Adsorption electrochemical

Figure 5.22 reveals the ability of solid state electrochemistry to create new types of adsorption on metal catalyst electrodes. Here oxygen has been supplied not from the gas phase but electrochemically, as 02 via current application for a time, denoted tj, of 1=15 pA at 673 K, i.e. at the same temperature used for gaseous O2 adsorption (Fig. 5.21). Figure 5.23 shows the effect of mixed gaseous-electrochemical adsorption. The Pt surface has been initially exposed to po2 =4x1 O 6 Torr for 1800 s (7.2 kL) followed by electrochemical O2 supply (1=15 pA) for various time periods ti shown on the figure, in order to simulate NEMCA conditions. 

Peter LM, Reid ID, Scharifker BR (1981) Electrochemical adsorption and phase formation on mercury in sulphide ion solutions. 1 Electroanal Chem 119 73-91 Da Silva Pereira MI, Peter LM (1982) Photocurrent spectroscopy of semiconducting anodic films on mercury. J Electroanal Chem 131 167-179... 

Palchetti I, Mascini M (2005) Electrochemical Adsorption Technique for Immobilization of Single-Stranded Oligonucleotides onto Carbon Screen-Printed Electrodes. 261 27-43 Pascal R, Boiteau L, Commeyras A (2005) From the Prebiotic Synthesis of a-Amino Acids Towards a Primitive Translation Apparatus for the Synthesis of Peptides. 259 69-122 Paulo A, see Santos I (2005) 252 45-84 Perez EM, see Leigh DA (2006) 265 185-208 Perret F, see Coleman AW (2007) 277 31-88 Perron H, see Coleman AW (2007) 277 31-88 Pianowski Z, see Winssinger N (2007) 278 311-342 Piestert F, see Gansauer A (2007) 279 25-52... 

The situation becomes even more complex in the case of electrochemical adsorption. Kolb et al. [17] first demonstrated clearly that the binding energy of adsorbed... 

Ikariyama [2] described a unique method for the preparation of a glucose oxidase (GOD) electrode in their work. The method is based on two electrochemical processes, i.e. electrochemical adsorption of GOD molecules and electrochemical growth of porous electrode. GOD immobilized in the growing matrix of platinum black particles is employed for the microfabrication of the enzyme electrode. It demonstrated high performance with high sensitivity and fast responsiveness. 

Electrochemical Adsorption at Catalytic Electrodes. A classification of adsorption processes at catalytic electrodes, such as platinum or rhodium, first proposed by Horanyi (24) and further developed by Wieckowski (21,25,26), categorizes adsorption processes into three fundamental groups ... 

Wieckowski, A. The Analysis of Electrochemical Adsorption Processes on Platinum P. W. U., Warsaw, Poland, 1984. 

Yu Runlan, Qiu Guanzhou, Hu Yuehua, Qin Wenqing, 2005. Electrochemical adsorption behaviour and mechanism of diethyldithiocarbamate on surface of marmatite. The Chinese Journal of Nonferrous Metals, 15(9) 1452 - 1457 (in Chinese)... 

Flowever, the focus of the major part of the chapters lies on the couphng chemistry used for DNA immobilization. Successful immobihzation techniques for DNA appear to either involve a multi-site attachment of DNA (preferentially by electrochemical and/or physical adsorption) or a single-point attachment of DNA (mainly by surface activation and covalent immobihzation or (strept)avidin-biotin linkage). Immobilization methods described here comprise physical or electrochemical adsorption, cross-linking or entrapment in polymeric films, (strept)avidin-biotin complexation, a surface activation via self-assembled monolayers using thiol linker chemistry or silanization procedures, and finally covalent coupling strategies. 

Physical or electrochemical adsorption uses non-covalent forces to affix the nucleic acid to the solid support and represents a relatively simple mechanism for attachment that is easy to automate. Adsorption was favoured and described in some chapters as suitable immobilization technique when multisite attachment of DNA is needed to exploit the intrinsic DNA oxidation signal in hybridization reactions. Dendrimers such as polyamidoamine with a high density of terminal amino groups have been reported to increase the surface coverage of physically adsorbed DNA to the surface. Furthermore, electrochemical adsorption is described as a useful immobihzation strategy for electrochemical genosensor fabrication. 

Electrochemical Adsorption Technique for Immobilization of Single-Stranded Oligonucleotides onto Carbon Screen-Printed Electrodes I. Palchetti M. Mascini... 

This method involves electrochemical deposition of the MPc onto CNT-modified electrode surface by repetitive cycling in a concentrated MPc solution (1 mM) within a specific potential window. The first cyclic voltammetric scan is usually similar to subsequent scans, indicating the formation of monomeric species only. Ozoemena et al [11] found that on certain occasions, as reported recently [11] during the electro-deposition of CoTAPc onto a basal plane pyrolytic graphite electrode (BPPGE) pre-modified with SWCNT, both cathodic and anodic waves may decrease continually and then stabilizes at a certain scan (a process known as electrochemical adsorption or simply called electrosorption ). 

Structural aspects of electrochemical adsorption of inorganic ions and neutral organic molecules and water dipoles on quasi-perfect cadmium electrode were also studied [19]. 

Wu et al. have studied adsorption and reaction of 2-iodoethanol [177] and acetaldehyde [178] on Ag(lll). Doubovaet al. [179] have studied adsorption of amyl alcohol on Ag(lll) electrodes in 0.05 M KGIO4 solutions and explained the observed differences and inconsistencies in the light of the applied experimental technique (e.g. the role of ac frequency) and the electrode surface preparation procedure. Generally, amyl alcohol was adsorbed less on Ag(lll) than on Hg. The electron-induced surface reactions of methyl formate [180] and methanol [181] on Ag(l 11) have been studied by Schwaner and White. Foresti et al. [182] have investigated electrochemically, adsorption of 1,5-pentanediol on the Ag(lll) and Ag(llO) faces. 

Underpotential deposition (UPD) is the electrochemical adsorption and (partial) reduction of a submonolayer or monolayer of cations on a foreign metal substrate at potentials more positive than the reversible potential of the deposited metal [141]. The UPD phenomenon is used in many fundamental and applied studies because it offers a means of controlling coverages during electrodeposition in a very concise manner. Until recently, most of the information obtained about the structure of the overlayers deposited on single crystal surfaces has come from indirect means such as current-voltage analysis or by analysis of the deposited films after transfer to a UHV chamber [141]. 

Screening strategy Precipitation and coagulation Membrane processes Ion exchange Electrochemical Adsorption... 

In an effort to develop a rapid and efficient scheme for immobilizing nucleic acids onto carbon screen-printed transducers, many authors took advantage of the strong adsorptive accumulation of these biomolecules at the screen-printed carbon surfaces. In particular, many of them reported that electrochemical adsorption (adsorption controlled by a positive potential) enhances the stability of the probe and this technique was preferentially chosen. 

Keywords Carbon screen printed electrodes Genosensors Electrochemical adsorption Hybridization event Electroactive indicators Indicator-free electrochemical genosensor... 

Thus, this review will focus on electrochemical genosensor developed using carbon screen-printed electrodes as the transducer the methods to immobilize oligonucleotides onto carbon based surfaces will be reviewed and special emphasis will be given to describe the electrochemical adsorptive accumulation. 

A scheme of oligonucleotide immobilization by electrochemical adsorption is shown in Fig. 3. 

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