A2019 by Abdullah M. Asiri
Surface tension and steady-state fluorescence measurements have been done for mixtures of bile sa... more Surface tension and steady-state fluorescence measurements have been done for mixtures of bile salts, namely sodium cholate (NaC) + sodium tourocholate (NaTC) and sodium cholate + sodium de-oxycholate (NaDC) at 298.15 K. From the experimental critical micelle concentration (cmc), the interaction parameter has been figured utilizing the regular solution theory proposed by Rubingh for mixed surfactant systems. The ideal cmc values and thermodynamic properties of micellization were evaluated. The Rosen model was used to calculate the various surface parameters. The interaction between NaC + NaDC surfactants was observed to be stronger than in NaC + NaTC. The stronger interaction of NaC + NaDC was also confirmed by fluorescence data. The steady-state fluorescence quenching method was applied to compute the micelle aggregation number, Stern-Volmer constant and micropolarity of single and mixed bile salt systems.
The condensation reaction of 5-amino-3-methyl-1-phenylpyrazole-4-carboxaldehyde with enol lactone... more The condensation reaction of 5-amino-3-methyl-1-phenylpyrazole-4-carboxaldehyde with enol lactone was carried out to get the expected compound involving translactonization type rearrangement. However , the reaction did not proceed as visualized and afforded rather unexpected compound 3,6-dimethyl-1,8-diphenyl-diazocino [3,4-c:7,8-c']bispyrazole as a result of Friedlander condensation. The structure was confirmed by spectroscopic determination and further studied using density functional theory (DFT) calculations. The FT-IR and 1 H NMR values were calculated and compared with those experimentally obtained in spectra. The frontier molecular orbitals (HOMO and LUMO) and molecular electrostatic potential were computed to determine the distribution of charge density and possible site for electro-philic and nucleophilic reactions. The newly synthesized compound was screened for their anti-inflammatory and antibacterial activities using formalin-induced paw edema and agar diffusion methods respectively. It was found to possess significant activities on animals models and against Gram-positive and Gram-negative bacteria.
in Wiley Online Library (wileyonlinelibrary.com). Organometallic macromolecules such as ferroceny... more in Wiley Online Library (wileyonlinelibrary.com). Organometallic macromolecules such as ferrocenyl bis-pyrazoline (2, 3) and bis-pyrimidine (4, 5) derivatives were synthesized by reacting ferrocenyl bis-chalcone 1 with thiosemicarbazide/phenylhydrazine/gua-nidine hydrochloride/thiourea, respectively, under microwave irradiation. Ferrocenyl bis-chalcone 1 was synthesized by reacting acetyl ferrocene with terephthalaldehyde. Synthesized compounds were characterized by using IR, 1 H NMR, 13 C NMR, EI-MS, and elemental analysis. In vitro antibacterial activity against two Gram-negative and two Gram-positive bacteria was determined by the disc diffusion assay. Moreover, minimum inhibition concentrations were also measured with reference to chloramphenicol. Thioamide functionally containing ferrocenyl bis-pyrazoline derivative 2 shows the best antibacterial activity on Escherichia coli and Salmonella typhimurium, among all tested compounds including the reference drug chlorampheni-col. The structure-activity relationship is also developed by using computational calculations with density functional theory (DFT)/B3LYP method.
A conductometric study of the mixed micellization behavior between cetyltrimethylammonium bromide... more A conductometric study of the mixed micellization behavior between cetyltrimethylammonium bromide (CTAB, a cationic surfactant) and sodium dodecyl sulfate (SDS, an anionic surfactant) was carried out in the absence/ presence of various percentages of chitosan in the temperature range of 298.15-318.15 K. The deviations of critical micelle concentration (cmc) from the ideal values indicate the interaction between CTAB and SDS. The micellar mole fraction values according to different proposed models X 1 Rub (Rubingh), X 1 M (Motomura), X 1 Rod (Rodenas), and X 1 id (ideal mole fraction) were estimated and the results obtained reveal the high contribution of CTAB in the mixed micellization, which enhances with the increase of the mole fraction of CTAB. The negative magnitudes of ΔG 0 m indicate the spontaneous formation of mixed micelles between CTAB and SDS. The values of activity coefficients (f 1 and f 2 ) were less than unity and the values of the interaction parameter (β) are negative in all cases, which indicate the attractive interaction between CTAB and SDS. The negative values of excess free energy of micellization (ΔG ex ) signify the stability of the mixed micelles. The negative values of ΔH 0 m in the chitosan systems indicate that micellization is exothermic. The values of ΔS 0 m were found to be positive in all cases. Scheme 1 Molecular structure of SDS Scheme 2 Molecular structure of CTAB Scheme 3 Molecular structure of chitosan 138 J Surfact Deterg J Surfact Deterg (2019) 22: 137-152 139 J Surfact Deterg J Surfact Deterg (2019) 22: 137-152 a Standard uncertainties (u) limits are uΔG 0 m ) = AE3%, u(ΔH 0 m ) = AE3%, and u(ΔS 0 m ) AE4%.
Plant-based materials are reported to have a wide range of applications in the environmental and ... more Plant-based materials are reported to have a wide range of applications in the environmental and bio-medical sectors. In this report, we present an economic and environmentally friendly supported turmeric powder (TP) biomass for the support of Ag, Ni and Cu nano-particles (NPs) designated as Ag@TP, Ni@TP and Cu@TP. The in situ syntheses of the stated NPs were achieved in aqueous medium using NaBH 4 as a reducing agent. The prepared NPs were applied for the degradation of o-nitro-phenol (ONP), m-nitrophenol (MNP), p-nitrophenol (PNP), methyl orange (MO), Congo red (CR), rhodamine B (RB) and methylene blue (MB). Initially, Ag@TP, Ni@TP and Cu@TP were screened for the MO dye and antibacterial activity, where Ag@TP displayed the strongest catalytic activity for MO and bactericidal activities as compared to Ni@TP and Cu@TP. The quantity of metal ions adsorbed onto the TP was investigated by atomic absorption spectroscopy. The Ag@TP, Ni@TP and Cu@TP were characterized through X-ray diffraction (XRD), attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, thermal gravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDS) and field emission scanning electron microscope (FESEM) analysis.
In this study, plant-mediated copper nanoparticles (CuNPs) were synthesized. Due to its direct sy... more In this study, plant-mediated copper nanoparticles (CuNPs) were synthesized. Due to its direct synthesis mechanism and eco-friendly nature, the current method accounts for the green chemistry approach using the fruit extract of Duranta erecta for the first time. The UV-visible spectrum of the CuNPs solution showed a distinct absorption peak at 588 nm. Fourier transform infrared spectroscopy confirmed that the fruit extract is responsible for the reduction as well as the stabilization of CuNPs. X-ray diffraction patterns conform the crystalline nature of CuNPs. Energy-dispersive X-ray spectros-copy was performed for elemental analysis whereas field emission scanning electron microscopy was carried out for surface morphology. Prepared CuNPs were used for the reduction of carcinogenic azo dyes methyl orange (MO) and congo red (CR). CuNPs exhibit outstanding catalytic reduction for MO and CR in the presence of NaBH 4 as reducing agents with the pseudo-first-order rate constants of 8.6 × 10 −3 s −1 and 5.07 × 10 −3 s −1 for MO and CR, respectively. Thus, natural plant materials act as cheap and environmentally friendly support for the synthesis of CuNPs and could be used for the purification of water from organic dye effluents.
The aim of the presented work was to assess the potential of Medicago polymorpha extract to synth... more The aim of the presented work was to assess the potential of Medicago polymorpha extract to synthesize silver nanoparticles (AgNPs) as a green method. It was a simple one-step synthesis approach and the product obtained was characterized by UV-visible spectroscopy, Fourier transform infrared (FTIR), powder X-ray diffraction, thermogravimetric analysis, and field-emission scanning electron microscopy (FE-SEM). At room temperature, the optimum time for the completion of the reaction (i.e. the formation colloidal solution) was just 5 min. FE-SEM images showed that AgNPs were predominantly in spheres, whereas FTIR spectrum analysis inferred that gallic acid present in the extract initially reduced silver ions to elemental silver. The carboxylic and hydroxyl groups of biomolecules present in the extract stabilized AgNPs by passivating the surface to prevent aggregation, resulting in uniform distribution. The antibacterial activity of synthesized AgNPs showed effective inhibitory effects against waterborne pathogens, including Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), at a minimum inhibitory concentration of 10 μg/ml. Membrane permeability and respiration studies were also performed to assess the surface role of the synthesized AgNPs. The prepared AgNPs exhibited excellent antioxidant activity and catalytic reduction of methyl orange with a rate constant of 6.8 × 10 −3 s −1 .
Poly(3,4-ethylene dioxythiophene): polystyrene sulfonate (PEDOT: PSS) zirconium(IV) phosphate (Zr... more Poly(3,4-ethylene dioxythiophene): polystyrene sulfonate (PEDOT: PSS) zirconium(IV) phosphate (ZrP) based ionomeric membrane was prepared by a solution-casting method. Subsequently, aniline polymerization was carried out on the surface of the membrane by oxidative chemical polymerization. It was characterized by thermogravimetric analysis/differential thermal analysis/differential thermogravimetry (TGA/DTA/DTG), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis, and Fourier-transform infrared (FTIR) spectroscopy. e membrane was also characterized by ion-exchange properties. e tip displacement investigation of the ionomeric membrane was also carried out. e outcomes demonstrated that the manufactured ionomeric membrane could produce generative strengths (tip powers), and consequently create good displacement. In this manner, the proposed ionomeric membrane was found proper for bending movement actuator that will give a successful and promising stage for smaller-scale mechanical applications.
Herein, we have investigated the interaction of bovine serum albumin (BSA), the most abundant glo... more Herein, we have investigated the interaction of bovine serum albumin (BSA), the most abundant globular protein, with a conventional cationic surfactant, cetyldimethylethylammonium bromide (CDMEAB), through a conductivity technique in the absence/presence of electrolyte solutions at various temperatures (298.15-323.15 K). The interaction of the protein with drugs/surfactants and other additives plays a crucial role in the body. Hence, the main concern of the study is to extract the impact of BSA on surfactant molecules and vice versa. From the specific conductivity versus concentration of surfactant plots, three different noticeable critical micelle concentration (c*) values were obtained for pure CDMEAB and its mixture with protein/protein + salts. The presence of BSA and electrolytes altered the c* values of CDMEAB revealing interactions among the studied constituents where the salt solutions reduced the c* values and created a convenient environment for favorable micellization. The negative magnitudes achieved for standard free energy changes (DG 0 m) suggest spontaneity of micellization while the values of DH 0 m and DS 0 m signified the existence of some electrostatic and hydrophobic interactions. The values of molar heat capacity (DC 0 m) were positive as well as small which was an indication of less structural deformation. Molecular Dynamics (MD) simulation for all atoms revealed that the salt ions promoted non-covalent interaction between BSA and CDMEAB, and such interactions were not observed in the absence of the salt. Protein structure remained nearly same in spite of strong interaction with CDMEAB as evident from the overall RMSD (root-mean-square deviation) values of the alpha carbons and backbone of the protein and RMSF (root-mean-square fluctuation) values of the amino acid residues present in BSA. In this work thermodynamic parameters of transfer (such as DG 0 m.tr. , DH 0 m.tr. , and DC 0 p.m.tr.) were also evaluated and the results are discussed in detail. Besides, contributions of enthalpy and entropy to free energy changes were also analyzed.
(2019) Facile synthesis of 1-(arylimino)naphthalen-2(1H)-ones from anilines and 2-naphthols promo... more (2019) Facile synthesis of 1-(arylimino)naphthalen-2(1H)-ones from anilines and 2-naphthols promoted by NaBr/ K 2 S 2 O 8 /CAN, Synthetic Communications, 49:5, 704-714,
Two carboxylate esters (methyl: (I) and ethyl: (II)) of 4-{(4-methylphenylsulfonamido)-methyl}cyc... more Two carboxylate esters (methyl: (I) and ethyl: (II)) of 4-{(4-methylphenylsulfonamido)-methyl}cyclo-hexanecarboxylic acid (sulfonamide) were synthesized and characterized by FTIR and X-ray crystallography. DFT studies were conducted in order to optimize the structures using Gaussian software which confirmed the bond angels and bond lengths obtained from single crystal analysis. Both Compounds (I and II) were evaluated for their biological studies viz; antioxidant activity (DPPH), enzyme inhibition activity (esterase and proteases), antibacterial (Halomonas halophila, Halomonas salina, Shigella sonnei, Bacillus subtilis, Chromohalobacter salexigens, Chromohalobacter israelensis, Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae) and anti-fungal (Aspergillus niger and Alternaria alternata). Results depicted that II is more active as compared to I in antioxidant and esterases while I is more potent against protease while moderate results were shown by both.
An elegant Z-scheme-fashioned photoanode consisting of Fe 2 O 3 nanorod arrays and underlying thi... more An elegant Z-scheme-fashioned photoanode consisting of Fe 2 O 3 nanorod arrays and underlying thin Sb 2 Se 3 layers was rationally constructed. The photocurrent density of the Sb 2 Se 3-Fe 2 O 3 Z-scheme photoanode reached 3.07 mA cm −2 at 1.23 V vs. RHE, three times higher than that of pristine Fe 2 O 3 at 1.03 mA cm −2. An obvious cathodic shift of the photocurrent onset potential of about 200 mV was also observed. The transient photovoltage response demonstrates that the suitable band edges (E CB ∼ −0.4 eV and E VB ∼ 0.8 eV) of Sb 2 Se 3 , match well with Fe 2 O 3 (E CB ∼ 0.29 eV and E VB ∼ 2.65 eV), permitting the photoexcited electrons on the conduction band of the Fe 2 O 3 to transfer to the valence band of Sb 2 Se 3 , and recombine with the holes therein, thus allowing a high concentration of holes to collect in the Fe 2 O 3 for water oxidation. The transient absorption spectra further corroborate that the built-in electric field in the p-n heterojunction leads to a more effective separation and a longer lifetime of the charge carriers.
The synthesis of NH 3 is mainly dominated by the traditional energy-consuming Haber−Bosch process... more The synthesis of NH 3 is mainly dominated by the traditional energy-consuming Haber−Bosch process with a mass of CO 2 emission. Electrochemical conversion of N 2 to NH 3 emerges as a carbon-free process for the sustainable artificial N 2 reduction reaction (NRR), but requires an efficient and stable electrocatalyst. Here, we report that the Mo 2 C nanorod serves as an excellent NRR electrocatalyst for artificial N 2 fixation to NH 3 with strong durability and acceptable selectivity under ambient conditions. Such a catalyst shows a high Faradaic efficiency of 8.13% and NH 3 yield of 95.1 μg h −1 mg −1 cat at −0.3 V in 0.1 M HCl, surpassing the majority of reported electrochemical conversion NRR catalysts. Density functional theory calculation was carried out to gain further insight into the catalytic mechanism involved. A s a necessary industrial chemical, NH 3 has been employed in medication, fertilizer, fuel, and explosives, etc. 1−5 Today, ever-increasing NH 3 consumption stimulates intensive research on artificial N 2 fixation technology. 6−10 However, industrial-scale NH 3 production mainly depends on the Haber−Bosch process, which is performed under rigorous conditions (350−550°C and 150−350 atm) with rather high energy consumption and CO 2 emission. 11,12 Therefore, it is urgently desired to develop an energy-saving and environmentally benign technological process for NH 3 production. Electrochemical reduction has emerged as a promising method for artificial N 2 fixation under ambient conditions. 13 However, the N 2 reduction reaction (NRR) process needs to break a rather inert molecular structure of N 2 with extremely high bond energy of about 941 kJ mol −1. 6 Thus, electro-catalysts with high activity for the NRR are a prerequisite. 13−15 In nature, N 2 fixation can be catalyzed under ambient conditions by Mo-dependent nitrogenases, via multiple proton and electron transfer steps. 16−18 Mo has also emerged as an interesting metal for homogeneous N 2 functionalization reactions, and some Mo-based molecular complexes have been designed 19,20 and synthesized for artificial N 2 fixa-tion. 21−24 However, other than stability of these catalysts, it is also challenging to effectively graft such catalysts onto electrodes for electrochemical tests and applications. Therefore , it is highly pressing to develop Mo-based heterogeneous electrocatalysts to solve these problems. Recently, (110)-oriented Mo nanofilm was reported for N 2 reduction electrocatalysis with only a Faradaic efficiency (FE) of 0.72%. 25 Our recent studies suggest that MoS 2 , 26 MoO 3 , 27 MoN, 28 and Mo 2 N 29 are effective for the NRR process with Faradaic efficiencies of 1.17%, 1.9%, 1.15%, and 4.5%, respectively. As such, to develop new Mo-based electro-catalysts for the NRR with improved activity is highly desired. Here, we present our recent study in developing the Mo 2 C nanorod as a superb NRR catalyst for artificial N 2 fixation to NH 3 with strong electrochemical durability and acceptable selectivity under ambient conditions. Such Mo 2 C achieves an FE as high as 8.13% with NH 3 yield of 95.1 μg h −1 mg −1 cat at
Magnesium titanate (MgTiO 3) has been successfully synthesized via the sonochemical method by usi... more Magnesium titanate (MgTiO 3) has been successfully synthesized via the sonochemical method by using TiO 2 (P25) and Magnesium nitrate (MgNO 3) 2 .6H 2 O as precursors without any additional phases such as MgTi 2 O 5 and Mg 2 TiO 4. The synthesized nanoparticles were well characterized by optical methods using UV-Vis diffuse reflectance spectroscopy (DRS) and Photo-luminescence spectroscopy (PL). The morphology of MgTiO 3 nanoparticles is irregular in shape with serious agglomerations were confirmed through SEM analysis. XRD confirms crystal structure and phase purity of MgTiO 3 nanoparticles calcined at 700°C for 2 hours. The calculated band gap energy of MgTiO 3 nanoparticles has been found to be 3.05 eV. Using the prepared MgTiO 3 nanoparticles, the photocatalytic activities were evaluated by following the degradation of Congo red dye under visible light. Moreover, the influence of various scavengers on the photocatalytic reaction were studied.
Photocatalytic hydrogen production from water is a promising strategy for the direct conversion o... more Photocatalytic hydrogen production from water is a promising strategy for the direct conversion of sunlight into chemical energy, which is considered as a long-term and sustainable solution to address worldwide energy and environmental issues. Herein, we develop carbon doped boron nitride (BCN) as metal-free photocatalysts by using solid-gas reaction and molecular design method of boron source. Four kinds of boron carbon nitride (BCN) were synthesized through mixed glucoses with melamine phosphate borate (MPB), melamine borate (MB), boric acid (BA) and boron oxide (BO), respectively. It can be found that the morphology of BCN-MPB (nanosheets) is different from bulk BCN-MB, bulk BCN-BA and bulk BCN-BO. The BCN-MPB nanosheets show much higher specific surface area, the longer lifetime of photoexcited charge carriers, and the stronger electron transport ability compared to those of bulk BCN. Thus, BCN-MPB nanosheets exhibit significantly improved photocatalytic hydrogen activities under visible light illumination compared to those of bulk BCN. Our work represents a facile and template-free synthesis strategy for the rational design of eco-friendly, stable and inexpensive photo-catalysts, and paves new pathways for tuning their photoreactivity in sustainable light-to-energy conversion.
A R T I C L E I N F O Keywords: PAni-SiO 2 nanocomposites 1,4-dioxane chemical sensor Electrochem... more A R T I C L E I N F O Keywords: PAni-SiO 2 nanocomposites 1,4-dioxane chemical sensor Electrochemical method Glassy carbon electrode Environmental safety A B S T R A C T In this study, conducting polyaniline (PAni) and silicon dioxide (SiO 2) nanocomposites (NCs) were synthesized for chemical sensing applications by microwave assisted reaction technique. Facile synthesis and characterization of the PAni-SiO 2 nanocomposites were investigated in details and discussed in this report. For the potential application, 1,4-dioxane chemical sensor was fabricated with the PAni-SiO 2 nanocomposites deposited onto glassy carbon electrode (GCE). A very thin uniform film was deposited onto GCE with nanocomposite by using conducting 5% nafion binder at room conditions. To evaluate the sensor analytical performances, a calibration plot such as current versus concentration of 1,4-dioxane was drawn and calculated the analytical parameters from the slope of calibration curve. Results are found as sensitivity (0.5934 µAµmol-1 L −2 cm −2), detection limit (16.0 ± 0.8 pmol L −1), and quantification limit (LOQ; 53.3 ± 1.5 pmol L −1) in this observation. Considering the linear region in calibration plot, the linear dynamic range of 1,4-dioxane chemical sensor was found (0.12 nmol L −1 ∼ 1.2 mmol L −1). Besides this, the proposed 1,4-dioxane chemical sensor was exhibited good reproducibility, long-term stability, high accuracy in detecting of 1,4-dioxane in real environmental samples. This research is to develop of a selective and an efficient electrochemical sensor. It might be a simple and easy way by applying electrochemical method to ensure the safe and sustainable green environment.
This study focuses on the preparation of nanostructured holmium oxide via the decomposition of ho... more This study focuses on the preparation of nanostructured holmium oxide via the decomposition of hol-mium acetate precursor utilizing the non-isothermal strategy. Thermogravimetric analysis (TGA) was used to follow up the various thermal events involved in the decomposition process. Dehydration completes approximately at 150 C, which is followed by the decomposition of the anhydrous acetate leading to the formation of holmium oxide. Based on the TGA results the acetate precursor was heated non-isothermally at the temperature range of 150e700 C. The obtained solids were characterized using powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). It is found that nanocrystalline Ho 2 O 3 starts to form at 500 C and presents the only phase detected at the 500e700 C range. The electrical conductivity of the solids that form at the temperature range of 300e700 C was investigated. The obtained values were correlated with the observed structural modifications accompanying the heat treatment. The electrical conductivity of the Ho 2 O 3 samples prepared at 500, 600 and 700 C reaches the values of 1.92 Â 10 À7 , 1.61 Â 10 À7 and 8.33 Â 10 À8 U À1 $cm À1 at a measuring temperature of 500 C, respectively. These values are potentially advantageous for high-resistivity devices.
In order to investigate the immobilization ways of uranium (U(VI)) on Kocuria sp., we investigate... more In order to investigate the immobilization ways of uranium (U(VI)) on Kocuria sp., we investigated the interaction behavior under different conditions by batch experiment. U(VI) products on Kocuria sp. were characterized by SEM, XRD, FTIR, and XPS techniques. SEM-EDS results presented U(VI) mineral-like precipitation formed on the cell surface which contained high percentage of P and U elements. XPS results also confirmed the appearance of bond P-O-U. XRD results illustrated characteristic UO 2 2+ peaks after U(VI) interaction with Kocuria sp. According to FTIR analysis, in addition to PO 4 3− groups, C_O,\ \OH,\ \COOH groups might play important roles in complexa-tion with U(VI). The biomineralization process of U(VI) on Kocuria sp. required longer time than sorption process, indicating that biomineralization was induced by the biosorption process. Our findings highlight the synergistic biosorption and biomineralization process of Kocuria sp. for U(VI) immobilization, which concentrated U(VI) on the cell surface via fast biosorption by providing nucleation sites for the precipitation to insoluble minerals, while the formation of U(VI) biomineral led to the relatively permanent immobilization of U(VI), and then emphasize the important roles of phosphate which are of significance in predicting the U(VI) immobilization properties.
Herein, the cloud-point (CP) measurements of a nonionic surface-active agent named Tween 80 [poly... more Herein, the cloud-point (CP) measurements of a nonionic surface-active agent named Tween 80 [poly(oxyethylene) (20) sorbitanmonooleate; Tw 80] were carried out in this study in the absence and attendance of an amikacin sulfate (AS) drug/(AS+ inorganic electrolyte (NaCl, NaNO 3 and Na 2 SO 4)). AS drug has been utilized to treat or prevent a wide range of bacterial infections. The measured values of CP in the aqueous phase for Tw 80 were observed in decreasing fashion with an increase in the concentration of surfactant. The obtained values of CP for Tw 80 solution were also noticed to decrease with increasing drug concentration. The determined CP values for (surfactant + drug) mixture were observed to decrease for the electrolytes' participation with respect to their nonparticipation, and the presence of electrolytes (sodium salts) in declining CP measurement was recorded and followed the order NaCl > NaNO 3 > Na 2 SO 4. The ΔG c 0 values are found to be positive that denotes the character of clouding is nonspontaneous. The ΔH c 0 and ΔS c 0 calculations were shown to be negative for the system studied except for the (Tw 80 + H 2 O) phase. The negative values of ΔH c 0 and ΔS c 0 decreased with the increment of electrolyte concentration. The thermodynamic parameters of transfer for the studied system were also evaluated and are illustrated in detail.
FeS 2 /carbon nanotube (CNT) nanocomposites were synthesized and immobilized on the surface of a ... more FeS 2 /carbon nanotube (CNT) nanocomposites were synthesized and immobilized on the surface of a glassy carbon electrode (GCE) in order to investigate the electrocatalytic conversion of 4-aminophenol (4-AP) into p-quinone in an aqueous medium. The reformed electronic properties (in terms of lowering of band-gap energy and charge-transfer resistance), as well as improved surface area, result in an enhanced redox reaction of 4-AP in the presence of FeS 2-CNT NCs compared to that with FeS 2 alone. The 4-AP molecules undergo coupled two-proton and two-electron transfer quasi-reversible redox reactions with a symmetry factor of 0.55 and standard rate constant (k°) of 0.8 cm s À 1. Here, quinone imine is generated as an intermediate which is later converted into quinone in an irreversible hydrolysis reaction. The best catalytic performance can be obtained at the pH value of 7.0.
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A2019 by Abdullah M. Asiri