Pt microdiscs

Anion detection at microelectrodes has not been studied widely. Amongst the first was the work of de Beer et al. [ 111 ] who manufactured a nitrite sensor with a tip just a few microns in diameter, which could detect nitrite ions down to 1 pM. This proved to be suitable for profiling the concentrations of nitrite anion within biofilms less than 1-mm thick inside water treatment plants. Other workers have found that use of an interdigitated microelectrode array [ 112] allows measurement of iodide via monitoring of its redox peak down to sub-micromole levels, making it a suitable technique for analysing mineral water. Carbon nanotubes coated onto Pt microdiscs have been utilised to make a nitrite sensor [113,114] with detection levels of 0.1 pM. Sulphide has also been detected at nickel microdiscs (50 pm diameter) [115]. 

Figure 1. I-E curves for the oxidation of Cr(CO)6, 2x10 M at a Pt microdisc (r = 5x10" cm) in acetonitrile containing (a) 0.1 M TBAB (b) 10 M TBAB (c) no electrolyte.

TABLE 1. Voltammetry data for the oxidation of Cr(CO)6 2x10 M in acetonitrile at a Pt microdisc (d = SxlO"" cm), containing different concentrations of electrolyte. 

Mark Borisovich Bardin-Shteyn (1919, Odessa-1987, Kinshinev) (Fig. 5.7.6) was doctor of chemical science and fought in WW II. In 1947 he started to teach at KSU and rose from assistant to professor. From 1964 to 1975, he was dean of the chemical faculty. He was a specialist in polarography of platinum metals. His studies on the determination of ft and Pd on solid electrodes and on the application of a rotating Pt microdisc electrode for polarography are well known. 

An array of microwells filled with the bacteria gel was prepared. The PAP was detected in the wells. The release of PAP into the extracellular liquid indicated the P-Gal activity that is the solubility of the MBP. The authors used a Pt microdisc electrode (radius, 10 mm) as the probe set to 0.30 V vs. Ag/AgCl to record the oxidation current of PAP produced in pGal catalyzed hydrolysis of PAPG. 

Single-crystal surfaces behave quite differently, almost no peroxide being produced on Pt(lll) in contact with 0.1 M KOH, the authors attributing this to the fact that OH is adsorbed reversibly on this surface, but irreversibly adsorbed on Pt(lOO) and Pt(llO) [61, 70]. Experiments conducted with platinum microdisc electrodes (2.5 to 12.5 jjLva) have unambiguously shown how the apparent number of electron for O2 reduction is dependent on mass transfer [71]. 

A schematic of a typical SECM is shown in Eig. 4.5. The main components are the bipotentiostat, tip-positioning system, electrochemical cell and data acquisition/ output system. While these basic components are common to almost all SECMs, the SECM tip can differ significantly depending on the particular system under investigation. Due to the ease of fabrication and polishing, microdisc SECM tips are most common. Microdisc tips are constructed by sealing microwires of metals such as Pt... 

Fig. 4.7 Experimental (solid line) and simulated (open circles, open triangles, open squares) CVs recorded at a 5-pm-radius Pt microdisk UME at scan rates of (a) 50, (b) 10 and (c) 1 mV/s, and (d) at a 1-pm-radius microdisc at a scan rate of 10 mV/s during oxidation of 7 mM Fc in [C4mim][BF4] at 25 °C. Potentials are vs. Fc/Fc scale and the simulated voltammograms represent those calculated for a reversible process with a diffusion coefficient of 5 x 10" cmVs. Reprinted with permission from Carano, M Bond, A M (2007) Aust. J. Chem. 60 29-34. Copyright 2007 CSIRO...

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