scholarly journals Evaluation of gas-sensing properties of ZnO nanostructures electrochemically doped with Au nanophases

2016 ◽  
Vol 7 ◽  
pp. 22-31 ◽  
Author(s):  
Elena Dilonardo ◽  
Michele Penza ◽  
Marco Alvisi ◽  
Cinzia Di Franco ◽  
Francesco Palmisano ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Gas Sensing ◽  
Low Cost ◽  
Sol Gel ◽  
Zno Nanostructures ◽  
Sensing Properties ◽  
Gas Sensing Properties ◽  
Zno Powders ◽  
One Step ◽  
Chemiresistive Gas Sensors

A one-step electrochemical method based on sacrificial anode electrolysis (SAE) was used to deposit stabilized gold nanoparticles (Au NPs) directly on the surface of nanostructured ZnO powders, previously synthesized through a sol–gel process. The effect of thermal annealing temperatures (300 and 550 °C) on chemical, morphological, and structural properties of pristine and Au-doped ZnO nancomposites (Au@ZnO) was investigated. Transmission and scanning electron microscopy (TEM and SEM), as well as X-ray photoelectron spectroscopy (XPS), revealed the successful deposition of nanoscale gold on the surface of spherical and rod-like ZnO nanostructures, obtained after annealing at 300 and 550 °C, respectively. The pristine ZnO and Au@ZnO nanocomposites are proposed as active layer in chemiresistive gas sensors for low-cost processing. Gas-sensing measurements towards NO2 were collected at 300 °C, evaluating not only the Au-doping effect, but also the influence of the different ZnO nanostructures on the gas-sensing properties.

scholarly journals Gas sensing properties of individual SnO2 nanowires and SnO2 sol–gel nanocomposites

2019 ◽  
Vol 10 ◽  
pp. 1380-1390 ◽  
Author(s):  
Alexey V Shaposhnik ◽  
Dmitry A Shaposhnik ◽  
Sergey Yu Turishchev ◽  
Olga A Chuvenkova ◽  
Stanislav V Ryabtsev ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Tin Dioxide ◽  
Gas Sensing ◽  
Sol Gel ◽  
Functional Materials ◽  
High Sensitivity ◽  
Sensor Response ◽  
Sensing Properties ◽  
Gas Sensing Properties ◽  
The Individual

This work is an investigation of the properties of semiconductor materials based on metal oxides, their catalytic properties, and their application as gas sensors, which were shown to exhibit high sensitivity, stability, and selectivity to target gases. The aim of this work is the comparison of gas sensing properties of tin dioxide in the form of individual nanowires and nanopowders obtained by sol–gel synthesis. This comparison is necessary because the traditional synthesis procedures of small particle, metal oxide materials seem to be approaching their limit. Because of this, there is increasing interest in the fabrication of functional materials based on nanowires, i.e., quasi-one-dimensional objects. In this work, nanocrystalline tin dioxide samples with different morphology were synthesized. The gas-transport method was used for the fabrication of well-faceted wire-like crystals with diameters ranging between 15–100 nm. The sol–gel method allowed us to obtain fragile gels from powders with grain sizes of about 5 nm. By means of X-ray photoelectron spectroscopy (XPS) it was proven that the nanowires contain considerably smaller amounts of hydroxy groups compared to the nanopowders. This leads to a decrease in the parasitic sensitivity of the sensing materials to humidity. In addition, we demonstrated that the nanowires are characterized by a nearly single-crystalline structure, ensuring higher stability of the sensor response due to the unlikelihood of sample recrystallization. The results from the ammonia detection experiments showed that the ratio of the sensor response to the surface area exhibits similar values for both the individual nanowire and nanopowders-based sensor materials.

One step synthesis of branched SnO2/ZnO heterostructures and their enhanced gas-sensing properties

2019 ◽  
Vol 281 ◽  
pp. 415-423 ◽  
Author(s):  
Xueli Yang ◽  
Sufang Zhang ◽  
Qi yu ◽  
Liupeng Zhao ◽  
Peng Sun ◽  
...  
Keyword(s):  
Gas Sensing ◽  
Sensing Properties ◽  
Gas Sensing Properties ◽  
One Step

scholarly journals Hydrophilicity and carbon chain length effects on the gas sensing properties of chemoresistive, self-assembled monolayer carbon nanotube sensors

2019 ◽  
Vol 10 ◽  
pp. 565-577 ◽  
Author(s):  
Juan Casanova-Cháfer ◽  
Carla Bittencourt ◽  
Eduard Llobet
Keyword(s):  
Carbon Nanotubes ◽  
Nitrogen Dioxide ◽  
Photoelectron Spectroscopy ◽  
Gas Sensing ◽  
Carbon Chain ◽  
Head Group ◽  
Carbon Chain Length ◽  
Sensing Properties ◽  
Gas Sensing Properties ◽  
Self Assembled

Here we describe the development of chemoresistive sensors employing oxygen-plasma-treated, Au-decorated multiwall carbon nanotubes (MWCNTs) functionalized with self-assembled monolayers (SAMs) of thiols. For the first time, the effects of the length of the carbon chain and its hydrophilicity on the gas sensing properties of SAMs formed on carbon nanotubes are studied, and additionally, the gas sensing mechanisms are discussed. Four thiols differing in the length of the carbon chain and in the hydrophobic or hydrophilic nature of the head functional group are studied. Transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy are used to analyze the resulting gas-sensitive hybrid films. Among the different nanomaterials tested, short-chain thiols having a hydrophilic head group, self-assembled onto Au-decorated carbon nanotubes were most responsive to nitrogen dioxide and ethanol vapors, even in the presence of ambient humidity. In particular, this nanomaterial was about eight times more sensitive to nitrogen dioxide than bare Au-decorated carbon nanotubes when operated at room temperature. This response enhancement is attributed to the interaction, via strong hydrogen bonding, of the polar molecules tested to the polar surface of hydrophilic thiols. The approach discussed here could be extended further by combining hydrophilic and hydrophobic thiol SAMs in Au-MWCNT sensor arrays as a helpful strategy for tuning sensor response and selectivity. This would make the detection of polar and nonpolar gas species employing low-power gas sensors easier, even under fluctuating ambient moisture conditions.

TUNGSTEN-DOPED TiO2 NANOLAYERS WITH IMPROVED CO2 GAS SENSING PROPERTIES FOR ENVIRONMENTAL APPLICATIONS

2017 ◽  
Vol 24 (Supp02) ◽  
pp. 1850024 ◽  
Author(s):  
MALIHEH SABERI ◽  
ALI AKBAR ASHKARRAN
Keyword(s):  
Electron Microscopy ◽  
Gas Sensing ◽  
Operating Temperature ◽  
Sol Gel ◽  
Optimum Operating ◽  
Optimum Operating Temperature ◽  
Sensing Properties ◽  
Vis Spectroscopy ◽  
Gas Sensing Properties ◽  
Tungsten Concentration

Tungsten-doped TiO2 gas sensors were successfully synthesized using sol–gel process and spin coating technique. The fabricated sensor was characterized by field emission scanning electron microscopy (FE-SEM), ultraviolet visible (UV–Vis) spectroscopy, transmission electron microscopy (TEM), X-Ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Gas sensing properties of pristine and tungsten-doped TiO2 nanolayers (NLs) were probed by detection of CO2 gas. A series of experiments were conducted in order to find the optimum operating temperature of the prepared sensors and also the optimum value of tungsten concentration in TiO2 matrix. It was found that introducing tungsten into the TiO2 matrix enhanced the gas sensing performance. The maximum response was found to be (1.37) for 0.001[Formula: see text]g tungsten-doped TiO2 NLs at 200[Formula: see text]C as an optimum operating temperature.

scholarly journals Discriminable Sensing Response Behavior to Homogeneous Gases Based on n-ZnO/p-NiO Composites

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 785 ◽  
Author(s):  
Wen-Dong Zhou ◽  
Davoud Dastan ◽  
Jing Li ◽  
Xi-Tao Yin ◽  
Qi Wang
Keyword(s):  
Gas Sensors ◽  
Gas Sensing ◽  
Sol Gel ◽  
High Sensitivity ◽  
Oxide Semiconductor ◽  
Sensing Properties ◽  
Gas Sensing Properties ◽  
P Type ◽  
Type Response ◽  
Properties Of Composites

Metal oxide semiconductor (MOS) gas sensors have the advantages of high sensitivity, short response-recovery time and long-term stability. However, the shortcoming of poor discriminability of homogeneous gases limits their applications in gas sensors. It is well-known that the MOS materials have similar gas sensing responses to homogeneous gases such as CO and H2, so it is difficult for these gas sensors to distinguish the two gases. In this paper, simple sol–gel method was employed to obtain the ZnO–xNiO composites. Gas sensing performance results illustrated that the gas sensing properties of composites with x > 0.425 showed a p-type response to both CO and H2, while the gas sensing properties of composites with x < 0.425 showed an n-type response to both CO and H2. However, it was interesting that ZnO–0.425NiO showed a p-type response to CO but an discriminable response (n-type) to H2, which indicated that modulating the p-type or n-type semiconductor concentration in p-n composites could be an effective method with which to improve the discriminability of this type of gas sensor regarding CO and H2. The phenomenon of the special gas sensing behavior of ZnO–0.425NiO was explained based on the experimental observations and a range of characterization techniques, including XRD, HRTEM and XPS, in detail.

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