Green microwave-assisted synthesis of cellulose/calcium silicate nanocomposites in ionic liquids and recycled ionic liquids

Fabrication of biomass materials by a microwave-assisted method in ionic liquids allows the high value-added applications of biomass by combining three major green chemistry principles: using environmentally preferable solvents, using an environmentally friendly method, and making use of renewable biomass materials. Herein, we report a rapid and green microwave-assisted method for the synthesis of the cellulose/calcium silicate nanocomposites in ionic liquids and recycled ionic liquids. These calcium silicate nanoparticles or nanosheets as prepared were homogeneously dispersed in the cellulose matrix. The experimental results confirm that the ionic liquids can be used repeatedly. Of course, the slight differences were also observed using ionic liquids and recycled ionic liquids. Compared with other conventional methods, the rapid, green, and environmentally friendly microwave-assisted method in ionic liquids opens a new window to the high value-added applications of biomass.     

Solid acid and microwave-assisted hydrolysis of cellulose in ionic liquid

Solid acid-catalyzed hydrolysis of cellulose in ionic liquid was greatly promoted by microwave heating. H-form zeolites with a lower Si/Al molar ratio and a larger surface area showed a relatively higher catalytic activity. These solid catalysts exhibited better performance than the sulfated ion-exchanging resin NKC-9. Compared with conventional oil bath heating mode, microwave irradiation at an appropriate power significantly reduced the reaction time and increased the yields of reducing sugars. A typical hydrolysis reaction with Avicel cellulose produced glucose in around 37% yield within 8 min.     

Chlorination of cellulose with methanesulphonyl chloride in N,N dimethylformamide and chloral

Treatment of hardwood dissolving sulphate pulp with N,N-dimethylformamide, chloral, and methanesulphonyl chloride at 75° effective rapid and selective chlorination, initially at the primary positions. When most of the primary hydroxyl groups had been replaced, reaction occurred at HO-3 to give 3,6-dichloro-3,6-dideoxy-D-allose residues. 4,6-Dichloro-4,6-dideoxy-D-galactose residues, derived from non-reducing end-groups were detected only in highly chlorinated cellulose. The degradation of cellulose during chlorination was investigated by gel-permeation chromatography.     

Chlorination and phosphorylation of cotton cellulose by reaction with phosphoryl chloride in N,N-dimethylformamide

Native cotton yarn reacts rapidly with phosphoryl chloride in N,N-dimethylformamide to produce highly chlorinated cellulose (degree of substitution of 0.5 or greater), phosphorylated cellulose, and cellulose formate. The ratio of chlorination to phosphorylation was readily controlled by varying the concentration of phosphoryl chloride in N,N-dimethylformamide.Reaction variables studied were the reagent concentration, reaction temperature, and reaction time. The effect that each of these variables has on the tensile and flammability properties of the resultant yarns was investigated. Yarns containing large proportions of chlorine have high tensile-strength and are unusually extensible, whereas yarns containing phosphorus have high flame-resistance. A mechanism for the selective chlorination or phosphorylation of the cotton cellulose is advanced.     

Electronic factors and lipophilicity in the horseradish peroxidase-catalyzed oxidation of N,N-dialkylanilines with hydrogen peroxide and oxygen

Initial rates of N-dealkylation of 15 N, N-dialkylanilines with hydrogen peroxide and oxygen in the presence of the enzyme horseradish peroxidase are interpreted mainly in terms of electron availability on nitrogen. In these cases a mechanism similar to that postulated in the chemical oxidation of these substrates is suggested, and involves the formation of a cation radical. Lipophilicity acts as a limiting factor in the reaction, and highly hydrophilic and hydrophobic substrates deviate from the reactivity suggested by electronic factors toward higher and lower reactivity, respectively.     

Rapid determination of protopine, allocryptopine, sanguinarine and chelerythrine in fruits of Macleaya cordata by microwave-assisted solvent extraction and HPLC-ESI/MS

An isocratic high-performance liquid chromatographic method coupled with electrospray mass spectrometry was developed to determine protopine, allocryptopine, sanguinarine and chelerythrine in fruits of Macleaya cordata. The sample was extracted with hydrochloric acid aqueous solution using microwave-assisted extraction method. The extracts were separated on a C8 reversed-phase HPLC column with acetonitrile:acetate buffer as mobile phase, and full elution of all analytes was realized isocratically within 10 min. The abundance of pseudomolecule ions was recorded using selected ion recording at m/z 354.4, 370.1, 332.5, 348.5 and 338.5 for protopine, allocryptopine, sanguinarine, chelerythrine and the internal standard, jatrorrhizine, respectively. Internal standard curves were used for the quantification of protopine, allocryptopine, sanguinarine and chelerythrine, which showed a linear range of 0.745-74.5, 0.610-61.0, 0.525-105 and 0.375-75 microg/mL, respectively, with correlation coefficients of 0.9995, 0.9992, 0.9993 and 0.9989, and limits of detection of 3.73, 3.05, 1.60 and 1.11 ng/mL, respectively.     

Conductance studies on the interaction of symmetrical tetraalkylammonium iodides with non-electrolytes – sucrose and urea – in N,N-dimethylformamide

The interaction of sucrose and urea with symmetrical tetraalkylammonium iodides in N,N-dimethylformamide (1) has been studied by employing conductance measurements. These studies involved the use of a rather simple, unique technique developed for study of the solute-solute and solute-solvent interactions in non-electrolyte solutions. Our results showed a break at the saturation temperature, indicating a transition in the conductance values. This behavior is explained in terms of the solute-solvent interactions involved in electrolyte-solvent-non-electrolyte systems. The results have been interpreted on the basis of the special, structure-promoting features of the (large) tetraalkylammonium (R₄N⁺) ions, the hydrogen-bonding capabilities of sucrose and urea, the salting-in behavior of R₄NI salts with sucrose and urea, and the one-dimensional, hydrogen-bonded structure of molecules of 1.     

Trimethine cyanine dyes as fluorescent probes for amyloid fibrils: The effect of N,N′-substituents

The effect of various N,N′-substituents in the molecule of benzothiazole trimethine cyanine dye on its ability to sense the amyloid aggregates of protein was studied. The dyes are low fluorescent when free and in the presence of monomeric proteins, but their emission intensity sharply increases in complexes with aggregated insulin and lysozyme, with the fluorescence quantum yield reaching up to 0.42.     

On the structure of the N,N′-dimethylpropyleneurea and dimethylsulfoxide solvated gallium(III) and indium(III) ions and bromide complexes in solution and solid state, and the complex formation of the gallium(III) and indium(III) bromide systems in N,N′-dimethylpropyleneurea

The structures of the N,N′-dimethylpropyleneurea (DMPU) solvated gallium(III) and indium(III) ions have been determined in DMPU solution by means of EXAFS. The gallium(III) ion is five-coordinate with a mean Ga-O bond distance of 1.924(5) Å, while the larger indium(III) ion is octahedrally coordinated with a mean In-O bond distance of 2.146(3) Å. The complex formation equilibria in DMPU for the gallium(III) and indium(III) bromide systems have been studied calorimetrically at 298 K. Three relatively strong complexes are formed in the indium(III) bromide system in DMPU, whereas no stability constants could be established in the gallium(III) bromide system as the heats of complex formation were very close to zero. Gallium(III) bromide is present as DMPU solvated GaBr₃ complexes in solution with three equatorial Ga-Br bonds at 2.328(3) Å, and two Ga-O bonds at 1.92(3) Å in the apical positions of a distorted trigonal bipyramid. The DMPU solvated indium(III) bromide has the same configuration with a mean In-Br bond distance of 2.510(3) Å, and two In-O bonds at 2.201(6) Å. Indium(III) binds three bromides and three Me₂SO molecules through the oxygen atoms in octahedral fac-configuration with mean In-Br and In-O bond distances of 2.630(3) and 2.211(15) Å, respectively.     

Electrochemical properties of copper complexes with unsubstituted and substituted 1,10-o-phenanthrolines in N,N-dimethylformamide solvent

The electrochemical reduction of a series of copper(II) complexes with 1,10-o-phenanthrolines, namely the 1:1 and 1:2 metal:ligand complexes with 2,9-dimethylphenanthroline, 4,7-dimethylphenanthroline and unsubstituted phenanthroline, respectively, has been studied in N,N-dimethylformamide using platinum electrodes. As to the 1:2 complexes, the effect of the presence of substituents with different electronic and steric effects on the phenanthroline ligands has been studied with the aim of rationalizing the different values of the standard potentials which have been measured. Furthermore, the possibility of electrogenerating neutral species, with a formally zerovalent copper centre, exhibiting different stability depending on the nature of the ligands, has been ascertained. In out solvent medium, 1:1 complexes have been found to be in equilibrium with the corresponding 1:2 complexes. A scheme for the reduction of solutions of these compounds, including the different equilibria associated to the electrode charge transfers, has been outlined.     

Environmentally friendly microwave ionic liquids synthesis of hybrids from cellulose and AgX (X = Cl,Br)

The purpose of this article was to explore an environmentally friendly strategy to synthesis of biomass-based hybrids. Herein, microwave-assisted ionic liquids method was applied to fabricate the hybrids from cellulose and AgX (X = Cl, Br) using cellulose and AgNO₃. The ionic liquids act simultaneously as a solvent, a microwave absorber, and a reactant. Ionic liquids provided Cl⁻ or Br⁻ to the synthesis of AgCl or AgBr crystals; thus no additional reactant is needed. The products are characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectrometry (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). The cellulose–Ag/AgCl hybrid and cellulose–Ag/AgBr hybrid were also obtained by using cellulose–AgCl and cellulose–AgBr hybrids as precursors. This environmentally friendly microwave-assisted ionic liquids method is beneficial to the hybrids with high dispersion.     

Synthesis, structure and properties of bis[N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-carboxamidecopper(II)] perchlorate

In this account we report the synthesis, structure and characterization of a dimeric Cu(II) complex, [Cu₂(PaPy₃H)₂](ClO₄)₄ (bis[N,N-bis(2-pyridylmethyl)amine-N-ethyl-2-pyridine-2-carboxamidecopper(II)]). In this complex, the coordination of the designed ligand PaPy₃H to the Cu(II) centers is completed by the bis(picolyl)methyl amine portion of one PaPy₃H unit and the oxygen and pyridine nitrogen atoms of the pyridine-2-carboxamide moiety of a second PaPy₃H ligand. The resulting dimeric complex demonstrates a new mode of coordination of the ligand PaPy₃H.     

Efficient synthesis of a fluorescent tripod detection system for pesticides by microwave-assisted click chemistry

A new tripod molecule containing an aromatic core bearing three peracetylated cyclodextrins was synthesized via a microwave-assisted Huisgen 1,3-dipolar cycloaddition and was studied by fluorescence spectroscopy. The photoluminescent properties of complexation phenomena with different pesticides were evaluated in acetonitrile. Fluorescence titrations have been performed to calculate binding constants, sensitivity factors, and limit of detection of the resulting complexes. 2D NMR experiments confirmed the inclusion of pesticide in the hydrophobic cavity of the macrocycle and validated the supramolecular association responsible for the quenching of the fluorescence.     

Facile synthesis of new 4-aza-podophyllotoxin analogs via microwave-assisted multi-component reactions and evaluation of their cytotoxic activity

A series of new 4-aza-podophyllotoxin analogs containing thiazole unit were synthesized via multi-component reactions of aldehydes, tetronic acid and 2-methylbenzo[d]thiazol-5-amine under microwave irradiation. The method not only provides a valuable tool in design and synthesis of new 4-aza-podophyllotoxin analogs but also has the advantages of atom-economy, environmental-friendliness, good yields and operational simplicity. More importantly, the preliminary evaluation on the cytotoxic activity of this type of new 4-aza-podophyllotoxin analogs has resulted in the finding of several compounds with potent and efficacious cytotoxicity to three carcinoma cell lines M14, MCF7 and SW1116.     

类肌肽4(5)-丙氨酰胺-5(4)-羧酸咪唑的酶促合成及表征

肌肽(β-Ala-L-His)是一种高效抗氧化剂,广泛应用于生物、化工、医药等领域。应用微水相酶促合成类肌肽,效率高价格低,且具有相似性质,开发前景广阔。本研究以L-丙氨酸和4,5-二羧酸咪唑制备类肌肽4(5)-丙氨酰胺-5(4)-羧酸咪唑,正交实验下的最佳合成条件为:四氢呋喃:pH8磷酸缓冲溶液=10:1.6(V/V),L-丙氨酸:4,5-二羧酸咪唑=1:3(m/m),α-胰凝乳蛋白酶:底物=1:200(m/m),35oC下磁力搅拌1.5h。硅胶G60薄层色谱(TLC)分离反应产物,Rf=0.81处出现新斑点;刮下该点纯化后进行紫外扫描,高效液相色谱(HPLC)和核磁共振,紫外光谱253nm处吸收明显增强,310nm处出现新吸收峰;253nm、310nm、330nm高效液相色谱保留时间均为4.0min;13C核磁共振显示8组碳原子。结合胰凝乳蛋白酶的催化机理,得出产物结构为4(5)-丙氨酰胺-5(4)-羧酸咪唑。     

Conventional and microwave-assisted synthesis of ZnO nanorods and effects of PEG400 as a surfactant on the morphology

Conventional and microwave-assisted synthesis of ZnO nanorods have been performed with and without using PEG400. ZnO nanorods were synthesized with 50-250 nm of diameter which depends on the used surfactant and methods. Surfactant effects of PEG400 on the size and morphology of ZnO nanorods were investigated. The microwave method was compared to the conventional heating method. Morphologies were investigated by using scanning electron microscopy (SEM).     

Synthesis, characterization and supramolecular structures of two Ni(II) complexes with potentially heptadentate ligand N,N-bis(2-hydroxybenzyl)-1,3-bis[(2-aminoethyl)amino]-2-propanol

A potentially heptadentate ligand H₃L (N,N^′-bis(2-hydroxybenzyl)-1,3-bis[(2-aminoethyl)amino]-2-propanol) and its two Ni(II) complexes, [Ni(H₂L)H₂O](H₂O)₃ClO₄ (1) and [Ni(H₂L)(H₂O)](H₂O)Cl (2) were prepared and characterized. X-ray structural analyses indicate that complex 1 has a distorted octahedral coordination geometry, with four amine N atoms of H₂L⁻ defining the equatorial plane, one aqua O atom and one phenoxo O atom of the ligand occupying two axial positions, respectively. The Ni(II) center of 2 has coordination geometry similar to that of 1. IR and electronic spectra of 1 and 2 are in agreement with their crystal structural features. Approximately along the ab plane, 2D supramolecular structure of 1 is assembled through multiple hydrogen bonds between hydroxy groups of the ligands, coordinated and crystal lattice H₂O and π-π stacking interactions between adjacent phenyl rings of the ligands, while for that of 2, probably along the a axis, 1D chain structure is also formed by multiple hydrogen bonds, but lack of π-π stacking interactions.     

Preparation and characterization on mechanical and antibacterial properties of chitsoan/cellulose blends

Polysaccharides-based membranes of chitosan and cellulose blends were prepared using trifluoroacetic acid as a co-solvent. Morphology and mechanical property of prepared membranes were studied by Instron and dynamic mechanical thermal analysis. The mechanical and dynamic mechanical thermal properties of the cellulose/chitosan blends appear to be dominated by cellulose, suggests that cellulose/chitosan blends were not well miscible. It is believed that the intermolecular hydrogen bonding of cellulose is supposed to be break down to form cellulose–chitosan hydrogen bonding; however, the intra-molecular and intra-strand hydrogen bonds hold the network flat. The reduced water vapor transpiration rate through the chitosan/cellulose membranes indicates that the membranes used as a wound dressing may prevent wound from excessive dehydration. The chitosan/cellulose blend membranes demonstrate effective antimicrobial capability against Escherichia coli and Staphylococcus aureus, as examined by the antimicrobial test. These results indicate that the chitosan/cellulose blend membranes may be suitable to be used as a wound dressing with antibacterial properties.     

Preparation, characterization and antimicrobial activity of a bio-composite scaffold containing chitosan/nano-hydroxyapatite/nano-silver for bone tissue engineering

In this study, a bio-composite scaffold containing chitosan/nano-hydroxyapatite/nano-silver particles (CS/nHAp/nAg) was developed by freeze drying technique, followed by introduction of silver ions in controlled amount through reduction phenomenon by functional groups of chitosan. The scaffolds were characterized using SEM, FT-IR, XRD, swelling, and biodegradation studies. The testing of the prepared scaffolds with Gram-positive and Gram-negative bacterial strains showed antibacterial activity. The scaffold materials were also found to be non-toxic to rat osteoprogenitor cells and human osteosarcoma cell line. Thus, these results suggested that CS/nHAp/nAg bio-composite scaffolds have the potential in controlling implant associated bacterial infection during reconstructive surgery of bone.