Improvement of Ethanol Gas-Sensing Responses of ZnO–WO3 Composite Nanorods through Annealing Induced Local Phase Transformation

Liang, Yuan‐Chang; Chang, Chi Wei

doi:10.3390/nano9050669

Cited by 28 publications

(20 citation statements)

References 30 publications

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“…The XPS survey scan spectrum ( Figure S1) of as-synthesized ZnO sheets also demonstrated no nitrogen existed in the sample, revealing the well phase transformation of Zn4CO3(OH)6•H2O to ZnO after the postannealing procedure. [22][23][24]. Figure 5d-f show the O1s XPS spectra of various ZnO sheets.…”

Section: Methodsmentioning

confidence: 99%

Thermal Annealing Induced Controllable Porosity and Photoactive Performance of 2D ZnO Sheets

2020

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Porous ZnO sheets containing various degrees of a nanoscaled pore were successfully synthesized using a simple hydrothermal method and various postannealing procedures. The porosity features of the ZnO sheets can be easily tuned by changing both the annealing temperature and annealing atmosphere. The dense porous nature of ZnO sheets is beneficial to enhance light absorption. Moreover, the substantially increased oxygen vacancies in the ZnO sheets were observed especially after the hydrogen treatment as revealed in the X-ray photoelectron spectroscope and photoluminescence analyses. The high density of surface crystal defect enhanced the photoinduced electron-hole separation rate of the ZnO sheets, which is crucial for an improved photoactivity. The porous ZnO sheets formed at a hydrogen atmosphere exhibited superior photoactive performance than the porous ZnO sheets formed at the high-temperature ambient air annealing. The dense pores and massive crystal defects formed by a hydrogen atmosphere annealing in the ZnO crystals might account for the observed photoactive behaviors in this study.

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Section: Methodsmentioning

confidence: 99%

Thermal Annealing Induced Controllable Porosity and Photoactive Performance of 2D ZnO Sheets

2020

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“…The Zn 2p spectra showed two symmetric binding features, the peak centered at 1021.8 eV corresponds to the Zn 2p 3/2 and the other one centered at 1044.8 eV is assigned to Zn 2p 1/2 . The spin-orbit splitting between Zn 2p 3/2 and Zn 2p 1/2 of various porous composite nanosheets is approximately 23 eV, indicating that zinc is in the Zn 2+ binding state in the ZnO nanosheet templates [ 21 , 22 ]. Comparatively, the relative intensity of the Zn 2p spectrum in Figure 4 d is weaker than that in Figure 4 c; this is in agreement with the Ni 2p spectrum intensity variation for various ZnO-NiO porous composite nanosheets as exhibited in Figure 4 a,b.…”

Section: Resultsmentioning

confidence: 99%

Design and Synthesis of Novel 2D Porous Zinc Oxide-Nickel Oxide Composite Nanosheets for Detecting Ethanol Vapor

2020

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The porous zinc oxide-nickel oxide (ZnO-NiO) composite nanosheets were synthesized via sputtering deposition of NiO thin film on the porous ZnO nanosheet templates. Various NiO film coverage sizes on porous ZnO nanosheet templates were achieved by changing NiO sputtering duration in this study. The microstructures of the porous ZnO-NiO composite nanosheets were investigated herein. The rugged surface feature of the porous ZnO-NiO composite nanosheets were formed and thicker NiO coverage layer narrowed the pore size on the ZnO nanosheet template. The gas sensors based on the porous ZnO-NiO composite nanosheets displayed higher sensing responses to ethanol vapor in comparison with the pristine ZnO template at the given target gas concentrations. Furthermore, the porous ZnO-NiO composite nanosheets with the suitable NiO coverage content demonstrated superior gas-sensing performance towards 50–750 ppm ethanol vapor. The observed ethanol vapor-sensing performance might be attributed to suitable ZnO/NiO heterojunction numbers and unique porous nanosheet structure with a high specific surface area, providing abundant active sites on the surface and numerous gas diffusion channels for the ethanol vapor molecules. This study demonstrated that coating of NiO on the porous ZnO nanosheet template with a suitable coverage size via sputtering deposition is a promising route to fabricate porous ZnO-NiO composite nanosheets with a high ethanol vapor sensing ability.

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“…Tungsten trioxide (WO 3 ), the most widely studied and used electrochromic material, has been studied for many years since having been found by Deb in the 1960s, thanks to its attractive characteristics of high coloring efficiency, good optical modulation ability and decent chemical stability in the field of electrochromism [3][4][5][6]. It is remarkable that WO 3 with various crystalline structures by different synthesis methods is extensively appropriate for diverse device applications [7][8][9], such as the electrochromic smart window [10,11], rear-view automatic-dimming rearview mirror [12], gas sensor device [13][14][15], and military camouflage [16], etc. A large variety of techniques can be used to prepare WO 3 thin films, such as chemical vapor deposition (CVD) [17], physical vapor deposition (PVD) [18] and wet chemical deposition methods base on solution [19][20][21].…”

Section: Introductionmentioning

confidence: 99%

Effect of the Ammonium Tungsten Precursor Solution with the Modification of Glycerol on Wide Band Gap WO3 Thin Film and Its Electrochromic Properties

et al. 2020

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Tungsten trioxide (WO3) is a wide band gap semiconductor material, which is commonly not only used, but also investigated as a significant electrochromic layer in electrochromic devices. WO3 films have been prepared by inorganic and sol-gel free ammonium tungstate ((NH4)2WO4), with the modification of glycerol using the spin coating technique. The surface tension, the contact angle and the dynamic viscosity of the precursor solutions demonstrated that the sample solution with a 25% volume fraction of glycerol was optimal, which was equipped to facilitate the growth of WO3 films. The thermal gravimetric and differential scanning calorimetry (TG-DSC) analysis represented that the optimal sample solution transformed into the WO3 range from 220 °C to 300 °C, and the transformation of the phase structure of WO3 was taken above 300 °C. Fourier transform infrared spectroscopy (FT-IR) spectra analysis indicated that the composition within the film was WO3 above the 300 °C annealing temperature, and the component content of WO3 was increased with the increase in the annealing temperature. The X-ray diffraction (XRD) pattern revealed that WO3 films were available for the formation of the cubic and monoclinic crystal structure at 400 °C, and were preferential for growing monoclinic WO3 when annealed at 500 °C. Atomic force microscope (AFM) images showed that WO3 films prepared using ammonium tungstate with modification of the glycerol possessed less rough surface roughness in comparison with the sol-gel-prepared films. An ultraviolet spectrophotometer (UV) demonstrated that the sample solution which had been annealed at 400 °C obtained a high electrochromic modulation ability roughly 40% at 700 nm wavelength, as well as the optical band gap (Eg) of the WO3 films ranged from 3.48 eV to 3.37 eV with the annealing temperature increasing.

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Improvement of Ethanol Gas-Sensing Responses of ZnO–WO3 Composite Nanorods through Annealing Induced Local Phase Transformation

Cited by 28 publications

References 30 publications

Thermal Annealing Induced Controllable Porosity and Photoactive Performance of 2D ZnO Sheets

Thermal Annealing Induced Controllable Porosity and Photoactive Performance of 2D ZnO Sheets

Design and Synthesis of Novel 2D Porous Zinc Oxide-Nickel Oxide Composite Nanosheets for Detecting Ethanol Vapor

Effect of the Ammonium Tungsten Precursor Solution with the Modification of Glycerol on Wide Band Gap WO3 Thin Film and Its Electrochromic Properties

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