For oxide semiconductors, the morphology, particle size and oxygen vacancies are usually considered as key influential parameters for photocatalytic degradation of organic pollutants/dyes. It is widely accepted that cation doping not only modifies their phase and microstructures but also introduces variations in oxygen vacancy concentration. Herein, we report the fabrication of sub-10 nm sized pure and indium doped CeO₂ nanocrystals (NCs) via a facile, green hydrothermal method for the investigation of photocatalytic activities. X-ray diffraction and transmission electron microscopy were employed to examine the crystal phase and morphology of the as-prepared nanocrystals. Raman and X-ray photoelectron spectroscopy techniques were implemented to investigate the presence and variations in oxygen vacancy concentration in un-doped and indium doped CeO₂ nanocrystals. The photocatalytic activity results revealed that 10 at% doping is the optimal indium doping level to demonstrate superior dye removal efficiency (∼40%) over un-doped and doped CeO₂ NCs. Moreover, the 10% In-doped CeO₂ nanocrystals expressed excellent cycling stability and superior photocatalytic performance toward other dye pollutants. Finally, on the basis of our findings, a possible photocatalytic mechanism in which indium doping can generate more surface oxygen vacancies in the ceria lattice which delay the electron–hole recombination rates, thus increasing the lifetime of electron–hole separation for enhanced photocatalytic performances was proposed.

For the first time, this work presents a novel room temperature time-effective concept to manipulate the crystallization kinetics and magnetic responses of thin films grown on amorphous substrates. Conventionally, metal-induced crystallization is adopted to minimize the crystallization temperature of the upper-layer thin film. However, due to the limited surface area of the continuous metal under-layer, the degree of crystallization is insufficient and post-annealing is required. To expose a large surface area of the metal under-layer, we propose a simple and novel approach of using an Au nanodots array instead of a continuous metallic under-layer to obtain crystallization of upper-layer thin films. Spinel cobalt ferrite (CFO) thin film as a ‘model’ was deposited on an Au nano-dots array to realize this methodology. Our findings revealed that the addition of quantum-sized Au nano-dots as a metal under-layer dramatically enhanced the crystallization of the cobalt ferrite upper layer at room temperature. The appearance of major X-ray diffraction peaks with high intensity and well-defined crystallized lattice planes observed via transmission electron microscopy confirmed the crystallization of the CFO thin film deposited at room temperature on 4 nm-sized Au nano-dots. This crystallized CFO thin film exhibits 18-fold higher coercivity (H_c = 4150 Oe) and 4-fold higher saturation magnetization (M_s = 262 emu cm⁻³) compared to CFO deposited without the Au under-layer. The development of this novel concept of room-temperature crystallization without the aid of additives and solvents represents a crucial breakthrough that is highly significant for exploring the green and energy-efficient synthesis of a variety of oxide and metal thin films.

We review emerging low-cost solution-processed resistive random-access memory (ReRAM) made of either hybrid nanocomposites or hybrid organo-lead halide perovskites.

Metal oxide nanosheets have potential applications in novel nanoelectronics as nanocrystal building blocks. In this work, the devices with a structure of Au/p-type Co₃O₄ nanosheets/indium tin oxide/glass having bipolar resistive switching characteristics were successfully fabricated. The experimental results demonstrate that the device have stable high/low resistance ratio that is greater than 25, endurance performance more than 200 cycles, and data retention more than 10,000 s. Such a superior performance of the as-fabricated device could be explained by the bulk film and Co₃O₄/indium tin oxide glass substrate interface effect.

Cerium Oxide Nanostructures and their Applications | InTechOpen, Published on: 2016-12-28. Authors: Adnan Younis, Dewei Chu and Sean Li

Spinel cobalt ferrite (CoFe2O4, CFO) nanoparticles (NPs) are a major focus of fundamental science and technological innovation due to their distinctive mix of magnetic, electrical, and chemical characteristics. CFO NPs have outstanding chemical stability, modest saturation magnetism (∼80 emu/g), a high Curie temperature (∼793 K), and significant magnetocrystalline anisotropy. These characteristics, further improved by cation substitution and surface functionalization, enable a wide range of applications. This review provides a comprehensive analysis of CFO NPs, covering their synthesis methods, physicochemical characterization, surface modifications, and diverse applications. We compare the environmental impact, scalability, yield, and particle size control of a variety of synthesis techniques, including co-precipitation, hydrothermal, sol-gel route, combustion method, microemulsion, thermal decomposition, electrochemical synthesis, polyol method, and green synthesis methods. The sustainable alternative of green synthesis, which employs plant- and microbe-mediated biosynthesis, is becoming increasingly important in the biomedical and environmental sectors. Furthermore, we explore advanced surface functionalization techniques that employ monomeric, inorganic, and polymeric stabilizers to improve the biocompatibility and stability of CFO NPs. The effects of cation substitution (such as transition metals and rare-earth dopants) on the physicochemical and magnetic properties of CFO NPs are examined in detail, addressing challenges like cost and stability in real-world applications. Moreover, the present review provides a detailed discussion correlating structural, morphological, magnetic, dielectric, optical, and electrical properties of CFO with synthesis methods and modifications. The traditional energy storage and conversion applications of CFO are comprehensively discussed. Additionally, the review highlights magnetic applications, biomedical applications (e.g., MRI contrast agents, magnetic hyperthermia, and biosensors), the role of CFO in electronics and optoelectronics, purification and catalysis applications, as well as advances in electromagnetic technologies. Emerging applications, including their roles in quantum computing, nanorobotics, tissue engineering, and bioimaging, are also discussed, emphasizing the cutting-edge potential of CFO NPs in multifunctional technologies. The objective of this review is to critically evaluate recent advancements, challenges, and future research directions to bridge the divide in understanding CFO NPs. This systematic evaluation establishes a strong foundation for researchers, allowing them to investigate novel applications of CFO NPs in both current and emerging technological domains.