•2D nanostructured rGO/WS2 heterojunctions has been successfully synthesized by one-step hydrothermal methods.•The rGO/WS2 based chemiresitive-type sensor shows an excellent sensitivity, selectivity ...and stability to 10–50 ppm NH3 at room temperature.•The enhanced sensitivity was attributed to the introduced hydroxyls by rGO nanosheets and extra acid centers by WS2 nanoflakes.
Hybrid of the two dimensional nanostructured reduced graphene oxide (rGO) and WS2 has been investigated for a room temperature ammonia sensor. The formed rGO/WS2 heterojunctions prepared by one-step hydrothermal synthesis indicated a good sensitivity to different concentrations of ammonia from 10 ppm to 50 ppm at room temperature. The WS2 nanoflakes doped in the heterojunction plays significant role in the enhanced response through the introduction of more hydroxyls in rGO and the extra Lewis acid active centers. The sensor also shows an excellent selectivity to NO2, alcohols, formaldehyde, acetone and benzene and a good long term stability indicating a potential to be employed as a room temperature NH3 sensor.
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•The photo-energy actived gas sensor was developed for the detection of NO2 by using the SnS2 nanosheets as the gas sensing material.•The gas sensor exhibits a high response and an ...excellent selectivity to 8 ppm NO2 under the green light illumination at room temperature.•The intrinsic mechanism of the SnS2 based sensor could be attributed to the photo-generated electron-hole pairs.
The visible-light activated gas sensor has been successfully fabricated for detecting NO2 by using two dimensional (2D) structured SnS2 nanosheet as the chemiresistive sensing material. Under the light illumination, the SnS2 nanosheet based chemiresistive gas sensor exhibits a high response and excellent selectivity to NO2 at room temperature. Influences of light wavelength, light intensity, operating temperatures and humidity on the sensing characteristics are investigated in details. It suggests that photo-energy activation can effectively activate the SnS2 sensor and the green light is the most effective to achieve superior sensing property of the SnS2 sensor at room temperature in terms of the excellent sensitivity and a better response/recovery speeds. The sensor also demonstrated an excellent selectivity to NO2 over several possible interferants such as SO2, CO2, NH3, acetone, methanol, ethanol and formaldehyde, and a good stability for about six months activated by the green light. The sensing mechanism is intimately related to the extra photo-generated electrons which subsequently attract more NO2 at its 2D surface. A simple Langmuir - Hinshelwood dynamics model is proposed to explain the effect of the visible light irradiation on the absorption/desorption speed of gas molecules.
Obituary for Prof. Dr. Alexander Gaskov Rumyantseva, Marina N; Vasiliev, Roman B
Sensors (Basel, Switzerland),
04/2021, Letnik:
21, Številka:
9
Journal Article
Recenzirano
Odprti dostop
Professor Alexander Gaskov, our dear colleague, friend and teacher, passed away on January 18, 2021 from COVID-19 ....
•One dimensional BaSnO3 microtubes were prepared via electrospining method.•The sample exhibited excellent selectivity of 14.4 to 1000 ppm acetic acid at 245 °C.•The detection limit for acetic acid ...was about 0.3 ppm.
In this paper, BaSnO3 microtubes were prepared via electrospinning method using Ba(NO3)2 and SnCl4·5H2O as raw materials. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), respectively; the gas sensing properties of the as-prepared sample were also investigated. The results revealed that BaSnO3 microtubes could be obtained by calcining the precursor at 700 °C for 6 h. It was revealed that the sensor device based on BaSnO3 microtubes (700 °C, 6 h) exhibited excellent selectivity and high response toward acetic acid vapor at the operating temperature of 245 °C, the ratio of S1000 ppm acetic acid to S1000 ppm ethanol was about 14.4; especially, when the concentration of acetic acid was as low as 0.3 ppm, the response was still able to reach 1.4.
In this work, MXene/NiO-composite-based formaldehyde (HCHO) sensing materials were successfully synthesized by an in situ precipitation method. The heterostructures between the MXene and NiO ...nanoparticles were verified by transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The HCHO sensing performance of the MXene/NiO-based chemiresistive-type sensors was investigated. Compared to pure MXene and NiO materials, the sensing performance of the MXene/NiO-P2-based sensor to HCHO gas at room temperature was significantly enhanced by the formation of MXene/NiO heterojunctions. The response of the MXene/NiO-P2 sensor to 50 ppm HCHO gas was 8.8, which was much higher than that of the pure MXene and NiO. At room temperature, the detectable HCHO concentration of the MXene/NiO-P2-based sensor was 1 ppm, and the response and recovery time to 2 ppm HCHO was 279 s and 346 s, respectively. The MXene/NiO-P2 sensor also exhibited a good selectivity and a long-term stability to HCHO gas for 56 days. The in situ Fourier transform infrared (FTIR) spectra of the MXene/NiO-P2 sensor, when exposed to HCHO gas at different times, were investigated to verify the adsorption reaction products of HCHO molecules.
Novel ZnSe/NiO heterostructure nanocomposites were successfully prepared by one-step hydrothermal method. The ZnSe/NiO-based sensor exhibits a response of ~ 96.47% to 8 × 10
−6
NO
2
at 140 °C, which ...is significantly higher than those of intrinsic ZnSe-based (no response) and NiO-based (~ 19.65%) sensors. The theoretical detection limit (LOD) of the sensor is calculated to be 8.91 × 10
−9
, indicating that the sensor can be applied to detect the ultralow concentrations of NO
2
. The effect of NiO content on the gas-sensing performance of the nanocomposites was investigated in detail. The optimal NiO content in the nanocomposite is determined to be 15.16% to achieve the highest response. The as-fabricated sensor also presents an excellent selectivity to several possible interferents such as methanol, ethanol, acetone, benzene, ammonia and formaldehyde. The enhanced sensing performance can be attributed to the formation of p–p heterostructures between ZnSe and NiO, which induces the charge transfer across the interfaces and yields more active sites.
Layered Au/SnS2 nanosheet based chemiresistive-type sensors were successfully prepared by using an in situ chemical reduction method followed by the hydrothermal treatment. SEM and XRD were used to ...study the microscopic morphology and crystal lattice structure of the synthesis of Au/SnS2 nanomaterials. TEM and XPS characterization were further carried out to verify the formation of the Schottky barrier between SnS2 nanosheets and Au nanoparticles. The as-fabricated Au/SnS2 nanosheet based sensor demonstrated excellent sensing properties to low-concentrations of NO2, and the response of the sensor to 4 ppm NO2 at 120 °C was approximately 3.94, which was 65% higher than that of the pristine SnS2 (2.39)-based sensor. Moreover, compared to that (220 s/520 s) of the pristine SnS2-based sensor, the response/recovery time of the Au/SnS2-based one was significantly improved, reducing to 42 s/127 s, respectively. The sensor presents a favorable long-term stability with a deviation in the response of less than 4% for 40 days, and a brilliant selectivity to several possible interferents such as NH3, acetone, toluene, benzene, methanol, ethanol, and formaldehyde. The Schottky barrier that formed at the interface between the SnS2 nanosheets and Au nanoparticles modulated the conducting channel of the nanocomposites. The “catalysis effect” and “spillover effect” of noble metals jointly improved the sensitivity of the sensor and effectively decreased the response/recovery time.
Composites of WS2 nanotubes (NT‐WS2) and gold nanoparticles (AuNPs) were prepared using aqueous HAuCl4 solutions and subjected to surface analysis. The obtained materials were jointly characterized ...by X‐ray photoelectron (XPS), Raman scattering (RSS), and ultraviolet photoelectron (UPS) spectroscopies. Optical extinction spectroscopy and electron energy loss spectroscopy in the scanning transmission electron microscopy regime (STEM‐EELS) were also employed to study plasmon features of the nanocomposite. It was found that AuNPs deposition is accompanied by a partial oxidative dissolution of WS2, whereas Au‐S interfacial species could be responsible for the tight contact of metal nanoparticles and the disulfide. A remarkable sensitivity of n‐type resistance of NT‐WS2 and Au‐NT‐WS2 to the adsorption of NO2 gas was also demonstrated at room temperature using periodical illumination by a 530 nm light‐emitting diode. Au‐NT‐WS2 nanocomposites are found to possess a higher photoresponse and enhanced sensitivity in the 0.25–2.0 ppm range of NO2 concentration, as compared to the pristine NT‐WS2. This behaviour is discussed within the physisorption‐charge transfer model to explore sensing properties of the nanocomposites.
Go for gold: The study sheds light on the mechanism of WS2 nanotube (NT‐WS2) decoration with Au nanoparticles by a direct interaction of disulfide with HAuCl4 solutions (see graphics) and revealed the optoelectronic features of the obtained nanocomposites. Au‐NT‐WS2 nanocomposites possess higher photoresponse and enhanced n‐type photoresistive sensitivity, as compared to the pristine NT‐WS2.
Increasing requirements for environmental protection have led to the need for the development of control systems for exhaust gases monitored directly at high temperatures in the range of 300-800 °C. ...The development of high-temperature gas sensors requires the creation of new materials that are stable under these conditions. The stability of nanostructured semiconductor oxides at high temperature can be enhanced by creating composites with highly dispersed silicon carbide (SiC). In this work, ZnO and SiC nanofibers were synthesized by electrospinning of polymer solutions followed by heat treatment, which is necessary for polymer removal and crystallization of semiconductor materials. ZnO/SiC nanocomposites (15-45 mol % SiC) were obtained by mixing the components in a single homogeneous paste with subsequent thermal annealing. The composition and microstructure of the materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The electrophysical and gas sensing properties of the materials were investigated by in situ conductivity measurements in the presence of the reducing gases CO and NH
(20 ppm), in dry conditions (relative humidity at 25 °C RH
= 0) and in humid air (RH
= 30%) in the temperature range 400-550 °C. The ZnO/SiC nanocomposites were characterized by a higher concentration of chemisorbed oxygen, higher activation energy of conductivity, and higher sensor response towards CO and NH
as compared with ZnO nanofibers. The obtained experimental results were interpreted in terms of the formation of an n-n heterojunction at the ZnO/SiC interface.
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