Composites of Polyvinyl Alcohol and Carbon (Coils, Undoped and Nitrogen Doped Multiwalled Carbon Nanotubes) as Ethanol, Methanol and Toluene Vapor Sensors (original) (raw)
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Journal of Nanoscience and Nanotechnology, 2011
We report the preparation of inexpensive ethanol sensor devices using multiwalled carbon nanotube-polyvinyl alcohol composite films deposited onto interdigitated electrodes patterned on phenolite substrates. We investigate the frequency dependent response of the device conductance and capacitance showing that higher sensitivity is obtained at higher frequency if the conductance is used as sensing parameter. In the case of capacitance measurements, higher sensitivity is obtained at low frequency. Ethanol detection at a concentration of 0.3 ppm in air is demonstrated. More than 80% of the sensor conductance and capacitance variation response occurs in less than 20 s.
The investigation of sensing mechanism of ethanol vapour in polymer-nanostructured carbon composite
Central European Journal of Physics, 2010
Polymer-nanostructured carbon composites (PNCC) using three different polymers as composite matrix materials (polyvinylacetate (PVAc), polyethylene glycol (PEG) and ethylene-vinylacetate copolymer (EVA)) have been developed. High structure carbon black Printex XE2 (Degussa AG) was used as a composites filler. Ethanol vapour sensor-effect of composites was determined as a change of electrical resistance as the composite was held in ethanol vapour for 30 seconds. Reversibility of electrical resistance of PNCC, response stability and repeatability have been measured and compared. The electrical resistance response of EVA-nanostructured carbon composite (EVA-NCC) to ethanol vapour as a function of vinylacetate content in the copolymer has been evaluated. Promising ethanol vapour sensor-effect has been observed for PEG-NCC followed by PVAc-NCC and EVA-NCC.
Materials Science in Semiconductor Processing, 2015
We report for the first time, development of an efficient ethanol sensor using mild functionalized multiwalled carbon nanotubes (MWCNTs). A unique technique to functionalize MWCNT is reported to enhance the performance of the ethanol sensor based on it. The conventional functionalization techniques tend to damage physical structure of carbon nanotubes (CNTs) to a large extent and convert most of their sp 2 bonds into sp 3 bonded carbon atoms. This results in reduction of the available adsorption sites for ethanol vapors on the CNT surface and hence deteriorates the sensitivity. In this work, the functionalization of nanotubes is achieved through direct cycloaddition to π electrons of the CNT that does not hamper the physical structure of the nanotube. High resolution transmission electron microscopy (HRTEM) and Raman spectroscopy studies were employed to confirm the appropriate functionalization for better performance of the sensor. Electrical transport properties of the composites were also studied to understand the quality of the established CNT network. Out of the other functionalization technique, Diels Alder cyclo addition reaction based composite sensor was found to exhibit excellent performance and has an edge over the other reported CNT based sensor.
Ultralow-power alcohol vapor sensors using chemically functionalized multiwalled carbon nanotubes
2007
Alcohol sensors, batch fabricated by forming bundles of chemically functionalized multi-walled carbon nanotubes (f-CNTs) across Au electrodes on SiO 2 /Si substrates using an AC electrophoretic technique, were developed for alcohol vapor detection using an ultra-low input power of ~0.01-1 µW, which is lower than the power required for most commercially available alcohol sensors by more than 4 orders of magnitude. The multi-walled carbon nanotubes (MWCNTs) have been chemically functionalized with the COOH groups by oxidation. We found that the sensors are selective with respect to flow from air, water vapor, and alcohol vapor. The sensor response is linear for alcohol vapor concentrations from 1 to 21 ppm with a detection limit of 0.9 ppm. The transient response of these sensors is experimentally shown to be ~1 s and the variation of the responses at each concentration is within 10 % for all of the tested sensors. The sensors could also easily be reset to their initial states by annealing the f-CNTs sensing elements at a current of 100-200 µA within ~100-200 s. We demonstrated that the response of the sensors can be increased by 1 order of magnitude after adding the functional group COOH onto the nanotubes, i.e., from ~0.9 % of a bare MWCNTs sensor to ~9.6 % of an f-CNTs sensor with a dose of 21 ppm alcohol vapor.
Poly(m-aminophenol)/amine groups functionalized multi-walled carbon nanotube composite was prepared by in-situ chemical polymerization and the film of the nanocomposite have been demonstrated as chemo-resistive sensor for ethanol. The functionalization of nanotube and the interfacial interaction between the poly(m-aminophenol) and functionalized nanotube within their composite was confirmed by Fourier transform infrared spectroscopy, X-beam photoelectron spectroscopy and Raman spectroscopy. Formation of polymer layers on the surfaces of nanotube was demonstrated form the morphological analysis of the nanocomposite by scanning electron microscopy and transmission electron microscopy. The percentage of functionalized nanotube was optimized as 2 wt% within the polymer matrix in terms of highest average DC-conductivity achieved as 32×10 −2 S cm −1 for that composition. The responses of nanocomposite with optimized composition toward various aliphatic alcohols vapor under dynamic flow with air were examined. The good response times and reasonable recovery times with significantly selective response for ethanol vapor was recorded.
Study of Ethanol Vapour Sensing Behaviour by Polypyrrole-multiwall Carbon Nanotubes Nanocomposites
Journal of Physical Science
Polypyrrole-multiwall carbon nanotubes (PPy/MWCNT) nanocomposites were synthesised by in-situ chemical oxidative polymerisation method. The MWCNTs were functionalised prior to the formation of nanocomposites. These nanocomposites were characterised by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA) to study the effect of incorporation of functionalised MWCNT in PPy matrix. The results showed the successful formation of PPy/MWCNT nanocomposite and there is significant interaction between PPy and MWCNTs. The response of the prepared PPy/ MWCNT nanocomposites sensors was studied in the form of sensitivity towards ethanol vapours. Results showed that the response increases with ethanol concentration and it is also affected by the MWCNT content in PPy matrix.
Fabrication and Characterization of Carbon Nanotube/Poly(vinyl alcohol) Composites
Advanced Materials, 1999
The working principle of composite polymer vapor sensors is basically to exploit the vapor absorption properties of an insulating polymer whose electrical properties are modulated by a conductive "filler". Carbon black and graphite powder have already been used as "filler" materials [Sens. In this work we fabricate and characterize vapor sensors with a new type of "filler": carbon nanoparticles obtained by flame synthesis. Electrochemically prepared porous silicon with a 40% porosity has been used as the substrate for the carbon growth. Carbon nanoparticles have been characterized by AFM, SEM, FTIR; XRD, diffraction laser spectroscopy, nitrogen isothermal adsorption and visible optical micrography. The carbon structures seem composed of "units" whose size is in the range 5-20 nm. Composite thin films have been realized using mainly poly(methyl-methacrylate) (PMMA) as polymeric insulating matrix. Thin films of the composite are used to realize chemiresistor sensing devices. The characteristics of the sensors responses to volatile organic compounds (VOCs) are related to filler types in order to optimize the sensing device and show the importance of the filler characteristics.
The in-situ synthesis and characteristics of sulfonic acid group functionalized multi-walled carbon nanotubes incorporated poly(m-aminophenol) composite (PmAP/s-MWCNT) has been investigated. The fabricated nanocomposite film was successfully exploited as aliphatic alcohol vapor sensor material. The amount of s-MWCNT inside the PmAP matrix was optimized as about 2 wt% in terms of highest average conductivity achieved (3.2 3 10 À2 S/cm) for the composites due to induced site-selective interaction between the conjugated PmAP chain and s-MWCNT. The functionalization of MWCNT and the interfacial interaction in the nanocomposite was confirmed by spectro-scopic analysis. The morphological analysis of the nanocompo-site by Field emission scanning electron microscopy and transmission electron microscopy indicated the formation of PmAP layers (thickness ~ 200 nm) on the surfaces of s-MWCNTs. The nanocomposite sensor exhibited distinct features of the response curves and percent response values for different aliphatic alcohols especially for methanol and ethanol, which could be used as a basis for the selective detection of these pollutant vapors.
Ultra-Low-Power Alcohol Vapor Sensors Based on Multi-Walled Carbon Nanotube
2006 1st IEEE International Conference on Nano/Micro Engineered and Molecular Systems, 2006
We have demonstrated multi-walled carbon nanotube (MWCNTs) based sensors, which are capable of detecting alcohol vapor with ultra-low power. We fabricated the Si-substrate sensors using an AC electrophoretic technique so as to form bundled MWCNTs sensing elements between Au microelectrodes. The I-V measurement illustrates that we can activate the sensors at the Ohmic region of the sensors (at 10µA), which is without any overheat effect. The sensors only need an ultra-low power (~1µW) to detect the alcohol vapor. They exhibit fast, reversible and repeatable response. We have tested the response of the sensors with alcohol concentrations from 10ppth to 400ppth (ppth = parts per thousand). Our result shows that there is a linear relation between the resistance of the sensors and alcohol concentration. Also, we can easily reverse the sensor to the initial reference resistance by annealing them at 100-250µA current within 6 minutes. Moreover, the sensors are selective with respect to flow from air, water vapor, and alcohol vapor. Finally, we have also studied how the temperature of the sensors affects their response towards alcohol vapor. The result shows that the performance of the sensors will deteriorate as the temperature of the sensors increase. Also, the cooling effect of the vapor is not a dominating factor in determining the response of the sensor. Based on our experiments, we prove the feasibility of turning the MWCNTs sensors into a commercialized alcohol sensor with ultra-low power requirements.