Ppm Ammonia Research Articles

Preparation and Gas Sensing Properties of PANI/SnO2 Hybrid Material.

A sensor operating at room temperature has low power consumption and is beneficial for the detection of environmental pollutants such as ammonia and benzene vapor. In this study, polyaniline (PANI) is made from aniline under acidic conditions by chemical oxidative polymerization and doped with tin dioxide (SnO2) at a specific percentage. The PANI/SnO2 hybrid material obtained is then ground at room temperature. The results of scanning electron microscopy show that the prepared powder comprises nanoscale particles and has good dispersibility, which is conducive to gas adsorption. The thermal decomposition temperature of the powder and its stability are measured using a differential thermo gravimetric analyzer. At 20 °C, the ammonia gas and benzene vapor gas sensing of the PANI/SnO2 hybrid material was tested at concentrations of between 1 and 7 ppm of ammonia and between 0.4 and 90 ppm of benzene vapor. The tests show that the response sensitivities to ammonia and benzene vapor are essentially linear. The sensing mechanisms of the PANI/SnO2 hybrid material to ammonia and benzene vapors were analyzed. The results demonstrate that doped SnO2 significantly affects the sensitivity, response time, and recovery time of the PANI material.

Commensal Escherichia coli Antimicrobial Resistance and Multidrug-Resistance Dynamics during Broiler Growing Period: Commercial vs. Improved Farm Conditions.

Simple SummaryThis experiment was designed to evaluate the differences in antimicrobial and multidrug resistance dynamics in broilers reared under two different farm conditions (commercial vs. improved) during the growing period, using Escherichia coli as sentinel bacterium. Although no antibiotics were applied during rearing for two different management conditions tested, high rates of antimicrobial and multidrug-resistant bacteria were observed throughout rearing, with the percentages of resistant bacteria observed being of particular concern in day-old chicks on arrival day and in chickens at the end of the growing period, just before delivery to the slaughterhouse.New measures applied to reduce antimicrobial resistances (AMR) at field level in broiler production are focused on improving animals’ welfare and resilience. However, it is necessary to have better knowledge of AMR epidemiology. Thus, the aim of this study was to evaluate AMR and multidrug resistance (MDR) dynamics during the rearing of broilers under commercial (33 kg/m2 density and max. 20 ppm ammonia) and improved (17 kg/m2 density and max. 10 ppm ammonia) farm conditions. Day-old chicks were housed in two poultry houses (commercial vs. improved), and no antimicrobial agents were administered at any point. Animals were sampled at arrival day, mid-period and at slaughter day. High AMR rates were observed throughout rearing. No statistical differences were observed between groups. Moreover, both groups presented high MDR at slaughter day. These results could be explained by vertical or horizontal resistance acquisition. In conclusion, AMR and MDR are present throughout rearing. Moreover, although a lower level of MDR was observed at mid-period in animals reared under less intensive conditions, no differences were found at the end. In order to reduce the presence of AMR bacteria in poultry, further studies are needed to better understand AMR acquisition and prevalence in differing broiler growing conditions.

Ammonia Sensing Performance of Polyaniline-Coated Polyamide 6 Nanofibers.

To understand the properties of polyaniline (PANI), aim gas, and the interaction between them in PANI-based gas sensors and help us to design sensors with better properties, direct calculations with molecular dynamics (MD) simulations were done in this work. Polyamide 6/polyaniline (PA6/PANI) nanofiber ammonia gas sensors were studied as an example here, and the structural, morphological, and ammonia sensing properties (to 50–250 ppm ammonia) of PA6/PANI nanofibers were tested and evaluated by scanning electron microscopy, Fourier transform infrared spectroscopy, and a homemade test system. The PA6/PANI nanofibers were prepared by in situ polymerization of aniline with electrospun PA6 nanofibers as templates and hydrochloric acid (HCl) as a doping agent for PANI, and the sensors show rapid response, ideal selectivity, and acceptable repeatability. Then, complementary molecular dynamics simulations were performed to understand how ammonia molecules interact with HCl-doped PANI chains, thus providing insights into the molecular-level details of the ammonia sensing performances of this system. Results of the radial distribution functions and mean square displacement analysis of the MD simulations were consistent with the dedoping mechanism of the PANI chains.

Enhanced ammonia sensing properties of rGO/WS2 heterojunction based chemiresistive sensor by marginal sulfonate decoration

Abstract Two-dimensional reduced graphene oxide (rGO) nanosheets were pre-sulfonated and further incorporated by WS2 nanoflakes to form S-rGO/WS2 heterojunctions by hydrothermal synthesis. The sulfonation and WS2 incorporation in S-rGO/WS2 heterojunction have been confirmed by EDS, XPS and FTIR. The sensing performance of rGO-based chemiresistive-type sensor to ammonia at room temperature has been significantly improved by the sulfonation and incorporation of WS2 nanoflakes. The chemiresistive sensor based on S-rGO/WS2 exhibits enhanced response signals to 10∼50 ppm ammonia, while the response/recovery time is significantly shortened compared to rGO/WS2 reported previously at room temperature. It benefits from both the extra introduced active acid centers sensitive to ammonia molecules and the better desorption-ability facilitated significantly by sulfonate groups (S O3H). The adsorption energy calculation of ammonia molecule on the sulfonated graphene sheet based on density functional theory (DFT) has been performed to illustrate the adsorption capacity of S O3H group. The selectivity and stability of gas sensor based on S-rGO/WS2 have also been studied.

Acetone sensing properties of the g–C3N4–CuO nanocomposites prepared by hydrothermal method

A hydrothermal method was utilized to synthesize pure CuO and g–C3N4–CuO nanocomposites for detecting different volatile organic compounds (VOCs). The morphology and chemical composition of the g–C3N4–CuO composites were characterized by different techniques such as XRD, SEM, TEM, EDS, TG–DSC, XPS, FTIR and N2 adsorption-desorption isotherms, respectively. By exposing the sensor of 4 wt % g–C3N4–CuO (S-3) nanocomposite into different VOCs, the better gas sensing response and the gas sensing selectivity to acetone were identified, the responses of S-3 nanocomposite based sensor were 143.7 and 1.26 to 1000 ppm and 0.01 ppm acetone, respectively; imperatively, the selectivity ratio of S 1000 ppm acetone/S 1000 ppm ammonia was 14.37, the response/recovery times were (17/24 s) for optimum concentration (1000 ppm) of acetone. Comparing with pure CuO nanoparticles, the specific surface area of nanocomposite was increased by the decoration of CuO nanoparticles onto g-C3N4 sheet.

Integration of a porous wood-based triboelectric nanogenerator and gas sensor for real-time wireless food-quality assessment

Monitoring the quality of perishable food in real time is critical for reducing the societal costs and foodborne diseases. A self-powered triboelectric nanogenerator (TENG)-based wireless gas sensor system (TWGSS) is presented to realize selective, sensitive, and real-time wireless food-quality assessment in a cold-supply chain. TWGSS can real-time monitor the key food spoilage markers gas (e.g., ammonia) and maintain excellent stability under high humidity (75%) and low temperature (−18 °C). Benefiting from the three-dimensional porous structure of wood and ammonia sensitive properties of the carbon nanotubes materials, output voltage of the TENG selectively decreases with the increase of ammonia concentrations from 50 to 500 ppm. Moreover, the TENG exhibits an ammonia-sensing response of 0.85 at 500 ppm ammonia, which is much higher than the other common gases released from perishable foods under the same gas concentrations. Through system integration and power management, a self-powered triboelectrically driven system that can also be used as a gas sensor and wirelessly transmit data to the user interfaces. This work provides a design concept for the application area of the TENGs to the assessment of food quality, and also promotes the development of self-powered systems in food industry. ● A wood-based triboelectric nanogenerator (TENG) was developed and used as NH 3 sensor. ● The self-powered TWGSS was proposed by integrating the TENG with the wireless circuitry. ● The TWGSS realized real-time wireless food-quality assessment in a cold-supply chain.

Selective and Trace Level Detection of Hydrazine Using Functionalized Single-Walled Carbon Nanotube-Based Microelectronic Devices

Microelectronic devices (MEDs) that utilize functionalized single-walled carbon nanotubes (SWCNTs) for hydrazine (HZ) sensing applications were developed and investigated, demonstrating their selective and sensitive detection of trace level HZ (0.01 ppm) in the presence of high-concentration interfering gases in ambient air at room temperature. These MEDs were fabricated with excellent reproducibility by the site-specific deposition of functionalized SWCNTs using a dielectrophoretic technique. Rigorous gas exposure testing conducted on these MEDs demonstrated a fast response with high sensitivity, selectivity, reproducibility, and reliability for detecting HZ. A dynamic response range was established from a linear relationship between the sensor response and the concentration of HZ (0.01 to 0.33 ppm). Additionally, these MEDs exhibited a linear trend relationship between device resistance and sensor response, which provided tunability in selecting and fabricating devices for improving sensing response. Field-emission scanning electron microscopy images showed the morphology of SWCNTs as a bundle on MEDs. Additional analytic gas exposure tests revealed negligible responses from these MEDs for high concentrations of interfering gases, such as 300 ± 17 ppm methanol (MeOH), 85 ± 6 ppm ethanol (EtOH), 145 ± 12 ppm formaldehyde (CH2O), and 500 ppm ammonia (NH3), compared to that of HZ (≤0.33 ppm), with HZ to interfering gas concentration ratios of 1:900, 1:250, 1:440, and 1:1500, respectively, demonstrating high sensor selectivity for HZ.

A highly sensitive cobalt chromite thick film based trace acetone sensor with fast response and recovery times for the detection of diabetes from exhaled breath

Acetone is known as the breath biomarker of diabetes. In this paper we have reported on a highly sensitive, stable cobalt chromite (CoCr2O4) thick film-based trace acetone sensor with quick response and recovery times promising for the detection of diabetes from exhaled breath. CoCr2O4 nanoparticles were prepared by a cost-effective and easy sol-gel method. The as prepared nanoparticles were well characterized by sophisticated characterization techniques, such as, XRD, FESEM. TEM, HRTEM, XPS, and BET. Further these nanoparticles were exploited to fabricate a Taguchi type chemoresistive sensor using a customized drop coater. The developed sensor was characterized by I–V measurement. The developed sensor exhibited high p-type response towards 1 ppm of acetone vapor (~3.81 folds), and appreciable resolution between 1 ppm, 2 ppm (response = ~4.82 folds), and 5 ppm (response = ~6.64 folds) acetone vapor at 300 °C. Further, the sensor exhibited fast response and recovery times of ~1.65 s and ~62 s, respectively. Also, the response of the sensor to 1 ppm acetone vapor is appreciably higher than that of 0.2 ppm ethanol, 0.25 ppm ammonia vapor, and saturated moisture. Finally, the sensor is stable for at least 6 months and exhibits repeatable measurements.

The alterations of tracheal microbiota and inflammation caused by different levels of ammonia exposure in broiler chickens

Ammonia (NH3) is a known harmful gas and exists in haze, forming secondary organic aerosols. Exposure to ambient ammonia correlates with the respiratory tract infection, and microbiota in the upper respiratory tract is an emerging crucial player in the homeostatic regulation of respiratory tract infection, and microbiota perturbation is usually accompanied by the inflammatory reactions; however, the effects of different levels of ammonia exposure on tracheal microbiota and inflammation are unclear. A total of 288 22-day-old male Arbor Acres broilers were chosen and divided into 4 groups with 6 replicates of 12 chickens, and respectively exposed to ammonia at 0, 15, 25, and 35 ppm for 21-d trial period. Cytokines (interleukin (IL)-1β, IL-6, and IL-10) in the trachea were measured at the 21 d of exposure to NH3. Tracheal microbiota at the 21 d was analyzed by the 16S rRNA gene analysis. The results showed that an increase in ammonia levels, even in 15 ppm, significantly decreased the alpha diversity and changed the bacterial community structure. Six genera (Faecalibacterium, Ruminococcus]_torques_group, unclassified_f__Lachnospiraceae, Ruminococcaceae_UCG-014, Streptococcus, Blautia) significantly increased, whereas Lactobacillus significantly decreased under different levels of ammonia exposure. We also observed positive associations of Faecalibacterium, Blautia, g__Ruminococcaceae_UCG-014, unclassified_f__Lachnospiraceae and Ruminococcus]_torques_group abundances with tracheal IL-1β concentration. Moreover, an increase in ammonia levels, even in 15 ppm, caused respiratory tract inflammatory injury. The results indicated that 15 ppm ammonia exposure changed the composition of tracheal microbiota that caused the tracheal injury possibly through increasing the IL-1β, which might make the broiler more sensitive to the changes of environment and pathogenic micro-organisms in the poultry house, and may be also a critical value that needs high alertness. Herein, the present experiment also suggested that the standard limit of ammonia concentration in adult poultry house is 15 ppm. This research provides an insight into the relationship between the upper respiratory tract microbiota and inflammation under ammonia exposure.

An Investigation of the Ammonia-Sensing Mechanism of α-MoO3-Based Chemi-Resistive Sensors

Chemi-resistive ammonia sensors based on alpha-phase molybdenum trioxide (α-MoO3) are a simple and selective technology for measuring the concentration of gaseous ammonia for applications such as human breath sensing and monitoring selective catalytic reduction (SCR) systems [1-7]. The basic operating principle of these sensors is the correlation between the electrical resistance of the sensor and the concentration of ammonia to which the sensor is exposed. Typically, the sensor consists of an interdigitated electrode substrate covered with the α-MoO3 film [1-7]. The electrical resistance of the α-MoO3 film changes as a function of ammonia concentration. This change in resistance of the α-MoO3 film is commonly attributed to the alteration of the charge depletion layer (Λ) of the α-MoO3 particles through the reaction of ammonia with adsorbed oxygen species [5-9]. For α-MoO3, the charge depletion layer model predicts that the resistance of the film should decrease with increasing ammonia concentration. In addition to the charge depletion layer model, other sensing mechanisms have been suggested, such as the partial reduction by ammonia of the surface of the α-MoO3 film [1,2] and the formation of oxygen vacancies in the α-MoO3 lattice [3].The α-MoO3 film can be fabricated by a variety of methods, including sol-gel synthesis, ion beam deposition, hydrothermal synthesis, and flame spray pyrolysis [1-6]. In this work, the α-MoO3 film is fabricated using Reactive Spray Deposition Technology (RSDT) followed by annealing to develop crystallinity. The RSDT is a flame-based process that can be used for the fabrication of α-MoO3 films at a commercial scale. The initial development of ammonia sensors with RSDT-fabricated α-MoO3 films of varying morphology was presented at the 236th ECS Meeting as an oral presentation, “Ammonia-Sensing Properties of α-MoO3 Fabricated by Reactive Spray Deposition Technology (RSDT).” From these initial sensors, the sensor with the strongest response to ammonia was selected for further testing at concentrations between 0.1 ppm and 5 ppm ammonia in dry air at 400°C. These sensing results and the materials characterization of the sensor by SEM and XRD before and after 80 hours of continuous testing are reported in Ebaugh et al. [7] and are shown in Figures 1-3. In Figure 1, the sensing results among the three test cycles comprising the 80 hours of testing are quite repeatable; however, the results consistently depart from the prediction of the charge depletion layer model between 3 ppm and 5 ppm.To better explain this unexpected sensing behavior, additional electrochemical testing and materials characterization is needed. Specifically, normal pulse voltammetry (NPV) can be used to provide data pertaining to the electronic path through the α-MoO3 film and the reaction and transport of chemical species adsorbed on the α-MoO3 film. TEM analysis of the α-MoO3 can show the nanoscale morphology of the sensing material. It is well established that the nanoscale morphology of the metal-oxide film impacts its sensing behavior [8-10]. XPS can also be used to investigate the possible reduction of the surface of the α-MoO3 particles and the formation of oxygen vacancies in the α-MoO3 lattice. Data from the materials characterization of the sensing film (XRD, SEM, TEM, and XPS) will be used in conjunction with sensing results and NPV data to develop an explanation for the sensor behavior observed in [7]. An understanding of the ammonia-sensing mechanism will help to guide the optimization of the RSDT-fabricated α-MoO3 film to improve the performance of the sensor for a wide range of applications.References A. K. Prasad, et al. Thin Solid Films. 436 2003 pp. 46-51.P. Gouma, et al. IEEE Sensors Journal. 10 (1) 2010 pp. 49-53.A. K. Prasad, et al. Sensors and Actuators B: Chemical. 93 2003 pp. 25-30.P Gouma, et al. Journal of Breath Research. 5 2011 p. 037110.A. T. Güntner, et al. Sensors and Actuators B: Chemical. 223 2016 pp. 266-273.D. Kwak, et al. ACS Applied Materials & Interfaces. 11 2019 pp. 10697-10706.T. A. Ebaugh, et al. ACS Applied Materials & Interfaces. Under review.C. S. Rout, et al. Nanotechnology. 18 2007 p. 205504.M. E. Franke, et al. Small. 2 (1) 2006 pp. 36-50.N. Barsan, et al. Fresenius Journal of Analytical Chemistry. 365 1999 pp. 287-304. Figure 1

Total ammonia and N<SUB align="right">2O emission characteristics from <i>Alcaligenes</i> sp. LS2T cultures and its application on laying hen manure associated with different pH conditions

The main objective of this research was to investigate the Alcaligenes sp. LS2T characteristics in total ammonia and N2O emission under different carbon sources and C/N ratios in the synthetic media. Observation of the strain application potential to suppress ammonia emission was also performed on laying hen manure with different initial pH conditions. The total ammonia concentration was observed by Nessler's reagent photometry method followed by Lide and Frederikse equation, while the N2O emission was measured by gas chromatography. The result showed that the least total ammonia concentration (12.77 ± 2.61 ppm) was seen in acetate C/N 28 medium. The highest N2O emission was seen in citrate C/N 14 medium, which emitted 377.13 ± 20.11 ppb N2O. The least emitted ammonia in the manure media was seen in an acid medium (116.92 ± 8.34 ppm ammonia). The results showed the Alcaligenes sp. LS2T capabilities to remove ammonia under aerobic condition.

Broilers' head behavior as an early warning index of production and lung health under ammonia exposure

This study investigated the effects of ammonia exposure (0, 15, 25, and 35 ppm) on head behavior, production performance and lung tissue morphology of broilers, and the relationship between head behavior, production performance, and lung tissue injury. In this experiment, a total of 264 AA commercial male broilers (21 d old) were assigned to 4 treatment groups with 6 replicates of 11 chickens for a 21-day trial period, the frequency of head-scratching and head-shaking behavior at the initial stage (2, 24, and 72 h) of ammonia exposure were recorded, and the production performance indices and the lung pathological changes after 21 d of ammonia exposure were observed. The correlation analysis was established between head behavior and production performance indices. Results showed that head-scratching behavior increased under 15 ppm ammonia for 72 h, head-shaking behavior increased when exposure to 15 ppm ammonia for 2, 24, and 72 h, and lung tissue was injured when exposure to 15 ppm ammonia for 21 d. However, exposure to 15 ppm ammonia did not influence growth performance. Compared with the control group, exposure to 25 ppm decreased the ADG and exposure to 35 ppm decreased the ADG, ADFI, and F/G. Furthermore, the increase in head-shaking frequency after 2 h and 24 h ammonia exposure was significantly associated with production performance and lung tissue injury after 21 d ammonia exposure. In conclusion, the head-shaking behavior at the initial stage of ammonia exposure can reflect the degree of harm of the later production performance and lung tissue health.

Enhanced room temperature ammonia gas sensing properties of Al-doped ZnO nanostructured thin films

In this present research work, we report the preparation of successfully synthesized ZnO films as pristine and doped with Al(Al-ZnO) on glass via facile, eco-friendly, and controllable SILAR method. A systematic evolution of structural, surface morphology, composition, photoluminescence and ammonia gas sensing behaviour of the system was investigated with a variation of Al dopant. XRD examination disclosed polycrystalline nature with the hexagonal system of all films and crystallite size was noticed between 37 and 51 nm. EDX study approves the presence of Al doping in ZnO. Surface morphological tests through SEM presented the formation of nanoparticles and nanorods with a variation of Al content. The photoluminescence study revealed that due to Al doping the PL intensity was quenched which signifies the reduction of defects in the films. It was shown that the estimated values of the energy gap are enlarged to 3.12 from 3.01 on rising the Al content till 3wt.% and finally decreased for 5wt.% Al content. The gas sensing analysis showed that Al doping content was made to drastically increase the gas sensing response. Compared with other dopant levels, the 3wt.% Al-ZnO nanorods unveiled the uppermost retort when tested to 100 ppm ammonia (NH3) gas concentration at room temperature.

Understanding Degradation Phenomena in HT-PEM Fuel Cells Using Micro-Computed Tomography

In times of transition from conventional energy-converting techniques to new technologies for the generation of power and electricity, polymer electrolyte membrane fuel cells (PEMFC) play a crucial role. Especially high temperature (HT)-PEMFCs are operated at around 160 °C and can be fuelled using reformate gas from methanol or natural gas reformers allowing to be used for both, mobile and stationary applications. Typically combined heat and power systems or range extenders are in the current focus of the industry.While the HT-PEMFC technology has made great progression in the last decades and started its way into commercialization, it still has to undergo more stages of advancement in order to become a real alternative for power supply in various sectors. One major hindrance of the technology is their insufficient lifetime accompanied by a lack of knowledge about external factors causing system degradation. Therefore, all cell components need a detailed degradation analysis which contributes to fundamental understanding.1-3 In this work, we investigate the components of the HT-PEMFC such as the bipolar plates (BPPs) and the membrane electrode assembly (MEA) regarding degradation phenomena during cell operation with use of contaminated air. By applying µ-computed tomography (µ-CT), these components are analysed in detail with the aim to reveal structural and morphological changes on the micro meter scale that occur during the life time.If the cell is operated with traces of contaminants (e. g. 10 ppm ammonia in the cathodic air stream) for a certain time period under constant load conditions, µ-CT investigation helps to identify degradation of the individual components. Figure 1 shows a reconstructed µ-CT image of a typical MEA with the gas diffusion layers (GDL) and the anode and cathode separated by the membrane. Analysis of thicknesses using single cross-sectional images of the MEA reveals that the catalyst layers do not change, while the membrane thickness decreased around 15 µm after operation with trace amounts of NH3. While this study shows local degradation of the MEA, we will investigate the BPP and its porosity after application in single cell HT-PEMFC under various operating conditions using µ-CT in another study. In combination we aim to present the opportunities of employing µ-CT as a technique to visualize and better understand degradation phenomena in HT-PEM fuel cell components. Søndergaard, T.; Cleemann, L. N.; Becker, H.; Steenberg, T.; Hjuler, H. A.; Seerup, L.; Li, Q.; Jensen, J. O., Journal of The Electrochemical Society 2018, 165, (6), F3053-F3062.Büsselmann, J.; Rastedt, M.; Klicpera, T.; Reinwald, K.; Schmies, H.; Dyck, A.; Wagner, P., Energies (Open Access Journal) 2020, 13, (3), 567.Kannan, A.; Li, Q.; Cleemann, L. N.; Jensen, J. O., Fuel Cells 2018, 18, (2), 103-112. Figure 1

Fabrication of flexible polyaniline@ZnO hollow sphere hybrid films for high-performance NH3 sensors

In this study, a simple inexpensive gas sensor, which uses polyaniline@ZnO hollow sphere hybrid films, is prepared with different mole percentages of ZnO hollow spheres (5–30 mol%) and combining hydrothermal and in-situ chemical oxidative polymerization methods. Polyaniline@ZnO hollow sphere hybrids are loaded on flexible polyethylene terephthalate substrates for rapid and selective detection of ammonia at room temperature. The morphology, structure, chemical functional group information and the specific surface area are, respectively, characterized by field emission-scanning electron microscopy, X-ray diffraction, Fourier transform infrared and N2 adsorption–desorption techniques. The best sensing performance is realized for the polyaniline@20 mol% ZnO hollow sphere hybrid sensor, which is exposed to 10 ppm ammonia at room temperature. Moreover, this sensor exhibits a low detection limit of 500 ppb, excellent selectivity and good response/recovery times (140/136 s). This good sensing performance can be attributed to the hollow structure of ZnO and the p–n heterojunction between the polyaniline and ZnO hollow spheres.

Novel barium hexaferrite based highly selective and stable trace ammonia sensor for detection of renal disease by exhaled breath analysis

Exhaled human breath bears the fingerprints of multifarious pathophysiological conditions, and diseases. In this paper we report for the first time a highly sensitive, selective, and stable barium hexaferrite based sensor for the detection of trace ammonia vapor in exhaled human breath, the biomarker for renal diseases. Barium hexaferrite nanoparticles were synthesized by a facile solid-state reaction route. The as prepared nanopowder and the sensor film were well characterized by using XRD, FESEM, TEM, EDX, XPS, BET, and I-V measurements. The fabricated sensor delineates p-type behavior and the capability to detect ammonia down to 0.2 ppm with reasonably high response of ∼1.46 folds. Further, the sensor showed remarkable response of ∼2.34 folds towards 1 ppm ammonia. The sensor is practically insensitive towards similar concentrations of other major interfering breath volatiles, viz. acetone, ethanol, and saturated moisture. Also, the sensor exhibited fast response (∼2.88 s), and recovery (∼39.4 s) times ensuring real time breath analysis. Finally, long-term stability of the sensor for more than three months renders it suitable for commercial applications.

Ammonia exposure causes lung injuries and disturbs pulmonary circadian clock gene network in a pig study

Ammonia toxicity to respiratory system in pig faming is of particular concern, but the molecular mechanism remains still unclear. The present study was devoted to assess the impacts of the ammonia exposure on the lung tissues based on a pig study using 80 ppm ammonia exposing to piglets for different days. The histology analysis revealed ammonia exposure induced lung injury and inflammatory response, as indicated by epithelial-mesenchymal transition (EMT), significant thickening of alveolar septa, infiltration of inflammatory cells and excessive mucus production. The transcriptome analysis revealed many more up-regulated genes in exposure groups when compared with the control group, and these genes were significantly enriched in the GO term of extracellular exosome, proteolysis, and regulation of circadian rhythm. The study discovered the induction of seven genes (CRY2, CIART, CREM, NR1D1, NR1D2, PER1 and PER3) that encode repressors of circadian clock. One gene (ARNTL) that encodes activator of circadian clock was down-regulated after ammonia exposure. The results of this study suggest that ammonia exposure disturbed the pulmonary circadian clock gene expression, which may establish new evidence for further understanding the toxicity of ammonia to lungs.

Electrical conductivity and ammonia sensing studies on polythiophene/MWCNTs nanocomposites

Over the years, conducting polymer nanocomposites have been successfully utilized for the fabrication of ammonia sensors. But, fabrication of a sensor for selective detection of ammonia below 01 ppm is still a challenging task. Herein, we prepared polythiophene (PTh) and a series of PTh nanocomposites with multiwalled carbon nanotubes (MWCNTs) by in-situ chemical oxidation technique. The as-prepared samples were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). PTh/MWCNTs nanocomposites showed significantly enhanced electrical conductivity as well as ammonia sensing performance as compared to PTh. The sensor-based on PTh/MWCNTs-3 (PTh/MWCNTs nanocomposite containing 15% MWCNTs to the weight of monomers) was found to be an ultra-sensitive (detection limit of 0.1 ppm), completely reversible, highly selective and stable ammonia sensor at room temperature. The sensing response of PTh/MWCNTs-3 at 2000, 1500, 1000, 500, 400, 200, 100, 50, 1 and 0.1 ppm of ammonia was found to be 88.70%, 73.27%, 62.04%, 51.65%, 46.96%, 42.97%, 38.86%, 35.18%, 32.93% and 27.66%, respectively. The result showed that the relative humidity had only a small effect on ammonia sensing properties of PTh/MWCNTs-3. We demonstrated the sensing mechanism by electronic interaction of polarons (i.e. charge carriers) of PTh with the lone pairs of electrons of the ammonia molecule.

Three-dimensional conductive organic sulfonic acid co-doped bacterial cellulose/polyaniline nanocomposite films for detection of ammonia at room temperature

Polymer sulfonic acid doped polyaniline (PANI) can improve the response to ammonia. An ammonia sensor (BC/PANI-DBSA/PAMPS) with ultrafast, selective and sensitive detecting capability based on bacterial cellulose (BC) film with a three-dimensional nano-network structure is reported. The sensor consists of PANI coated BC nanofiber co-doped with dodecylbenzene sulfonic acid (DBSA) and poly(2-acrylamido-2-methyl-1-propane sulfonic acid) (PAMPS), made by an in situ chemical oxidation polymerization route. The sensing response of the DBSA and PAMPS co-doping PANI composite in the range of 10−150 ppm ammonia vapor was greatly enhanced compared to sole doped composite, and showed high sensing selectivity towards ammonia, with a low detection limit of 200 ppb at room temperature. More importantly, the sensor display an excellent response (S = 6.1) and rapid response/recovery time (10.2 s/8.6 s) toward 100 ppm ammonia, and still showed excellent sensing capability after up to 60 days. Taken together, this work provides a facile and green approach to fabricate macroscale materials with ultra-fine nanoscale architecture for fast and sensitive gas detection.

Room temperature ammonia gas sensor based on polyaniline/copper ferrite binary nanocomposites

In this work, a polyaniline/copper ferrite (PANI/CuFe2O4) heterostructure was synthesized by in situ polymerization for the first time, and a high-performance NH3 sensor was developed by coating the heterostructure onto a substrate with staggered electrodes. The composition, chemical state and morphology of the PANI/CuFe2O4 composite was characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy (Raman), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The TEM and SEM results showed that the CuFe2O4 had a nanometer microsphere structure and PANI nanocapsules that were rod-like. The sensitivity of the PANI/CuFe2O4 sensor to different concentrations of NH3 gas was investigated at room temperature. The experimental results showed that the PANI/CuFe2O4 film shows excellent performance in terms of high response and selectivity: the response at 5 ppm ammonia was found to be as high as 27.37 %, which was clearly superior to that found for pristine PANI and CuFe2O4 films. The PANI/CuFe2O4 nanocomposite showed excellent sensitivity toward NH3 sensing, which can be attributed to the interaction between p-n heterojunctions in the binary nanocomposite. In addition, an ammonia alarm circuit based on the fabricated sensor was developed to realize practical applications for the detection of ammonia concentrations beyond the current limits.