electrode could been rapidly fabricated with a pulse potential and could be used as a reference electrode with long-term stable properties in human serum samples.