Fabrication of Nanosized Island-Like CdO Crystallites-Decorated TiO2 Rod Nanocomposites via a Combinational Methodology and Their Low-Concentration NO2 Gas-Sensing Behavior

Abstract

TiO2–CdO composite rods were synthesized through a hydrothermal method and sputtering thin-film deposition. The hydrothermally derived TiO2 rods exhibited a rectangular cross-sectional crystal feature with a smooth surface, and the as-synthesized CdO thin film exhibited a rounded granular surface feature. Structural analyses revealed that the CdO thin film sputtered onto the surfaces of the TiO2 rods formed a discontinuous shell layer comprising many island-like CdO crystallites. The TiO2–CdO composite rods were highly crystalline, and their surfaces were rugged. A comparison of the NO2 gas-sensing properties of the CdO thin film, TiO2 rods, and TiO2–CdO composite rods revealed that the composite rods exhibited superior gas-sensing responses to NO2 gas than did the CdO thin film and TiO2 rods, which can be attributed to the microstructural differences and the formation of heterojunctions between the TiO2 core and CdO crystallites.

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

“…No metallic W component was detected from the sample. The asymmetric O 1s spectrum of ZnO–WO 3 composite nanorods was displayed in Figure 5c and that spectrum was deconvoluted into three subpeaks at approximately 530.1 eV, 530.9 eV, and 531.9 eV, matching the oxygen coordination in lattice oxygen, vacancy oxygen, and surface chemisorbed oxygen, respectively [18,19]. By contrast, in Figure 5d, the Zn 2p spectrum of the ZnO–WO 3 composite nanorods with a thermal annealing at 400 °C exhibited a similar spectrum feature as exhibited in Figure 5a, revealing the divalent state of the zinc in the nanorods.…”

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

“…A larger potential barrier variation was expected in the NST than in the NPT during the gas-sensing tests. This explains the higher gas-sensing response of the NST in this study [2,36]. Moreover, the selectivity of the NST was shown in Figure 7f.…”

“…TiO 2 has been widely studied for applications in photodegradation organic dyes and gas-sensing materials because of its low toxicity, high chemical stability, and environmental friendliness [1][2][3][4][5][6]. However, TiO 2 still has some drawbacks that might limit its efficiency in photocatalyst and gas-sensing materials.…”

“…According to research fabricating TiO 2 -based heterostructures in applications such as gas-sensing materials, ZnS-sphere-decorated TiO 2 flower-like composites exhibit a superior gas-sensing response to pristine TiO 2 flowers [3]. Moreover, decorating the surface of TiO 2 nanorods with island-like CdO crystallites markedly improves the gas-sensing response of the nanorods to low-concentration NO 2 [2]. Increased potential barriers in the heterostructure systems could constitute an essential factor in enhancing the gas-sensing performance of TiO 2 on exposure to reducing and oxidizing gases.…”

Synthesis and Fabrication of In2O3: CdO Nanoparticles for NO2 Gas Sensor

“…Indium oxide is a wide band gap n-type semiconductor with direct band gaps of 3.75 eV, with a cubic bixbyite structure. It is a best material used as in transparent conducting oxide (18). Operating temperature is an essential parameter for gas sensitivity.…”