Electrochemistry with Nanoparticles

This chapter is organized into sections corresponding to various electrochemical characteristics of nanometallic particles. The introduction gives a brief idea of the basics of colloids together vith related literature. Subsequently, the electrochemistry with nanoparticles and ensembles of nanoelectrodes is explained followed by the electrochemical coulomb staircase behaviour of monolayer-protected nanometallic clusters. The investigation of nanoparticles using techniques based on combinations of different spectroscopic and electrochemical techniques is then reviewed. Sensors and electrocatalysis form the next sections and finally a summary and perspectives are given. 

Most of the electrochemical phenomena occur in size regimes that are very small. The effects of size on diffusion kinetics, electrical double layer at the interface, elementary act of charge transfer and phase formation have recently been reviewed by Petrri and Tsirlina [12]. Mulvaney has given an excellent account of the double layers, optical and electrochemical properties associated with metal colloids [11]. Special emphasis has been given to the stability and charge transfer phenomenon in metal colloid systems. Willner has reviewed the area of nanoparticle-based functionalization of surfaces and their applications [6-8]. This chapter is devoted to electrochemistry with nanoparticles. One of the essential requirements for electrochemical studies is that the material should exhibit good conductivity. 

Devarajan, S. Sampath, S. Electrochemistry with nanoparticles. In The Chemistry of Ncmomaterials Synthesis, Properties, and Applications, C. N. R. Rao, Achim Muller, A. K. Cheetham, (eds.) Wiley-VCH Verlag GmbH Co. KGaA, Berlin, Germany, published on-line January 2005 (DOI 10.1002/352760247X.ch20) 2004, Chapter 20. 

The lure of new physical phenomena and new patterns of chemical reactivity has driven a tremendous surge in the study of nanoscale materials. This activity spans many areas of chemistry. In the specific field of electrochemistry, much of the activity has focused on several areas (a) electrocatalysis with nanoparticles (NPs) of metals supported on various substrates, for example, fuel-cell catalysts comprising Pt or Ag NPs supported on carbon [1,2], (b) the fundamental electrochemical behavior of NPs of noble metals, for example, quantized double-layer charging of thiol-capped Au NPs [3-5], (c) the electrochemical and photoelectrochemical behavior of semiconductor NPs [4, 6-8], and (d) biosensor applications of nanoparticles [9, 10]. These topics have received much attention, and relatively recent reviews of these areas are cited. Considerably less has been reported on the fundamental electrochemical behavior of electroactive NPs that do not fall within these categories. In particular, work is only beginning in the area of the electrochemistry of discrete, electroactive NPs. That is the topic of this review, which discusses the synthesis, interfacial immobilization and electrochemical behavior of electroactive NPs. The review is not intended to be an exhaustive treatment of the area, but rather to give a flavor of the types of systems that have been examined and the types of phenomena that can influence the electrochemical behavior of electroactive NPs. 

This includes two classes of materials namely, semiconductors and metals. There have been excellent reviews on electrochemistry with semiconductor nanoparticles [18-20]. Here, we confine ourselves to electrochemical studies with metallic nanoparticles. 

Numerous electrochemical platforms have been developed for DNA detection, including direct electrochemistry of the DNA bases [5], electrochemistry of different polymer-modified screen-printed chips [6], electrochemistry of DNA-specific redox indicator molecules or enzymes [7,8], electrochemistry of signal amplification with nanoparticles (NPs) such as gold, silver or magnetic particles [9,10], and dsDNA r-stacked mediated charge transport chemistry [4, 7,11,12]. 

Kwon, S.J., Zhou, H.J., Fan, F.R.F. et al. (2011) Stochastic electrochemistry with electrocatalytic nanoparticles at inert ultramicroelectrodes-theory and experiments. Physical Chemistry Chemical Physics, 13, 5394—5402. 

Reisee et al. [52] first described a pulsed electrodeposition and pulsed out-of-phase ultrasound to prepare copper nanopowders. Such an electrochemical method has since then employed to synthesize a variety of nanoparticles. Mancier et al. [53] have prepared Cu20 nanopowders (8 nm) with very high specific surface area of 2,000 m2/g by pulsed ultrasound assisted-electrochemistry. 

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