Chemistry Reference
In-Depth Information
1.53 nm
Secondary
hydroxyls (Head)
0.78 nm
van der Waals forces
Hydrogen bond
Primary hydroxyls (Tail)
Acted as molecular
bricks
Figure 14.2
Schematic picture of the MWCNTs-
b
-CD composites formation mechanism. Adapted from [60].
© 2008 American Chemical Society.
Novel nanocomposites of
β
-cyclodextrin and MWCNTs have also been prepared and deposited on glassy
carbon substrates to prepare
-CyDex/MWNT modified electrodes. These novel modified electrodes offer a
new strategy for the simultaneous determination of guanine (G), adenine (A) and thymine (T). Well separated
voltammetric peaks are obtained between G and A (330 mV), A and T (170 mV) mixtures. The detection limits
for individual analysis of A, T and G were 0.75, 6.768 and 33.67 nmol l
−1
, respectively. The functional properties
of the composite films when differential pulse voltammetry was used showed that the
β
-CyDex/MWNT
nanocomposites modified electrodes were sensitive and could be readily applied in biosensor devices [60].
Due to its extraordinary electronic, thermal and mechanical properties, graphene has emerged as a
fascinating material in electronic, optoelectronic and sensing applications. Chemical reduction of graphene
oxide (GO) is considered to be an efficient approach to produce processable graphene sheets on a large scale.
Different reducing agents are used for the chemical reduction of GO but, unfortunately, the reducing agents
involved are hazardous. Furthermore, most chemical reduction processes are time-consuming and complicated.
There are a few reports on environmentally-friendly processes to reduce graphene oxide to graphene either
by chemical or electrochemical methods. However, a 'unified green approach' to the overall process of
graphene synthesis has not been achieved yet. Among others, a method based on the use of aluminium
powder in acid medium has been recently reported. Though the reduction mechanism is still unclear, this
procedure provides a new green route to prepare graphene sheets with high purity and high electrical
conductivity on a large scale without toxicity [61]. A microwave-based approach towards eco-friendly
synthesis of graphene nanosheets, with advantages such as simplicity, high productivity, low cost and short
processing times has also been described [62]. Together with such procedures, green methods for the
preparation of stable dispersions of graphene without the need of stabilizers are also being developed. For
example, an environmentally friendly freeze drying process which allows the preparation of solvent-free
graphene nanosheets, has been recently described. [63].
β
14.2.2.2 Metal nanoparticles
Green methods for the preparation of gold nanoparticles have appeared in the literature in the last years. An
interesting example of the fabrication of gold nanostructured films is based on the prior oxidation of a gold
electrode surface at a high potential of 10V followed by the reduction of the gold oxides using
β
-D-glucose
