Tài liệu miễn phí Hoá học
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Effect of CNT incorporation on PAN/PPy nanofibers synthesized by electrospinning method
In this study, carbon nanotubes (CNTs) added polyacrylonitrile/polypyrrole (PAN/PPy) electrospun nanofibers were produced. Average diameters of the nanofibers were measured as 268 and 153 nm for 10 and 25 wt% of PPy contents, respectively. A relatively higher strain to failure values (23.3%) were observed for the low PPy content. When as-grown CNTs (1 and 4 wt%) were added into the PAN/PPy blends, disordered nanofibers were observed to form within the microstructure. To improve the interfacial properties of CNTs/PAN/PPy composites, CNTs were functionalized with H2SO4/HNO3/HCl solution.
4/3/2023 11:15:48 PM +00:00
Modeling and optimization of simultaneous degradation of rhodamine B and acid red 14 binary solution by homogeneous Fenton reaction: A chemometrics approach
This study aimed to propose a mathematical method to investigate and optimize the simultaneous elimination process of multiple organic pollutants using the Fenton process. Hence, the treatment of rhodamine B (RB) and acid red 14 (AR14) dyes in their binary solution was studied. Multivariate curve resolution alternating least square (MCR-ALS), a novel chemometric method, was applied along with correlation constraints to resolute the UV-Vis spectrophotometric data, enabling quantification of investigated dyes despite a high spectral overlapping. Response surface methodology was adopted to assess the model and optimize individual and interactive effects of three independent factors (Fe2+, H2O2 and initial pH) on the simultaneous elimination of RB and AR14.
4/3/2023 11:15:38 PM +00:00
Sorption studies of europium on cerium phosphate using Box-Behnken design
Amorphous cerium phosphate was prepared and characterized. Three-level Box-Behnken design (BBD) was employed to analyze the effect of process variables such as initial pH (2–6), contact time (60–180 min), and sorbent amount (0.05–0.15 g) on the sorption capacity of europium. Analysis of variance (ANOVA) revealed that the main effect of initial pH and sorbent amount has a substantial impact on the sorption of Eu(III). Probability F-value (F = 3 × 10 −3 ) and correlation coefficient (R2 = 0.97) point out that the model is in good accordance with experimental data. The maximum sorption capacity of Eu(III) was found to be 42.14 mg g −1 at initial pH 6, contact time of 180 min, and a sorbent amount of 0.05 g.
4/3/2023 11:15:27 PM +00:00
Oxidation of crotyl alcohol by N-chloro-4-methylbenzene sulphonamide in acidic medium and in alkaline media in the presence of os(VIII) catalyst-a kinetic pathway
The kinetic pathway of oxidation of crotyl alcohol by sodium salt of N -chloro-4-methylbenzene sulphonamide (chloramine-T) in acidic and alkaline medium has been studied. The speciation of chloramine-T has been made to suggest a proper and reasonable reaction mechanism. The thermodynamic quantities such as activation energy and activation entropy are evaluated in acidic as well as in catalysed alkaline medium. An anticipated reaction mechanism has been suggested.
4/3/2023 11:15:16 PM +00:00
An anthracene based fluorescent probe for the selective and sensitive detection of Chromium (III) ions in an aqueous medium and its practical application
An anthracene based fluorescent probe, integrated with thiophene moiety, exhibited selective and sensitive detection of chromium (III) ions over other metal ions. Its synthesis was achieved by simple mixing of two commercially available compounds, 2-aminoanthracene, and 2-thiophenecarboxaldehyde, in onestep without the needed complex purification process. The probe molecule (ANT-Th) offered exceptional features such as “turn-on” fluorescence response, low detection limit (0.4 µM), and fast response time (
4/3/2023 11:15:04 PM +00:00
Preparation of rapid (chain-stopped) alkyds by incorporation of gum rosin and investigation of coating properties
In this study, the synthesis, characterization, and properties of a short oil length chain–stopped(rapid) alkyd resin is investigated. Gum rosin modified alkyd resin (RA-GR) was prepared using soybean oil, phthalic anhydride, glycerin and gum rosin acid. An alkyd modified with benzoic acid (RA-BA) was also prepared for comparison. FTIR analyses and GPC measurements of the alkyds were used for characterization. Other properties such as the viscosity, acid value, and solid content of the final resins were determined.
4/3/2023 11:14:49 PM +00:00
The use of water-soluble phthalocyanines as textile dyes in nylon/elastane fabric: Fastness and antibacterial effectiveness
This work reports on dyeing of nylon/elastane fabric with water-soluble phthalocyanines (1-4) bearing quinoline 5-sulfonic acid substituents on the peripheral or nonperipheral positions and determining the antibacterial efficiency of the phthalocyanine compounds and the dyed nylon/elastane fabrics. The light, washing, water, perspiration, and rubbing fastness properties of nylon/elastane fabrics dyed with phthalocyanines were also determined. The results showed that all dyed fabrics showed very good wet fastness values. The lightfastness value of the nylon/elastane fabric dyed with phthalocyanine dye (1) showed a much better value than the others.
4/3/2023 11:14:16 PM +00:00
Preparation, characterization, and binding profile of imprinted semi-IPN cryogel composite for aluminum
Human body is greatly exposed to aluminum due to its high abundance in the environment. This nonessential metal is a threat to the patients of chronic renal disorders, as it is easily retained in their plasma and quickly accumulates in different tissues. Thus, there is great need to remove it from the aqueous environment. In this study, Al3+ imprinted semiinterpenetrating polymer network (semi-IPN)-based cryogel composite was prepared and applied for the purification of environmental and drinking water samples from aluminum. Poly (2-hydroxyethyl methacrylate) (pHEMA) discs were produced via cryogenic treatment and imprinted semi-IPN was introduced to the 3-(trimethoxysilyl) propyl acrylatemodified macroporous cryogel discs.
4/3/2023 11:13:56 PM +00:00
Evaluation of a novel nanocrystalline hydroxyapatite powder and a solid hydroxyapatite/Chitosan-Gelatin bioceramic for scaffold preparation used as a bone substitute material
Artificially fabricated hydroxyapatite (HAP) shows excellent biocompatibility with various kinds of cells and tissues which makes it an ideal candidate for a bone substitute material. In this study, hydroxyapatite nanoparticles have been prepared by using the wet chemical precipitation method using calcium nitrate tetra-hydrate [Ca(NO3)2.4H2O] and di-ammonium hydrogen phosphate [(NH4)2HPO4] as precursors. The composite scaffolds have been prepared by a freeze-drying method with hydroxyapatite, chitosan, and gelatin which form a 3D network of interconnected pores. Glutaraldehyde solution has been used in the scaffolds to crosslink the amino groups (|NH2) of gelatin with the aldehyde groups (|CHO) of chitosan.
4/3/2023 11:13:38 PM +00:00
A review: A comparison of different adsorbents for removal of Cr (VI), Cd (II) and Ni (II)
A review of the studies dealing with the removal of chromium, cadmium, and nickel ions with different adsorbents published in the literature between 2014 and 2018 is given in tabular form, along with the adsorption conditions, adsorption isotherm, and kinetic models applied by the authors to model the experimental data and adsorption capacities. The review focuses on the efficiency of ion removal.
4/3/2023 11:13:29 PM +00:00
One-step synthesis of hierarchical [B]-ZSM-5 using cetyltrimethylammonium bromide as mesoporogen
One-step facile synthesis of boron containing ZSM-5 microspheres is developed using 1,6-diaminohexane as the structure-directing agent and cetyltrimethylammonium bromide as the mesoporogen. High boron incorporation up to Si/B ratio of 38 is achieved and evidenced by the stretching vibrations of B–O–Si at 667cm−1 and 917cm−1 using Fourier-transform infrared spectra. The morphology of the crystals resembles berry-like spheres with sizes approximately 15 µm, which is composed of aggregated nanocrystals having sizes around 450 nm, is observed using scanning electron microscopy.
4/3/2023 11:13:04 PM +00:00
Isothermal compressibility and isobaric thermal shrinkage of a porous α-alumina compact: Thermodynamic calculations
Two methods were proposed to calculate the thermodynamic parameters of porous ceramic compacts depending on their molar volume change with applied pressure and heating temperature, respectively. Molar volume of the porous α-alumina (α-Al 2 O3) compact was evaluated according to literature depending on both the applied pressure at room temperature and the heating temperature at atmospheric pressure. The isothermal compressibility coefficient, Gibbs energy, and work done on the compact by compression were calculated.
4/3/2023 11:12:57 PM +00:00
Corrosion and wear behaviour of highly porous Ti-TiB-TiNx in situ composites in simulated physiological solution
Highly porous Ti matrix composites can be a solution for some of the major clinical concerns for the load bearing implants such as low tribocorrosion resistance, stress shielding, and lack of biological anchorage. In order to respond to these needs, highly porous Ti-TiB-TiNx in-situ composites were synthesized by pressureless sintering using BN as reactant and urea as space holder. Corrosion behaviour was investigated at body temperature, in phosphate buffer saline solution (PBS), by measuring open circuit potential (OCP) and cyclic polarization. Wear behaviour was studied in PBS by reciprocating against a 10 mm diameter alumina ball under 3N of normal load and 1Hz of frequency.
4/3/2023 11:12:42 PM +00:00
Colorimetric cadmium ion detection in aqueous solutions by newly synthesized Schiff bases
Two newly synthesized Schiff bases DMCA and DMBA were used for selective detection of Cd2+ over a wide range of other metal ions in acetonitrile (ACN)/Tris-HCl buffer (10 mM, pH 7.32, v/v 2:1). The sensors can detect Cd2+ ions by colour changes from colourless to orange for DMBA and yellow to reddish for DMCA. Response of the probes towards metal ions was investigated by using UV-vis spectroscopy. The complex stoichiometry between the sensors, DMBA and DMCA, and Cd 2+ was found to be 2:1 and the binding constants were calculated to be 2.65×10 12M−2 and 4.95×10 12M−2 , respectively. The absorbance-based detection limits of DMBA and DMCA were calculated as 0.438 µM and 0.102 µM, respectively. The sensors were also successfully applied to real samples.
4/3/2023 11:12:33 PM +00:00
Improvement of the adhesion of conductive poly(m-toluidine) onto chemically reduced-wool fabrics
Wool has disulphide bonds containing-hydrophobic external keratin layers, which act as a barrier for the modification through coating with hydrophilic materials. For that reason, in this work, to ensure a dense and homogenous conductive polymer coating onto the wool, the fabrics were subjected to the reduction process in the aqueous alkaline medium containing agents that can attack these disulphide bonds. Then, one of the polyaniline derivatives, poly(mtoluidine) (PMT), was coated onto wool by in situ polymerization of m-toluidine sulphate using ammonium persulfate (APS) as an oxidant.
4/3/2023 11:12:24 PM +00:00
Box–Behnken design for removal of uranium(VI) from aqueous solution using poly(ethylene glycol) based dicationic ionic liquid impregnated chitosan
Poly(ethylene glycol) bis(methylimidazolium) di[bis(trifluoromethylsulfonyl)imide] was synthesized as an ionic liquid and impregnated onto chitosan. The removal of uranium(VI) ions from aqueous solution was investigated with batch sorption tests using ionic liquid impregnated chitosan. Response surface methodology based on 3 level Box– Behnken design was applied to analyze the effect of initial pH (4–6), initial concentration (20–60 mg L −1 ), contact time (15–105 min), and temperature (30–50°C) on the uptake capacity of uranium(VI). Main effect of initial concentration, quadratic effect of contact time, and dual effect of initial pH and contact time were found statistically significant based on analysis of variance (ANOVA).
4/3/2023 11:12:13 PM +00:00
2-[(3-Aminoalkyl-(alkaryl-,aryl-))-1 H-1,2,4-triazol-5-yl]anilines: Synthesis and anticonvulsant activity
The presented work is devoted to the development of synthesis methods for novel 2-[(3-aminoalkyl-(alkaryl-, aryl-))-1H -1,2,4-triazolo]anilines. Abovementioned compounds were obtained via hydrazinolysis (Ing-Manske procedure) and acid hydrolysis of corresponding N -acylated{([1,2,4]triazolo[1,5- c ]quinazolin-2-yl)alkyl-(alkaryl-, aryl-)}amines. The regioselectivity of hydrazinolysis and hydrolysis were established. The features of spectral characteristics were studied and discussed. Characteristic patterns of protons signals splitting in 1H NMR of the synthesized compounds were established. The effect of the synthesized compounds on the pentylenetetrazol seizures was studied.
4/3/2023 11:12:05 PM +00:00
Synthesis, characterization and crystal structures of platinum(II) saccharinate complexes with 1,5-cyclooctadiene
The addition of the sac ligand resulted in the replacement of 1 and 2 chlorido ligands in [PtCl2(COD)] to yield 1 and 2, respectively. The structures of the complexes were determined by single crystal X-ray diffraction and showed a distorted square planar coordination geometry around platinum(II). COD acted as a π -donor ligand, while sac was N -coordinated in both complexes. The TG/DTA data indicated that both complexes were thermally stable up to 220°C in air and their thermal decompositions yielded Pt as a final product. Complexes 1 and 2 were also designed as possible precursors to synthesize new mixed-ligand platinum(II) sac complexes in a one-pot reaction.
4/3/2023 11:11:57 PM +00:00
Synthesis and liquid crystalline properties of new triazine-based π-conjugated macromolecules with chiral side groups
In this study, we reported the synthesis of a new tribranched macromolecule liquid crystal with triazine in the centre. The central triazine core is bonded via sequences of Sonigashira coupling to 3 triazine unites through acetylenic bridges. The triazines at the periphery are substituted with 2 chiral citronellyloxy side groups. The salt of the resulting star-shaped macromolecule, which was oily at room temperature, with 4-dodecyloxybenzoic acid at 1:1 ratio exhibited a Smectic C (SmC) mesophase. The liquid crystalline properties of organic salt were investigated using DSC (differential scanning calorimetry) and POM (polarizing optical microscopy).
4/3/2023 11:11:42 PM +00:00
Extraction of heavy metal complexes from a biofilm colony for biomonitoring the pollution
An extraction method was tested for biomonitoring the biofilm samples containing heavy metals. The fractionation of metal complexes was performed via C-18-HPLC-ICP-MS and MALDI-MS, respectively. The extraction power of some reagents was determined for the heavy metal extraction from biofilm samples collected in Erdemli coast in the Mediterranean Sea. The ammonium acetate solution giving the highest extraction results was found as a suitable extraction reagent. The concentration and pH of the ammonium acetate solution were optimized and found as 1 M and 5, respectively. The chromatograms of metal complexes with the C-18-HPLC-ICP-MS system were taken to determine the effect of the pH of the metal complexes.
4/3/2023 11:11:33 PM +00:00
Gas phase polymerization of ethylene towards UHMWPE
For the first time, ultra-high molecular weight polyethylene (UHMWPE) was produced in gas phase process with a new fluidized bed concept where the solids are dispersed phase and the gas is bulk phase as opposed to conventional fluidized bed reactors (FBRs). With this concept, UHMWPE with average molecular weights about 1-6,9 × 10 6 g moles −1 were produced with a commercial supported Ziegler-Natta catalyst by using a gas phase mini semibatch reactor system. Additionally, optimum conditions of gas phase polymerization for the best results of productivity, catalyst activity, molecular weight and crystallinity were determined by Taguchi experimental design and catalyst stability at the optimum condition was tested by video microscopy polymerization.
4/3/2023 11:11:22 PM +00:00
Synthesis and effect of substituent position, metal type on the electrochemical properties of (3-morpholin-4-ylpropoxy) groups substituted cobalt, manganese phthalocyanines
In this work, 4-(3-morpholin-4-ylpropoxy)phthalonitrile 2, 3-(3-morpholin-4-ylpropoxy)phthalonitrile 3, Co(II)Pc and Mn(III)Pcs containing (3-morpholin-4-ylpropoxy) groups at peripheral and nonperipheral positions were synthesized. Phthalonitrile derivatives (2 and 3), Co(II)Pc and Mn(III)Pcs (2a, 2b, 3a, 3b) were characterized by using FT-IR, NMR (only for 2 and 3), mass and UV–Vis (except 2 and 3) spectral data techniques. Also, electrochemistry of (3-morpholin-4-ylpropoxy) group substituted Co(II)Pc and Mn(III)Pcs were inspected by using cyclic voltammetry. Electrochemical studies show that (3-morpholin-4-ylpropoxy) group substituted Co(II)Pc and Mn(III)Pcs electropolymerized on the Pt working electrode.
4/3/2023 11:10:59 PM +00:00
Allylphenoxypiperidinium halides as corrosion inhibitors of carbon steel and biocides
A series of 1-(4-(2-allylphenoxy)butyl)piperidin-1-ium halides (4a-d) was synthesized and characterized via spectroscopic methods (FTIR, 1H NMR). The corrosion inhibition of the synthesized halides on carbon steel in water-salt-hydrocarbon environment, saturated with H2S, was investigated. For this purpose, a series of techniques such as gravimetric measurement, potentiodynamic polarisation, and scanning electron microscope (SEM) were used and some thermodynamic parameters of corrosion process (∆Gads., ∆H0 ads., ∆S0ads.) were evaluated. The steel surface was checked by SEM, and the steel surface showed good surface coverage.
4/3/2023 11:10:40 PM +00:00
A novel fluorimetric method for determination of pseudoephedrine hydrochloride in pharmaceutical formulations and blood serum
An inexpensive, simple, highly sensitive, and rapid fluorimetric method was developed for the analysis of pseudoephedrine hydrochloride at trace levels. The method is based on the recovery of fluorescence of Rh6G dye due to the interaction of pseudoephedrine hydrochloride with Rh6G-Au NPs complex, which results in the release of Rh6G from the complex and halting fluorescence resonance energy transfer between Rh6G and Au NPs. The intensity of fluorescence was directly proportional to the concentration of the analyte, which was used for its determination. Experimental factors were optimized by response-surface methodology.
4/3/2023 11:10:25 PM +00:00
Development and validation of an HPLC method for determination of rofecoxib in bovine serum albumin microspheres
A simple and reliable HPLC method was developed and validated for determination of rofecoxib in bovine serum albumin microsphere. The analyses were performed on a C18 column (150 x 4.6 mm, 5 µm particle size) at room temperature with UV detection at 272 nm. The mobile phase was composed of acetonitrile-0.1% o-phosphoric acid solution in water (1:1, v/v) mixture, and flow rate was set to 1 mL/min. The method was validated according to the international guidelines with respect to stability, linearity range, limit of quantitation and detection, precision, accuracy, specificity, and robustness. The detection and quantification limit of the method were 1.0 µg/mL and 2.5 µg/mL, respectively.
4/3/2023 11:10:17 PM +00:00
Effect of polyelectrolyte complex formation on the antibacterial activity of copolymer of alkylated 4-vinylpyridine
Polymers bearing quaternized 4-vinylpyridine (QVP) groups are known for their antibacterial activities and these polymers can form polyelectrolyte complexes (PEC) with polyanions through electrostatic interactions. PEC formation can be used to adjust the antibacterial activity of polymers of QVP, deliver active molecules, or design antibacterial supramolecular structures. However, the antibacterial activity of PECs of QVP polymers has not been investigated. In this study, a copolymer of QVP was mixed with polyacrylic acid in various molar ratios of components to form PECs. Hydrodynamic diameters and zeta potentials of formed PECs were determined by dynamic and electrophoretic light scattering spectroscopy techniques.
4/3/2023 11:10:09 PM +00:00
Mesoporous starch aerogels production as drug delivery matrices: Synthesis optimization, ibuprofen loading, and release property
The aim of this work was to prepare biodegradable starch aerogels as drug carriers. The effective parameters in the synthesis and the optimal values of these parameters were determined using Minitab experimental design software. Ibuprofen was selected as a model drug for the dissolution study and loaded into optimized aerogel during the last solvent exchange step. The Fourier Transform Infrared Spectroscopy (FTIR) analysis showed that ibuprofen has been successfully loaded into the aerogel matrix without any effect on the aerogel nature. The drug loading was calculated to be 29%. The isotherm of ibuprofen adsorption into aerogels matrices followed from the Freundlich isotherm.
4/3/2023 11:09:59 PM +00:00
Analysis of electrochemical impedance spectroscopy response for commercial lithium-ion batteries: Modeling of equivalent circuit elements
Electrochemical impedance spectroscopy measurements were performed to capture the physically meaningful parameters of commercially available 18650 cylindrical and 2032 coin cells by using the equivalent circuit model. The impedance response of the batteries was systematically investigated and discussed. A detailed analysis was achieved providing a determination of influential factors on the equivalent circuit parameters. The results suggested that the cell type tested here influenced the equivalent circuit elements profoundly. Taguchi analysis indicated that state-of-charge had the highest effect on the cathodic constant-phase-element exponent. The results contribute to full electrochemical analysis that is required for battery characterization.
4/3/2023 11:09:49 PM +00:00
Syntheses and antibacterial activities of 4 linear nonphenolic diarylheptanoids
Four linear nonphenolic diarylheptanoids were synthesized and their antibacterial activities were studied. (S)-2-Me-CBS-catalysed reduction of alnustone with BH3. SMe 2 gave (R) (-)(4E,6E)-1,7-diphenylhepta-4,6-dien-3-ol, a natural product. Reduction of alnustone with Na in t-BuOH at –15 °C under NH3 atm gave (E)-1,7-diphenylhept-5- en-3-one as a Birch-type reduction product. t-BuOK catalysed condensation of benzalacetone with propionyl chloride gave (4Z,6E)-5-hydroxy-1,7-diphenylhepta-4,6-dien-3-one, a natural product. (1E,4Z,6E)-5-Hydroxy-4-phenethyl1,7-diphenylhepta-1,4,6-trien-3-one, a curcuminoid, was synthesized starting from pentan-2,4-dione in 3 steps.
4/3/2023 11:09:42 PM +00:00
Combined ligand and structure-based virtual screening approaches for identification of novel AChE inhibitors
The excessive activity of acetylcholinesterase enzyme (AChE) causes different neuronal problems, especially dementia and neuronal cell deaths. Food and Drug Administration (FDA) approved drugs donepezil, rivastigmine, tacrine and galantamine are AChE inhibitors and in the treatment of Alzheimer’s disease (AD) these drugs are currently prescribed. However, these inhibitors have various adverse side effects. Therefore, there is a great need for the novel selective AChE inhibitors with fewer adverse side effects for the effective treatment. In this study, combined ligand-based and structure-based virtual screening approaches were used to identify new hit compounds from small molecules library of National Cancer Institute (NCI) containing approximately 265,000 small molecules.
4/3/2023 11:09:31 PM +00:00