Ammonia Sensor Research Articles

Pristine and transition metal decorated holey graphyne monolayer as an ammonia sensor: insights from DFT simulations

The first-principles density functional theory method has been employed to comprehensively investigate adsorption configurations, adsorption energies, electronic properties, and gas sensing characteristics of pure and transition metal (TM = Sc, Pd, and Cu) decorated holey graphyne (HGY) monolayer for the detection of ammonia (NH3). The calculations reveal that the NH3 molecule weakly interacts with the pristine HGY surface with an adsorption energy of −0.146 eV. The expedited charge transfer and strong orbital hybridization between the NH3 molecule and the decorated TM (except Pd) resulted in the strong adsorption of the NH3 on the TM-decorated system. Among the three metals, it is found that the Sc decorated HGY can be regarded as the potential NH3 sensor owing to its reasonable adsorption energy of −1.49 eV, a large charge transfer of 0.113e, and an attainable recovery time of 3.2 s at 600 K. Furthermore, the stability of the Sc decorated HGY structure at ambient temperature is also validated using the ab initio molecular dynamic simulations. The results of the current study mirror the probable application of 2D HGY-based gas sensors for the detection of ammonia.

Humidity-activated ammonia sensor based on mesoporous AlOOH towards breath diagnosis

Discrimination and quantitation of ammonia (NH3) exhaled from human beings using oxide chemiresistors has shown great potential for non-invasive and direct diagnosis of helicobacter pylori gastropathy and end-stage renal disease. Herein, a newly humidity-activated sensor employing AlOOH that synthesized by a simple approach consisting of in-situ etching treatment and hydrothermal method is designed and demonstrated. The humidity-activated AlOOH sensor exhibits a high selectivity and response toward ppb-level of NH3 under 98 % relative humidity at room temperature, neglecting the water poisoning effect on gas-sensing characteristics. The enhanced adsorption of NH3 at abundant BrØnsted acid sites, and the effective ammonium ionic transmitting pathway induced by adsorbed moisture are proposed as the reasons behind the humidity-activated gas-sensing mechanism. Analysis using direct current analysis, complex impedance spectra and temperature programmed desorption (TPD) are performed to verify the above proposals. This study provides new pathway for rapid and stable detection of NH3 in human breath.

Plasma-Polymerized Thiophene-Reduced Graphene Oxide Composite Film Sensor for Ammonia/Amine Detection at Room Temperature

Industrialization has led to an increasing need for specific and selective gas sensors in the past few decades. Environmental monitoring of certain volatile compounds such as ammonia is necessary. Advancements in the food storage sector have created the need for cheap and effective amine chemosensors. Classical chemosensors still face several issues, such as a lack of selectivity and low sensitivity toward ammonia and amines. Sensitivity is defined as the relative change in response expressed in percentage. In this work, we have resolved a few issues associated with the ammonia and amine sensors, such as low selectivity, long-term instability, and unreliability under higher temperatures using plasma-polymerized thiophene (PPTh) reduced graphene oxide (rGO) composite films. PPTh films were prepared using RF plasma polymerization with optimized deposition parameters. Several samples were evaluated for their sensing response to understand the optimal PPTh and rGO ratio in the PPTh-rGO composite. These composite PPTh-rGO films have shown 4 times higher sensitivity for ammonia/amines than individual PPTh and rGO films. Ammonia, methylamine (MA), dimethylamine (DMA), and trimethylamine (TMA) were primary analytes and tested for sensing response of the PPTh-rGO composite. The sensitivity measured ranges from 1328 for trimethylamine to 2354 for methylamine at 1000 ppm. The order of sensitivity was found to be MA > Ammonia > DMA > TMA. Polymer swelling, reduced charge carriers, and disruption of conductive pathways can explain possible sensing mechanisms. PPTh-rGO composite films have shown selectivity as high as 110 for ammonia/amine over other commonly used volatile organic compounds. The sensing response of these films is stable for any temperature fluctuations from 30 °C to 150 °C. Additionally, films showed stable sensitivity for over 4 months. Thus, composite films of PPTh-rGO can be effectively used to develop highly selective and stable gas sensors for the environmental monitoring of ammonia/amines.

Разработка параметрической модели определения газового состава воздушной среды (аммиак, сероводород, углекислый газ) животноводческого помещения

Indoor climate parameters influence the productivity of animals and their physiological condition. Exceeding permissible concentrations of gases leads to animal diseases, loss of productivity, and the mortality of young cattle. Therefore, it is reasonable to predict the concentration of gas composition in the livestock houses. To determine and distribute harmful gases (ammonia, hydrogen sulphide, and carbon dioxide) in the livestock house, the authors performed the 3D modeling of a fragment of the farm in the SolidWorks 2020 software package. Parametric models of gas movement under different conditions were created and optimal measurement points of gas concentration in the livestock house were determined. The simulations made it possible to determine the direction of air flows and detect accumulations and clouds of gases. The maximum concentration of carbon dioxide was detected at 0.9m (an air speed of 0 m/sec) and at 1.3m (a speed of 0.75 m/sec). The highest concentration of hydrogen sulphide was found in the area bordering the ridge space (an air speed of 0 m/s) and at the level of 2.25 m (a speed of 2 m/s). The highest concentration of ammonia was observed under the roof and in the area under the ridge (an air speed of 2 m/s). It is recommended to install hydrogen sulphide and ammonia sensors under the ridge, while carbon dioxide, hydrogen sulphide and ammonia sensors – in the stall, carbon dioxide and hydrogen sulphide sensors – near the feed table. Concentrations should be measured at heights of 500, 1500, and 3000 mm. When the concentration of emitted gas increases and other conditions are equal, the concentration of gas in the cloud increases, but the structure of the cloud changes insignificantly. Parameter interrogation sensors should be installed in enclosed ventilated boxes in the same manner as in weather stations.

Thermosalient effect of a naphthalene diimide and tetrachlorocobaltate hybrid and changes of color and magnetic properties by ammonia vapor.

An organic-inorganic hybrid metal halide (OIMH), namely the electron-deficient naphthalene diimide (NDI) and [CoCl4]2- hybrid (1), showed potential as a sensor for ammonia and amines, in addition to magnetic changes upon vapochromism. Crystal 1 exhibited thermosalient behavior such as leaping and movement, at around 130 °C, which could be explained to be associated with the removal of water molecules from the crystal lattice as shown by TGA and DSC. Compound 1 changed from green to black within 5 minutes when exposed to ammonia vapor, which was attributed to the radical formation in the NDI moiety as evidenced by ESR, and this phenomenon was preserved even when other mono- and di-alkylamines were applied. The exposure of 1 to ammonia resulted in a subsequent color alteration, progressing from black to a gradually dark orange after one day (1_NH3_1 day). This transformation was concomitant with the formation of [Co(NH3)6]3+ from [CoCl4]2-, leading to a modification of the magnetic properties from paramagnetic Co(II) (S = 3/2) to diamagnetic Co(III) (S = 0). Based on these findings, compound 1 represents the first example of an OIMH that exhibits thermosalient behaviour, color change, and magnetic conversion upon exposure to ammonia.

Unique modulation effects on the performance of graphene-based ammonia sensors via ultrathin bimetallic Au/Pt layers and gate voltages.

Gas sensors with superior comprehensive performance at room temperature (RT) are always desired. Here, Au, Pt and Pt/Au-decorated graphene-based field effect transistor (FET) sensors for ammonia (denoted as Au/Gr, Pt/Gr and Pt/Au/Gr, respectively) are designed and fabricated. All these devices exhibited far better RT sensing performances for ammonia compared with graphene devices. Applying positive back gate voltages can further enhance their RT performance in which the Pt/Au/Gr devices show superior RT comprehensive performance such as a response of -16.2%, a recovery time of 4.6 min, and especially a much reduced response time of 54 s for 200 ppm NH3 with a detection limit of 103 ppb at a gate voltage of +60 V, and can be potentially tailored for further performance improvement by controlling the ratios of Pt and Au. The dependences of their performance on the gate voltage except for the response time could be reasonably explained by theoretical calculations in terms of the changes of the total density of states near the Fermi level, adsorption energies, transferred charges and adsorption distances. This study provides an effective solution for performance improvement of FET-based sensors via synergistic effects of ultrathin-layer multiple-metallic decoration and gate voltage, which would promote the exploration of novel sensors.

Highly sensitive ammonia sensor using newly synthesized carbazole based hypercrosslinked polymer and tin dioxide

Tin Dioxide (SnO2), carbazole based hypercrosslinked polymer (C-HCP), and C-HCP/SnO2 nanocomposites by different C-HCP weight percent concentration (0.05–0.15 %wt.) were synthesized by precipitation method and used as sensing materials for ammonia sensor. These materials were applied for ammonia detection in various temperature (100–350 °C) and ammonia concentration (100, 200, and 300 ppm). The electrical conductivity of materials was measured at different temperature and decreasing of electrical conductivity observed by temperature increasing. The resistance of sensor in air to that in presence of ammonia was considered as sensor response. According to the results, SnO2 had much greater conductivity than different concentration of C-HCP/SnO2 composite under same conditions. The results showed that in maximum sensor response with adding the C-HCP in SnO2, the optimum temperature decrease. The optimum temperature for SnO2 and 0.05, 0.1, and 0.15 %wt. of C-HCP in SnO2 composites was obtained 300 °C, 250 °C, 200 °C, and 150 °C, respectively. According to the results, the maximum sensor response observed 0.10 %wt. for ammonia detection at 200 °C. The 0.10 %wt. C-HCP in SnO2 based sensor showed a response three times higher than that by pure SnO2 in ammonia detection. Finally, the repeatability of sensors to the ammonia was obtained suitable in 3 continuous cycle and the response and reduction times of sensors was measured.

Guest Editorial: Materials & Devices for Advanced Flexible Sensors

The papers in this special section focus on materials and devices for flexible sensors. Presents recent advances in skin electronics, touch sensors for flexible display, near-infrared spectroscopy (NIRS) and organic electrochemical transistors (OECT), respectively. Three research article introduces new methods in flexible pressure sensing array, ammonia sensors and charge plasma junctionless tunnel field effect transistor (CP JLTFET), respectively.

An ion-selective chemiresistive platform as demonstrated for the detection of nitrogen species in water.

The use of ion-selective electrodes (ISE) is a well-established technique for the detection of ions in aqueous solutions but requires the use of a reference electrode. Here, we introduce a platform of ion-selective chemiresistors for the detection of nitrogen species in water as an alternative method without the need for reference electrodes. Chemiresistors have a sensitive surface that is prone to damage during operation in aqueous solutions. By applying a layer of ion-selective membrane to the surface of the chemiresistive device, the surface becomes protected and highly selective. We demonstrate both anion-selective (NO3-, NO2-) and cation-selective (NH4+) membranes. The nitrate sensors are able to measure nitrate ions in a range of 2.2-220 ppm with a detection limit of 0.3 ppm. The nitrite sensors respond between 67 ppb and 67 ppm of nitrite ions (64 ppb detection limit). The ammonium sensors can measure ammonium concentrations in a wide range from 10 ppb to 100 ppm (0.5 ppb detection limit). The fast responses to nitrate and nitrite are due to a mechanism involving electrostatic gating repulsion between negative charge carriers of the film and anions while ammonium detection arises from two mechanisms based on electrostatic gating repulsion and adsorption of ammonium ions at the surface of the p-doped chemiresistive film. The adsorption phenomenon slows down the recovery time of the ammonium sensor. This sensor design is a new platform to continuously monitor ions in industrial, domestic, and environmental water resources by robust chemiresistive devices.

Ppb-Level Ammonia Sensors Based on SnS2/rGO Nanohybrid Operating at Room Temperature

Ppb-Level Ammonia Sensors Based on SnS₂/rGO Nanohybrid Operating at Room Temperature

Room-temperature chemiresistive ammonia sensors based on 2D MXenes and their hybrids: recent developments and future prospects.

Detection of ammonia (NH3) gas at room temperature is essential in a variety of sectors, including pollution monitoring, commercial safety and medical services, etc. Two-dimensional (2D) materials have emerged as fascinating candidates for gas-sensing applications due to their distinct properties. MXenes, a type of 2D transition metal carbides/nitrides/carbonotrides, have drawn the interest of researchers due to their high conductivity, large surface area, and changing surface chemistry. The review begins by describing the NH3 gas-detecting methods of 2D materials and then concentrates on MXene-based sensors, emphasising the benefits that MXenes provide in this context. The study also explains the prime factors involved in evaluating sensor performance, which include sensor response, sensitivity, selectivity, stability, charge transfer values, adsorption energy and response/recovery times. Subsequently, the review covers two main categories: pristine/intercalated MXenes and MXene-based hybrid materials. The review investigates the approaches for improving the sensing characteristics of pristine and intercalated MXenes by introducing MXene hybrids like MXene-metal oxide hybrids, MXene-transition metal dichalcogenides hybrid, MXene-other 2D materials hybrid, MXene-polymers and other hybrids and other MXene-derived materials. In summary, this review offers a thorough overview of current advancements and potential applications for room-temperature ammonia sensors based on 2D MXenes and their hybrids. In order to pave the way for future improvements in MXene-based gas-sensing technology for room temperature ammonia detection, the study concludes by outlining potential future scope and conclusions.

Emerging poly(aniline co-pyrrole) nanocomposites by in-situ polymerized for high-performance flexible ammonia sensor

Emerging poly(aniline co-pyrrole) nanocomposites by in-situ polymerized for high-performance flexible ammonia sensor

High performance self-supported nickel oxalate/polyaniline electrode: a novel high sensitivity electrochemical ammonia sensor

High performance self-supported nickel oxalate/polyaniline electrode: a novel high sensitivity electrochemical ammonia sensor

Room Temperature Ammonia Sensing of MoS2 2D Sheets Decorated with Polyaniline (PANI)

Room Temperature Ammonia Sensing of MoS2 2D Sheets Decorated with Polyaniline (PANI)

High performance UV-LED activated gas sensors based on ordered carbon mesoporous materials loaded with ZnO nanoparticles

Carbon mesoporous materials (CMMs) with various ZnO loading concentrations have been fabricated as sensitive chemical sensors for nitrogen dioxide (NO2) and ammonia (NH3) detection. Mesostructured carbon with high surface area (>1000 m2/gr) is prepared using a template replication method, and zinc oxide (ZnO) nanoparticles are loaded through a facile solution impregnation. The sensors are operated at room temperature (∼25 °C) and activated by UV irradiation of a 365 nm wavelength and 25 mW/cm2 irradiance emitted from a UV-LED. SEM, TEM, XRD, XPS, and BET characterizations are carried out to study the physico-chemical properties of the prepared materials. The sensors with 57 wt% and 70 wt% ZnO loadings have exhibited superior gas sensing for the detection of NO2 and NH3, respectively. The maximum response values in optimal loading concentrations are 1.91 (NO2) and 1.35 (NH3), which are significantly higher than those of pristine ZnO nanoparticles reported previously. This improvement in response could be attributed to the high surface area, as well as the extended separation and restrained recombination rate of the photo-induced electron-hole pairs in ZnO/CMM sensing material. Furthermore, loading on CMMs produces more oxygen vacancies (OVac) induced by C-dopant, which increases the number of active sites and results in a large number of photo-induced oxygen ions on the surface, thus enhancing gas sensing activity.

Molecular Engineering of Silicon Phthalocyanine to Improve the Charge Transport and Ammonia Sensing Properties of Organic Heterojunction Gas Sensors

AbstractNovel organic heterostructures fabricated with a bilayer consisting of an axially substituted silicon phthalocyanine (R2‐SiPc) derivative and lutetium bis‐phthalocyanine (LuPc2) are investigated for their ammonia sensing properties. Surface and microstructure characterization of the heterostructure films reveal either compact or highly porous surface topography in (345F)2‐SiPc and Cl2‐SiPc‐based heterostructures, while electrical characterization reveals a strong influence of the axial substituent in R2‐SiPc on NH3 sensing capabilities. Electrical characterization further demonstrates an apparent energy barrier for interfacial charge transport, which is higher in the (345F)2‐SiPc/LuPc2 heterojunction device. In‐depth charge transport studies by impedance spectroscopy further reveal a resistive interface in (345F)2‐SiPc/LuPc2 and faster bulk and interfacial charge transport in Cl2‐SiPc/LuPc2 heterojunction devices. Different interfacial charge transport capabilities and surface topographies affect NH3 sensing properties of the two heterojunction devices, in which (345F)2‐SiPc/LuPc2 reveals a fast and non‐linear response with a limit of detection (LOD) of 310 ppb, while Cl2‐SiPc/LuPc2 exhibits a slow, and linear response to NH3 with LOD of 100 ppb. Finally, different metrological parameters of the two sensors are correlated to the respective gas‐material interactions, in which adsorption and diffusion regimes are modulated by the surface topography and hydrophobicity of the sensing layer.

Flexible room temperature sensor with modulation of polyaniline interfacial polymerization by CTAB for ppb-level ammonia detection

A highly selective and sensitive flexible room temperature ammonia (NH3) sensor was produced by in situ polymerizations of polyaniline (PANI) with modulation of Hexadecyl trimethyl ammonium Bromide (CTAB) on a porous Polyvinylidene fluoride film (PVDF). CTAB allows the PANI nanoparticles to grow uniformly on the surface and in the internal pores of the PVDF film, which increases the sensor’s response to the NH3. As a result, the sensor’s response values to 5 ppm NH3 and 0.01 ppm NH3 are 81.3 % and 4.6 % at 20 °C, respectively. The sensor also shows excellent selectivity for NH3 and maintains superior stability. Such a highly responsive and sensitive sensor is expected to be applied to detect chronic kidney disease.

Room temperature operable ultra-sensitive ammonia sensor based on polyaniline-silver (PANI-Ag) nanocomposites synthesized by ultra-sonication

This paper reports a novel, highly sensitive room temperature operable and reusable ammonia (NH3) gas sensor based on Polyaniline-silver nanocomposite (PANI-Ag). The nanocomposite was synthesized by in-situ, sonochemical oxidative polymerization methods by using ammonium persulphate. Aniline was used as a dispersant and stabilizer, D-glucose was chosen as an efficient reducing agent for the formation of Ag nanoparticles in the sol. The structural and optical properties of PANI-Ag nanocomposite were studied by FTIR spectroscopy, X- ray diffraction (XRD) and scanning electron microscopy (SEM). Morphological analysis of PANI-Ag nanocomposites revealed a cluster of PANI nanofibers with uniformly distributed silver nanoparticles having an average particle size of about 6 nm. The performance of PANI-Ag based sensor was evaluated at different concentrations of aqueous ammonia at room temperature. The sensor is highly sensitive at low ammonia concentration (less than 100 ppm). The sensor showed fast response and recovery time in the range of 30–120 s from 1 ppm to 100 ppm of ammonia concentration. The sensor showed an optimum response of 57% for 100 ppm ammonia. Due to excellent reversibility, reusability and long term environmental stability, PANI-Ag sensor provides a promising simple and efficient sensor system for wide-range ammonia concentration detection at room temperature.

Polyaniline/Graphene-Functionalized Flexible Waste Mask Sensors for Ammonia and Volatile Sulfur Compound Monitoring.

A flexible resistive-type polyaniline-based gas sensor was fabricated by simple dip-coating of graphene combined with in situ polymerization of aniline on a flexible waste mask substrate. The prepared polypropylene/graphene/polyaniline (PP/G/PANI) hybrid sensor demonstrated a fast response (114 s) and recovery time (23 s), ppb-level detection limit (100 ppb), high response value (250% toward 50 ppm NH3, which is over four times greater than that of the pristine PANI sensor), acceptable flexibility, excellent selectivity, and long-term stability at room temperature. The morphological and structural properties of the composite sensor materials were characterized by scanning electron microscopy and energy-dispersive spectroscopy characterization, and the surface chemistry of the hybrid sensors was analyzed by Fourier transform infrared spectroscopy. The excellent sensing performance was mainly ascribed to the larger specific surface area and efficient conducting paths of the porous PP/G/PANI network. Moreover, the PP/G/PANI hybrid gas sensor exhibited excellent sensing capability on volatile sulfur compounds contained in human breath, indicating that the hybrid sensor can be applied to breath analysis and kidney disease diagnosis.

Optical Ammonia-Sensing Probe Based on Surface-Plasmon Resonance of Silver-Nanoparticle-Decorated Superparamagnetic Dendritic Nanoparticles

Ammonia is a serious contaminant of aquaculture water due to its continuous release into the water environment during the biological processes of aquatic animals. Ammonia accumulation in water has negative environmental impacts, including eutrophication and the death of aquatic organisms. Therefore, sensitive and accurate determination of ammonia is an urgent need, especially in pisciculture systems. Here, we report the fabrication of a novel magnetic–hyperbranched nanomaterial-based ammonia-sensing probe for the fast and sensitive determination of ammonia in water. The proposed probe is composed of poly(amidoamine) (PAMAM)-coated superparamagnetic iron oxide nanoparticles (SPIONs) decorated with silver nanoparticles. Changing the ammonia concentration is associated with a corresponding change in the surface plasmon resonance property of silver nanoparticles. The proposed nanosystem was characterized with FTIR spectroscopy, SEM imaging, energy-dispersive X-ray (EDX) analysis, TEM imaging, X-ray diffractometry (XRD), and vibrating sample magnetometry (VSM). The TEM images showed a homogenous and uniform distribution of the nanoparticles with an average nanoparticle size of 200 nm, while the surface silver nanoparticles have an average particle size of 10–50 nm. The proposed optical ammonia sensor was successfully used to determine the concentration of ammonia in water samples by measuring the change in the solution absorbance at 428 nm. The obtained results revealed high recovery values (96.3–104.7%) and very low detection (LOD = 5.69 mg/L) and quantification (LOQ = 18.96 mg/L) limits. The standard plot is linear in the concentration range of 10–50 mg/L with an r2 value of 0.9980. Sandell’s sensitivity of the most promising sensor (NP-III) among the investigated systems was found to be 0.15 µg/cm2, which indicates high sensitivity.