Biomedical Engineering Reference
In-Depth Information
due to the exceptionally high surface-to-volume ratio of the reinforcing
phase and/or its exceptionally high aspect ratio. h e reinforcing material
can be made up of particles (e.g., minerals), sheets (e.g., exfoliated clay
stacks) or i bers (e.g., carbon nanotubes or electrospun i bers). h e area of
the interface between the matrix and reinforcement phase(s) is typically
an order of magnitude greater than for conventional composite materials.
h is large amount of reinforcement surface area means that a relatively
small amount of nanoscale reinforcement can have an observable ef ect on
the macroscale properties of the composite. For example, adding carbon
nanotubes improves the electrical and thermal conductivity. Other kinds
of nanoparticulates may result in enhanced optical properties, dielectric
properties, heat resistance or mechanical properties such as stif ness,
strength and resistance to wear and damage. In general, the nano-rein-
forcement is dispersed into the matrix during processing. h e percentage
by weight (called mass fraction) of the nanoparticulates introduced can
remain very low (on the order of 0.5% to 5%) due to the low i ller per-
colation threshold, especially for the most commonly used nonspherical,
high-aspect-ratio i llers (e.g., nanometer-thin platelets such as clays, or
nanometer-diameter cylinders such as carbon nanotubes).
Zhang
et al.
reported a synthesis protocol to prepare novel compos-
ite imprinted material by a surface imprinting technique incorporating
MWCNTs layer, melamine as a template, MAA as a functional monomer,
and EGDMA as a crosslinker (Figure 12.28) [63].
h e imprinted/MWCNTs sorbent was characterized by a scanning elec-
tron microscope (SEM). Adsorption dynamics and a Scatchard adsorp-
tion model were employed to evaluate the adsorption process. h e results
showed that the imprinted/MWCNTs sorbent displayed a rapid dynamic
adsorption and a high adsorption capacity of 79.9 μmol g
-1
toward
melamine. Applied as a sorbent, the imprinted/MWCNTs sorbent was
used for the determination of melamine in a real sample by online solid-
phase extraction HPLC. An enrichment ratio of 563-fold, detection limit
(S/N=3) of 0.3 μg L
-1
, and quantii cation limit of 4.5 μg L
-1
were achieved
during the experiment.
Some nanoparticle-MWCNTs composites are also reported in the liter-
ature, viz., Huang
et al.
developed a novel sensitive molecularly imprinted
electrochemical sensor for selective detection of tyramine by combination
of MWCNT-AuNP composites and chitosan [64]. h e MWCNT-AuNP
composites were introduced for the enhancement of electronic trans-
mission and sensitivity. Chitosan acts as a bridge for the imprinted layer
and the MWCNT-AuNP composites. h e MIP was synthesized using
tyramine as the template molecule, and silicic acid tetracthyl ester and
