Influence of cellulose nanofibers on the curing behavior of epoxy/amine systems

Epoxy composites were prepared using diglycidyl ether bisphenol F and water-dilutable diglycidyl ether bisphenol A with curing agents, polyoxypropylenediamine and diethylmethylbenzenediamine, in water or dimethylformamide as a solvent. The influence of cellulose nanofibers and solvents on curing kinetics of epoxy composites was investigated. Curing kinetic parameters were calculated using the model-fitting methods and the isoconversional method. Among these, the Sestak–Berggren equation best fit the experimental data. Results indicated that dimethylformamide decreased the reaction rate, whereas water revealed the opposite pattern. Cellulose nanofibers catalyzed the reaction between bisphenol F resins and the aromatic curing agent.     

A Solvent‐Free Procedure for Synthesis of N‐Sulfonylimines Using Microwave Irradiation Catalyzed by ZrO2/S2O8 2− Solid Superacid

Abstract

A solvent‐free synthesis of N‐sulfonylimines from aldehydes with sulfonamides is described using ZrO₂/S₂O₈ ^2? as catalyst under microwave irradiation. This method is fast and high yielding for a range of substrates.     

Activation of Iron (III) and Bismuth (III) Nitrates by Tungstophosphoric Acid: Solvent‐Free Oxidative Deprotection of Oximes to Carbonyl Compounds

Abstract

Tungstophosphoric acid (H₃PW₁₂O₄₀ · 6H₂O) has been used as a catalyst for a simple, rapid, selective, and solvent‐free cleavage of oximes to carbonyl compounds using iron (III) and bismuth (III) nitrates as oxidants.     

Synthesis of Guanylhydrazones Under Microwave Irradiation

Abstract

The reaction of aromatic aldehydes and ketones with aminoguanidine hydrochloride under microwave irradiation (MWI) afforded guanylhydrazones in shorter reaction times and improved yield as compared to the conventional methodology.     

Synthesis of fluorinated malonamides and use in L/L extraction of f-elements

Synthesis of new fluorinated tertiary malonamides (F-malonamides) was accomplished, and their liquid/liquid (L/L) extraction properties with f-elements were investigated. These molecules are fluorinated analogues of well known extractants used in several processes designed towards the treatment of nuclear wastes, and the efficient separation of lanthanides from minor actinides; however, the synthesis of F-malonamides deserved a modification of the general synthetic route commonly employed to prepare H-malonamides. Extraction of neodymium from various aqueous media into both fluorous and classical solvents was studied, which revealed an opposite trend between F-malonamides and H-malonamides: L/L extraction ability is very sensitive to the nitrogen atoms substitution pattern, and the most efficient F-malonamide is compound 3 (R₁ = Me), whereas the best H-malonamide is compound 5 (R₁ = Bu, DMDBTDMA).     

Oxidation of aliphatic alcohols by triethylammonium chlorochromate in non-aqueous medium – A kinetic and mechanistic study

The oxidation of some aliphatic alcohols by triethylammonium chlorochromate (TriEACC) in dimethyl sulfoxide leads to the formation of the corresponding carbonyl compounds. The reaction is first order with respect to TriEACC. The reaction exhibited Michaelis–Menten type kinetics with respect to alcohol. The reaction is catalyzed by hydrogen ions. The hydrogen-ion dependence has the form: k_obs = a + b[H⁺]. The oxidation of [1,1-²H₂] ethanol (MeCD₂OH) exhibits a substantial primary kinetic isotope effect. Oxidation of aliphatic alcohol was studied in 19 different organic solvents. The solvent effect has been analysed using Kamlet’s and Swain’s multi-parametric equation. A suitable mechanism has been proposed.     

MXene: A two-dimensional material in selective water separation via pervaporation

MXene, well-identified as Ti₃C₂T_X, belongs to the family of two-dimensional (2D) materials, which have been currently explored in various applications. Very recently, such materials have been pointed out as potential nanomaterials for advanced solute separations when introduced in membranes, such as ion separation, gas separation, nanofiltration, chiral molecular separation, and solvent separation. This latter separation, generally named Pervaporation (PV), is identified as a highly selective technology for water separations. To date, few pieces of research have been released but providing interesting insights into several solvent (including water) separations. Hence, this brief review aims to analyze and discuss the latest advances for utilizing MXenes for PV membranes. Particular emphasis has been devoted to the relevant outcomes in the field, along with the strategies followed by researchers to tailor membranes. Based on the current findings, the perspectives in the field are also stated.     

Solvent free synthesis,characterization, DFT,cyclic voltammetry and biological assay of Cu(II), Hg(II) and UO2(II) – Schiff base complexes

A series of metal ion complexes was prepared in solid state from Cu(II), Hg(II) and UO₂(II) ions with 3-oxo-3-(2-(2-oxoindolin-3-ylidene)hydrazineyl)-N-phenylpropanamide (H₃L) ligand through solvent free synthesis methodology. The chemical formulae of the new compounds were estimated according to variable spectral and analytical investigations. The ligand exhibited a neutral or mononegative tetradentate mode of coordination towards the central ions inside the octahedral arrangement that proposed for the three complexes. The DFT/B3LYP method was applied under different basis sets (6-31G*or SDD) to optimize the structures of new compounds except the UO₂(II) complex. The computational data were investigated to verify the binding mode that suggested spectrally. Moreover, studies in solution regarding Cu(II) ion via cyclic voltammetry were performed in absence or presence of H₃L, to realize the significant effect of complex formation on the electrochemical manners of copper. The shifts in the potential peaks accompanied by the changes in the values of parameters correspond to kinetic and thermodynamic. Also, the solvation and kinetic characteristics for the cathodic and anodic potential of Cu(II) ion in absence or presence of H₃L at different scan rates, were estimated. Finally, the ligand and copper ion exhibited high affinity towards complexation in solution. Furthermore, the activity of the new compounds towards inhibiting microbes was studied against Staphylococcus aureus (G+) and Escherichia coli (G-) bacteria as well as Candida albicans (fungus) by determining the inhibition zone diameter. Also, both the antioxidant and cytotoxic activity of the isolated compounds were evaluated. Commonly, a remarkable antimicrobial and anticancer activity was appeared with UO₂(II) complex and the ligand. While, the antioxidant activity of all compounds appeared lower.     

Degradation of parathion methyl by reactive sorption on the cerium oxide surface: The effect of solvent on the degradation efficiency

A simple and easily scalable “wet” procedure was used to prepare nanocrystalline cerium oxide capable of destroying the toxic organophosphate pesticide parathion methyl. The synthetic procedure consists of the direct precipitation of cerous salt with aqueous ammonia in the absence of CO₂. The prepared cerium oxide was able to decompose the organophosphate compounds both in nonpolar (e.g., heptane) and polar aprotic (e.g., acetonitrile) solvents. However, in solvents with hydrogen-bond donating ability, the –OH groups on the cerium oxide surface were solvated and inactivated. The preferential solvation model was used to express the experimental dependencies of the cerium oxide degradation efficiency on the composition of the water-acetonitrile mixture. In certain solvent systems, some empirical polarity scales, such as the alpha-scale or the Dimrodth-Richardt parameter ET(30), may be correlated with the degradation efficiency of cerium oxide.     

无溶剂法大量制备高效红光碳点及其在白光器件中的应用

以邻苯二胺、 2,5-二氨基苯磺酸和三氯化铝为原料, 通过无溶剂法大量制备了高效的红色荧光碳点 (R-CDs). 制得的碳点尺寸大约为2.4 nm, 含有13%的氮元素, 主要由高度石墨化的碳核及覆盖在其表面的大量官能团构成. 在不同的波长光激发下, 碳点在乙醇溶液中表现出不依赖于激发的红光发射, 其荧光峰位于 704 nm, 最大量子产率达到22%. 由于R-CDs具有优异的光学性质, 利用其构筑了紫外光激发的碳基白色发光二极管, 其色坐标为(0.33, 0.33), 非常接近自然光. 该研究为高效红色荧光碳点的大量制备提供了一种新路径, 同时拓宽了其在白光器件中的应用.