Subject:
All Disciplines Arts & Humanities Biology & Life Sciences Business & Economics Chemistry & Materials Science Computer Science & Mathematics Engineering Environmental & Earth Sciences Medicine & Pharmacology Physical Sciences Public Health & Healthcare Social Sciences
Sort:
Most Viewed Latest Alphabetical (A-Z) Alphabetical (Z-A)
Filter:
All Topic Review Biography Peer Reviewed Entry Video Entry
Topic Review
Insights into Si-Si and Si-H Bond
During the last decades, the search for new methodologies for the synthesis of organosilicon compounds have increased due to the multiple applications in industry, in academy, among other areas. Silicon-hydrogen and silicon-silicon bond activation by d-block metals still represent the most important pathways for obtaining molecular entities that contain, witihin their structures, silane motifs. Although the chemistry of Si-H bond activation is under continue development, Si-Si bonds are poorly characterized and less used and thus, disilanes represent good starting precursors because of their stability towards ambient conditions. The present entry will focus on the physicochemical properties of Si-H and Si-Si bonds, some trends and finally highlighting their impact on the synthesis of metal complexes.
  • 6.6K
  • 15 Feb 2023
Topic Review
Water-Gas Shift Reaction
The water-gas shift reaction (WGSR) describes the reaction of carbon monoxide and water vapor to form carbon dioxide and hydrogen: The water gas shift reaction was discovered by Italian physicist Felice Fontana in 1780. It was not until much later that the industrial value of this reaction was realized. Before the early 20th century, hydrogen was obtained by reacting steam under high pressure with iron to produce iron, iron oxide and hydrogen. With the development of industrial processes that required hydrogen, such as the Haber–Bosch ammonia synthesis, a less expensive and more efficient method of hydrogen production was needed. As a resolution to this problem, the WGSR was combined with the gasification of coal to produce a pure hydrogen product. As the idea of hydrogen economy gains popularity, the focus on hydrogen as a replacement fuel source for hydrocarbons is increasing.
  • 5.3K
  • 22 Nov 2022
Topic Review
Copper(II) Complex
A dinuclear copper(II) complex of (1) (where bipy = 2,2′‑bipyridine, bzt = benzoate and ox = oxalate) was synthesised and characterised by diffractometric (powder and single-crystal XRD) and thermogravimetric (TG/DTG) analyses, spectroscopic techniques (IR, Raman, electron paramagnetic resonance spectroscopy (EPR) and electronic spectroscopy), magnetic measurements and density functional theory (DFT) calculations. The analysis of the crystal structure revealed that the oxalate ligand is in bis(bidentate) coordination mode between two copper(II) centres. The other four positions of the coordination environment of the copper(II) ion are occupied by one water molecule, a bidentate bipy and a monodentate bzt ligand. An inversion centre located on the ox ligand generates the other half of the dinuclear complex. Intermolecular hydrogen bonds and pi-pi for the organisation of the molecules in the solid state. Molar magnetic susceptibility and field dependence magnetisation studies evidenced a weak intramolecular–ferromagnetic interaction (J = +2.9 cm‑1) between the metal ions. The sign and magnitude of the calculated J value by density functional theory (DFT) are in agreement with the experimental data.
  • 5.3K
  • 30 Oct 2020
Topic Review
Production of Electrolytic Manganese Dioxide
The ferromanganese (FeMn) alloy is produced through the smelting-reduction of manganese ores in submerged arc furnaces. This process generates large amounts of furnace dust that is environmentally problematic for storage. Due to its fineness and high volatile content, this furnace dust cannot be recirculated through the process, either. Conventional MnO2 production requires the pre-reduction of low-grade ores at around 900 °C to convert the manganese oxides present in the ore into their respective acid-soluble forms; however, the furnace dust is a partly reduced by-product. A hydrometallurgical route is proposed to valorize the waste dust for the production of battery-grade MnO2. By using dextrin, a cheap organic reductant, the direct and complete dissolution of the manganese in the furnace dust is possible without any need for high-temperature pre-reduction. The leachate is then purified through pH adjustment followed by direct electrowinning for electrolytic manganese dioxide (EMD) production. An overall manganese recovery rate of >90% is achieved. 
  • 4.8K
  • 08 Jul 2021
Topic Review
Solketal
Solketal (CAS 100–79–8) has low viscosity at room temperature (~11 cP) and freezing, boiling, and flash points of about −26 °C, 190 °C, and 80 °C, respectively. The density is 1.06 g/cm3 and the vapor pressure is 107.32 mmHg. It has low toxicity, slight odor, and it is non-irritant for humans; due to these characteristics and to the renewable origin, it is considered an environmentally friendly substance. It is completely miscible in water and in most organic compounds, which endows its solvent capacity.
  • 3.3K
  • 07 May 2021
Topic Review
Coal Fly Ash Use in Cement and Concrete
Nowadays, coal is increasingly being used as an energy source in some countries. This coal-fired generation process, however, has the disadvantage that produces large quantities of coal fly ash. Its characteristics differ depending on the combustion conditions and the coal source. Fineness will influence early compressive strength in cement-based materials. The finer the binding material, the higher the early compressive strength. They can be used to produce high-volume fly ash (HVFA) concrete, self-compacting concrete (SCC), concrete for marine infrastructures, pervious concrete, roller compacted concrete (RCC) and so on.
  • 2.6K
  • 14 Dec 2021
Topic Review
Metal-Organic Frameworks
Metal-organic frameworks represent a porous class of materials that are build up from metal ions or oligonuclear metallic complexes and organic ligands. They can be considered as sub-class of coordination polymers and can be extended into one-dimension, two-dimensions, and three-dimensions. Depending on the size of the pores, MOFs are divided into nanoporous, mesoporous, and macroporous items. The latter two are usually amorphous. MOFs display high porosity, a large specific surface area, and high thermal stability due to the presence of coordination bonds. The pores can incorporate neutral molecules, such as solvent molecules, anions, and cations, depending on the overall charge of the MOF, gas molecules, and biomolecules. The structural diversity of the framework and the multifunctionality of the pores render this class of materials as candidates for a plethora of environmental and biomedical applications and also as catalysts, sensors, piezo/ferroelectric, thermoelectric, and magnetic materials.
  • 2.4K
  • 13 Jan 2021
Topic Review
Electron Paramagnetic Resonance
Electron Paramagnetic Resonance, EPR is resonance absorption of microwave quanta by electron spins placed in a swept external magnetic field B at a definite value of magnetic field. Other used names are Electron Magnetic Resonance, EMR and Electron Spin Resonance, ESR.
  • 2.4K
  • 24 May 2021
Topic Review
ZnO and TiO2 Green Synthesis
Over the last two decades, oxide nanostructures have been continuously evaluated and used in many technological applications. The advancement of the controlled synthesis approach to design desired morphology is a fundamental key to the discipline of material science and nanotechnology. These nanostructures can be prepared via different physical and chemical methods; however, a green synthesis approach is a promising way to produce these nanostructures with desired properties with time and energy savings and/or less use of hazardous chemicals. In this regard, ZnO and TiO2 nanostructures are prominent candidates for various applications given their thermal stability, non-toxicity and cost-effective. 
  • 2.2K
  • 06 May 2021
Topic Review
CO2 Hydroboration
The use of CO2 as C1 building block for chemical synthesis is receiving growing attention, due to the potential of this simple molecule as abundant and cheap renewable feedstock. Among the possible reductants used in the literature to bring about CO2 reduction to C1 derivatives, hydroboranes have found various applications, in the presence of suitable homogenous catalysts. The main results obtained since 2016 in the synthetic design of main group, first and second row transition metals for use as catalysts for CO2 hydroboration are summarized.
  • 2.0K
  • 04 Jun 2024
Topic Review
Crystallization of LiNbO3
Due to its piezoelectric, ferroelectric, nonlinear optics, and pyroelectric properties, LiNbO3 crystal has found its wide applications in surface acoustic wave (SAW) devices, optical waveguides, optical modulators, and second-harmonic generators (SHG). LiNbO3 crystallized as R3c space group below Curie temperature shows spontaneous polarization that leads to its ferroelectric and piezoelectric properties. Physical and chemical characteristics of LiNbO3 are mainly determined by Li/Nb ratio, impurity cations, vacancies in a cation sublattice. Different sizes of LiNbO3 ranging from nanoscale and microscale to bulk size have been synthesized by solid state method, hydrothermal/solvothermal method, Czochralski (Cz) growth method, etc. Most basic and applied studies of LiNbO3 focus on its bulk single crystal.
  • 2.0K
  • 17 Dec 2021
Topic Review
Ag2O–MnO2/Graphene Oxide Nanocomposite
Catalytic oxidation of alcohol to their analogous carbonyls is one of the key organic reactions in both scientific and industrial applications, with universal production of 10,000 million tons/year of carbonyls in the 20th century. Such as, aldehyde and ketone derivatives are extensively employed as precursors in insecticide, flame-retardant, cosmetic, confectionery, flavoring, pharmaceutical, and beverage industries. 
  • 1.8K
  • 27 Oct 2020
Topic Review
Layered Oxide Cathodes
Layered intercalation compounds are the dominant cathode materials for rechargeable Li-ion batteries. In this review, we discuss the topology of the layered structure and explain how the structure (1) sets the voltage slope trends among various alkali ions, (2) is critically limited to certain transition metals due to their electronic structure, and (3) controls the alkali diffusion mechanism. 
  • 1.8K
  • 17 Jun 2021
Topic Review
Copper Biological Active Complexes
Very few biological active Cu(II) complexes entered in clinical trials as result of poor water solubility and lipophilicity, low stability as well as in vivo inactivation. Their pharmacological and/or oral administration profile can be improved either by physically encapsulation or by conjugation to an organic matrix via a moiety able to coordinate Cu(II). As result, a large variety of species were developed as delivery carriers such as liposomes, synthetic or natural polymers or dendrimers.
  • 1.8K
  • 28 Dec 2020
Topic Review
Pincer Transition Metal Catalysts for Sustainability
Sustainable solutions are needed to avoid global warming and climate change. Homogeneous catalysis might play a fundamental role for this. Pincer-type complexes are promising in terms of stability, selectivity, efficiency and the use of mild reaction conditions. Pincer complexes have been used in many sustainable chemical reactions, for example hydrogen release and upconversion of CO2, N2, and biomass.
  • 1.7K
  • 08 Apr 2022
Topic Review
Compounds of Thorium
Many compounds of thorium are known, this is because thorium and uranium are the most stable and accessible actinides and are the only actinides that can be studied safely and legally in bulk in a normal laboratory. As such, they have the best-known chemistry of the actinides, along with that of plutonium, as the self-heating and radiation from them is not enough to cause radiolysis of chemical bonds as it is for the other actinides. While the later actinides from americium onwards are predominantly trivalent and behave more similarly to the corresponding lanthanides, as one would expect from periodic trends, the early actinides up to plutonium (thus including thorium and uranium) have relativistically destabilised and hence delocalised 5f and 6d electrons that participate in chemistry in a similar way to the early transition metals of group 3 through 8: thus, all their valence electrons can participate in chemical reactions, although this is not common for neptunium and plutonium.
  • 1.7K
  • 25 Oct 2022
Topic Review
Water Physisorbed on Natural Clinoptilolite
Infrared spectroscopy (FT-IR) can provide very useful information on the nature of water physisorbed on zeolites. The vibrational characteristics of geomorphic clinoptilolite of natural origin and the water physically adsorbed on it have been investigated. In particular, two types of physisorbed water molecules have been identified by combining the FT-IR analysis with a mild thermal drying treatment (1h at 150°C) of the sample: the loosely-bound water and the tightly-bound water.
  • 1.5K
  • 29 Oct 2020
Topic Review
Zirconolite and Murataite for the Immobilization of Actinides
Zirconolite is highly stable in nature, with isotope systems that have been closed for hundreds of million years, making it possible for age determination. Murataite is a very rare mineral, its synthetic counerpart was first discovered in the Synroc matrix from defense waste obtained by sintering. Synthetic zirconolie and murataite can be applied for nuclear waste immobilization. 
  • 1.5K
  • 14 Sep 2022
Topic Review
Rhenium(I) Tricarbonyl Complexes As Photosensitisers
Photodynamic therapy (PDT) is emerging as a significant complementary or alternative approach for cancer treatment. Re(I) tricarbonyl complexes is a new generation of metal-based photosensitisers for PDT that are of great interest in multidisciplinary research.
  • 1.4K
  • 27 Oct 2020
Topic Review
Mechanochemical Synthesis of Nanoparticles
Various solvent-based approaches have been already used to synthesize porous materials. Mechanochemical synthesis is one of the effective eco-friendly alternatives to the conventional synthesis. It adopts the efficient mixing of reactants using ball milling without or with a very small volume of solvents, gives smaller size nanoparticles (NPs) and larger surface area, and facilitates their functionalization, which is highly beneficial for antimicrobial applications.
  • 1.3K
  • 15 Mar 2023
  • Page
  • of
  • 5
Featured Entry Collections
>>

Featured Books

>>
Encyclopedia of Social Sciences
Encyclopedia of COVID-19
Encyclopedia of Fungi
Encyclopedia of Digital Society, Industry 5.0 and Smart City
ScholarVision Creations
Feedback