Negative Gibbs Free Energy Research Articles

As(V) removal using biochar produced from an agricultural waste and prediction of removal efficiency using multiple regression analysis.

Arsenic contamination in drinking water is a matter of concern for many countries. An efficient and low-cost solution for this hazard is essentially needed on urgent basis. Therefore, in this study, banana pith (an agricultural waste) was used for biochar production and later it was modified with iron and applied for arsenic adsorption from aqueous solution. Produced biochar was characterized for proximate, ultimate, and surface analyses. Interestingly, after iron impregnation, the surface area of biochar increased (31.59 m2/g) by nearly 8 times. Morphological analysis showed that iron particles firmly held within the pores after impregnation. Arsenate (As(V)) adsorption behavior of iron-impregnated banana pith biochar was evaluated through a batch study by considering various parameters like dose, concentration, pH, temperature, and competing anions. Compared to impregnated biochar, raw biomass and its biochar showed a lesser affinity for arsenate in aqueous solution. The adsorption isotherm of As(V) on banana pith biochar was covered in the temperature range of 298 to 318 K, and kinetic data of adsorption was experimentally generated at 298 K. Langmuir model for the sorption isotherms and pseudo-second-order kinetic model for the sorption kinetics represented the experimental data. The thermodynamic study showed negative Gibb's free energy (- 46.88 kJ/mol at 298 K, - 48.58 kJ/mol at 308 K, - 50.73 kJ/mol at 318 K) that suggested spontaneity of the adsorption process. Negative enthalpy (ΔH° = - 10.55 kJ/mol) showed exothermic nature of adsorption of arsenic, while negative entropy (ΔS° = 0.123 kJ/mol.K) suggested enthalpy-driven adsorption process. Mechanism of arsenic adsorption onto iron-impregnated banana pith biochar has also been discussed in detail. Based on the experimental observation, a predictive model for arsenate removal has been developed in this study. The findings of the present study elucidated that iron-impregnated banana pith biochar can be used as a low-cost adsorbing material for As(V) from aqueous solutions.

Change of Electrical Properties of Rutile- and Anatase-TiO2 Films by Atomic Layer Deposited Al2O3

Introduction Titanium dioxide (TiO2) has been widely investigated as a channel layer for oxide thin film transistors (oxide-TFTs) and an active layer of resistive random access memory [1]. TiO2 is a very attractive because high dilectric constant (k) of anatase and rutile phases are ~30 and ~80, respectively, and easily converted from an insulator to a semiconductor and conductor due to the electrons generated by formation of oxygen vacancies (Vo). TiO2 semiconductor was studied as a channel material for oxide-TFTs because of its relatively high electron mobility of 10 cm2V-1s-1 [2]. However, the semiconductor region is very narrow and Vo formation must be controlled carefully because poor and excess Vo concentrations lead to insulator and conductor regions, respectively. Recently, MOSFETs with high-mobility InGaAs channels have exhibited good performance when native oxides (GaOx and AsOx), which caused Fermi-level pinning, were removed from the channel. The native oxides were removed during Al2O3 deposition using atomic layer deposition (ALD) with trimethylaluminum (TMA) precursor and H2O oxidant gas. Furthermore, the formation of a two-dimensional electron gas (2-DEG) in Al-based amorphous oxide/SrTiO3 heterostructures was reported to be grown by ALD using TMA and H2O gases, based on a similar mechanism of oxygen removal from the Ti-O layer of a SrTiO3 single crystal [3]. Here, we have an iteresting about how the ALD process with TMA and H2O affect to characteristics of rutile- and anatase-TiO2 films as channel metaerial for oxide-TFT. In this paper, we deposited an Al2O3 layer on polycrystalline rutile- and anatase-TiO2 films by ALD with TMA and H2O, and examined its electrical properties, including its resistivity, Hall mobility (m Hall), and carrier density (n). Experiment First, a 10-nm-thick TiO2 film was deposited on a 100-nm SiO2/p-Si substrate by ALD at 200°C using a Ti[N(CH3)2]4 precursor and H2O oxidant gas. The as-grown TiO2 film had an amorphous structure, and rutile- and anatase-phases were formed by post-deposition annealing (PDA) of the films at 800°C in N2 and 500°C in O2 atomosphere, respectively. Next, the TMA precursor and H2O oxidant gases were alternately supplied, as in an ALD Al2O3 deposition at 300°C. The number of ALD cycles was varied over the ranges of 0–50 cycles. The electrical properties of rutile- and anatase-TiO2 films were investigated by Hall measurement with the van der Pauw method at room temperature. For Hall measurement, Au (100 nm)/Ti (10 nm) electrodes were deposited in 4 places of the samples with a single TiO2 or TiO2/Al2O3 stack structure by thermal evaporation. Results and discussion Initially, the rutile- and anatase-TiO2 films were an insulator, but its resistivity dropped dramatically to 10-1–10-2 Wcm and stayed low after 5 ALD cycles. The n values of both samples were 1019–1020 cm-3 in the low-resistivity region. The m Hall values were 1–6 cm2V-1s-1, which correspond well with the literature values of 0.2–6 and 10 cm2V-1s-1 for thin-film and single-crystal anatase-TiO2, respectively. These m Hall values are also similar to values for 2DEG of LaAlO3/SrTiO3 heterostructures (4–5 cm2V-1s-1) [3] and InOx-based oxide semiconductors (~10 cm2V-1s-1) [4]. Therefore, we found that rutile- and anatase-TiO2 films could be easily converted from an insulator to a conductor after ALD Al2O3 deposition. Here, we considered the mechanism that generated an electron carrier in rutile- and anatase-TiO2 films under the ALD Al2O3 deposition. In an initial step of ALD process, when a TMA molecule is absorbed on the surface of the TiO2 film, the reaction of the –CH3 ligand of TMA and oxygen of TiO2 forms Al2O3 because of the negative Gibbs free energy. As a result, a Vo is formed, and electrons are generated in the TiO2 film. Summary We conclude that electrical properties dramatically changed as the number of ALD cycles increased above 5 cycles. The resistivity, n, and m Hall of the TiO2 films were 10-1–10-2 Wcm, 1019–1020 cm-3, and 1–6 cm2V-1s-1, regardless of rutile and anatase phase structures. Acknowledgement The authors thank all staff members of the Nanofabrication group of the National Institute for Materials Science (NIMS) for their support.

Kinetic and Thermodynamic Investigation of Human Serum Albumin Interaction with Anticancer Glycine Derivative of Platinum Complex by Using Spectroscopic Methods and Molecular Docking

In this paper, a new anticancer Pt (II) complex, cis-[Pt (NH3)2(tertpentylgly)]NO3, was synthesized with glycine-derivative ligand and characterized. Cytotoxicity of this water-soluble Pt complex was studied against human cancer breast cell line of MCF-7. The interaction of human serum albumin (HSA) with Pt complex was studied by using UV-Vis, fluorescence spectroscopy methods, and molecular docking at 27 and 37°C in the physiological situation (I = 10mM, pH = 7.4). The negative [Formula: see text] and positive [Formula: see text] indicated that electrostatic force may be a major mode in the binding between Pt complex and HSA. Binding constant values were obtained through UV-Vis and fluorescence spectroscopy that reveal strong interaction. The negative Gibbs free energy that was obtained by using the UV-Vis method offers spontaneous interaction. Fluorescence quenching the intensity of HSA by adding Pt complex confirms the static mode of interaction is effective for this binding process. Hill coefficients, nH, Hill constant, kH, complex aggregation number around HSA, <J>, number of binding sites, g, HSA melting temperature, Tm, and Stern-Volmer constant, kSV, were also obtained. The kinetics of the interaction was studied, which showed a second-order kinetic. The results of molecular docking demonstrate the position of binding of Pt complex on HSA is the site I in the subdomain IIA.

Preparation of magnetic core-shell Fe3O4@polyaniline composite material and its application in adsorption and removal of tetrabromobisphenol A and decabromodiphenyl ether

Present study described a magnetic adsorption and removal method with prepared magnetic core-shell Fe3O4@polyaniline microspheres for the removal of two typical BFRs, tetrabromobisphenol-A (TBBPA) and decabromodiphenyl ether (BDE-209) from water samples. Magnetic core-shell Fe3O4@polyaniline microspheres were prepared by a hydrothermal and two step polymerization method with cheap iron salts and aniline, which were characterized with transmission electron microscopic (TEM) and scanning electron microscopy (SEM). The results showed that the Fe3O4@polyaniline microspheres earned a clear thickness shell of polyaniline (about 50 nm) and a saturation magnetization of 40.4 emu g−1. The Magnetic core-shell Fe3O4@polyaniline exhibited excellent adsorption capability and removal rate to TBBPA and BDE 209. The adsorption of TBBPA and BDE 209 all followed pseudo-second order kinetics and agreed well to the Freundlich adsorption isotherms model. The negative Gibbs free energy change (ΔG0) and positive standard enthalpy change (ΔH0) for TBBPA and BDE-209 suggested that the adsorption was spontaneous and endothermic in nature. These results demonstrated that Fe3O4@PANI was a good adsorbent and would have a good application prospect in the removal of pollutants from environmental water.

Extending the study of mass transport across the gas-liquid interface by reversed-flow gas chromatography

The transfer of dichlorodifluoromethane to water was utilized as model system to provide better insight on the determination of mass transport parameters across the gas-liquid interface. Weak signals by reversed-flow gas chromatography were recorded at various temperatures, from 320.7 to 344.3 K, by digitizing and smoothing the output of the flame ionization detector. A flexible uncertainty analysis distinguished the main sources of error in the determined parameters, suggesting improvements on the utilized experimental setup. Liquid diffusivities decreased with rising temperature (4.39 to 1.01 × 10−10 m2 s-1), approaching literature values at lower temperatures. The estimated liquid film thicknesses similarly decreased (1.8 to 1.0 × 10-4 m) and were one order of magnitude larger than previous findings, due to the larger extent of evaporation permitted by the current experimental setup. A mass transfer coefficient was estimated, corresponding to the endothermic contribution of the reverse (liquid-to-gas) process, whose activation energy (43.4 ± 2.8 kJ mol-1) matched the vaporization enthalpy of water in the studied temperature range. Successful comparisons were made with literature distribution coefficients and Henry’s law constants. The dissolution of CFC-12 in water was found to be exothermic, slightly spontaneous at lower temperatures and approaching equilibrium at higher ones (indicated by the small negative molar Gibbs free energy values), with negative entropy change values [average: –(190.7 ± 6.9) J K-1 mol-1], as expected for a process of increased order.

Reagent adsorption on modified mineral surfaces: isotherm, kinetic and thermodynamic aspects

This study has been designed to investigate the effect of surface dissolution on the isotherm, kinetics, and thermodynamics of collector adsorption on the surface of ilmenite (IL) and its accompanied gangue minerals including olivine (Ol), pyroxene (Px), tremolite (Tr), and clinochlore (Cch). For this purpose, some laboratory techniques such as flotation experiments, adsorption tests, ICP-Mass analysis, UV–Visible spectroscopy, BET analysis, and scanning electron microscopy were employed. The flotation experiments showed that after surface dissolution, the selectivity of ilmenite flotation is improved by increasing its flotation recovery and by the decrease of gangue minerals floatabilities. As revealed by adsorption tests, this can be attributed to the more adsorption density of collector on the surface of treated ilmenite and its reduction on the modified surface of olivine-pyroxene (Ol-Px) and tremolite-clinochlore (Tr-Cch) having less surface active cations (Fe2+, Ca2+, and Mg2+) after surface modification by oxalic acid. Also, the equilibrium data analysis indicated that the Langmuir model is the most appropriate model to describe the adsorption of sodium oleate as a collector on the surface of studied minerals. The kinetics studies showed that unlike the gangue minerals, the adsorption kinetics of collector on the surface of modified ilmenite is significantly enhanced. According to the thermodynamic parameters, positive Enthalpy (ΔH), negative Gibbs free energy (ΔG), and positive Entropy (ΔS) were found for the collector adsorption process before and after treatment, showing the endothermic, spontaneous and more favorable nature of adsorption reaction at high temperatures. Also, the surface dissolution changes the ΔG and ΔS of ilmenite into the more negative and positive values, respectively, while it changes these thermodynamic parameters inversely for both gangue phase samples.

Adsorption Characteristic of Cr(VI) onto Different Activated Coal Fly Ashes: Kinetics, Thermodynamic, Application Feasibility, and Error Analysis

Raw coal fly ash (RCFA) was recycled as three kinds of adsorbents by hydroxyl anion (OH−), hydrogen ion (H+), and thermal activation, respectively, for the adsorption of Cr(VI) from water. The H+ activation can explore the adsorptive potential of RCFA more effectively than the other two methods. The specific surface areas of the adsorbents are 12.33, 16.32, and 13.89 m2 g−1 for OH−, H+, and thermal activation, respectively. The adsorption process follows the pseudo-second-order kinetic model and the Langmuir model better and exhibits exothermic property. The activation energy (20.65–31.88 kJ mol−1) and the negative Gibbs free energy reveal that the adsorption is a physical and spontaneous process. The adsorbents derived from OH−, H+, and thermal activation can be used at least 5, 7, and 4 times, respectively, while the one from H+ activation has the best adsorption capacity (6.41 μg g−1 for the first run). The adsorption process can introduce other metallic/toxic elements, but within the Chinese standard. The preparation cost of the H+ activation is $1103 ton−1 adsorbent, while the treatment cost is $1.6 ton−1 water. The more accurate parameters in the pseudo-second-order kinetic model and Langmuir model can be calculated by nonlinear method and provided by the error function of the sum of the squares of the errors.

Host-guest interactions between p-sulfonatocalix[4]arene and p-sulfonatothiacalix[4]arene and group IA, IIA and f-block metal cations: a DFT/SMD study.

The molecular recognition in aqueous solution is extremely important because most biological processes occur in aqueous solution. Water-soluble members of the calix[n]arene family (e.g., p-sulfonato substituted) can serve as model systems for studying the nature and manner of interactions between biological receptors and small ions. The complex formation behavior of water-soluble p-sulfonatocalix[4]arene and thiacalix[4]arene and group IA, IIA and f-block metal cations has been investigated computationally by means of density functional theory computations in the gas phase and in aqueous environment. The calculated Gibbs free energy values of the complex formation reaction of these ligands with the bare metal cations suggest a spontaneous and energy-favorable process for all metal cations in the gas phase and only for Na+, Mg2+, Lu3+ cations in water environment. For one of the studied cations (La3+) a supramolecular approach with explicit solvent treatment has been applied in the study of the effect of metal hydration on the complexation process. The La3+ binding to the p-sulfonatocalix[4]arene host molecule (now in the metal’s second coordination shell) is still exergonic as evidenced by the negative Gibbs free energy values (ΔG1 and ΔG78). The combination of implicit/explicit solvent treatment seems useful in the modeling of the p-sulfonatocalix[4]arene (and thiacalix[4]arene) complexes with metal cations and in the prediction of the thermodynamic parameters of the complex formation reactions.

Effect of Brij 35 and saponin surfactants on adsorption of diethylstilbestrol as anemerging estrogenic contaminant by clinoptilolite in batch and fixed-bed columnexperiments

In this study, natural clinoptilolite was modified by saponin and Brij 35 surfactants to remove diethylstilbestrol (DES) from wastewater in batch and continuous systems. The optimum pH, amount of adsorbent, contact time, and temperature were 11, 10 g/L, 12 h, and 35 °C, respectively, for the process. The equilibrium data agreed well with the Langmuir isotherm for natural clinoptilolite (NC), natural clinoptilolite modified by Brij 35 (NC-Brij), and natural clinoptilolite modified by saponin surfactants (NC-saponin) compared to other isotherms. The maximum adsorption capacities resulting from the Langmuir isotherm for NC, NC-Brij, and NC-saponin were 8.012, 23.64, and 39.525 mg/g, respectively. Fixed-bed column experiments were performed under various operational conditions to evaluate the performance of the adsorbent bed breakthrough curve. The lumped method solves bed equations to determine the axial dispersion coefficient (Dz) and overall mass transfer coefficient (Koverall) parameters. Comparison of the kinetic models indicated that the DES adsorption process was well described by the intraparticle diffusion model for NC, pseudo-second-order and fractional power kinetic models for NC-Brij, and pseudo-second-order model for NC-saponin. The negative Gibbs free energy and positive enthalpy changes for NC, NC-Brij, and NC-saponin confirmed that the removal reaction of DES was spontaneous and the adsorption was endothermic, respectively.

The effect of Pseudomonas fluorescens biosurfactant pseudofactin II on the conformational changes of bovine serum albumin: Pharmaceutical and biomedical applications

Herein, we have investigated the binding interaction of bovine serum albumin (BSA) with a biosurfactant pseudofactin II (PF) in physiological buffer medium through the use of surface tension, fluorescence, circular dichroism (CD), isothermal titration calorimetry (ITC) and molecular docking studies. Fluorescence results showed that PF interacts with BSA through a static quenching mechanism. CD results demonstrate a conformational change in BSA upon PF combination. The negative Gibbs free energies obtained through ITC experiment suggest that the binding process is spontaneous. Molecular docking further provides an insight of various residues that are involved in this binding process, showing a binding energy of −58.6 kcal mol−1. The present study will help understand the binding mechanism of lipopeptide biosurfactant (PF) to proteins as well as the associated stability and conformational changes.

Adsorptive removal of apramycin antibiotic from aqueous solutions using Tween 80-and Triton X-100 modified clinoptilolite: experimental and fixed-bed modeling investigations

ABSTRACT This study examined the performance of natural clinoptilolite (NC) modified with two surfactants of Triton X-100 (NC-Triton) and Tween 80 (NC-Tween) on apramycin (APR) adsorption from wastewater in batch and continues systems. The optimum pH, contact time, adsorbent dosage, and temperature were achieved. The findings revealed that the sorption was best described using the Langmuir isotherm compared to other isotherms. The maximum adsorption capacity of NC-Triton was greater than NC and NC-Tween. The lumped method was applied to solve the fixed-bed equations; predict breakthrough curve; determine axial dispersion coefficient and overall mass transfer coefficient parameters; and compare theoretical results with experimental results. Good fitness of experimental data with kinetic models of intra-particle diffusion, pseudo-first-order/liquid film diffusion and pseudo-second-order for NC, NC-Tween and NC-Triton, respectively, indicated that they were more suitable than the other models. Endothermic and spontaneous processes were resulted from positive enthalpy and negative Gibbs free energy changes, respectively.

Gibbs free energy [formula omitted] analysis for the Na[sbnd]O[sbnd]H (sodium-oxygen-hydrogen) thermochemical water splitting cycle

The main aim of the paper is to determine a theoretical range of operational conditions for the three chemical reactions of the NaOH (sodium-oxygen-hydrogen) thermochemical water splitting cycle by performing a Gibbs free energy (ΔG) analysis. ΔG is a thermodynamic parameter that allows determining if a chemical reaction is able to occur due to its enthalpy (ΔH) and entropy (ΔS) changes under specific conditions of pressure (p) and temperature (T). The methodology consists of implementing in Engineering Equation Solver (EES) software equations related to ΔH and ΔS for the three chemical reactions of the NaOH process, considering specific conditions of p and T with proper thermodynamic data to calculate ΔG. The main obtained results are: reaction 1, hydrogen production step, has ΔG < 0 for any values of T and p considered in the study; it can be performed at 100 °C under 1 bar; reaction 2, metal separation step, only can proceed under vacuum atmosphere at around 500 °C; reaction 3, hydrolysis step, always has negative Gibbs free energy despite pressure and temperature values and it can be carried out under 1 bar at 25 °C. Moreover, the methodology described in this paper could be used to investigate operational conditions for thermochemical processes.

Effective inhibition on the corrosion of X65 carbon steel in the oilfield produced water by two Schiff bases

The failure of carbon steel pipelines due to corrosion is a serious problem in the oil and gas exploitation. In this study, two new Schiff bases, 5-((3-phenylallylidene)amino)-1,3,4-thiadiazole-2-thiol (PATT) and 5-((thiophen-2-ylmethylene)amino)-1,3,4-thiadiazole-2-thiol (TATT), were synthesized as inhibitors to inhibit the corrosion of X65 carbon steel in the CO2-saturated oilfield produced water. Electrochemical measurements and surface analysis show that both PATT and TATT exhibit significant inhibition effect by predominant inhibition of anodic process. The considerable negative standard Gibbs free energy indicates that the adsorptions of PATT and TATT are primarily chemisorption. Molecular dynamics simulations show that both PATT and TATT adsorb on Fe surface in flat orientation. PATT exhibits a higher inhibition effect than TATT, which has been demonstrated by experimental measurements and theoretical calculations.

Experimental, kinetic, and thermodynamic studies of adsorptive desulfurization and denitrogenation of model fuels using novel mesoporous materials.

The kinetics, equilibrium and thermodynamics studies of adsorptive desulfurization and denitrogenation to eliminate the refractory sulfur and nitrogen compounds like BT, DBT, quinoline and carbazole of model fuel by mesoporous material (MSU-S) and cobalt modified mesoporous material (CoO-MSU-S) adsorbents were carried out. The adsorption performance, capacity and selectivity of the adsorbent toward sulfur and nitrogen compounds were examined. Equilibrium and kinetics experiments confirmed that Co+2 impregnation would enhance the adsorption capacity of MSU-S. The results demonstrated that CoO-MSU-S led to a considerable improvement in the adsorption performance. The adsorption amounts reached 18.41, 21.20, 39.65 and 24.60 mg.g-1 for BT, DBT, quinoline and carbazole, respectively. The Langmuir isotherm model showed good fittings with the experimental equilibrium data for benzothiophene, dibenzothiophene and carbazole, and the data for quinoline was expressed well by the Freundlich for CoO-MSU-S adsorbent. Negative Gibbs free energy showed that all sulfur and nitrogen compounds were adsorbed spontaneously. The experimental data revealed that the pseudo-second-order model can describe the kinetics of adsorption of compounds on the adsorbent. The data obtained from the breakthrough curves indicated that DBT < BT < carbazole < quinoline order for the selectivity of modified adsorbent towards the adsorbates.

Integrated multi-spectroscopic and molecular modelling techniques to probe the interaction mechanism between salvianolic acid A and α‑glucosidase.

α-Glucosidase (AG) is an important drug target for the treatment of type 2 diabetes mellitus in humans due to the potential effect of down regulating glucose absorption in patients. In our previous study, salvianolic acid A (SAA) was found to exhibit potent AG inhibitory activity, whereas the interaction mechanism was still ambiguous. Herein, the interaction mechanism of SAA and AG was investigated by multi-spectroscopic methods along with molecular docking. As a result, it was found that SAA reversibly inhibited AG in a competitive manner with IC50 of 16.44 ± 0.18 μM, and the inhibition belonged to a multi-phase kinetics process with a first-order reaction. The intrinsic fluorescence of AG could be strongly quenched by SAA through a static quenching mechanism. The negative Gibbs free energy change and positive values of enthalpy and entropy change revealed that the binding of SAA to AG was spontaneous and dominated mainly by hydrophobic interactions, and only a single binding site was determined for them. Analysis of synchronous fluorescence, ANS-binding fluorescence, circular dichroism and Fourier transform infrared spectra suggested that the binding of SAA to AG induced rearrangement and conformational changes of the enzyme. Besides, further molecular modelling validated that SAA could bind to the active domain and prevent the entrance of substrate, resulting in the inhibition of AG activity. These findings provide new insights into understanding the interaction mechanism of SAA on AG.

Computational MitoTarget Scanning Based on Topological Vacancies of Single-Walled Carbon Nanotubes with the Human Mitochondrial Voltage-Dependent Anion Channel (hVDAC1).

We present an in silico approach for modeling the noncovalent interactions between the human mitochondrial voltage-dependent anion channel (hVDAC1) and a family of single-walled carbon nanotubes (SWCNTs) with a defined pattern of topological vacancies ( v = 1-16), obtained by removing atoms from the SWCNT surface. The general results showed more stable docking interaction complexes (SWCNT-hVDAC1), with more negative Gibbs free energy of binding affinity values, and a strong dependence on the vacancy number ( R2 = 0.93) and vacancy formation energy ( R2 = 0.96). In addition, for most of the SWCNT vacancies that were analyzed, the interatomic distances for the interactions of the SWCNT-hVDAC1 complex with the functional catalytic residues (i.e., Pro7, Gln199, Gln182, Phe181, Val20, Asp19, Lys15, Gly14, Asp12, Ala11, and Arg18) that form the hVDAC1 active site (i.e., the voltage-sensing N-terminal α-helix segment) were very similar to or shorter than the interatomic distances of these residues for ATP-hVDAC1 interactions. In particular, the hVDAC1 residues that can be phosphorylated like Tyr10, Tyr198, and Se16 were significantly perturbed by the interactions with SWCNT with at least nine vacancies. In addition, the SWCNT vacancy family members can affect the flexibility properties of the hVDAC1 N-terminal α-helix segment inducing different patterns of local perturbations in inter-residue communication. Finally, vacancy quantitative structure-binding relationships (V-QSBRs) were unveiled for setting up a robust model that can predict the strength of docking interactions between SWCNTs with a specific topological vacancy and hVDAC1. The developed V-QSBR model classified properly all of the SWCNTs with a different number of SWCNT vacancies with exceptional sensitivity and specificity (both equal to 100%), indicating a strong potential to unequivocally predict the influence of SWCNT vacancies on the mitochondrial channel interactions.

Removal of toxic dyes from aqueous solution by adsorption onto highly recyclable xGnP® graphite nanoplatelets

The adsorptive capacity of xGnP® graphite nanoplatelets (GNP) was evaluated for the removal of Drimaren Dark Blue CL-R (DDB), Direct Red 80 (DR80), Chrysophenine (CH) and Eosin Yellowish (EY). Kinetic pseudo-second-order (PSO) model best fitted the experimental data for all evaluated dyes. Moreover, sorption capacity at equilibrium state for DDB, DR80, CH and EY were 22.14, 38.36, 28.68 and 156.77 mg g−1, respectively. Equilibrium data for the DDB dye were best fitted to the BET type IV model, while DR80, CH and EY dyes were adjusted by BET Type II. From these models, it was achieved the following maximum monolayer adsorption capacities: 20.51, 26.41, 39.41 and 66.00 mg.g−1 for DDB, DR80, CH and EY, respectively. Furthermore, investigations over the effect of pH on adsorption revealed that its behavior is governed by strong electrostatic and π−π stacking interactions. Thermodynamic studies exhibited negative values, of enthalpy and Gibbs free energy, for all dyes, indicating the spontaneous and exothermic nature of adsorption. Hence, adsorption tends to be more favorable as the temperature decreases. GNP also showed high regeneration capacity, keeping its sorption efficiency after six adsorption-desorption cycles. Dyes solutions also showed low phytotoxicity after their adsorption on GNP.

Adsorption of paraquat from water by insoluble cyclodextrin polymer crosslinked with 1,2,3,4-butanetetracarboxylic acid

An insoluble polymer was elaborated by crosslinking reaction between β-CD (β-cyclodextrin) and BTCA (1,2,3,4-butanetetracarboxylic acid) and it was firstly applied in adsorption of paraquat (PQ) from water. This insoluble polymer was synthesized at 180 °C for 30 min which displayed 74.1% of reaction yield, 3.80 mmol g− 1 of ion exchange capacity (IEC) and 0.18 mmol g− 1 of β-CD content. Physicochemical properties were evaluated by attenuated total reflection–Fourier transform infrared spectroscopy (ATR-FTIR), carbon-13 nuclear magnetic resonance (13C NMR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) method and stereoscopic microscopy. The optimal pH was 8 and the equilibrium time was 120 min. At 30 °C, the adsorption capacity was enhanced (10.8, 19.7, and 25.8 mg g− 1) when the initial concentration of paraquat was increased (25, 50 and 200 mg L− 1, respectively). Adsorption kinetics was described by the pseudo-second-order model and adsorption isotherm was appropriated to the Langmuir model. The negative standard enthalpy change (∆Ho) showed an exothermic process, the positive standard entropy change (∆So) displayed an increased disorder and the negative standard Gibbs free energy change (∆Go) indicated a spontaneous adsorption method. Ultimately, the regeneration efficiency of polymer in methanol was 87.3% after four cycles. This polymer could be used as a potential adsorbent for removal of other cationic pesticides.

Unexpected SiC nanowires growth during spark plasma sintering of WC-10Si: A comparative study on phase formation and microstructure properties against WC-10Co cermet

In the present work, SiC nanowires were formed unexpectedly during spark plasma sintering of WC-10 wt%Si cermet. The microstructure, hardness, bending strength and fracture toughness of WC-10 wt%Si were compared with conventional WC-10 wt%Co. The sintering temperatures were chosen according to time-temperature-displacement curves to enhance maximum shrinkage of composites containing Si and Co at temperatures of 1850° and 1350 °C, respectively. Thermodynamic investigations showed negative Gibbs free energy of the formation of WSi2 and SiC compounds during sintering process while the positive amounts of ΔG were calculated for the possible formation of intermetallic compounds in WC-10 wt%Co composite. XRD investigations approved the formation of WSi2 and SiC compounds while the reaction between WC and Co led to the formation of η phase as expected. The microstructure observations revealed nanowire shapes of SiC particles distributed uniformly. The bending strength of 583 ± 31 MPa and fracture toughness of 6.2 MPa m1/2 were measured for WC-10 wt%Si composite, these amounts were lower compared to bending strength and fracture toughness of WC-10 wt%Co composite (1032 ± 26 MPa and 16.4 MPa m1/2, respectively). Besides, the hardness of 2147 ± 31 and 1622 ± 28 Vickers was obtained for WC-10 wt%Si and WC-10 wt%Co composites, respectively. The weak mechanical properties of WC-10 wt%Si composite were related to the presence of pores between SiC nanowires which acted as crack propagation centers.

Tunable, Multifunctional Ceramic Composites via Intercalation of Fused Graphene Boron Nitride Nanosheets.

Ternary two-dimensional (2D) materials such as fused graphene-boron nitride (GBN) nanosheets exhibit attractive physical and tunable properties far beyond their parent structures. Although these features impart several multifunctional properties in various matrices, a fundamental understanding on the nature of the interfacial interactions of these ternary 2D materials with host matrices and the role of their individual components has been elusive. Herein, we focus on intercalated GBN/ceramic composites as a model system and perform a series of density functional theory calculations to fill this knowledge gap. Propelled by more polarity and negative Gibbs free energy, our results demonstrate that GBN is more water-soluble than graphene and hexagonal boron nitride (h-BN), making it a preferred choice for slurry preparation and resultant intercalations. Further, a chief attribute of the intercalated GBN/ceramic is the formation of covalent C-O and B-O bonds between the two structures, changing the hybridization of GBN from sp2 to sp3. This change, combined with the electron release in the vicinity of the interfacial regions, leads to several nonintuitive mechanical and electrical alterations of the composite such as exhibiting higher young's modulus, strength, and ductility as well as sharp decline in the band gap. As a limiting case, though both tobermorite ceramic and h-BN are wide band gap materials, their intercalated composite becomes a p-type semiconductor, contrary to intuition. These multifunctional features, along with our fundamental electronic descriptions of the origin of property change, provide key guidelines for synthesizing next generation of multifunctional bilayer ceramics with remarkable properties on demand.