Growth Mechanisms of ZnO Micro-Nanomorphologies and Their Role in Enhancing Gas Sensing Properties

Abstract

Zinc oxide (ZnO) is one of the main functional materials used to realize chemiresistive gas sensors. In addition, ZnO can be grown through many different methods obtaining the widest family of unique morphologies. However, the relationship between the ZnO morphologies and their gas sensing properties needs more detailed investigations, also with the aim to improve the sensor performances. In this work, seven nanoforms (such as leaves, bisphenoids, flowers, needles, etc.) were prepared through simple wet chemical synthesis. Morphological and structural characterizations were performed to figure out their growth mechanisms. Then, the obtained powders were deposited through screen-printing technique to realize thick film gas sensors. The gas sensing behavior was tested toward some traditional target gases and some volatile organic compounds (acetone, acetaldehyde, etc.) and compared with ZnO morphologies. Results showed a direct correlation between the sensors responses and the powders features (morphology and size), which depend on the specific synthesis process. The sensors can be divided in two behavioral classes, following the two main morphology kinds: aggregates of nanocrystals (leaves and bisphenoids), exhibiting best performances versus all tested gases and monocrystal based (stars, needle, long needles, flowers, and prisms).

Metal–Organic Framework-Derived Porous Hollow Co3O4/ZnO Nanofibers for H2S Sensing

“…Moreover, the formation of heterojunctions leads to more defects and target adsorption sites, along with an increase in oxygen vacancies. This improves the gas-sensitive response and response recovery rate of the material. , When exposed to H 2 S, the sensor releases the trapped electrons from the adsorbed oxygen back to the conduction band of the composite, and electrons flow from ZnO to Co 3 O 4 . This indicates that the depletion layer thickness of the heterogeneous interfaces of the Co 3 O 4 /ZnO composite nanofibers becomes thin compared to that in air, leading to a significant reduction in the sensor resistance.…”

Effect of variable thickness on liquefied petroleum gas sensing response of ZnO thin films

“…The large surface area of the ZnO thin films leads in a large number of surface atoms, which might cause a lack in surface atomic correlation and excessive surface energy [40]. Ambra et al and Fengjun et al also reported the effect of specific surface area on gas sensing properties of ZnO thin films [41,42]. Surface morphology influenced the distribution and accessibility of reaction sites on the film's surface.…”

The Effect of Couple Doping Gd and Co on The Physical Characteristics of LaFeO3 Thick Film for Acetone Gas Sensor Application

“…XRD was carried out to see the crystal structure of thick film ceramics, and the results were analyzed using Match!3, so the crystal phase, crystal plane orientation (miller index, hkl), lattice parameters (a, b, and c) and crystallite size (D) were obtained. The crystallite size was obtained from the Debye-Scherrer Equation [23], which is shown in Equation ( 1), namely…”