Tài liệu miễn phí Hoá học
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Entrapment of organic fluorophores in calcium phosphate nanoparticles with slow release
Two organic fluorophores, fluorescein (F) and rhodamine B (Rd), were entrapped in calcium phosphate nanoparticles. The as-obtained nanoparticles can be used for biological release applications. For this aim, calcium phosphate nanoparticles were synthesized using the precipitation method. Structural analysis of these nanoparticles was performed using XRD, FTIR, and Raman spectroscopy, confirming that the synthesized nanoparticles were hydroxyapatite. TEM and SEM analyses demonstrated that these nanoparticles had a size of 20 nm and a well-defined morphology. F and Rd (about 0.5 wt.%) were entrapped in these nanoparticles and their release, as a function of time, was studied via UV-Vis spectroscopy.
4/3/2023 11:01:23 PM +00:00
Highly improved electrocatalytic oxidation of dimethylamine borane on silver nanoparticles modified polymer composite electrode
Dimethylamine borane (DMAB) is a promising fuel alternative for fuel cell applications. In this work cyclic voltammetric behavior of DMAB was investigated on the polymerized aminophenol film decorated with Ag nanoparticles in alkaline media. The polymer film was formed on the glassy carbon electrode by electrochemical technique and then, the surface was modified with Ag nanoparticles. The surface of the modified electrode was identified by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy techniques.
4/3/2023 11:01:07 PM +00:00
One-pot synthesis of VOx/Al2O3 as efficient catalysts for propane dehydrogenation
Vanadium oxides, as highly efficiently catalysts, are widely applied in various catalytic reactions, such as the dehydrogenation of light alkanes and epoxidation of alkenes. In this paper, a series of VOx/Al2O3 catalysts were fabricated by the 1-pot method for catalytic propane dehydrogenation. The results indicated that the VOx/Al2O3 catalysts with loading of 10 wt.% vanadium exhibited optimized catalytic performance. The as-prepared catalysts were characterized by N2 adsorption-desorption, XRD, TEM, H2 -TPR, and XPS to explore the texture properties, morphology, and electronic environment of vanadium. In addition, several vanadium catalysts were also prepared by the incipient wetness impregnation (IWI) method to compare their catalytic performance with the 1-pot synthesized catalysts.
4/3/2023 11:00:50 PM +00:00
Highly sensitive fluorometric method based on nitrogen-doped carbon dot clusters for tartrazine determination in cookies samples
Nitrogen-doped carbon nanodots (CDs) were prepared via the solvothermal method, using urea and triethylene glycol as the starting materials. The as-prepared CDs had individual diameters of approximately 100 nm and were in clusters of different sizes. The surface composition and optical properties of the as-prepared CDs were characterized. They exhibited multicolor emission properties in the visible range when excited with a wide wavelength range. The aqueous solution of the CDs was used in highly sensitive tartrazine determination. The fluorescence quenching of the CDs was in a linear relationship with the concentrations of tartrazine in the range of 0.5–30.0 µM. The detection limit of the assay was 0.18 µM. Acceptable recovery results were obtained via spike-recovery experiments on cookie samples.
4/3/2023 11:00:37 PM +00:00
Nucleophilic substitution reactions of monofunctional nucleophilic reagents with cyclotriphosphazenes containing 2,2-dioxybiphenyl units
The nucleophilic substitution reactions of mono- and bis-spiro-2,2′ -dioxybiphenyl cyclotriphosphazenes (3 and 4) with cyclopropanemethylamine (5) and aniline (6) were performed in the presence of trimethylamine in THF. Five novel cyclopropanemethylamino- and anilino-substituted spiro-2,2′ -dioxybiphenyl cyclotriphosphazene derivatives (7–11) were obtained from these reactions. The molecular structures of the new cyclotriphosphazene derivatives (7– 11) were characterized by elemental analysis, MALDI-TOF MS, FT-IR, and NMR ( 31P and 1H) spectroscopies. The structure of the spiro-(2,2′ -dioxybiphenyl)-bis-(anilino)-cyclotriphosphazene (11) was also determined by single-crystal X-ray crystallography.
4/3/2023 11:00:21 PM +00:00
Novel BODIPY-bridged cyclotriphosphazenes
Three new 2-component unsubstituted (4P), diiodo- (5P), and dibromo- (6P) distyryl-BODIPY-bridged cyclotriphosphazene dimers were designed and synthesized. The newly synthesized BODIPY-cyclotriphosphazene systems were characterized by 1 H, 13 C, and 31P NMR spectroscopy. The photophysical properties of the distryl-BODIPYs (4–6) and BODIPY-cyclotriphosphazene dyads (4P–6P) were studied by UV-Vis absorption and fluorescence emission spectroscopy. In these derivatives, the bino-type cyclotriphosphazene derivative bearing unsubstituted BODIPY unit 4 P exhibited high fluorescence and no singlet oxygen generation due to the lack of spin converter. The attachment of heavy atoms (iodine and bromine) enabled the production of singlet oxygen.
4/3/2023 11:00:08 PM +00:00
Chemosensor properties of 7-hydroxycoumarin substituted cyclotriphosphazenes
The newly synthesized cyclotriphosphazene cored coumarin chemosensors 5, 6, and 7 were successfully characterized by 1 H NMR, 31P NMR, and MALDI-TOF mass spectrometry. Additionally, the photophysical and metal sensing properties of the targeted compounds were determined by fluorescence spectroscopy in the presence of various metals (Li+, Na+, K+, Cs+, Mg2+, Ca2+, Ba2+, Cr3+, Mn2+, Fe3+, Co2+, Al3+, Hg+, Cu2+, Zn2+, Ag+, and Cd2+). The fluorescence titration results showed that compounds 5, 6, and 7 could be employed as fluorescent chemosensors for Fe3+ ions with high sensitivity. The complex stoichiometry between final cyclotriphosphazene chemosensors and Fe 3+ ions was also determined by Job’s plots.
4/3/2023 10:59:55 PM +00:00
Synthesis, optical, and structural properties of bisphenol-bridged aromatic cyclic phosphazenes
Phenoxy- and naphthoxy-substituted bisphenol-bridged cyclic phosphazenes were synthesized in 2 steps and their thermal, photophysical, and electrochemical properties were investigated. The structures of the cyclic phosphazene compounds were determined by ESI-MS mass spectrometry and 1 H, 13 C, and 31P NMR spectroscopies. The photophysical studies of phenoxy- and naphthoxy-substituted bridged cyclophosphazenes were investigated by means of absorption and fluorescence spectroscopies in different solvents. Thermal and electrochemical properties of the target compounds were also studied. Furthermore, the excimer emissions through intramolecular interactions in solution and in solid state were investigated by fluorescence spectroscopy and the theoretical calculations were performed in detail using DFT.
4/3/2023 10:59:36 PM +00:00
Synthesis of new cyclotriphosphazene derivatives bearing Schiff bases and their thermal and absorbance properties
In this study, a series of cyclotriphosphazene derivatives containing a Schiff base (3a–3d) were synthesized by the reactions of hexachlorocyclotriphosphazene (1) with bis-aryl Schiff bases (2a–2d) having different terminal groups (H, F, Cl, and Br). The products (3a–3d) were characterized by elemental and mass analyses, FT-IR, and 1 H, 13 C, and 31P NMR spectroscopies. Furthermore, the structure of compound 3a was also determined by X-ray crystallography. The thermal behaviors and the spectral properties of the new cyclotriphosphazene compounds (3a–3d) were investigated and the results were compared in the series.
4/3/2023 10:59:26 PM +00:00
Synthesis and spectroscopic properties of (N/O) mono- and dispirocyclotriphosphazene derivatives with benzyl pendant arms: Study of biological activity
The absolute configuration of compound 14 was found as SR in the solid state. Analytical and spectroscopic data of the phosphazenes were consistent with their suggested structures. Antimicrobial activities of the benzyl-pendant-armed cyclotriphosphazenes were scrutinized against G(+) and G(−) bacteria and yeast strains. The bacterium most affected by the synthesized compounds was Pseudomonas aeruginosa. Minimum inhibitory concentrations and minimal bacterial concentrations were in the range of 125–500 µM. Interactions between the phosphazenes (3–12 and 15) and plasmid DNA were studied with agarose gel electrophoresis.
4/3/2023 10:59:15 PM +00:00
Pyrene-BODIPY-substituted novel water-soluble cyclotriphosphazenes: Synthesis, characterization, and photophysical properties
In the present work, pyrene-boron-dipyrromethene (BODIPY)-substituted novel water-soluble cyclotriphosphazene derivatives (6 and 7) were synthesized by click reactions between a cyclotriphosphazene derivative with a hydrophilic glycol side group (2) and BODIPYs (4 and 5). All of the new compounds (2, 6, and 7) were characterized by Fourier-transform infrared and nuclear magnetic resonance spectroscopy, as well as mass spectrometry and elemental analysis. The photophysical properties of the BODIPY-substituted cyclotriphosphazenes (6 and 7) were investigated by UV-Vis and fluorescence emission spectroscopy in water and water/solvent mixtures. It was found that the target compounds were soluble in water and could be potential candidates as water-soluble fluorescent dyes for the desired applications.
4/3/2023 10:58:45 PM +00:00
The role of diazacrown ether in the enhancement of the biological activity of silver nanoparticles
The nanostructuring of hydroxyl-substituted diazacrown-ether (DC) by silver nanoparticles was obtained by green synthesis method in order to increase the antibacterial activity of silver nanoparticles. The synthesized DC, nanoparticles, and nanosupramolecular complex (Ag@DC) were studied by TEM, powder-XRD, and NMR, IR, and UV spectroscopy methods. The Ag@DC nanostructures were uniform and their sizes ranged from 8 to 18 nm. IR and UV spectra revealed the noncovalent formation of the nanosupramolecular complex. The antibacterial activities of the prepared active agents were investigated on gram-positive and gram-negative bacteria by twofold microdilution method.
4/3/2023 10:58:14 PM +00:00
An ultrasensitive electrochemical immunosensor platform based on disposable ITO electrode modified by 3-CPTMS for early detection of parathyroid hormone
Parathyroid hormone (PTH) is a polypeptide containing 84 amino acids secreted by cells of the parathyroid glands. Imbalances of parathyroid levels cause medical problems such as osteoporosis, mental disorders, pancreatitis, kidney stones, cancer, and other symptoms. In this study, we aimed to design an ultrasensitive electrochemical immunosensor for PTH detection. Indium tin oxide (ITO) was used as an electrode for electrochemical impedance spectroscopy (EIS) measurements. ITO sheets were modified by using 3-cyanopropyltrimethoxysilane (3-CPTMS) selfassembled monolayers (SAMs) for immobilizing the anti-PTH antibody via covalent interactions.
4/3/2023 10:58:06 PM +00:00
Surface modification of polyvinyl chloride by polyacrylic acid graft as a polyelectrolyte membrane using Ar plasma
This work reports the synthesis and properties of a new membrane based on polyvinyl chloride (PVC) grafting with polyacrylic acid (PAA) using argon (Ar) plasma. The membranes of PVC were synthesized by solutioncasting method, where PAA was deposited as an ultrathin film onto PVC using dielectric barrier discharge at atmospheric pressure with Ar gas. The surface characteristics and chemical composition of the modified membranes were analyzed by water contact angle, scanning electron microscopy, and Fourier transform infrared spectroscopy. Moreover, the electrochemical properties of the membrane were investigated via ion exchange capacity for the purpose of using it as a polyelectrolyte membrane.
4/3/2023 10:57:54 PM +00:00
Aqueous two-phase extraction technique based on magnetic ionic liquid-nonionic surfactant for phenolic acids in grape, apple, pear, and banana
An aqueous two-phase extraction system was constituted using magnetic ionic liquid-nonionic surfactant for phenolic acids and the developed method was applied to apple, grape, pear, and banana samples. Ionic liquids based on imidazolium containing butyl, allyl, and benzyl groups were used for extraction. The parameters influencing the extraction efficiency such as volume of ionic liquids, type and amount of surfactant and salt, ultrasound extraction time, temperature, and sample pH were optimized. The extraction efficiencies of ionic liquids were compared for phenolic acids under optimized conditions.
4/3/2023 10:57:46 PM +00:00
Synthesis and characterization of unsaturated diacyl and alkyl-acyl piperazine derivatives
The aim of this study is to obtain new unsaturated piperazine compounds by the reactions of piperazine (1a) and piperazine derivatives (1b–1d) with acylation reactive groups (2a–2j). Methacryloyl piperazine (1b) was synthesized from the reaction of methacrylic anhydride with piperazine (1a). Acyl chlorides (2b–2d) were prepared from the reaction of thionyl chloride with carboxylic acids (3a–3c) obtained as a result of the reaction with malonic acid and suitable aldehyde (5-methylfuran-2-carbaldehyde for 3a, cinnamaldehyde for 3b, and thiophene-2-carbaldehyde for 3c), respectively, by literature methods. Acyl chlorides 2e and 2f were obtained from the reaction of commercially purchased carboxylic acids 3d and 3e with thionyl chloride.
4/3/2023 10:57:37 PM +00:00
Synthesis, characterization, and investigation of singlet oxygen, DNA interaction, and topoisomerase I inhibition properties of novel zinc(II) phthalocyanine
In this work, phthalonitrile (3) and zinc(II) phthalocyanine (4) were prepared. To determine the photodynamic therapy potential of compound 4, singlet oxygen quantum yield, DNA binding and cleavage, and topoisomerase I inhibition experiments were performed. The singlet oxygen quantum yield value of compound 4 was found higher than that of the standard unsubstituted zinc(II) phthalocyanine compound (Std-ZnPc). The binding experiments showed that compound 4 interacted with ct-DNA strongly via nonintercalation mode. pBR322 plasmid DNA cleavage activity of the compound was investigated using agarose gel electrophoresis.
4/3/2023 10:57:23 PM +00:00
Dispersive liquid-liquid microextraction of parabens from pharmaceuticals and personal care products prior to their determination using HPLC-DAD
Dispersive liquid–liquid microextraction followed by a back-extraction step was combined with HPLC-DAD for the determination of four parabens (i.e. methyl-, ethyl-, propyl-, and butylparaben). Optimum extraction conditions were found as follows: 225 µL of chloroform, 0.75 mL of ethanol, 7.5 mL of aqueous solution and within an extraction time of 15 s. Back-extraction into 100 µL of 50 mM sodium hydroxide solution within 20 s resulted in a reversed-phase HPLC-compatible extract. The analytes were separated at 20◦C using methanol (A) and water (B), 40:60 (A:B, v/v) as the mobile phase, a flow rate of 1.0 mL min −1 and an injection volume of 20 µL. DAD was set at 258 nm to monitor the analytes.
4/3/2023 10:57:12 PM +00:00
Synthesis and catalytic activity of ionic palladium N-heterocyclic carbene complexes
The synthesis of 3 benzimidazole-based ionic Pd(II)-NHC complexes (NHC:N -heterocyclic carbene) is presented. The structures of the complexes are as follows: [NHC-PdBr3]−[NHC]+. The ionic palladium(II)-NHC complexes were synthesized in high yields and were fully characterized by nuclear magnetic resonance spectroscopy, X-ray diffraction, LC-MS/MS, and elemental analysis. These complexes have been identified as active catalysts in Suzuki–Miyaura reactions in a solution of 2-propanol and water at room temperature for different aryl bromides.
4/3/2023 10:57:04 PM +00:00
Synthesis of Hofmann-type Zn(H2O)2Ni(CN)4.nG (G = water and 1,4-dioxane) clathrates and the determination of their structural properties by various spectroscopic methods
Thes tructures of the crystalline compounds were characterized via their spectral analyses. General information about the structures of the newly obtained Hofmann-type clathrates was obtained from their vibration spectra by considering significant changes in the vibration peaks of the cyanide group, water ligand molecule, and guest molecules (water and 1,4-dioxane). The thermal behavior of the Hofmann-type clathrates was investigated in the range of 25–500°C. In addition, experimental data on the magnetic properties of the Hofmann-type clathrates were obtained using the Gouy method under normal conditions.
4/3/2023 10:56:48 PM +00:00
Step-by-step optimization of the HILIC method for simultaneous determination of abacavir, lamivudine, and zidovudine from dosage form
Combined therapy for HIV treatment shows superior efficacy in comparison to single therapy. Furthermore, the separation and determination of the combined dosage forms hold a significant place in the pharmaceutical industry. Not only reverse phase high-performance liquid chromatography (HPLC) but also hydrophilic interaction liquid chromatography (HILIC) can be used for these purposes. Contrary to conventional RP systems, HILIC may be an alternative for the analysis of polar substances. The aim of this study was the step-by-step development of a simple, rapid, and reliable method for the simultaneous determination of antiviral compounds from their marketed formulation (Trizivir).
4/3/2023 10:56:39 PM +00:00
One-pot synthesis of quinazolin-4(3H )-ones and 2,3-dihydroquinazolin-4(1H )-ones utilizing N -(2-aminobenzoyl)benzotriazoles
A convenient and efficient method has emerged for the one-pot synthesis of substituted quinazolin-4(3H)- ones and nonaromatic alkaloids. 2-Substituted quinazolin-4(3H)-ones, 2,3-disubstituted quinazolin-4(3H)-ones, and 2,3-dihydroquinazolin-4(1H)-ones were obtained at yields of 46% to 95% by a one-pot reaction of N -(2-aminobenzoyl) benzotriazoles with amines and orthoesters or aldehydes under catalyst-free conditions.
4/3/2023 10:56:30 PM +00:00
Stability improvement by crosslinking of previously immobilized glucose oxidase on carbon nanotube-based bioanode
Bioanode stability with glucose oxidase was enhanced significantly by covalent crosslinking without substantial enzymatic activity and affinity loss. Initially, glucose oxidase was immobilized by aldehyde groups on the electrode that was developed using ferrocenecarboxaldehyde, polyethyleneimine, multiwall carbon nanotubes, and carbon cloth for biofuel cell applications. The glucose oxidase half-life was extended by more than 4 times, from 27.2 to 124.7 h, after the electrode was crosslinked. Enzymatic kinetic parameters were determined for the crosslinked enzyme and they were compared to the noncrosslinked immobilized enzyme parameters on the electrode.
4/3/2023 10:56:19 PM +00:00
Design, synthesis, and antitumor evaluation of novel methylene moiety-tethered tetrahydroquinoline derivatives
Novel methylene-tethered tetrahydroquinolines (THQs) and cyclopenta[b]pyridines were synthesized by onepot multicomponent reactions of Mannich bases, enolizable ketones, and NH4 OAc in water by an environmentally friendly K-10 montmorillonite clay-catalyzed reaction. The cytotoxic activities of 1-(2-methyl-8-methylene-5,6,7,8- tetrahydroquinolin-3-yl)ethanone (9a), ethyl 2-methyl-8-methylene-5,6,7,8-tetrahydroquinoline-3 carboxylate (9b), and 1-(2-methyl-7-methylene-6,7-dihydro-5H -cyclopenta[ b ]pyridin-3-yl)ethanone (11a) were tested against rat glioblastoma (C6), human breast cancer (MCF-7), prostate cancer (PC3), neuroblastoma (SH-SY5Y), and mouse fibroblast (L929) cell lines in a concentration-dependent (50–300 µM) and time-dependent (24–72 h) manner and expressed as IC50 values.
4/3/2023 10:56:11 PM +00:00
Evaluation of the enrichment and amplification effect of pentachlorobenzene with lower bioconcentration in the food chain before and after modification
In this paper, in order to construct a 3D quantitative structure–activity relationship (QSAR) model with the chlorobenzene (CB) molecular structure parameter as an independent variable and the octanol-water partition coefficient (KOW ) as a dependent variable, 9 kinds of CB molecules were used as training sets and 3 kinds of CB molecules were used as test sets. We adopted the QSAR module in the Sybyl-X2.0 software from the Tripos Corporation (USA). The molecular modification of the pentachlorobenzene molecule with low bioconcentration was carried out by combining a three-dimensional contour map and fractional factorial design.
4/3/2023 10:55:57 PM +00:00
Investigation of the effects of some water-soluble vitamins on glutathione reductase enzyme purified from bovine liver
Glutathione reductase (GR, EC 1.8.1.7) is an antioxidant enzyme and is involved in the reducing reaction of oxidized glutathione. Glutathione and reduced glutathione are very crucial for micro- and macroorganisms because of their barrier function against radicals. Therefore, the aim of this article was to purify GR and evaluate the relationship between purified GR and vitamins. GR was purified from bovine liver using 2’,5’-ADP Sepharose 4B column materials. To check the purity of each subunit of the enzyme, SDS-PAGE electrophoresis was performed and each one was 55 kDa. Afterwards, specific activity and purified ratio for the enzyme were calculated as 54 EU/mg × protein and 2700 times, respectively.
4/3/2023 10:55:49 PM +00:00
The solvatochromism and electronic structure of (E)-2-(2-hydroxystyryl)quinolin-8-ol
The (E)-2-(2-hydroxystyryl)quinolin-8-ol (abbreviated as HSQ) molecule was synthesized and characterized. The ESIPT, solvatochromism properties, electronic structure, and ground and excited electric dipole moments of this molecule were measured using absorption and fluorescence spectra recorded in 13 different solvents. Its electronic structure via electronic transitions was investigated to find the quantitative values of solvatochromism properties by LSER calculations. The ESIPT mechanism was clarified; ground and excited dipole moments were determined using solvatochromic shift methods.
4/3/2023 10:55:25 PM +00:00
Glucose oxidase immobilized biofuel cell flow channel geometry analysis by CFD simulations
Glucose oxidase was covalently immobilized to a porous electrode, which was developed by using ferrocene functionalized polyethyleneimine, multiwall carbon nanotubes, and carbon cloth for biofuel cell applications in our recent studies. The kinetics parameters (i.e. kM, Vmax) and other parameters required for the modeling study were determined experimentally. Fuel cell flow channel geometry was analyzed by a computational fluid dynamics modeling approach. Substrate flow rate and mass transfer for each proposed channel type were considered in the simulations.
4/3/2023 10:54:49 PM +00:00
Synthesis and characterization of novel mussel-inspired benzoxazines by thiol-benzoxazine chemistry
A catechol-based benzoxazine copolymer is reported via a new approach using an oxazine-thiol reaction. The main chain benzoxazine precursor was obtained via the classic benzoxazine synthesis methodology using the raw chemicals catechol, formaldehyde, and 4,7,10-trioxa-1,13-tridecanediamine. The countercomponent was synthesized from poly(ethylene glycol) methyl ether via the Fischer esterification reaction. The obtained reactive catechol-based benzoxazine was then reacted in mild conditions with polymeric thiol precursor to obtain a copolymer structure. The precursors and the resulting structure were characterized by thermal and spectral analyses using DSC, TGA, FT-IR, 1H NMR, and GPC.
4/3/2023 10:54:40 PM +00:00
Modeling and optimizing microwave-assisted extraction of antioxidant compounds from marigold (Calendula officinalis L.) using response surface methodology
Calendula officinalis L. is a commercially important plant that finds application in the treatment of various diseases in traditional medicine. The total antioxidant capacity, radical scavenging activity, and total phenolic content of marigold extracts were investigated by Folin, CUPRAC, and DPPH assays, respectively. The optimum operating conditions of microwave-assisted extraction (MAE) including temperature, extraction time, solvent-to-solid ratio, and solvent concentration were ascertained by employing response surface methodology (RSM). The solvent (ethanol) concentration was the most significant operating factor among all responses of MAE.
4/3/2023 10:54:32 PM +00:00