In the light of recent experimental as well as theoretical studies, we summarize our present understanding of polar oxide surfaces and examine fundamental issues regarding their stability. The focus is on the surface atomic configurations (relaxations, reconstructions, non-stoichiometry, etc) obtained under specific preparation conditions and their associated electronic structure. We discuss several mechanisms at work on polar surfaces, such as relaxation effects, change of covalency in the surface layers, partial filling of surface states, and stoichiometry variations, and try to assess their actual efficiency for cancelling the polarity.

https://iopscience.iop.org/article/10.1088/0953-8984/12/31/201/pdf

Polar oxide surfaces

Epitaxial growth and properties of thin film oxides

Prussian blue (PB) modified γ-Fe2O3 magnetic nanoparticles (MNPs) featuring varying PB proportions were synthesized and characterized by TEM, FTIR, UV-vis, EDS, XRD and XPS. The magnetic properties and peroxidase-like catalytic activity of the synthesized nanoparticles were investigated. With increasing PB content, the magnetism could still maintain a high level. Peroxidase-like activity was enhanced as the PB proportion increased. Catalysis was found to follow Michaelis–Menten kinetics. The calculated kinetic parameters exhibited strong affinity with substrates and high catalytic activity, which are three orders of magnitudes larger than that for magnetite nanoparticles of similar size. Based on the high activity, an enzyme immunoassay model was established: staphylococcal protein A (SPA) was conjugated onto the surface of the nanoparticles to construct a new nanoprobe which was employed to detect IgG immobilized to 96-well plates. The results presented a linear absorbance enhancement with concentration of IgG, suggesting that PBMNPs serve as an inexpensive horseradish peroxidase (HRP) mimic enzyme with potential applications in bio-detection.

Prussian blue modified iron oxide magnetic nanoparticles and their high peroxidase-like activity

This review outlines developments in the growth of crystalline oxides on the ubiquitous silicon semiconductor platform. The overall goal of this endeavor is the integration of multifunctional complex oxides with advanced semiconductor technology. Oxide epitaxy in materials systems achieved through conventional deposition techniques is described first, followed by a description of the science and technology of using atomic layer-by-layer deposition with molecular beam epitaxy (MBE) to systematically construct the oxide-silicon interface. An interdisciplinary approach involving MBE, advanced real-space structural characterization, and first-principles theory has led to a detailed understanding of the process by which the interface between crystalline oxides and silicon forms, the resulting structure of the interface, and the link between structure and functionality. Potential applications in electronics and photonics are also discussed.

S.A. Chambers

Papers

Heteroepitaxial growth of α-Fe2O3, γ-Fe2O3 and Fe3O4 thin films by oxygen-plasma-assisted molecular beam epitaxy