Au NPs

Figure 16. Effect of contact structure on the catalytic activity in CO oxidation over supported Pt and Au NPs.

To fulfill both the requirement of CFME for the practical applications and the necessity of Au substrate to assemble so-called promoters to construct the third-generation biosensor, Tian el al. have combined the electrochemical deposition of Au nanoparticles (Au-NPs) onto carbon fiber microelectrodes with the self-assembly of a monolayer on these Au-NPs to facilitate the direct electron transfer of SOD at the carbon fiber microelectrode. The strategy enabled a third-generation amperometric 02 biosensor to be readily fabricated on the carbon fiber microelectrode. This CFME-based biosensor is envisaged to have great potential for (he detection of 02" in biological systems [158],... 

The Au-NPs were electrodeposited on the carbon fiber microelectrodes from 0.5 M H2S04 solution containing l.OmM Na AuCl4] by applying a potential step from 1.1 V to 0V for 30 s. Cysteine-modified Au-NPs-electrodeposited CFMEs were prepared by... 

Figure 6.14 (left panel) displays amperometric responses of the Cu, Zn-SOD/Cys/ Au-NP/CFME to successive addition of 02 at (a) +250mV and (b) 150mV. The... 

Murray et al. demonstrated in two seminal contributions that freely diffusing, monodisperse hexanethiol-capped 1.6-nm Au-NPs ( Au145) exhibit sequential... 

Electrostatic hybridization can also be achieved through electrophoretic deposition (Fig. 5.7(a)). Niu et al. electrophoretically coated an indium doped tin oxide (ITO) electrode with GO in dimthethyl formamide (DMF) [92]. The GO coated ITO was then submerged in a solution of Au NPs, a bias was applied and the negatively charged NPs coated the GO/ITO electrode. The process could be repeated a number... 

Fig. 5.7 (a), (b) Schematic of electrophoretic deposition of GO and Au NPs to form layered hybrid structure (c). Altered and reprinted with permission from [92] (2012), Wiley. 

Fig. 5.11 Schematic of the stepwise preparation of Fe304-PDA-RG0-Au NP hybrid via ex situ electrostatic assembly and in situ Au NP reduction.

Fig. 5.14 (a) Schematic of SEED process of metal NP deposition on metai surface supported nanoparticie. (b) Example of Au NP deposition on CVD grown graphene on Cu foil, scale 1pm. Reproduced with permission from [143], (2012) Elsevier. 

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. 

Marken s group also prepared LbL films from combinations of positively charged 6-nm diameter Ti02 NPs and negatively charged 20 nm diameter Au NPs, using an approach in which the polymeric binder for the LbL structure was alternated between... 

Nafion and PDDA [58]. Thermal treatment of the resulting films gave a mesoporous Ti02 matrix with Au NPs embedded within and dispersed on top of the Ti02 matrix. Only about 10% of the Au surface area was electrochemically active, suggesting that a large fraction of the Au NPs was not well coimected to the underlying electrode surface. These mesoporous deposits were shown to be effective electrocatalysts for NO and nitrite oxidation. 

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