4 research outputs found
Optically Transparent Carbon Nanotube Film Electrode for Thin Layer Spectroelectrochemistry
Carbon
nanotube (CNT) film was evaluated as an optically transparent
electrode (OTE) for thin layer spectroelectrochemistry. Chemically
inert CNT arrays were synthesized by chemical vapor deposition (CVD)
using thin films of Fe and Co as catalysts. Vertically aligned CNT
arrays were drawn onto a quartz slide to form CNT films that constituted
the OTE. Adequate conductivity and transparency make this material
a good OTE for spectroelectrochemistry. These properties could be
varied by the number of layers of CNTs used to form the OTE. Detection
in the UV/near UV region down to 200 nm can be achieved using these
transparent CNT films on quartz. The OTE was characterized by transmission
electron microscopy, scanning electron microscopy, Raman spectroscopy,
UV–visible spectroscopy, cyclic voltammetry, electrochemical
impedance spectroscopy, and thin layer spectroelectrochemistry. Ferricyanide,
trisÂ(2,2′-bipyridine) rutheniumÂ(II) chloride, and cytochrome
c were used as representative redox probes for thin layer spectroelectrochemistry
using the CNT film OTE, and the results correlated well with their
known properties. Direct electron transfer of cytochrome c was achieved
on the CNT film electrode
Carbon Nanotube Thread Electrochemical Cell: Detection of Heavy Metals
In this work, all
three electrodes in an electrochemical cell were
fabricated based on carbon nanotube (CNT) thread. CNT thread partially
insulated with a thin polystyrene coating to define the microelectrode
area was used as the working electrode; bare CNT thread was used as
the auxiliary electrode; and a micro quasi-reference electrode was
fabricated by electroplating CNT thread with Ag and then anodizing
it in chloride solution to form a layer of AgCl. The Ag|AgCl coated
CNT thread electrode provided a stable potential comparable to the
conventional liquid-junction type Ag|AgCl reference electrode. The
CNT thread auxiliary electrode provided a stable current, which is
comparable to a Pt wire auxiliary electrode. This all-CNT thread three
electrode cell has been evaluated as a microsensor for the simultaneous
determination of trace levels of heavy metal ions by anodic stripping
voltammetry (ASV). Hg<sup>2+</sup>, Cu<sup>2+</sup>, and Pb<sup>2+</sup> were used as a representative system for this study. The calculated
detection limits (based on the 3σ method) with a 120 s deposition
time are 1.05, 0.53, and 0.57 nM for Hg<sup>2+</sup>, Cu<sup>2+</sup>, and Pb<sup>2+</sup>, respectively. These electrodes significantly
reduce the dimensions of the conventional three electrode electrochemical
cell to the microscale
Carbon Nanotube-Loaded Nafion Film Electrochemical Sensor for Metal Ions: Europium
A Nafion film loaded with novel catalyst-free
multiwalled carbon
nanotubes (MWCNTs) was used to modify a glassy carbon (GC) electrode
to detect trace concentrations of metal ions, with europium ion (Eu<sup>3+</sup>) as a model. The interaction between the sidewalls of MWCNTs
and the hydrophobic backbone of Nafion allows the MWCNTs to be dispersed
in Nafion, which was then coated as a thin film on the GC electrode
surface. The electrochemical response to Eu<sup>3+</sup> was found
to be ∼10 times improved by MWCNT concentrations between 0.5
and 2 mg/mL, which effectively expanded the electrode surface into
the Nafion film and thereby reduced the diffusion distance of Eu<sup>3+</sup> to the electrode surface. At low MWCNT concentrations of
0.25 and 0.5 mg/mL, no significant improvement in signal was obtained
compared with Nafion alone. Scanning electron microscopy and electrochemical
impedance spectroscopy were used to characterize the structure of
the MWCNT–Nafion film, followed by electrochemical characterization
with Eu<sup>3+</sup> via cyclic voltammetry and preconcentration voltammetry.
Under the optimized conditions, a linear range of 1–100 nM
with a calculated detection limit of 0.37 nM (signal/noise = 3) was
obtained for determination of Eu<sup>3+</sup> by Osteryoung square-wave
voltammetry after a preconcentration time of 480 s
Electrospun Carbon Nanofiber Modified Electrodes for Stripping Voltammetry
Electrospun
polyacrylonitrile (PAN) based carbon nanofibers (CNFs)
have attracted intense attention due to their easy processing, high
carbon yield, and robust mechanical properties. In this work, a CNF
modified glassy carbon (GC) electrode that was coated with Nafion
polymer was evaluated as a new electrode material for the simultaneous
determination of trace levels of heavy metal ions by anodic stripping
voltammetry (ASV). Pb<sup>2+</sup> and Cd<sup>2+</sup> were used as
a representative system for this initial study. Well-defined stripping
voltammograms were obtained when Pb<sup>2+</sup> and Cd<sup>2+</sup> were determined individually and then simultaneously in a mixture.
Compared to a bare GC electrode, the CNF/Nafion modified GC (CNF/Nafion/GC)
electrode improved the sensitivity for lead detection by 8-fold. The
interface properties of the CNF/Nafion/GC were characterized by electrochemical
impedance spectroscopy (EIS), which showed the importance of the ratio
of CNF/Nafion on electrode performance. Under optimized conditions,
the detection limits are 0.9 and 1.5 nM for Pb<sup>2+</sup> and Cd<sup>2+</sup>, respectively