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Topic Review
Actual Symmetry of Symmetric Adducts
This review discusses molecular adducts, whose composition allows a symmetric structure. Such adducts are popular model systems, as they are useful for analyzing the effect of structure on the property selected for study since they allow one to reduce the number of parameters. The main objectives of this discussion are to evaluate the influence of the surroundings on the symmetry of these adducts, steric hindrances within the adducts, competition between different noncovalent interactions responsible for stabilizing the adducts, and experimental methods that can be used to study the symmetry at different time scales. This review considers the following central binding units: hydrogen (proton), halogen (anion), metal (cation), water (hydrogen peroxide). 
  • 854
  • 10 Feb 2022
Topic Review
Cellulose Nanocrystals
Cellulose has both highly ordered crystalline and amorphous regions in varying proportions, depending on its source. Removing the amorphous region influences the structure and crystallinity of the cellulose, resulting in the formation of CNCs. CNCs are needle-like particles made up of cellulose chain segments that have been organized in an almost defect-free crystalline structure with at least one dimension less-than-or-equal-to 100 nm. CNCs are also known as cellulose nanowhiskers, cellulose whiskers, and nanocrystalline cellulose, but CNCs is the most used term. CNCs have a high thermal stability, surface area, and crystallinity compared to bulk cellulose, which has more amorphous fractions. Different types of LCB waste have been used to extract CNCs such as cotton, pineapple leaf, sugarcane bagasse, walnut shell, soy hulls, bamboo fibre, and many more.
  • 853
  • 29 Apr 2022
Topic Review
Biomedical Applications of Quaternized Chitosan
The natural polymer chitosan is the second most abundant biopolymer on earth after chitin and has been extensively explored for preparation of versatile drug delivery systems. The presence of two distinct reactive functional groups (an amino group at C2, and a primary and secondary hydroxyl group at C3 and C6) of chitosan are involved in the transformation of expedient derivatives such as acylated, alkylated, carboxylated, quaternized and esterified chitosan. Amongst these, quaternized chitosan is preferred in pharmaceutical industries owing to its prominent features including superior water solubility, augmented antimicrobial actions, modified wound healing, pH-sensitive targeting, biocompatibility, and biodegradability. It has been explored in a large realm of pharmaceuticals, cosmeceuticals, and the biomedical arena. Immense classy drug delivery systems containing quaternized chitosan have been intended for tissue engineering, wound healing, gene, and vaccine delivery. 
  • 852
  • 11 Aug 2021
Topic Review
Approaches to Preceramic Polymer Fiber Fabrication
The demand for lightweight, high-modulus, and temperature-resistant materials for aerospace and other high-temperature applications has contributed to the development of ceramic fibers that exhibit most of the favorable properties of monolithic ceramics. The preceramic polymer requirements for a fiber concoction include: (1) appropriate rheology for non-Newtonian flows of materials and appropriate viscosity during rotation; (2) reactivity to fuse the fibers for subsequent pyrolysis; (3) controlled degradation during pyrolysis to prevent disorders of the structure, such as scattered material, and to produce high-density fibers with high ceramic performance; (4) controlled formation of nano- or microstructures.
  • 852
  • 15 Jul 2022
Topic Review
N-Type Layered Oxyselenide Thermoelectric Materials
Bi6Cu2Se4O6is a new type of layered oxyselenide thermoelectric material. The crystal structure of Bi6Cu2Se4O6can be regarded as a 1:2 ratio of BiCuSeO and Bi2O2Se heaping along thec-axis by turns, so there are insulative layersBi2O22+and conductive layersCu2Se22−andSe2−in the structure. The Bi6Cu2Se4O6system not only maintains the low thermal conductivity of BiCuSeO but also can utilize the intrinsic electron carrier concentration of Bi2O2Se, considered to be a promisingn-type oxyselenide thermoelectric material.
  • 852
  • 20 Jul 2021
Topic Review
Biodegradable Polymers in Triboelectric Nanogenerators
Triboelectric nanogenerators (TENGs) have attracted much attention because they not only efficiently harvest energy from the surrounding environment and living organisms but also serve as multifunctional sensors toward the detection of various chemical and physical stimuli. In particular, biodegradable TENG (BD-TENG) represents an emerging type of self-powered device that can be degraded, either in physiological environments as an implantable power source without the necessity of second surgery for device retrieval, or in the ambient environment to minimize associated environmental pollution.
  • 852
  • 14 Feb 2023
Topic Review
Graphene Oxide Derivatives
Matrix-assisted laser desorption/ionization (MALDI) has been considered as one of the most powerful analytical tools for mass spectrometry (MS) analysis of large molecular weight compounds such as proteins, nucleic acids, and synthetic polymers thanks to its high sensitivity, high resolution, and compatibility with high-throughput analysis. Despite these advantages, MALDI cannot be applied to MS analysis of small molecular weight compounds (<500 Da) because of the matrix interference in low mass region. Therefore, numerous efforts have been devoted to solving this issue by using metal, semiconductor, and carbon nanomaterials for MALDI time-of-flight MS (MALDI-TOF-MS) analysis instead of organic matrices. Among those nanomaterials, graphene oxide (GO) is of particular interest considering its unique and highly tunable chemical structures composed of the segregated sp2 carbon domains surrounded by sp3 carbon matrix.
  • 851
  • 02 Feb 2021
Topic Review
Multifunctional Polymeric Nanogels for Biomedical Applications
Currently, research in nanoparticles as a drug delivery system has broadened to include their use as a delivery system for bioactive substances and a diagnostic or theranostic system. Nanogels, nanoparticles containing a high amount of water, have gained attention due to their advantages of colloidal stability, core-shell structure, and adjustable structural components. These advantages provide the potential to design and fabricate multifunctional nanosystems for various biomedical applications. Modified or functionalized polymers and some metals are components that markedly enhance the features of the nanogels, such as tunable amphiphilicity, biocompatibility, stimuli-responsiveness, or sensing moieties, leading to specificity, stability, and tracking abilities. 
  • 851
  • 07 Dec 2021
Topic Review
Natural Antiviral Polymers
Natural polymers or biopolymers are classified into polysaccharides, polypeptides (proteins), and nucleic acid polymers (polynucleotides). Natural polymers as components of living systems are derived from plants, animals, and microorganisms.
  • 850
  • 05 May 2022
Topic Review
Historical Perspective on Membrane Science and Technology
Over the last few decades, considerable effort has been devoted to developing better membranes and extending their range of applications to different areas. Membrane processes already have an established role in gas separation and water treatment, and their applications in the food, pharmaceutical, and health areas have been continuously increasing. In the last few years, membrane processes proved to have a key role in biorefinery and bioenergy production processes, namely for process intensification and the recovery and purification of valuable products. Membranes are also a crucial component of electrochemical energy conversion devices, including fuel cells and electrolysers. Moreover, the growing environmental concerns have drawn attention to the use of fossil-based polymers and toxic solvents for membrane fabrication. Therefore, the development of new membranes, using polymers from renewable sources and more sustainable fabrication methods, is being pursued.
  • 850
  • 23 Feb 2022
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