Although known since the late 19th century, organic–inorganic perovskites have recently received extraordinary research community attention because of their unique physical properties, which make them promising candidates for application in photovoltaic (PV) and related optoelectronic devices. This review will explore beyond the current focus on three-dimensional (3-D) lead(II) halide perovskites, to highlight the great chemical flexibility and outstanding potential of the broader class of 3-D and lower dimensional organic-based perovskite family for electronic, optical, and energy-based applications as well as fundamental research. The concept of a multifunctional organic–inorganic hybrid, in which the organic and inorganic structural components provide intentional, unique, and hopefully synergistic features to the compound, represents an important contemporary target.

Organic–Inorganic Perovskites: Structural Versatility for Functional Materials Design

Recycling of rare earths: a critical review

Two-dimensional (2D) nanosheets, which possess atomic or molecular thickness and infinite planar lengths, are regarded as the thinnest functional nanomaterials. The recent development of methods for manipulating graphene (carbon nanosheet) has provided new possibilities and applications for 2D systems; many amazing functionalities such as high electron mobility and quantum Hall effects have been discovered. However, graphene is a conductor, and electronic technology also requires insulators, which are essential for many devices such as memories, capacitors, and gate dielectrics. Along with graphene, inorganic nanosheets have thus increasingly attracted fundamental research interest because they have the potential to be used as dielectric alternatives in next-generation nanoelectronics. Here, we review the progress made in the properties of dielectric nanosheets, highlighting emerging functionalities in electronic applications. We also present a perspective on the advantages offered by this class of materials for future nanoelectronics.

Two‐Dimensional Dielectric Nanosheets: Novel Nanoelectronics From Nanocrystal Building Blocks

Square Bi2WO6 nanoplates have been successfully synthesized by simple hydrothermal process. The effects of hydrothermal temperature and reaction time on morphologies and sizes of the nanoplates were investigated. These nanoplates are square geometric shapes having their basal plane as the (001) plane of orthorhombic Bi2WO6. On the basis of results of morphologies observation and selected area electron diffraction of series samples, a possible growth mechanism of the nanoplates is revealed. The square laminar shape could be attributed to anisotropic growth along the (001) plane, which is parallel to their intrinsic layer structure. UV−visible diffuse reflection spectra of the prepared Bi2WO6 nanoplates indicate they had absorption in the visible region, but a blue shift appeared compared to their bulk counterparts. Their photocatalytic activities are determined by rhodamine B degradation under visible light irradiation (λ > 400 nm). The reaction constant (k) of the best quality Bi2WO6 nanoplates is three t...

Synthesis of Square Bi2WO6 Nanoplates as High-Activity Visible-Light-Driven Photocatalysts

A wide variety of cation-exchangeable layered transition metal oxides and their relatively rare counterparts, anion-exchangeable layered hydroxides, have been exfoliated into individual host layers, i.e., nanosheets. Exfoliation is generally achieved via a high degree of swelling, typically driven either by intercalation of bulky organic ions (quaternary ammonium cations, propylammonium cations, etc.) for the layered oxides or by solvation with organic solvents (formamide, butanol, etc.) for the hydroxides. Ultimate two-dimensional (2D) anisotropy for the nanosheets, with thickness of around one nanometer versus lateral size ranging from submicrometer to several tens of micrometers, allows them to serve either as an ideal quantum system for fundamental study or as a basic building block for functional assembly. The charge-bearing inorganic macromolecule-like nanosheets can be assembled or organized through various solution-based processing techniques (e.g., flocculation, electrostatic sequential deposition, or the Langmuir-Blodgett method) to produce a range of nanocomposites, multilayer nanofilms, and core-shell nanoarchitectures, which have great potential for electronic, magnetic, optical, photochemical, and catalytic applications.

Nanosheets of oxides and hydroxides: Ultimate 2D charge-bearing functional crystallites.

It is of critical importance to improve toughness, strength, and wear-resistance together for the development of advanced structural materials. Herein, we report on the synthesis of unoxidized graphene/alumina composite materials having enhanced toughness, strength, and wear-resistance by a low-cost and environmentally benign pressure-less-sintering process. The wear resistance of the composites was increased by one order of magnitude even under high normal load condition (25 N) as a result of a tribological effect of graphene along with enhanced fracture toughness (KIC) and flexural strength (σf) of the composites by ~75% (5.60 MPa·m1/2) and ~25% (430 MPa), respectively, compared with those of pure Al2O3. Furthermore, we found that only a small fraction of ultra-thin graphene (0.25–0.5 vol%, platelet thickness of 2–5 nm) was enough to reinforce the composite. In contrast to unoxidized graphene, graphene oxide (G-O) and reduced graphene oxide (rG-O) showed little or less enhancement of fracture toughness due to the degraded mechanical strength of rG-O and the structural defects of the G-O composites.

/pdf/unoxidized-graphene-alumina-nanocomposite-fracture-and-wear-2y59sfb0kk.pdf

Unoxidized Graphene/Alumina Nanocomposite: Fracture- and Wear-Resistance Effects of Graphene on Alumina Matrix

Uranium–organic framework solids, in which uranium building units are connected by bidentate dicarboxylate anions such as succinate, glutarate, and isophthalate, were synthesized; the glutarate and isophthalate compounds contain cavities, in which occluded water and organic templates reside.

/pdf/incorporation-of-uranium-vi-into-metal-organic-framework-1z9t5fdhb4.pdf

Incorporation of uranium(VI) into metal–organic framework solids, [UO2(C4H4O4)]·H2O, [UO2F(C5H6O4)]·2H2O, and [(UO2)1.5(C8H4O4)2]2[(CH3)2NCOH2]·H2O

Recovery of indium from etching waste by solvent extraction and electrolytic refining

The thermal conductivity of layered metal chalcogenides such as MT 2 (M = Mo, W; T = S, Se) shows a marked decrease after exfoliation and subsequent restacking process. Random stacking of two-dimensional crystalline sheets circumvents thermal conduction pathways along a longitudinal direction, which results in a reduction in thermal conductivity. WS 2 and WSe 2 compounds retain p-type conducting behavior after exfoliation and restacking with decreased electrical conductivity due to the change in carrier concentration. MoSe 2 compound exhibits metallic behavior < 130 °C with a small Seebeck coefficient, which results from metastable 1T-MoSe 2 structure of the restacked phase.

http://koreascience.or.kr:80/article/JAKO201034136115388.pdf

Thermal and Electronic Properties of Exfoliated Metal Chalcogenides

Macromolecular nanoplatelets of the ferroelectric oxide Bi4Ti3O12 were synthesized by exfoliation reaction for the first time. Formation of the exfoliated nanoplatelets was confirmed by atomic force microscopy (AFM) and high-resolution transmission electron microscopy (HRTEM).

Jong-Young Kim

Papers

Unoxidized Graphene/Alumina Nanocomposite: Fracture- and Wear-Resistance Effects of Graphene on Alumina Matrix

Incorporation of uranium(VI) into metal–organic framework solids, [UO2(C4H4O4)]·H2O, [UO2F(C5H6O4)]·2H2O, and [(UO2)1.5(C8H4O4)2]2[(CH3)2NCOH2]·H2O

Recovery of indium from etching waste by solvent extraction and electrolytic refining

Thermal and Electronic Properties of Exfoliated Metal Chalcogenides

Macromolecular Nanoplatelet of Aurivillius-type Layered Perovskite Oxide, Bi4Ti3O12