Regulation of specific surface area of 3D flower-like WO3 hierarchical structures for gas sensing application

Since MXene (a two-dimensional material) was discovered in 2011, it has been favored in all aspects due to its rich surface functional groups, large specific surface area, high conductivity, large porosity, rich organic bonds, and high hydrophilicity. In this paper, the preparation of MXene is introduced first. HF etching was the first etching method for MXene; however, HF is corrosive, resulting in the development of the in situ HF method (fluoride + HCl). Due to the harmful effects of fluorine terminal on the performance of MXene, a fluorine-free preparation method was developed. The increase in interlayer spacing brought about by adding an intercalator can affect MXene’s performance. The usual preparation methods render MXene inevitably agglomerate and the resulting yields are insufficient. Many new preparation methods were researched in order to solve the problems of agglomeration and yield. Secondly, the application of MXene-based materials in gas sensors was discussed. MXene is often regarded as a flexible gas sensor, and the detection of ppb-level acetone at room temperature was observed for the first time. After the formation of composite materials, the increasing interlayer spacing and the specific surface area increased the number of active sites of gas adsorption and the gas sensitivity performance improved. Moreover, this paper discusses the gas-sensing mechanism of MXene. The gas-sensing mechanism of metallic MXene is affected by the expansion of the lamellae and will be doped with H2O and oxygen during the etching process in order to become a p-type semiconductor. A p-n heterojunction and a Schottky barrier forms due to combinations with other semiconductors; thus, the gas sensitivities of composite materials are regulated and controlled by them. Although there are only several reports on the application of MXene materials to gas sensors, MXene and its composite materials are expected to become materials that can effectively detect gases at room temperature, especially for the detection of NH3 and VOC gas. Finally, the challenges and opportunities of MXene as a gas sensor are discussed.

Download Full-text

W-Sn Mixed Oxides and ZnO to Detect NOx and Ozone in Atmosphere

Proceedings ◽

10.3390/proceedings2130836 ◽

2018 ◽

Vol 2 (13) ◽

pp. 836

Author(s):

Ambra Fioravanti ◽

Sara Morandi ◽

Alessia Amodio ◽

Mauro Mazzocchi ◽

Michele Sacerdoti ◽

...

Keyword(s):

Zinc Oxide ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Mixed Oxides ◽

Gas Sensing ◽

Molar Fraction ◽

Functional Materials ◽

X Ray Diffraction ◽

X Ray

Thick films of zinc oxide (ZnO) in form of nanospheres or hexagonal prisms and of tungsten-tin (W-Sn) mixed oxides at nominal Sn molar fraction (0.1, 0.3 and 0.5) were prepared. The functional materials were synthesized and characterized by SEM and TEM, X-ray diffraction, specific surface area measurements, UV-Vis-NIR and IR spectroscopies. The gas sensing measurements highlighted that ZnO is more performant in form of nanoprisms, while W-Sn sensors offer a better response towards NOx and ozone with respect to pure WO3.

Download Full-text

Surface Structure Engineering of Nanosheet-Assembled NiFe2O4 Fluffy Flowers for Gas Sensing

Nanomaterials ◽

10.3390/nano11020297 ◽

2021 ◽

Vol 11 (2) ◽

pp. 297

Author(s):

Xiaofeng Wang ◽

Xu Li ◽

Guozheng Zhang ◽

Zihao Wang ◽

Xue-Zhi Song ◽

...

Keyword(s):

Specific Surface ◽

Surface Structure ◽

Surface Area ◽

Specific Surface Area ◽

Photoelectron Spectroscopy ◽

Gas Sensing ◽

Nitrogen Adsorption ◽

X Ray ◽

Adsorption Desorption ◽

Sensing Performance

In this work, we present a strategy to improve the gas-sensing performance of NiFe2O4 via a controllable annealing Ni/Fe precursor to fluffy NiFe2O4 nanosheet flowers. X-ray diffraction (XRD), a scanning electron microscope (SEM), nitrogen adsorption–desorption measurements and X-ray photoelectron spectroscopy (XPS) were used to characterize the crystal structure, morphology, specific surface area and surface structure. The gas-sensing performance was tested and the results demonstrate that the response was strongly influenced by the specific surface area and surface structure. The resultant NiFe2O4 nanosheet flowers with a heating rate of 8 °C min−1, which have a fluffier morphology and more oxygen vacancies in the surface, exhibited enhanced response and shortened response time toward ethanol. The easy approach facilitates the mass production of gas sensors based on bimetallic ferrites with high sensing performance via controlling the morphology and surface structure.

Download Full-text

Study on the Enhanced Specific Surface Area of Mesoporous Titania by Annealing Time Control: Gas Sensing Property

Journal of the Microelectronics and Packaging Society ◽

10.6117/kmeps.2015.22.2.021 ◽

2015 ◽

Vol 22 (2) ◽

pp. 21-26 ◽

Cited By ~ 1

Author(s):

M.-H. Hong ◽

Ch.-S. Park ◽

H.-H. Park

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Annealing Time ◽

Gas Sensing ◽

Mesoporous Titania ◽

Time Control

Download Full-text

Fabrication of n-ZnO/p-Si++ Hetero-junction Devices for Hydrogen Detection: Effect of Annealing Temperature

10.21203/rs.3.rs-891721/v1 ◽

2021 ◽

Author(s):

Vinod Kumar ◽

Ishpal Rawal ◽

Vipin Kumar

Keyword(s):

Grain Boundary ◽

Specific Surface ◽

Crystallite Size ◽

Surface Area ◽

Specific Surface Area ◽

Active Sites ◽

Annealing Temperature ◽

Gas Sensing ◽

Ambient Air ◽

Hydrogen Gas

Abstract In the present study, we reports the fabrication of n-ZnO/p-Si++ hetero-junction devices for the detection of hydrogen leakage in ambient air environment. For the fabrication of n-ZnO/p-Si++ hetero-junction devices, high quality ZnO thin films are grown by controlled thermal evaporation technique on the highly doped p-type silicon substrates at 400 oC. The two sets of films deposited at 400 o C are further annealed at 500 and 600 oC to examine the effect of annealing temperature on the structural, morphology, electrical and gas sensing properties of the deposited films. It is revealed from the x-ray diffraction studies that the crystallite size, and the density of the films increase from 22.55 to 24.95 nm, from 5.65 to 5.68 g/cm3, respectively, on increasing the fabrication temperature from 400 to 600 oC. In contrast to it, the grain boundary specific surface area decrease from 8.79 x107 to 7.88 x107 m-1 on changing the fabrication temperature from 400 to 600 oC. The hydrogen gas sensing response of the fabricated devices has also been recorded at different operating temperatures and different hydrogen concentrations (200 to 1000ppm) in air ambient. It is found that the gas sensing response of the fabricated devices increase with increase in operating temperature (up to 100 oC) and decease beyond this temperature. The gas sensing responses of the devices fabricated at 400, 500 and 600 oC are found to be 97.22, 64.23 and 40.77 % at 1000 ppm of hydrogen. A decrease in gas sensing response with fabrication temperature is attributed to the increase in crystallite size (quantum size effect), density of films (i.e. lower penetration) and decrease in grain boundary specific surface area (i.e. active sites) with annealing temperature. The mechanism of the gas sensing in these devices has also been systematically analyzed under different models.

Download Full-text

C2H5OH and NO2 sensing properties of ZnO nanostructures: correlation between crystal size, defect level and sensing performance

RSC Advances ◽

10.1039/c7ra13702h ◽

2018 ◽

Vol 8 (10) ◽

pp. 5629-5639 ◽

Cited By ~ 27

Author(s):

Chu Thi Quy ◽

Nguyen Xuan Thai ◽

Nguyen Duc Hoa ◽

Dang Thi Thanh Le ◽

Chu Manh Hung ◽

...

Keyword(s):

Nitrogen Dioxide ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Crystal Size ◽

Gas Sensing ◽

Zno Nanostructures ◽

Defect Level ◽

Sensing Applications ◽

Sensing Performance

ZnO nanostructures were synthesized for ethanol and nitrogen dioxide gas-sensing applications. Results pointed out that the defect levels dominating the gas-sensing performance but not the morphology, specific surface area or crystal size.

Download Full-text

P–p heterojunction CuO/CuCo2O4 nanotubes synthesized via electrospinning technology for detecting n-propanol gas at room temperature

Inorganic Chemistry Frontiers ◽

10.1039/c7qi00192d ◽

2017 ◽

Vol 4 (7) ◽

pp. 1219-1230 ◽

Cited By ~ 27

Author(s):

Khaled Tawfik Alali ◽

Zetong Lu ◽

Hongsen Zhang ◽

Jingyuan Liu ◽

Qi Liu ◽

...

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Room Temperature ◽

Gas Sensing ◽

Tubular Structure ◽

Large Specific Surface Area ◽

Sensing Performance

Composite CuO/CuCo2O4 nanotubes were synthesized by electrospinning technology. The large specific surface area, complex tubular structure, and p–p heterojunction are the potential reasons for the excellent room temperature gas sensing performance toward n-propanol vapor.

Download Full-text

Nanoflake assembled hierarchical porous flower-like α-Fe2O3 with large specific surface area for enhanced acetone sensing

Functional Materials Letters ◽

10.1142/s1793604720510388 ◽

2020 ◽

Vol 13 (06) ◽

pp. 2051038

Author(s):

Jianxia Zhang ◽

Li Liu ◽

Xiaonian Tang ◽

Dan Sun ◽

Chunxia Tian ◽

...

Keyword(s):

Specific Surface ◽

Surface Area ◽

Calcination Temperature ◽

Specific Surface Area ◽

Gas Sensing ◽

High Porosity ◽

Large Specific Surface Area ◽

Minimum Concentration ◽

Maximum Value ◽

Hierarchical Porous

High porosity [Formula: see text]-Fe2O3 has attracted a lot of attention due to its exceptional structure. In this paper, nanoflake assembled hierarchical porous flower-like [Formula: see text]-Fe2O3 was prepared by hydrothermal and calcination methods without any additional templates. Scanning electron microscopy (SEM) morphological characterization results show that with the increase of calcination temperature (400∘C, 450∘C, 500∘C, 550∘C, 600∘C), pores appeared. However, the results of nitrogen adsorption show that the specific surface area of the [Formula: see text]-Fe2O3 reaches the maximum value (52.19[Formula: see text]m2/g) when the calcination temperature is 500∘C. The gas sensing performance of flower-like [Formula: see text]-Fe2O3 with different calcination temperature is compared, interestingly, with the increase of calcination temperature, the response of the samples increased first and then decreased, and reached the maximum value (44.2–100 parts per million (ppm) acetone) when the calcination temperature was 500∘C. The minimum concentration for acetone was 200 ppb (response value is 2.0). Moreover, calcined at 500∘C, hierarchical porous [Formula: see text]-Fe2O3 has a fast response recovery (4/25 s) and low working temperature (210∘C). These excellent gas sensing properties are mainly due to porous structure, large specific surface area, and oxygen vacancies on the surface, which make it a promising material for acetone sensors.

Download Full-text