Topic
Vapours
About: Vapours is a research topic. Over the lifetime, 1153 publications have been published within this topic receiving 15022 citations.
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TL;DR: The sensing layer of an inkjet-fabricated sensor based on copper oxide nanostructured particles on polymer flexible substrate for the sensing of alcohol vapours and humidity at room temperature showed the opposite resistance response to stimuli than expected.
Abstract: This work focuses on an inkjet-fabricated sensor based on copper oxide nanostructured particles on polymer flexible substrate for the sensing of alcohol vapours and humidity at room temperature. Nanoparticles were prepared by a microwave-assisted solvothermal sealed vessel synthesis method. The ink composition was developed on the basis of viscosity and surface tension optimization by the addition of polymeric steric surfactant and dispersant. The printing process was optimized with the help of non-dimensional criteria. Silver nanoink was used for the printing of an interdigitated pattern on a PET substrate which was overprinted by the copper oxide ink, thus obtaining a flexible flat sensor. Material design and all fabrication steps of the sensor respected the temperature limitation given by the thermal stability of the polymer substrate. Printed layers and motifs were characterized microscopically and by resistance measurement. The effectiveness of the prepared sensor was demonstrated and studied by measuring the response to saturated vapours at room temperature. The sensing layer showed the opposite resistance response to stimuli than expected for the well-known p-type sensing mechanism of CuO sensors operated at high temperatures. In addition to vapour sorption, condensation and desorption influencing electron, proton and ionic conductivity, manifestation of another mechanism was observed and an explanation suggested in terms of the electrochemical mechanism.
25 citations
25 citations
TL;DR: A prototype of a fast-response task-specific amperometric gas sensor based on paper-supported room-temperature ionic liquids (RTILs) is proposed here for improved analysis of volatile acid species, showing that the quite high potentials required for the detection of these analytes are lowered significantly, thanks to the addition of the basic acetate RTIL.
Abstract: A prototype of a fast-response task-specific amperometric gas sensor based on paper-supported room-temperature ionic liquids (RTILs) is proposed here for improved analysis of volatile acid species. It consists of a small filter paper foil soaked with a RTIL mixture containing an ionic liquid whose anion (acetate) displays a basic character, upon which three electrodes are screen printed by carbon ink profiting from a suitable mask. It takes advantage of the high electrical conductivity and negligible vapour pressure of RTILs and of their easy immobilization into a porous and inexpensive supporting material such as paper. The performance of this device, used as a wall-jet amperometric detector for flow injection analyses of headspace samples in equilibrium with aqueous solutions at controlled concentrations, was evaluated for phenol and 1-butanethiol vapours which were adopted as model acid gaseous analytes. The results obtained showed that the quite high potentials required for the detection of these analytes are lowered significantly, thanks to the addition of the basic acetate RTIL. In such a way, overlap with the medium discharge is avoided, and the possible adverse effect of interfering species is minimised. The sensor performance was quite satisfactory (detection limits, ca. 0.3 μM; dynamic range, ca. 1–200 μM, both referred to solution concentrations; correlation coefficients in the range 0.993–0.997; repeatability, ± 6 % RSD; long-term stability, 9 %); thus suggesting the possible use of this device for manifold applications.
24 citations
01 Jan 1994
TL;DR: Application of the biofilter model developed herein to this problem permitted explanation of the phenomenon and confirmed that biofilm concentration gradients are likely to occur during the removal of pollutant mixtures when microbial inhibition occurs.
Abstract: In the work reported here, selected .kinetic and operational aspects of the aerobic biotreatment of vapours of methyl ethyl ketone (MEK) and of methyl isobutyl ketone (MIBK) in compost-based biofilters have been investigated. Emphasis was placed on the characterization and on the development of conceptual explanations of the phenomena occurring during the removal of either single or mixtures of the two pollutants under both steady and transient state operating conditions. A dynamic mathematical model for a biofilter was developed. It proved appropriate for describing most of the experiments undertaken and served as a basis for comprehensive discussion of biofilter operation. Mixtures of MEK and MIBK vapours were shown to undergo simultaneous biodegradation that was probably mediated by the same microbial community. Neither diffusion nor oxygen limitation occurred and the process was controlled by the biological rates that could be achieved. Maximum elimination capacities decreased from 120 and 30 g nr3 h"1 for MEK and MIBK, respectively, in the case of single pollutants, to 40 and 18 g nr3 h_1, in the case of simultaneous removal of equal concentrations of vapours. Studies on pollutant concentration profiles in biofilters indicated high axial heterogeneity with respect to degradation rates. Application of the biofilter model developed herein to this problem permitted explanation of the phenomenon and confirmed that biofilm concentration gradients are likely to occur during the removal of pollutant mixtures when microbial inhibition occurs. Investigations of transient behaviour in biofilters exposed to perturbations emphasized the major role of sorption processes during transient state operation. Steady states were generally re-established within two to five hours after perturbations occurred. Pulses of pollutants in the waste air stream indicated that major inhibition occurred during short term exposure to gaseous concentrations above 10 g nr3 MEK, even though MIBK did not exhibit similar inhibitory effects at this concentration. Biodegradation of MEK and/or MIBK in shake flasks by suspended cultures inoculated from operating biofilters showed markedly different growth and biodegradation patterns. In the range of concentrations tested (1-20 mMol) in shake flask cultures, Monod kinetics with substrate inhibition successfully described growth on MEK or on MIBK, although no substrate inhibition occurred when cultures were grown on mixtures of MEK and MIBK.
24 citations
TL;DR: In this article, an extreme and reversible growth of electrical resistance as a response of polyisoprene-high structure carbon nanoparticle composites to tensile or compressive strain found in earlier studies is examined with the purpose to adapt the material as a highly sensitive sensor of organic solvents.
Abstract: An extreme and reversible growth of electrical resistance as a response of polyisoprene–high structure carbon nanoparticle composites (PHSCNC) to tensile or compressive strain found in earlier studies is examined with the purpose to adapt the material as a highly sensitive sensor of organic solvents. The change of the electrical resistance of PHSCNC studied during exposure to different organic solvent vapours is reported. The highest sensitivity is detected at concentrations of 9–11 mass parts of the nanoparticle filler corresponding to percolation region of the composite. The mechanism of vapour sensing is studied and the extremely high sensitivity (remarkable and rapid change of the resistance) is explained by tunnel current between adjacent carbon nanoparticles. The rate of the change of resistance is found to depend on the chemical composition of the molecules being absorbed by the polymer matrix.
24 citations