Infrared Study of Charge Carrier Confinement in Doped (6,5) Carbon Nanotubes

The comprehensive study of resistivity and low frequency (10[Formula: see text]Hz–20[Formula: see text]kHz) noise characteristics of hybrid polymer composites with multi-walled carbon nanotubes (MWCNTs) and onion-like carbon (OLC) particles in one material have been carried out in the wide temperature range ((75–380) K). The characteristic dependences on the fillers density and the dominant conduction mechanisms were investigated. At low temperature ((75–170) K), the resistivity dependences on temperature are well-fitted by the Mott’s formula for the quasi-one-dimensional charge carrier variable range hopping and Arrhenius law. At temperatures above 300[Formula: see text]K, the resistance increases with temperature due to matrix expansion and decreases due to the onset of the conductivity in the matrix. Low frequency voltage noise spectra comprise of 1/[Formula: see text] and Lorentzian-type components with characteristic times in the range from 0.1[Formula: see text][Formula: see text]s to 10[Formula: see text][Formula: see text]s; the noise spectral density in the region of Ohmic resistance is proportional to the voltage square. Therefore, thermally activated charge carrier capture centers randomly modulate the sample’s resistance and control the carrier hopping. Impulse noise and more sudden changes of the noise characteristics were observed at the temperatures, where the conduction mechanisms change.

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Tunable Chemical Grafting of Three-Dimensional Poly (3, 4-ethylenedioxythiophene)/Poly (4-styrenesulfonate)-Multiwalled Carbon Nanotubes Composite with Faster Charge-Carrier Transport for Enhanced Gas Sensing Performance

Sensors ◽

10.3390/s20092470 ◽

2020 ◽

Vol 20 (9) ◽

pp. 2470

Author(s):

Hyojae Kim ◽

Yeongseok Jang ◽

Gyeong Won Lee ◽

Seung Yun Yang ◽

Jinmu Jung ◽

...

Keyword(s):

Carbon Nanotubes ◽

Charge Carrier ◽

Multiwalled Carbon Nanotubes ◽

Carrier Transport ◽

Gas Sensing ◽

Three Dimensional ◽

Charge Carrier Transport ◽

Multiwalled Carbon ◽

Gas Molecules ◽

Sensing Performance

The three-dimensional volumetric application of conductive poly (3,4-ethylenedioxythiophene)/poly (4-styrenesulfonate) (PEDOT:PSS) to multiwalled carbon nanotubes (MWCNTs) has not been widely reported. In this study, the applicability of the 3D PEDOT:PSS-MWCNT composite for a gas sensor was investigated with different PEDOT:PSS concentrations. The gas-sensing performance of the 3D PEDOT:PSS-MWCNT composites was investigated using ethanol and carbon monoxide (CO) gas. Overall, in comparison with the pristine MWCNTs, as the PEDOT:PSS concentration increased, the 3D PEDOT:PSS-MWCNT composites exhibited increased conductivity and enhanced gas sensing performances (fast response and recovery times) to both ethanol and CO gases. Importantly, although the PEDOT:PSS coating layer reduced the number of sites for the adsorption and desorption of gas molecules, the charge-carrier transport between the gas molecules and MWCNTs was significantly enhanced. Thus, PEDOT:PSS can be chemically grafted to MWCNTs to enhance the connectivity and conductivity of a 3D network, leading to possible applications in gas sensors.

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