The impedance and electrical conductivity behavior of gellan gum hydrogels containing the conducting fillers poly(3,4-
ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) and vapour grown carbon nanofibers (VGCNF) is
presented. Impedance analysis showed that an equivalent circuit consisting of a Warburg element in series with a resistor
could be used to model the gels’ behavior. It is demonstrated that the addition of the conducting fillers PEDOT:PSS and
VGCNFs can result in a measurable improvement in the conductivity of hydrogels with high water content and swelling
ratios. Incorporation of combinations of these conducting fillers resulted in an improvement of the conductivity of gellan
gum-containing hydrogels with water content (swelling ratio) of at least 97.5% (40) from 1.2 ± 0.1 mS/cm to 4 ± 0.6 mS/cm.
The inkjet processing of water dispersable polymer carbon nanotube composite materials is reported. Single printed
layers displayed good optical transparency, sheet resistance, and conductivity. It is demonstrated that an alcohol sensor
based on a single printed layer of polymer carbon nanotube composite could operate at a lower voltage compared to a
sensor based on a single printed layer of the polymer.
The production of small diameter (0.7-1.2nm) and high purity single walled carbon nanotubes using a gas-phase catalytic approach has aroused considerable interest in the chemistry of this unique material. Most recently it has been proposed that tubes produced in this manner can be cut by simply grinding them in a soft organic material such as g-cyclodextrin. The results reported on such cutting techniques however concentrated upon microscopy thereby limiting the degree of information, which could be deduced about the type of interaction between the two materials. In this study electronic and vibrational spectroscopy as well as Differential Scanning Calorimetry has been performed upon a ground mixture of the aforementioned single walled carbon nanotubes and γ-Cyclodextrin. The mixture was prepared by grinding in a 30:1 ratio γ-cyclodextrin and single walled carbon nanotubes for approximately two hours with the drop-wise addition of ethanol (1ml) in the first 10 minutes. A similar ground mixture of g-Cyclodextrin and multi walled carbon nanotubes was also prepared to help asses the type and degree of interaction between the single walled carbon nanotubes and the γ-Cyclodextrin. Absorption spectroscopy showed changes to the electronic structure of both the single walled carbon nanotubes and the γ-Cyclodextrin, while evidence from Raman spectroscopy indicates that the cyclodextrins are absorbed via van der Waals forces along the length of the tube inducing a compressive strain. No such evidence for an interaction with multi walled carbon nanotubes was observed suggesting the possibility of a diameter selective interaction. Finally as a comparison a sample containing 5mg of tubes was refluxed in an aqueous solution of γ cyclodextrin (0.3M) for ~72 hour similar to early studies preformed on C60 and γ cyclodextrin
Amino functionalized multi wall carbon nanotubes (MWNT) were reacted with an inorganic Ruthenium complex, {[Ru(dcclbpy)(bpy)2](PF6)2}, in an attempt to covalently attach the Ruthenium complex to the MWNT. The covalent attachment between the Ruthenium complex and the carbon nanotubes is achieved by the formation of an amide group. Absorption and emission spectroscopy indicated that a reaction between the amino functionalized MWNT and the Ruthenium complex occurred. Atomic fore microscopy (AFM) images gave further evidence of a successful attachment of the Ruthenium complex to MWNT by showing multiple junctions between MWNT distinct from naturally occurring splitting of MWNT ropes.
Visible photoluminescence from multiwalled carbon nanotubes (MWNT) was observed on excitation at 1064 nm. Strong nonlinear behavior of the photoluminescence was shown using power law dependence studies. The nonlinear response in MWNT was further investigated using degenerate four wave mixing. An ultrafast response was observed and the magnitude of the third order optical susceptibility, (chi) , was determined to be in the region of 1.2x10-10 esu. Van Hove singularities in the density of states were identified for the first time in MWNT using optical absorption spectroscopy. Optical transitions between the singularities coincide with the spectral region of the photoluminescence. We propose that a multiphoton absorption process, followed by up conversion luminescence, is responsible for nonlinear photoluminescence in MWNT. Photoluminescence from graphitic particles (GP) was also investigated. This is shown to result mainly from thermal behavior and well-known optical centers. Blackbody radiation was observed in the near infrared region in both materials with MWNT exhibiting lower blackbody temperatures than graphite under the same irradiation conditions.
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