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Ammonia is an atmospheric pollutant precursor of inorganic fine particles (sulphate and ammonium nitrate particles) that are particularly harmful to human health. Ammonia and particulate matter (PM) are responsible for severe pollution outbreaks over Europe (LCSQA, LCSQA 2019), during springtime of 2012 (Kutzner et al., 2021), 2014 (Fortems-Cheiney et al., 2016), 2015 (Petit et al., 2017), 2016 (Tournadre et al., 2020: Viatte et al., 2020) and 2020 (Viatte et al., 2021). Despite this major societal and scientific interest, there is a crucial lack of routine ammonia and aerosol speciation observations. One of the scientific reasons comes from the difficulty to measure atmospheric ammonia due to its sticky, volatile, and reactive nature (von Bobrutzki et al., 2010).The objective of the Multi-Instrumental Analysis of Ammonia Concentrations (AMICA) project is to compare the response of different available systems for measuring atmospheric ammonia at a rural site in the Île-de-France region. The 14 instruments based on different NH3 measurement techniques are compared over a wide range of ammonia concentrations from ambient atmospheric to boosted concentrations (10 to 600 ppbv) using an innovative 400 m2 ammonia emission system. They are all synchronized with a cross-correlation function based on the median value. At elevated concentrations all inlet-based instruments sampling to the same manifold performed very well on precision, even at high temporal resolution monitoring (1 min) that highlights a great progress for current in situ NH3 analysers. By comparing with the data from a mini Differential Optical Absorption Spectrometer (miniDOAS) and a sequential acid trap-IC (ROSAA), we demonstrated that inlet design perturbs the response time of the instruments connected to the manifold, which was already mentioned in literature. This measurement campaign is part of a series of ammonia projects that have recently taken place in France.ReferencesFortems-Cheiney, A., et al., Geophys. Res. Lett., 43, 5475–5482, https://doi.org/10.1002/2016GL069361, 2016.Kutzner, R. D., et al., Atmos. Chem. Phys., 21, 12091–12111, https://doi.org/10.5194/acp-21-12091-2021, 2021.LCSQA, Le Laboratoire Central de Surveillance de la Qualité de l'Air, Bilan des travaux 2018-2019 du programme CARA, Ref. INERIS : DRC-19-181155-02828A, 2019.Petit, J.-E. , et al., T, Atmospheric Environment, Volume 155, 2017, Pages 68-84, ISSN 1352-2310, https://doi.org/10.1016/j.atmosenv.2017.02.012.Tournadre, B., et al., Atmos. Meas. Tech., 13, 3923–3937, https://doi.org/10.5194/amt-13-3923-2020, 2020.Viatte, C., et al., Atmos. Chem. Phys., 20, 577–596, https://doi.org/10.5194/acp-20-577-2020, 2020.Viatte C., et al., Atmosphere, 2021, 12, 160, https://doi.org/10.3390/atmos12020160.von Bobrutzki, et al., Atmos. Meas. Tech., 3, 91–112, https://doi.org/10.5194/amt-3-91-2010, 2010.

Ammonia (NH3) in the atmosphere affects both the environment and human health. It is therefore increasingly recognised by policy makers as an important air pollutant that needs to be mitigated, though it still remains unregulated in many countries. In order to understand the effectiveness of abatement strategies, routine NH3 monitoring is required. Current reference protocols, first developed in the 1990s, use daily samplers with offline analysis; however, there have been a number of technologies developed since, which may be applicable for high time resolution routine monitoring of NH3 at ambient concentrations. The following study is a comprehensive field intercomparison held over an intensively managed grassland in southeastern Scotland using currently available methods that are reported to be suitable for routine monitoring of ambient NH3. In total, 13 instruments took part in the field study, including commercially available technologies, research prototype instruments, and legacy instruments. Assessments of the instruments' precision at low concentrations (< 10 ppb) and at elevated concentrations (maximum reported concentration of 282 ppb) were undertaken. At elevated concentrations, all instruments performed well and with precision (r2 > 0.75). At concentrations below 10 ppb, however, precision decreased, and instruments fell into two distinct groups, with duplicate instruments split across the two groups. It was found that duplicate instruments performed differently as a result of differences in instrument setup, inlet design, and operation of the instrument. New metrological standards were used to evaluate the accuracy in determining absolute concentrations in the field. A calibration-free CRDS optical gas standard (OGS, PTB, DE) served as an instrumental reference standard, and instrument operation was assessed against metrological calibration gases from (i) a permeation system (ReGaS1, METAS, CH) and (ii) primary standard gas mixtures (PSMs) prepared by gravimetry (NPL, UK). This study suggests that, although the OGS gives good performance with respect to sensitivity and linearity against the reference gas standards, this in itself is not enough for the OGS to be a field reference standard, because in field applications, a closed path spectrometer has limitations due to losses to surfaces in sampling NH3, which are not currently taken into account by the OGS. Overall, the instruments compared with the metrological standards performed well, but not every instrument could be compared to the reference gas standards due to incompatible inlet designs and limitations in the gas flow rates of the standards. This work provides evidence that, although NH3 instrumentation have greatly progressed in measurement precision, there is still further work required to quantify the accuracy of these systems under field conditions. It is the recommendation of this study that the use of instruments for routine monitoring of NH3 needs to be set out in standard operating protocols for inlet setup, calibration, and routine maintenance in order for datasets to be comparable.

Ammonia (NH3) in the atmosphere affects both the environment and human health. It is therefore increasingly recognised by policy makers as an important air pollutant that needs to be mitigated. In order to understand the effectiveness of abatement strategies, routine NH3 monitoring is required. Current reference protocols, developed in the 1990s, use daily samplers with offline analysis but there have been a number of technologies developed since, which may be applicable for high time resolution routine monitoring of NH3 at ambient concentrations. The following study is a comprehensive field intercomparison held over an intensively managed grassland in South East Scotland using currently available methods that are reported to be suitable for routine monitoring of ambient NH3. In total 13 instruments took part in the field study. The instruments include: an online ion chromatography system (MARGA, Metrohm-Applikon,NL), two wet chemistry continuous flow analysis systems (AiRRmonia, Mechatronics, NL), a photoacoustic spectrometer (NH3 monitor, LSE, NL), two mini Differential Optical Absorption Spectrometers (miniDOAS; NTB Interstate University of Applied Sciences Buchs, now part of "Eastern Switzerland University of Applied Sciences, CH and RIVM, NL), as well as seven spectrometers using cavity enhanced techniques: a Quantum Cascade Laser Absorption Spectrometer (QCLAS, Aerodyne, Inc. US), Picarro G2103 Analyzer (Picarro US), Economical NH3 Analyser (Los Gatos Research, US), Tiger-i 2000 (Tiger Optics, US) and LaserCEM® gas analyser (AP2E, FR). Assessments of the instruments’ precision at low concentrations (< 10 ppb) and at elevated concentrations (maximum reported concentration of 282 ppb) were undertaken. At elevated concentrations all instruments performed well on precision (r2 > 0.75). At concentrations below 10 ppb however, instruments fell into two distinct groups and the duplicate instruments, miniDOAS, AiRRmonia, LGR and Picarro were split across the two groups. It was found that identical instruments performed differently at low concentrations, highlighting the impact of the setup, inlet design and operation of the instrument used. Accuracy in determining absolute concentrations in the field was assessed using a calibration-free CRDS Optical Gas Standard (OGS, PTB, DE), serving as an instrumental reference standard. Accuracy was also assessed using well established metrological standards for calibration gases, i) a permeation system (ReGaS1, METAS, CH) and ii) Primary Standard gas Mixtures (PSMs) prepared by gravimetry (NPL, UK). This study showed that though the OGS good performance with respect to sensitivity and linearity with reference gas standards, this in itself is not enough for the OGS to be a field reference standard because a closed path spectrometer has limitations due to losses to surfaces in sampling NH3, which need to be taken into account. Overall, the instruments studied performed well against the standard gases but we note that not every instrument could be calibrated using gas standards due to incompatible inlet designs and limitations in the gas flow rates of the standards. This work provides evidence that though NH3 instrumentation have greatly progressed in measurement precision, there is still further work required to quantify the accuracy of these systems under field conditions. It is the recommendation of this study that the use of instruments for routine monitoring of NH3 needs to be set out in standard operating protocols for inlet set-up, calibration and routine maintenance, in order for datasets to be comparable.

Hybrid composites based on tin chloride and the conductive polymers, polyaniline (PAni) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), were integrated into high-performance hydrogen sulphide (H2S) gas sensors working at room temperature. The morphology and chemical properties were studied by scanning and transmission electron microscopy (SEM, TEM), energy dispersive spectroscopy (EDS) and Fourier-transform infrared (FTIR). The composites demonstrated a slightly porous nanostructure and strong interactions between the polymers and the metal salt, which slightly dopes PAni. The hybrid sensors exhibited a very low detection limit (&lt, 85 ppb), fast response, repeatability, reproducibility and stability over one month. Moreover, this work presents how calibration based on the derivative of the signal can give hybrid sensors the ability to quantify the concentration of targeted gas, even during continuous variation of the analyte concentration. Finally, the effect of interfering species, such as water and ammonia, is discussed.

International audience; Coming from natural and anthropogenic sources, hydrogen sulfide gas (H2S) is a smelly hazardous substance at the sub-ppm level, which can lead to poisoning deaths at higher concentrations. New sensors with high metrological properties (detection limit lower than 1 ppm) and good stability are still needed to monitor and control the risk associated with this gas. The properties of a high-performance hydrogen sulfide gas sensor based on tin oxide and conductive polymers (polyaniline and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) are investigated. The principle of detection of this resistive sensor consists of a two steps reaction. H2S reacts with tin oxide producing hydrochloride acid, which dopes polyaniline, leading to the increase of its conductivity. Those systems present high repeatability and reproducibility, with sensitivities around 10%/ppm and a limit of detection close to 30 ppb. Moreover, the effect of interfering species such as humidity and oxidative gases (ammonia) is addressed. Those species have a limited impact, corrigible by data treatment. Finally, the sensors present an increase of sensitivity with time, apparently due to the modification of the interface between the electrodes and the sensitive materials.

Polyaniline (PANI) is a conducting polymer, widely used in gas-sensing applications. Due to its classification as a semiconductor, PANI is also used to detect reducing ammonia gas (NH3), which is a well-known and studied topic. However, easier, cheaper and more straightforward procedures for sensor fabrication are still the subject of much research. In the presented work, we describe a novel, more controllable, synthesis approach to creating NH3 PANI-based receptor elements. The PANI was electrochemically deposited via cyclic voltammetry (CV) on screen-printed electrodes (SPEs). The morphology, composition and surface of the deposited PANI layer on the Au electrode were characterised with electron microscopy, Fourier-transform infrared spectroscopy and profilometry. Prior to the gas-chamber measurement, the SPE was suitably modified by Au sputtering the individual connections between the three-electrode system, thus showing a feasible way of converting a conventional three-electrode electrochemical SPE system into a two-electrode NH3-gas detecting system. The feasibility of the gas measurements&rsquo, characterisation was improved using the gas analyser. The gas-sensing ability of the PANI-Au-SPE was studied in the range 32&ndash, 1100 ppb of NH3, and the sensor performed well in terms of repeatability, reproducibility and sensitivity.

International audience; Estimating agriculture’s contribution to air pollution and global warming is needed to understand and limit its impacts on the environment and climate. It is equally important to estimate the capacity of agricultural practices to mitigate these emissions and to characterize atmospheric deposition and the impacts of air pollutants on agroecosystems. This chapter presents methods for measuring air pollutant concentrations, their fluxes at the soil-vegetation-atmosphere interface, and emissions from livestock facilities. Methods for measuring air concentrations are described with a focus on compounds emitted from or impacting agriculture (including forests): ammonia, nitrogen oxides, pesticides, volatile organic compounds including methane, abiotic and biotic particles, and ozone. The main methods for measuring emission and deposition fluxes of air pollutants between terrestrial surfaces, especially agroecosystems, and the atmosphere are described with a specific focus on the eddy covariance method as well as on emissions from livestock buildings. Then the general principles of source apportionment methods for estimating emissions spatial variability are presented. To address the questions on atmospheric chemistry, the methods used for measuring the reactivity of atmospheric compounds are presented. Finally, an insight is given on the developments of measurement methodologies to address new compounds and improve the sensors’ sensitivity and response time as well as provide estimates of spatial variability of concentrations and fluxes at larger scales.

This work aims at evaluating the applicability of photocatalytic oxidation (PCO) for industrial emission treatment. A dedicated single-pass semi-industrial PCO reactor is designed and the PCO removal of isopropanol (IPA) is investigated under industrial conditions: (i) high IPA concentrations ranging from 1.8 to 14.6 ppm and (ii) high air flow rates ranging from 26 to 146 m3.h−1. The concentrations of upstream and downstream IPA and by-products are monitored, not only using analytical instruments (mass spectrometry), but also gas micro-sensors. This approach aims at assessing the aptitude of commercially available micro-sensors to monitor a semi-industrial PCO reactor, and estimating their ability to automate such a process for industry. First, the influence of the main process parameters has been addressed: (i) IPA concentration, (ii) total air flow rate, (iii) number of PCO stages and (iv) number of PCO media. Irrespectively of the process condition, IPA PCO does not lead to deactivation of the media; whereas IPA mineralization and side-products formation are directly impacted by the process parameters. The increase of IPA concentration and air flow rate inhibits IPA mineralization, while the increase of number of stages and media promotes IPA mineralization. It is evidenced that selected gas micro-sensors can provide a semi-quantitative monitoring of the process performances. The main limitations of sensors are (i) their resolution regarding the detection of concentration variations and (ii) their cross-sensitivity to various classes of VOCs. Nevertheless, some sensors could be relevant for the automation and control of the PCO process once a preliminary metrological validation with relevant analytical devices is performed. © 2018 Elsevier B.V.

Indoor air quality (IAQ) receives an increasing attention because of long-term occupancy of confined environments with high specific pollutant concentrations, especially volatile organic compounds, inducing a risk for human health. Standard air quality instruments are not adapted for long-term continuous real-time monitoring of these environments, and a promising alternative resides in using electronic gas sensors, which are miniature and low-cost devices capable to detect air pollutants, even at low concentrations. The present study focuses on IAQ monitoring with electronic gas multi sensor systems, as well as with typical indoor air analyzers in a 40 m 3 experimental room. The suitability of electronic gas sensors to monitor pollution events in indoor environments, characterized by transient concentrations of VOCs, has been characterized by simultaneous injections of acetaldehyde, acetone, formaldehyde, toluene and o -xylene. The impact of a green wall structure in the room has been assessed by the reduction of residual pollutant and higher decay of injected oxygenated VOCs than in the empty room. It has been shown that electronic gas sensor response show a good correlation within the analyzer measurements, both for injected VOC concentrations and their decay. Indeed, these systems provide relevant information for air treatment control system and detection of indoor air quality events, in the case of simple gas matrixes, however realistic complex matrixes are poorly monitored by electronic gas sensors selected in this study. This limitation could be overcome by increasing the number of sensitive sensors to indoor air specific composition.

International audience; L’Observatoire de la Qualité de l’Air Intérieur (OQAI) prépare actuellement une deuxième campagne nationale de connaissance de la qualité de l’air dans les logements, après celle menée en 2003-2005. Pour cette nouvelle campagne, l’OQAI souhaite, en marge des techniques de mesure plus traditionnelles, suivre en continu différents indicateurs de qualité de l’air dans plusieurs centaines de logements représentatifs du parc de résidences principales sur une durée d’une semaine à quelques mois au moyen de capteurs portables, peu bruyants, sensibles, spécifiques, fiables, et le moins coûteux possible. A cet égard, l’OQAI a mis en place un groupe de travail multidisciplinaire sur cette thématique afin d’identifier les technologies à même de répondre aux besoins de cette campagne, d’identifier les critères à la fois techniques, de contraintes sur le terrain et de communications à prendre en compte pour un déploiement dans les logements, d’étudier la possibilité d’une mise en œuvre par les occupants eux-mêmes et d’identifier les opportunités offertes par l’acquisition de ces données. L’état des réflexions en cours est partagé ici.

International audience

Kidney failure is a serious chronic disease, defined as the irreversible loss of kidney function. This disease is clinically silent to a very advanced stage. Thus, only a screening procedure can diagnose its pathology early enough to slow its progression. Due to the known fact that pathology of this disease is characterized by an increase of ammonia concentration in breath, its monitoring with a portable system can be a simple way for a noninvasive and early diagnostic on site. To realize such a system a new specific conductometric array of 11 different polyaniline nanocomposite sensors is used, based on the electronic nose principles. This approach allows bypass sensor weaknesses (sensor drift and sensitivity to humidity) and to determine ammonia in the typical concentration range of human breath (500 ppb–2100 ppb). In particular, polyaniline based nanocomposites with either titanium dioxide, chitosan or carbon nanotubes are used to provide different sensitivities and response times. This allows associating a single pattern of sensor responses to a concentration range. Maximum variation of resistance, derivative and integral values are extracted from the response curves of each sensor. Common classifiers are then tested and a selection feature algorithm is used. It permits improving the measurement accuracy and determining the most relevant features and sensors. Diagnosis accuracy reaches 91% with the combination of feature selection and Support Vector Machine algorithm.

International audience; Kidney failure is a critical chronic disease, defined as the irreversible loss of kidney functions. It has been shown that this pathology is associated with an increase of ammonia concentration in breath. Measuring it with a handheld system is a simple way for a noninvasive and early diagnostic. The idea of this paper is to measure the concentration of ammonia in a concentration range of human breath (500 ppb-2100 ppb) with humidity using a network of 11 different nanocomposite sensors. To overcome sensor weaknesses (sensor drift and sensitivity to humidity), the electronic nose principles are applied. Polyaniline-based nanocomposites with titanium dioxide, chitosan and carbon nanotubes are used to provide different sensitivities and response times and thus associate a single pattern to a concentration range. Several classifiers are then investigated and recursive feature elimination algorithm are used to select the most relevant features and sensors while improving the measurement accuracy. Diagnosis accuracy reaches 91% with the combination of feature selection and Support Vector Machine algorithm.

International audience; In the last decade, the use of electronic olfaction systems for the early diagnosis of several pathologies by breath analysis has been investigated. In this study, an electronic nose including seven polyaniline sensors has been developed. An impedance measurement circuit and a microcomputer to process the sensor responses were studied to give a pre-diagnosis conclusion. The measurement accuracy is 97% when it is exposed to a simulated human breath and different concentration of ammonia, from 500 ppb to 2.8 ppm. The described prototype weights about 300 g and can be used for 14 hours with a smartphone battery.

New ammonia and amine sensing materials based on hybrid polyaniline/titanium dioxide nanocomposites were synthesized by a one-pot chemical polymerization. Particular attention was paid to the influence of TiO2 nanoparticles and the surface active dopants on the structure–property relationship of the nanocomposites in terms of their morphology, composition, electrical and sensing properties. Dodecylbenzenesulfonic (DBSA) and lauryl sulfuric (LSA) acids were used as polyaniline dopants. The nanocomposites sensing properties were evaluated at different humidity levels when exposed to ammonia, methyl- and trimethylamine (0.2 ppm to 1 ppm). The materials demonstrated strong responses and high sensitivity to the gases with a quantification limit of 20 ppb for ammonia. The sensors are reversible and have short response times. However, the response magnitude depends on the dopant nature. The results were interpreted in terms of basicity and size of the analyte gas molecules.

Indoor environments present high specific pollutant concentrations, especially volatile organic compounds, inducing a risk for human health. Tools able to provide real-time information on indoor air quality (IAQ) are needed, in order to feed into the knowledge of these environments, identify the sources and automatically control remediation systems. Electronic gas micro-sensors are low-cost and nonintrusive instruments, which can be permanently deployed in large numbers to map the air quality of a whole building, but that still need to be evaluated. Five multi-sensors systems, combining several selective and non-selective electronic gas micro-sensors, have been installed inside a classroom at a low energy junior high school, in parallel with a set of standard analytical tools. The aim of this work was to determine if multi-sensors systems, associated with unsupervised k-means learning to process the data, were able to monitor effectively the dynamics of indoor air in a room in real conditions, and at what level of data quality.

International audience; Air Pollution monitoring and measurement are generally done using sampling techniques and analysis equipment often heavy, complex and expensive. Although these methods offer a high measurement precision which is essential to answer standards requirements, they are not adapted for quality oriented applications where simple information with low precision can be sufficient. The use of semiconductor gas sensors networks can provide the answer for a “low cost” system intended for such applications in air pollution detection fields. Three identical portable autonomous sensors arrays were built, each containing nine commercial semiconductor sensors especially chosen to detect a large range of pollutants usually encountered in ambient air and for a large part of them regulated. In order to overcome the temporal instability and the lack of reproducibility of these sensors, a calibration and normalisation procedure was developed. The obtained systems were used for on-site pollution monitoring in association with the French National Network of Accredited Associations for Air Quality Monitoring (AASQA). Gathered data from sensors systems and network data (NO, NO2, CO, PM2,5, …) were treated using nonlinear regression algorithms like Neural Networks with an original “fuzzy logic” type pre-treatment in order to compute a model able to predict the membership degree for three predefined pollution categories: traffic, urban and photochemical pollution, along with a pollution index describing the severity of the predominant pollution. The prediction rate was estimated system per system, and site per site for six sites. It has been shown that it was possible to obtain a quasi-universal model with a success rate over 80%.

In regard to other methods, nano-structured polymers present a credible alternative for the detection of air pollutants and in particular for ammonia detection. They can have large response to the pollutant, a very low detection threshold, a short response time and are relatively easy to fabricate. For polyaniline (PANI) composites, the metrological performances depend on the method of synthesis, the nature of dopant, of the polymer matrix and of the sensors fabrication. In this work, the ammonia sensing properties of composite materials based on PANI doped with a sulfonic acid in a polyurethane matrix were studied in the ppm range. It is shown that the deposition process of polymer solutions by electrospinning compared to the drop coating process improves the sensing properties in terms of sensitivity and response time. These results are interpreted by the modification of the morphology of materials.

Because of their size and price, miniature gas sensors are good candidates for long-term, large-scale, continuous monitoring of the air quality in confined environments, even in the presence of occupants. In spite of their still somewhat limited metrological performances, these tools are able to provide relevant information on the pollutants spatial and temporal evolution. They can therefore be used to identify pollution sources and automatically control ventilation and remediation systems, provided they are associated with adequate data treatment procedures. In the present study, four sensors for the detection of CO2, NO, NO2 and O3 have been deployed, without previous calibration, inside a classroom of a low energy high school building, together with standard analytical instruments. The data are analyzed with a procedure based on the bisecting K-means algorithm. This unsupervised classification allows the identification of similar measurements, which can be merged into clusters. An excellent agreement has been found between the classification results provided by the analyzers and by the sensors, even if the latter were not calibrated before deployment. These results validate the data treatment methodology proposed in this work, and demonstrate the potential of using commercial micro sensors in real conditions.

A growing number of companies have started commercializing low-cost sensors (LCS) that are said to be able to monitor air pollution in outdoor air. The benefit of the use of LCS is the increased spatial coverage when monitoring air quality in cities and remote locations. Today, there are hundreds of LCS commercially available on the market with costs ranging from several hundred to several thousand euro. At the same time, the scientific literature currently reports independent evaluation of the performance of LCS against reference measurements for about 110 LCS. These studies report that LCS are unstable and often affected by atmospheric conditions—cross-sensitivities from interfering compounds that may change LCS performance depending on site location. In this work, quantitative data regarding the performance of LCS against reference measurement are presented. This information was gathered from published reports and relevant testing laboratories. Other information was drawn from peer-reviewed journals that tested different types of LCS in research studies. Relevant metrics about the comparison of LCS systems against reference systems highlighted the most cost-effective LCS that could be used to monitor air quality pollutants with a good level of agreement represented by a coefficient of determination R2 > 0.75 and slope close to 1.0. This review highlights the possibility to have versatile LCS able to operate with multiple pollutants and preferably with transparent LCS data treatment.

We demonstrate here strong influences of the content of polyaniline (PANI) doped with dodecylbenzenesulfonic acid (DBSA) and the nature of dispersing solvents chlorobenzene (CB) and dichloroacetic acid (DCAA) on the morphology and sensing properties of TiO2/PANI-DBSA hybrid nanocomposite layers cast on transducer electrodes. The obtained results evidence that these effects are caused by the solubility of the PANI component of the synthesized nanocomposites in the solvents and the boiling temperature of the latter. To estimate a quantitative effect of PANI, we used the real contents of the PANI-DBSA component/phase determined from the PANI polymerization yield. The highest magnitudes and rates of the sensor responses to gaseous ammonia are shown by the nanocomposite layer with an intermediate PANI-DBSA content (18.9 wt%) and cast from the nanocomposite dispersion in CB. We explain this effect by the specific morphology of the layer, which appears to be due to the poor solubility of the PANI-DBSA component in this solvent. The comparison of sensitivity of the chemically synthesized nanocomposites to ammonia with that of their mechanically mixed analogs demonstrates the better sensing performance of the former.

cited By 7; International audience; Formaldehyde detection in air is of particular interest since this compound is classified as carcinogenic by the International Agency for Research on Cancer (IARC). It is abundant indoors (with an indoor/outdoor ratio around 5 to 15) and has as main origin the emissions from building or furniture materials. Among all the strategies currently used to control formaldehyde concentrations, none of them combines both good selectivity, low detection limit and easiness of use at low cost. To achieve this goal, we focused on the specific reaction between fluoral-p and formaldehyde to develop a sensor made of an intrinsically conducting polymer and fluoral-p. Formaldehyde reacts with fluoral-p to produce 3, 5-diacetyl-1, 4-dihydro-2, 6-lutidine (DDL) and ammonia. Polyaniline (PAni) was chosen as the conducting polymer due to its ammonia sensitivity as previously described by the authors. The performances of this new formaldehyde sensor have been evaluated in terms of sensibility, response time and detection limit. © 2011 IEEE.

Composites based on conductive organic/inorganic fillers dispersed in insulating matrix have been widely investigated because of their widespread applications such as electromagnetic shielding, electrostatic discharge, and sensors. In this context, novel composite materials based on epoxy resin matrix charged with polyaniline (PANI)-doped para-toluene sulfonic acid were elaborated. Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy were used to check the structure and the morphology of the samples. Viscoelastic behavior and thermal stability of the composites were explored by dynamic mechanical thermal analysis and thermogravimetric analysis. It was shown that the PANI particles exhibited a partial crystalline structure and were homogeneously dispersed in epoxy matrix. Consequently, this structure affected the thermal stability and viscoelastic properties of the composites. Furthermore, the dielectric and electrical properties were investigated up to 1 MHz. Measurements of dielectric properties revealed that with loading fillers in matrix, the dielectric parameters increased to high values at low frequency then decreased at values around 40 and 32 of real and imaginary parts, respectively, at 1 MHz with 15% of PANI content. Copyright © 2011 John Wiley & Sons, Ltd.

Polymer blends based on nanostructured polyaniline (PANI) doped with hydrochloric acid (HCl) and para-toluene sulfonic acid (PTSA) introduced into aliphatic polyurethane matrix (PU) are synthesized to produce flexible thin composite films for microwave absorbers. The effects of dopant type, PANI content and film thickness on morphologies, dielectric and microwave absorption properties in the X-band are studied. It reveals that real and imaginary parts of the complex permittivity are proportional to filler concentrations and type of doped PANI. The PANI-PTSA/PU films show higher permittivity and better microwave absorbing properties than PANI-HCl/PU for the same weight fraction of PANI. The minimum reflection loss RL(dB) values for the PANI-PTSA/PU are −37 dB at (20% PANI and 11.6 GHz) and −30 dB at (15% PANI and 11.3 GHz) for thicknesses of 1.2 and 1.6 mm, respectively. These high values of reflection losses make the obtained lightweight and flexible composites promising radar absorbing materials (RAM). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40961.

The source-receptor model Chemical Mass Balance (CMB) generally used for air pollution studies is applied for the first time to solve odor signature issues. The olfactory annoyance perceived at a receptor site of an industrial area is often the result of a combination of different smells, emitted by several industrial sources. To identify the main responsible for the inconvenience, tools able to determine the contribution of each source directly where the annoyance is perceived are widely developed and deployed. In this work, the contributions of volatile organic compound sources, coming from a waste treatment plant containing three potential sources of olfactory annoyance (waste storage, production of biogas, and compost piles of green wastes) and perceived at a village located downwind, are studied by chemical analyses. The CMB methodology is applied, and the results are finally compared to olfactometric methods, in order to validate whether it is appropriate to use this model for olfactory problems or not.

National audience; The aim of this work is to develop a multi-sensors array system based on semiconductor sensors for atmospheric pollution detection. The main disadvantages of these sensors are their low reproducibility and long-term stability. A calibration procedure was established to standardize all sensors sensitivity, in order to assure inter-cells signal homogeneity, and to correct any drift in sensors response. Complementary tests under low gas concentrations were made to prove the capacity of such system to detect sub-ppm gas concentrations.

International audience; Pas de résumé

The aim of this work is to quantify mixtures of two complex odor sources, sampled in a waste treatment plant site, using a MOS‐based e‐nose. The study was performed in two steps: a learning phase, using samples of pure sources, followed by a validation phase with binary mixtures in known proportions. The results proved that the model developed was able to predict the ratio of each source involved in the mixture.

Thin (1–40 μm) films of nanostructured polyaniline (PANI)-based composites are suggested for ppb range ammonia sensing. Three types of the composites have been studied: two core–shell systems with a poly(butyl acrylate) (PBuA) or poly(vinylidene fluoride) (PVDF) core and a PANI shell, and a composite based on PANI nanofibers embedded in a polyurethane (PU) matrix. Nanofibers and core–shell nanoparticles had a diameter around 100–200 nm. The gas sensing ability of the nanostructured films was compared to ammonia concentrations from 20 ppb to 10 ppm through the change of the sensors resistance. All the composites showed high performances in terms of response time, reversibility and detection limit. Specifically, the last parameter was below 100 ppb for films formed of the core–shell nanoparticles and below 20 ppb for the nanofiber based composites. However, while the response times were similar for all of the samples, the films made of the contacting core–shell nanoparticles had a higher sensitivity than PANI nanofibers embedded in the PU film matrix. The obtained results showed that nanostructured PANI-based composites of different morphologies can be used as ultra-sensitive and low cost ammonia gas sensors.

International audience; The development of a conducting composite from its one-step synthesis in aqueous dispersed medium to the characterization of its chemical sensor performance is detailed. Composite films of polyaniline and polyacrylate were processed from the crude dispersion with no need for post-formulation. The synthesis has been optimized to be as simple, cheap and transferable as possible. The composite composition is tunable, i.e. the nature of the dopant was varied and its effect on kinetic parameters was observed. Ab initio calculations have been performed on a series of six ionic systems to gain a deeper insight into the contribution of both the stability of the anilinium salts in the composite polymerization. The conductivities of all composites were recorded from room temperature to 150 °C and the thermal stability versus dopant highlighted. The conducting films were then studied as active layers in a chemical sensor. The results showed that these composites, easily synthesized and processed, are ammonia sensitive and exhibit a fast response when exposed to air pollution.

cited By 3; International audience; This study is based on the synthesis of composite particles made of polymer matrix and of intrinsically conducting polymer (ICP), with architecture control. Particle dispersion has been deposited on glass or plastic substrate to form a conducting film. This film has been successfully tested in sensor devices, namely gas sensors and electro-controlled delivery systems. In the first application, films have been performed and tested as active layer for ammonia detection. This chemical sensor template has been optimized in term of chemical composition and properties. These new sensors are sensitive (a pollution as low as 10 ppm ammonia is detected), exhibit a short response time (few seconds) and may be used several times in a row with the same performances. In the second application, core-shell particles have been entrapped into a hydrogel and these hydrogel composites have been characterized by polymerization kinetics, morphological, rheological, and swelling studies. These composites have been then evaluated as potentially drug release templates under electric field.