Tài liệu miễn phí Hoá học
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An efficient protocol for the synthesis of brominated norbornene, norbornadiene, and benzonorbornadiene
An efficient protocol for the synthesis of 2-bromonorbornene, 2-bromonorbornadiene, 2-bromoben- zonorbornadiene, 2,3-dibromonorbornene, 2,3-dibromonorbornadiene, and 2,3-dibromobenzonorbornadiene in good yields has been developed. 1,2-Dibromotetrachloroethane is used as the brominating agent for these reactions. The results are discussed in comparison with alternative methods in the literature.
4/3/2023 10:34:56 PM +00:00
Gold-assembled silica-coated cobalt nanoparticles as efficient magnetic separation units and surface-enhanced Raman scattering substrate
Magnetic and optical bifunctional nanoparticles that combine easy separation, preconcentration, and efficient SERS capabilities have been fabricated with high sensitivity and reproducibility through a low-cost method. These gold nanoparticles attached on magnetic silica-coated cobalt nanospheres (Co@SiO2 /AuNPs) display the advantage of strong resonance absorption due to gaps at nanoscale between neighboring metal nanoparticles bringing large field enhancements, known as “hot spots”. The prepared particles can be controlled by using an external magnetic field, which makes them very promising candidates in biological applications and Raman spectroscopic analysis of dissolved organic species.
4/3/2023 10:34:38 PM +00:00
3D-QSAR/HQSAR-based analysis of bioconcentration and molecular modification of monophenyl aromatic compounds
Comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA) of three-dimensional quantitative structure–activity relationship (3D-QSAR) models were conducted using 36 aromatic compound congeners as the training set and eight aromatic compound congeners as the test set. Logarithms of experimental bioconcentration data (logBCF) were used as dependent variables and the physicochemical properties of the aromatic compound congeners were used as independent variables. Furthermore, the molecular holographic quantitative structure–activity relationship (HQSAR) model constructed by the HQSAR module in Sybyl software was used to establish a method to find molecular activity substitution sites of bioconcentration potential by coupling the molecule activity contribution map of HQSAR with the electrostatic contour map of CoMSIA.
4/3/2023 10:34:20 PM +00:00
Synthesis of novel azo linkage-based Schiff bases including anthranilic acid and hexanoic acid moieties: Investigation of azo-hydrazone and phenol-keto tautomerism, solvatochromism, and ionochromism
Two new azo-Schiff base receptors (L1 and L2) containing azo and azomethine groups with a conjugated group (benzyl ring of anthranilic acid, in L1) and electron-donating group (alkyl chain of hexanoic acid, in L2) were synthesized and characterized. Azo-hydrazone/phenol-keto tautomerism and solvatochromism were investigated. Studying their sensing ability towards cations (Co2+, Cu2+, Zn2+, Ni2+, Pb2+, Cd2+, Mn2+, Fe3+, Cr3+, and Al3+), high sensitivity and selectivity were recorded for Fe3+ by naked eye and UV-Vis spectra in DMF-aqueous HEPES buffer (v:v, 1:1, pH 6.8). The color of L1 and L2 solutions instantly changed from yellow to deep orange and pale orange. L2 sensed Cu2+ and Al3+ ions selectively by UV-Vis spectra.
4/3/2023 10:33:51 PM +00:00
Investigation of the structural and physicochemical requirements of quinoline-arylamidine hybrids for the growth inhibition of K562 and Raji leukemia cells
Quantitative structure–activity relationship (QSAR) analysis of 28 quinoline-arylamidine (CQArA) hybrids against two leukemia cells, K562 and Raji, was performed. Multiple linear regression (MLR) models were obtained by genetic algorithm. The best models involved the following descriptors: radial distribution function (RDF) descriptors, GETAWAY (GEometry, Topology, and Atom-Weights AssemblY) descriptor, bond information content index, and dipole moment. The best MLR models for K562 and Raji cells demonstrated satisfactory stability in internal and external validation. Since the QSAR model for Raji cells has better predictive ability, two new highly potent CQArA analogues were proposed based on it.
4/3/2023 10:33:38 PM +00:00
Rapid and on-site electrochemical detection of bisphenol A and arsenic in drinking water using a novel electrode array
The paper describes a novel dip-and-gauge hand-held sensor device for the rapid, cost-effective, and on-site detection of bisphenol A and arsenic in drinking water samples. Different working electrode diameters ranging from 1.5 mm to 4 mm were designed and fabricated to construct a new electrochemical biosensor. The sensor was employed for the chronoamperometric detection of bisphenol A and voltammetric determination of arsenic in drinking water samples. Bisphenol A measurements resulted in a detection limit of 10 ng mL−1 with a linear range of 0–4000 ng mL−1. Baby products and bottles have to be completely free of bisphenol and hence a liquid-phase microextraction method has been developed to reduce the detection limit further to 0.6 ng mL−1.
4/3/2023 10:33:26 PM +00:00
Characterization and purification of 1,2,4-triazole-containing phthalocyanines synthesized by microwave method and structure elucidation by spectroscopic techniques
The complexes of peripherally tetra-substituted metal-free (8), lead(II) (9), and zinc(II) (10) phthalocyanine derivatives were synthesized for the first time in this work. The structures of these new complex compounds have been elucidated using many spectral methods such as electronic absorption, FT-IR, 1H NMR, 13C NMR, elemental analysis, and mass spectra. The thermogravimetric behavior of compounds 8–10 was determined by thermogravimetric analysis method in addition to these spectral methods.
4/3/2023 10:33:14 PM +00:00
In situ preparation of hydroxyapatite composites into hydrolyzed polyacrylamide solution and methylene blue dye retention
Four composites of hydroxyapatite/hydrolyzed polyacrylamide (HAP/HPAM-n) were prepared using an in situ wet chemical method. The synthesis was performed by preparing a suspension of calcium in a copolymer solution having a known HPAM concentration. Phosphoric acid was added dropwise to each suspension to obtain HAP/HPAM-n composites. The effect of initial copolymer amount on the composite properties was investigated using XRD, FTIR, TGA, and SEM/EDS analysis. The obtained results were compared to the HAP sample synthesized under the same conditions and without copolymer.
4/3/2023 10:33:05 PM +00:00
New diazo-containing phenolic oximes: structural characterization, computational studies, and solvent extraction of Cu(II), Ni(II), and Zn(II) ions
In the current study, four new phenolic oxime ligands (HL1ox–HL4ox) containing diazo groups (-N=N-) were synthesized and used for liquid-liquid extraction of heavy metal ions [Cu(II), Ni(II), and Zn(II)]. The new compounds were characterized by analytical and spectroscopic methods. Solid-state structures of HL1ox–HL3ox were determined by single-crystal X-ray diffraction studies. Hirshfeld surface analysis of the compounds was performed to determine the contribution of different intermolecular contacts to the stability of the structures. The HL1ox–HL4ox ligands showed higher extraction performance for Cu(II) ion than Ni(II) and Zn(II) ions.
4/3/2023 10:32:57 PM +00:00
Crystal structure and Hirshfeld surface analysis of 1,2-ethylene-bis (para-methyl pyridinium) dichromate as a new selective and mild agent in oxidation of alcohols
1,2-Ethylene-bis(para-methyl pyridinium) dichromate, (C14H18N2)[Cr2O7], is used as a new oxidizing agent in conversion of some alcohols to their corresponding carbonyl compounds in CH3 CN solvent and also under solvent-free conditions. In both procedures, high conversion percentages are observed. However, a much shorter reaction time is achieved in solvent-free conditions. For allylic alcohols, the C=C bond is not oxidized and the examined saturated alcohol in this work (i.e. cyclo-hexanol) remains intact, which illustrates the mild nature of reagent used.
4/3/2023 10:32:44 PM +00:00
Plasma O2 modifies the structure of synthetic zeolite-A to improve the removal of cadmium ions from aqueous solutions
The present study addresses the removal of cadmium ions (Cd(II)) from aqueous solutions at a pH of 7.5 using zeolite-A activated by exposure to oxygen plasma. The activation process was performed over a wide range of plasma powers (10, 20, 30, and 40 W) and exposure times (30 to 360 s). Oxygen plasma cannot chemically modify zeolite to a considerable extent, but it can clean the surface, open blocked pores, and induce the formation of additional OH groups via exposure to humidity in ambient air. Therefore, Cd+2 ion removal is increased by approximately 10% with the plasma treatments.
4/3/2023 10:32:31 PM +00:00
Efficient synthesis and antifungal investigation of nucleosides’ quaternary ammonium salt derivatives
Quaternary ammonium salts are a group of compounds with diverse biological properties, the most important of which are their antiviral, antibacterial, and antifungal activities. The quaternization reactions of 5'-O-tosyl derivatives of uridine and thymidine with triethylamine, trimethylamine, 4-(N ,N -dimethylamino)pyridine, 2-methylpyridine, and pyridine are described in this article. Two of the synthesized compounds are exceptional because they are first of this type that demonstrate concentration-dependent antifungal in vitro activity against two species of the genus Candida in minimal YNB-SG medium.
4/3/2023 10:32:18 PM +00:00
1,2-Dibromotetrachloroethane: An efficient reagent for many transformations by modified Appel reaction
An efficient and facile method has been developed for the synthesis of alkyl bromides from various alcohols under mild conditions using a triphenylphosphine (PPh3)/1,2-dibromotetrachloroethane (DBTCE) complex in excellent yields and very short time (5 min). This method can also be applied for the transformation of chiral alcohols to their corresponding bromides in very high enantiomeric excess. The PPh3 /DBTCE complex is also successfully applied to ring-opening reactions of cyclic ethers in mild conditions. Esterification, amidation, and formation of acid anhydrides under very mild experimental conditions are also successfully accomplished by following a modification of the Appel reaction protocol in this work.
4/3/2023 10:32:12 PM +00:00
Effect of polyvinyl alcohol/chitosan blend ratios on morphological, optical, and thermal properties of electrospun nanofibers
In this study, the electrospinning method was used to prepare polyvinyl alcohol (PVA)/chitosan (CS) blend nanofibers from their solutions. The effect of blend ratios (PVA/CS: 1%, 3%, 5%, and 7% (w/w)), applied voltage, and flow rate on the morphological, optical, and thermal properties of electrospun nanofibers were investigated by scanning electron microscopy (SEM), fluorescence and UV-Vis spectroscopies, and thermogravimetric analysis (TGA), respectively. Fourier transform infrared spectroscopy analysis indicated the existence of related functional groups of both PVA and CS in the electrospun fibers.
4/3/2023 10:31:45 PM +00:00
Novel “turn off-on” sensors for detection of DNA-acrylamide interaction using ZnS quantum dots as a phosphorescent probe
A novel “turn off-on” sensor for detection of interaction between DNA and acrylamide (ACR) was developed. In this method, L-cysteine capped Mn-doped ZnS quantum dots (QDs) were used as room temperature phosphorescent probes. In the “turn-off” mode, ACR was absorbed onto the surface of QDs via electrostatic interaction, which caused a quenching effect of room-temperature phosphorescence signal by photoinduced electron-transfer mechanism. ACR was removed from the QDs’ surface with the addition of DNA. Thus, the phosphorescence emission of QDs was recovered and the system was turned to the “turn-on” mode.
4/3/2023 10:31:37 PM +00:00
Naphthoxazoles and heterobenzoxazoles: Cholinesterase inhibition and antioxidant activity
Finding novel cholinesterase inhibitors that would be able to cross the blood–brain barrier, have favorable pharmacokinetic parameters, and reduce hepatotoxicity along with other side effects has been the main focus of investigations dealing with Alzheimer disease. In this study we evaluated cholinesterase inhibitory and antioxidant activity of seven oxazole derivatives. These compounds have been efficiently and sustainably prepared by photochemical electrocyclization reaction. Various naphthoxazoles have been previously investigated as potential antibacterial, antituberculosis, and anticancer agents.
4/3/2023 10:31:30 PM +00:00
Synthesis, characterization, and kinetic studies of multifunctionalized mesoporous silica for adsorption of zinc
The aim of this study is to evaluate the utilization of bifunctional mesoporous silica with a platinum and propylsulfonic acid group (Pt/SBA15-PrSO3H) as an adsorbent for the removal of Zn(II) ions from aqueous solutions. The SBA15-functionalized organosulfonic acid material was synthesized with a one-step cocondensation synthesis route. The second step was Pt loading during reduction and deposition into the aqueous suspension of the bifunctional mesoporous silica synthesized by an aqueous solution of formaldehyde as the reducing agent. The propylsulfonic acid and platinum functionalized mesoporous silica were characterized by BET, thermogravimetric analysis, and X-ray diffraction methods.
4/3/2023 10:31:18 PM +00:00
Preparation and physicochemical characterization of zinc oxide/sodium cellulose composite for food packaging
Zinc oxide/sodium cellulose composite with different ZnO loadings was prepared for the first time. The crystal structures of cellulose, sodium cellulose, and ZnO/sodium cellulose composite were characterized by FT-IR, XRD, XPS, SEM, and EDX. ZnO/sodium cellulose showed a similar XRD pattern to that of cellulose II. The XPS spectrum emphasized the presence of Zn2+ and Na+ ions in the prepared composite. Additionally, the SEM analysis showed the growth of ZnO crystals on the sodium cellulose surface. UV-Vis spectrometry of the ZnO/sodium cellulose spectrum showed a distinguished absorption band at 360 nm that was attributed to the presence of ZnO particles on the cellulosic fibers.
4/3/2023 10:31:05 PM +00:00
Comparative study of solvent extraction of molybdenum by various extractants
Solvent extraction of molybdenum from various acid media by Alamine 336, Aliquat 336, TOPO, and DEHPA in kerosene was studied. The extraction efficiency of molybdenum by diisobutyl ketone (DIBK), the effects of various parameters like diluents, mineral acids, extractant concentration, and applications of these extractants on molybdenum extraction contained in the uranium-bearing ore solutions were investigated. DIBK used as solvent can indeed extract the molybdenum without adding any extractants in the range of 20–50 mg/L. Molybdenum was extracted by Aliquat 336 in all mineral acids at more than 90%.
4/3/2023 10:30:58 PM +00:00
Electrodeposition of tin(II) from citrate complexes
This paper provides the calculation of the distribution of the concentrations of complex particles of the Sn(II) - citrate - water system in the solution volume, on the surface of the electrode, and in the diffusion layer for the tin citrate electrolyte containing an excess of the ligand. Based on the calculations for the electrodeposition of tin, an electrolyte containing [SnCit]2− complex at pH 8.0 was chosen. The kinetic parameters of the discharge stage, the diffusion coefficient of the electrochemical active ion, and the current efficiency of tin were determined by the methods of stationary voltammetry and chronovoltamperometry.
4/3/2023 10:30:47 PM +00:00
Synthesis of highly active crystalline carbon nitride prepared in various salt melts for photocatalytic degradation of phenol
Crystallinity could have a decisive influence on photocatalytic performance. In this study, the synthesis of crystalline carbon nitride (CN) was studied via an ionic melt polycondensation of urea precursor in the presence of various salt melts, which were KCl-LiCl, KCl-NaCl, and KCl-ZnCl2. While all the salt melts helped to improve the optical properties of the CN, only KCl-LiCl salt melt could form crystalline CN as evidenced by its X-ray diffraction pattern. Furthermore, the specific surface area of CN (72 m2/g) was maintained when using KCl-LiCl (73 m2/g), but it was decreased in the presence of KCl-NaCl (22 m2/g) or KCl-ZnCl2 (17 m2/g).
4/3/2023 10:30:36 PM +00:00
An evaluation of the adsorption dynamics of phosphate ions onto Fe(II)-montmorillonites
Fe(II)-montmorillonites (Fe(II)-MMTs) were prepared by mixing solutions of Fe(II) and montmorillonite at pH 3.5. Two different Fe(II)-MMTs were prepared and the ferrous iron contents were 40 mg/L and 80 mg/L. All samples were characterized by XRD, FT-IR, TGA, DSC, and nitrogen adsorption. By nitrogen adsorption, the pore size can be obtained in the pore diameter curve with average pore widths of 6.67 nm, 9.96 nm, and 17.07 nm, respectively. The removal rate of phosphate increased rapidly during the first 40 min, in which Fe(II)-MMT (1) and Fe(II)-MMT (2) were stronger adsorption systems than MMT.
4/3/2023 10:30:19 PM +00:00
The protective effect of N-acetylcysteine amide against paraquat-induced neurotoxicity
N-acetylcysteine amide (NACA) is a new antioxidant molecule with powerful radical scavenging properties. The aim of this study was to investigate neuroprotective effects of NACA against paraquat (PQ) toxicity in the midbrains of rats by using motor coordination tests and biochemical and histological analysis. Thirty adult Wistar albino rats were divided into three groups: Group 1: control (n = 10), Group 2: PQ (10 mg/kg) (n = 10), and Group 3: PQ (10 mg/kg) + NACA (100 mg/kg) (n = 10). NACA was administrated intraperitoneally 30 min before PQ injection. Performance was measured for a period of 28 days. The rotarod and accelerod tests were performed prior to and after the experimental period.
4/3/2023 10:30:11 PM +00:00
Catalytic hydrogenation of furfural and furfuryl alcohol to fuel additives and value-added chemicals
The selective hydrogenation of furfural and furfuryl alcohol at different temperatures has been studied using several catalysts. The effect of various reaction conditions (pressure, catalyst amount, and solvent) was studied. We have shown that Pd/TiO2 catalysts can be very effective for the synthesis of 2-methylfuran at room temperature. Using octane as a solvent, the solvent effectiveness was investigated and showed actively high selectivity towards 2-methylfuran and furfuryl alcohol, but there were many byproducts that were still noticed.
4/3/2023 10:30:04 PM +00:00
An insight into the therapeutic potential of piperazine-based anticancer agents
The piperazine ring system is among the medicinally important nitrogen-containing heterocyclic ring systems and is exploited for the synthesis of various drug molecules. A number of FDA-approved anticancer drugs contain piperazine rings and thus it is considered as an attractive scaffold having extraordinary potential for the development of new anticancer agents. In recent decades there has been an alarming increase in the number of people suffering from cancerous diseases all over the world, which resulted in an extraordinary increase in research reports on new anticancer drug candidates.
4/3/2023 10:29:52 PM +00:00
Experimental and theoretical study of NH3 adsorption and desorption over a Cu-chabazite NH3-SCR catalyst
NH3 adsorption and desorption behavior of a commercial Cu-chabazite (CHA) NH3 selective catalytic reduction (NH3 -SCR) catalyst was studied in the presence and absence of H2O. NH3 uptake values at various adsorption temperatures were obtained during various steps of the adsorption and temperature-programmed desorption (TPD) experiments. Total NH3 uptake decreased from 4.6 to 1.6 g NH3/L catalyst when the adsorption temperature was increased from 50 to 300◦C. Three major adsorption sites for NH3 adsorption could be identified and quantified using TPD experiments, namely loosely, moderately, and strongly bound NH3 with peak centers at around 147, 266, and 447◦C.
4/3/2023 10:29:43 PM +00:00
Determination of hydrogen peroxide with an enzymeless amperometric sensor based on poly(vinylferrocene)-supported Ag nanoparticles
An enzymeless electrochemical sensor for detection of low amounts of H2O2 with the aid of Ag nanoparticles supported on conducting poly(vinylferrocene) (PVF) film was developed. Experimental results revealed that contribution of Ag nanoparticles led to remarkable improvement by means of reduction potential and reduction current. Influence of experimental parameters (i.e. polymeric film thickness, concentration of Ag precursor, immersion time in precursor solution, reduction time, and reduction potential) were investigated. The Ag/PVF-modified electrode system was characterized physically by scanning electron microscopy.
4/3/2023 10:29:33 PM +00:00
Preparation of self-propelled Cu-Pt micromotors and their application in miRNA monitoring
Self-propelled catalytic micromotors offer considerable promise in terms of many applications. Catalytic micromotors are strongly influenced by the presence and concentration of specific ions and chemicals in the environment, making them useful as sensors and actuators. In this work, copper (Cu)-platinum (Pt) micromotors were fabricated by using the magnetron sputtering method for the first time in the literature and their applications based on the detection of miRNA-21 were evaluated. We analyzed the dependence of the mobility of Cu-Pt micromotors using different concentrations of hydrogen peroxide (H2O2).
4/3/2023 10:29:21 PM +00:00
Voltammetric determination of glycopyrrolate in a pharmaceutical formulation
The electrochemical activity of glycopyrrolate was studied. Different voltammetric techniques were applied in this study, including cyclic voltammetry (CV), differential pulse voltammetry (DPV), and linear sweep voltammetry (LSV). Glassy carbon and platinum working electrodes were utilized. CV indicated that glycopyrrolate has a reversible redox reaction on the working electrode surface, with an anodic peak current at approximately 1.05 V and a cathodic peak at 0.80 V. Several parameters that affect the sensitivity of these methods were optimized for the quantitation of glycopyrrolate.
4/3/2023 10:29:10 PM +00:00
Optimization of sugarcane bagasse activation to achieve adsorbent with high affinity towards phenol
Sugarcane bagasse as an agricultural/industrial biomass was converted into a low-cost activated carbon via an acid activation procedure under optimized conditions. Phosphoric acid was applied as a cost-effective and environmentally friendly chemical activator. The optimized activated carbon produced under temperature of 550°C and impregnation ratio of 1.5 showed a micromesoporous structure with specific surface area and pore volume of 972.5 m2/g and 0.43 cm3/g, respectively.
4/3/2023 10:29:00 PM +00:00