Tài liệu miễn phí Hoá học
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Application of inverse gas chromatography in the surface characterization of diethanol amine modified polystyrene based polymer
In the present work, diethanol amine modified polystyrene based polymer (PVBC-Diethanol amine) was synthesized and characterized, then surface properties of the polymer were examined by inverse gas chromatography method at infinite dilution. The retention diagrams obtained based on the interaction of polar and nonpolar probes with the polymer were drawn over a temperature range from 30 to 55 °C. Through the diagrams, the dispersive component of the surface free energy, gS D of the polymer surface, and the specific enthalpy of adsorption, DHA S , of probes on the polymer were also calculated. Lewis acid, KA, and Lewis base, KD , parameters of PVBC-Diethanol amine surface were determined. The values of KA and KD indicated that PVBC-Diethanol amine surface exhibited a basic behavior.
4/3/2023 11:50:41 PM +00:00
Preparation of G-CuO NPs and G-ZnO NPs with mallow leaves, investigation of their antibacterial behavior and synthesis of bis(indolyl)methane compounds under solventfree microwave assisted dry milling conditions using G-CuO NPs as a catalyst
In this study, biogenic copper and zinc oxide nanoparticles (G-ZnONPs and G-CuONPs) were synthesized by the green synthesis method using Malva parviflora L. (Millow) leaf extract and the obtained nanoparticles were characterized in detail with UVVis, FTIR, SEM, XRD. The antibacterial properties of the synthesized nanoparticles on gram-positive and gram-negative bacteria were investigated and it was found that the nanoparticles had high antimicrobial activity in the results of the experiments. With the obtained G-CuONPs, the synthesis of bis(indolyl)methanes with the “green” one-pot synthesis using microwave was achieved quickly and with high efficiency, and the thermal behavior of the obtained products was investigated.
4/3/2023 11:50:30 PM +00:00
A survey on surface morphology control of cross-linked poly(N-vinylpyrrolidone) polymer particle via inverse suspension polymerization
This study mainly centers on the preparation and characterization of the cross-linked poly(NVP) microspheres by means of inverse suspension polymerization technique. The effect of the cross-linker content, the volumetric ratio of dispersed phase to suspension phase (DP/CP), agitation rate, and the reaction temperature on the characteristics of the microparticles were investigated meticulously using SEM, and the optimum preparation conditions were determined. The findings revealed that the morphological and surface properties of the obtained particles could be controlled easily by changing these parameters. Accordingly, the microparticles having the perfect spherical with smooth surface and good roundness, dumbbell-shaped, snowman besides dented, sunked and macelike appearance were obtained.
4/3/2023 11:50:16 PM +00:00
Surface and chemical characteristics of platinum modified activated carbon electrodes and their electrochemical performance
: Platinum (Pt) loaded activated carbons (ACs) were synthesized by the thermal decomposition of platinum (II) acetylacetonate (Pt(acac)2 ) over chemically activated glucose-based biochar. The effect of Pt loading on surface area, pore characteristics, surface chemistry, chemical structure, and surface morphology were determined by various techniques. XPS studies proved the presence of metallic Pt0 on the AC surface. The graphitization degree of Pt loaded ACs were increased with the loaded Pt0 amount. The electrochemical performance of the Pt-loaded ACs (Pt@AC) was determined not only by the conventional three-electrode system but also by packaged supercapacitors in CR2032 casings.
4/3/2023 11:50:06 PM +00:00
Sn(II)/PN@AC catalysts: Synthesis, physical-chemical characterization, and applications
In this study, the novel tin-based catalysts (Sn(II)/PN@AC) were prepared using the phosphorus and nitrogen dual-modified activated carbon as support and SnCl2 as active compounds, as well as then evaluated in acetylene hydrochlorination. Under the reaction temperature of 180°C and an acetylene gas hourly space velocity (GHSV-C2 H2) of 30 h–1, the 15%Sn(II)/PN@AC-550 showed the initial acetylene conversion of 100% and vinyl chloride selectivity over 98.5%. Additionally, the deactivation rate of 15%Sn(II)/PN@AC-550 reached 0.47% h–1, which was lower than that of 15%Sn(II)/AC-550 (1.02% h–1), suggesting that PN@AC-550 as novel support can retarded the deactivation of Sn(II)/AC-550 catalysts during acetylene hydrochlorination.
4/3/2023 11:49:55 PM +00:00
Acetylene hydrochlorination over tin nitrogen based catalysts: Effect of nitrogen carbondots as nitrogen precursor
The catalysts comprising the main active compounds of Sn-Nx were synthesized using trichlorophenylstannane ((C6 H5 )Cl3 Sn), nitrogen carbon-dots (NCDs), and activated carbon (AC) as starting materials, and the activity and stability of catalysts was evaluated in the acetylene hydrochlorination. According to the results on the physical and chemical properties of catalysts (TEM, XRD, BET, XPS and TG), it is concluded that NCDs@AC can increase (C6 H5 )Cl3 Sn dispersity, retard the coke deposition of (C6 H5 )Cl3 Sn/AC and lessen the loss of (C6 H5 )Cl3 Sn, thereby further promoting the stability of (C6 H5 )Cl3 Sn/AC. Based on the characterization results of C2 H2 - TPD and HCl adsorption experiments, we proposed that the existence of Sn-Nx can effectively strengthen the reactants adsorption of catalysts.
4/3/2023 11:49:40 PM +00:00
Antiinfective properties of ursolic acid-loaded chitosan nanoparticles against Staphylococcus aureus
The present study aimed to synthesize ursolic acid-loaded chitosan nanoparticles (UA-Ch-NPs) as an antiinfective agent against 21 Staphylococcus aureus isolates. The UA-Ch-NPs were synthesized by a simple method and then characterized by TEM, FTIR, DLS-zeta potential, and XRD analyses. According to the characterization results, highly dispersed spherical nanoparticles with a mean diameter of 258 nm and a zeta potential of + 40.1 mV were developed. The antibacterial properties of UA-Ch-NPs were investigated and their inhibitory effect on biofilm formation was demonstrated by AFM. Finally, the expression levels of icaA and icaD were measured using real-time PCR. Results indicated that the minimum inhibitory concentration (MIC) of UA and UA-Ch-NPs against S. aureus was 64 and 32 µg/mL, respectively.
4/3/2023 11:49:33 PM +00:00
New iodine-apatites: Synthesis and crystal structure
The paper describes methods for the preparation of compounds with an apatite structure containing only iodine atoms in the “halogen” position. The crystal structure of the compounds was refined by the Rietveld method. The resulting apatites have a structure with a space group P63 /m and have the following unit cell parameters. The study of the crystal structure showed a relatively low efficiency of the binding of iodine in the apatite matrix.
4/3/2023 11:49:26 PM +00:00
Photocatalytic decomposition of textile dyestuffs by photosensitive metal oxide catalysts
Textile azo dyes are one of the pollutants in waste water that adversely affect human and environmental health. Removal of these chemicals from wastewater is important for eco-system and human health. In this study, Bi2 O3 nanoflakes and ZnO were synthesized by the co-precipitation method. Adsorption and photocatalytic degradation reactions were carried out to remove dyes (Victoria blue (VB) and Malachite green (MG)) from wastewater with the photocatalysts. In order to improve the activity of catalysts, cetyltrimethylammoniumbromide (CTAB) was added as a surfactant to pure oxide structures, and Bi2 O3 -CTAB and ZnO-CTAB catalysts were prepared. The structural and morphological properties of these catalysts were determined by BET, XRD, DRS, FTIR, and SEM analysis.
4/3/2023 11:49:17 PM +00:00
One‒pot green synthesized protein‒based silver nanocluster as prooxidant biosensor
In this study, silver nanoclusters as prooxidant biosensor were eco‒friendly synthesized using chicken egg white protein without any chemical reducing agents for measuring copper(II)-induced prooxidant activities of catechin, epicatechin, epigallocatechin gallate, resveratrol, gallic acid, chlorogenic acid, and rutin. The prooxidant activities were evaluated via measuring the absorption at 450 nm wavelength of the Cu(I)‒neocuproine chelate formed by extraction of protein-bound Cu(I) with neocuproine reagent. Accuracy was determined by evaluating recovery values of wine, grape and apple samples and the obtained values were between 97.2%‒98.9%. Intraday precision and inter-day reproducibility experiments were studied with three different experiments in a day and three different days respectively.
4/3/2023 11:49:10 PM +00:00
Effect of fuel choice on conductivity and morphological properties of samarium doped ceria electrolytes for IT-SOFC
The present investigation is emphasized on the effect of various combustion agents on the crystal properties, surface microstructure, and oxygen ion conductivity of 20% mole-Sm doped ceria (Ce0.80Sm0.20O1.90/SDC20) ceramics as solid electrolyte for ITSOFCs. The most widely used combustion agents for engineering ceramic production as ethylene glycol, diethylene glycol, triethylene glycol, L-alanine, L-valine, glycine, citric acid monohydrate, urea, and EDTA-citric acid were compared in terms of SDC20 properties. X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and electrochemical impedance spectroscopy (EIS) were used to determine the microstructure properties, crystal structure and ionic conductivity of SDC20 powder.
4/3/2023 11:49:00 PM +00:00
Optimization for esterification of saturated palm fatty acid distillate by D-optimal design response surface methodology for biolubricant production
The results have shown the ester products yields have been significantly increased up to 93% with selectivity of 99% SFA-TMP tri-ester after the optimization process by using D-optimal design. The results for lubrication properties have shown that the SFA PFAD-based esters have low-temperature properties with pour points value in the range of 18–35 °C, flash point (270–310 °C), onset oxidative stability temperature (251–322 °C) and viscosity indices (115–131), respectively. The results showed that the presence of many esters functional groups in the molecule structure of SFA PFAD-based esters provides a positive impact on the lubrication properties. Overall, the results indicated that the SFA PFAD-based esters can be used as biolubricant base oils with pour point depressants.
4/3/2023 11:48:52 PM +00:00
Polycyclic aromatic hydrocarbon-substituted push–pull chromophores: An investigation of optoelectronic and nonlinear optical properties using experimental and theoretical approaches
A series of new push–pull chromophores were synthesized in moderate to very high yields (65%–97%) by treating TCNE and TCNQ with alkynes substituted by electron-rich diethylaniline and polycyclic aromatic hydrocarbons. Some of the chromophores exhibit strong intramolecular charge-transfer bands in the near-IR region with λmax values between 695 and 749 nm. With the help of experimental and theoretical analysis, it is concluded that the trend in λmax values is affected by PAH substituents sterically, not electronically. Steric constraints led to the increased dihedral angles, reducing conjugation efficiencies. The absorption properties of push-pull compounds have been investigated in solvents possessing different polarities.
4/3/2023 11:48:32 PM +00:00
N doping of TiO2 nanocrystal for efficient photodegradation of organic pollutants under ultraviolet and visible light irradiation
To decrease the band gap of TiO2 and enhance its photocatalytic performance, in this work, N-doped nanocrystalline TiO2 is synthesized successfully through a simple sol-gel synthesis process with dicyandiamide used as N source. The N-doped TiO2 photocatalysts have been characterized in detail by means of powder X-ray diffraction, Raman spectroscopy, infrared spectroscopy, UV-vis spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscope. The photocatalytic activities of N-doped TiO2 to different organic pollutants are significantly different.
4/3/2023 11:48:24 PM +00:00
Laccase bound to cryogel functionalized with phenylalanine for the decolorization of textile dyes
: In this study, amino acid functionalized poly(2-hydroxyethyl methacrylate-N-methacrylolyl-l-phenylalanine) [PHEMAPA] cryogel discs were prepared. In this respect, phenylalanine containing N-methacryloyl-(L)-phenylalanine methyl ester (MAPA) was polymerized with 2-hydroxyethyl methacrylate (HEMA) without requirement of any activation step. Laccase bound poly(2-hydroxyethyl methacrylate-N-methacryloyl-l-phenylalanine) [Lac-PHEMAPA] cryogel discs were applied for decolorization of Reactive Blue-247 (RB-247). The ability of Lac-PHEMAPA cryogel discs on dye decolorization was found to be as 90% in 2 h and even more within 4h.
4/3/2023 11:48:16 PM +00:00
Low loaded Pt-Co catalyst surfaces optimized by magnetron sputtering sequential deposition technique for PEM fuel cell applications: Physical and electrochemical analysis on carbon paper support
The results showed that Pt particles, deposited by dc-magnetron gun, surround the large Co-clusters deposited by rf-magnetron gun. In addition, the increase of Co content led to an increase in the electrochemical active surface area (EASA) from 23.75 m2 /gPt to 47.54 m2 /gPt for pure Pt and Pt:Co (1:3), respectively, which corresponded the improvement of the utilization of Pt by a factor of 1.91. This improvement indicated that the sequential magnetron cosputtering was one of the essential technique to deposit homogeneous metal clusters with desirable size on the gas diffusion layer by adjustment plasma parameters.
4/3/2023 11:48:05 PM +00:00
Ultrasound assisted supramolecular liquid phase microextraction procedure for Sudan I at trace level in environmental samples
A method based on supramolecular liquid phase microextraction has been developed for the preconcentration and determination of trace levels of Sudan I. 1-decanol and tetrahydrofuran were used as supramolecular solvent components. Trace levels of Sudan I were extracted into the extraction solvent phase at pH = 4.0 Analytical parameters such as pH value, supramolecular solvent volume, ultrasonication, centrifugation, model solution volume, matrix effects have been optimized. The limit of detection and the limit of quantification values for Sudan I were calculated as 1.74 μg L−1 and 5.75 μg L−1, respectively. In order to determine the accuracy of the method, addition and recovery studies were carried out to environmental samples.
4/3/2023 11:47:55 PM +00:00
Advances in polymer based Friedlander quinoline synthesis
Nitrogen containing heterocyclic compounds has acquired their remarkable and distinct place in the wide area of organic synthesis due to the broad range of applications. Among them, quinoline motifs have attracted researchers in the synthetic chemistry because of its presence in the large number of pharmacologically active compounds. Different methods for synthesis of quinoline derivatives are reported, among them the Friedlander synthesis have provided comparatively more efficient approach. Many of the reported conventional Friedlander methodologies have some problems such as difficult product isolation procedures, poor yields and use of expensive catalysts, etc.
4/3/2023 11:47:43 PM +00:00
Fibroin nanofibers production by electrospinning method
Silk fibroin, which has many characteristic properties such as low inflammation reaction, biodegradation, suppleness, good antithrombogenic details, biocompatibility and high tensile strength is a very good candidate for biomedical applications. Electrospinning procures high surface area, porous, nanofiber dimension fiber generation, which is a plain method. An experimental study was carried out to produce nanofiber structure from silk fibroin by electrospinning and the electrospinning parameters for the spinning of uniform, continuous and silk fibroin fibers were optimized. As a result, the effect of variables of concentration, distance and applied voltage on the strength, thickness, surface structure, fiber diameter of nanomaterial was investigated.
4/3/2023 11:47:31 PM +00:00
Catalytic, theoretical, and biological investigation of an enzyme mimic model
The designed catalyst has shown an enzyme-like kinetics profile with a significant substrate affinity. The cooperative action in between catalytic triad amino acids has shown improved catalytic activity in comparison to only the histidine-containing control group. Histidine is an irreplaceable contributor to catalytic action and this is an additional reason for control group selection. This new method based on the self-assembly of covalently conjugated action units offers a new platform for enzyme investigations and their further applications. Artificial catalyst studies always stayed at the kinetics investigation level, in this work bioactivity of the designed catalyst was shown by the induction of biomineralization of the cells, indicating the possible use of enzyme mimics for biological applications.
4/3/2023 11:47:22 PM +00:00
Preparation and characterization of templated porous carbons from sucrose by one-pot method and application as a CO2 adsorbent
The templated porous carbons were prepared from sucrose by one-pot method. In this method in which the pre-synthesis of the hard template is eliminated, the porous carbons were produced by organic-inorganic self-assembly of sucrose, tetraethyl ortosilicate (TEOS), Pluronic P123 and n-butanol in an acidic medium, and subsequent carbonization. The synthesis parameters such as sucrose amount, TEOS molar ratio and carbonization temperature were evaluated for describing their effects on the pore structures of the synthesized carbons. The prepared porous carbons were characterized by N2 adsorption, thermogravimetric analysis (TGA), Raman spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) techniques.
4/3/2023 11:47:14 PM +00:00
Sensitive and selective determination of imidacloprid with magnetic molecularly imprinted polymer by using LC/Q-TOF/MS
In this paper, magnetic-molecularly imprinted polymer was used for the preconcentration of trace levels of imidacloprid in water and apple samples prior to liquid chromatography-quadrupole-time-of-flight mass spectrometric determination. The selectivity of the magnetic polymer was united with the sensitivity and the high resolving power of the chromatographic system. The developed method showed a linear range from 10.0 to 500.0 µg/L. The quantitative recoveries were obtained for water and apple samples in the range of 92.0%–99.0 %. The relative standard deviations of intra-day and inter-day tests were found to be in the range of 0.8%–1.2% and 1.2%–1.6 %, respectively.
4/3/2023 11:47:08 PM +00:00
Structural and adsorption behaviour of ZnO/aminated SWCNT-COOH for malachite green removal: Face-centred central composite design
In this study, an effective adsorbent was synthesized to remove malachite green (MG), which is one of the toxic dyes. Firstly, single walled carbon nanotube with carboxylated acid (SWCNT-COOH) was functionalized with diethylenetriamine and a new nanocomposite was obtained using nano zinc oxide (ZnO) powder. The effects of pH (3–7), the amount of adsorbent (5–15 mg) and the initial concentration (10–50 mg L–1) of the solution on the adsorption uptake were investigated. The optimal parameters that maximize the adsorption uptake according to the specified working range are found to be 4.63 for pH, 49.94 mg L–1 for initial concentration, 5.25 mg for the adsorbent dose, and the maximum adsorption capacity has been found as 52.26 mg g–1.
4/3/2023 11:46:43 PM +00:00
Fabrication and characterization of enhanced hydrazine electrochemical sensor based on gold nanoparticles decorated on the vanadium oxide, ruthenium oxide nanomaterials, and carbon nanotubes composites
This work describes the synthesis of mixed oxide film of vanadium and ruthenium by pulsed deposition technique on multiwall carbon nanotubes and the decoration of gold nanoparticles on the mixed film. A ternary electrocatalyst has been developed for the electrochemical oxidation of hydrazine by combining two metal oxide mixtures with Au nanoparticles. Surface morphology and chemical composition of the electrode have been examined with SEM, EDX, HRTEM, EIS, and XRD. The peak current of hydrazine increased 9 times at the AuNPs/(VOx-RuOx)/CNT/GCE compared to the bare GCE, and the peak potential shifted to negative 848 mV.
4/3/2023 11:46:34 PM +00:00
Preconcentration of rifampicin prior to its efficient spectroscopic determination in the wastewater samples based on a nonionic surfactant
This research work is focused on the cloud point extraction (CPE) procedure for the preconcentration of rifampicin prior to its determination in water. The UV/vis spectrophotometric method was adapted for the measurement of rifampicin content after the phase separation. Triton-X 100 was used as the nonionic surfactant which contains hydrophilic polyethylene chain feasible for the extraction of analyte. Various analytical parameters that can affect the extraction efficacy were optimized to achieve linearity of the proposed method in the concentration range of 3.54–81.41 mgL–1. The Limit of detection and quantification were 1.261 and 4.212 mgL–1, respectively.
4/3/2023 11:46:24 PM +00:00
Adsorptive performance of MWCNTs for simultaneous cationic and anionic dyes removal; kinetics, thermodynamics, and isotherm study
Disposal of contaminated wastewater causes many serious problems especially when it gets mixed with the ground and seawater. It is, therefore, important to apply any remedial action to eradicate dangerous pollutants from the aqueous effluents and to avoid exposure of this wastewater to aquatic life. The research results discussed herein deal with the removal of Rhodamine B (RhB) and Congo Red (CR) dye from wastewater by using multi-walled carbon nanotubes (MWCNTs) as an adsorbent. Different factors like solid dosage, initial pH and concentration, time, and temperature were studied to understand the behavior and mechanism of adsorption.
4/3/2023 11:46:14 PM +00:00
Remarkable bismuth-gold alloy decorated on MWCNT for glucose electrooxidation: The effect of bismuth promotion and optimization via response surface methodology
In this study, the carbon nanotube supported gold, bismuth, and gold-bismuth (Au/MWCNT, Bi/MWCNT, and Au-Bi/ MWCNT) nanocatalysts were prepared with NaBH4 reduction method at varying molar atomic ratio for glucose electrooxidation (GAEO). The synthesized nanocatalysts at different Au: Bi atomic ratios are characterized via x-ray diffraction (XRD), transmission electron microscopy (TEM), and N2 adsorption-desorption. For the performance of AuBi/MWCNT for GAEO, electrochemical measurements are performed by using different electrochemical techniques namely cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS).
4/3/2023 11:45:55 PM +00:00
Hybrid paper sheets with improved barrier properties
Hybrid paper sheets were prepared by applying a thin coating layer of cross-linked polydimethylsiloxane (PDMS) and inorganic particles onto Whatman Grade 1 filter paper substrates. Several coatings with different inorganic particle contents and types were applied onto the paper substrates to investigate the effect of the variation in the coating formulation on the (i) wetting, (ii) water barrier properties, (iii) air barrier properties, (iv) surface roughness, and (v) mechanical properties of the samples. It was revealed that the superhydrophobic hybrid paper sheets with significantly low air permeability and high water barrier properties could be prepared which is an indication that the method proposed can be used for the preparation of packaging materials.
4/3/2023 11:45:42 PM +00:00
Quercetin enhances vitamin D2 stability and mitigate the degradation influenced by elevated temperature and pH value
The results obtained revealed vit. D2 degradation was drastically increased with longer incubation under thermal treatment. However, quercetin and vit. D2 groups were able to significantly inhibit the degradation of vit. D2 and stabilize it, evaluated through the retention percentage. We also exposed vit. D2 at solutions with different pH values (1, 4, 5, 7, 10). Quercetin exerted vit. D2 anti-degradation at different pH values as well as under thermal pressure at different time points. Conclusively, quercetin can be an effective way to reduce temperature and pH induced degradation of vit. D2.
4/3/2023 11:45:34 PM +00:00
Structural rearrangement of Neisseria meningitidis transferrin binding protein A (TbpA) prior to human transferrin protein (hTf) binding
Gram-negative bacterium Neisseria meningitidis, responsible for human infectious disease meningitis, acquires the iron (Fe3+) ion needed for its survival from human transferrin protein (hTf). For this transport, transferrin binding proteins TbpA and TbpB are facilitated by the bacterium. The transfer cannot occur without TbpA, while the absence of TbpB only slows down the transfer. Thus, understanding the TbpA-hTf binding at the atomic level is crucial for the fight against bacterial meningitis infections. In this study, atomistic level of mechanism for TbpA-hTf binding is elucidated through 100 ns long all-atom classical MD simulations on free (uncomplexed) TbpA.
4/3/2023 11:45:24 PM +00:00