Preparation of kapa carrageenan-based acidic heterogeneous catalyst for conversion of sugars to high-value added materials.

A novel composite based on kappa-Carrageenan (κC) was prepared using N,N-methylene bisacrylamide (MBA) as the crosslinking agent. 5-Hydroxymethylfurfural (5-HMF) was produced by catalytic dehydration of fructose and glucose with MBA grafted κC (κC-g-MBA) as the solid acid catalyst due to sulfonic acid groups in biopolymer skeletons. Various reaction parameters such as optimization of the quantity of the catalyst, temperature, reaction time, and solvent were performed. It was established that for fructose dehydration, the best reaction conditions were the 160 °C as the optimized reaction temperature and 1 h reaction time, respectively. Under these conditions, the HMF yield and fructose conversion were 94.2% and 95.5%, respectively. Furthermore, 160 °C and 2 h were the best reaction temperature and reaction time for glucose dehydration, respectively. Under similar conditions, the HMF yield and glucose conversion are 47% and 93%, respectively. The catalyst was readily prepared from inexpensive materials with considerable reusability and reactivity.

Fabrication and characterization of nanobiocomposite scaffold of zein/chitosan/nanohydroxyapatite prepared by freeze-drying method for bone tissue engineering.

In this investigation, porous composite scaffolds were prepared using a freeze-drying procedure by mixing zein (ZN), chitosan (CS) and nanohydroxyapatite (nHAp) in different inorganic/organic weight ratios. The gained nanocomposite scaffolds were studied using X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and N2-adsorption-desorption technique. Also, swelling, porosity, mechanical properties, biomineralization capability, degradation, cell attachment, and cell viability of the composite scaffolds were studied. The results showed a porous nature with acceptable pore dimensions and interconnections for cell penetration and colonization. In addition, the cytocompatibility of the ZN/CS/nHAp scaffolds was surveyed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) evaluation and cell attachment studies using human bone cancer cells. Studies indicated non- toxicity to the cells, and the cells were found to be attached to the pore walls within the scaffolds. The results related to physicochemical properties and superior cytocompatibility suggested that ZN/CS/nHAp scaffold could be potential candidate materials for the tissue engineering.

Chitosan /Zeolite Y/Nano ZrO2 nanocomposite as an adsorbent for the removal of nitrate from the aqueous solution.

In the present study, a series of chitosan/Zeolite Y/Nano Zirconium oxide (CTS/ZY/Nano ZrO2) nanocomposites were made by controlling the molar ratio of chitosan (CTS) to Zeolite Y/Nano Zirconium oxide in order to remove nitrate (NO3-) ions in the aqueous solution. The nanocomposite adsorbents were characterized by XRD, FTIR, BET, SEM and TEM. The influence of different molar ratios of CTS to ZY/Nano ZrO2, the initial pH value of the nitrate solution, contact time, temperature, the initial concentration of nitrate and adsorbent dose was studied. The adsorption isotherms and kinetics were also analyzed. It was attempted to describe the sorption processes by the Langmuir equation and the theoretical adsorption capacity (Q0) was found to be 23.58mg nitrate per g of the adsorbent. The optimal conditions for nitrate removal were found to be: molar ratio of CTS/ZY/Nano ZrO2: 5:1; pH: 3; 0.02g of adsorbent and temperature: 35°C, for 60min. The adsorption capacities of CTS, ZY, Nano ZrO2, CTS/Nano ZrO2, CTS/ZY and CTS/ZY/Nano ZrO2 nanocomposites for nitrate removal were compared, showing that the adsorption ability of CTS/ZY/Nano ZrO2 nanocomposite was higher than the average values of those of CTS (1.95mg/g for nitrate removal), ZY, Nano ZrO2, CTS/Nano ZrO2, and CTS/ZY.

Nano-composite of silk fibroin-chitosan/Nano ZrO2 for tissue engineering applications: fabrication and morphology.

A scaffold possessing certain desired features such as biodegradation, biocompatibility, and porous structure could serve as a template for tissue engineering. In the present study, silk fibroin (SF), chitosan (CS) and zirconia (Nano ZrO2) were all combined using the freeze drying technique to fabricate a bio-composite scaffold. The composite scaffold (SF/CS/Nano ZrO2) was characterized by SEM, XRD, TGA, BET and FT-IR studies. The scaffold was found to possess a porous nature with pore dimensions suitable for cell infiltration and colonization. The presence of zirconia in the SF/CS/Nano ZrO2 scaffold led to an increase in compressive strength and water uptake capacity while at the same time decreasing the porosity. Cytocompatibility of the SF/CS/Nano ZrO2 scaffold, assessed by MTT assay, revealed non-toxicity to the Human Gingival Fibroblast (HGF, NCBI: C-131). Thus, we suggest that SF/CS/Nano ZrO2 composite scaffold is a potential candidate to be used for tissue engineering.

Synthesis, characterization and application of various types of alumina and nano-γ-alumina sulfuric acid for the synthesis of 2,5-disubstituted 1,3,4-oxadiazoles.

An efficient and green protocol for the synthesis of 2,5-disubstituted 1,3,4-oxadiazoles by one-pot reaction of different aromatic carboxylic acids and benzoyl hydrazides using natural alumina, alumina sulfuric acid (ASA), nano-γ-alumina and nano-γ-alumina sulfuric acid (nano-γ-ASA) under microwave irradiation and solvent-free conditions was developed. Short reaction times, mild reaction conditions, easy work-up, and high yields are the main advantages of this methodology. The catalysts could be recovered and reused for the subsequent reactions without any appreciable loss of efficiency.

Anti-inflammatory drugs interacting with Zn (II) metal ion based on thiocyanate and azide ligands: synthesis, spectroscopic studies, DFT calculations and antibacterial assays.

Zinc (II) complexes with non-steroidal anti-inflammatory drugs (NSAIDs) naproxen (nap) and ibuprofen (ibu) were synthesized in the presence of nitrogen donor ligands (thiocyanate or azide). The complexes were characterized by elemental analysis, FT-IR, (1)H NMR and UV-Vis spectroscopes. The binding modes of the ligands in complexes were established by means of molecular modeling of the complexes, and calculation of their IR, NMR and absorption spectra at DFT (TDDFT)/B3LYP level were studied. The experimental and calculated data verified monodentate binding through the carboxylic oxygen atoms of anti-inflammatory drugs in the zinc complexes. The calculated (1)H, FT-IR and UV-Vis data are in better agreement with the experimental results, and confirm the predicted tetrahedral structures for the Zn (II) complexes. In addition to DFT calculations of complexes, natural bond orbital (NBO) was performed at B3LYP/6-31+G(d,p) level of theory. Biological studies showed the antibacterial activity of zinc complexes against Gram-positive and Gram-negative bacterial strains.

A periodic density functional theory study of tetrazole adsorption on anatase surfaces: potential application of tetrazole rings in dye-sensitized solar cells.

A density functional theory (DFT) method (periodic DMol(3)) with full geometry optimization was used to study the adsorption of tautomeric forms of tetrazole on anatase TiO2 (101), (100), and (001) surfaces. It was found that the adsorption of tetrazole on the TiO2 surfaces does not proceed via a dissociative process, and negative shifts in the Fermi level of TiO2 were noted upon N-containing heterocycle adsorption. The configuration of the tetrazole during adsorption and the corresponding adsorption energies on different surfaces and sites were estimated. In addition, it was found that tetrazole may be adsorbed on TiO2 surfaces through an interaction between a cation on the surface and a lone pair on the N1 or N2 atom of the tetrazole molecule. The results indicate that the adsorption of tetrazole through the N2 position (leading to the 1H tautomer) on an anatase TiO2 surface is favored over adsorption through the N1 position. In addition, it was observed that the photocatalytic activity of tetrazole-doped TiO2 is higher than that of a pure anatase TiO2 surface.

MP2, DFT and ab initio calculations on thioxanthone.

Density functional theory (DFT), HF and MP2 calculations have been carried out to investigate thioxanthone molecule using the standard 6-31+G(d,p) basis set. The results of MP2 calculations show a butterfly structure for thioxanthone. The calculated results show that the predicted geometry can well reproduce the structural parameters. The predicted vibrational frequencies were assigned and compared with experimental IR spectra. A good harmony between theory and experiment is found. The theoretical electronic absorption spectra have been calculated using CIS method. (13)C and (1)H NMR of the title compound have been calculated by means of B3LYP density functional method with 6-31+G(d,p) basis set. The comparison of the experimental and the theoretical results indicate that density functional B3LYP method is able to provide satisfactory results for predicting NMR properties.

Linear free energy relationship for the anomeric effect: MP2, DFT and ab initio study of 2-substituted-1,4-dioxanes.

The anomeric effect of 2-substituted 1,4-dioxane derivatives was calculated and compared with the values for substituted cyclohexane. The bond lengths, bond angles, torsion angles, and relative energies of axial and equatorial conformers of 2-substituted 1,4-dioxanes were calculated by the second-order Møller-Plesset (MP2), density functional theory (DFT/B3LYP), and Hartree-Fock (HF) methods using 6-31G(∗) basis set. The energy differences between the axial and equatorial conformers, endo and exo-anomeric effects, repulsive non-bond and H-bonding interactions were investigated. A linear free energy relationship (LFER) between calculated (MP2/6-31G(∗)) anomeric effect and inductive substituent constants (σ(I)) was obtained for 2-substituted-1,4-dioxanes (slope=6.19 and r(2)=0.967). The calculated energy differences indicate lower equatorial orientation for 2-substituted-1,4-dioxanes compared to the 2-substituted-tetrahydropyrans. The contribution of resonance, hyperconjugation, inductive, steric, hydrogen bonding, electrostatic interaction, and level of theory influences the anomeric effect.

Spectroscopic, quantum chemical DFT/HF study and synthesis of [2.2.1] hept-2'-en-2'-amino-N-azatricyclo [3.2.1.0(2,4)] octane.

The compound 4-N-bicyclo [2.2.1] hept-2'-en-2'-amino-N-azatricyclo [3.2.1.0(2,4)] octane (2) has been synthesized and characterized by elemental analysis, IR, UV-vis, mass and NMR. Density functional theory (DFT) and Hartree-Fock (HF) calculations have been carried out for the title compound by using the standard 6-31G* basis set. The calculated results show that the predicted geometry can well reproduce the structural parameters. Predicted vibrational frequencies have been assigned and compared with experimental IR spectra and they complement each other. The theoretical electronic absorption spectra have been calculated by using CIS, TD-DFT and ZINDO methods. The (13)C NMR and (1)H NMR of compound (2) have been calculated by means of Becke 3-Lee-Yang-Parr (B3LYP) density functional method with 6-31G* basis set. Comparison between the experimental and the theoretical results indicates that density functional B3LYP method is able to provide satisfactory results for predicting NMR properties. On the basis of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated.

Experimental and CIS, TD-DFT, ab initio calculations of visible spectra and the vibrational frequencies of sulfonyl azide-azoic dyes.

The detailed experimental and computational analysis [Hartree-Fock (HF), Time-Dependent Density-Functional Theory (TD-DFT) and Second-Order Møller-Plesset Perturbation Theory (PM2) levels of theory at standard 6-31G* basis set] of structure, infrared spectra and visible spectra of azo dyes are investigated. The optimized geometries and calculated vibrational frequencies are evaluated via comparison with experimental values. The vibrational spectral data obtained from solid phase FT-IR spectra are assigned based on the results of the theoretical calculations. The observed spectra are found to be in good agreement with the calculated values. The geometry optimization yields a planar conformation for phenyl rings with azo moiety. The energy and oscillator strength calculated by Configuration Interaction Singles (CIS) complements the Time-Dependent Density-Functional Theory (TD-DFT) results and the experimental findings. Unfortunately, PM2 method could not predict vibrational frequencies and visible spectra of the azo dyes under conditions of this investigation.

Vibrational spectra and assignments using ab initio and density functional theory analysis on the structure of biotin.

Density functional theory (DFT) and Hartree-Fock calculations were performed using the following models: HF/6-311G(d), B3LYP/6-311G(d), B3LYP/6-311+G(d) and B3PW91/6-311G(d) calculations were performed for biotin. It has been characterized by IR and X-ray. The calculated results show that the predicted geometry can well reproduce the structural parameters. Predicted vibrational frequencies have been assigned and compared with experimental IR spectra and they supported each other. On the basis of vibrational analyses, the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between Cp,m degrees, Sm degrees, Hm degrees and temperatures.

DFT and ab initio study of structure of dyes derived from 2-hydroxy and 2,4-dihydroxy benzoic acids.

We present a detailed analysis of the structural, infrared spectra and visible spectra of a series of azo dyes preparation of salicylic acid and 2,4-dihydroxy benzoic acid derivatives as the coupling component. The preparation of these azo dyes with salicylic acid and 2,4-dihydroxy benzoic acid derivatives (salicylic acid, methyl salicylate, ethyl salicylate, butyl salicylate, methyl 2,4-dihydroxy benzoate, ethyl 2,4-dihydroxy benzoate, salicylaldehyde, salicylamide, 2,4-dihydroxy benzamide, salicylaldoxime) have been investigated theoretically by performing HF and DFT levels of theory using the standard 6-31G* basis set. The optimized geometries and calculated vibrational frequencies are evaluated via comparison with experimental values. The vibrational spectral data obtained from solid phase FT-IR spectra are assigned modes based on the results of the theoretical calculations. The observed spectra are found to be in good agreement with the calculations.

DFT and ab initio calculations of the vibrational frequencies and visible spectra of triazenes derived from cyclic amines.

We present a detailed analysis of the structural, infrared spectra and visible spectra of the 4-substituted aminoazo-benzenesulfonyl azides. The preparation of 4-sulfonyl azide benzenediazonium chloride with cyclic amines of various ring sizes (pyrrolidine, piperidine, 4-methylpiperidine, N-methylpiperazine, morpholine and hexamethyleneimine) have been investigated theoretically by performing HF and DFT levels of theory using the standard 6-31G* basis set. The optimized geometries and calculated vibrational frequencies are evaluated via comparison with experimental values. The vibrational spectral data obtained from solid phase FT-IR spectra are assigned modes based on the results of the theoretical calculations. The observed spectra are found to be in good agreement with the calculations.