Two-Dimensional Germanium Sulfide Nanosheets as an Ultra-Stable and High Capacity Anode for Lithium Ion Batteries

Lithium ion batteries (LIBs) at present still suffer from low rate capability and poor cycle life during fast ion insertion/extraction processes. Searching for high-capacity and stable anode materials is still an ongoing challenge. Herein, a facile strategy for the synthesis of ultrathin GeS₂ nanosheets with the thickness of 1.1 nm is reported. When used as anodes for LIBs, the two-dimensional (2D) structure can effectively increase the electrode/electrolyte interface area, facilitate the ion transport, and buffer the volume expansion. Benefiting from these merits, the as-synthesized GeS₂ nanosheets deliver high specific capacity (1335 mAh g⁻¹ at 0.15 A g⁻¹), extraordinary rate performance (337 mAh g⁻¹ at 15 A g⁻¹) and stable cycling performance (974 mAh g⁻¹ after 200 cycles at 0.5 A g⁻¹). Importantly, our fabricated Li-ion full cells manifest an impressive specific capacity of 577 mAh g⁻¹ after 50 cycles at 0.1 A g⁻¹ and a high energy density of 361 Wh kg⁻¹ at a power density of 346 W kg⁻¹. Furthermore, the electrochemical reaction mechanism is investigated by the means of ex-situ high-resolution transmission electron microscopy. These results suggest that GeS₂ can use to be an alternative anode material and encourage more efforts to develop other high-performance LIBs anodes.     

Enzymatic Extraction of Bioactive and Self‐Assembling Wool Keratin for Biomedical Applications

Keratin is widely recognized as a high‐quality renewable protein resource for biomedical applications. Despite their extensive existence, keratin resources such as feathers, wool, and hair exhibit high stability and mechanical properties because of their high disulfide bond content. Consequently, keratin extraction is challenging and its application is greatly hindered. In this work, a biological extraction strategy is proposed for the preparation of bioactive keratin and the fabrication of self‐assembled keratin hydrogels (KHs). Based on moderate and controlled hydrolysis by keratinase, keratin with a high molecular weight of approximately 45 and 28 kDa that retain its intrinsic bioactivities is obtained. The keratin products show excellent ability to promote cell growth and migration and are conferred with significant antioxidant ability because of their intrinsically high cysteine content. In addition, without the presence of any cross‐linking agent, the extracted keratin can self‐assemble into injectable hydrogels. The KHs exhibit a porous network structure and 3D culture ability, showing potential in promoting wound healing. This enzyme‐driven keratin extraction strategy opens up a new approach for the preparation of keratin that can self‐assemble into injectable hydrogels for biomedical engineering.     

Biological Applications of Macrocyclic Schiff Base Ligands and Their Metal Complexes: A Survey of the Literature (2005–2019)

This article aims to provide a survey of biological applications of Schiff base macrocycles and their metal complexes, with emphasis given to the synthesis of the compounds and to their uses as antibacterial and antifungal agents. The literature on the subject, published during the 2005–2019 period, is shortly reviewed. This is an informed report collecting information on the addressed topic in a concise systematic way, and can be expected to be useful as a fast literature catalogue for researchers working on this and related domains.     

Synthesis,Characterization and Evaluation of the Antibacterial and Antitumor Activity of HalogenatedSalen Copper (II) Complexes derived from Camphoric Acid

Platinum metal complexes are the most common chemotherapeutics currently used in cancer treatment. However, the frequent adverse effects, as well as acquired resistance by tumor cells, urge the development of effective alternatives. In the recent past, copper complexes with Schiff base ligands have emerged as good alternatives, showing interesting results. Accordingly, and in continuation of previous studies in this area, three new camphoric acid-derived halogenated salen ligands and their corresponding Cu (II) complexes were synthesized and their antitumor activity was evaluated in order to determine the influence of the type and number of halogens present (Br, Cl). The in vitro cytotoxic activity was screened against colorectal WiDr and LS1034 and against breast MCF-7 and HCC1806 cancer cell lines. The results proved the halogenated complexes to be very efficient, the tetrachlorinated Cu (II) complex being the most promising, presenting IC₅₀ of 0.63–1.09 μM for the cell lines studied. The complex also shows selectivity to colorectal cancer cells compared to non-tumor colon cells. It is worth highlighting that the tetrachlorinated Cu (II) complex, our most efficient complex, shows a significantly more powerful antitumor effect than the reference drugs currently used in conventional chemotherapy. The halogenated salen and corresponding complexes were also screened for their antimicrobial activity against four bacterial species-Staphylococcus aureus, Enterococcus faecalis, Escherichia coli and Pseudomonas aeruginosa-and four fungal species-Candida albicans, Candida glabrata, Aspergillus fumigatus and Alternaria alternata. The compounds were found to exhibit moderate to strong antibacterial activity against the bacterial strains studied. NMR studies and theoretical calculations provided some insight into the structure of the ligands and copper complexes. Considering the results presented herein, our work validates the potential use of copper-based chemotherapeutics as alternatives for cancer treatment.     

Electrochemical Characteristics of a Triphenylamine Derivative by Microelectrode Voltammetry

With the objective of understanding the kinetic redox properties of triphenylamine derivatives in association with chemical reactions, for their future application in functional organic semiconductor devices, the electrochemical characteristics of 4‐(2,2‐diphenylethenyl)‐N,N‐bis(4‐methylphenyl)‐benzenamine (TPA) were evaluated. Based on cyclic voltammograms of TPA on Pt disk electrodes with diameters of 300 μm and 10 μm at slow and fast scan rates in an acetonitrile solution, the TPA^.+ is stable, while the TPA²⁺ is unstable. Importantly, the unstable TPA²⁺ appears to break down by a subsequent chemical reaction. A Cottrell plot analysis from chronoamperometry of a solution containing TPA reveals that both the first and second oxidations are one‐electron reactions. Concerning the stabilization mechanism of the first oxidation state of TPA, the results of molecular orbital calculations indicate that the electrons of the HOMO level are distributed in the triphenylamine group, which induces a resonance‐stabilized TPA^.+. Based on these results, TPA/TPA^.+ is suggested to have a sufficient stability for further application in organic semiconductor devices.     

In-situ cation exchange enhances room temperature phosphorescence of a family of metal-organic frameworks

The rational designability and chemical tunability of metal-organic frameworks(MOFs)are enabling tributes to efficaciously enhance their room temperature phosphorescence(RTP)performance.A family of stable anionic MOFs,[Zn₂(4,5-ImDC)₂]M₂(NKU-132,M=(CH₃)₂NH₂or(CH₂CH₃)₂NH₂),featuring significant RTP have been synthesized.By rational cation selection and in-situ replacement from dimethylammonium to diethylammonium,the phosphorescence lifetime is increased from 30.88 to126.3 ms,along with less sensitivity to air.This work provides an anti-quenching and lifetime tuning example for RTP-MOFmaterials via facile host-guest chemistry.     

In Vivo Metabolism Study of Timosaponin BIII in Rat Using HPLC-QTOF-MS/MS

Timosaponin BIII, as one of the steroid saponins isolated from Anemarrhena asphodeloides Bge., was proved to have many pharmacological activities in recent years and became a natural active compound with good development prospect. In the present study, a simple and rapid method using high-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry was developed for the determination of the structures of timosaponin BIII and its metabolites in rats after administrating intragastrically at 300 mg kg⁻¹. By comparing their changes in molecular masses (ΔM), retention times and spectral patterns with those of the parent compound, nine metabolites were detected and identified in urine, and eight in plasma as well as four in brain. It is also indicated that the deglycosylation and oxidation reactions were the main metabolic pathways in the biotransformation of timosaponin BIII in vivo and the structures of the nine metabolites were identified and proposed to be timosaponin BII(M1), the hydroxylated metabolite of TBII(M2), the hydroxylated metabolites of TBIII(M3 and M4), deglycosylation and monooxygenation product of TBIII(M5), the deglycosylation product of TBII(M6), timosaponin AIII(M8), the isomers of timosaponin AIII(M7 and M9).

     

Improving Resolution of Isomeric Flavonoids and Their Glycosides Using Two-Dimensional Liquid Chromatography Coupled With High-Resolution Mass Spectrometry

Chromatographia - The separation of isomers is one of the key issues in analysing complex natural matrices, thus commanding a higher separating power from the applied analytical system. In this...     

Electrospinning Fabrication of SrTiO3 Nanofibers and Their Photocatalytic Activity

Russian Journal of Physical Chemistry A - SrTiO3 nanofibers were fabricated by an electrospinning process. The phase, microstructure and photocatalytic activity of the obtained SrTiO3 nanofibers...