Derivatized gold electrodes

FossBJ, Ion A, Partali V, Sliwka HR, and BanicaFG. 2006b. Electrochemical and EQCM investigation of a selenium derivatized carotenoid in the self-assembled state at a gold electrode. Journal of Electroanalytical Chemistry 593(1-2) 15-28. 

Figure 8.3 Rate constants for the reduction of [Mo(CN)g]3 (upper curve) and [W(CN)g]3 (lower curve) on gold electrodes derivatized with a monolayer of HO(CH2)i6SH. The electrode potential is given with respect to a Ag/AgCl electrode in saturated KC1. Data taken from Ref. 2.

Iodide in urine [39] and catecholamines [40,41] are example of analytes recently detected electrochemically and studied under IPC conditions. Pulsed amperometric detection on a gold electrode was used to detect etimicin [42] and gentamicin [43] in commercial samples, thus avoiding tedious pre-column derivatization. Heterocyclic aromatic amines in soup cubes [44] were determined by a coulometric electrode array detector, and the coulometric detection of a quinone-bearing drug candidate [45] allowed the study of electrochemical properties. 

Fig. 1.5. Dependence of the electroenz3maatic response (Ay) of lactate dehydrogenase modified gold electrodes on the time of protein layer growth (a) mixed 3-mercaptopropamol and 3-mercaptopropionic acid SAM derivatized with 1,4-diamino-butane ligand fi-ee- ( ), CB- (O) and Ll-anchored (A) (b) cystamine SAM derivatized with fumaric acid ligand fi-ee- ( ), CB- (O) and Ll-anchored (A). The monolayers were incubated in a 0.36mgml enzyme solution in 50 mM Na-phosphate buffer, pH 7.0. Reproduced from [240] with permission.

Thiol-derivatized cobalt porphyrins self-assemble on the surface of gold electrodes. The monolayers obtained catalyse reduction of oxygen to hydrogen peroxide. These layers retain their activity after as many as 105 turnovers378,379. 

Electroactive monolayers of thiol-derivatized hydroquinones on the surface of platinum electrodes were prepared and studied by Hubbard and coworkers even before Nuzzo and Allara reported formation of the first gold-thiol monolayers . The redox potentials of quinone- or hydroquinone-containing monolayers vary with pH with a slope of 60 mV pH indicating a 2e -I- 2H+ reaction . This observation was used in an elegant study by Hickman and coworkers. They codeposited hydroquinone and ferrocene-containing thiols on the surface of a gold electrode. The half-wave potential of the latter does not depend on the pH value of the solution, and therefore can be used as a reference. The whole assembly acts thus as a pH-sensitive sensor which does not require any separate reference electrodes . 

Postlethweite, T.A., J.E. Hutchison, K.W. Hathcock, and R.W. Murray (1995). Optical electrochemical, and electrocatalytic properties of self-assembled thiol-derivatized porphyrins on transparent gold electrodes. Langmuir 11, 4109-4116. 

Gold electrodes derivatized with these monolayers permit the voltammetric detection of ferrocene in the adjacent solution at concentrations as low as 5 iM[32]. This finding indicates that the surface-attached CD cavities effectively complex the ferrocene molecules from the solution, making their detection possible at concentrations 1-2 orders of magnitude lower than those required for conventional voltammetric techniques on bare gold electrodes. 

HPLC methods are extremely sensitive toward sugars and sugar derivatives, an important advance over detection by means of refractive index measurement lying in the use of ion chromatography with pulsed amperometric detection at copper, platinum, or gold electrodes. Analytical processes may be fully automated using various postcolumn derivatization procedures as required. 

Fujita K, Nakamura N, Ohno H, Leigh BS, Niki K, Gray HB, Richards JH (2004) Mimicking protein-protein electron transfer voltammetry of Pseudomonas aeruginosa azurin and the thermus thermophilus Cu-A domain at omega-derivatized self-assembled-monolayer gold electrodes. J Am Chem Soe 126 13954-13961... 

The same authors developed a much more robust label-free impedimetric immunosensor, based on the same IDpE arrays conveniently derivatized through covalent procedures to ensure reliability and to prevent nonspecific adsorption [42]. Atrazine-BSA was covalently immobilized on the surface of the IDpEs previously activated with (3-glycidoxypropyl)trimethoxysilane via the side chain amino groups of lysines or arginines with the epoxy groups on the device surface. Before, the gold electrodes were blocked... 

Xue Z, Yang J, Zhi F, Wang W, Liu X, Lu X (2009) Preparation, characterization, and electrochemical behaviors of self-assembled monolayCT on gold electrode surface with mercapto-derivatized cobaltous porphyrin. Anal Lett 42(4) 668-677... 

Zak J, Yuan H, Ho M, Woo LK, Porter MD (1993) Thiol-derivatized metalloporphyrins monomolecular films for the electrocatalytic reduction of dioxygen at gold electrodes. Langmuir 9 2772—2774... 

Mashazi P, Nyokong T (2010) Electrocatalytic smdies of covalently immobilized metal tetra-amino phthalocyanines onto derivatized, screen-printed gold electrodes. Microchim Acta 171 321-332... 

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