Highly sensitive benzene detection with metal oxide semiconductor gas sensors – an inter-laboratory comparison

For detection of benzene, a gas sensor system with metal oxide semiconductor (MOS) gas sensors using temperature-cycled operation (TCO) is presented. The system has been tested in two different laboratories at the concentration range from 0.5 up to 10 ppb. The system is equipped with three gas sensors and advanced temperature control and read-out electronics for the extraction of features from the TCO signals. A sensor model is used to describe the sensor response in dependence on the gas concentration. It is based on a linear differential surface reduction (DSR) at a low temperature phase, which is linked to an exponential growth of the sensor conductance. To compensate for cross interference to other gases, the DSR is measured at three different temperatures (200, 250, 300 °C) and the calculated features are put into a multilinear regression (partial least square regression – PLSR) for the quantification of benzene at both laboratories. In the tests with the first set-up, benzene was supplied in defined gas profiles in a continuous gas flow with variation of humidity and various interferents, e.g. toluene and carbon monoxide (CO). Depending on the gas background and interferents, the quantification accuracy is between ±0.2 and ±2 ppb. The second gas mixing system is based on a circulation of the carrier gas stream in a closed-loop control for the benzene concentration and other test gases based on continuously available reference measurements for benzene and other organic and inorganic compounds. In this system, a similar accuracy was achieved for low background contaminations and constant humidity; the benzene level could be quantified with an error of less than 0.5 ppb. The transfer of regression models for one laboratory to the other has been tested successfully

Low-Cost Air Quality Monitoring Tools: From Research to Practice (A Workshop Summary)

In May 2017, a two-day workshop was held in Los Angeles (California, U.S.A.) to gather practitioners who work with low-cost sensors used to make air quality measurements. The community of practice included individuals from academia, industry, non-profit groups, community-based organizations, and regulatory agencies. The group gathered to share knowledge developed from a variety of pilot projects in hopes of advancing the collective knowledge about how best to use low-cost air quality sensors. Panel discussion topics included: (1) best practices for deployment and calibration of low-cost sensor systems, (2) data standardization efforts and database design, (3) advances in sensor calibration, data management, and data analysis and visualization, and (4) lessons learned from research/community partnerships to encourage purposeful use of sensors and create change/action. Panel discussions summarized knowledge advances and project successes while also highlighting the questions, unresolved issues, and technological limitations that still remain within the low-cost air quality sensor arena

Comparison of InP Schottky diodes based on Au or Pd sensing electrodes for NO2 and O3 sensing

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An innovative gas sensor system designed from a sensitive organic semiconductor downstream a nanocarbonaceous chemical filter for the selective detection of NO2 in an environmental context

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First French Intercomparison Exercises for Air Quality sensors (EAμC) : results and assessment

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Elaboration of SWNTs-based gas sensors using dispersion techniques: Evaluating the role of the surfactant and its influence on the sensor response

International audienceThis paper describes the preparation of the CNTs-based gas sensors, which are achieved by the utilisation of aqueous dispersions of carbon nanotubes (CNTs) using NaDDBS as a surfactant. The sensors are made of IDEs (Interdigitated electrodes) on which the CNTs dispersion are dropcast deposited. The sensing layers are characterized by Raman and IR spectroscopy as well as SEM analysis and electrical characterization (I-V). Finally, the sensor response and relative resistance change (ΔR/R) versus concentration under low NO2 gas concentrations are reported. The sensor performance is evaluated by focusing on the influence of the surfactant and the annealing process on the final sensor. The effect of the surfactant has been investigated in order to establish the optimal conditions for the realization of the sensors using dispersion route. Although the use of surfactant provides stable dispersions, the annealing treatment of the sensor before sensing experiments need to be correctly tuned for good sensor performance. Indeed, even if the presence of surfactant does not drastically hinder the sensor response, a major problem comes from its residue after decomposition under certain annealing conditions (≥300 °C). In fact the surfactant residue seems to obstruct active sites on the sensor surface and therefore render the sensor unusable. Lower annealing conditions (≤150 °C) seem to be the optimum

An innovative gas sensor system designed from a sensitive organic semiconductor downstream a nanocarbonaceous chemical filter for selective detection of NO2 in an environmental context. Part II: Interpretations of O3/nanocarbons and NO2/nanocarbons interactions

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Improved selectivity towards NO2 of phthalocyanine-based chemosensors by means of original indigo/nanocarbons hybrid material

International audienceA new and original gas sensor-system dedicated to the selective monitoring of nitrogen dioxide in air and in the presence of ozone, has been successfully achieved. Because of its high sensitivity and its partial selectivity towards oxidizing pollutants (nitrogen dioxide and ozone), copper phthalocyanine-based chemoresistors are relevant. The selectivity towards nitrogen dioxide results from the implementation of a high efficient and selective ozone filter upstream the sensing device. Thus, a powdered indigo/nanocarbons hybrid material has been developed and investigated for such an application. If nanocarbonaceous material acts as a highly permeable matrix with a high specific surface area, immobilized indigo nanoparticles are involved into an ozonolysis reaction with ozone leading to the selective removal of this analytes from air sample. The filtering yields towards each gas have been experimentally quantified and establish the complete removal of ozone while having the concentration of nitrogen dioxide unchanged. Long-term gas exposures reveal the higher durability of hybrid material as compared to nanocarbons and indigo separately. Synthesis, characterizations by many complementary techniques and tests of hybrid filters are detailed. Results on sensor-system including CuPc-based chemoresistors and indigo/carbon nanotubes hybrid material as in-line filter are illustrated. Sensing performances will be especially discussed