NH3 Gas Concentration Research Articles

Fast response paper based visual color change gas sensor for efficient ammonia detection at room temperature

We show that a cheap, disposable type rapid paper sensor (working at room temperature) can be made using perovskite halide CH3NH3PbI3 (MAPI) to detect presence of the toxic ammonia gas (NH3)by just color change, where the black colored MAPI film (on the paper) changes to yellow color in presence of a very low concentration of NH3 gas. The sensor can detect presence of NH3 gas in open or closed atmosphere down to around 10 ppm with a response time of nearly 10 sec which decreases to few seconds when the concentration exceeds 20 ppm. The easy to fabricate sensor paper being a visual sensor does not need any other extra equipment for its operation. The sensor is not sensitive to moisture with RH upto 90% and does not also respond to gases like Methane (CH4), Nitrous Oxide (N2O), Carbon dioxide (CO2) etc in the test chamber each up to a concentration of 500 ppm. Conversion/decomposition of MAPI to PbI2 on exposure to NH3 has been proposed as the mechanism of color change and the mechanism has been established using a collection of techniques like XRD, EDX, UV-Visible absorption and Photo Luminescence.

A Room-Temperature CNT/Fe₃O₄ Based Passive Wireless Gas Sensor.

A carbon nanotube/Fe3O4 thin film-based wireless passive gas sensor with better performance is proposed. The sensitive test mechanism of LC (Inductance and capacitance resonant) wireless sensors is analyzed and the reason for choosing Fe3O4 as a gas sensing material is explained. The design and fabrication process of the sensor and the testing method are introduced. Experimental results reveal that the proposed carbon nanotube (CNT)/Fe3O4 based sensor performs well on sensing ammonia (NH3) at room temperature. The sensor exhibits not only an excellent response, good selectivity, and fast response and recovery times at room temperature, but is also characterized by good repeatability and low cost. The results for the wireless gas sensor’s performance for different NH3 gas concentrations are presented. The developed device is promising for the establishment of wireless gas sensors in harsh environments.

A Highly Stable Two-Dimensional Copper(II) Organic Framework for Proton Conduction and Ammonia Impedance Sensing.

This work reports the design and fabrication of a proton conductive 2D metal-organic framework (MOF), [Cu(p-IPhHIDC)]n (1) (p-IPhH3 IDC=2-(p-N-imidazol-1-yl)-phenyl-1 H-imidazole-4,5-dicarboxylic acid) as an advanced ammonia impedance sensor at room temperature and 68-98 % relative humidity (RH). MOF 1 shows the optimized proton conductivity value of 1.51×10-3 S cm-1 at 100 °C and 98 % RH. Its temperature-dependent and humidity-dependent proton conduction properties have been explored. The large amount of uncoordinated carboxylate groups between the layers plays a vital role in the resultant conductivity. Distinctly, the fabricated MOF-based sensor displays the required stability toward NH3 , enhanced sensitivity, and notable selectivity for NH3 gas. At room temperature and 68 % RH, it gives a remarkable gas response of 8620 % to 130 ppm NH3 gas and lower detection limit of 2 ppm towards NH3 gas. It is also found that the gas response of the ammonia sensor increases linearly with the increase of NH3 gas concentration under 68-98 % RH and room temperature. Moreover, the sensor indicates excellent reversibility and selectivity toward NH3 versus N2 , H2 , O2 , CO, CO2 , benzene, and MeOH. Based on structural analyses, activation energy calculations, water and NH3 vapor absorptions, and PXRD determinations, proton conduction and NH3 sensing mechanisms are suggested.

Application of Passive Sampler for Ammonia Gas in Soil

The emissions of ammonia (NH3) from soil have accelerated rapidly and have affected both vegetation and the atmosphere. It is thus necessary to investigate not only the amounts of NH3 gas released from the soil surface but also the dynamics of NH3 gas in the soil. Active sampling and diffusive sampling have been adopted to measure the components of soil air. However, gas aspiration for active sampling inevitably collects a wide range of soil gases. We examined the application of passive sampling to NH3 gas measurements in soil and compared the outcome to active sampling results. In laboratory experiments, the performance of the present passive sampler in moist soil was investigated. When immersed in solution, the passive sampler collected gas released from the solution, depending on the vapor pressure of the volatile substance. In laboratory experiments measuring NH3 gas in soil, there were no significant differences among the values measured by passive sampler at each measurement point. Thus, we concluded that the passive sampler can accurately measure NH3 gas in soil. In field experiments, the average NH3 gas concentrations were 43 ppb in urea-added soil and 1 ppb in control soil. The relative standard deviation of NH3 concentrations in urea-added soil was large. This result is expected because soil characteristics can change under the influence of ambient environmental factors such as wind, rain, and temperature. In other words, the spatial differences in NH3 emissions were reflected in the passive sampler measurements.

Physical quality and digestibility in vitro determination of green pellet concentrate based on Indigofera zollingeriana

<p>This study aims to determine the physical quality and digestibility of green pellet concentrate based on <em>I.</em><em> zollingeriana</em>. The composition of green pellet concentrate feed contains <em>I. zollingeriana</em> and <em>C.</em><em> calothyrsus</em> in the following combinations: 1) <em>I.</em><em> zollingeriana</em> /<em>C.</em><em> calothyrsus</em> (90/0; R0), 2) <em>I.</em><em> zollingeriana</em>/<em>C. calothyrsus</em> (75/15; R1), 3) <em>I.</em><em> zollingeriana</em>/<em>C. calothyrsus</em> (60/30; R2) and 4<em>) I.</em><em> zollingeriana</em> / <em>C. calothyrsus</em> (45/45; R3). The physical quality study of green pellet concentrate was performed using a completely randomized design with four types of green concentrate as treatments of three replications. Green pellet concentrate studies conducted in vitro rumen fermentation were performed using in a randomized block design with four treatments and three sources of liquid rumen as a block. The results of the experiments conducted with pellet criteria containing <em>I.</em><em> zollingeriana/C. calothyrsus </em>composition (60/30; R2) have the best physical character (water activity = 0.58; particles size = 12.69 mm; degree value angles = 21.01<sup>o</sup>; collision endurance = 99.78%; endurance friction = 90.42 %; bulk density = 590 kg/m3) compared to the other treatments. The quality of diet based on digestibility in vitro, dry matter and organic material having a pattern equal to R0 is higher (P<0.05) compared with other treatments, while the rough digestibility of In Vitro protein is seen R0, R1, and R2 (P>0.05), but (P<0.05) was higher than the treatment of R3. There was no difference of pH and total bacteria on green pellet concentrate type. The treatment of R3 has the lowest NH3, VFA and total gas concentration (P<0.5) compared with R2, R1 and R0. It was concluded that concentrate green pellet of <em>I.</em><em> zollingeriana</em> composition (60%) and <em>C.calothyrsus</em> (30%) had better physical and nutritional quality.</p>

Agricultural ammonia emissions in China: reconciling bottom-up and top-down estimates

Abstract. Current estimates of agricultural ammonia (NH3) emissions in China differ by more than a factor of 2, hindering our understanding of their environmental consequences. Here we apply both bottom-up statistical and top-down inversion methods to quantify NH3 emissions from agriculture in China for the year 2008. We first assimilate satellite observations of NH3 column concentration from the Tropospheric Emission Spectrometer (TES) using the GEOS-Chem adjoint model to optimize Chinese anthropogenic NH3 emissions at the 1∕2° × 2∕3° horizontal resolution for March–October 2008. Optimized emissions show a strong summer peak, with emissions about 50 % higher in summer than spring and fall, which is underestimated in current bottom-up NH3 emission estimates. To reconcile the latter with the top-down results, we revisit the processes of agricultural NH3 emissions and develop an improved bottom-up inventory of Chinese NH3 emissions from fertilizer application and livestock waste at the 1∕2° × 2∕3° resolution. Our bottom-up emission inventory includes more detailed information on crop-specific fertilizer application practices and better accounts for meteorological modulation of NH3 emission factors in China. We find that annual anthropogenic NH3 emissions are 11.7 Tg for 2008, with 5.05 Tg from fertilizer application and 5.31 Tg from livestock waste. The two sources together account for 88 % of total anthropogenic NH3 emissions in China. Our bottom-up emission estimates also show a distinct seasonality peaking in summer, consistent with top-down results from the satellite-based inversion. Further evaluations using surface network measurements show that the model driven by our bottom-up emissions reproduces the observed spatial and seasonal variations of NH3 gas concentrations and ammonium (NH4+) wet deposition fluxes over China well, providing additional credibility to the improvements we have made to our agricultural NH3 emission inventory.

Comparison of Voltammetric Techniques for Ammonia Sensing in Ionic Liquids

AbstractIn electroanalytical chemistry, it is often observed that square wave voltammetry (SWV) and differential pulse voltammetry (DPV) are more sensitive techniques compared to linear sweep voltammetry (LSV), due to their method of sampling which minimises the charging current (non‐faradaic processes). In this work, a comparison of the three techniques (LSV, DPV and SWV) is performed for ammonia (NH3) gas oxidation (a chemically and electrochemically irreversible redox process) in an ionic liquid over a concentration range of 10–100 ppm. Four different platinum electrodes are employed: a screen‐printed electrode (SPE), a thin‐film electrode (TFE), a microarray thin‐film electrode (MATFE) and a Pt microdisk electrode (μ‐disk). Calibration plots (current vs concentration) for all three different electrochemical techniques on all four surfaces showed excellent linearity with increased concentrations of NH3 gas and relatively low limits of detection (LODs). On the larger mm‐sized surfaces (SPE and TFE), the current responses for LSV and SWV were quite similar, but DPV gave the lowest currents. Whereas for the smaller micron sized electrodes (MATFE and μ‐disk), currents were of the order LSV>SWV>DPV, with LSV being far superior to the pulse techniques. These findings suggest that the pulse techniques of SWV and DPV may not be the optimum methods, particularly on microelectrodes, for the detection of analytes such as ammonia in RTILs.

Enhanced NH3 gas-sensing performance of silica modified CeO2 nanostructure based sensors

The silica modified CeO2 gas sensing nanomaterials are synthesized using a sol-hydrothermal route. The 8%silica-CeO2 has larger specific surface areas of 83.75m2/g and smaller crystalline size of 11.5nm than pure CeO2, respectively. Compared to pure CeO2, the 8%silica-CeO2 based gas sensor exhibits significant enhancement NH3 gas-sensing performance. At room temperature, it shows much better gas response of 3244% to 80ppm of NH3 gas and lower detection limit (0.5ppm) towards NH3 gas. It is also found that the gas response of the NH3 gas sensors increases linearly with the increase of NH3 gas concentration. Moreover, the NH3 gas sensor have good reversibility, stability and selectivity. The reason of enhanced NH3 gas-sensing performance is not only because of the increased specific surface areas, but also due to the electrolytic conductivity of NH4+ and OH− on the surface.

Simple one-pot polyol synthesis of Pd nanoparticles, TiO2 microrods and reduced graphene oxide ternary composite for sensing NH3 gas at room temperature

Pd nanoparticles (Pd NPs), TiO2 microrods (TiO2 MRs) and reduced graphene oxide (RGO) ternary composite (Pd NPs/TiO2 MRs/RGO) film were fabricated by one-pot polyol, followed by annealing, to yield two morphologies of MRS and NPs. The NH3 gas-sensing properties of Pd NPs/TiO2 MRs/RGO film at room-temperature were investigated. The morphology, phase composition and crystalline structure of Pd NPs/TiO2 MRs/RGO ternary composite films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. Microstructural observations revealed that the Pd NPs and interconnected TiO2 MRs randomly adhered to the surface of RGO. Comparative gas sensing results revealed that the sensor that was based on the Pd NPs/TiO2 MRs/RGO ternary composite film responded much more strongly to NH3 gas at room temperature than did that based on TiO2 MRs and TiO2 MRs/RGO films, revealing the contribution of RGO and Pd NPs to NH3 gas-sensing capacity. Most importantly, the sensor that was made of the Pd NPs/TiO2 MRs/RGO ternary composite film responded strongly to low concentrations of NH3 gas at room temperature; its use is practical because of its ease of fabrication.

Analytical modelling of sensing performance of carbon nanotubes for gas sensing

Carbon nanotubes (CNTs) have recently captured attention as novel materials for nanoelectronic sensors due to their ability to achieve better sensitivity and accuracy in these devices. Up until now, the majority of investigations have focused on experimental studies for sensors. Therefore, there is lack of analytical models comparative to experimental investigations. The proposed model employs a CNT-based field effect transistor (CNT-FET) scheme to model the transport parameters of the CNT-based gas sensor. The CNT conductance is affected on exposure to the target analyte – NH3 gas molecules. The NH3 gas concentration is absorbed on the CNT surface after a chemical reaction between the CNT and NH3. This modulates the current-voltage (I-V) characteristics and conductance of the CNT-based gas sensor. The I-V characteristics of the CNT-based sensor have been proposed as a criterion to detect the effect of gas absorption. Finally, the proposed model was compared with experimental investigation for validation.

Analytical modelling of sensing performance of carbon nanotubes for gas sensing

Carbon nanotubes (CNTs) have recently captured attention as novel materials for nanoelectronic sensors due to their ability to achieve better sensitivity and accuracy in these devices. Up until now, the majority of investigations have focused on experimental studies for sensors. Therefore, there is lack of analytical models comparative to experimental investigations. The proposed model employs a CNT-based field effect transistor (CNT-FET) scheme to model the transport parameters of the CNT-based gas sensor. The CNT conductance is affected on exposure to the target analyte – NH3 gas molecules. The NH3 gas concentration is absorbed on the CNT surface after a chemical reaction between the CNT and NH3. This modulates the current-voltage (I-V) characteristics and conductance of the CNT-based gas sensor. The I-V characteristics of the CNT-based sensor have been proposed as a criterion to detect the effect of gas absorption. Finally, the proposed model was compared with experimental investigation for validation.

Miniature fiber-optic NH3 gas sensor based on Pt nanoparticle-incorporated graphene oxide

A highly sensitive ammonia (NH3) optical fiber sensor is demonstrated using platinum (Pt)-nanoparticle-incorporated graphene oxide (GO). The sensor was fabricated by coating a tapered microfiber multimode interferometer with Pt-decorated GO film. The sensing mechanism of the sensor was based on charge-transfer-induced refractive index changes in the GO: Pt nanoparticles which form an ideal assistant material can improve sensitivity remarkably for gas sensing. The experimental results show a sensitivity of 10.2pm/ppm with Pt nanoparticles which is three times higher than the sensitivity when coated with pure GO. These results indicate the sensor has the optimal sensing sensitivity when the Pt nanoparticle concentration is 185.2mg/L and exhibits a linear response with NH3 gas concentration below 80ppm. This composite film-based passive optical fiber sensor provides an approach for highly sensitive NH3 sensing in a limited space and flammable or explosive environment.

Simultaneous removal of ammonia and hydrogen sulfide gases using biofilter media from the biodehydration stage and curing stage of composting.

Biofiltration of NH3 and H2S with different packing media, biodehydration stage compost (BSC), and curing stage compost (CSC) was studied. Meanwhile, fluorescence excitation-emission matrix (EEM) spectroscopy was used to characterize the conversion mechanisms of organic matter during these biofiltration processes. Both biofilters were effective for the simultaneous removal of NH3 and H2S when inlet concentrations of NH3 and H2S were 0-50 and 50-250mg/m3, respectively. An abrupt increase in the inlet gas concentrations of NH3 and H2S to 100-150 and 200-250mg/m3, respectively, caused the decrease in the removal efficiencies (REs) of NH3 and H2S in the BSC biofilter, followed by a slow upturn. By contrast, relatively steady REs of both NH3 and H2S were observed in the CSC biofilter. After 60days of operation, the average REs of NH3 and H2S were more than 95% in the CSC biofilter. During the operation of CSC, nitrate and nitrite peaked around the 30th day, whereas sulfate showed a steady increase. The excitation-emission matrix fluorescence and parallel factor analysis (EEM-PARAFAC) indicated that the simultaneous inlet of NH3 and H2S facilitated the degradation of protein-like substances, whereas humic-like substances played an important role in the packing filters for the treatment of the two odorous pollutants.

Evaluating ammonia (NH3) predictions in the NOAA National Air Quality Forecast Capability (NAQFC) using in situ aircraft, ground-level, and satellite measurements from the DISCOVER-AQ Colorado campaign

The U.S. National Oceanic and Atmospheric Administration (NOAA) is responsible for forecasting elevated levels of air pollution within the National Air Quality Forecast Capability (NAQFC). The current research uses measurements gathered in the DISCOVER-AQ Colorado field campaign and the concurrent Front Range Air Pollution and Photochemistry Experiment (FRAPPE) to test performance of the NAQFC CMAQ modeling framework for predicting NH3. The DISCOVER-AQ and FRAPPE field campaigns were carried out in July and August 2014 in Northeast Colorado. Model predictions are compared with measurements of NH3 gas concentrations and the NH4+ component of fine particulate matter concentrations measured directly by the aircraft in flight. We also compare CMAQ predictions with NH3 measurements from ground-based monitors within the DISCOVER-AQ Colorado geographic domain, and from the Tropospheric Emission Spectrometer (TES) on the Aura satellite.In situ aircraft measurements carried out in July and August of 2014 suggest that the NAQFC CMAQ model underestimated the NH3 concentration in Northeastern Colorado by a factor of ∼2.7 (NMB = −63%). Ground-level monitors also produced a similar result. Average satellite-retrieved NH3 levels also exceeded model predictions by a factor of 1.5–4.2 (NMB = −33 to −76%). The underestimation of NH3 was not accompanied by an underestimation of particulate NH4+, which is further controlled by factors including acid availability, removal rate, and gas-particle partition. The average measured concentration of NH4+ was close to the average predication (NMB = +18%).Seasonal patterns measured at an AMoN site in the region suggest that the underestimation of NH3 is not due to the seasonal allocation of emissions, but to the overall annual emissions estimate. The underestimation of NH3 varied across the study domain, with the largest differences occurring in a region of intensive agriculture near Greeley, Colorado, and in the vicinity of Denver. The NAQFC modeling framework did not include a recently developed bidirectional flux algorithm for NH3, which has shown to considerably improve NH3 modeling in agricultural regions. The bidirectional flux algorithm, however, is not expected to obtain the magnitude of this increase sufficient to overcome the underestimation of NH3 found in this study. Our results suggest that further improvement of the emission inventories and modeling approaches are required to reduce the bias in NAQFC NH3 modeling predictions.

Measurements of NO2, SO2, NH3, HNO3 and O3 in West African urban environments

In this paper, we present the measurements of atmospheric gas concentrations of NO2, SO2, NH3, HNO3, and O3 performed at two traffic sites in the context of the POLCA (Pollution of African Capitals) program. These gases were measured using a passive sampling technique from Jan. 2008 to Dec. 2009 at Dakar and from Jun. 2008 to Dec. 2009 at Bamako. In addition, during these periods there were two intensive measurement campaigns (from 19 Jan. to 2 Feb. 2009 at Bamako and from 30 Nov. to 13 Dec. 2009 at Dakar) where real-time active analysers were used to measure NO2 and SO2. Results show that Dakar has a pollution level for NO2 and SO2 higher than that of Bamako, whereas it is lower for NH3 concentrations. Monthly values of NO2 range between 21.1 and 43.5 ppb in Dakar with an annual mean concentration of 31.7 ppb (59.6 μg/m3). NO2 values in Bamako are 9.4–22.6 ppb with a mean of 16.2 ppb. At Dakar, the mean annual NO2 limit value (21.3 ppb or 40 μg/m3) recommended by the World Health Organization (WHO) is widely exceeded. The mean annual concentration of SO2 is 15.9 ppb in Dakar and 3.6 ppb in Bamako. These differences may be explained by different sources of traffic between Bamako (with mainly gasoline vehicles) and Dakar (with mainly diesel vehicles). The annual mean NH3 concentration is about two times higher in Bamako (46.7 ppb) than in Dakar (21.1 ppb). In addition to other possible sources, we assume that the ammonia from domestic fires and uncontrolled garbage incineration may have more influence at Bamako than at Dakar. The mean annual concentrations of HNO3 and O3 are 1.3 ppb and 7.7 ppb in Dakar and 0.6 ppb and 5.1 ppb in Bamako, respectively. Seasonal variation in measured gas concentrations are low in Bamako and more pronounced in Dakar, except for HNO3 and NH3. At Dakar, NO2 and SO2 daily mean concentrations are higher during the weekdays than on weekends, when urban activities are reduced, whereas at Bamako, no significant difference was observed between weekdays and weekends. At Dakar, the daily average concentrations of SO2 in the dry season (11.6–39.6 ppb) widely exceed the WHO air quality guideline (7.6 ppb or 20 μg/m3 as 24-h average). Finally, the spatial distribution of gases at different sites in these two capitals have been investigated and showed higher pollution levels at the traffic sites, especially for NO2, NH3 and SO2, and lower levels in the suburban area, with the exception of ozone.

Aerobic treatment of liquid swine manure using polymer: Evaluation for ammonia emissions reduction and nitrogen retention

In the present study, the effectiveness of polymer (maleic-itaconic acid) on ammonia (NH3) emissions reduction and in retaining nitrogen (N) in fresh liquid swine manure (SM) was evaluated. The relationship between pH and NH3 emission was also determined. Different doses of polymer (namely Treatment 1 = T1 = 0.8 L polymer/ton of manure, Treatment 2 = T2 = 1.6 L polymer/ton of manure, Treatment 3 = T3 = 2.4 L polymer/ton of manure, and Treatment 4 = T4 = 3.2 L polymer/ton of manure) were added to the SM and its effects were observed for 30 d. The tests results showed significant reduction in pH for T1, T2, T3 and T4 compared to control (C). For the short term (up to 3d) T2, T3, and T4 showed significantly lower NH3 gas concentrations than C, however, for the long term (up to 10–20 d) only T4 continued to indicate significantly lower NH3 gas concentrations. Although numeric observations were reported for other treatments (T1, T2 and T3), no significant differences in NH3 gas concentrations were found. The NH3 emissions reductions were calculated in the range of 81–92%, 31–88%, −39–61%, 6–41%, −106% to −6% for the treatment period of 1, 3, 10, 20 and 30 d, respectively. The addition of polymer resulted in no significant difference in total ammonia nitrogen (TAN) and NO3−–N concentration. However, the addition of polymer had a significant influence on total Kjehldahl nitrogen (TKN) and soluble chemical oxygen demand (SCOD) concentration. The NH3 gas emissions strongly correlated with the manure pH (R2 = 0.911–0.999).

Carbon Nanotube Thin Films Functionalized via Loading of Au Nanoclusters for Flexible Gas Sensors Devices

Carbon nanotubes (CNTs) have been demonstrated to be one of the most interesting materials for gas sensing. This paper applies a simple method for the direct transfer of high-density CNTs from a SiO2/Si substrate to a flexible substrate for carbon dioxide (CO2), ammonia (NH3), and isopropyl alcohol gas sensing at room temperature. The flexible gas sensor exhibited high sensitivities of 4.8%, 5.4%, and 5.2% at room temperature for ambient CO2, NH3, and isopropyl alcohol gas concentrations of 800 ppm, respectively. In addition, the gas response of the CNT-based chemiresistor is attributed to p-type conductivity in the Au-modified semiconducting CNTs. Very good repeatability of the sensor response to gas concentration is demonstrated, representing a major step toward the low-cost large-scale production of this class of device.

Hierarchical graphene-polyaniline nanocomposite films for high-performance flexible electronic gas sensors.

A hierarchically nanostructured graphene-polyaniline composite film is developed and assembled for a flexible, transparent electronic gas sensor to be integrated into wearable and foldable electronic devices. The hierarchical nanocomposite film is obtained via aniline polymerization in reduced graphene oxide (rGO) solution and simultaneous deposition on flexible PET substrate. The PANI nanoparticles (PPANI) anchored onto rGO surfaces (PPANI/rGO) and the PANI nanofiber (FPANI) are successfully interconnected and deposited onto flexible PET substrates to form hierarchical nanocomposite (PPANI/rGO-FPANI) network films. The assembled flexible, transparent electronic gas sensor exhibits high sensing performance towards NH3 gas concentrations ranging from 100 ppb to 100 ppm, reliable transparency (90.3% at 550 nm) for the PPANI/rGO-FPANI film (6 h sample), fast response/recovery time (36 s/18 s), and robust flexibility without an obvious performance decrease after 1000 bending/extending cycles. The excellent sensing performance could probably be ascribed to the synergetic effects and the relatively high surface area (47.896 m(2) g(-1)) of the PPANI/rGO-FPANI network films, the efficient artificial neural network sensing channels, and the effectively exposed active surfaces. It is expected to hold great promise for developing flexible, cost-effective, and highly sensitive electronic sensors with real-time analysis to be potentially integrated into wearable flexible electronics.

NH3 gas sensor based on Pd/SnO2/RGO ternary composite operated at room-temperature

Novel room-temperature NH3 gas sensors based on Pd, tin oxide (SnO2) and reduced graphene oxide (RGO) ternary nanocomposite (Pd/SnO2/RGO) film were fabricated by the one-pot route. The Pd/SnO2/RGO ternary nanocomposite films were characterized by Fourier transform infrared spectroscopy (FTIR), Raman, X-ray diffractometry (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Microstructural observations revealed that the Pd and SnO2 nanoparticles easily and homogeneously attached to the surface of RGO. The sensor that was based on a Pd/SnO2/RGO ternary nanocomposite film responded strongly to low concentrations of NH3 gas at room-temperature. Its better sensor sensitivity than that of the pristine of SnO2 and SnO2/RGO nanocomposite film was related to the higher conductivity and catalytic activity of the Pd/SnO2/RGO ternary nanocomposite film.

Application of principal component analysis to gas sensing characteristics of Cr0.8Fe0.2NbO4 thick film array

The transient changes in resistances of Cr0.8Fe0.2NbO4 thick film sensors towards specified concentrations of H2, NH3, acetonitrile, acetone, alcohol, cyclohexane and petroleum gas at different operating temperatures were recorded. The analyte-specific characteristics such as slopes of the response and retrace curves, area under the curve and sensitivity deduced from the transient curve of the respective analyte gas have been used to construct a data matrix. Principal component analysis (PCA) was applied to this data and the score plot was obtained. Distinguishing one reducing gas from the other is demonstrated based on this approach, which otherwise is not possible by measuring relative changes in conductivity. This methodology is extended for three Cr0.8Fe0.2NbO4 thick film sensor array operated at different temperatures.