concentration coupled with high diffuse layer potential is essential for good stability. The spherical electrical double layer around the particles determines the extent
and the nature of the chemistry as well as the electron transfer processes involving
colloids. The double layer theories developed by Helmholtz, Grahame, Stern, Gouy
and Chapman to understand the interfaces of an electronic conductor/liquid electrolyte are used to build models to explain colloidal behavior.
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 nanoparticlebased 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.
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.
20.2
Preparation of Nanostructures
Electrochemical studies with nanosized particles require them to be accessible to
the electrode surface where the potential can be controlled. This can be accomplished either by using the metallic colloid along with an inert, planar electrode or
by attaching the nanoparticle onto a conducting matrix. Both these methods have
been demonstrated in the literature [21–25]. In this section, some of the anchoring
methods that are available for this purpose are briefly explained. A few other
methods of preparation are explained wherever appropriate.
Transparent, conducting indium tin oxide (ITO) electrodes are widely used to
generate assemblies for simultaneous electrochemical and spectroscopic measurements [26]. Oxide surfaces such as ITO and silica are generally functionalized with
amino- or mercaptosilanes that can further be used to attach metallic particles [23,
24, 27, 28]. Molecules containing carboxylic acid groups are also frequently used to
functionalize titania and alumina surfaces [29, 30]. Gold is one of the most extensively studied electrode materials for anchoring various molecules. The procedure involves the assembly of a base monolayer consisting of bifunctional groups
where one of them is sulfur or nitrogen based so that the metal–sulfur/nitrogen
interaction takes place spontaneously [31]. The other end of the functionalized
molecule is used to attach the nanoparticles. Electrophoretic deposition is also
reported to form an assembly of particles on conducting matrices [32]. Bharathi
and Lev demonstrated the electrochemical deposition of gold particles from an
20.2 Preparation of Nanostructures 647
and the nature of the chemistry as well as the electron transfer processes involving
colloids. The double layer theories developed by Helmholtz, Grahame, Stern, Gouy
and Chapman to understand the interfaces of an electronic conductor/liquid electrolyte are used to build models to explain colloidal behavior.
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 nanoparticlebased 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.
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.
20.2
Preparation of Nanostructures
Electrochemical studies with nanosized particles require them to be accessible to
the electrode surface where the potential can be controlled. This can be accomplished either by using the metallic colloid along with an inert, planar electrode or
by attaching the nanoparticle onto a conducting matrix. Both these methods have
been demonstrated in the literature [21–25]. In this section, some of the anchoring
methods that are available for this purpose are briefly explained. A few other
methods of preparation are explained wherever appropriate.
Transparent, conducting indium tin oxide (ITO) electrodes are widely used to
generate assemblies for simultaneous electrochemical and spectroscopic measurements [26]. Oxide surfaces such as ITO and silica are generally functionalized with
amino- or mercaptosilanes that can further be used to attach metallic particles [23,
24, 27, 28]. Molecules containing carboxylic acid groups are also frequently used to
functionalize titania and alumina surfaces [29, 30]. Gold is one of the most extensively studied electrode materials for anchoring various molecules. The procedure involves the assembly of a base monolayer consisting of bifunctional groups
where one of them is sulfur or nitrogen based so that the metal–sulfur/nitrogen
interaction takes place spontaneously [31]. The other end of the functionalized
molecule is used to attach the nanoparticles. Electrophoretic deposition is also
reported to form an assembly of particles on conducting matrices [32]. Bharathi
and Lev demonstrated the electrochemical deposition of gold particles from an
20.2 Preparation of Nanostructures 647