微波原位合成Ag NPs/MoS2复合材料及其电化学性能

二硫化钼纳米片(MoS₂)受到带电杂质、结构缺陷和易聚集等因素的影响,导致其电子转移性能下降,使其应用受限。将银纳米颗粒(Ag NPs)与少层MoS₂纳米片复合,可提升MoS₂纳米片的电化学性能。本研究创新性地采用微波还原法,使Ag NPs原位沉积于MoS₂,得到Ag NPs/MoS₂复合材料。结果表明,将Ag NPs/MoS₂复合材料修饰于丝网印刷电极(screen printed electrodes,SPE)后,测得的循环伏安(cyclic voltammetry,CV)曲线峰电流值为同浓度单一MoS₂修饰电极的1.8倍,方波伏安(square wave voltammetry,SWV)曲线峰电流值为单一MoS₂修饰电极的3.4倍,电化学阻抗谱(electrochemical impedance spectroscopy,EIS)的电子转移阻抗值(Ret)仅为167Ω,相比MoS₂/S...     

2,4,5-三氯苯酚在复合修饰电极的电化学行为的研究

制备了多壁碳纳米管/纳米金复合修饰电极(MWCNT/Au NPs/GCE),研究了2,4,5-三氯苯酚(2,4,5-trichlorophenol,简称2,4,5-TCP)在此修饰电极上的电化学行为。结果表明2,4,5-三氯苯酚在MWCNT/Au NPs/GCE上于0.640V有一灵敏氧化峰,与裸电极相比峰电流显著提高。考查了支持电解液、修饰剂用量等测量条件的影响,发现在7.0×10~(-7)~6.0×10~(-6)mol·L~(-1),3.5×10~(-6)~3.5×10~(-4)mol·L~(-1)两个浓度区间内,2,4,5-TCP峰电流和浓度呈良好线性关系。在扫速0.05~0.2 V·s~(-1)时,氧化峰电流与扫速成线性关系,这说明2,4,5-TCP在修饰电极上的电化学氧化过程是受吸附控制的。采用计时电量法获得扩散系数(D)为3.08×10~(-6)cm~2·s~(-1);根据Frumkin等温式,计算出2,4,5-TCP的吸附系数β为1.3×10~3L·mol~(-1)。另外,我们推导出2,4,5-TCP在MWCNT/Au NPs/GCE修饰电极上的电极反应是一电子、一质子的完全不可逆过程。     

氧化石墨烯/多壁碳纳米管负载金铂核壳纳米粒子构建一种三维新型抗坏血酸电化学传感器

该文采用涂覆的方式构建了一种用于灵敏检测抗坏血酸(AA)的电化学传感器。先将多壁碳纳米管(MWCNTs)和氧化石墨烯(GO)混合悬浮液修饰在玻碳电极(GCE)表面,修饰的GO可有效防止MWCNTs聚集,再将具有良好电催化性能的金铂核壳纳米粒子(Au@Pt NPs)修饰在GO/MWCNTs电极上,层层组装构建形成GO/MWCNTs/Au@Pt NPs/GCE三维新型抗坏血酸电化学传感器。该修饰电极在磷酸缓冲溶液中对AA显示了较宽的线性范围和极低的检出限,氧化峰电流与AA浓度在0.005～0.5μmol/L和0.5～1 000μmol/L范围内呈良好的线性关系,相关系数均为0.999,检出限(S/N=3)为4×10~(-9) mol/L,稀释人体血清样品的加标浓度为0.01、0.1、10μmol/L,回收率为90.9%～108%,相对标准偏差(RSD,n=3)为1.2%～2.8%。该修饰电极对AA具有良好的选择性,可有效排除多巴胺、尿酸、葡萄糖等生物小分子的干扰。方法简单、高效、灵敏,可用于临床实际检测。     

基于Ru@SiO_2的微囊藻毒素电化学发光免疫传感器研究

本研究在玻碳电极(GCE)表面电沉积金纳米粒子(Au NPs),通过化学吸附将微囊藻毒素-(亮氨酸-精氨酸)(MC-LR)的单克隆抗体(anti-MC-LR)固定在电沉积了Au NPs的玻碳电极表面,以牛血清白蛋白(BSA)封闭非特异性吸附位点,制得免疫电极anti-MC-LR/Au NPs/GCE。采用微乳化法制备了掺杂三(2,2'-联二吡啶)钌(Ⅱ)配合物离子(Ru(bpy)2+3)的二氧化硅纳米粒子(Ru@SiO2),利用透射电镜和扫描电镜对所制备的纳米粒子进行表征。3-氨基丙基三乙氧基硅烷(APTS)进一步与Ru@SiO2反应,制得氨基功能化的Ru@SiO2,通过1-(3-二甲氨基丙基)-3-乙基碳二亚胺(EDC)和N-羟基琥珀酰亚胺(NHS)活化辣根过氧化物酶标记的MC-LR(HRP-MC-LR),并使其与氨基功能化的Ru@SiO2偶联,制得MC-LR-Ru@SiO2。采用直接竞争模式,在标记物MC-LR-Ru@SiO2存在下,以三丙胺作为共反应物,利用电化学发光法(ECL)测定溶液中的微囊藻毒素,免疫反应完成后,电化学发光强度(I)随着MC-LR浓度的增大而减小,且在0.100~100μg/L范围内,电化学发光强度差值(ΔI)与游离的MC-LR浓度的对数呈良好线性关系,检出限为0.007μg/L。对实际水样进行了加标回收实验,回收率为95.5%~105%。     

基于PbS QDs/TiO2 NPs构建新型谷胱甘肽光电化学传感器

通过高温煅烧将二氧化钛纳米颗粒(TiO₂ NPs)修饰到ITO电极表面制成TiO₂ NPs/ITO电极, 再采用连续离子层吸附反应(SILAR)循环将硫化铅量子点(PbS QDs)修饰到TiO₂/ITO电极表面制得PbS QDs/TiO₂ NPs/ITO电极, 并将该电极应用于检测谷胱甘肽(GSH)的光电化学传感器. 在该传感器中, 当PbS QDs受470 nm可见光的激发时将产生电子(e)和光生空穴(h ⁺), 光生空穴可被溶液中的GSH捕获, 并将GSH氧化成GSSH, 有效避免电子和空穴的复合, 显著提高了光电效率. 该传感器对GSH的检测具有较高的灵敏度和选择性, 线性检测范围为0.06~1 mmol/L, 检出限(LOD)为4.6×10 ^-3 mmol/L(S/N=3).     

八面体二氧化铈负载金纳米粒子的电化学传感器检测邻氨基苯酚

采用原位生长法制备了八面体二氧化铈(Ce O₂)负载金纳米粒子(Au NPs)复合材料Au NPs@Ce O₂,用扫描电镜及能量色散X射线光谱仪对复合材料进行形貌表征与元素分析。利用此复合材料修饰玻碳电极,构筑了一种邻氨基苯酚电化学传感器。Ce O₂性质稳定,其八面体结构提供了较大的比表面积,Au NPs具备极佳的导电性,二者复合协同发挥良好的电催化能力。研究发现,Au NPs@Ce O₂复合材料修饰电极对邻氨基苯酚表现出较高的检测灵敏度,在优化实验条件下,邻氨基苯酚浓度与氧化峰电流成正比,在1.00×10^-7～3.38×10^-5 mol/L浓度范围内呈现2段较好的线性关系,线性回归方程分别为I₁(A)=3.29×10^-2c(mol/L)+1.08×10^-8 (R=0.9967)和I₂(A)=1.32×10^-2c(mol/L)+1.22×10     

四磺酸酞菁钴-DDAB表面活性剂薄膜电极的电化学与电化学催化研究

四磺酸酞菁钴配合物阴离子(CoPcTS_4-)在水溶液中可借助离子交换进入阳离子表面活性剂双十二烷基二甲基溴化铵(DDAB)薄膜,从而形成CoPcTS_4-DDAB薄膜电极.循环伏安法表明,该薄膜电极在pH7.0的空白缓冲溶液中十分稳定,有两对准可逆的还原氧化峰,其中第一对峰的E_pc1=-0.28V,E_pa1=-0.18V(vs.SCE),为中心离子Co(II)Co(I)的还原氧化峰;第二对峰的E_pc2=-1.30V,E_pa2=-1.18V,为酞菁环的还原氧化峰.应用循环伏安法估计了该薄膜体系的电荷传递扩散系数D_ct和表观非均相电极反应速率常数k^o'.CoPcTS_4-DDAB薄膜电极可用于对三氯乙酸(TCA)的电化学催化还原.催化电流与TCA浓度在4×10^-5～1×10^-3molL范围内成线性关系.     

青蒿素在银电极上的电化学行为及其定量分析

在乙醇(1+4)+B R缓冲溶液(pH7.2)中,青蒿素在银电极上有一灵敏的还原峰,无氧化峰,峰电位为-0.64V(vs.SCE)。2 5次微分线性扫描伏安(2 5thLSV)峰电流与青蒿素的浓度在8.0×10-6～1.0×10-3mol L范围内成线性关系(r=0.9994),检出限为5.0×10-6mol L,该法已用于人工合成样品分析,优于紫外测定法。     

基于固体酶催化反应电化学测定酶含量

提出了以固体辣根过氧化物酶(HRP)对过氧化氢氧化邻苯二胺的催化作用为基础的测定HRP及其标记物的电化学方法.测定中以Au-Pt/PAN/GCE为工作电极,并详细叙述其制备过程.将一定浓度的HRP按规定方法固定在上述修饰电极上制得HRP/Au-Pt/PAN/GCE修饰电极,将此电极浸入含5.0×10-3mol·L-1邻苯二胺及2.5×10-3mol·L-1过氧化氢的磷酸盐缓冲溶液(pH 5.0)中,反应10 min后将电极取出,记录溶液中酶催化反应产物的方波伏安峰及峰电流.结果表明:酶催化反应前,底物在工作电极上于-0.488 V(vs.SCE)处有明显的还原峰,在酶催化反应后,在-0.584 V处出现一个更大的还原峰,电位负移160 mV,且峰电流明显增大.峰电流值(Ip)与修饰在Au-Pt/PAN/GCE电极上的HRP的含量在1.0×10-2～2.0×102μg·L-1之间呈线性关系,方法的检出限(3S/N)为3.0 ng·L-1.     

洛美沙星的示波极谱法测定及其电化学行为

在Britton-Robinson－0.02mol/LKCl(pH8.77)底液中,洛美沙星在汞电极上有一灵敏的导数还原峰,峰电位V     

Analysis of diffusion-controlled stochastic events of iridium oxide single nanoparticle collisions by scanning electrochemical microscopy

We investigated the electrochemical detection of single iridium oxide nanoparticle (IrO(x) NP) collisions at the NaBH(4)-treated Pt ultramicroelectrode (UME) in a scanning electrochemical microscope (SECM) over an insulating surface. The NP collision events were monitored by observing the electrocatalytic water oxidation reaction at potentials where it does not take place on the Pt UME. These collisions occurred stochastically, resulting in a transient response ("blip") for each collision. The frequency of the collisions is proportional to the flux of NPs to the UME tip, and thus equivalent to the SECM current. A plot of collision frequency versus distance followed the theoretical approach curve behavior for negative feedback for a high concentration of mediator, demonstrating that the collisions were diffusion-controlled and that single-particle measurements of mass transport are equivalent to ensemble ones. When the SECM was operated with a Pt substrate at the same potential as the tip, the behavior followed that expected of the shielding mode. These studies and additional ones result in a model where the IrO(x) NP collision on the Pt UME is adsorptive, with oxygen produced by the catalyzed water oxidation causing a current decay. This results in a blip current response, with the current decay diminished in the presence of the oxygen scavenger, sulfite ion. Random walk and theoretical bulk simulations agreed with the proposed mechanism of IrO(x) NP collision, adsorption, and subsequent deactivation.     

结合光学成像技术研究单颗粒碰撞电化学

近年来,单颗粒碰撞技术在纳米电化学领域受到广泛关注. 该技术通常控制超微电极处于某一电位,检测单个纳米颗粒随机碰撞到电极表面后产生的瞬时电流. 通过分析电流信号,可以研究单个纳米颗粒的性质. 尽管该技术可以检测单个纳米颗粒的电化学或电催化电流,但是传统的单颗粒碰撞技术缺乏空间分辨率,难以识别和表征特定的纳米颗粒. 因此,结合光学成像技术研究单颗粒碰撞电化学来补充电化学技术缺失的空间信息已成为一种趋势. 本文首先简要综述了单颗粒碰撞技术的三种检测原理,主要介绍了近年来单颗粒碰撞技术与荧光显微镜、表面等离激元共振显微镜、全息显微镜和电致化学发光相结合的研究进展,最后展望了单颗粒碰撞技术未来的发展趋势.     

Combined Blip and Staircase Response of Ascorbic Acid‐Stabilized Copper Single Nanoparticle Collision by Electrocatalytic Glucose Oxidation

The current response of the collision of ascorbic acid‐stabilized copper (Cu) single nanoparticles (NPs) on a gold (Au) ultramicroelectrode (UME) surface was observed by using an electrocatalytic amplification method. Here, the glucose oxidation electrocatalyzed by oxidized Cu NPs was used as the indicating reaction. In this system, the NP collision signals were obtained simultaneously by both direct particle electrolysis and electrocatalytic amplification. For example, when the applied potential was high enough for Cu NP oxidation, a blip response combined with a staircase response was observed as a current signal. The blip part in the single Cu NP collision signal indicates the self‐oxidation of a Cu NP, and the staircase part indicates the steady‐state electrocatalytic reaction by oxidized Cu NP.     

DNA analysis by application of Pt nanoparticle electrochemical amplification with single label response

This study demonstrates a highly sensitive sensing scheme for the detection of low concentrations of DNA, in principle down to the single biomolecule level. The previously developed technique of electrochemical current amplification for detection of single nanoparticle (NP) collisions at an ultramicroelectrode (UME) has been employed to determine DNA. The Pt NP/Au UME/hydrazine oxidation reaction was employed, and individual NP collision events were monitored. The Pt NP was modified with a 20-base oligonucleotide with a C6 spacer thiol (detection probe), and the Au UME was modified with a 16-base oligonucleotide with a C6 spacer thiol (capture probe). The presence of a target oligonucleotide (31 base) that hybridized with both capture and detection probes brought a Pt NP on the electrode surface, where the resulting electrochemical oxidation of hydrazine resulted in a current response.     

Direct Observation of the Collision of Single Pt Nanoparticles onto Single‐Crystalline Gold Nanowire Electrodes

We observed the collision of single Pt nanoparticles (NPs) onto an Au nanowire (NW) electrode by using electrocatalytic amplification. Previously, such observations had typically been performed by using a microscale disk‐type ultramicroelectrode (UME). The use of a NW electrode decreased the background noise current and provided a shielding effect, owing to adsorption of the NPs onto the insulating sheath. Therefore, the transient current signal that was caused by the collision of single NPs could be more clearly distinguished from the background current by using a NW electrode instead of a UME. Furthermore, the use of a NW electrode increased the collisional frequency and the magnitude of the transient current signal. The experimental data were analyzed by using a theoretical model and a random walk simulation model.     

Various Current Responses of Single Silver Nanoparticle Collisions on a Gold Ultramicroelectrode Depending on the Collision Conditions

Collisions of silver nanoparticles (NPs) with a more electrocatalytic gold or platinum ultramicroelectrode (UME) surface have been observed by using an electrochemical method. Depending on the applied potential to the UME, the current response to the collision of Ag NPs on the UME resulted in various shape changes. A staircase decrease, a blip decrease, and a blip increase of the hydrazine oxidation current were obtained at an applied potential of 0.33, 0.80, and 1.3 V, respectively. Different collision behaviors of Ag NPs on the UME surface were suggested for each shape of current response. Ag NP attachment, which hindered the diffusion flux to the UME, caused a staircase decrease of the electrocatalytic current. Instantaneous blocking of the hydrazine oxidation by Ag NP collision and, following recovery of the current by means of oxidation of Ag NP, caused a blip decrease of the electrocatalytic current. The formation of a higher oxidation state of Ag on the Ag NP and its electrocatalytic hydrazine oxidation resulted in a blip increase of the electrocatalytic current. The analysis of the current response of a single NP collision experiment can be a useful tool to understand the various behaviors of NPs on the electrode surface.     

Direct Electrolysis and Detection of Single Nanosized Water Emulsion Droplets in Organic Solvent Using Stochastic Collisions

We studied the electrochemical detection of single nanosized water emulsion droplets in organic solution using the electrochemical collision technique on an ultramicroelectrode (UME). In this experiment, the detection system for water droplets does not require any kind of redox species in organic solvent. Only water molecules in the water droplets were considered. When water droplets collided with the UME surface, anodic current spikes were observed in the chronoamperometry, resulting from the electrolysis of water molecules in the water droplets. From the collision frequency and integrated current spike, concentrations and size distributions of water droplets in organic solvent can be determined.     

A Snapshot of the Properties of Single Nanoparticles at the Moment of a Collision

Direct electrochemical characterization of freely moving nanoparticles (NPs) at the individual particle level is challenging. A method is presented that can achieve this goal based on the collision between a NP and an ultramicroelectrode (UME). By applying a sinusoidal potential to the UME and monitoring the current response in the frequency domain, a sudden change in the phase angle indicates the arrival of a NP at the UME. The response induced by the collision can be isolated and used to explore the properties of the NP. This method, analogous to a high‐speed camera, can obtain a snapshot of the properties of the single NP at the moment of a collision. The proposed method was employed to investigate the properties of both the hard catalytic Pt NP and soft electroactive emulsion droplets, and many new insights were revealed thereafter. The method also has the potential to be applied in many other fields, where the interested signals appear as discrete events.     

Simultaneous Detection of Single Attoliter Droplet Collisions by Electrochemical and Electrogenerated Chemiluminescent Responses

We provide evidence of single attoliter oil droplet collisions at the surface of an ultra‐microelectrode (UME) by the observation of simultaneous electrochemical current transients (i–t curves) and electrogenerated chemiluminescent (ECL) transients in an oil/water emulsion. An emulsion system based on droplets of toluene and tri‐n‐propylamine (2:1 v/v) emulsified with an ionic liquid and suspended in an aqueous continuous phase was formed by ultrasonification. When an ECL luminophore, such as rubrene, is added to the emulsion droplet, stochastic events can be tracked by observing both the current blips from oxidation at the electrode surface and the ECL blips from the follow‐up ECL reaction, which produces light. This report provides a means of studying fundamental aspects of electrochemistry using the attoliter oil droplet and offers complementary analytical techniques for analyzing discrete collision events, size distribution of emulsion systems, and individual droplet electroactivity.     

Observation of single metal nanoparticle collisions by open circuit (mixed) potential changes at an ultramicroelectrode

Single nanoparticle (NP) collisions were successfully observed by a potentiometric measurement. The open circuit potential (OCP) of a measuring Au ultramicroelectrode (UME) changes when Pt NPs collide with the UME in a hydrazine solution. The OCP change is related to the redox processes, the concentration of particles, particle size, and electrode size. Compared with the amperometric technique, this approach has several advantages: higher sensitivity, simpler apparatus, fewer problems with NP decomposition, and contamination.