Highly enhanced vapor sensing of multiwalled carbon nanotube network sensors by n-butylamine functionalization

The sensing of volatile organic compounds by multiwall carbon nanotube networks of randomly entangled pristine nanotubes or the nanotubes functionalized by n-butylamine, which were deposited on polyurethane supporting electrospinned nonwoven membrane, has been investigated. The results show that the sensing of volatile organic compounds by functionalized nanotubes considerably increases with respect to pristine nanotubes. The increase is highly dependent on used vapor polarity. For the case of highly polar methanol, the functionalized MWCNT network exhibits even more than eightfold higher sensitivity in comparison to the network prepared from pristine nanotubes.internal Grant of TBU in Zlin - resources of the Specific University Research [IGA/FT/2014/013]; operational program Research and Development for Innovations - European Regional Development Fund (ERDF); National Budget of the Czech Republic within the framework of the Centre of Polymer Systems project [CZ.1.05/2.1.00/03.0111]; Ministry of Education, Youth and Sports of the Czech Republic within the framework of the Czech-Argentina [7AMB13AR019]; Slovenian Research Agency (ARRS

Comparison of vapor sensing properties of pristine and hexamethylene diamine-treated MWCNT networks to primary, secondary and tertiary alcohols

The sensing properties of pristine and hexamethylene diamine (HDA)-treated multiwall carbon nanotube networks (MWCNT-Ns) to selected primary, secondary (sec-) and tertiary (ter-) alcohols were examined by resistance measurements. It was seen that sensor responses, S (%), of MWCNT (HDA)-N to these alcohols were much higher than those of the pristine network. An increase in the S (%) values per mm Hg of both networks was observed from propanol to butanol, when their values from primary alcohols to sec-/tert-ones decreased due to the change in the interaction area of these alcohols with the MWCNT-Ns. © (2014) Trans Tech Publications

Enhanced strain-dependent electrical resistance of polyurethane composites with embedded oxidized multiwalled carbon nanotube networks

The effect of different chemical oxidation of multiwalled carbon nanotubes with H2O2, HNO3, and KMnO4 on the change of electrical resistance of polyurethane composites with embedded oxidized nanotube networks subjected to elongation and bending has been studied. The testing has shown sixteen-fold increase in the electrical resistance for the composite prepared from KMnO4 oxidized nanotubes in comparison to the composites prepared from the pristine and other oxidized nanotubes. The evaluated sensitivity of KMnO4 treated composite in terms of the gauge factor increases with strain to nearly 175 at the strain 11%. This is a substantial increase, which ranks the composite prepared from KMnO4 oxidized nanotubes among materials as strain gauges with the highest electromechanical sensitivity. The observed differences in electromechanical properties of the composites are discussed on basis of their structure which is examined by the measurements of Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscope. The possible practical use of the composites is demonstrated by monitoring of elbow joint flexion during two different physical exercises. © 2013 R. Benlikaya et al

The enhanced alcohol sensing response of multiwalled carbon nanotube networks induced by alkyl diamine treatment

The vapor sensing properties of multiwalled carbon nanotube networks (MWCNT-Ns) of randomly entangled pristine nanotubes and the nanotubes treated by KMnO4-H2SO4, ethylenediamine and hexamethylenediamine deposited on polyurethane supporting non-woven membrane to vapors of linear alcohols (methanol, ethanol, propan-1-ol, butan-1-ol and pentan-1-ol) are measured by monitoring of electrical resistance of the networks. The substantial increase is observed in the sensor response of the networks to vapors of the alcohols induced by the alkyl diamine treatments of nanotubes in comparison with those of pristine and the KMnO4 treated MWCNT-Ns. Analysis of the enhanced linear alcohol sensing properties of the MWCNT-Ns is concentrated on the interactions between the network and the alcohols and the amount of adsorbed alcohols on the networks by using the Fourier transform infrared (FTIR) spectroscopy analysis and the gravimetric measurements. The scanning electron microscopy, Brunauer-Emmett-Teller surface area and thermal gravimetric analyses are used for the characterization of the networks as well as FTIR. The result shows that the enhanced vapor sensor response can be attributed to the extent of the interaction area between the carbon nanotubes and the alcohols. © 2014 Elsevier B.V

Effect of crack formation under elongation in carbon nanotube networks embedded in polyurethane

A highly deformable composite composed of a network of electrically- conductive entangled carbon nanotubes embedded in elastic polyurethane for sensing tensile deformation by changes in strain has been prepared. The testing has shown that the composite can be extended as by much as 400 % during which the electrical resistance increases more than 270 times. The high strain sensing can be attributed to the network cracking upon extension. To understand the cracking mechanism and explain the resistance change, the structural changes of networks made of pristine carbon nanotubes (as well as functionalized multi-walled) were examined. The microscopic observation of crack formation and resistance change of the networks correlates well with the amount of cracking. © (2014) Trans Tech Publications

Breathable and polyol based hydrogel food packaging

Packaging of fresh fruits and vegetables is an important issue to preserve their shelf-life and quality and to protect them from early spoilage. Polymeric materials are predominantly used for fruit and vegetable packaging where bioplastics are more concerned for practical as well as an environmental friendly protection point of If the packaging materials polyol or biobased polymers, that are able to breath, can help to solve these problems. In this study, the breathability of PVP-CMC based hydrogel food packaging was examined in respect of suitability of the package in the preservation of quality and self-life of "table grapes" by monitoring the changes in the resistances of modified MWCNT sensors. The MWCNT sensors were prepared by polyvinyl alcohol (humidity measurement) and hexamethylenediamine (ethanol vapor measurement) and placed them inside and/or outside of the package for three weeks. The results obtained from the measurements of the PVP-CMC based hydrogel food package were compared with those of a traditional food package. In addition, before and after the packages were investigated by Fourier Transform Infrared Spectroscopy, hermogravimetric Analysis and Atomic Force Microscopy Analysis to confirm the changes in morphology and physico-chemical properties of the packaging materials. It has been noticed that the PVP-CMC package is more breathable compared to traditional one. It has also been observed that during the period of experiment the absorption and diffusion of water vapor occurred only in the case of the hydrogel based PVP-CMC food package, thus the "table grapes" remained as good as fresh after three weeks. No ethanol formation/fermentation process has been started during 3 weeks at room temperature. Copyright © 2015 American Scientific Publishers.Operational Program Education for Competitiveness; European Social Fund (ESF); national budget of Czech Republic [CZ.1.07/2.3.00/20.0104, CZ.1.05/2.1.00/03.0111]; Operational Program Research and Development for Innovation

Analysis of sensing properties of thermoelectric vapor sensor made of carbon nanotubes/ethylene-octene copolymer composites

We designed a novel self-powered thermoelectric vapor sensor, whose thermogenerated voltage was modulated by chemical vapors. The sensor was made of composites of oxidized multi-walled carbon nanotubes within ethylene-octene copolymer. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy of the multi-walled carbon nanotubes within ethylene-octene copolymer showed that the oxidation with HNO3 or KMnO4 enhanced its p-type electrical conductivity and that the thermoelectric power increase was proportional to the formation of new oxygen-containing functional groups on the surface of carbon nanotubes. When this composite was subjected to a saturated vapor of either heptane (aliphatic hydrocarbon), toluene (aromatic hydrocarbon) or ethanol (alcohol), its respective relative resistance increased in average by 3.6, 1.1 and 0.05. Consequently, the magnitude of voltage generated by the thermoelectric device containing the oxidized multi-walled carbon nanotubes within ethylene-octene copolymer determined the absence or presence of the aforementioned chemical vapors. © 2016 Elsevier LtdMŠMT, Ministry of Education, Youth and SportsMinistry of Education, Youth and Sports of the Czech Republic - Program NPU I [LO1504]; Fund of the Institute of Hydrodynamics [AV0Z20600510

Can a wearable strain sensor based on a carbon nanotube network be an alternative to an isokinetic dynamometer for the measurement of knee-extensor muscle strength?

This study aimed to find out whether a wearable strain sensor including thermoplastic polyurethane composite with a multi-walled carbon nanotube network could be a viable alternative to an isokinetic dynamometer for the measurement of knee-extensor muscle strength. For the first time, the voltage-torque and angle-time relations of the sensor were determined to allow a comparison between the angle-dependent torque changes of the dynamometer and the sensor. This comparison suggested that the torque-angle relations of the dynamometer and the sensor did not have the same characteristics. In this regard, the sensor may be used in the torque measurements due to the moderate correlation between the torque values determined via the isokinetic dynamometer and the sensor and due to the significant difference between low and high torque values of the sensor. By the same token, the torque-angle graph of the sensor may be more informative than that of the dynamometer in evaluation of knee problems. © 2017 IOP Publishing Ltd.Balikesir University [2014/25