Tài liệu miễn phí Hoá học
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The protective role of melatonin under heavy metal-induced stress in Melissa Officinalis L
In this paper, the protective role of melatonin in counteracting metal-induced free radical generation was highlighted. Using the HPLC-FLD technique melatonin was identified and quantified in the roots and leaves of lemon balm (Melissa officinalis L.), grown under photoperiod conditions. Furthermore, the response of plants pre-treated with exogenous 0.1 mM melatonin to the increased zinc (Zn) and cadmium (Cd) concentrations was observed, with changes in mineral (Ca, Mg), physiological and antioxidant status of the plant during heavy metals stress. The obtained melatonin concentrations were the highest published for dry plants so far. Elevated Cd and Zn levels in soil caused alternation in biochemical and physiological parameters of lemon balm leaves and roots.
4/3/2023 11:40:06 PM +00:00
Thermal stresses in SOFC stacks: The role of mismatch among thermal conductivity of adjacent components
Generating power from renewable biogas in solid oxide fuel cells (SOFCs) is an environment-friendly, efficient, and promising energy conversion process. Biogas can be used in SOFCs via a reforming process for which dry reforming is more suitable as the reforming agent exists in the biogas mixture. Biogas can be directly reformed to H2 -rich fuel stream in the anode chamber of a SOFC by the heat released during power generation. Exploiting the heat and water produced in the SOFC for internal reforming of biogas makes the energy conversion process very efficient; however, various challenges are reported. Thus, indirect internal reforming is opted for which a separate reforming domain is required. In an indirect internal reformer operating at usual conditions, dry reforming rate is quite high in the inlet and it decreases steeply toward the fuel outlet.
4/3/2023 11:39:52 PM +00:00
Unsymmetrical zinc phthalocyanines containing thiophene and amine groups as donor for bulk heterojunction solar cells
Photovoltaic technology is an alternative resource for renewable and sustainable energy and low costs organic photovoltaic devices such as bulk-heterojunction (BHJ) solar cells, which are selective candidates for the effective conversion of solar energy into electricity. Asymmetric phthalocyanines containing electron acceptor and donor groups create high photovoltaic conversion efficiency in dye sensitized solar cells. In this study, a new unsymmetrical zinc phthalocyanine was designed and synthesized including thiophene and amine groups at peripherally positions for BHJ solar cell. T
4/3/2023 11:39:43 PM +00:00
The impact of alkaline earth oxides on Bi2O3 and their catalytic activities in photodegradation of Bisphenol A
The BPA into wastewater has posed a threat to environment and human health. Hence, we aimed to eliminate BPA in a short time and with a rapid degradation rate from food wastewater. Herein, the effects of different alkaline-earth oxide doped with Bi2O3 nanoparticles on the photocatalytic degradation of bisphenol A were investigated. SrO-Bi2O3, CaO-Bi2O3, and MgO-Bi2O3 binary oxides were prepared by wet-impregnation method. The structural and optical features of catalysts were clarified BET, XRD, DRS, FTIR, PL, and SEM techniques.
4/3/2023 11:39:31 PM +00:00
Investigation of performances of commercial diesel oxidation catalysts for CO, C3H6, and NO oxidation
Four commercial monolithic diesel oxidation catalysts (DOCs) with two different platinum group metal (PGM) loadings and Pt:Pd ratios of 1:0, 2:1, 3:1 (w/w) were investigated systematically for CO, C3H6, and NO oxidation, CO-C3H6 co-oxidation, and COC3H6-NO oxidation reactions via transient activity measurements in a simulated diesel engine exhaust environment. As PGM loading increased, light-off curves shifted to lower temperatures for individual and co-oxidation reactions of CO and C3H6. CO and C3H6 were observed to inhibit the oxidation of themselves and each other. Addition of Pd to Pt was found to enhance CO and C3H6 oxidation performance of the catalysts while the presence and amount of Pd was found to increase the extent of self-inhibition of NO oxidation.
4/3/2023 11:39:22 PM +00:00
Evaluation of the fuel cell performances of TiO2/PAN electrospun carbon-based electrodes
lectrocatalytic effect of the untreated and TiO2 +polyacrylonitrile (PAN) modified discarded battery coal (DBC) and pencil graphite electrodes (PGE) were evaluated in fuel cell (FC) applications. TiO2+PAN solution is coated on PGE and DBC electrodes by electrospinning. According to the FESEM and EDS characterizations, TiO2 and PAN nanofibers are found to be approximately 40 and 240 nm in size. TiO2+PAN/PGE showed the best FC performances with 2.00 A cm–2 current density and 5.05 W cm–2 power density values, whereas TiO2+PAN/DBC showed 0.68 A cm–2 current density and 0.62 W cm–2 power density values.
4/3/2023 11:39:13 PM +00:00
Integrated 3D-QSAR, molecular docking, and molecular dynamics simulation studies on 1,2,3-triazole based derivatives for designing new acetylcholinesterase inhibitors
The molecular features characteristics provided by the 3D-QSAR contour plots were quite useful for designing and improving the activity of acetylcholinesterase of this class. Based on these findings, a new series of 1,2,3-triazole based derivatives were designed, among which compound A1 with the highest predictive activity was subjected to detailed molecular docking and compared to the most active compound. The selected compounds were further subjected to 20 ns molecular dynamics (MD) simulations to study the comparative conformation dynamics of the protein after ligand binding, revealing promising results for the designed molecule. Therefore, this study could provide worthy guidance for further experimental analysis of highly effective acetylcholinesterase inhibitors.
4/3/2023 11:39:04 PM +00:00
Synthesis, characterization, and biological evaluation of new copper complexes of naphthyl pyrazole ligands
Two naphthalene pyrazole ligands were synthesized using KOH/DMSO and Cu catalyst and characterized with FT-IR, ESIMS, 1H, and 13C NMR spectroscopies. The crystal structures of 1-(2-methylnaphthalen-1-yl)-1H-pyrazole (MeNap-Pz) ligand have been determined with X-ray crystal structure analysis. Reaction of the ligands with Cu(NO3)2x3.5H2O gave two new complexes and characterized with magnetic susceptibility, molar conductance, FT-IR, LCMS-MS, ICP-OES, NMR, thermogravimetric analysis, and ESR spectra. The spectral data of the ligands are coordinated to the metal ion through the nitrogen atoms of the pyrazole ring. Consequently, it has been determined that [Cu(MeNap-Pz)2(NO3)]NO3.2H2O complex showed square planar geometry and [Cu(NapMe-Pz)2(NO3)2].H2O complex showed octahedral geometry. All compounds were screened for in vitro antibacterial activity and copper complexes have been shown to be effective on bacteria.
4/3/2023 11:38:55 PM +00:00
Synthesis, spectroscopic, thermal, crystal structure properties and characterization of new Hofmann-type-like clathrates with 4-aminopyridine and water
In this study, synthesis of two new heteronuclear tetracyanonickelate(II) clathrates based on 4-aminopyridine (4AP) and guest water (H2O) molecule and investigation of their structural properties were reported. These clathrates were characterized by using vibration spectroscopy, elemental, thermal analysis and single crystal X-ray diffraction (SC-XRD) techniques. Examining the elemental and spectral data of these clathrates, it was observed that the formulas [Zn(II)(4AP)2Ni(µ-CN)2(CN)2]·6H2O and [Cu(II)(4AP)4Ni(µCN)2(CN)2]·H2O were defined their structures. General information about the structural properties of these clathrates in single crystal form has been obtained by considering the changes in the characteristic peaks of the cyanide group and the 4AP that formed them.
4/3/2023 11:38:46 PM +00:00
Electrochemical investigation of the interaction of 2,4-D and double stranded DNA using pencil graphite electrodes
2,4-dichlorophenoxyacetic acid (2,4-D) is an auxinic herbicide used to control broadleaf weeds. It is also a threatening factor for not only aquatic life but also human health due to its genotoxicity and endocrine disruptive property. Herein, the interaction between 2,4-D and double stranded DNA was investigated by using single-use pencil graphite electrodes (PGE) in combination with electrochemical techniques. The detection mechanism was based on the monitoring of the changes at the guanine oxidation signal obtained before/after surface-confined interaction of 2,4-D and DNA at the surface of PGE. The electrochemical characterization of the interaction was studied by using microscopic and electrochemical techniques.
4/3/2023 11:38:37 PM +00:00
Synthesis and characterization of biodegradable palm palmitic acid based bioplastic
This study involves the quantitative analysis of high free fatty acid crude palm oil, the separation of palmitic acid and synthesis of palm palmitic acid-based bioplastic. Synthesis of dimethyl 2-tetradecylmalonate (DMTDM) using methyl palmitate (MP) with sodium hydride (NaH) in the presence of reactive solvent of dimethyl carbonate (DMC) was carried out. The reaction conditions comprise at a mole ratio of MP: DMC: NaH: dimethylformamide (DMF) (0.1:2:0.25:1) at 60°C for 14 h with 88.3 ± 1.4% yield. FTIR spectra of DMTDM showed the ester carbonyl group at 1740 cm–1. The polymerization of DMTDM with 1,6-hexandiol or 1,12-dodecandiol was carried out using titanium (IV) isopropoxide Ti(OiPr)4 as the catalyst and reaction time of 24 h.
4/3/2023 11:38:22 PM +00:00
Synthesis, characterization and catalytic properties of cationic N-heterocyclic carbene silver complexes
Three new dibenzimidazolium salts bridged by 2-methylenepropane-1,3-diyl group were synthesized. Their dinuclear N-heterocyclic carbene Ag(I) complexes were prepared by the reactions of these salts with Ag2 O. The structures of the synthesized compounds were defined by nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), elemental analysis, and LC-MSMS (for complexes) techniques. Stability of the silver complexes was confirmed by 1H NMR spectroscopy. Catalytic activities of Ag(I) compounds were tested for three-component coupling reaction of some aldehydes, amines, and phenylacetylene.
4/3/2023 11:38:11 PM +00:00
Tin-sulfur based catalysts for acetylene hydrochlorination
In the present work, tin-sulfur based catalysts were prepared using Na2SO3 and (CH3SO3)2 Sn and were tested in acetylene hydrochlorination. Based on the analysis of experiments results, the acetylene conversion of (CH3SO3)2 Sn/S@AC is still over 90%after a 50 h reaction, at the reaction conditions of T = 200oC, VHCl/VC2H2 = 1.1:1.0 and C2H2-GSHV = 15 h–1. According to the results of X-ray photoelectron spectroscopy (XPS), HCl adsorption experiments, and acetylene temperature programmed desorption (C2H2-TPD), it is reasonable to conclude that the interaction between Sn and S not only can retard the oxidation of Sn2+ in catalysts but also strengthen the reactant adsorption capacity of tin-based catalysts.
4/3/2023 11:37:58 PM +00:00
Removal of COD, aromaticity and color of a pretreated chemical producing industrial wastewater: A comparison between adsorption, ozonation, and advanced oxidation processes
A wide range of products are produced in the chemical producing industry such as textile dyes, chemicals, printing dyes and chemicals, paper chemicals, electrostatic powder dyes, and optical brighteners. The aim of this study is to investigate the treatability of chemical oxygen demand (COD), aromaticity, and color in the wastewater of this sector, where highly complex chemicals are used. Most of the studies in the literature are related to the treatment of synthetically prepared dyed wastewater. This study is important as it is carried out with real wastewater and gives results of many treatment methods. In the study, COD, UV-vis absorbance, and color values were attempted to be removed from the wastewater of a chemical producing industry that was pretreated by coagulationflocculation.
4/3/2023 11:37:50 PM +00:00
Synthesis and characterization of magnetic nanocomposite for in vitro evaluation of irinotecan using human cell lines
: In this study, magnetic O-carboxymethyl chitosan (MOCC) nanocomposite was synthesized and characterized as a drug delivery system for loading the anticancer drug irinotecan (CPT-11). To increase the drug loading capacity, MOCC was synthesized by linking the carboxyl group functionally to chitosan. Also, several critical factors such as concentration, the dose of MOCC, and contact time for optimum drug loading condition were investigated. The loading capacity of CPT-11 onto MOCC was calculated as 5.6 mg/g, and the loaded drug concentration was calculated as 0.04787 mM at pH value of 5.
4/3/2023 11:37:40 PM +00:00
Synthesis and biological evaluation of new pyrazolebenzene-sulphonamides as potential anticancer agents and hCA I and II inhibitors
Cancer is a disease characterized by the continuous growth of cells without adherence to the rules that healthy normal cells obey. Carbonic anhydrase I and II (CA I and CA II) inhibitors are used for the treatment of some diseases. The available drugs in the market have limitations or side effects, which bring about the need to develop new drug candidate compound(s) to overcome the problems at issue. In this study, new pyrazole-sulphonamide hybrid compounds 4-[5-(1,3-benzodioxol-5-yl)-3-aryl-4,5-dihydro-1Hpyrazol-1-yl]benzenesulphonamides (4a - 4j) were designed to discover new drug candidate compounds. The compounds 4a - 4j were synthesized and their chemical structures were confirmed using spectral techniques.
4/3/2023 11:37:28 PM +00:00
Spectroscopic investigation of defect-state emission in CdSe quantum dots
CdSe quantum dots are the most studied Cd-based quantum dots with their high quantum yield, high photostability, narrow emission band, and easy synthesis procedure. They are frequently used to develop light emitting diode (LED) due to their unique photophysical properties; however, their narrow emission band causes a challenge to design white LEDs because white light emission requires emission in multiple wavelengths with broad emission bands. Here in this study, we developed CdSe quantum dots with a narrow bandedge emission band and broad defect-state emission band through a modified two-phase synthesis method.
4/3/2023 11:37:16 PM +00:00
Graphene preparation and graphite exfoliation
The synthesis of Graphene is critical to achieving its functions in practical applications. Different methods have been used to synthesis graphene, but graphite exfoliation is considered the simplest way to produce graphene and graphene oxide. In general, controlling the synthesis conditions to achieving the optimum yield, keeping the pristine structure to realize on-demand properties, minimum layers with the smallest lateral size, and minimum oxygen content are the most obstacles experienced by researchers. Each application requires a specific graphene model, graphene oxides GO, or even graphene intercalated compounds (GIC) depending on synthesis conditions and approach. This paper reviewed and summarized the most researches in this field and focusing on exfoliation methods.
4/3/2023 11:37:04 PM +00:00
Rhenium/rhenium oxide nanoparticles production using femtosecond pulsed laser ablation in liquid
In this study, rhenium/rhenium oxide nanoparticles (Re/ReO3NPs) have been produced for the first time in ultrapure water by using Femtosecond Pulsed Laser Ablation in Liquid (fsPLAL) method. X-Ray Diffraction (XRD) measurements and results obtained for NPs show the existence of well-crystallized peaks and preferred phases. Re NPs have hexagonal structure while ReO3 NPs have the perovskite-like cubic crystal structures. The Re/ReO3 ratio is also determined to be 53/47 with ~ 20 nm crystallite size, while pure ReO3 crystallite sizes were measured to be ~ 25 nm. The TEM results have shown that the produced particles have a spherical shape, and particle sizes changes between ~ 20 nm and ~ 60 nm.
4/3/2023 11:36:53 PM +00:00
Synthesis of some NH- and NH,S- substituted 1,4-quinones
A series of NH-substituted-1,4-quinones, possessing one, two, three or not chlorine, were synthesized by the reaction between different quinones (p-chloranil (1), p-toluquinone (2), or 2,3-dichloro-1,4-naphthoquinone (3)) and (-)-cis-myrtanylamine (5) via nucleophilic reactions. Moreover, 2-bromo-1,4-naphthoquinone (4) was reacted with 2-(methylthio)ethylamine (11) to produce aminosubstituted naphthoquinones (12 and 13), bearing with bromine and not bromine. In addition, 2-bromo-1,4-naphthoquinone (4) was reacted with 4′-aminodibenzo-18-crown-6 (14) and 4′-aminobenzo-18-crown-6 (16) to yield crown-containing 1,4-naphthoquinones (15 and 17), respectively. New compounds were characterized, providing 1 H NMR, 13C NMR, FTIR, MS-ESI, UV/Vis and elemental analysis.
4/3/2023 11:36:42 PM +00:00
Development of a spiramycin sensor based on adsorptive stripping linear sweep voltammetry and its application for the determination of spiramycin in chicken egg samples
Herein, an adsorptive stripping linear sweep voltammetric technique was described to determine spiramycin, a macrolide antibiotic, using a carboxylic multiwalled glassy carbon electrode modified with carbon nanotubes. The main principle of the analytical methodology proposed was based on the preconcentration of spiramycin by open-circuit accumulation of the macrolide onto the modified electrode surface. As a result of the adsorption affinity of spiramycin to the modified surface, the sensitivity of the glassy carbon electrode was significantly increased for the determination of spiramycin. The electrochemical behavior of spiramycin was evaluated by cyclic voltammetry and the irreversible anodic peak observed was measured as an analytical signal in the methodology.
4/3/2023 11:36:35 PM +00:00
The effect of H2O on the sulfation of Havelock limestone under oxy-fuel conditions in a thermogravimetric analyser
A gas mixture representing oxy-fuel combustion conditions was employed in a thermogravimetric analyser to determine the effect of water vapor and SO2 concentration on limestone sulfation kinetics over the temperature range of 800 to 920°C. Here, experiments used small samples of particles (4 mg), with small particle sizes (dp < 38 µm) and large gas flow rates (120 mL/min@ NTP) in order to minimize mass transfer interferences. The gas mixture contained 5000 ppmv SO2, 2% O2, and the H2O content was changed from 0% to 25% with the balance CO2. When water vapor was added to the gas mixture at lower temperatures (800–870°C), the limestone SO2 capture efficiency increased.
4/3/2023 11:36:24 PM +00:00
Preparation of glutathione loaded nanoemulsions and testing of hepatoprotective activity on THLE-2 cells
To improve bioavailability and stability of hydrophobic and hydrophilic compounds, nanoemulsions are good alternatives as delivery systems because of their nontoxic and nonirritant nature. Glutathione (GSH) suffers from low stability in water, where its encapsulation in nanoemulsions is a powerful strategy to its stability in aqueous systems. The aim of this study was to obtain nanoemulsions from the hydrophobic/hydrophilic contents of N. sativa seed oil so as to improve GSH stability along with bioavailability of N. sativa seed oil. Then, the prepared nanoemulsions were tested for in vitro hepatoprotective activity against ethanol toxicity. To the best of our knowledge, there is no study on the test of nanoemulsions by the combination of Nigella sativa seed oils and GSH in hepatoprotective activity.
4/3/2023 11:36:16 PM +00:00
Detection of alkanolamines in liquid cement grinding aids by HPLC coupled with evaporative light scattering detector
Triethanolamine (TEA), triisopropanolamine (TIPA), diethanol isopropanolamine (DEIPA) are necessary cement additives, and knowing their contents is needed for quality control and also to understand final properties of the cement. Whether it is the production of grinding aids, technical research and development or application research all involve the detection of grinding aids. This work developed a simple analytical technique for the simultaneous analysis of these alkanolamines in liquid cement grinding aids using high-performance liquid chromatography (HPLC) combined with evaporative light scattering detection (ELSD).
4/3/2023 11:36:09 PM +00:00
Dispersive liquid-liquid microextraction for the isolation and HPLC-DAD determination of three major capsaicinoids in Capsicum annuum L.
Dispersive liquid-liquid microextraction (DLLME) was combined with high-performance liquid chromatography-diodearray detector (HPLC-DAD) for the extraction and quantitation of three major capsaicinoids (i.e. capsaicin, dihydrocapsaicin and nordihydrocapsaicin) from pepper (Capsicum annuum L.). Chloroform (extraction solvent, 100 μL), acetonitrile (disperser solvent, 1250 μL) and 30 s extraction time were found optimum. The analytes were back-extracted into 300 μL of 50 mM sodium hydroxide/ methanol, 45/55% (v/v), within 15 s before being injected into the instrument. Enrichment factors ranged from 3.3 to 14.7 and limits of detection from 5.0 to 15.0 µg g–1. Coefficients of determination (R2) and %RSD were higher than 0.9962 and lower than 7.5%, respectively.
4/3/2023 11:36:00 PM +00:00
Fabrication and characterization of amidoxime-functionalized silica decorated with copper: A catalytic assembly for rapid reduction of dyes
In this study, amidoxime-functionalized silica decorated with copper (AFS-Cu) was fabricated and tested for its catalytic application. Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, and X-ray diffraction were employed to characterize its structure and morphology. The application of AFS-Cu as a catalyst for the catalytic reduction of methylene blue (MB) in aqueous media using NaBH4 as reductant was evaluated. The ability to reuse as well as the effect of catalyst dose and pH of solution on the catalytic activity was investigated.
4/3/2023 11:35:49 PM +00:00
Comparative study on the effect of precursors on the morphology and electronic properties of CdS nanoparticles
Cadmium dithiocarbamate and cadmium ethyl xanthate complexes were synthesized and characterized by microanalysis, Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analyses. The complexes were employed as molecular precursors for the fabrication of CdS nanoparticles in hexadecylamine (HDA) and oleylamine (OLA) at a temperature of 250 °C. Spherical and oval shaped particles with sizes ranging from 9.93 ± 1.89 to 16.74 ± 2.78 nm were obtained in OLA while spherical, oval and rod shaped particles with sizes ranging from 9.40 ± 1.65 to 29.90 ± 5.32 nm were obtained in HDA.
4/3/2023 11:35:36 PM +00:00
Phytochemical characterisation of Phlomis linearis Boiss. & Bal and screening for anticholinesterase, antiamylase, antimicrobial, and cytotoxic properties
In the present work, essential oil and fatty acids and extracts obtained from aerial parts of Phlomis linearis Boiss. & Bal. were investigated for chemical composition and biological activities. The phytochemical analyses were conducted with gas chromatographymass spectrometry/flame ionisation detector (GC-MS/FID) and liquid chromatography-mass spectromtetry (LC-MS/MS) techniques. The extracts and essential oil were studied for α-amylase and acetylcholinesterase activities with two different spectrophotometric methods. Antimicrobial activities of the extracts were investigated by microdilution. The extracts were evaluated in vitro for cytotoxic effects against cancer and normal cell lines by MTT assay.
4/3/2023 11:35:29 PM +00:00
Accelerated FeIII/FeII redox cycle of Fenton reaction system using Pd/NH2-MIL-101(Cr) and hydrogen
In this paper, a novel improvement in the catalytic Fenton reaction system named MHACF-NH2-MIL-101(Cr) was constructed based on H2 and Pd/NH2-MIL-101(Cr). The improved system would result in an accelerated reduction in FeIII, and provide a continuous and fast degradation efficiency of the 10 mg L-1 4-chlorophenol which was the model contaminant by using only trace level FeII. The activity of Pd/NH2-MIL-101(Cr) decreased from 100% to about 35% gradually during the six consecutive reaction cycles of 18 h. That could be attributed to the irreversible structural damage of NH2-MIL-101(Cr).
4/3/2023 11:35:11 PM +00:00
Removal of Cd(II), Cu(II), and Pb(II) by adsorption onto natural clay: A kinetic and thermodynamic study
In this work, we study the elimination of three bivalent metal ions (Cd2+, Cu2+, and Pb2+) by adsorption onto natural illitic clay (AM) collected from Marrakech region in Morocco. The characterization of the adsorbent was carried out by X-ray fluorescence, Fourier transform infrared spectroscopy and X-ray diffraction. The influence of physicochemical parameters on the clay adsorption capacity for ions Cd2+, Cu2+, and Pb2+, namely the adsorbent dose, the contact time, the initial pH imposed on the aqueous solution, the initial concentration of the metal solution and the temperature, was studied. The adsorption process is evaluated by different kinetic models such as the pseudo-first-order, pseudo-second-order, and Elovich.
4/3/2023 11:35:02 PM +00:00