Room Temperature Ammonia Research Articles

Highly responsive room-temperature ammonia sensing properties of MoS2/MoO3 nano-composite

Low dimensional MoS2/MoO3 nanocomposite was synthesized using a facile two-step method. In the first step, MoO3 was obtained using sol–gel approach. In the second step MoO3 was probe-sonicated and MoS2/MoO3 composite was obtained followed by a hydrothermal method. Raman spectroscopy established the various Raman modes corresponding to vibrations of various atoms in MoS2 and O-Mo-O bending and stretching modes related to MoO3. Further, successful ammonia sensing using two-terminal device at room-temperature established that nano-composite behaves like an n-type semiconducting materials. The sensor so obtained has nearly 62% relative response for 300 ppm of ammonia. Corresponding response and recovery times were found to be 73 s and 206 s, respectively. Complete recovery at room-temperature without any extra optical or thermal source was obtained. Further sensor device exhibited high reproducibility and superior selectivity behavior for 100-ppm ammonia. Present results suggest the potential use of MoS2/MoO3 composite as a room-temperature monitoring of ammonia.

MoS2/multiwalled carbon nanotubes based composite for room-temperature ammonia sensing

In past few years, two-dimensional transition metal dichalcogenides (TMDCs) with general formula MX2, where M is a transition metal (Mo, W or Ti) and X is a chalcogen (S, Se or Te) atom, have attracted significant attention in gas sensing applications due to their layered structure, semiconducting properties and superior responsivity at room-temperature. Multiwalled carbon nanotubes (MWCNT), on the other hand, have been used to enhance the gas sensing response of a base material. Herein, we report sensitive, selective and improved detection of ammonia by MoS2/MWCNTs composite as compared to MoS2 based two-terminal devices at room-temperature. A facile hydrothermal route was used to prepare MoS2/MWCNTs composite. An alumina substrate with pre-deposited gold contacts was used to make two-terminal devices. The resulting two-terminal devices have shown n-type semiconducting nature and high sensitivity/selectivity towards ammonia when compared with other reducing gases like hydrogen sulfide, formaldehyde and ethanol. Further, the composite based device shows faster response and recovery features compared to MoS2 and lower detection limit down to 10 ppm. Raman spectra from the sample indicated the presence of various Raman modes corresponding to vibrations of various atoms in MoS2 and D, G bands belonging to MWCNTs. Present results suggest that MoS2/MWCNTs composite can be employed for improved and selective ammonia gas monitoring at room-temperature.

Room-Temperature Hydrogen- and Ammonia Gas-Sensing Characteristics of a GaN-Based Schottky Diode Synthesized With a Hybrid Surface Structure

A GaN-based Schottky diode synthesized with a hybrid surface structure is used to fabricate a new room-temperature (25 °C) hydrogen and ammonia gas sensor. This hybrid surface structure includes platinum (Pt) nanoparticle (NP)/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanosphere (NS) mixtures and a Pt thin film. The employed hybrid surface structure can effectively increase the catalytic reactivity of the Pt metal and enhance the related gas-sensing characteristics. In the experiment, a higher sensing response of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7.3\times 10^{{5}}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.1\times 10^{{1}}{)}$ </tex-math></inline-formula> is obtained under 1% H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /air (1000 ppm NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /air) gas at 25 °C. Moreover, extremely low detecting levels of 100 ppb H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /air and 100 ppb NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /air are acquired at 25 °C. The related hydrogen- and ammonia-sensing mechanisms are elucidated in this work. For wireless transmission and Internet of Things (IoT) application, the Kalman filter and shape-preserving piecewise cubic interpolation (SPPCI) algorithms are employed to substantially reduce redundant data and restore original results. More than 86.7% (97%) of the original data points are removed with a small mean recovery error (MRE) of 3% (0.3%) under 1% H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /air (1000 ppm NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /air) gas at 25 °C.

Universal sensing of ammonia gas by family of lead halide perovskites based on paper sensors: Experiment and molecular dynamics

In this paper we show that, high sensitivity and high selectivity room temperature ammonia (NH3) gas sensors with both visual and electrical response can be made from family of lead halide perovskites with different cations and anions. These sensors, based on papers, act as general platforms for new generation of solid state gas sensors for sensitive detection of NH3 gas by simple color change (∼10 ppm sensitivity) as well as electrical resistance change with sub ppm sensitivity limited by electrical noise only. The sensors with materials like CH3NH3PbI3 (MAPI), CH3NH3PbBr3 (MAPB) and CH(NH2)2PbI3 (FAPI), are grown on paper from solution. MAPB changes color from orange to white and FAPI and MAPI from black to yellow under NH3 gas exposure respectively. For electrical sensor operation, a fixed concentration (20 ppm) of NH3 gas, the sensitivity of MAPI is highest at 96 % followed by MAPB at 82 % and FAPI at 65 %. The sensors with electrical read out could trace NH3 gas well below ppm level with only few nanowatt of power consumption. Based on experiments, a sensing mechanism has been proposed. The proposed mechanism mainly consists of decomposition of the perovskite halides to lead (Pb) halide by preferential adsorption of NH3 gas molecules. The proposed mechanism has also been substantiated by molecular dynamics simulations. These sensors fabricated by simple solution process on paper substrates and operable at ambient temperature, are compatible with very low power (∼ nW) paper electronics.

Room temperature ammonia gas sensor based on V2O5 nanoplatelets/Quartz crystal microbalance

In the present work, we report the deposition of vanadium pentoxide (V2O5) thin film on the quartz crystal microbalance (QCM) using vacuum thermal evaporation method followed by rapid thermal annealing (RTA) in oxygen atmosphere (O2),for gas sensing application. The structure, morphology and surface wettability of the obtained thin film were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurement (CA). The results show that the elaborated structure has a porous, rough and hydrophilic characteristic with a pure V2O5 phase in form of nanopaltelets. The sensing properties of V2O5 nanopaltelets /QCM structure were evaluated towards NH3 vapor at room temperature. The result revealed that the sensor exhibited good sensing performance: a fast response time, a short recovery time, good stability, reproducibility, reversibility and linearity.

Highly sensitive room temperature ammonia gas sensor using pristine graphene: The role of biocompatible stabilizer

Graphene has attracted extraordinary attention for gas sensing due to its large specific surface area as well as its high charge carrier mobility. Nonetheless, in most cases, graphene derivatives, such as reduced graphene oxide (rGO), were employed as sensing elements instead of pristine graphene. In this contribution, pristine graphene noncovalently functionalized by a biocompatible stabilizer (flavin monocleotide sodium salt, FMNS) was produced for the application as NH3 sensing materials in a chemiresistor type gas sensor. Detailed characterizations indicate that the graphene flakes exhibit good structural quality with few defects. The optimized ammonia sensors demonstrate outstanding performance: ultralow limit-of-detection (1.6 ppm), excellent sensitivity (2.8%, 10 ppm; 18.5%, 1000 ppm), reproducibility, reversibility, low power consumption (work temperature, 25 °C) as well as low cost. Additionally, the roles of FMNS from graphene preparation to NH3 sensing are elucidated via all-atom molecular dynamics simulations: (1) stabilizer for the graphene dispersion, (2) p-type dopant for graphene-based sensing element, and (3) active adsorption sites for NH3 gas sensing. This contribution provides an efficient strategy to design highly sensitive pristine graphene-based NH3 gas sensors utilizing FMNS-like molecules, involving a facile and environmentally friendly process, biocompatible materials, low cost equipment, and scale-up capability.

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.

3D printed CuO semiconducting gas sensor for ammonia detection at room temperature

In this work, a new room-temperature ammonia gas sensor based on n-type copper oxide (CuO) semiconductor was fabricated by 3D printing with fused deposition modeling (FDM) technique and sintering method. The polylactic acid (PLA) was blended together with Cu particles and extruded into the filament form for FDM printing. The PLA/Cu composite was printed and calcined in a furnace to obtain semiconducting CuO. The structural characterization results of 3D printed sensor showed monoclinic CuO phase and scaffold structures, which provided active porous sites for enhanced gas adsorption and room-temperature gas-sensing performances. According to gas-sensing data, the 3D printed CuO gas sensor exhibited good repeatability, high stability (>3 months), low humidity dependency (25–65 %RH), high sensitivity and selectivity towards ammonia at room temperature. The sensor response increased linearly with increasing NH3 concentration from 25 to 200 ppm. The sensing mechanism of the 3D printed CuO sensor was proposed based on the resistance change via reaction on adsorbed surface oxygen species or direct electron transfer between ammonia molecules and CuO. This approach could open up new ways to fabricate semiconductor gas sensors with controllable sizes and shapes for future gas-sensing applications.

High sensitive room temperature ammonia sensor based on dopant free m-WO3 nanoparticles: Effect of calcination temperature

High sensitive room temperature ammonia sensor based on dopant free m-WO3 nanoparticles: Effect of calcination temperature

Highly selective room temperature ammonia sensors based on ZnO nanostructures decorated with graphene quantum dots (GQDs)

This paper presents a highly selective ammonia sensor based on ZnO nanostructures combined with graphene quantum dots (GQDs). Novel graphene quantum dots (GQDs) have an average lateral size distribution of 2.6 nm. Various amounts of GQDs were combined with the ZnO nanostructure surfaces. Prior to the ZnO:GQDs investigation, field emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to intensively characterize the surface morphologies, existence of functional groups, and chemical compositions. ZnO:GQD heterojunctions are crucial candidate materials due to their highly selective response to ammonia (NH3) vapor. The ammonia sensing characteristics of bare ZnO and ZnO:GQDs sensors at room temperature were systematically investigated via exposure to acetone and ethanol vapor. The ammonia sensing results show that ZnO:GQDs sensors with a volume of 15 μL have optimum sensor responses at an ammonia concentration of 1000 ppm with a value of 6047. The ammonia sensing properties of ZnO:GQDs sensors are due to the GQDs’ carboxyl and hydroxyl groups, which produce more oxygen-containing groups leading to a high H+ molecule density. This further contributes to their highly responsive and selective performance for sensing ammonia at room temperature.

Effect of Cu2+ doping on the structural, optical, and vapor-sensing properties of ZnO thin films prepared by SILAR method

The Cu-doped ZnO thin films were fabricated on glass slides by a two-step SILAR coating method. The diffraction data revealed that the prepared ZnO:Cu films were in the phase of Wurtzite geometry, and the grain size decreases from 37 to 26 nm. The morphological studies revealed uniform distribution of nanograins as well as a nanoflower structure. The doping samples exhibited an increase in transmittance and an increase in the bandgap. A room temperature ammonia vapor-sensing performance of Cu-doped ZnO films is also studied, and sensitivity for sensing ammonia vapor is increased with doping concentration. The sensitivity was remarkably enhanced to 12,300% and it has a relatively fast response/recovery time of 37/8 s for 100 ppm NH3 for the 5 wt% of ZnO:Cu film. Its high sensitivity and fast response make the ZnO:Cu film a good contender for high-quality gas sensor devices.

Room temperature ammonia gas sensing characteristics of copper oxide-tin oxide composite thin films prepared by radio frequency magnetron sputtering technique

In this work, thin films of composite copper oxide-tin oxide [CuO:SnO2 (1:1)] were prepared by radio frequency magnetron sputtering technique at room temperature on quartz glass substrates. X-ray diffraction study revealed that the as-deposited films were amorphous in nature and the crystallinity of the films was obtained by annealing the films at 1000 °C. The hexagon rod-like structure, dews-like particles and cylindrical-shaped particles were observed in surface morphological study. The X-ray photoelectron spectroscopic study confirmed the formation of Cu2+ and Sn4+ states in the deposited films. The decrease in optical energy band gap with increase in RF power and annealing temperature may be due to the creation of localized states near the band edges of CuO:SnO2. The gas sensing characteristics of the films were analysed by recording the electrical resistance variation of the films in the presence/absence of various concentrations of NH3 gas at room temperature. The CuO:SnO2 film exhibited a highest sensing response of 3838 for 125 ppm of NH3 gas at room temperature. The film sustained its initial sensor response even after 6 months period for 5 repeated cycles, which ascertained the stability and repeatability of CuO:SnO2 thin film based gas sensor.

Hydrothermally synthesized MoS2-multi-walled carbon nanotube composite as a novel room-temperature ammonia sensing platform

MoS2 and its composite with multi-walled carbon nanotube (MWCNTs) were synthesized using facile hydrothermal approach. Structural and vibrational analysis revealed the presence of various defects in MoS2 and its composite with MWCNT. Two-terminal devices were made on a quartz substrate with pre-deposited silver contacts. The resulting Ag/MoS2/Ag and Ag/MoS2-MWCNT/Ag devices exhibit n-type semiconducting behavior and have shown room-temperature ammonia detection down to 12 ppm level. In case of former, the corresponding response time (tresponse = 400 s) and recovery time (trecovery = 280 s) are very large with limit of detection down to 1.2 ppm. The latter, i.e., Ag/MoS2-MWCNT/Ag device on the other hand exhibits faster response-recovery (65 and 70 s, respectively) features along with enhanced relative response for various ammonia concentrations ranging from 12 to 325 ppm. Further, the composite device also displays superior selectivity to its counterpart. It is argued that these differences might arise from different adsorption energy for different gas molecules on the surface of MoS2 or MoS2-MWCNT semiconducting channel. Present results suggest that composite materials such as MoS2-MWCNT may serve as a novel gas sensing platform with superior sensing characteristics and selectivity features.

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.

Correction to: Room temperature ammonia gas sensor using Nd-doped SnO2 thin films and its characterization

The original version of the article (https://doi.org/10.1007/s10854-020-03809-6) was unfortunately published with errors in Table 2 and Fig. 9a. These errors are corrected in this article. The corrected table and figure are given below.

Size controlled V2O5-WO3 nano-islands coated polypyrrole matrix: A unique nanocomposite for effective room temperature ammonia detection

Unique metal oxide nanomaterials represent prominent interest owing to their low cost, ease of fabrication and vast number of detectable gases in resistive based gas sensors. Unfortunately they are limited by their dependence of operating temperature, power consumption, poor sensitivity and deterioration of sensing material after continuous usage. To get the better of, conducting polymer polypyrrole has been widely used for fulfilling the requirement as ideal sensing material in sensing field due to its chemical stability, high electron affinity, controllable electrical conductivity and excellent room temperature operation. In this article, we report room temperature responsive ammonia gas sensing material PPy with V2O5 and WO3 developed by in situ chemical oxidation polymerization method. Characterizations carried out using the UV–vis, FTIR, XRD, XPS, SEM, HR-TEM, AFM analysis techniques. Physical and chemical analysis results reveal that the nanocomposite was synthesized successfully without other impurities. The morphological analysis exhibits that V2O5 and WO3 nanoparticles were wrapped and connected over PPy surface as nano islands provides enhanced sensing properties towards selectively NH3with ultrahigh sensitivity of 85 % with response time of 73 s and recovery time 101 s. The outstrip performance of gas sensing esteems were corresponds to the valid p-n heterojunctions of V2O5-WO3 and excellent surface effect of PPy.

Room temperature ammonia gas sensor using Nd-doped SnO2 thin films and its characterization

Nd-doped SnO2 thin films are prepared by the nebulizer spray pyrolysis method. The compositional and morphological studies are discussed. The X-ray diffraction reveals that the films are polycrystalline in nature. The grain size increases as the doping concentration of Nd increases. The x-axis orientation of the films is enhanced by Nd doping. The intensity of the miller indices (200) is enhanced due to doping. In the Raman spectrum, the doping concentration-dependent intensity is observed. The quenching is observed in the photoluminescence spectrum. The transmittance and the band gap of films have been decreased due to doping. The 5 wt% Nd-doped film shows the maximum response to ammonia.

Flexible room temperature ammonia gas sensor based on in suit polymerized PANI/PVDF porous composite film

Flexible room temperature sub-ppm ammonia (NH3) gas-sensing films based on polyaniline (PANI) nanoparticles were successfully developed on porous polyvinylidene fluoride (PVDF) substrate by in suit chemical oxidative polymerization method. The fabricated PANI/PVDF film sensor, which was synthesized with 0.1 mol/L aniline, possesses the best response value of 24.5% and 2.6% to 1 ppm and 0.1 ppm NH3 at room temperature, respectively. Furthermore, the PANI/PVDF film sensor shows excellent selectivity towards NH3 compared with methanol, ethanol, acetone, toluene, and formaldehyde at room temperature. The improved sensing performance is related to the porous PVDF nanostructure and synergetic effects of PVDF and PANI. Finally, the effect of working temperature and relative humidity on the sensing properties of the PANI/PVDF thin film sensor was also discussed and analyzed. The results show the potential application of the flexible PANI/PVDF film sensor for monitoring sub-ppm NH3 gas under ambient conditions.

Enhanced room temperature ammonia gas sensing properties of strontium doped ZnO thin films by cost-effective SILAR method

In this present work, pure and Sr doped ZnO films were systematically coated SILAR method is debated. The influence of Sr doping content on microstructure, surface morphology, elemental composition, photoluminescence and ammonia vapor sensing properties of these coated films were analyzed before and after incorporation of Sr. The effect of Sr doping revealed a change in crystal orientation from the (0 0 2) to the (1 0 1). SEM analysis reveals the formation of flower-like morphology formed by a number of nanowires with doping concentration. With the increase in Sr concentration, the bandgap values are increased from 3.02 to 3.20 eV. The addition of Sr also induces a rapid response towards ammonia gas sensing.

Room temperature ammonia gas sensor based on ionic conductive biomass hydrogels

Sensitive detection of ammonia (NH3) in exhaled human breath, may offer useful information for early diagnosis of kidney disease. Traditional chemical NH3 sensors usually suffer from ambient humidity. In this work, NH3 sensor operating under high humidity at 25 ℃ with enhanced response and selectivity has been achieved based on biomass hydrogel poly-l-glutamic acid and l-glutamic acid (PGA/GA). The response of the optimum PGA/GA sensor to 50 ppm NH3 at 80% relative humidity (RH) reaches 8.4, and the sensor can detect 0.5 ppm NH3. The special ionic conductive NH3 mechanism of the PGA/GA sensor was intensively studied by complex impedance plots and a quartz crystal microbalance. The high response, low detection limit, high stability and the non-toxic characteristics of biomaterials suggest PGA/GA sensors are promising for exhaled breath analyzer.