scholarly journals High performances room temperature NO2 gas sensor based on ZnO nanoparticles with oxygen vacancies prepared by auto combustion method

2021 ◽  
Author(s):  
Majdi Benamara ◽  
Hassen Dahman ◽  
Jalel Massoudi ◽  
Essebti Dhahri ◽  
Lassaad El Mir ◽  
...  
Keyword(s):  
Room Temperature ◽  
Oxygen Vacancies ◽  
Optical Measurement ◽  
Vacancy Concentration ◽  
Combustion Method ◽  
Visible Range ◽  
Light Illumination ◽  
Oxygen Vacancy Concentration ◽  
Pure Zinc ◽  
Auto Combustion

Abstract Pure zinc oxide was prepared by an auto-combustion method and oxygen vacancies were created by means of a thermally activated process as it is based on a vacuum treatment. XRD, XPS and SEM characterizations were used to determine the structure and morphology of pure and treated ZnO1 − X with x equal to 0, 0.05 and 0.10. Optical measurement was investigated in the UV-Visible range and indicated that oxygen vacancies enhance absorption in the visible range. Gas sensors were prepared by spraying the solution of ZnO1 − X nanoparticles on alumina substrates with pre-deposited gold interdigitated electrodes. The fabricated sensors exhibited exceptional sensing responses to 0.5 ppm of NO2 at room temperature and under white light illumination. The sensing tests outline an enhancement in sensors performances due to the presence of oxygen vacancies. The best response was 76, with 1.5 min and 2.7 min as response and recovery times respectively, obtained with sensor based on ZnO0.90 nanoparticles having the higher oxygen vacancy concentration, confirmed by XPS measurements and the lowest grain size and higher absorption in the visible range.

MECHANISM STUDY ON OXYGEN VACANCY INDUCED RESISTANCE SWITCHING IN Au/LaMnO3/SrNb0.01Ti0.99O3

2013 ◽  
Vol 27 (11) ◽  
pp. 1350074 ◽  
Author(s):  
YU-LING JIN ◽  
ZHONG-TANG XU ◽  
KUI-JUAN JIN ◽  
CHEN GE ◽  
HUI-BIN LU ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Oxygen Vacancies ◽  
Vacancy Concentration ◽  
Resistance Switching ◽  
Switching Behavior ◽  
Oxygen Vacancy Concentration ◽  
Mechanism Study ◽  
Switching Performance ◽  
Switching Characteristics

Mechanism of resistance switching in heterostructure Au / LaMnO 3/ SrNb 0.01 Ti 0.99 O 3 was investigated. In Au / LaMnO 3/ SrNb 0.01 Ti 0.99 O 3 devices the LaMnO 3 films were fabricated under various oxygen pressures. The content of the oxygen vacancies has a significant impact on the resistance switching performance. We propose that the resistance switching characteristics of Au / LaMnO 3/ SrNb 0.01 Ti 0.99 O 3 arise from the modulation of the Au / LaMnO 3 Schottky barrier due to the change of the oxygen vacancy concentration at Au / LaMnO 3 interface under the external electric field. The effect of the oxygen vacancy concentration on the resistance switching is explained based on the self-consistent calculation. Both the experimental and numerical results confirm the important role of the oxygen vacancies in the resistance switching behavior.

scholarly journals Evoked Methane Photocatalytic Conversion to C2 Oxygenates over Ceria with Oxygen Vacancy

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 196 ◽  
Author(s):  
Jin Du ◽  
Wei Chen ◽  
Gangfeng Wu ◽  
Yanfang Song ◽  
Xiao Dong ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Photocatalytic Oxidation ◽  
Oxygen Vacancies ◽  
Vacancy Concentration ◽  
Direct Conversion ◽  
Oxygen Vacancy Concentration ◽  
Ambient Conditions ◽  
Ethanol Production Rate ◽  
Viable Approach ◽  
Oxidation By Water

Direct conversion of methane to its oxygenate derivatives remains highly attractive while challenging owing to the intrinsic chemical inertness of CH4. Photocatalysis arises as a promising green strategy which could stimulate water splitting to produce oxidative radicals for methane C–H activation and subsequent C–C coupling. However, synthesis of a photocatalyst with an appropriate capability of methane oxidation by water remains a challenge using an effective and viable approach. Herein, ceria nanoparticles with abundant oxygen vacancies prepared by calcinating commercial CeO2 powder at high temperatures in argon are reported to capably produce ethanol and aldehyde from CH4 photocatalytic oxidation under ambient conditions. Although high-temperature calcinations lead to lower light adsorptions and increased band gaps to some extent, deficient CeO2 nanoparticles with oxygen vacancies and surface CeIII species are formed, which are crucial for methane photocatalytic conversion. The ceria catalyst as-calcinated at 1100 °C had the highest oxygen vacancy concentration and CeIII content, achieving an ethanol production rate of 11.4 µmol·gcat−1·h−1 with a selectivity of 91.5%. Additional experimental results suggested that the product aldehyde was from the oxidation of ethanol during the photocatalytic conversion of CH4.

Room temperature ferromagnetism in Gd-doped In2O3 nanoparticles obtained by auto-combustion method

2020 ◽  
Vol 31 (10) ◽  
pp. 7871-7879 ◽  
Author(s):  
G. Hosamani ◽  
B. N. Jagadale ◽  
J. Manjanna ◽  
S. M. Shivaprasad ◽  
D. K. Shukla ◽  
...  
Keyword(s):  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Combustion Method ◽  
Auto Combustion ◽  
In2o3 Nanoparticles

Conversion of syngas into light olefins over bifunctional ZnCeZrO/SAPO-34 catalysts: regulation of the surface oxygen vacancy concentration and its relation to the catalytic performance

2021 ◽  
Author(s):  
Yaoya Luo ◽  
Sen Wang ◽  
Shujia Guo ◽  
Kai Yuan ◽  
Hao Wang ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Oxygen Vacancies ◽  
Vacancy Concentration ◽  
Catalytic Performance ◽  
Light Olefins ◽  
Oxygen Vacancy Concentration ◽  
Surface Oxygen ◽  
Surface Oxygen Vacancy

Surface oxygen vacancies can improve the formation of methanol intermediates and promote their evolution into olefin products for syngas-to-olefins over Zn0.5CeZrOx/SAPO-34.

Stabilization of the ferroelectric phase in Hf-based oxides by oxygen scavenging

2021 ◽  
Author(s):  
Mingji Su ◽  
Jirong Liu ◽  
Zeping Weng ◽  
Xiang Ding ◽  
Zhengyang Chen ◽  
...  
Keyword(s):  
Oxygen Vacancy ◽  
Oxygen Vacancies ◽  
Crystallization Process ◽  
Ferroelectric Phase ◽  
Vacancy Concentration ◽  
Ferroelectric Properties ◽  
Ferroelectric Materials ◽  
Oxygen Vacancy Concentration ◽  
Vital Importance ◽  
Oxygen Scavenging

Abstract We propose an oxygen scavenging technique based on thermodynamic considerations of metal and oxygen systems to stabilize the ferroelectric phase and enhance the ferroelectricity in Hf-based oxides. By using an oxygen scavenging metal to control the oxygen vacancy concentration in Hf-based oxides, the effect of this oxygen scavenging technique in ferroelectric Hf-based oxides was systematically investigated. It was revealed that controlling the oxygen vacancies during the crystallization process is of vital importance to stabilizing the ferroelectric properties. This oxygen scavenging technique is an effective method of improving the performance of Hf-based ferroelectric materials without employing any dopant in HfO2.

scholarly journals Thermoelectric Power, Electrical Resistivity and Magnetic Properties of Ni-Sm Nano-particles

2020 ◽  
Vol 11 (1) ◽  
pp. 7835-7846
Keyword(s):  
Thermoelectric Power ◽  
Room Temperature ◽  
Structural Characteristics ◽  
Structural Parameters ◽  
Combustion Method ◽  
Xrd Analysis ◽  
Lattice Parameter ◽  
Differential Method ◽  
Nano Particles ◽  
Auto Combustion

Nanocrystalline Samarium doped Nickel ferrites having compositional formula NiSmXFe2-XO4 (0.00≤X≥0.10) were prepared by the citrate-gel auto combustion method and sintered at 5000C. The structural characteristics such as XRD analysis were shown cubic spinel structure, and the structural parameters like lattice parameter, X-ray density, bulk density, and porosity variations with Sm doping were studied. The surface morphology of prepared samples was observed by Scanning Electron Microscopy (SEM). The magnetic parameters were studied at room temperature with VSM, and the observed results are discussed with composition. The DC electrical properties were studied using a two-probe method in the temperature range from room temperature to well beyond Curie temperature. Thermoelectric power studies were carried out from room temperature to well beyond transition temperature with a differential method. The Seebeck coefficient variation with temperature was studied, and it shows the prepared samples are classified as n-type semiconductors. The observed results can be explained on the basis of the conduction mechanism.

Enhanced room temperature ferromagnetism in Cr-doped ZnO nanoparticles prepared by auto-combustion method

2018 ◽  
Vol 39 (4) ◽  
pp. 043001 ◽  
Author(s):  
Khizar-ul Haq ◽  
M. Irfan ◽  
Muhammad Masood ◽  
Murtaza Saleem ◽  
Tahir Iqbal ◽  
...  
Keyword(s):  
Zno Nanoparticles ◽  
Room Temperature ◽  
Room Temperature Ferromagnetism ◽  
Combustion Method ◽  
Auto Combustion ◽  
Doped Zno

Characterization and Magnetic Properties of Nanocrystalline Nickel Ferrite Synthesized by Carbon-Adsorb Auto Combustion Method

2011 ◽  
Vol 239-242 ◽  
pp. 108-111
Author(s):  
Ying Shan Chen ◽  
Wang Jun Feng ◽  
Cui Huan Li ◽  
Rui Shan Li ◽  
Rui Fan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Nickel Ferrite ◽  
Room Temperature ◽  
Combustion Method ◽  
Ferromagnetic Behavior ◽  
Vibrating Sample Magnetometry ◽  
Nanocrystalline Nickel ◽  
Transmission Electron ◽  
Auto Combustion ◽  
Xrd Techniques

Nanocrystalline nickel ferrite has been successfully synthesized through carbon-adsorb auto combustion method from Ni and Fe nitrate salts. The powders were characterized by X-raydiffraction(XRD) techniques,scanning electron microscopy(SEM),transmission electron microscopy(TEM) and vibrating sample magnetometry(VSM). XRD indicated that the products were spinel NiFe2O4. SEM and TEM indicated that the particles were spherical with particle size in the range 10-80nm. VSM showed that the sample exhibited typical ferromagnetic behavior at room temperature,while the coercivity of the sample was 150.45Oe and the residual magnetization of the sample was 5.1emu/g.The saturation magnetization of the sample(25.3emu/g)was lower than that for the reported bulk particles(55emu/g), and it has the ultrafine nature.

scholarly journals Ni/NiO Nanocomposites with Rich Oxygen Vacancies as High-Performance Catalysts for Nitrophenol Hydrogenation

Catalysts ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 944 ◽  
Author(s):  
Jun Zhou ◽  
Yue Zhang ◽  
Song Li ◽  
Jing Chen
Keyword(s):  
Charge Transfer ◽  
High Performance ◽  
Oxygen Vacancies ◽  
Vacancy Concentration ◽  
Hydrothermal Process ◽  
Oxygen Vacancy Concentration ◽  
Hydrogenation Catalysts ◽  
Hydrogen Flow ◽  
Sacrificial Agent

Heterogeneous catalysis often involves charge transfer between adsorbed molecules and the surface of catalyst, and thus their activity depends on the surface charge density. The efficiency of charge transfer could be optimized by adjusting the concentration of oxygen vacancies (Ov). In this work, hexagonal Ni(OH)2 nanoparticles were initially synthesized by a hydrothermal process using aluminum powder as the sacrificial agent, and were then converted into 2D Ni/NiO nanocomposites through in situ reduction in hydrogen flow. The oxygen vacancy concentration in the NiO nanosheet could be well-controlled by adjusting the reduction temperature. This resulted in strikingly high activities for hydrogenation of nitrophenol. The Ni/NiO nanocomposite could easily be recovered by a magnetic field for reuse. The present finding is beneficial for producing better hydrogenation catalysts and paves the way for the design of highly efficient catalysts.

scholarly journals Temperature effect over structure and photochemical properties of nanostructured SnO2 powders

2014 ◽  
Vol 12 (9) ◽  
pp. 909-917 ◽  
Author(s):  
Ana-Maria Ungureanu ◽  
Ovidiu Oprea ◽  
Bogdan Vasile ◽  
Corina Andronescu ◽  
Georgeta Voicu ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Oxygen Vacancies ◽  
Single Phase ◽  
Tin Dioxide ◽  
Vacancy Concentration ◽  
Structural Characteristics ◽  
Oxygen Vacancy Concentration ◽  
High Concentration ◽  
Tem Analysis ◽  
X Ray

AbstractWe successfully synthesized tin dioxide nanoparticles with polyhedral morphology via an ethylene glycol assisted sol-gel approach. The structural characteristics of three tin dioxide samples were investigated after being thermally treated at 400°C, 600°C and 800°C. X-ray diffraction (XRD) patterns clearly show the formation of single phase tin dioxide nanoparticles, with crystallite size of 6–20 nm, in good correlation with Fourier transform infrared (FTIR) spectra. Transmission electron microscopy (TEM) analysis confirms the formation of 6nm polyhedral nanoparticles for the 400°C sample. Ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectra suggest a high concentration of oxygen vacancies. The oxygen vacancy concentration increases with temperature, due to the combined action of the formation of VO and the energetic O compensation. X-ray photoelectron spectroscopy (XPS) analysis also confirms the formation of single phase tin dioxide and the presence of oxygen vacancies in good agreement with UV-VIS and PL data.

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