An improved process is presented to functionalize carbon nanotubes by potassium
permanganate with the help of phase transfer catalyst (PTC). The PTC helps
to extract potassium permanganate from the solid phase to an organic
solvent phase and improves the efficiency of nanotube oxidation. The
higher reaction efficiency as well as mild reaction conditions leads to a
higher yield of functional nanotube preparation. X-ray photoelectron
spectroscopy confirms the functional groups attached to the nanotube surface. A
preliminary comparison is given of the potassium permanganate oxidation
of nanotubes with and without PTC. This method is believed to be a
potential economic method for large-scale functional nanotube preparation.
Fine platinum nanoparticles (1–5 nm in diameter) were deposited on functionalized
multi-walled carbon nanotubes (MWNTs) through a decoration technique. A novel type
of enzymatic Pt/MWNTs paste-based mediated glucose sensor was fabricated.
Electrochemical measurements revealed a significantly improved sensitivity (around
52.7 µA mM−1 cm−2) for glucose sensing without using any picoampere booster or Faraday cage. In addition,
the calibration curve exhibited a good linearity in the range of 1–28 mM of glucose
concentration. Transmission electron microscopy (TEM) and x-ray photoelectron
spectroscopy (XPS) were performed to investigate the nanoscale structure and the chemical
bonding information of the Pt/MWNTs paste-based sensing material, respectively. The
improved sensitivity of this novel glucose sensor could be ascribed to its higher
electroactive surface area, enhanced electron transfer, efficient enzyme immobilization,
unique interaction in nanoscale and a synergistic effect on the current signal from possible
multi-redox reactions.
A nanocomposite of a multiwalled carbon nanotube and polythiophene was
prepared by functionalizing the nanotube surface with a polythiophene,
poly[3-(2-hydroxyethyl)-2,5-thienylene], containing pendant hydroxyl groups. The
composite was characterized by IR, high resolution TEM and conductivity
measurements. The poly[3-(2-hydroxyethyl)-2,5-thienylene] (PHET) was
synthesized by the oxidation polymerization of 2-(3-thienylethanol) using
FeCl3
and CHCl3. Multiwalled carbon nanotubes were synthesized by a microwave CVD method and
oxidized with potassium permanganate using a phase transfer catalyst in mild conditions.
The COOH groups formed on the nanotube surface were converted to COCl using thionyl
chloride and it was then condensed with the polythiophene at high temperature in
anhydrous DMF. High resolution TEM images showed that the functionalization provided
a firm coating of the conducting polymer on nanotube walls. This nanocomposite with
PHET grafted to CNT showed higher conductivity than a nanocomposite of PHET and
CNT in the same percentage weight composition prepared by ultrasonic mixing of the two.
Such a material was designed and synthesized with a view to electronic and sensor
applications.
This paper presents the design and development of a passive wireless sensor for the detection of bio-hazard materials and vapors using chemiresistive thin films. Composite polymer thin film with functionalized carbon nanotubes (f-CNT) and polymethylmethacrylate (PMMA) is employed as a sensing material. It is investigated that resistance change is determined with the concentration of dichloromethane vapors diffused into composite thin film, due to electrical transition from direct contact to tunneling in carbon nanotube nanojunctions. The chemiresistive film is integrated into a passive wireless system which works based on the change in phase of the reflected RF signal. Measurement results of sensors in a wireless sensing system show a large differential phase shift, which can be utilized for remote monitoring of bio-hazard vapors in real time.
Multiwalled carbon nanotubes (MWNTs) were functionalized by oxidation with
potassium permanganate using a phase transfer catalyst. The functionalized
nanotubes (f-CNTs) were allowed to react with a functional chemical such as
3-methacryloxypropyltrimethoxysilane (3-MPTS). The f-CNTs and the reaction product of
f-CNTs and 3-MPTS (fs-CNTs) were characterized by Fourier transform infrared and
energy dispersion spectroscopy and also by scanning electron microscopy and transmission
electron microscopy analysis. The MWNTs attached to the organofunctional moieties have
a greater versatility for further utilization of nanotubes in different applications.
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