ZnO Structures with Surface Nanoscale Interfaces Formed by Au, Fe2O3, or Cu2O Modifier Nanoparticles: Characterization and Gas Sensing Properties

Zinc oxide rod structures are synthetized and subsequently modified with Au, Fe2O3, or Cu2O to form nanoscale interfaces at the rod surface. X-ray photoelectron spectroscopy corroborates the presence of Fe in the form of oxide—Fe2O3; Cu in the form of two oxides—CuO and Cu2O, with the major presence of Cu2O; and Au in three oxidation states—Au3+, Au+, and Au0, with the content of metallic Au being the highest among the other states. These structures are tested towards nitrogen dioxide, ethanol, acetone, carbon monoxide, and toluene, finding a remarkable increase in the response and sensitivity of the Au-modified ZnO films, especially towards nitrogen dioxide and ethanol. The results for the Au-modified ZnO films report about 47 times higher response to 10 ppm of nitrogen dioxide as compared to the non-modified structures with a sensitivity of 39.96% ppm−1 and a limit of detection of 26 ppb to this gas. These results are attributed to the cumulative effects of several factors, such as the presence of oxygen vacancies, the gas-sensing mechanism influenced by the nano-interfaces formed between ZnO and Au, and the catalytic nature of the Au nanoparticles.

A NONLOCAL STRUCTURAL DERIVATIVE MODEL BASED ON THE CAPUTO FRACTIONAL DERIVATIVE FOR SUPERFAST DIFFUSION IN HETEROGENEOUS MEDIA

Superfast diffusion exists in various complex anisotropic systems. Its mean square displacement is an exponential function of time proved by several theoretical and experimental investigations. Previous studies have studied the superfast diffusion based on the time-space scaling local structural derivatives without considering the memory of dynamic behavior. This paper proposes a nonlocal time structural derivative model based on the Caputo fractional derivative to describe superfast diffusion in which the structural function is a power law function of time. The obtained concentration of the diffusive particles, i.e. the solution of the structural derivative model is a double-sided exponential distribution. The derived mean square displacement is a Mittag–Leffler function of time, which generalizes the exponential case. To verify the feasibility of the model, the charge and energy transfer at nanoscale interfaces in solar cells and the dynamics of the dripplons between two graphene sheets are employed. Compared with the existing models, the fitting results indicate that the proposed model is more accurate with higher credibility. The properties of the nonlocal structural derivative model with different structural functions are also discussed.

Three-Dimensional Optical Analysis of Ferroelectric Domain Walls

This chapter presents the latest results demonstrating the flexibility and sensitivity of optical methods for the investigation of the physical properties of DWs in 3D. Domain walls in ferroelectric materials are nanoscale interfaces separating regions with different orientation of the polarization. They have long been considered as imperfections affecting the overall macroscopic properties of ferroelectrics. However, the recently discovered rich and diverse local physical properties of ferroelectric DWs have transformed these domain boundary regions into individual nanostructures with significant fundamental interest and potentially viable application in nanoelectronic device components. This chapter emphasizes the important contribution of both nonlinear and linear optical microscopy in different geometries (transmission, reflection, and non-collinear geometry) to access the detailed morphology of ferroelectric domain walls, obtain their 3D profile, access their internal structure, and establish correlations with their electronic properties.