Sustainable Synthesis of Highly Functionalized Activated Carbon using Plasma Technology.

Surface functionalized activated carbon (SFAC) has been used for several applications, including adsorption, catalysis and energy storage materials. Existing chemical and physical activation methods for surface functionalization are mostly identified as expensive, inefficient, and non-green methods. Plasma, known as the fourth state of matter, has recently been recognized as an attractive and sustainable method for introducing a higher degree of surface functionality to activated carbon. It also improves the bulk chemical structure and the properties of SFAC. The surface functionalization process is governed by discharge gas, discharge source, discharge efficiency and discharge time. The majority of researchers have utilized oxygen plasma as the discharge gas. However, ammonia, carbon dioxide, atmospheric air, specific gases such as chlorine and hydrogen sulfide, and neutral gases such as nitrogen and argon have also been used as the discharge gas. These plasma activations were conducted under different power conditions (W to kW) and varying treatment times (seconds to hours) using different plasma sources such as dielectric barrier discharge (DBD), arc, radio frequency (RF) and microwave (MW) for the surface functionalization. Most of the researchers have experienced both positive and negative co-relationships between principal parameters and surface functional groups (SFGs), surface area, porosity and other surface features such as roughness and hydrophilicity. However, a comprehensive review on the effects of these parameters on the final material properties is lacking. Therefore, this Review focuses on the recent developments in the utilization of plasma as a surface activation technique for activated carbon. Furthermore, an in-depth analysis of the relationship between experimental parameters and the resultant surface features of activated carbon is carried out and discussed. The functionalization mechanisms related to plasma activation have also been illustrated. The aging effect, which negatively impacts surface functionalized activated carbon, is also emphasized. Finally, the recent advances in applications of SFAC, challenges and future perspectives are discussed in detail.

A Novel Green Approach to Synthesize Curcuminoid-Layered Double Hydroxide Nanohybrids: Adroit Biomaterials for Future Antimicrobial Applications.

Thermal instability, photodegradation, and poor bioavailability of natural active ingredients are major drawbacks in developing effective natural product-based antimicrobial formulations. These inherited issues could be fruitfully mitigated by the introduction of natural active ingredients into various nanostructures. This study focuses on the development of a novel green mechanochemical synthetic route to incorporate curcuminoids into Mg-Al-layered double hydroxides. The developed one-pot and scalable synthetic approach makes lengthy synthesis procedures using toxic solvents redundant, leading to improved energy efficiency. The hydrotalcite-shaped nanohybrids consist of surface and interlayer curcuminoids that have formed weak bonds with layered double hydroxides as corroborated by X-ray diffractograms, X-ray photoelectron spectra, and Fourier transmission infrared spectra. The structural and morphological properties resulted in increased thermal stability of curcuminoids. Slow and sustained release of the curcuminoids was observed at pH 5.5 for a prolonged time up to 7 h. The developed nanohybrids exhibited zeroth-order kinetics, favoring transdermal application. Furthermore, the efficacy of curcuminoid incorporated LDHs (CC-LDH) as an anticolonization agent was investigated against four wound biofilm-forming pathogens, Pseudomonas aeruginosa, Staphylococcus aureus, methicillin-resistant Staphyloccocus aureus, and Candida albicans, using a broth dilution method and an in vitro biofilm model system. Microbiological studies revealed a 54-58% reduction in biofilm formation ability of bacterial pathogens in developed nanohybrids compared to pure curcuminoids. Therefore, the suitability of these green-chemically synthesized CC-LDH nanohybrids for next-generation antimicrobial applications with advanced dermatological/medical properties is well established.

Molecular structure of selected tuber and root starches and effect of amylopectin structure on their physical properties.

The objectives of this study were to characterize starches isolated from potato, canna, fern, and kudzu, grown in Hangzhou, China, for potential food and nonfood applications and to gain understandings of the structures and properties of tuber and root starches. Potato and canna starches with B-type X-ray patterns had larger proportions of amylopectin (AP) long branch chains (DP >or=37) than did fern (C-type) and kudzu (C(A)-type) starches. The analysis of Naegeli dextrins suggested that fern and kudzu starches had more branch points, alpha-(1,6)-D-glycosidic linkages, located within the double-helical crystalline lamella than did the B-type starches. Dispersed molecular densities of the C- and C(A)-type APs (11.6-13.5 g/mol/nm(3)) were significantly larger than those of the B-type APs (1.4-6.1 g/mol/nm(3)) in dilute solutions. The larger proportion of the long AP branch chains in the B-type starch granules resulted in greater gelatinization enthalpy changes (Delta H). Retrograded kudzu starch, which had the shortest average chain length (DP 25.1), melted at a lower temperature (37.9 degrees C) than the others. Higher peak viscosities (550-749 RVU at 8%, dsb) of potato starches were attributed to the greater concentrations of phosphate monoesters, longer branch chains, and larger granule sizes compared with other tuber and root starches.