Graphene-wrapped ZnO nanocomposites were fabricated by a simple solvothermal technology with a one-pot route. The structure and morphology of these as-fabricated samples were systematically ...characterized. The adding of graphene enhanced the content of the oxygen vacancy defect of the sample. All gas-sensing performances of sensors based on as-prepared samples were thoroughly studied. Sensors displayed an ultrahigh response and exceptional selectivity at room temperature under blue light irradiation. This excellent and enhanced toluene gas-sensing property was principally attributed to the synergistic impacts of the oxygen vacancy defect and the wrapped graphene in the composite sensor. The photo-activated graphene-wrapped ZnO sensor illustrated potential application in the practical detection of low concentrations of toluene under explosive environments.
Zn-doped SnO2 nanorods clusters with controllable size (the length and the diameter of nanorods) are prepared by adjusting the Zn2+ concentration in the precursor solution using a facile hydrothermal ...process. The as-synthesized samples are characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and energy-dispersive X-ray spectroscopy (EDS). With an increase of the molar ratio of Zn2+/Sn4+ in the solution, the length of the Zn-doped SnO2 nanorods gradually increases, and the average length of the nanorods reaches the maximum of 239nm at 0.133. However, when the molar ratio of Zn2+/Sn4+ is increased to 0.2, the length of the nanorods decreases accompanied with the generation of Zn2SnO4 phase. The Zn-doped SnO2 nanorods grow along the 112 direction and the possible growth mechanism is proposed. The gas-sensing properties of the obtained Zn-doped SnO2 samples are tested towards methanol gas. And, it is found the composition-morphology-performance relationship that the more the doping content of Zn, the longer the length of nanorods and the higher the response to methanol, which is significant for the preparation and the design of gas-sensing materials with the high performance.
In this work, we report on the gas-sensing behavior of Al-doped SnO2 nanotubes (NTs) in order to evaluate the effect of Al on improved sensing performance and propose an oxygen-vacancy-dominating ...sensing mechanism of SnO2. The hierarchical mesoporous Al-doped SnO2 NTs are fabricated by simple electrospinning method and annealing treatment. Al-doping shows profound influence on the oxygen vacancy of SnO2 which changes as a function of Al/(Al+Sn) ratio and the oxygen vacancy exhibits a maximum value when the ratio is 8%. As a result, the gas-sensing response to formaldehyde varies following the oxygen vacancies. Oxygen vacancies at the surface of SnO2 facilitate oxygen adsorption and the formation of surface catalytic active O−O−, thus the gas response is remarkably enhanced. Furthermore, a new fundamental understanding toward the gas-sensing performance of oxygen-vacancy-dominating SnO2 is proposed.
Here, by means of opening the interlayer spacing (5.8 Å to 10 Å), enhanced gas response (∼2 to 50 ppm NO2) and fast response/recovery speed (∼15 s) can be simultaneously achieved in the novel VS2-E ...based gas sensor, because of the enlarged distance allows more NO2 to enter the interlayer, and the weaker binding energy (−0.22 eV) of NO2 in the expanded VS2-E layers accelerates its adsorption and desorption.
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•A novel NO2 sensor based on expanded 2D VS2 is reported for its fast response/recovery (15 s).•Revealing the p-type semiconducting features of the expanded VS2 with coexistence of T and H phases.•Confirming that enlarging the interlayer spacing can improve the gas-sensing properties of 2D TMDs innovatively.•In-depth explanations are supported by the DFT calculations and the mechanism explanation.
Currently, most gas sensors of two-dimensional (2D) layered transition metal dichalcogenides (TMDs) are only focused on the surface adsorption while ignoring their large interlayer active regions. The recovery time of 2D TMDs gas sensors are relatively long due to the limited interlayer spacing. Herein, the interlayer-expanded VS2 (VS2-E, 10 Å) based NO2 gas sensor with rapid response/recovery (∼15 s) is reported innovatively. The response and recovery time is 1/23 and 1/41 of the normal interlayer spacing VS2 (VS2-N, 5.8 Å) counterparts, respectively. VS2-E with coexistence of T and H phases shows the p-type semiconductor features. In addition, the response value of VS2-E sensor is ∼2 to 50 ppm NO2 at 120 °C, approximately twice that of VS2-N. The enlarged interlayer spacing of VS2-E promotes the adsorption/desorption of more NO2 molecules between the interlayers, leading to a larger response and quicker response/recovery for VS2-E compared with VS2-N. This is also confirmed by a weaker binding energy (−0.17 eV) of NO2 in VS2-E layers than that of VS2-N (−0.62 eV) calculated by theoretical calculation. This work enriches the interlayer sensing mechanism and provides a significant guidance for the applications of interlayer regulation engineering in other 2D layered gas-sensing materials.
Defect graphene was reported by adding sugar through solvothermal method. The characterization results of XRD, IR, Raman, and XPS showed that the samples have tunable mount of oxygenated group, which ...plays a role as adsorption site to detecting humidity gas molecule. The sample from sucrose has the highest mount of functional oxygenated groups and shows the best humidity property.
► Graphene with tunable defect was reported through solvothermal method. ► The defect was considered as oxygenated groups based on characterization results. ► The sample from sucrose has the most mount of functional oxygenated groups. ► The defect plays a role as adsorption site to detecting humidity gas molecule. ► The sample from sucrose shows the best humidity property.
Porous TiO2 and ZnO films, fabricated by screen printing, were assessed as UV light activated gas sensors at room temperature. To facilitate the simultaneous measurements of the current transients of ...the two materials, they were printed onto the same alumina substrate. Compared with ZnO, TiO2 exhibited a superior performance to ethanol and formaldehyde gases. The response of TiO2 increased with the concentration of the test gas and amounted to 224 and 1700 to 100 ppm ethanol and formaldehyde gases, respectively, while the responses of ZnO to 100 ppm ethanol and formaldehyde gases were 0.14 and 1.5, respectively. The difference between TiO2 and ZnO is discussed. Furthermore, it is suggested that a metal oxide semiconductor with lower photo-to-dark current ratio can achieve higher photoactivated gas sensitivity.
The shell–core nanocomposites of MOX/AP were prepared by a facile liquid deposition method at room temperature and exhibited significant self-catalytic effects for the thermal decomposition of AP in ...lowering the decomposition temperature and increasing the heat release.
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► MOX/AP shell–core nanocomposites were synthesized by a facile liquid deposition method. ► MOX nanoparticles were homogeneously coated on the surface of AP. ► The nanocomposites have excellent self-catalytic performances for AP decomposition. ► ZnO/AP nanocomposites (mass ratio
=
4:100) exhibit the best self-catalytic performance.
To overcome the agglomeration of metal oxide (MOX) nanocatalysts mechanically mixed with ammonium perchlorate (AP) and other additives of rocket propellant, the shell–core nanocomposites of MOX/AP have been synthesized successfully by a facile liquid deposition method at room temperature. SEM analysis revealed that MOX (M
=
Zn, Co, Fe) nanoparticles were deposited on the surface of AP particles as either a continuous thin layer or small clusters. Owing to the existence of the shell of MOX nanocatalysts, ZnO/AP, Co
3O
4/AP and Fe
2O
3/AP nanocomposites showed excellent self-catalytic performances for AP thermal decomposition: lowering the decomposition temperature from 398
°C to 272
°C, 285
°C, 337
°C, and increasing the heat release from 584
J
g
−1 to 1137
J
g
−1, 1237
J
g
−1, 1010
J
g
−1, respectively. Moreover, their self-catalytic performances mainly relied on the content of MOX nanocatalysts, which was controlled by the concentration of metal salts in the precursor solution. In particular, ZnO/AP nanocomposites with the mass ratio of ZnO:AP
=
4:100 exhibited the best self-catalytic performance in decreasing the activation energy from 154.0
kJ/mol to 96.5
kJ/mol. The MOX/AP (M
=
Zn, Co, Fe) shell–core nanocomposites could have a promising application in the rocket propellant for improving the thermal-catalytic decomposition performance of AP.
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•Charge separation in homojunction based on the broadened band gap by quantum effect.•Absolute charge separation by the passivation effect of TiO2 nanorod.•Long-distance electron ...transfer behavior in photocatalysis.•Roughed surface for enhanced light harvesting by light trapping effect.
As known, the electron transfer behavior in photocatalysis is short-distance transportation, which leads the photo-induced electrons and holes to be localized. The temporarily separated electrons and holes will recombine with each other in the localized region. In this paper, we successfully achieved electron transfer in a homojunction of branched rutile TiO2 nanorod @nanoparticle core-shell architecture by quantum confinement effect aroused by the nanoparticle, which is proved by the blue-shifting in UV–vis absorption spectrum of the homojunction. Meanwhile, an absolute charge separation is also achieved by the long-distance electron transfer along the single-crystalline rutile TiO2 nanorod as uninterrupted high-speed electron transfer channel to FTO substrates. Based on the effective charge separation, the photocatalytic decomposition of gaseous benzene by the homojunction is significantly enhanced, yielding 10 times CO2 than that of the nanorod array. This homojunction interfacial charge separation, aroused by quantum effect, through long-distance transfer along the single-crystalline nanorod gives us inspiration to achieve efficient charge separation with defect-less interfaces, which might can be utilized for real-time environmental abatement and energy generation simultaneously.
VO2-based film, as a very promising thermochromic material for smart windows, has attracted extensive attention but has not been widely applied because it is difficult to simultaneously improve in ...terms of both solar-modulation efficiency (ΔTsol) and visible transmittance (Tlum) when made using the magnetron-sputtering method, and it has poor durability when made using the wet chemical method. Herein, island-like ZrO2-VO2 composite films with improved thermochromic performance (ΔTsol: 12.6%, Tlum: 45.0%) were created using a simple approach combining a dual magnetron-sputtering and acid-solution procedure. The film’s ΔTsol and Tlum values were increased initially and subsequently declined as the sputtering power of the ZrO2 target was raised from 30 W to 120 W. ΔTsol achieved its maximum of 12.6% at 60 W, and Tlum reached its maximum of 51.1% at 90 W. This is likely the result of the interaction of two opposing effects: Some VO2 nanocrystals in the composite film were isolated by a few ZrO2 grains, and some pores could utilize their surface-plasmon-resonance effect at high temperature to absorb some near-infrared light for an enhanced ΔTsol and Tlum. More ZrO2 grains means fewer VO2 grains in the composite film and increased film thickness, which also results in a decrease in ΔTsol and Tlum. As a result, this work may offer a facile strategy to prepare VO2-based films with high thermochromic performance and promote their application in smart windows.
QDS modified Bi(2)WO(6) (BWO) nanostructures were processed by calcination at different temperatures. A strong correlation was found among the processing, structure and properties of the samples. ...With increasing calcination temperature from 200°C to 500°C, the crystallinity increased and the BWO QDS gradually disappeared from the nanostructures. Both surface area and band gap of the samples decreased. The light absorption of the samples became lower for the long-wavelength range, accompanied by a red shift of the absorption edge. The photocatalytic activity of the samples decreased after calcination at higher temperature. The competitive relations between crystallinity and surface area in affecting photocatalytic activity were discussed. The role of BWO QDS that played in enhancement of photocatalytic activity was also revealed by studying structure and property evolution of the calcined samples.
