Biomedical Engineering Reference
In-Depth Information
Figure 11.2
SEM image of (A) the polystyrene template and (B) the three-dimensional
gold i lm [24]. (Reprinted with permission from [24].)
reduction of HAuCl
4
into interspace of the polystyrene template fabricated
on an ITO electrode [24]. h en chemical removal of template by using
organic solvent is done (Figure 11.2).
Although the template-assisted method controls the shape and size
of the nanoporous gold well, but because of the limitation of template
materials, the structure of nanoporous gold can only be adjusted in limited
ways. Meanwhile, an additional operation is needed to remove the tem-
plates; the procedure is complex and limits its development.
11.2.3 Electrochemical Method
Neither the dealloying method nor template-assisted method use pure
gold as the raw material, thus the contamination of the nanoporous struc-
tures with impurities is one of the most serious issues. Furthermore,
preparation of an alloy with a specii c composition is required in the deal-
loying method; and in template-assisted process, elimination of template
is need. h e electrochemical method is an alternative method that solves
these problems. An electrochemical etching of gold through anodizing in
a solution of hydrol uoric acid and dimethylformamide (DMF) to fabricate
nanoporous gold i lms has been reported [14]
As Figure 11.3 shows, the electrochemically etched nanoporous gold
shows tunable pore size and etching depth by tuning the etching conditions.
11.3
Nucleic Acids (NAs)-Based Biosensors
Ultrasensitive detection of DNA has recently attracted much attention
because of its various applications including: clinical diagnosis, environ-
mental monitoring, and the detection and characterization of bacteria
and viruses [28-32]. Specii c detection of DNA is based on the “sandwich
