The sensing properties of carbon nanotube filled copolymers for VOC vapors detection

Nowadays, carbon nanotubes are a widely available material, especially multiwall carbon nanotubes. In addition to many other applications, they find use in all kinds of sensors, like deformation, motion, tensile and pressure responsive elements. Numerous applications in sensors for volatile organic compounds (VOCs) are reported as well, nevertheless, they mainly suffer from low selectivity. Therefore, in this research, a sensor containing MWCNTs dispersed in a functional polymer matrix was prepared. As a polymer matrix, styreneisoprene- styrene elastomer was chosen. The standard sensing mechanism of entangled MWCNTs is based on the quality of the contacts (charge transfer) between the individual nanotubes. In the prepared nanocomposite, the mechanism is modified due to the presence of the otherwise non-conductive matrix. The changes of conductivity depend on the response of the percolating nanotube filler network to the swelling of the polymer matrix due to adsorption of VOCs. The tested gas substances have high values of diffusion coefficient for the polymer, so they have a quick response. Then, the selectivity is ensured by differences in solubility of the tested VOCs in the polymer. The effect was demonstrated for four VOCs differing by their affinity to the polymer matrix, namely, heptane, toluene, acetone, and ethanol. © 2021 TANGER Ltd., Ostrava.Internal Grant Agency of the Tomas Bata University in Zlin [IGA/CPS/2019/007]; project CPS-strengthening research capacity [CZ.1.05/2.1.00/19.0409]; Ministry of Education, Youth and Sports of the Czech Republic -DKRVO [RP/CPS/2020/006]RP/CPS/2020/006; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Univerzita Tomáše Bati ve Zlíně: CZ.1.05/2.1.00/19.0409, IGA/CPS/2019/00

Microstrip resonant sensor for differentiation of components in vapor mixtures

A novel microstrip resonant vapor sensor made from a conductive multiwalled carbon nanotubes/ethylene-octene copolymer composite, of which its sensing properties were distinctively altered by vapor polarity, was developed for the detection of organic vapors. The alteration resulted from the modified composite electronic impedance due to the penetration of the vapors into the copolymer matrix, which subsequently swelled, increased the distances between the carbon nanotubes, and disrupted the conducting paths. This in turn modified the reflection coefficient frequency spectra. Since both the spectra and magnitudes of the reflection coefficients at the resonant frequencies of tested vapors were distinct, a combination of these parameters was used to identify the occurrence of a particular vapor or to differentiate components of vapor mixtures. Thus, one multivariate MWCNT/copolymer microstrip resonant sensor superseded an array of selective sensors. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Ministry of Education, Youth and Sports of the Czech Republic-DKRVO [RP/CPS/2020/006]; National Budget of the Czech Republic: the project CPSV-Strengthening Research Capacity [CZ.1.05/2.1.00/19.0409]; Czech Academy of Sciences, Czech Republic [RVO:67985874]RP/CPS/2020/006; CZ.1.05/2.1.00/19.0409; Akademie Věd České Republiky, AV Č

Giant response and selectivity of Hansen solubility parameters-based graphene-SBS co-polymer matrix composite room temperature sensor to organic vapours

A styrene-butadiene-styrene co-polymer matrix nanocomposite filled with graphene nanoplatelets was studied to prepare chemiresistive volatile organic compounds (VOCs) room temperature sensors with considerable response and selectivity. Nanofiller concentration was estimated from the electrical conductivity percolation behaviour of the nanocomposite. Fabricated sensors provided selective relative responses to representative VOCs differing by orders of magnitude. Maximum observed average relative responses upon exposure to saturated vapours of the tested VOCs were ca. 23% for ethanol, 1600% for acetone, and the giant values were 9 × 106% for n-heptane and 10 × 106% for toluene. The insensitivity of the sensor to the direct saturated water vapour exposure was verified. Although high humidity decreases the sensor’s response, it paradoxically enhances the resolution between hydrocarbons and polar organics. The non-trivial sensing mechanism is explained using the Hansen solubility parameters (HSP), enabling a rational design of new sensors; thus, the HSP-based class of sensors is outlined.DKRVO, (RP/CPS/2022/007); Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Univerzita Tomáše Bati ve Zlíně, UTB, (IGA/CPS/2022/002, IGA/CPS/2023/006)Ministry of Education, Youth, and Sports of the Czech Republic-DKRVO [RP/CPS/2022/007]; Tomas Bata University in Zlin [IGA/CPS/2022/002, IGA/CPS/2023/006

Detection of NH3 gas using CrVO4 nanoparticles

Nanostructured chromium orthovanadate with an average particle size of 65 nm was prepared by the co-precipitation technique for the chemiresistive sensor. The morphology and particle size distribution of CrVO4 nanoparticles were examined by SEM and TEM. According to XRD, most of the prepared CrVO4 material (crystallites) has a monoclinic structure belonging to the space group C2/m. XPS and UV-Vis absorbance measurements provided additional information on the main phase and the surface. The material has shown reasonable selectivity towards the NH3 gas. The as-prepared CrVO4 nanostructures exhibit a maximum relative response of 32% to 50 ppm NH3. The identical dynamic response profiles during the sequential injections of 50 ppm NH3 evinced the repeatability of the sensor. The limit of detection (LOD) value of the sensor was estimated ca 0.7 ppm using relative response values towards a wide range of NH3 concentrations from 10 ppm to 100 ppm. The sensing mechanism was expressed in terms of the surface band bending phenomenon caused by the adsorption and desorption of the ammonia. The best sensor performance was achieved at 330 °C, where the effects of humidity and moisture can be neglected. The results confirmed that the CrVO4 nanomaterial has the potential to fabricate an affordable, easy-to-make, and reliable gas sensor for NH3 gas.DKRVO, (RP/CPS/2022/007); European Union´s Horizon 2020 research and innovation programme, (739566); Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Istanbul Üniversitesi, (FYL-2021-38266); Agentúra na Podporu Výskumu a Vývoja, APVV; Vedecká Grantová Agentúra MŠVVaŠ SR a SAV, VEGA, (1/0844/21); Universität zu Köln, UoC; Univerzita Tomáše Bati ve Zlíně, UTB, (IGA/CPS/2022/002, IGA/CPS/2023/006)Ministry of Education, Youth and Sports of the Czech Republic - DKRVO [RP/CPS/2022/007]; European Union's Horizon 2020 research and innovation programme [739566]; Internal grant agency of Tomas Bata University in Zlin [IGA/CPS/2022/002, IGA/CPS/2023/006]; Scientific Research Projects Coordination Unit of Istanbul University [FYL-2021-38266]; Slovak Research and Development Agency [VEGA 1/0844/21]; University of Cologn

Microstrip Resonant Sensor for Differentiation of Components in Vapor Mixtures

A novel microstrip resonant vapor sensor made from a conductive multiwalled carbon nanotubes/ethylene-octene copolymer composite, of which its sensing properties were distinctively altered by vapor polarity, was developed for the detection of organic vapors. The alteration resulted from the modified composite electronic impedance due to the penetration of the vapors into the copolymer matrix, which subsequently swelled, increased the distances between the carbon nanotubes, and disrupted the conducting paths. This in turn modified the reflection coefficient frequency spectra. Since both the spectra and magnitudes of the reflection coefficients at the resonant frequencies of tested vapors were distinct, a combination of these parameters was used to identify the occurrence of a particular vapor or to differentiate components of vapor mixtures. Thus, one multivariate MWCNT/copolymer microstrip resonant sensor superseded an array of selective sensors