Hierarchical Dense Array of ZnO Nanowires Spatially Grown on ZnO/TiO₂ Nanofibers and Their Ultraviolet Activated Gas Sensing Properties

Abstract

A three-dimensional heterostructure using selective growth of ZnO nanowires on TiO 2 /ZnO nanocomposite nanofiber by a novel combination of a postseeding method in an electrospinning process and a hydrothermal technique is presented in this work. A hierarchical dense array of ZnO nanowires with a diameter of 70−120 nm and an aspect ratio of about 10 on TiO 2 /ZnO composite nanofibers (ZnO@TiO 2 /ZnO) was fabricated. XRD, UV−vis, FESEM, HRTEM, TEM, EDX, and XPS analyses were used for characterization of nanofibers. The results demonstrate about 4 times enhancement in UV spectrum absorption in the range of 240−300 nm compared to the nonhierarchical structures. It was found that the optimized operating temperatures for TiO 2 /ZnO nanofibers were 260 and 240 °C in the dark and under UV illumination. Results showed that ZnO@TiO 2 /ZnO exhibit about 3 times improvement in gas sensitivity with UV irradiation for 10−200 ppm of ethanol gas with reduced response and recovery times. UV-illuminated ZnO@TiO 2 /ZnO had about 3.81 and 4.30 times selectivity on ethanol with respect to acetone and toluene.

Environmentally Benign Organic Dye Conversion under UV Light through TiO2-ZnO Nanocomposite

“…It should be noted that the TU and ZU photocatalysts exhibit lower photocatalytic efficiency due to the higher recombination rate of the photogenerated electron-hole pair. Moreover, the photodegradation performance increased with the increasing content of ZnO, due to the formation of the effective heterojunction and the inhibition of electron-hole pair recombination [31]. However, when the ZnO content was exceeded in TZU70, there was a saturation value and the overall heterostructure was unstable, leading to a decrease in the effective charge transfer process in the heterostructure and a decrease in photocatalytic efficiency [29].…”

Nanosized ZnO/SiO2-Based Amphiphobic Coatings for Stone Heritage Protection

“…With the addition of ZnO, the absorption rate improved significantly, especially when m­(ZnO):m­(SiO 2 ) = 3:2, the absorption rate was close to 100%. This is attributed to the porous and uniformly rough structure constructed by the two nanoparticles, which allows light to be “trapped” within the structure for multiple refractions and provides a larger specific surface area and active sites, causing more photoelectric effects and thus increasing UV light absorption. , At this point, the absorptivity of the coating decreases when the ZnO content continues to increase, which might be due to the self-agglomeration of ZnO, resulting in uneven dispersion or shedding of particles. As a result, the UV absorption efficiency of the coating is reduced.…”

Optically Activated 3D Thin‐Shell TiO2 for Super‐Sensitive Chemoresistive Responses: Toward Visible Light Activation

“…The previous studies on light‐activated gas sensors have repeatedly reported relatively improved gas responses and faster recovery characteristics under light illumination. [ 7,8 ] Considering the high‐performance requirements for gas sensors in IoE applications, further modifications of the sensory materials, other than just relying on their bulk properties, should precede the full utilization of the given light energy. In response, there have been numerous efforts reported to date with various strategies for light‐activated gas sensors including i) heterojunction engineering, [ 9 ] ii) noble metal decoration, [ 10 ] iii) utilization of nonoxide materials (2D, inorganic perovskites), [ 11,12 ] iv) incorporation of plasmonic nanoparticles, [ 13 ] and v) development of effective nanostructures.…”