Nanobiosensors - Biosensors and Biosensor Kinetics - page 102

Huang et al. (2008) have recently developed a novel carbon nanofiber material, which
contains electrospun palladium nanoparticles. In their most recent analysis, Liu et al. (2009)
have mixed the electrospun nickel nanoparticle-loaded carbon nanofibers with mineral oil.
This is their NiCFP electrode. Their intention was to determine glucose concentrations, sans
a mediator or an enzyme.
Liu et al. (2009) report that the NiCF composite was made by carbonizing the electrospun
PAN (polymer)/NiAA composite fibers. This nanocomposite was then mixed with mineral
oil in the ratio of 60/40 w/w. They also report that two steps are required to make these
nanocomposite fibers. They include (a) synthesis of the carbon fiber and (b) deposition of
the Ni catalysts. It is difficult to discharge the nanoparticles from these fibers as they are
deeply embedded in them. Their method, which includes a thermal treatment step prepares
these nanofibers directly and effectively. They further indicate that their nanofibers do not
consist of pure nickel alone, but are a mix of nickel and nickel oxide. An x-ray diffraction
pattern result also indicates that the nanoparticles of nickel and nickel oxide coexist. Their
NiCFP electrode combines the properties of the CF (electrochemical performance such as
good conductivity) with the electrocatalytic activity of the nickel nanoparticles. They demon-
strated clearly that the nickel and nickel oxide particles play an important role in the elec-
trode as the CFP electrode alone did not indicate any current response.
Liu et al. (2009) also report that their simple fabrication method, along with the high
electrocatalytic performance exhibited, offers a biosensor platform that is effective for
the determination of glucose. Furthermore, their biosensor is able to determine 95% of the
glucose concentration within 5 s, and the detection limit is as low as 1 m M. This, according
to them, is better than that obtained by using a nickel complex ( Ojani et al., 2008 ),
CNT (carbon nanotube)-based complex ( Chen et al., 2008; Deng et al., 2008 ), and alloy-
modified electrodes (Li et al., 2008). Their biosensor also demonstrated a wide linear range
(2 m M-2.5 mM). The sensitivity exhibited is 3.3 m A per mM.
Another advantage of the Liu et al. (2009) biosensor is the antifouling activity of its NiCFP
electrode, due to the resistance offered to surface fouling by chloride ions. Other metal and
alloy electrodes are subject to fouling by chloride ions ( Sun et al., 2001 ). An additional
advantage of the Liu et al. (2009) biosensor is its good operational stability. The response
that the NiCFP electrode demonstrated was consistent, and not self-inhibited by glucose or
any of its oxidation products on the electrode's surface. Liu et al. (2009) further report that
the high electrocatalytic activity exhibited by the NiCFP electrodes leads to a sensitivity that
is 1.5 times that exhibited by a Ni bulk electrode. This is primarily due to the large electro-
active surface area prevalent in the NiCFP electrode.
Liu et al. (2009) also report that their biosensor exhibited good reproducibility properties.
Also, when their biosensor was stored in a desiccator at room temperature for a month, it lost
only 2% of its response to a 1% glucose solution. Their NiCFP electrode also permitted a