Platinized carbon nanoelectrodes as potentiometric and amperometric SECM probes

Micrometer-sized platinized carbon electrodes have previously been used for the detection of reactive oxygen and nitrogen species (ROS and RNS) in biological systems. Here, we report the preparation and characterization of quartz-sealed platinized carbon nanoelectrodes. Such electrodes can be employed as tips in the scanning electrochemical microscope (SECM). The prepared electrodes were characterized by steady-state voltammetry, scanning electron microscopy, and SECM. In addition to ROS/RNS detection, the high surface area of a platinized nanoelectrode makes it a useful potentiometric probe. Unlike previously fabricated platinized electrodes, carbon electrodes possess a very thin insulating sheath, which is essential for experiments inside biological cells and high-resolution SECM imaging.     

纳米尺度扫描电化学显微镜的探针制备及在电催化氧和氢反应研究中的应用

扫描电化学显微镜是一种在检测样品表面物理形貌的同时能提供丰富的电化学信息的扫描探针技术,由于超微电极的引入,它可以高时空分辨率地探究各类样品的物理形貌和电化学性能之间的构效关系. 随着现代纳米科技的不断发展,扫描探针的尺寸也逐渐从亚微米发展到纳米级别. 与此同时,高效优选各类氧反应和氢反应电催化材料,明晰其电化学反应过程和性能是二十一世纪绿色新能源转换存储系统（如可再生燃料电池、金属空气电池等）的重要研究方向. 本文首先概括了可应用于扫描电化学显微镜的纳米级扫描探针的制备及发展,之后着重介绍了近四年纳米尺度扫描电化学显微镜在电催化氧反应和氢反应研究中的一些最新研究进展. 最后以点窥面,对未来纳米尺度扫描电化学显微镜的未来发展趋势作了展望.     

扫描电化学显微镜在电催化氧反应研究中的应用

本综述首先简单介绍了扫描电化学显微镜的基本概况,尤其是不同的工作模式. 其次,有针对性地介绍了SECM的不同工作模式在氧还原和水解析氧反应相关研究中的应用. 最后,对扫描电化学显微镜未来在新能源转换存储系统研究领域的应用进行了展望.     

Modification and characterization of artificially patterned enzymatically active surfaces by scanning electrochemical microscopy

This review summarizes the characterization of localized enzymatic activity by scanning electrochemical microscopy (SECM). After introducing the concepts of feedback imaging and generator-collector experiments with enzyme-modified solid surfaces, a comparison of the merits and limitations of both approaches is given and further illustrated by selected applications. They include enzyme-modified patterned monolayers, enzyme-modified polymer microstructures and enzyme-modified metal microstructures. Such configurations are important for the development of miniaturized bioanalytical systems with proteins, such as miniaturized enzyme electrode arrays. SECM has emerged as an ideal tool for prototyping of such systems. It also offers several mechanisms for local surface modifications under conditions compatible with conservation of protein functionality of enzymes and antibodies. The subsequent imaging of the immobilized activity provides direct information about local immobilized enzyme activity. The range of biotechnological applications can be expanded by labeling other biomolecules, such as monoclonal antibodies, with appropriate enzymes. Miniaturized electrochemical enzyme immunoassays that apply the sandwich format and SECM as the detection method are reviewed. They have been performed on microstructured supports after reagent spotting or on agglomerates of surface-modified magnetic microbeads. Finally, current challenges are listed with indications of ongoing research to overcome current limitations by means of instrumental improvements.     

SECM基本原理及其在金属腐蚀中的应用

扫描电化学显微镜（SECM）是一种具有较高空间分辨率的化学显微镜,在成像和动力学研究已经广泛应用. 本文简要介绍SECM基本原理,综述2009年以来SECM在腐蚀方面的应用,包括扫描成像和异相转移电子化学活性的研究,并简要介绍了作者课题组在SECM方面的研究工作,展望SECM在腐蚀研究的应用.     

Modification and characterization of artificially patterned enzymatically active surfaces by scanning electrochemical microscopy

This review summarizes the characterization of localized enzymatic activity by scanning electrochemical microscopy (SECM). After introducing the concepts of feedback imaging and generator-collector experiments with enzyme-modified solid surfaces, a comparison of the merits and limitations of both approaches is given and further illustrated by selected applications. They include enzyme-modified patterned monolayers, enzyme-modified polymer microstructures and enzyme-modified metal microstructures. Such configurations are important for the development of miniaturized bioanalytical systems with proteins, such as miniaturized enzyme electrode arrays. SECM has emerged as an ideal tool for prototyping of such systems. It also offers several mechanisms for local surface modifications under conditions compatible with conservation of protein functionality of enzymes and antibodies. The subsequent imaging of the immobilized activity provides direct information about local immobilized enzyme activity. The range of biotechnological applications can be expanded by labeling other biomolecules, such as monoclonal antibodies, with appropriate enzymes. Miniaturized electrochemical enzyme immunoassays that apply the sandwich format and SECM as the detection method are reviewed. They have been performed on microstructured supports after reagent spotting or on agglomerates of surface-modified magnetic microbeads. Finally, current challenges are listed with indications of ongoing research to overcome current limitations by means of instrumental improvements. Received: 19 December 2000 / Revised: 26 February 2001 / Accepted: 2 March 2001     

Scanning electrochemical microscopy-development of instrumentation utilizing piezo-bimorph X-Y scanners

The development of the instrumentation of a scanning electrochemical microscopy (SECM) is presented. The core of the SECM sensing system is constructed based on piezobimorph scanners, a mechanical micropositioner of multi-dimensional adjustment and ultramicroelectrodes. The control of the electrochemical cell and the SECM system is realized by a battery powered bipoteniostat and analog control circuits respectively with the control of a microcomputer work station. The demonstrations of SECM experiments are given on both a standard IDA sample and a silver electrode. Discussions on the resolution and quality of SECM image are made.     

Fabricating and imaging carbon-fiber immobilized enzyme ultramicroelectrodes with scanning electrochemical microscopy.

The scanning electrochemical microscope (SECM) is used to image the activity of enzymes immobilized on the surfaces of disk-shaped carbon-fiber electrodes. SECM was used to map the concentration of enzymatically produced hydroquinone or hydrogen peroxide at the surface of a 33-microm diameter disk-shaped carbon-fiber electrode modified by an immobilized glucose-oxidase layer. Sub-monolayer coverage of the enzyme at the electrode surface could be detected with micrometer resolution. The SECM was also employed as a surface modification tool to produce microscopic regions of enzyme activity by using a variety of methods. One method is a gold-masking process in which microscopic gold patterns act as mask for producing patterns of chemical modification. The gold masks allow operation in both a positive or negative process for patterning enzyme activity. A second method uses the direct mode of the SECM to produce covalently attached amine groups on the carbon surface. The amine groups are anchors for attachment of glucose oxidase by use of a biotin/avidin process. The effect of non-uniform enzyme activity was investigated by using the SECM tip to temporarily damage an immobilized enzyme surface. SECM imaging can observe the spatial extent and time-course of the enzyme recovery process.     

Filming a live cell by scanning electrochemical microscopy: label-free imaging of the dynamic morphology in real time

ABSTRACT: The morphology of a live cell reflects the organization of the cytoskeleton and the healthy status of the cell. We established a label-free platform for monitoring the changing morphology of live cells in real time based on scanning electrochemical microscopy (SECM). The dynamic morphology of a live human bladder cancer cell (T24) was revealed by time-lapse SECM with dissolved oxygen in the medium solution as the redox mediator. Detailed local movements of cell membrane were presented by time-lapse cross section lines extracted from time-lapse SECM. Vivid dynamic morphology is presented by a movie made of time-lapse SECM images. The morphological change of the T24 cell by non-physiological temperature is in consistence with the morphological feature of early apoptosis. To obtain dynamic cellular morphology with other methods is difficult. The non-invasive nature of SECM combined with high resolution realized filming the movements of live cells.     

Scanning electrochemical microscopy in the 21st century

The fundamentals of and recent advances in scanning electrochemical microscopy (SECM) are described. The focus is on applications of this method to studies of systems and processes of active current interest ranging from nanoelectrochemistry to electron transfer reactions and electrocatalysis to biological imaging.     

Direct Nanomachining on Semiconductor Wafer By Scanning Electrochemical Microscopy

Scanning electrochemical microscopy (SECM) is one of the most important instrumental methods of modern electrochemistry due to its high spatial and temporal resolution. We introduced SECM into nanomachining by feeding the electrochemical modulations of the tip electrode back to the positioning system, and we demonstrated that SECM is a versatile nanomachining technique on semiconductor wafers using electrochemically induced chemical etching. The removal profile was correlated to the applied tip current when the tip was held stationary and when it was moving slowly (<20 μm s⁻¹), and it followed Faraday's law. Both regular and irregular nanopatterns were translated into a spatially distributed current by the homemade digitally controlled SECM instrument. The desired nanopatterns were “sculpted” directly on a semiconductor wafer by SECM direct-writing mode. The machining accuracy was controlled to the sub-micrometer and even nanometer scales. This advance is expected to play an important role in electrochemical nanomachining for 3D micro/nanostructures in the semiconductor industry.     

Tip current/positioning close-loop mode of scanning electrochemical microscopy for electrochemical micromachining

Scanning electrochemical microscopy (SECM) has been approved as a prospective electrochemical micromachining (ECMM) technique soon after its birth. However, it still remains challenge for SECM to fabricate arbitrary three-dimensional (3D) microstructures because of the limitation of positioning system. To solve this problem, we proposed a tip current signal/positioning close-loop mode in which the tip current signal is fed back to the positioning system in order to program the motion trial of SECM tip. Both the triedge-cone and sinusoidal microstructures were obtained by the close-loop positioning mode. The static-state etching process was demonstrated not to be disturbed by the slow motion rate of SECM tip. The unique positioning mode would be significant for both ECMM and electrochemical imaging.     

Biological applications of scanning electrochemical microscopy: chemical imaging of single living cells and beyond

Recent applications of scanning electrochemical microscopy (SECM) to studies of single biological cells are reviewed. This scanning probe microscopic technique allows the imaging of an individual cell on the basis of not only its surface topography but also such cellular activities as photosynthesis, respiration, electron transfer, single vesicular exocytosis and membrane transport. The operational principles of SECM are also introduced in the context of these biological applications. Recent progress in techniques for high-resolution SECM imaging are also reviewed. Future directions, such as single-channel detection by SECM, high-resolution imaging with nanometer-sized probes, and combined SECM techniques for multidimensional imaging are also discussed.     

扫描电化学显微镜及其在界面电化学研究中的应用

对扫描电化学显微镜(Scanning Electrochemical Microscope，SECM)的发展及其在界面电化学中的研究应用进行了评述。介绍了SECM的工作原理以及常用的操作模式，并对SECM在液／液界面、固／液界面等方面的应用进行了总结。     

Electrochemical detection of receptor-mediated endocytosis by scanning electrochemical microscopy

We report a scanning electrochemical microscopy (SECM)-based receptor-mediated endocytosis detection method. Epidermal growth factor receptor (EGFR), which is one of the key membrane proteins associated with cancer, was used as a model for receptor-mediated endocytosis. EGFR molecules on the outer cell membrane were detected by SECM by using alkaline phosphatase (ALP) as a labeling enzyme. Since SECM detected the ALP activity on the outer membrane, the procedure helped discriminate the EGFR on the outer membrane from the intracellular EGFR involved in endocytosis. SECM showed a marked decrease in the current responses generated due to ALP activity by 93% on addition of the epidermal growth factor, indicating clearly that EGF triggered the endocytosis, which led to the withdrawal of most EGFRs from the outer membrane.     

Constant-distance mode scanning electrochemical microscopy (SECM)--Part I: Adaptation of a non-optical shear-force-based positioning mode for SECM tips

A non-optical shear-force-based detection scheme for accurately controlling the tip-to-sample distance in scanning electrochemical microscopy (SECM) is presented. With this approach, the detection of the shear force is accomplished by mechanically attaching a set of two piezoelectric plates to the scanning probe. One of the plates is used to excite the SECM tip causing it to resonate, and the other acts as a piezoelectric detector of the amplitude of the tip oscillation. Increasing shear forces in close proximity to the sample surface lead to a damping of the vibration amplitude and a phase shift, effects that are registered by connecting the detecting piezoelectric plate to a dual-phase analogue lock-in amplifier. The shear force and hence distance-dependent signal of the lock-in amplifier is used to establish an efficient, computer-controlled closed feedback loop enabling SECM imaging in a constant-distance mode of operation. The details of the SECM setup with an integrated piezoelectric shear-force distance control are described, and approach curves are shown. The performance of the constant-distance mode SECM with a non-optical detection of shear forces is illustrated by imaging simultaneously the topography and conductivity of an array of Pt-band microelectrodes.     

Scanning electrochemical microscopy in the 21st century. Update 1: Five years after

This Perspective is an update to our more extensive survey of scanning electrochemical microscopy (SECM) published in 2007. During this time, the SECM field retained its momentum by expanding into new areas and meeting the emerging scientific and technological challenges. Here we focus on most prominent developments such as high-resolution imaging, investigation of structures and processes on the nanoscale, alternative energy applications, and new approaches to solving "real world" problems. The fabrication of novel SECM probes and related theoretical advances are also discussed.     

Scanning electrochemical microscopy for biosurface imaging

Scanning electrochemical microscopy (SECM) is a powerful technique that can provide chemical identity, quantification, and spatiotemporal information on biosurfaces. The ability of SECM for noninvasive and high-resolution electrochemical imaging has made it valuable for the study of cell phenotypes and functions. This review focuses on the latest advances of SECM technique for the biosurface imaging. The SECM measurements of different biomarkers, including oxygen consumption rate and enzyme activity of cell aggregates, redox state of cardiomyocytes, and bacterial metabolic activity, are introduced. The applicability of SECM on membrane permeability measurements, neurotransmitter measurements, and intracellular measurements is discussed.     

扫描电化学显微镜在生物医学领域的应用研究进展

研究病变细胞和组织的异常表现可为理解重大疾病发生发展的病理机理和新型药物筛选提供重要参考.扫描电化学显微镜(Scanning electrochemical microscopy, SECM)是一种基于电化学原理的扫描探针显微镜,通过记录探针在样品表面扫描时的电流或电位等信息,对活细胞的形态和多种化学信息进行原位、实时...     

Optimized preparation and scanning electrochemical microscopy analysis in feedback mode of glucose oxidase layers grafted onto conducting carbon surfaces

An optimized immobilization procedure based on the electroreduction of aryldiazonium salt followed by covalent attachment of a cross-linked hydrogel was used to graft glucose oxidase on a carbon surface. Scanning electrochemical microscopy (SECM) and cyclic voltammetry were used to follow the construction steps of the modified electrode. By adjusting the compactness of the layer through the electrografting reaction, the penetration of the mediator through the layer can be controlled to allow the monitoring of the enzymatic activity by both cyclic voltammetry and SECM in feedback mode. The enzymatic activity of the film is finally characterized by SECM.