Hierarchical core/shell ZnO/NiO nanoheterojunctions synthesized by ultrasonic spray pyrolysis and their gas-sensing performance

Abstract

ZnO nanorod arrays decorated with NiO nanosheets on FTO substrates were prepared via a simple ultrasonic spray pyrolysis process combined with chemical bath method. The synthesized samples were characterized and analyzed by scanning electron microscopy and X-ray diffraction. The hierarchical and porous morphologies of ZnO/NiO core-shell nanoheterojunctions could be controlled by changing the growth time of NiO sheets. The "oriented attachment" and "self-assembly" crystal growth mechanisms were proposed to explain the formation of the ZnO/NiO nanostructures. Sensors based on the ZnO/NiO heterojunction nanostructure were fabricated and investigated for their ethanol-sensing properties. The result indicated that response was about 180% toward 100 ppm ethanol at an operating temperature of 200 °C.The growth approach in this work offers a new technique for the design and synthesis of transition metal oxide hierarchical nanoarrays which are promising for gas sensing applications.

Surface Morphology-Dependent Functionality of Titanium Dioxide–Nickel Oxide Nanocomposite Semiconductors

“…(Figure 4a,b), which were in agreement with those reported in the literature for the NiO phase [18,19]. Figure 4c,d show the O1s spectra of the TiO2-NiO composites formed at 350 °C and eV and were attributed to the lattice oxygen of the NiO phase [20]; additionally, broadened subpeaks were observed at 530.7 eV and were attributed to the formation of surface-oxygen-deficient sites and surface chemisorbed oxygen species on the NiO shell layer [21]. Notably, the relative intensity of the higher binding energy component in the O1s spectra of the TiO2-NiO composites decreased when the composites were thermally treated from 350 °C to 500 °C.…”

“…Figure 4c,d show the O1s spectra of the TiO 2 -NiO composites formed at 350 • C and 500 • C, respectively. Sharp fitted subpeaks were observed at a binding energy of approximately 528.8 eV and were attributed to the lattice oxygen of the NiO phase [20]; additionally, broadened subpeaks were observed at 530.7 eV and were attributed to the formation of surface-oxygen-deficient sites and surface chemisorbed oxygen species on the NiO shell layer [21]. Notably, the relative intensity of the higher binding energy component in the O1s spectra of the TiO 2 -NiO composites decreased when the composites were thermally treated from 350 • C to 500 • C. This finding reveals that surface crystalline imperfections of a larger size were formed in the NiO nanosheets.…”

Self-Aligned Hierarchical ZnO Nanorod/NiO Nanosheet Arrays for High Photon Extraction Efficiency of GaN-Based Photonic Emitter

“…Since the system tends to minimize the overall surface energy, the ZNRs grew preferentially along the [0001] direction [28,29]. Then, Ni-based nanoparticles (NPs) nucleated on the surface of the ZNRs to form active sites, which minimized the interfacial energy barrier to promote the subsequent growth of Ni-based NPs.…”

Controlled Carbon Doping in Anatase TiO2 (101) Facets: Superior Trace‐Level Ethanol Gas Sensor Performance and Adsorption Kinetics

“…[1][2][3][4][5][6] The trace level detection of ethanol is possible with metal oxides due to the presence of highly active surface adsorbed superaxo and peraxo oxygen species. [1][2][3][4][5][6] The trace level detection of ethanol is possible with metal oxides due to the presence of highly active surface adsorbed superaxo and peraxo oxygen species.…”

“…To the best of our knowledge, the clear gas sensing mechanism of carbon-doped TiO 2 has not yet been reported so far. To the best of our knowledge, so far carbon-doped TiO 2 has not been exploited for detection of trace-level volatile organic compound sensors.…”