Selective Ammonia Gas Sensor Research Articles

Highly selective ammonia gas sensor at room temperature based on MoO3/MWCNT-9 nanocomposites

Herein, a resistive gas sensor based on Molybdenum tri oxide (MoO3)/ 9 % mass fraction of multi-walled carbon nanotubes (MWCNTs-9) nanocomposites was developed by hydrothermal method to detect NH3 gas at room temperature. According to the findings, outstanding resistance change rate of 187.5 % was observed in MoO3/MWCNT-9 sensor when exposed to 100 ppm NH3 at room temperature (25 °C). In contrast, 8.2 % response rate was recorded for pure MoO3 sensor when exposed to same condition and the response value of newly fabricated sensor was improved by about 22.9 times to unalloyed MoO3. In addition, the nanocomposite sensor consisting of MoO3/MWCNT-9 had demonstrated excellent selectivity, repeatability, and a high level of sensitivity in detecting low concentrations of NH3 at low temperature. During experiment when the sensor desorbed NH3 gas at room temperature, a certain instantaneous voltage was applied, which greatly reduces the sensor’s resistance recovery time to 90 s. MWCNTs’s doping decreased the operating temperature of MoO3 and showed good gas sensitivity at room temperature. Finally, the results reveal that MoO3/MWCNT-9 nanocomposite-based sensor can be fruitful in the field of NH3 monitoring.

Exploring the NH3 gas sensing efficiency of polyvinylpyrrolidone based tungsten trioxide (PVP/WO3) Nanocomposites: A recent progression in the toxic gas sensing materials

In this paper, a room temperature operable, highly reproducible, stable and selective ammonia gas sensor of PVP, WO3, and PVP/WO3 nanocomposites were investigated. Drop casting method was used to deposit the sensing materials on interdigitated copper electrode. Chemical reduction and ultrasonication methods were adopted for the preparation of WO3 and PVP/WO3 nanocomposites, respectively. The as-produced sensing materials were characterized by using FTIR, XRD, and SEM techniques. LCR meter was used to analyze the gas sensing properties of PVP, WO3 and PVP/WO3 (5–25 wt%) nanocomposites. Under same condition of temperature (300 K), humidity (40%RH), and NH3 vapors (100 ppm) the sensor based on PVP/WO3 20 wt% showed higher sensing response of 87.26 as compared to pure PVP and WO3 nanosheets sensor which was 15.36 and 3.37, respectively. The PVP/WO3 20 wt% based sensor exhibited excellent results in term of reproducibility, stability (90 days), response time (14 s), and recovery time (10 s).

Highly sensitive and selective ammonia gas sensor based on FAPbCl3 lead halide perovskites

We report gas sensors based on formamidinium lead chloride (FAPbCl3), which demonstrate a strong and outstandingly selective response towards ammonia due to the specific interaction of the halide vacancies with NH3.

Selective room temperature ammonia gas detection using 2-amino pyridine functionalized graphene oxide

A stable and selective ammonia gas sensor has been prepared using 2-amino pyridine functionalized Graphene oxide (GO). The GO and functionalized GO was characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, Scanning electron microscopy & Energy dispersive X-ray spectroscopy. The sensing film was prepared by drop casting the amide functionalized GO on SiO2/Si substrate. Aluminum contacts were made on the sensor device for electrical measurement. The prepared sensor response was investigated for different concentrations of ammonia gas varied from 50 ppm to 900 ppm. The value of sensor response observed at low concentration (i.e. at 50 ppm) and at high concentration (i.e. 900 ppm) was 8.5% & 55.6% respectively. The sensor device showed good response time (~20s) & recovery time (~120s). The sensor also exhibited good selectivity and stability towards ammonia gas.

Nanorod like NiCo2O4 nanostructure for high sensitive and selective ammonia gas sensor

Ammonia gas sensors that work at room temperature are of immediate requirement to monitor the environmental safety of human beings and other living organisms. In the present study, we report the room temperature ammonia-sensing performances of Co3O4 and NiCo2O4 nanoparticles. The hydrothermally prepared samples were characterized using various sophisticated techniques in order to investigate the crystal structure, phase purity, morphology, elemental and chemical composition. The as prepared samples displayed selectivity against the ammonia gas and the NiCo2O4 nanorod-like sample exhibited superior sensing performances at room temperature.

Ambient temperature selective ammonia gas sensor based on SnO2-APTES modifications

In order to deal with the well-known lack of selectivity of SnO2 based gas sensors, the functionalization of SnO2 was performed. Liquid silanization by 3-aminopropyltriethoxysilane (APTES) was used as an intermediate step, followed by functionalization with molecules bearing acyl chloride with alkyl or ester end functional groups. Modified sensors with APTES, alkyl and ester end functional groups were successfully characterized by Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR). No response was observed for APTES and alkyl modified SnO2 sensors to ammonia gas at room temperature while the SnO2 sensor modified with ester end group was found to be sensitive and selective to ammonia gas at room temperature. This implies that the response is generated by ester functional groups. Working at low temperature is also one of the advantages of these sensors as well as the selectivity with respect to other gases like acetone and ethanol.

Selective Ammonia Gas Sensor based on SnO2-APTES Modification

In the present work, SnO2 sensors were produced by thick film fabrication. In order to deal with well-known lack of selectivity of SnO2 sensors, functionalization was performed. Silanization by 3-aminopropyltriethoxysilane (APTES) in liquid phase was used as an intermediate step, followed by functionalization with molecules bearing acyl chloride with different end functional groups molecules, for example ester group. Modified sensors with APTES and ester end functional group were successfully characterized by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The SnO2 sensor modified with ester end group was found to be sensitive and selective to ammonia gas at 100̊C. Working at low temperature is also one of the advantages of these sensors as well as the selectivity with respect to other gases like acetone.

Polytungstate clusters on zirconia as a sensing material for a selective ammonia gas sensor

Tungstated-zirconia has been tested as a functional material for a selective ammonia gas sensor. The sensor has been found to respond consistently and rapidly to changes in concentration of ammonia in the oxygen rich and moist gas mixture at 673 K. The sensor showed negligible cross-sensitivity to propene, CO, and NO. From characterizations of tungstated-zirconia by XRD, Raman, UV–vis, high-resolution TEM, and ammonia-TPD, it was found that subnano-sized polytungstate clusters are uniformly supported on the zirconia surface, and the strong acid sites derived from the polytungstate clusters are suggested to effectively work as selective adsorption sites for ammonia. The fabricated ammonia sensor utilizing tungstated-zirconia is expected to be useful for controlling the injection amount of ammonia in urea-SCR systems.

A highly selective ammonia gas sensor using surface-ruthenated zinc oxide

Preparation and characterisation of a highly selective surface-ruthenated zinc oxide sensor for ammonia in trace levels is demonstrated. The introduction of some RuO linkages on the surface of ZnO leads to a dramatic enhancement in the sensitivity ( S) to 1000 ppm level of ammonia at 300°C ( S=440) as compared to the similar response obtained for pure ZnO ( S=1.5). A systematic study using various characterisation techniques such as EDAX, SEM, CV and XPS indicates the key role played by the amount and distribution of Ru species on the surface.