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Topic Review
2D-MoS2
Two-dimensional (2D) materials are generally defined as crystalline substances with a few atoms thickness.Two-dimensional transition metal dichalcogenide (2D-TMDs) semiconducting (SC) materials have exhibited unique optical and electrical properties. The layered configuration of the 2D-TMDs materials is at the origin of their strong interaction with light and the relatively high mobility of their charge carriers, which in turn prompted their use in many optoelectronic applications, such as ultra-thin field-effect transistors, photo-detectors, light emitting diode, and solar-cells. Generally, 2D-TMDs form a family of graphite-like layered thin semiconducting structures with the chemical formula of MX2, where M refers to a transition metal atom (Mo, W, etc.) and X is a chalcogen atom (Se, S, etc.). The layered nature of this class of 2D materials induces a strong anisotropy in their electrical, chemical, mechanical, and thermal properties. In particular, molybdenum disulfide (MoS2) is the most studied layered 2D-TMD.
  • 4.5K
  • 28 Sep 2021
Topic Review
Structure of Oxide Perovskite
Materials crystalizing in the perovskite crystal structure are common crystals that are currently employed for multiples applications, including transistors, solar cells, light-emitting devices, memories, catalysts, and superconductors.One of the biggest players within the perovskite structures is the family of oxide perovskites. This is a prominent family with the general formula of ABO3, where A commonly designates an alkaline or rare earth metal cation, occupying the 12-fold coordinated cuboctahedral cages of the oxygen sub-lattice, and B stands for a transition-metal cation (e.g., Fe, Ni, Mn, Co, Cu, or Ti) coordinated with six oxygen atoms in an octahedral coordination. In fact, in the perovskite structure, distortions frequently occur due to the deviation from ideal values of ionic size ratios between the different A, B, and O sites of the crystal. In addition, A or B cations may have distinctive sizes and valences that could result into oxygen non-stoichiometry, involving both oxygen excess and/or oxygen deficiency.
  • 4.3K
  • 24 Sep 2021
Topic Review
Mechanical Milling
Mechanical milling (MM) has attracted great attention as a powerful tool for the synthesis of a variety of sophisticated materials, including equilibrium, nonequilibrium (e.g., amorphous, quasicrystals, nanodiamonds, carbon nanotubes, nanocrystalline powders), and nanocomposite materials. The MM is a unique process in that it involves a solid-state interaction between the reactant materials’ fresh powder surfaces at room temperature. As a result, it has been used to fabricate alloys and compounds that are difficult or impossible to acquire using standard melting and casting processes.
  • 2.5K
  • 20 Oct 2021
Topic Review
The Nitrogen Bond
The nitrogen bond in chemical systems occurs when there is evidence of a net attractive interaction between the electrophilic region associated with a covalently or coordinately bound nitrogen atom in a molecular entity and a nucleophile in another, or the same molecular entity. It is the first member of the family of pnictogen bonds formed by the first atom of the pnictogen family, Group 15, of the periodic table, and is an inter- or intra-molecular non-covalent interaction.
  • 2.4K
  • 25 Mar 2022
Topic Review
Covalent Organic Framework (COFs)
Covalent organic frameworks (COFs) are 2D or 3D low density crystalline porous materials with periodically ordered skeletons constituted by organic molecules linked through covalent bonds. They were first reported by Yaghi and collaborators in 2005 from condensation of benzenediboronic acid (BDBA) alone and in the presence of hexahydroxytriphenylene (HHTP) in a simple one-pot procedure at 120 °C, obtaining a boroxine COF (COF-1) and a boronate ester COF (COF-5), respectively. Since then, there has been steady growth in the number of published works dealing with the synthesis, properties, and catalytic applications of COFs.
  • 2.2K
  • 23 Nov 2021
Topic Review
The Phosphorus Bond
The phosphorus bond in chemical systems, which is an inter- or intramolecular noncovalent interaction, occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a covalently or coordinately bonded phosphorus atom in a molecular entity and a nucleophile in another, or the same, molecular entity. It is the second member of the family of pnictogen bonds, formed by the second member of the pnictogen family of the periodic table. 
  • 2.2K
  • 07 Mar 2022
Topic Review
Nucleation in Polymer Crystallization
Nucleation plays a vital role in polymer crystallization, in which chain connectivity and thus the multiple length and time scales make crystal nucleation of polymer chains an interesting but complex subject. Though the topic has been intensively studied in the past decades, there are still many open questions to answer. The final properties of semicrystalline polymer materials are affected by all of the following: the starting melt, paths of nucleation, organization of lamellar crystals and evolution of the final crystalline structures. In this viewpoint, we attempt to discuss some of the remaining open questions and corresponding concepts: non-equilibrated polymers, self-induced nucleation, microscopic kinetics of different processes, metastability of polymer lamellar crystals, hierarchical order and cooperativity involved in nucleation, etc. Addressing these open questions through a combination of novel concepts, new theories and advanced approaches provides a deeper understanding of the multifaceted process of crystal nucleation of polymers.
  • 2.1K
  • 25 Jun 2021
Topic Review
High Pressure Macromolecular Crystallography
Since its introduction in the early 1970s, high pressure crystallography (HPX) has shown great potential for the investigation of different types of matter. Using diamond anvil cells, HPX is an emerging technique that has been rapidly implemented, making it available to biologists, and there is immense potential for utilizing this technique in biological systems in the future. At the molecular level, high-pressure crystallographic investigation provides information on structural characteristics that not only determine the native conformation of a protein but also the conformations with higher free-energy, thus revealing function-related structural changes and properties that can be modified as a result of pressurization. The increase in the number of crystal structures of different macromolecules determined under high pressure over the last five decades can be ascribed mainly to two factors: the emergence of high-pressure cells with very large, open angles, and the advent of third generation synchrotron sources. The use of high pressure crystallography as a research tool has been shown to contribute to the advancements in the basic fields of biochemistry (protein misfolding and aggregation), biophysics (protein stability), and biotechnology (food processing).
  • 1.9K
  • 04 Apr 2023
Topic Review
Germanium Ion Implantation and Annealing
Germanium (Ge) ion implantation into silicon waveguides will induce lattice defects in the silicon, which can eventually change the crystal silicon into amorphous silicon and increase the refractive index from 3.48 to 3.96. A subsequent annealing process, either by using an external laser or integrated thermal heaters can partially or completely remove those lattice defects and gradually change the amorphous silicon back into the crystalline form and, therefore, reduce the material’s refractive index.  In addition, Ge ion implantation and annealing are also demonstrated to enable post-fabrication trimming of ring resonators and Mach–Zehnder interferometers and to implement nonvolatile programmable photonic circuits. 
  • 1.6K
  • 01 Mar 2022
Topic Review
Recent Advances in Fabricating Wurtzite AlN
As a representative ultrawide bandgap (UWBG) semiconductor material, wurtzite aluminum nitride (AlN) material has many excellent properties such as high electron mobility (1100 cm2/Vs), high breakdown voltage (11.7 MV/cm), high piezoelectric coefficient, high thermal conductivity (320 W/m·K), high hardness (nine on the Mohs scale), high corrosion resistance, high chemical and thermal stability, as well as high bulk acoustic wave velocity (11,270 m/s).
  • 1.6K
  • 10 Jan 2022
Topic Review
Ferroelastic Twinning in Minerals
Ferroelastic twinning in minerals is a very common phenomenon. The twin laws follow simple symmetry rules and they are observed in minerals, like feldspar, palmierite, leucite, perovskite, and so forth. The major discovery over the last two decades was that the thin areas between the twins yield characteristic physical and chemical properties, but not the twins themselves. Research greatly focusses on these twin walls (or ‘twin boundaries’); therefore, because they possess different crystal structures and generate a large variety of ‘emerging’ properties. Research on wall properties has largely overshadowed research on twin domains. 
  • 1.6K
  • 15 Jun 2021
Topic Review
Cenospheres Recovery from Fly Ash
Coal fly ash (CFA) is a major global pollutant produced by thermal power plants during the generation of electricity. A significant amount of coal fly ash is dumped every year in the near vicinity of the thermal power plants, resulting in the spoilage of agricultural land. CFA has numerous value-added structural elements, such as cenospheres, plerospheres, ferrospheres, and carbon particles. Cenospheres are spherical-shaped solid-filled particles, formed during the combustion of coal in thermal power plants. They are lightweight, have high mechanical strength, and are rich in Al-Si particles. Due to cenospheres’ low weight and high mechanical strength, they are widely used as ceramic/nanoceramics material, fireproofing material, and in nanocomposites. 
  • 1.2K
  • 28 Sep 2021
Topic Review
Deposit Formation, Coal-Fired Rotary Kiln
The deposit-forming problem is one of the main bottlenecks restricting the yield and production benefit of iron ore pellets produced by coal-fired rotary kilns. In order to implement measures to ensure the efficient production of pellets by coal-fired rotary kilns, the mechanism and influencing factors on the deposit formation were reviewed. The pellet powder and coal ash come together to form the material base of the deposit.
  • 1.2K
  • 08 Sep 2021
Topic Review
Relevance of Crystal Forms in the Pharmaceutical Field
The existence of multiple crystal forms of an active pharmaceutical ingredients (API) is relevant not only for the selection of the best solid material to carry through the various stages of drug development, including the choice of dosage and of excipients suitable for drug development and marketing, but also in terms of intellectual property protection and/or extension. This is because the physico-chemical properties, such as solubility, dissolution rate, thermal stability, processability, etc., of the solid API may depend, sometimes dramatically, on the crystal form, with important implications on the drug’s ultimate efficacy.
  • 1.2K
  • 26 Aug 2022
Topic Review
Valuable Organic Acids
A ruminant-based carboxylate platform based on mixed or undefined anaerobic co-cultures of rumen microorganisms can convert the carbohydrate polymers in the lignocellulosic part of organic waste streams to carboxylic acids that can be upgraded to biofuels or green chemicals.
  • 1.1K
  • 27 Sep 2021
Topic Review
Ethyl Acetate Hydrogenation
Ethyl acetate hydrogenation is the reverse reaction of ethanol dehydrogenation. Tuthenium complexes acting in homogeneous phase, at very low temperatures, promote both ethanol dehydrogenation and ethylacetate hydrogenation.
  • 990
  • 30 Mar 2023
Topic Review
Methods for Protein Crystallization
Proteins are biopolymers consisting of amino acids linked by peptide bonds. A peptide bond is a type of amide bond that occurs during the formation of proteins and peptides as a result of the interaction of the α-amino group (-NH2) of one amino acid with the α-carboxyl group (-COOH) of another amino acid. The main method for determining the spatial structure of a protein is X-ray structural analysis of protein crystals. The main difficulty in applying this method is in obtaining a perfect protein-crystal. 
  • 841
  • 28 Jan 2023
Topic Review
Cubic Silicon Carbide
The cubic silicon carbide is the only polytype that can be grown on silicon wafers. This approach reduces the cost as no SiC substrate is used and only the silicon carbide layer thickness required for the specific application is grown on a cheaper Si substrate. This technology also offers the potential for faster scale-up with wafer size compared with the development of larger diameter hexagonal SiC wafers. In principle, with a large reactor, a 300 mm Si wafer can be obtained using the present process.
  • 832
  • 15 Dec 2021
Topic Review Peer Reviewed
Homogenization Methods of Lattice Materials
The existing methods for analyzing the behaviors of lattice materials require high computational power. The homogenization method is the alternative way to overcome this issue. Homogenization is an analysis to understand the behavior of an area of lattice material from a small portion for rapid analysis and precise approximation. This paper provides a summary of some representative methodologies in homogenization.
  • 802
  • 06 Jun 2022
Topic Review
Lead-Free Perovskite Single Crystals
Lead-free perovskites have received remarkable attention because of their nontoxicity, low-cost fabrication, and spectacular properties including controlled bandgap, long diffusion length of charge carrier, large absorption coefficient, and high photoluminescence quantum yield. Compared with the widely investigated polycrystals, single crystals have advantages of lower trap densities, longer diffusion length of carrier, and extended absorption spectrum due to the lack of grain boundaries, which facilitates their potential in different fields including photodetectors, solar cells, X-ray detectors, light-emitting diodes, and so on. 
  • 777
  • 30 Nov 2021
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