Ultramicroelectrodes , scanning electrochemical microscopy

Selzer Y and Manler D 2000 Scanning electrochemical microscopy. Theory of the feedback mode for hemispherical ultramicroelectrodes steady-state and transient behavior Anal. Chem. 72 2383... 

Topics discussed above are some basic principles and techniques in voltammetry. Voltammetry in the frequency domain where i-E response is obtained at different frequencies from a single experiment known as AC voltammetry or impedance spectroscopy is well established. The use of ultramicroelectrodes in scanning electrochemical microscopy to scan surface redox sites is becoming useful in nanoresearch. There have been extensive efforts made to modify electrodes with enzymes for biosensor development. Wherever an analyte undergoes a redox reaction, voltammetry can be used as the primary sensing technique. Microsensor design and development has recently received... 

The scanning tunneling microscope (STM) has led to several other variants (61). Particularly attractive for electrochemical studies is scanning electrochemical microscopy (SECM) (62-65). In SECM, faradaic currents at an ultramicroelectrode tip are measured while the tip is moved (by a piezoelectric controller) in close proximity to the substrate surface that is immersed in a solution containing an electroactive species (Fig. 2.17). These tip currents are a function of the conductivity and chemical nature of the substrate, as well as of the tip-substrate distance. The images thus obtained offer valuable insights into the microdistribution of the electrochemical and chemical activity, as well... 

Scanning electrochemical microscopy (SECM the same abbreviation is also used for the device, i.e., the microscope) is often compared (and sometimes confused) with scanning tunneling microscopy (STM), which was pioneered by Binning and Rohrer in the early 1980s [1]. While both techniques make use of a mobile conductive microprobe, their principles and capabilities are totally different. The most widely used SECM probes are micrometer-sized ampero-metric ultramicroelectrodes (UMEs), which were introduced by Wightman and co-workers 1980 [2]. They are suitable for quantitative electrochemical experiments, and the well-developed theory is available for data analysis. Several groups employed small and mobile electrochemical probes to make measurements within the diffusion layer [3], to examine and modify electrode surfaces [4, 5], However, the SECM technique, as we know it, only became possible after the introduction of the feedback concept [6, 7],... 

Since micro-gravimetry with the EQCM lacks specificity only the difference of cation and anion fluxes can be obtained by microgravimetry and therefore an independent measurement of specific ions is needed. Scanning electrochemical microscopy (SECM) coupled with a quartz crystal microbalance with independent potential control of the tip and substrate has been recently done by Cliffel and Bard [28]. In this experiment generation at the substrate (EQCM crystaj) working electrode and collection at the tip of an ultramicroelectrode (UNE) that was approached perpendicular to the EQCM crystal was employed with measurement of A/. Hillier and Ward [8] had previously used a scanning microelectrode to map the mass sensitivity across the surface of the QCM crystal. Reflection of longitudinal waves at the UME tip limits these experiments due to oscillations. 

Horrocks, B. R., Schmidtke, D., Heller, A. and Bard, A. J. (1993), Scanning electrochemical microscopy.24. Enzyme ultramicroelectrodes for the measurement of hydrogen-peroxide at surfaces. Anal. Chem., 65(24) 3605-3614. 

Refs. [i] Bard A], Mirkin MV (eds) (2001) Scanning electrochemical microscopy. Marcel Dekker, New York, chap 3 [ii] Bard AJ, Faulkner LR (2001) Electrochemical methods, 2ni edn. Wiley, New York, chap 5 [iii] Zoski CG (ed) (2007) Handbook of electrochemistry. Elsevier, Amsterdam, chap 6,11,12,19 [iv] Fleischmann M, Pons S, Rolison DR (eds) (1987) Ultramicroelectrodes. DataTech Systems, NC... 

E. Computer-based methods for analysis of voltammetric data Ultramicroelectrodes and Scanning Electrochemical Microscopy... 

Scanning electrochemical microscopy (SECM) [196] is a member of the growing family of scanning probe techniques. In SECM the tip serves as an ultramicroelectrode at which, for instance, a radical ion may be generated at very short distances from the counterelectrode under steady-state conditions. The use of SECM for the study of the kinetics of chemical reactions following the electron transfer at an electrode [196] involves the SECM in the so-... 

C Wei, AJ Bard, I Kapui, G Nagy, K Toth. Scanning electrochemical microscopy. 32. Gallium ultramicroelectrodes and their application in ion-selective probes. Anal Chem 68 2651-2655, 1996. 

Scanning electrochemical microscopy (SECM) is a scanning probe technique in which the probe is a disk ultramicroelectrode (typical radius in the 5 to 25 pm range) that scans the surface of the investigated sample facing it [157]. SECM measurements are carried out in... 

Satpati, A.K. and Bard, A.J. (2012) Preparation and characterization of carbon powder paste ultramicroelectrodes as tips for scanning electrochemical microscopy applications. Anal. Chem., 84, 9498 - 9504. 

Walsh DA, Lovelock KRJ, Licence P (2010) Ultramicroelectrode voltammetry and scanning electrochemical microscopy in room-temperature ionic liquid electrolytes. Chem Soc Rev 39 4185 194... 

Scanning electrochemical microscopy (SECM), a member of the scanning probe microscopies (SPM), uses an ultramicroelectrode as the probe to characterize the localized electrochemical properties of the surfaces (1-3). Although the lateral resolution of SECM is inferior to that of STM or AFM because it is difficult to fabricate a small probe microelectrode with atom-size radius, SECM has abilities of detecting chemical reactions. In addition, it can induce chemical reactions in an extremely small volume. Using the unique properties of SECM, a single molecule (4) or a radical with a short lifetime (5) was recently detected. 

Comstock DJ, Elam JW, Pellin MJ, Hersam MC (2010) Integrated ultramicroelectrode-nanopipet probe for concurrent scanning electrochemical microscopy and scanning ion conductance microscopy. Anal Chem 82(4) 1270-1276... 

Mauzeroll J, Hueske EA, Bard AJ (2003) Scanning electrochemical microscopy. 48. Hg/Pt hemispherical ultramicroelectrodes fabrication and characterization. Anal Chem 75 3880-3889... 

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