“…The alternate current conductivity was determined by the expression (Fig. 11 a) 97 . Figure 11 Alternate conductivity ( a ) and energy activation ( b , c ).…”
This study centers on the environmentally benign synthesis of zinc oxide nanoparticles (ZnO NPs) derived from Zn (CH3COO)2·2H2O and Moringa seeds. The synthesized nanostructures underwent comprehensive characterization utilizing diverse analytical techniques, encompassing X-ray diffraction (XRD), UV–VIS spectroscopy, field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. XRD measurements coupled with W–H plot transformation unequivocally confirmed the formation of ZnO nanostructures, characterized by an average size of 24.9 nm. UV–VIS spectroscopy, complemented by Kubelka Munk curve analysis, elucidated the direct conduction and determined a bandgap of 3.265 eV. FESEM analysis revealed minimal particle aggregation, showcasing well-defined grain boundaries spanning sizes from 20.4 to 87.7 nm. XPS analysis substantiated the presence of Zn (2p), Zn (3p), Zn (3d), and O (1s). Raman spectroscopy identified E2H as the predominant mode, followed by E1(TO) and (E2H-E2L). ZnO thin films, fabricated via pulsed laser deposition (PLD) and deposited onto silicon (100) substrates, exhibited exemplary morphology and discernible topography, characterized by a normal grain size distribution. Zeta potential tests yielded a value of approximately ($$\mathcalligra{z}$$
z
~ − 43.8 mV), indicative of the commendable stability of the colloidal suspension, likely attributable to low particle aggregation. Dielectric measurements conducted on sintered pellets at 900 °C unveiled elevated capacitance and dielectric constant at low frequencies across the temperature range of 289.935–310 K. These findings affirm the potential utility of environmentally synthesized ZnO for a spectrum of applications, including energy devices and nanofluids.
“…The alternate current conductivity was determined by the expression (Fig. 11 a) 97 . Figure 11 Alternate conductivity ( a ) and energy activation ( b , c ).…”
This study centers on the environmentally benign synthesis of zinc oxide nanoparticles (ZnO NPs) derived from Zn (CH3COO)2·2H2O and Moringa seeds. The synthesized nanostructures underwent comprehensive characterization utilizing diverse analytical techniques, encompassing X-ray diffraction (XRD), UV–VIS spectroscopy, field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. XRD measurements coupled with W–H plot transformation unequivocally confirmed the formation of ZnO nanostructures, characterized by an average size of 24.9 nm. UV–VIS spectroscopy, complemented by Kubelka Munk curve analysis, elucidated the direct conduction and determined a bandgap of 3.265 eV. FESEM analysis revealed minimal particle aggregation, showcasing well-defined grain boundaries spanning sizes from 20.4 to 87.7 nm. XPS analysis substantiated the presence of Zn (2p), Zn (3p), Zn (3d), and O (1s). Raman spectroscopy identified E2H as the predominant mode, followed by E1(TO) and (E2H-E2L). ZnO thin films, fabricated via pulsed laser deposition (PLD) and deposited onto silicon (100) substrates, exhibited exemplary morphology and discernible topography, characterized by a normal grain size distribution. Zeta potential tests yielded a value of approximately ($$\mathcalligra{z}$$
z
~ − 43.8 mV), indicative of the commendable stability of the colloidal suspension, likely attributable to low particle aggregation. Dielectric measurements conducted on sintered pellets at 900 °C unveiled elevated capacitance and dielectric constant at low frequencies across the temperature range of 289.935–310 K. These findings affirm the potential utility of environmentally synthesized ZnO for a spectrum of applications, including energy devices and nanofluids.
Low-dimensional metal oxides have drawn significant attention across various scientific domains due to their multifaceted applications, particularly in the field of environment monitoring. Their popularity is attributed to a constellation of unique properties, including their high surface area, robust chemical stability, and remarkable electrical conductivity, among others, which allow them to be a good candidate for detecting CO, CO2, H2, NH3, NO2, CH4, H2S, and volatile organic compound gases. In recent years, the Sol-Gel method has emerged as a powerful and versatile technique for the controlled synthesis of low-dimensional metal oxide materials with diverse morphologies tailored for gas sensing applications. This review delves into the manifold facets of the Sol-Gel processing of metal oxides and reports their derived morphologies and remarkable gas-sensing properties. We comprehensively examine the synthesis conditions and critical parameters governing the formation of distinct morphologies, including nanoparticles, nanowires, nanorods, and hierarchical nanostructures. Furthermore, we provide insights into the fundamental principles underpinning the gas-sensing mechanisms of these materials. Notably, we assess the influence of morphology on gas-sensing performance, highlighting the pivotal role it plays in achieving exceptional sensitivity, selectivity, and response kinetics. Additionally, we highlight the impact of doping and composite formation on improving the sensitivity of pure metal oxides and reducing their operation temperature. A discussion of recent advances and emerging trends in the field is also presented, shedding light on the potential of Sol-Gel-derived nanostructures to revolutionize the landscape of gas sensing technologies.
Of numerous environmental problems, the air pollution caused by toxic nitrogen dioxide has become more and more serious. Its timing detection is of utmost importance but challenging. It is known that NO2 sensors fabricated by zinc oxide-derived materials suffer some issues. And thus synthetic strategies such as doping and combining have been developed to improve sensitive performance and modify operation condition. However, the relevant sensing reaction mechanism still remains unclear; moreover, the experimentally structural characterizations on sensitive materials (SMs) and reaction intermediates are rather difficult at the atomic level, which turn much worse for the doped and combined SMs. In the work, density functional theory calculations have been exploited to examine copper-doped zinc oxide (marked as ZOC) and its composites ZOC/CN and ZOC/Gr. CN and Gr are short for 2D materials, graphitic carbon nitride (g-C3N4) and graphene, respectively. The local structures have been accessible for these SMs and their intermediates along the reaction pathway. It is shown that ZOC bears the Cu-Zn heterobimetallic adsorption active sites, which hold NO2 via Cu/Zn-O dative bonds. The introduction of copper increases metal contribution to high-lying occupied molecular orbitals (MOs). Major NO2→ZOC donation and minor back-donation interactions have been recognized by charge decomposition analyses in terms of fragment MOs. Consequently, its adsorption free energy towards NO2 is strengthened by 0.27 eV relative to pristine ZnO. These well interpret the experimental findings that the copper-doped zinc oxide has much faster response time. Further combination with g-C3N4 enhances the NO2-sensing performance, which turns out to be the best SM candidate. Exemplarily, ZOC/CN shows the most negative NO2 adsorption energy (-0.31 eV), very small uphill energy for the rate-determining step (0.27 eV) and modest formation energy of nitrate (-1.06 eV). With these, the SM not only responses NO2 rapidly but also desorbs nitrate at mild
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