Biomedical Engineering Reference
In-Depth Information
3.2.1
Preparation of AuNPs
h e preparation procedure is very important in terms of nanoparticle
behaviors. It has been demonstrated that catalytic ef ects of some nanopar-
ticles have been shown to be closely connected to the support on which
they are deposited [21]. Also, stabilizing agents, which are controlled by
the preparation conditions, have been directly af ected by the properties of
these nanostructured particles. On the other hand, the size and the unifor-
mity of the nanoparticles are af ected by the type and the amount of reduc-
ing agent employed in synthesis [1].
AuNPs can be prepared electrochemically or via chemical reduction
methods, which ot en leads to colloidal gold. Colloidal gold consists of
octahedral units of gold homogeneously dispersed in a liquid phase [22-
26]. h e chemical preparation method usually involves a simple reduc-
tion of metal salts by reducing agents in a controlled way. Some of the
most well-known and frequently used method to synthesize spherical
gold nanoparticles includes the reduction of gold chloride by citrate. For
smaller ( 2 nm) gold nanoparticles, borohydride reduction is applied
at er an aqueous solution of gold ions is transferred to an organic phase
that includes a phase transfer agent. h e other two methods used for this
purpose are the microoemulsion method, wherein gold salts are reduced
in the aqueous core of inverse micelles, and the seeding method, where
gold seed particles (prepared by one of the other methods) are utilized
to grow more gold in the presence of a weak reducing agent [19]. For the
examination of the obtained structure, transmission electron micros-
copy (TEM) [24] and X-ray photoelectron spectroscopy [25] have been
used (Figure 3.1).
3.2.2 AuNP Modii ed Electrodes
Solid electrodes like glassy carbon (GCE), crystalline gold and highly ori-
entated pyrolytic graphite electrodes [25, 27], and composite electrodes
including carbon paste electrode (CPE) and glassy carbon paste electrode
(GCPE) [3, 22] have been modii ed with colloidal gold. Modii cation of
CPE and GCPE [3, 22] with AuNP was achieved directly by mixing colloi-
dal gold into the paste at the production stage. For preventing the leakage
of the resulting electrode's structure, in some works, dialysis membrane
has been used [3]. Besides this, proper additives like albumin [22] have
been utilized for obtaining better dispersion of gold particles into the
