Quenched disorder of a nematic liquid crystal under a magnetic field J. Mol. Liq. (IF 4.513) Pub Date : 2018-02-15 Kostyantyn Slyusarenko, Christophe Blanc, Yuriy Reznikov, Maurizio Nobili
We report measurements and theoretical predictions on the effect of an aligning magnetic field on the orientational disorder of a nematic liquid crystal in contact with isotropic solid substrates. Different types of substrates present a similar disorder and a similar dependency on the magnetic field amplitude, i.e. a decreasing of the angular distribution widths and spatial correlation lengths. Measurements are in qualitative agreement with a theory where the orientational disorder emerges from the competition between the aligning magnetic torque and the disorienting thermal fluctuations during the adsorption of the liquid crystal molecules on the substrate.
On the way of reconstruction of the liquid crystal surface anchoring potential J. Mol. Liq. (IF 4.513) Pub Date : 2018-02-16 V.A. Belyakov, D.V. Shmeliova, S.V. Semenov
We extend further the theoretical and experimental studies of the actual surface anchoring potential reconstruction by polarization microscope technique in a wedge-shaped cell with weak surface anchoring forces filled by a chiral nematic liquid crystal (in Grandjean-Cano Wedge) and present the material for the sake of the reader convenience with a short coherent survey of our previous results. To realize the theoretically predicted options of observation of large director deviation angles from the easy axes φ at a wedge surfaces (up to π/2) the experimental studies of director distribution in Grandjean-Cano zones were performed. A weak surface anchoring at one wedge surface was obtained by photo-alignment technique. A strong surface anchoring at the second wedge surface was obtained by rubbing. The measurements were performed using polarizing microscope. The experimentally found director distributions in Grandjean-Cano zones were compared with theoretical ones calculated for various model surface anchoring potentials. As a result of the present studies the ways to enlarge (compared to the previous studies) angular range of the actual surface anchoring potential restoration were proposed and it was found that the experimentally found surface potential is nicely fitted by a new model surface anchoring potential, the so called model D-potential WD(φ)~φ2.
Dynamics of nonlinear electrophoretic motion of dielectric microparticles in nematic liquid crystal J. Mol. Liq. (IF 4.513) Pub Date : 2018-02-19 Fedor V. Podgornov, Anna V. Ryzhkova, Wolfgang Haase
The dynamics of dielectric microparticles motion in nematic liquid crystal cells with in-plane electrodes was investigated. It was found that the microparticles motion was driven by the Stokes drag and electrophoretic forces in the middle part of the electrodes gap. At low electric field strengths (E < 0.4 V/μm), the electrophoresis of microparticles is linear whereas for E > 0.4 V/μm it has nonlinear nature, due to the induced charges in electric double layers near the microparticles boundary (q~E2). Independently on the NLC alignment, this nonlinearity leads to the cubic dependence of the microparticles velocity on the electric field strength (v~E3). But, the value of nonlinear electrophoretic mobility (μ(3)) of microparticles is a function of the alignment and the parameters of NLC as well as the dielectric permittivity of the microparticles. Near the electrodes, the dielectrophoretic and the elastic trapping forces significantly influence the motion dynamics of microparticles.
High-quality alignment of nematic liquid crystals using periodic nanostructures created by nonlinear laser lithography J. Mol. Liq. (IF 4.513) Pub Date : 2018-02-20 I.A. Pavlov, A.S. Rybak, A.M. Dobrovolskiy, V.M. Kadan, I.V. Blonskiy, F.Ö. Ilday, Z.I. Kazantseva, I.A. Gvozdovskyy
Resonanсe nonlinear optical properties of dye-doped liquid crystals under pulse excitation: Insight into early experiments J. Mol. Liq. (IF 4.513) Pub Date : 2018-02-21 Eugene A. Tikhonov, Igor P. Ilchishin
The results of studies of the nonlinear optical properties of dye-doped nematic (NLCs) and cholesteric liquid crystals (CLCs) under powerful laser excitation are presented. The invariability of the structure of a planar-oriented NLC as a result of the conservation of the absorption dichroism of an impurity dye under the control over the lasing threshold is shown. A method to reduce the threshold for the stimulated Raman scattering (SRS) in the isotropic phase of NLC at frequencies that overlap with the amplification band of a dissolved dye is proposed. The peculiarities of the energy characteristics of CLC lasers are studied in detail. A variation of the lasing efficiency and the nonlinear dependence of the lasing energy on the pumping are explained within a model of lasing systems with distributed feedback. The dynamics of the optical destruction of a planar texture of a dye-doped CLC at critically high levels of laser irradiation is studied.
Spectral and quantum mechanical study of some azo-derivatives J. Mol. Liq. (IF 4.513) Pub Date : 2018-04-04 Daniela Babusca, Ana Cezarina Morosanu, Andreea Celia Benchea, Dan Gheorghe Dimitriu, Dana Ortansa Dorohoi
The system of mobile ions in lattice models: Screening effects, thermodynamic and electrophysical properties J. Mol. Liq. (IF 4.513) Pub Date : 2018-04-05 George Bokun, Dung di Caprio, Myroslav Holovko, Vyacheslav Vikhrenko
The lattice fluid model of the system with short range and long range Coulomb interactions is suggested. In the framework of the collective variables method, the screening of the Coulomb interactions in the bulk is considered. It is shown that the Debye length includes additional concentration dependence inversely proportional to the square root of the mean concentration of vacant sites like what was known at the plane boundary. The Coulomb interaction contribution to the free energy of the system is calculated in the approach close to the mean spherical approximation and is given in an analytical form.The influence of the variation of the crystal field near the system boundary on the structure and characteristics of the electric double layer is investigated. As compared to the system with equal crystal potentials at the lattice sites throughout the system the pronounced difference for the electrical capacitance appears at low absolute values of the surface potential and it is more pronounced for negative electric potentials. The capacitance diverges as the potential values at which the electric field tends to zero and attains negative values in regions of the surface potentials depending on their polarity and values of the surface crystal potential. Negative values of the capacitance may indicate the thermodynamic instability of the system that can result from neglecting the short range interaction contribution.
Yuriy Reznikov: Memories of Liquid Crystal Society Commonwealth & MRSU group R&D in area of Yuriy Reznikov’s activity J. Mol. Liq. (IF 4.513) Pub Date : 2018-04-06 V.V. Belyaev, S.I. Torgova, N.N. Barabanova, A.K. Dadivanyan
One chapter of the paper is devoted to memories of two members of Board of LC Society Commonwealth on Yuriy Reznikov. Another chapter is a brief description of theoretical models developed in the MRSU group under leadership of Professor Artem Dadivanyan (†2017) in area of the LC orientation and photo-induced effects are presented. Many of these R&D were initiated by Yuriy Reznikov with his colleagues from many countries.
Natural convection and entropy generation of a ferrofluid in a square enclosure under the effect of a horizontal periodic magnetic field J. Mol. Liq. (IF 4.513) Pub Date : 2018-04-27 S.A.M. Mehryan, Mohsen Izadi, Ali J. Chamkha, Mikhail A. Sheremet
The current work is concerned with the study of the impacts of a periodic magnetic field on natural convection and entropy generation of Fe3O4-water nanofluid flowing in a square enclosure. The magnetic field is applied as a sinusoidal function of the y coordinate. The Galerkin finite-element method is employed to numerically solve the model governing partial differential equations. To evaluate the correctness and accuracy of the results, comparisons have been performed between the outcomes of this work and previously published results. The governing dimensionless parameters and their corresponding ranges are the Rayleigh number (Ra = 103–106), Hartmann number which indicates the amplitude of the periodic magnetic field (Ha = 0–50), the period number (λ = 0.1–1.0) and the nanoparticles volume fraction (φ = 0–0.08). The outcomes of the study are presented in the forms of streamlines, isotherms and entropy generation contours as well as the local and average Nusselt numbers. Regardless of Ha and λ values, the average Nusselt number Nuavg and the total entropy generation St associated with the periodic magnetic field are found to be higher than those corresponding to the uniform magnetic field. Additionally, When λ = 0.25 and Ra = 106, for Ha < 10, using the Fe3O4 nanoparticles enhances the total entropy generation St, however, when Ha > 10, the effect of the existence of the nanoparticles on St would be inverse.
Influence of magnetic field on Al2O3-H2O nanofluid forced convection heat transfer in a porous lid driven cavity with hot sphere obstacle by means of LBM J. Mol. Liq. (IF 4.513) Pub Date : 2018-04-27 M. Sheikholeslami
In this research, nanofluid flow in a three dimensional porous cavity under the impact of magnetic field is simulated by means of Lattice Boltzmann Method. The enclosure is full of Al2O3-H2O nanofluid. Properties of nanofluid are estimated via single phase model considering Brownian motion effect. Mesoscopic simulations are done for various values of Darcy number, Hartmann number and Reynolds number. Results demonstrate that temperature gradient has direct relationship with Darcy number and Reynolds number. Increasing Lorentz forces leads to reduce in Nusselt number.
Experimental and correlational study of phase equilibria in aqueous solutions of phosphoric acid with alcohols at different temperatures J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-20 A. Ghanadzadeh Gilani, A. Najafgholizadeh, B. Mohammadi khanghah, M. Nasouri Gazani
Liquid-liquid equilibrium (LLE) data were measured for the aqueous mixtures of phosphoric acid with 1-pentanol and 1-heptanol at T = (298.2, 308.2, and 318.2) K and atmospheric pressure. These ternary systems exhibit as Treybal's type-1 liquid-liquid phase behavior. The reliability of the experimental tie-lines was checked using the Othmer-Tobias and Hand correlation equations. The activity coefficient models of NRTL and UNIQUAC were applied to fit the experimental tie lines. For these models, values of the binary interaction parameters between each pair of components in the studied systems were obtained. Experimental distribution coefficients and selectivity factors for the immiscibility regions were determined.
Tb(III) complexes with nonyl-substituted calixarenes as building blocks of hydrophilic luminescent mixed polydiacetylene-based aggregates J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-20 Julia Elistratova, Bulat Akhmadeev, Rustem Zairov, Alexey Dovzhenko, Sergey Podyachev, Svetlana Sudakova, Viktor Syakaev, Raz Jelinek, Sofia Kolusheva, Asiya Mustafina
The present work for the first time introduces PDA-based vesicles as convenient supporters of luminescent water insoluble Tb3+ complexes. The specific cyclophanic structure of the ligands, where upper and lower calixarene rims are decorated by nonyl- and chelating groups correspondingly provides both complex formation with Tb3+ ions with the coordination of the latter via two 1,3-diketonate groups and self- or mixed aggregation of the complexes. The conditions of the self-aggregation of the Tb3+ complexes are revealed, although the self-aggregates are unstable being converted into the nanosized precipitates which tend to further aggregation and phase separation. The complexes exhibit Tb(III)-centered luminescence which tends to change in time following the phase separation processes. The embedding of the Tb3+ complexes into the PDA-based vesicles results in the mixed aggregates with significant Tb(III)-centered luminescence and significant colloidal stability. The latter arises from high negative electrokinetic potential values due to exterior carboxylic/carboxylate groups of the PDA vesicles.
Epigrammatic progress and perspective on the photocatalytic properties of BiVO4-based photocatalyst in photocatalytic water treatment technology: A review J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-20 Mohamad Fakhrul Ridhwan Samsudin, Suriati Sufian, B.H. Hameed
In recent years, Advanced Oxidation Processes (AOPs) via photocatalyst has shown great promises as a new frontier environmental friendly and sustainable wastewater treatment technology in replacing the current conventional techniques. At present, bismuth vanadate (BiVO4) has garnered much attention as one of the promising photocatalysts in environmental remediation applications under visible light irradiation. This is due to intrinsic physical and chemical features of BiVO4; appealing electronic band structure, high physicochemical stability and environmental friendliness. This review aims to provide an insight into the most recent progress in synthesis, properties and photocatalytic applications of BiVO4, particularly in wastewater treatment. Special emphasis is also placed on the discussion on the major limitations exists within the BiVO4 photocatalyst such as poor charge carrier transfer, slow water oxidation kinetics and fast recombination rate. Subsequently, an insight into the most recent strategies to circumvent the major limitations is detailed. Finally, invigorating perspectives and future directions of this BiVO4 photocatalyst will be presented. It is anticipated that this review will deliver a scientific and technical overview to the researchers who work in this field to facilitate the next generation of BiVO4 photocatalyst with profound performances.
Enhanced methylene blue adsorption onto activated reed-derived biochar by tannic acid J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-21 Yan Wang, Yong Zhang, Shiyin Li, Wenhui Zhong, Wei Wei
This study investigated the effect of tannic acid (TA) on the adsorption efficiency of activated biochar (ABC) prepared from reed biomass regarding the removal of methylene blue (MB) from aqueous solution. The structure and chemical properties of the obtained ABC adsorbent were characterized by XRD, FTIR, N2 adsorption-desorption isotherms, and scanning electron microscopy. After the HNO3 activation of the original biochar (BC), the well-developed porous surface structure of ABC was observed with a considerable increase in the specific surface area. The adsorption behavior of MB onto ABC was determined with the presence of TA (pre-loading versus co-introduction with solute). Results demonstrated that the removal of MB was promoted in the presence of TA solutions with pH ranging from 4.0 to 8.0, and an increase of the initial concentration of TA (from 10 to 50 mg/L) caused a more pronounced promotion effect. The adsorption of MB onto ABC followed the Elovich kinetic model, suggesting a heterogeneous multilayer adsorption process. The adsorption data were best described by the Sips isotherm model, showing a maximum adsorption amount of 77.35 mg/g in the presence of TA, which was much higher than many reported adsorbents. The adsorption mechanism appeared to be related to electrostatic interaction, hydrogen bonding, ion exchange, n-π/π-π interaction, etc. Findings of the present work highlighted the positive effect of TA on the adsorptive removal of MB by ABC, and were also beneficial for developing reed-derived biochar as an engineered absorbent for removal of toxic dyes from aqueous solution.
Amphiphilic second-order phase transitions determined through NMR J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-21 Teresa Reilly, Mohamed I.H. Mohamed, Teresa E. Lehmann, Vladimir Alvarado
In this work, nuclear magnetic resonance (NMR) spectroscopy is used to investigate surfactant phase behavior over a broad concentration region. This technique is an adaptation of a previously developed method applied to detect the critical micelle concentration (CMC) of surfactants. In this method, a surfactant concentration is correlated to the normalized intensity, or area, of the NMR signal for each surfactant. In this procedure a linear relationship develops on either side of the CMC, with a distinct change in slope where the primary phase change occurs. The research conducted herein investigates the NMR response at higher surfactant concentration, where the phase change consists of a change in micelle shape or other structural configurations. These secondary phase transitions can be expected from 10 to 90 wt.%, where the CMC measurements are conducted at concentrations <1 wt.%. The solutions were also analyzed with dynamic light scattering (DLS) and a cross-polarizer microscope to confirm suspected detected phase changes. Visible changes in the rheological response were observed and therefore carefully examined. In a large part, the results seen with all methods corresponded with visible differences in the surfactant solutions and detected changes in the NMR protocol.
Entropy generation of dissipative flow of carbon nanotubes in rotating frame with Darcy-Forchheimer porous medium: A numerical study J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-21 G.S. Seth, R. Kumar, A. Bhattacharyya
This research article explains the influence of magnetic field and volume fraction of carbon nanotubes (CNTs) on the flow over a stretching sheet in rotating frame. We analysed the behaviour of base fluid such as water with both kind of CNTs i.e. multi-wall carbon nanotubes (MWCNTs) and single-wall carbon nanotubes (SWCNTs). The nanofluid transport mechanism is obtained following Xue model. The mathematical model is developed by order of magnitude analysis. Governing partial differential equations are first converted into a system of ordinary differential equations making the use of suitable similarity transformation and then solved by developing i.e. fourth order finite difference scheme using Newton's linearization technique, which helps us to deal with the non-linear terms in a very smooth way. Numerical simulation for the fluid velocity and fluid temperature along with Nusselt number and skin friction coefficient are carried out for a set of values of different regulatory flow parameters that characterize the physics of the flow graphically. An outstanding correlation is perceived in tabular form of mesh density solutions of different length of domain obtained by fourth order finite difference scheme. The Biot number, Brinkmann number and applied magnetic field have vital effects on the thermal energy irreversibility in terms of Bejan number.
Structure and kinetics of water in highly confined conditions: A molecular dynamics simulation study J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-21 Amal Kanta Giri, Filipe Teixeira, M. Natália D.S. Cordeiro
In this work, we carried out a systematic and detailed study of water under severely confined conditions, based on atomistic molecular dynamics (MD) simulations. Specifically, MD simulations were performed for water confined in single-walled capped carbon nanotubes of chiral indices between (4,4) and (10,10). The structure and dynamics of confined water, and its dependence on the diameter and length of the capped carbon nanotubes (CCNTs) was examined, alongside with the influence of the latter on water immersion. Our results show that the axial water density decreases with increasing distance from the open face of the CCNTs, and that water forms well-defined shells along the radius of the CCNTs. The confined water molecules closer to the water–wall interfacial region tend to orient themselves pointing their OH bonds towards the wall. This trend becomes less evident in the inner regions of the CCNTs, so that the water molecules in the central region of the (10,10) CCNT are almost randomly oriented. On the other hand, the water molecules inside the (6,6) CCNT form a single-file chain along the CCNT's axis. Furthermore, the average number of hydrogen bonds per water molecule decreases with increasing length of the CCNT and decreasing diameter. Hydrogen bonding and water orientations in the CCNTs significantly affect the mobility of water, being the mobility of water faster in the (7,7) CCNT than in other CCNTs of the same length.
[Fe(CN)6]4−/[Fe(CN)6]3− based metal organic ionic frameworks and impact of Fe2+/Fe3+ on material-medicinal-properties J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-21 R.K. Ameta, Rohit R. Koshti, Akshay Vyas, Chirag Rane, Nitin Kumar Sharma, Man Singh
Study reports the preparation and material-medicinal-properties (MMPs) of Metal Organic Ionic Frameworks (MOIFs) of [Fe(CN)6]4−/[Fe(CN)6]3− with dodecyltrimethylammonium bromide (DTAB), Tetradecyltrimethylammonium bromide (TTEB) and Hexadecyltrimethylammonium bromide (HTEB). MOIFs with [Fe(CN)6]4− are found in liquid state as metallic ionic liquids while with [Fe(CN)6]3− in solid state (SMOIFs). MOIFs were characterized with UV/Vis, FTIR, Raman and powder XRD measurements where the ionic interaction between coordination sphere of [Fe(CN)6]4−/[Fe(CN)6]3− and quaternary nitrogen of DTAB was analyzed. The thermal conductivity of LMOIFs has also been studied where an increase in conductivity with temperature is noticed, inferring their electrolytic property as well as thermal stability proposing them as electrolyte for Li/Na ionic batteries. Viscoelastic property of MOIFs reveals the mechanical stability also inferring their use in ionic batteries. MOIFs have shown their dye degradation activity studied with Methyl Orange (MO) and Methyl Red (MR) depicting impact of Fe2+ and Fe3+. MOIFs have shown their protein binding nature studied with BSA, analyzed with spectrophotometric titrations revealing that hydrophobicity works according to oxidation state of metal. MOIFs have also been tested against microorganism for their antimicrobial potential where number of DTAB unit has been found for respective activity with both the ferro and ferricyanide units for gram –ve bacteria whereas the effect of DTAB unit with Fe3+ and Fe2+ was found inverse.
Effect of adsorption of polyethylene glycol (PEG), in aqueous media, to improve cellulose nanostructures stability J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-19 Giovanni F. de Lima, Alana G. de Souza, Derval S. Rosa
In recent year, the interest in environmentally friendly materials, like cellulose nanostructures (CNSs) has increased. Nanoscale dimensions, high surface area, low density, and high mechanical strength are examples of CNSs properties that attract researchers' attention. CNSs stability and dispersity are the main limitations that prevent its application as nanofiller in polymeric matrices. In this work, the surface modification of CNSs was investigated. To overcome CNSs limitation, they were modified with polyethylene glycol (PEG), in aqueous solution, in different proportions: 2, 5 and 10 wt%. FTIR, elemental analysis, NMR, and XPS were carried out to verify the adsorption efficiency. The results showed an excellent adsorption of PEG chains on the CNSs surface, with particle size increase of 50–90 nm and a considerable increase in thermal stability. XRD and AFM analysis observed no significant variation in crystallinity and morphology in modified CNSs. Thus, modification of CNSs with PEG is an environmentally friendly process and showed positive results regarding improving CNSs stability, in aqueous media.
Control volume based finite element simulation of magnetic nanofluid flow and heat transport in non-Darcy medium J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-19 Mohsen Sheikholeslami, Ahmad Zeeshan, Aaqib Majeed
Magnetic nanofluids are used in cancer therapeutics by utilizing cancer imaging and drug delivery. These are also used to kill cancerous cells without affecting the nearby healthy cells by producing higher temperatures around tumor. This investigation aims to explore the heat transfer in non-Darcy porous medium for magnetic nanofluid flowing due to external magnetic field. Nanoparticle shapes and their properties are also considered. Vorticity stream function formulation is also employed. The solutions of the resulting system of equations are found by CVFEM. Illustrations are outlined pictorially for numerous physical parameters namely, Rayleigh number, radiation parameter, Darcy number, Fe3O4-water based volume concentration and Hartmann numbers. Outcomes indicate that augmenting in Hartmann number results in reduce in velocity of nanofluid and heat transfer rate. The nanoparticle with shape Platelet gives maximum heat transfer rate.
Electrospun chitosan/poly(ethylene oxide) nanofibers applied for the removal of glycerol impurities from biodiesel production by biosorption J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-19 Bruna Silva de Farias, Évelin Mendes Vidal, Natália Torres Ribeiro, Nauro da Silveira, Bruna da Silva Vaz, Suelen Goettems Kuntzler, Michele Greque de Morais, Tito Roberto Sant'Anna Cadaval, Luiz Antonio de Almeida Pinto
Electrospun chitosan/poly(ethylene oxide) nanofibers were synthetized, characterized and applied as alternative biosorbents to remove pigments from pretreated crude glycerol. The pigments removal efficiency of electrospun nanofibers was examined by comparing the adsorption capacity of nanofibers with other chitosan–based biosorbents. Pseudo–first order, pseudo–second order and Elovich models were used to estimate kinetic parameters. The nanofibers exhibited continuous fibers, with the average fibers diameter of 526 ± 101 nm. The results also indicated interactions between chitosan and poly(ethylene oxide) molecules, without changing the main adsorptive sites of chitosan. Furthermore, chitosan/poly(ethylene oxide) nanofibers exhibited higher relative adsorption capacity (120 g−1) than chitosan powder (35 g−1) and chitosan biopolymeric film (58 g−1). The pseudo–first order and Elovich models were the most suitable models to represent the kinetic behavior of the composite nanofiber.
Comprehensive study on biocorona formation on functionalized selenium nanoparticle and its biological implications J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-19 Debolina Chakraborty, Pooja Chauhan, Sruthi Ann Alex, Savita Chaudhary, K.R. Ethiraj, N. Chandrasekaran, Amitava Mukherjee
Selenium nanoparticles paved its way into the field of medicine because of its lowered toxicity and excellent biological properties. Interaction between these nanoparticles and serum proteins leads to the formation of protein corona (hard and soft) on the nanoparticle surface modulating its biological behaviour and fate. In the present study, we have emphasized on the biocorona formation of most abundant serum proteins i.e. human serum albumin, immunoglobulin-G, and transferrin on functionalized selenium nanoparticles (CTAB, SDS, and brij-58). Changes in protein adsorption pattern, mean hydrodynamic size, and zeta potential of differently functionalized selenium nanoparticles, following protein coronation were analysed for various incubation periods. Quantification of hard corona and soft corona for individual protein and for protein mixture was also done. The biological impact of protein coronation on selenium nanoparticles was evaluated by the cellular uptake and cell viability studies. Finally, modulation in radical scavenging property of selenium nanoparticles before and after protein corona formation was studied through DPPH assay.
Facile one-pot synthesis of novel structured IONP@C-HIOP composite as superior electrocatalyst for hydrogen evolution reaction and aqueous waste investigation of bio-imaging applications J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-19 Raji Atchudan, Thomas Nesakumar Jebakumar Immanuel Edison, Suguna Perumal, Mani Shanmugam, Yong Rok Lee
Hexagon-shaped composite made up of iron oxide nanoparticles@carbon (IONP@C-HIOP) was successfully synthesized at 185 °C by a simple hydrothermal method. All the analytical results confirmed the formation of IONP@C-HIOP with a uniform size without apparent aggregation. The IONP@C-HIOP composite exhibits excellent catalytic activity towards hydrogen evolution reaction (HER) with lowest onset-potential (−25 mVRHE) and Tafel slope (45 mV dec−1) in 0.5 M H2SO4 aqueous electrolyte. The high electrocatalytic performance of the composite towards HER attributes to the carbon decorated IONPs, providing a conducting network for fast electron transport from IONPs to electrodes. The composite shows high stability representing a synergistic effect between IONPs and carbon for efficient HER. In addition, the supernatant solution (byproduct) of IONP@C-HIOP showed durable fluorescence activity and was used as a label-free fluorescent probe for live cell imaging applications. This method of synthesis is a simple and economic for multi-diverse applications. Thus, the main product of synthesized IONP@C-HIOP might be an ideal choice for environmental-friendly applications HER and the byproduct for cell imaging.
Synthesis of highly-efficient functionalized biochars from fruit industry waste biomass for the removal of chromium and lead J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-18 Sabolc Pap, Veselin Bezanović, Jelena Radonic, Anica Babic, Sanja Saric, Dragan Adamovic, Maja Turk Sekulic
Plums and apricots are among the most popular fruits in Serbia and kernels of these are generally disposed of as waste. In common with other organic waste products there is potential to utilise these kernels in wastewater treatment. A new generation of highly-efficient biochars were therefore developed for low-cost wastewater treatment. The aim of this work was to prepare functionalized biochars from different fruit industry waste biomass and to evaluate their ability to for lead and chromium adsorption. Fruit kernel based biochars were synthesized by pyrolysis and functionalized with sulphuric acid. The biochars were characterized using: proximate-ultimate analysis, the Brunauer, Emmett and Teller technique, surface functional group analysis with Fourier-transform infrared spectroscopy, pHpzc and scanning electron microscopy with energy dispersive X-ray spectroscopy. Heavy metal adsorption by biochars was studied using different process parameters was shown to occur through different adsorption mechanisms. Three kinetic and two isotherm models were applied to the experimental data. Sulphur-containing functional groups on the biochar surface played an important role in binding. The high adsorption efficiency is attributed to surface complexation of biochar functional groups with heavy metal ions. Based on these results, biochars could be used as a highly efficient adsorbent for removal of heavy metals from aqueous solutions.
Synthesis, optimization and characterization of mesoporous Mg-Al-Fe tri-metal nanocomposite targeting defluoridation: Synergistic interaction of molar ratio and thermal activation J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-18 Humayun Kabir, Ashok Kumar Gupta, Debjyoti Debnath
In the present study, the synthesis of a novel tri-metal nanocomposite (TMNC) Mg-Al-Fe using co-precipitation method was optimized by a 33 factorial design. The physicochemical properties were characterized by XRD, FESEM, EDX, HRTEM, FTIR, BET, and TGA. The influence of process parameters viz. molar ratio of bivalent to trivalent metals, the molar ratio of trivalent metals, and the calcination temperature on the preparation of TMNC targeting fluoride adsorption was also elucidated. The substantial variation of adsorption capacity from 1.20–4.98 mg/g established the vital role of optimum molar ratio and calcination temperature in the preparation of TMNC. It was observed that the adsorbent with bivalent to trivalent metal molar ratio of 5 and calcined at 400 °C exhibits maximum Langmuir adsorption capacity of 90.68 mg/g. The high surface area and mesoporous structure of the mixed metal nanocomposite obtained at optimum preparation conditions play an essential role in enhancing its fluoride removal capability.
Dispersions of Magnetic Nanoparticles in the Mixture Ethyleneglycol-Choline Chloride: the Role of Solvent Association J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-18 C. Kern, R. Aquino, E. Dubois, R. Perzynski, V. Peyre
The mixture of choline chloride and ethyleneglycol ((1:3) on the molar scale) is first characterized using density, viscosimetry and refractive index measurements, in the temperature range 20-45°C, with controlled amounts of water. Thermodynamic parameters such as the activation entropy, enthalpy and Gibbs energy for the viscous flow are deduced from the data and show that the solvent is highly structured. A protocol to disperse in this solvent 10 nm maghemite nanoparticles previously synthesized in water is described. The good quality of the dispersion is assessed by visual observations, optical microscopy, small angle X-ray scattering (SAXS), magnetization measurements, viscosimetry, and light scattering. The results lead to the description of a local viscosity around the particles, lower than the macroscopic one, that could be the result of the solvent segregation with ethyleneglycol being mostly present in the close vicinity of the particles.
Multiwavelength UV-metric and pH-metric determination of the dissociation constants of the hypoxia-inducible factor prolyl hydroxylase inhibitor Roxadustat J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-18 Milan Meloun, Lucie Pilařová, Milan Javůrek, Tomáš Pekárek
The dissociation constant pKa of the Roxadustat with UV-VIS spectra, molar absorption coefficients and protonation equilibria are the key physicochemical parameters influencing many biopharmaceutical characteristics. Roxadustat is an orally bioavailable, hypoxia-inducible factor prolyl hydroxylase inhibitor with potential anti-anemic activity. It belongs to Active Pharmacenutical Ingredients, which have acidic/basic functionalities, their ionization state is controlled by solution pH and acid dissociation constants. Nonlinear regression of the pH-spectra with programs REACTLAB and SQUAD84 and of the pH-titration curve with ESAB determined four multiple consecutive dissociation constants with the protonation scheme. A sparingly soluble neutral molecule LH3 of Roxadustat was dissociated to the soluble anions LH2−, LH2− and L3− or protonated to the cation LH4+ in an aqueous medium. The graph of molar absorption coefficients of variously protonated species according to wavelength shows that the spectra of two anions LH2− and LH2− are nearly the same in colour. The Roxadustat spectrum exhibited five sharp isosbestic points, which were related to the LH2−/L3− equilibrium. Four consecutive thermodynamic dissociation constants were estimated using UV-metric data pKTa1 = 3.60(04), pKTa2 = 5.62(14), pKTa3 = 7.66(16), pKTa4 = 9.08(02) at 25 °C and pKTa1 = 3.60(04), pKTa2 = 5.73(10), pKTa3 = 7.52(10), pKTa4 = 8.99(02) at 37 °C and using pH-metric data pKTa1 = 4.33(09), pKTa2 = 6.57(11), pKTa3 = 8.88(05), pKTa4 = 9.03(04) at 25 °C and pKTa1 = 4.25(09), pKTa2 = 6.49(10), pKTa3 = 8.80(06), pKTa4 = 9.00(05) at 37 °C The positive values of the enthalpy ΔH0 showed that the dissociation process is endothermic and the positive values of the Gibbs free energy ΔG0 at 25 °C indicated that the dissociation process was not spontaneous, which also was confirmed by a negative value of the entropy ΔS0. Four macro-dissociation constants of Roxadustat and six protonation locations were predicted by MARVIN.
A novel approach to Lithol red nanopigment by water in oil microemulsion method J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-18 M. Zarandi, M. Kazemi, Z. Mohamadi, A. Ghasemzadeh
Lithol Red is one of the commonest 20th century red synthetic organic pigments. It is used in various printing industry for its brightness and bleed-resistance. Performance of pigments depends on their size completely. In the current research, microemulsion as simple and novel method has been applied for the preparation of Lithol red nanopigment. The optimized microemulsion formulation contains water 15%, n-butyl acetate 55%, cethyl trimetyl ammonium bromide (CTAB, as cationic surfactant) 15% and 2-propanol (as co-surfactant) 15%. Lithol red nanopigments are characterized by SEM and TEM. Prepared Lithol red nanopigments were spherical with the average diameter of 60 nm and low size distribution.
Dependence of physical parameters on the size of silver nano particles forming composites with a nematic liquid crystalline material J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-18 Pratibha Tripathi, Mukesh Mishra, Sandeep Kumar, Roman Dabrowski, Ravindra Dhar
Thermodynamic, dielectric and electro-optical properties of a nematic liquid crystal namely 4-(trans-4-n-hexylcyclohexyl) isothiocyanatobenzoate (6CHBT) mixed with silver nanoparticles (Ag-NPs) of two widely different sizes have been studied. Thermodynamic studies suggest nominal increase in isotropic to nematic transition temperature of the nano composites as compared to the pure 6CHBT. Dielectric parameters of nano composites in the homeotropic and planar aligned samples have been measured in the frequency range of 1 Hz–35 MHz. Dielectric studies suggest that anisotropy is marginally decreased due to the dispersion of Ag-NPs. Threshold voltage for Freedericksz transition and splay elastic constant has decreased in the case of nano composites. Dielectric studies also suggest that relaxation mode corresponding to the molecular rotation about its long axis cannot be detected in the experimental window of the frequency. However, we obtained a relaxation mode due to the molecular rotation about its short axis.
Enhancing the purity of magnesite ore powder using an ethanolamine-based collector: Insights from experiment and theory J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Wenbao Liu, Wengang Liu, Shujuan Dai, Ting Yang, Zhen Li, Ping Fang
Magnesite ore powder is the primary raw material used to prepare refractory magnesia. With the depletion of high-grade magnesite, methods to reduce the impurities and improve the quality of magnesite ore powder are urgently required. In this study, an ethanolamine-based surfactant, bis (2-hydroxyethyl) dodecylamine (BHDA), was first introduced into the flotation of magnesite ore as a novel collector, and the possibility of improving the purity of the ore was investigated by experiment and theory. Flotation tests, X-ray photoelectron spectroscopy, Fourier-transform-IR spectroscopy, and zeta potential measurements were carried out to study the behaviors and mechanisms by which the collector enhances the purity of magnesite ore powder. The flotation results revealed the noticeable difference in the floatability of quartz, magnesite, and dolomite when combined with the collector over a wide range of pulp pH values (4.18–9.17). The analytical results obtained from FTIR spectra, XPS, and zeta potential measurements indicate that BHDA was readily adsorbed on the surface of quartz, mainly by electrostatic and hydrogen bonding interactions, whereas it was adsorbed on the surfaces of magnesite and dolomite by weak electrostatic interactions. By introducing a hydroxyethyl group to the tertiary amine collector, more hydrogen bonds can form with the surface of quartz, strengthening the adsorption stability. Thus, compared to the traditional collector, dodecylamine, BHDA showed better desilication and purification performance for magnesite ore powder. Meanwhile, our results show that the simpler reagent system and process flow makes BHDA promising for the industrial purification of magnesite ore powder.
Statistical evaluation of three kinds of sonochemically-prepared magnetic conductive polymer nanocomposites for ultrasound-assisted ligandless uptake of some deleterious metal ions in vegetable samples J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Alireza Asghari, Sara Mollaei Parvari, Maryam Hemmati, Maryam Rajabi
In this work, three effectual nanoadsorbents in terms of both the synergically conductive and magnetic properties, named as PTh/surfactant/Fe3O4, PANI/surfactant/Fe3O4, and Ppy/surfactant/Fe3O4, were compared for the simultaneous ligandless preconcentration of Pb2+ and Ni2+ ions from some vegetable samples. The enrichment/detection process was performed by an ultrasound-ameliorated extraction method coupled with micro-sampling flame atomic absorption spectrometry, benefited by the ease of use, high speed, bio-compatibility, low cost, and high preconcentration. Also a simple and effective synthesis of magnetic nanocomposites by an impressive co-precipitation method followed by an efficient in situ sonochemical oxidative polymerization embossed the current procedure. Under optimized conditions obtained by multivariate approaches, pH 5.5, 5 min ultrasonic time, 20 mg of the best nanoadsorbent (PTh/surfactant/Fe3O4), and 250 μL of the eluent resulted in high extraction percentages (85–95%). The calibration curves obtained showed the good liner ranges of 4–400 ng mL−1 and 4–650 ng mL−1 for Ni2+ and Pb2+ ions, respectively, accompanied with low detection limits ranging from 1 to 1.2 ng mL−1. The preconcentration factor was found to be 40. No significant interference of serious foreign agents in the trace analysis of the aforementioned metal ions indicated a good selectivity of the ligandless ultrasound-promoted microextraction procedure, which can be considerably owned by the versatile magnetic nanosorbent. On the other hand, the superb figures of merits demonstrated a great effectiveness of the ultrasonic irradiation in the impressive synthesis of the nanosorbent as well as the facile and efficient microextraction of trace amounts of Ni2+ and Pb2+ ions in complicated plant matrices.
Measurement and correlation of the solubility of antipyrine in ten pure and water + ethanol mixed solvents at temperature from (288.15 to 328.15) K J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Zhirong Wang, Guangyi Zhou, Jiejie Dong, Zhili Li, Lei Ding, Baohua Wang
The aim of this experiment is to obtain new antipyrine solubility data and the correlation equation parameters and thermodynamic parameters of the dissolution process. The solubility of antipyrine was experimentally measured in ten mono-solvents (methanol, ethanol, acetone, n-propanol, isopropanol, methyl acetate, n-butanol, isobutanol, ethyl acetate, water) and binary mixed solvents (ethanol–water) at 288.15 to 328.15 K using a gravimetric method under atmospheric pressure. In addition, the experimental solubility in the mono- and mixed solvents was correlated using the λh equation, modified Apelblat equation, nonrandom two-liquid equation, Wilson equation, and van't Hoff equation. Good agreement was found between the experimental values and correlation values calculated by all the selected equations. The thermodynamic parameters, Gibbs energy (∆G°sol), molar enthalpy of dissolution (∆H°sol), and molar entropy of dissolution (∆S°sol) were also calculated. These experimental results are crucial for optimization of the antipyrine crystallization process.
Pressure and temperature dependence of light fullerenes solubility in n-heptane J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Konstantin N. Semenov, Nikolay A. Charykov, Enriqueta R. López, Josefa Fernández, Juan J. Parajó, Nikita E. Podolskii, Igor V. Murin
Solubility of individual light fullerenes (C60 and C70) in n-heptane was measured in the ranges of pressure from 0.1 up to 110 MPa and temperature from 298.3 to 358.3 K. At 0.1 MPa, the solubility diagrams of the C60 – n-heptane, C70 – n-heptane binary system consists of only one branch corresponding to crystallization of mono-solvated fullerenes – C60·C7H16 and C70·C7H16. The compositions of the solid crystalline solvates were determined by thermogravimetric analysis. Thermodynamic description of the temperature and pressure dependences of solubility was performed using the van-der-Waals differential equation. As a result, the changes of the isothermal compressibility, molar volume, isobaric heat capacity and molar entropy in the process of the light fullerenes dissolution with formation of infinitely diluted solution were calculated.
Assessment of solvent effects on the inclusion behavior of pyrazinamide drug into cyclic peptide based nanotubes as novel drug delivery vehicles J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Mahnaz Shahabi, Heidar Raissi
In the present work, the encapsulation process of Pyrazinamide drug into the cyclic peptide nanotubes with the different numbers of cyclic peptides as novel drug carriers is investigated using density functional theory calculations in the aqueous medium. The negative computed binding energies for all inclusion complexes reveal the stabilization of Pyrazinamide molecule inside the cavities of the nanotubes. Moreover, our computational results indicate that the interaction between Pyrazinamide molecule and the cyclic peptide nanotubes is weak; so that, the drug encapsulation process is typically physisorption. The formation of more number of conventional hydrogen bonds between the Pyrazinamide drug molecule and the active sites of the cyclic peptide nanotube's backbone facilitates the enhancement of binding affinity of the drug molecule into the nanotube with two cyclic peptides and further more stability of the inclusion complex. To characterize the nature of the intermolecular interactions through the topological parameters, the values of electron densities and their Laplacian have been analyzed using the Bader's theory of atoms in molecules. The origin charge transfer during orbital interactions within the encapsulation process of Pyrazinamide drug into cyclic peptide nanotubes is evaluated by the natural bond orbital method. The encapsulation process of Pyrazinamide in the cavity of the nanotubes imparts significant impact on the solvation energy of the drug molecule as well as cyclic peptide nanotubes which introduces the cyclic peptide nanotubes as efficient carriers for delivery of Pyrazinamide drug in nanomedicine domain.
Molecular dynamics simulation of self-assembly and viscosity behavior of PAM and CTAC in salt-added solutions J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Dongjie Liu, Fei Liu, Wenjing Zhou, Fei Chen, Jinjia Wei
In this study, the self-assembly of cationic surfactant cetyltrimethyl ammonium chloride (CTAC) and nonionic polymer polyacrylamide (PAM) in aqueous solution with added sodium salicylate (NaSal) as counter-ion salt is studied using a coarse-grained molecular dynamic simulation (CGMD). The microstructure evolution shows that in the mixed solutions, surfactant micelles are readily to associate with polymer and can form a new complex of CTAC and PAM with interconnected network structures, which can be attributed to the hydrophobic interactions, the attraction between acylamino and the head of CTAC, and the attraction between Sal− and acylamino. The calculation of radial distribution function for different sites also proved the aggregate of the surfactant and polymer. Then a reverse non-equilibrium molecular dynamics (RNEMD) simulation is used to investigate the rheological property of the mixed solutions, the CTAC/NaSal solution and the PAM solution. The molecular dynamics simulation demonstrates that the viscosity of the CTAC/PAM/NaSal solution is significantly higher than that of the CTAC/NaSal solution, mainly because the surfactant micelles interacted with the polymer and formed rod-like micelles.
Experimental study of physicochemical changes in water by iterative contact with hydrophilic polymers: A comparison between Cellulose and Nafion J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Vittorio Elia, Rosario Oliva, Elena Napoli, Roberto Germano, Gabriella Pinto, Liliana Lista, Marcella Niccoli, Dario Toso, Giuseppe Vitiello, Marco Trifuoggi, Antonella Giarra, Tamar A. Yinnon
Water kept in contact with cellulose has not been a “juicy” research topic until now. This is surprising because cellulose is a major component of the cell walls in green plants. It is also a common material used in many artificial systems, e.g., filters. In this work, we review some of our experimental results and show that iteratively bringing cellulose (cotton wool) in contact with pure water endows the water with some unforeseen properties. For example, the liquid left over after removing the cellulose is optically active, i.e., mirror symmetry breaking was triggered during temporary contact of bulk water with a natural polymer. (Here and in the following, by “mirror” symmetry we actually mean “chiral” symmetry). Moreover, this leftover liquid fluoresces after irradiation with ultraviolet light. These properties are neither attributable to impurities released by the inert polymer nor to organic- or bio-contaminants, as our state-of-the-art analytical techniques show. These techniques include gel electrophoresis, Matrix-Assisted Laser Desorption/Ionization Time of Flight (MALDI-TOF) and Gas Chromatography both coupled with Mass Spectrometry. Instead, the properties are attributable to stabilization of interfacial water adjacent to hydrophilic membranes. Our findings have implications for processes in water flowing adjacent to cellulose, in particular enantioselective processes. Such processes play critical roles in many bio-systems and technologies. Thus, our study indicates that water iteratively brought in contact with cellulose merits intensive research.
Novel zwitterionic Natural Deep Eutectic Solvents as environmentally friendly media for spontaneous self-assembly of gold nanoparticles J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Antonello Di Crescenzo, Matteo Tiecco, Romina Zappacosta, Simona Boncompagni, Pietro Di Profio, Valeria Ettorre, Antonella Fontana, Raimondo Germani, Gabriella Siani
The potential application of some novel zwitterionic Natural Deep Eutectic Solvents, NADESs, based on betaine N,N,N-trimethylglycine and carboxylic acids (glycolic, phenylacetic and oxalic acid), has been evaluated in the synthesis of gold nanoparticles (AuNPs). AuNPs have been successfully obtained by reduction of gold(III) chloride trihydrate by ascorbic acid or sodium borohydride as reducing agents, without the use of any surfactant or capping agent. The effect of the different experimental conditions (nature of the reducing agent, temperature) has been discussed. In the NADES composed of trimethylglycine and oxalic acid, no addition of a reductant was needed because AuNPs start to form immediately after the dissolution of the precursor salt. This result may open new perspectives in fine-tuning smart solvent characteristics and developing the most appropriate NADES for an environmentally friendly metal nanoparticle synthesis without using auxiliary chemicals.
Surface activity, foam properties and aggregation behavior of mixtures of short-chain fluorocarbon and hydrocarbon surfactants J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Ning Jiang, Youjie Sheng, Changhai Li, Shouxiang Lu
Surface activity, foam properties and aggregation behavior of a short-chain fluorocarbon surfactant (FS-50), an anionic hydrocarbon surfactant (sodium dodecyl sulfate, denoted as SDS) and FS-50/SDS mixture are systemically studied for the first time in this paper. Surface activity was characterized by surface tension. Foam properties, including foamability and foam stability, of the mixed systems were studied based on the standard Ross-Miles method. The aggregation behavior of the surfactant solution was observed by using cryo-transmission electron microscopy (Cryo-TEM). The results show that FS-50 exhibits good surface activity and foam properties, which reveals that as a kind of environment friendly short-chain fluorocarbon surfactant, FS-50 is a perfect substitute of long-chain ones. Surface activity and foam properties of FS-50/SDS mixed system are enhanced by adding FS-50 and further improved by the increase of FS-50 concentration. The foam properties are enhanced by tightening the arrangement of surface adsorbed molecules at the liquid-air interface. A synergistic interaction exists in the mixture of short-chain FS-50 and SDS, which is produced through microscopic spheroidal-to-wormlike transition. Finally, the macroscopic performance of FS-50/SDS mixed solution is enhanced by the changes of composition and morphology of the adsorbed film layer. This work shows an environmental friendly surfactants mixed system and provides a more comprehensive perceive of the relationship between macroscopic properties and micro-aggregation structure of short-chain fluorocarbon and hydrocarbon surfactants mixed system.
Green synthesis g-C3N4 quantum dots loading h-BN for efficient and stable photocatalytic performance J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Tao Wang, Xiqing Liu, Qiuyue Men, Changchang Ma, Yang Liu, Zhi Liu, Pengwei Huo, Chunxiang Li, Yongsheng Yan
Many recent advances in constructing green metal-free materials have opened new possibilities in catalysis. To explore and enhance the photocatalytic performance of g-C3N4 quantum dots (CN QDs), the metal-free materials of CN QDs embedded in the h-BN was successfully synthesized by calcination the mixture of melamine and h-BN. The studies proved the CNBN has appeared red-shift due to the quantum size effect and 2D h-BN. The CN QDs were embedded into the h-BN could not only facilitate the separation and transfer, but also the h-BN terminated with OH groups could act as active sites, thus enhanced the photocatalytic performance. Moreover, this work may pave the way for the application of CN QDs and fabricate 2D h-BN composites for green metal-free materials in another field.
Structural analysis of an amino acid ionic liquid: Bulk and electrical double layer J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Mohammad Razmkhah, Mohammad Taghi Hamed Mosavian, Fatemeh Moosavi
The interfacial structures and macroscopic properties of electrical double layer for 1-Ethyl-3-Methyl-Imidazolium Phenyl Alanine ([EMIM][PHE]), as an amino acid ionic liquid (AAIL), have been investigated by molecular dynamics simulation and compared with conventional [EMIM][PF6]. Result of bulk state showed that hydrogen atoms of ring in [EMIM]+ are capable to form hydrogen bond with the nitrogen and oxygen of [PHE]−. Number of these hydrogen bonds enhances if IL is introduced to graphene sheet. Surprisingly, it was observed that anion-anion hydrogen bond is also probable for [EMIM][PHE]. Introducing the IL to graphene does not affect number of this anion-anion hydrogen bond. Being in touch with graphene or not, the main correlation regime between anion and cation is the tail-ring for studied systems. It was observed that phenyl ring of [PHE]− acts as an inhibitor for [EMIM]+ to form π-π stacking with graphene. This behavior leads to higher accumulation of [PHE]− than [EMIM]+ in the first layer. In the current study, a responding electrical potential for an assumed supercapacitor was also introduced. Responding potential of [EMIM][PHE] is lower than [EMIM][PF6].
Dynamic viscosity of a liquid Sn-3.0Ag-0.5Cu alloy with Ni nanoparticles J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Andriy Yakymovych, Hans Weber, Ivan Kaban, Herbert Ipser
The impact of minor additions of Ni nanoparticles on the dynamic viscosity of the liquid Sn-3.0Ag-0.5Cu alloy (SAC305; in wt%) is examined. The nanocomposite samples were prepared from commercial SAC305 powder and Ni nanopowder by cold pressing. The dynamic viscosity of the (Sn96.5Ag3.0Cu0.5)100–xNix alloys measured during heating and cooling exhibited a hysteresis in a temperature range up to 100 K above the melting temperature. This is supposed to be related to the structural transformations caused by dissolution of Ni nanoparticles in the liquid Sn-based matrix upon heating. The experimental values of the viscosity of the (Sn96.5Ag3.0Cu0.5)100–xNix alloys are in a good agreement with calculated data using thermodynamic approaches.
The effect of ionic liquid adsorption on the electronic and optical properties of fluorographene nanosheets J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Mehdi Shakourian-Fard, S. Maryamdokht Taimoory, Volodymyr Semeniuchenko, Ganesh Kamath, John F. Trant
In the present study, we investigate the adsorption characteristics of six different ionic liquids (ILs) on a fully-fluorinated graphene (fluorographene, FG) surface using electronic structure studies and associated analysis methods. A systematic comparison of differences in IL binding energies (ΔEb) with fluorographene, graphene and hexagonal boron nitride surfaces indicates that fluorination strongly decreases the binding energy compared to the other two surfaces, hence resulting in the binding energetics: ΔEb (Graphene…IL) > ΔEb (Hexagonal boron-nitride…IL) > ΔEb (Fluorographene…IL). To probe the reasons for this difference, quantum theory of atoms in molecules (QTAIM) analysis and non-covalent interactions (NCI) analyses were carried out. Results indicate that the stability of complexes of FG surface with ILs (FG…IL) arises only due to the presence of the expected weak non-covalent intermolecular interactions. The calculation of charge transfers by employing the ChelpG method shows that the interaction of ILs with FG surface generally induces a negative charge on the FG surface. Furthermore, these interactions lead to a decrease of the HOMO-LUMO energy gap (Eg) of the FG surface, enhancing its electrical conductivity. In addition, a detailed analysis of the global molecular descriptors including the Fermi energy level (EFL), work function (WF), electronic chemical potential (μ), chemical hardness (η), global softness (S) and electrophilicity index (ω) was carried out for both the FG surface alone and the adsorbed complexes showing that there are small, but meaningful, differences in the reactivity of the surface depending on the nature of the IL. Finally, time-dependent DFT (TD-DFT) calculations of the optical properties of FG surface and FG…IL complexes reveal that the absorption spectrum of the FG surface undergoes a red shift following IL adsorption. This study demonstrates that FG provides a useful complementary tool to graphene and boron nitride materials, allowing for the fine-tuning of the optoelectronic properties of these monolayer materials. These results will assist in the development of these types of ILs for applications in optoelectronics.
Solubilization of drugs using sodium lauryl sulfate: Experimental data and modeling J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Mohammad Norouz Alizadeh, Ali Shayanfar, Abolghasem Jouyban
Micellar solubilization is a great method for increasing drugs solubility in aqueous environments. At concentrations above the critical micelle concentration (CMC), micelles are formed and they are able to increase the apparent aqueous solubility of poorly soluble drugs. Sodium lauryl sulfate (SLS) is one of the common solubilizing agents in pharmaceutical sciences. Investigation on the water solubility of drugs in the presence of surfactants and the development of a relationship between drug solubility in the presence of SLS and structural descriptors is an important issue in the prediction and understanding of the solubilization mechanism. The aims of this study are: determination of experimental solubility of drugs in the presence of SLS and development of models for finding a relationship between solubilization factor by SLS and structural descriptors. Samples were prepared by adding excess amount of 19 drugs (with diverse structural and physicochemical properties) to water and an aqueous solution of SLS at different concentrations, that is, less than (0.1%) and above the CMC (0.5%). The mixtures were placed in a shaker-incubator for 72–96 h at 37 °C. Then, the equilibrated samples were filtered and analyzed at maximum wavelengths by UV-spectrophotometry and the concentrations were calculated based on the calibration curves. Afterward, the molecular descriptors of drugs were computed and their relationship with solubilization factor in the presence of SLS was investigated. Most of the drugs showed a considerable increase in solubility above the CMC (0.5%) of SLS. Therefore, the effective mechanism for solubilization by surfactants is the formation of micelles. On the other hand, a good correlation was observed between structural descriptors and solubilization power in the presence of surfactant. Overall, SLS is a good solubilization agent and the solubility in aqueous solution of SLS depends on various structural descriptors.
Evaluation of viscometric properties of carboxymethylcellulose and gellan J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Gustavo Monteiro da Silva, Rafael Fernandes Pinto da Rocha, Marcia Parente Melo da Costa, Ivana Lourenço de Mello Ferreira, Marcia Cerqueira Delpech
Viscometry is an inexpensive characterization method to obtain important information about the hydrodynamic volume and conformation of polymers in diluted solutions, in a determined solvent and specific temperature. The viscometric parameters can be mathematically calculated by graphical extrapolation or single-point determination. This article reports a viscometric study of two polysaccharides, carboxymethylcellulose (CMC) (degree of substitution = 2.23) and gellan (GL), with the use of two calculation methods, employing a series of six equations: Huggins, Kraemer and Schulz-Blaschke, by graphical extrapolation; and Schulz-Blaschke, Solomon-Ciuta and Deb-Chanterjee, by single-point determination. It is also used Wolf equations for a different way to determine the intrinsic viscosity. The solution for CMC analyses was NaCl 0.2 mol/L, and for gellan determination, the solvent applied was KCl 0.1 mol/L. For both polymers, the test temperature was 30 ± 0.1 °C. The average molar mass was also determinate by the viscometry analysis. The values of intrinsic viscosity of some constants indicated that the solvents systens used for CMC and for gellan, the solvents used are classified as a good system (kh + kk < 0.5). It was also observed that the method of calculation by a single-point determination was valid for both polyelectrolytes analyzed.
On the anomalous composition dependence of viscosity and surface tension in refrigerant blends J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Wael A. Fouad, Lourdes F. Vega
The Polar PC-SAFT equation of state coupled with DGT and excess entropy scaling was applied to predict the phase, interfacial and transport properties of refrigerant blends. Results show the presence of several thermophysical anomalies in systems under consideration. The literature has always linked aneotropic behavior at the interface (extrema in surface tension) to azeotropic behavior (extrema in vapor pressure) at the bulk. However, a minimum in surface tension as a function of composition was predicted in this work for R-32 + R-1234yf zeotropic mixture. The system also exhibits a significant positive excess volume in comparison to other R-32 binary mixtures. The latter phenomena indicate the presence of excessively weak intermolecular interactions between both species. Furthermore, a minimum in viscosity as a function of composition was predicted for R-32 + R-143a binary mixture. This was attributed to the homogenous distribution of charges found in both symmetrical molecules which leads to molecular repulsion and structure breaking. On contrary, a maximum in viscosity as a function of composition was predicted for R-32 + R-125 binary mixture. This was attributed to strong charge-charge interactions between the highly fluorinated R-125 molecule and R-32. The latter promotes structure making as evidenced by the system's negative excess volume. A maximum in the viscosity was also predicted for R-152a + R-1234ze(E) binary mixture. Aggregate formation is promoted in this system due to the strong charge-charge interaction between the unshielded fluorine atom in R-1234ze(E) and the undisturbed methyl group in R-152a.
In situ assembly of sulfur-doped carbon quantum dots surrounded iron(III) oxide nanocomposite; a novel electrocatalyst for highly sensitive detection of antipsychotic drug olanzapine J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Ganesan Muthusankar, Arumugam Sangili, Shen-Ming Chen, Rajendran Karkuzhali, Murugan Sethupathi, Gopalakrishnan Gopu, Selvam Karthick, Ramdhass Keerthika Devi, Nallathambi Sengottuvelan
Herein, we report the synthesis of sulfur-doped carbon quantum dots (S-CQDs) chemically incorporated with iron oxide nanoparticles (S-CQDs/Fe2O3) using hydrothermal synthesis strategy. The as-synthesized nanocomposite was characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscope, thermogravimetric analysis, and energy dispersive X-ray spectroscopy. We have analyzed the clear electrochemical kinetics of the S-CQDs/Fe2O3 nanocomposite modified glassy carbon electrode. Addition to this, electrochemical sensing property of S-CQDs/Fe2O3/GCE towards the detection of antipsychotic drug olanzapine (OLZ) was explored. Remarkably, S-CQDs/Fe2O3/GCE has shown the good electrocatalytic activity for OLZ oxidation and also exhibits a very low detection limit and sensitivity of about 0.006 μM and 0.88 μA μM−1 cm−2 respectively. Further, the proposed sensor has applied for the detection of OLZ in urine samples.
The improvement of the cationic/anionic surfactant interfacial activity via the selective host-guest recognition J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-17 Han Jia, Xu Leng, An Ma, Pan Huang, Hongyan Wu, Dexin Liu
Supramolecular chemistry proposed a controllable and convenient approach to construct the desired complexes used in various fields, including chemical enhanced oil recovery. β‑cyclodextrin (β-CD) can effectively enclose the surfactants to fabricate the stable inclusion complexes via the host-guest recognition. In the present report, the β‑CD effects on the interfacial activities of the mixed surfactant system consisting of N‑dodecyl‑N‑methylpyrrolidinium bromide (L12) and sodium dodecyl sulfate (SDS) were systematically evaluated. Interestingly, the additional β-CD molecules greatly reduced the interfacial tension (IFT) between the L12/SDS aqueous solution and model oil (toluene and n-decane, v/v = 1:1). Due to the electrostatic attraction of L12/SDS, the β-CD molecules could selectively enclose the majority surfactants to improve the intensive arrangements of mixed surfactants at the interface. In general, the host-guest recognition facilitates the fabrications of β-CD/surfactant inclusions and decrease surfactant interfacial concentrations. The competition between the host-guest recognition and the electrostatic attraction dominates the IFT variations. Then we changed the molar ratio of L12/SDS, the dissolved order of chemicals and explored the variations of the mixed surfactants hydrophile-lipophile balance to further confirm the proposed mechanism. Moreover, the salinity and temperature effects on the IFT were systematically investigated.
A molecular dynamics simulation scenario for studying solvent-mediated interactions of polymers and application to thermoresponse of poly(N-isopropylacrylamide) in water J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-10 Edder J. García, Debdip Bhandary, Martin T. Horsch, Hans Hasse
Studying equilibrium properties of polymers in solution by atomistic simulations is a challenging task as the available computation time is often not sufficient to ensure representative sampling of the phase space. One approach to tackle this problem is to create a simulation scenario which is simple enough to enable adequate sampling of equilibrium states while it retains the essential parts of the physics of the polymer in solution. In this work, we present and test such a scenario, which is designed for studying whether a given polymer will aggregate or dissolve in a given solvent. Two periodic polymer molecules are simulated in the explicit solvent. The distance d between the polymer chains lends itself as order parameter so that advanced sampling techniques, such as umbrella sampling, can be applied easily. A state corresponding to dissolved polymers (large d) and a state corresponding to aggregated polymers (small d) can be defined. The scenario misses the intramolecular collapse of the single chain, but it retains full atomistic detail regarding the polymer-solvent and the intermolecular polymer-polymer interactions. The thermoresponsive behavior of PNIPAM in water is studied with the new scenario, and it is shown that quantitative predictions of the experimental equilibrium data can be obtained after adjusting a single state-independent parameter in the force field.
Effect of ionic strength on solution and drilling fluid properties of ionic polysaccharides: A comparative study between Na-carboxymethylcellulose and Na-kappa-carrageenan responses J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-10 Liszt Y.C. Madruga, Paulo C.F. da Câmara, Nívia do N. Marques, Rosangela de C. Balaban
Natural polymers are widely used in different industries, mainly due to their hydrophilic features, which make it possible to solubilize them in water or absorb a large amount of it. Polysaccharides are the most widely used hydrophilic polymers, mainly because of their non-toxicity, biodegradability, compliance with environmental regulations and thickening behaviour in water. Knowledge of polymer performance in different aqueous media is essential to ensure optimal use in a desired application. In this study, the stability of sodium kappa-carrageenan and sodium carboxymethylcellulose stability was investigated in saline and basic aqueous media, as well as their applicability in drilling fluids. The ionic strength effects of the aqueous media containing Na+, Mg2+ and Ca2+ on the rheological properties of the polymer solutions were evaluated by varying the salt concentration, pH and temperature. The rheological properties and drilling fluid filtrate volume were evaluated by varying salt concentration and pH. The kappa-carrageenan solutions and drilling fluids were scarcely influenced by ion addition, at pH 7 to 10, even at higher salt concentrations, but highly influenced at pH > 11. On the other hand, carboxymethylcellulose solutions and their drilling fluids were more affected by the presence of salt and pH changes, with a greater decline in viscosity and increase in filtrate volume. This behaviour was interpreted as conformation adopted by the kappa-carrageenan chains in the presence of ions, indicating that this polymer is a good candidate for drilling fluids in oil well operations.
Role of a Tween 20-containing antifoaming agent in renaturation of foam-denatured pepsin during defoaming J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-10 Rui Li, Yunkang Chang, Yuran Zhang, Xiang'e Chen, Youshuang Zhu
The foam-induced enzyme denaturation, which often results in a large activity loss, is a common phenomenon in foam fractionation of enzymes. To reduce it effectively, we used a Tween 20-containing antifoaming agent to assist the renaturation of the enzyme molecules adsorbed at the gas-liquid interface during defoaming with pepsin as a model enzyme. We studied the roles of the antifoaming agent and its ingredients in renaturation of the adsorbed pepsin molecules. The results show that during defoaming, Tween 20 in the antifoaming agent was able to assist the adsorbed pepsin molecules to restore their native structures as soon as they were desorbed from the gas-liquid interface. The other ingredients, including polydimethylsiloxane, polyether L61 and aluminum silicate, did not affect the pepsin structure during defoaming. However, they enhanced the Tween 20-assisted renaturation of the adsorbed pepsin molecules by increasing the defoaming efficiency. Furthermore, the separation of the antifoaming agent from pepsin in the foamate had no significant effect on its specific activity. When the addition amount of the antifoaming agent in the foamate was 15.0‰ (v/v), almost all the adsorbed pepsin molecules were reactivated. Therefore, the foam-induced pepsin denaturation was reduced effectively without any changes of the foam fractionation process itself. The results are important to improve the performances of foam fractionation of enzymes.
Application of Zizyphus Lotuse - pulp of Jujube extract as green and promising corrosion inhibitor for copper in acidic medium J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-10 A. Jmiai, B. El Ibrahimi, A. Tara, M. Chadili, S. El Issami, O. Jbara, A. Khallaayoun, L. Bazzi
The study of the inhibitory power of the Pulp of Jujube (PJ) extract of the plant Zizyphus Lotus with respect to the corrosion of copper in 1 M hydrochloric medium has been realized. This study was conducted by stationary and transients electrochemical measurements, weight loss and atomic absorption spectroscopy techniques. Scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), Fourier transform infrared (FT-IR) and atomic force microscopy (AFM) studies were used to characterize the surface of uninhibited and inhibited copper specimens. The results showed that the inhibition increases with PJ extract concentration reaching a maximum of 93% at a concentration of 1 g L−1. The obtained results indicate that PJ extract can act as a good green corrosion inhibitor for copper in 1 M HCl. The effect of temperature was also investigated and thermodynamic parameters were determined and discussed.
Aggregation induced emission properties of new cyanopyridone derivatives J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-10 M.G. Swathi, T.N. Ahipa
Nowadays, fluorescent organic compounds have attracted much research interest due to their academic significance and applications. The present article deals with the fluorescence behaviors of conjugated cyanopyridone based compounds (CP1–5) possessing various donor/acceptor moieties. These compounds showed aggregation-induced emission (AIE) properties in their THF/H2O mixtures due to the restriction of intramolecular rotation and exhibited a blue emission behavior in their aggregated state. During the AIE study, compound (CP-1) showed a red shift in the emission profile and rest of the compounds exhibited a blue shift in their emission profile. Further, field emission scanning electron microscope (FESEM) and Epi-fluorescence microscopic studies showed that the stronger emission of these compounds is mainly due to the formation of large-sized aggregates in the THF/water mixture than the pure THF.
Catalytic reduction of picric acid, nitrophenols and organic azo dyes via green synthesized plant supported Ag nanoparticles J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-10 Muhammad Ismail, M.I. Khan, Sher Bahadar Khan, Kalsoom Akhtar, Murad Ali Khan, Abdullah M. Asiri
A facile and single-step green synthesis of silver nanoparticles dispersed on taro (Colocasia esculenta) plant rhizome powder (TP) is reported here. In the current study, we describe for the first time, the successful adsorption-based assembly of the silver/taro power (Ag/TP) nanocomposites using the rhizome of taro as a stabilizing agent. The Ag/TP nanocomposites exhibited very high efficiency in the catalytic reduction of nitroarenes such as picric acid/trinitrophenol (TNP), 4-nitroaniline (4-NA), 4-nitrophenol (4-NP) and 2-nitrophenol (2-NP) to the corresponding amines. The prepared catalyst also showed a high activity in the catalytic reduction of organic azo dyes such as Methyl Orange (MO), Congo Red (CR), Methyl Red (MR) and Rhodamine B (RhB) by NaBH4. The morphology, structure and crystallite size of the prepared nanocomposites were evaluated by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray photo electron spectroscopy (XPS) and X-ray diffraction analysis (XRD). The calculated turnover frequency was 3.846 min−1 for 4-NP and 1.104 min−1 for 2-NP. However, the pseudo-first-order constant was 5.27 × 10−3 s−1 for 4-NP and 1.23 × 10−3 s−1 for 2-NP. The prepared Ag/TP catalyst was also tested for the reduction of a mixture of nitroarenes and dyes. Ag/TP catalyst emerged as a promising, easily recoverable and reusable, with at least in 5 successive reactions and stable for 3 days.
Poly(N-isopropylmethacrylamide-acrylic acid) microgels as adsorbent for removal of toxic dyes from aqueous medium J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-11 Khalida Naseem, Zahoor H. Farooqi, Robina Begum, Maida Ghufran, Muhammad Zia Ur Rehman, Jawayria Najeeb, Ahmad Irfan, Abdullah G. Al-Sehemi
Poly(N-isopropylmethacrylamide-acrylic acid) [pniM-Ac] microgel particles were synthesized by surfactant free radical precipitation polymerization method. Microgel particles were used as adsorbent for the removal of toxic dyes such as Congo red (CR) (anionic), methylene blue (MB) (cationic) and Rhodamine B (Rh-B) (cationic) from aqueous medium at ambient temperature. Due to presence of carboxylate groups inside the polymer chains of microgel particles, uptake of cationic dyes such as MB and Rh-B was high as compared to anionic dye CR at low temperature and high pH of the medium. But at high temperature, microgel particles were shrunken and their hydrophobicity was increased. Under such conditions, uptake of anionic dye CR was high due to increased hydrophobic interaction between polymer chains of microgel particles and dye molecules. Effect of dye concentration, adsorbent dose, pH of the medium and agitation time on the percentage removal of dyes was also investigated and their optimum values were determined. Langmuir isotherm model best explained the adsorption of CR, MB and Rh-B on microgel particles. Pseudo second order has well explained the kinetics of adsorption of all dyes on microgel system as compared to other kinetic models as reflected by the values of regression coefficients (R2). Mechanism of adsorption of all dyes on microgel particles was explained by intra-particle diffusion model. Microgel particles also showed high capacity to extract toxic dyes simultaneously from aqueous medium as compared to their individual adsorption. Pure and dye loaded microgel particles were analyzed by UV–visible (UV–vis) spectroscopy and Fourier transform infrared (FTIR) spectrometry. Size and morphology of microgel particles were investigated by transmission electron microscopy (TEM).
Static magnetic field alters properties of confined alkylammonium nitrate ionic liquids J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-11 Andrei Filippov, Oleg I. Gnezdilov, Oleg N. Antzutkin
Ethylammonium nitrate (EAN) and propylammonium nitrate (PAN) ionic liquids confined between polar glass plates and exposed to a strong magnetic field of 9.4 T demonstrate gradually slowing diffusivity, a process that can be reversed by removing the sample from the magnetic field. The process can be described well by the Avrami equation, which is typical for autocatalytic (particularly, nucleation controlled) processes. The transition can be stopped by freezing the sample. Cooling and heating investigations showed differences in the freezing and melting behavior of the sample depending on whether it had been exposed to the magnetic field. After exposure to the magnetic field, the sample demonstrated decrease in the 1H NMR signal of residual water. 1H NMR spectroscopy with presaturation demonstrates that the most probable mechanism of the decrease of the bulk water signal is adsorption of water on polar surfaces of glass plates. Generally, our findings confirm our previous suggestion that alteration of the dynamic properties of confined alkylammonium nitrate ionic liquids exposed to a magnetic field is related to the alteration of real physical-chemical phases.
Surface dynamics associated with zinc oxide nanoparticles and biomolecules in presence of surfactants J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-11 Shruti G. Bhatkalkar, Dinesh Kumar, Ahmad Ali, Shilpee Sachar
This work reports the physicochemical parameters and the nature of association between Zinc oxide nanoparticles (ZnO NPs) and biomolecules viz., Bovine serum albumin (BSA) and Deoxyribonucleic acid (DNA) in presence of cationic, anionic and non-ionic surfactants. Zinc oxide nanoparticles are first synthesized using wet chemical method and subsequently characterized by FTIR, XRD, SEM, TEM and EDAX studies. The nanoparticle-protein interactions were studied using UV–vis spectroscopy, fluorescence spectroscopy, Dynamic light scattering studies, circular dichroism techniques and SDS-PAGE technique. The spectroscopic investigation sheds light into various aspects of binding during the molecular association of BSA with the ZnO NPs in absence and presence of cationic, anionic and non-ionic surfactants. The nanoparticles-DNA interactions were studied in presence and absence of surfactants by gel electrophoresis. Anionic and non-ionic surfactants were found to impart long-term stability to ZnO NPs. This study provides valuable mechanistic insights into the interactions taking place at the interface of the nanoparticles which further helps in designing stable colloidal ZnO NPs systems.
Vapor–liquid equilibrium for binary and ternary systems of tetrahydrofuran, ethyl acetate and N-methyl pyrrolidone at pressure 101.3 kPa J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-11 Jingwei Yang, Xiangshuai Pan, Mengxiao Yu, Peizhe Cui, Yixin Ma, Yinglong Wang, Jun Gao
Vapor−liquid equilibrium (VLE) data for the binary systems of tetrahydrofuran (THF) + ethyl acetate (EtOAc), THF + N-methyl pyrrolidone (NMP) and EtOAc + NMP, and the ternary systems of THF + EtOAc + NMP were measured at 101.3 kPa. The modified Rose vapor recirculating type equilibrium still was utilized to obtain the experimental data. The Herington method, as well as the Van Ness test, was used to verify the thermodynamic consistency of the experimental data. The NRTL model, UNIQUAC model and Wilson model were adopted to correlate the vapor-liquid equilibrium data. Accordingly, the binary interaction parameter for each model was obtained by regressing the experimental data. The results show that the three models can accurately agreement with the experimental data.
Converting CoS-TEA hybrid compound to CoS defective ultrathin nanosheets and their enhanced photocatalytic property J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-11 Win Thi Yein, Qun Wang, Jinzhu Wu, Xiaohong Wu
CoS ultrathin nanosheets with thickness of about 4.6 nm had been obtained through in-situ generated inorganic-organic hybrid CoS-TEA (TEA = triethanolamine) as self-sacrificial precursors. More importantly, defective ultrathin CoS nanosheets showed the boosted and faster visible light photocatalytic property i.e. 97.34% degradation of Rhodamine B (RhB) in 80 min as compared to CoS nanoplates prepared under the similar condition and the previous report. In addition, the enhanced photocatalytic activity originated from prolonged lifetime of photoinduced electron–hole pairs and faster interfacial charge transfer and RhB dye photodegradation reaction pathway has been revealed using photoelectrochemical and optical techniques.
Effect of natural and modified cyclodextrins on the excited state proton transfer of 7-hydroxy-4-methylcoumarin J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-11 A. Antony Muthu Prabhu, Madi Fatiha, B. Sivaraman, Maria Josefa Yáñez-Gascón, Horacio Pérez-Sánchez
Effect of natural and modified cyclodextrins on the absorption and 2D, 3D fluorescence spectra of 7‑hydroxy‑4‑methyl coumarin (HMC) have been investigated in different buffer solutions (pHs – 1.0, 6.5 and 10.0). Both neutral and monoanion species were formed in the ground state, whereas three species such as zwitterion, neutral and monoanion in the excited state in the above mentioned pH ranges. The excited state property of HMC obviously varied with the results from the absorption data. The excited state proton transfer was observed at low pH from the hydroxyl group to carbonyl group of HMC. FT-IR, PXRD, SEM results showed the apparent variation in the natural and modified CDs with the HMC molecule. The results demonstrated that in three pH solutions, HMC forms 1:1 inclusion complex with the three CDs. Finally the proposed structures of the inclusion complexes were predicted using Semi-empirical calculations.
Deciphering the anthelmintic activity of benzimidazolium salts by experimental and in-silico studies J. Mol. Liq. (IF 4.513) Pub Date : 2018-07-11 Prabodh Ranjan, Mohd Athar, Kari Vijayakrishna, L.K. Meena, R. Vasita, Prakash C. Jha
Inspired from the facts that majority of the drug administrated in the form of salts and “poison is in the dose”; herein, we have synthesized and characterized 1-methyl-3-alkylbenzimidazolium and 1-methyl-3-alkylimidazolium derived ionic salts with varying N-alkyl chains and different anions. These ionic salts were evaluated for their vermicidal activity (VA) and cell viability test against the Pheretima posthuma and A549 cell lines (human alveolar basal epithelial cells), respectively. The morphological changes in the test organism were visualized by the Scanning Electron Spectroscopy (SEM) to get the mechanistic insight. Furthermore, results were compared with VA of 1-methyl-3-alkylimidazolium derivatives to establish their structure-activity-relationship (SAR) of the fused benzene ring in 1-methyl-3-alkylimidazolium. The current findings suggested that the activity of these salts depend on the nature of N-alkyl side-chain, anionic moieties, varying charge on quaternary nitrogen (due to different anions) lipophilicity and types of cationic core fused with imidazolium ring. These findings were complemented by the quantitative-structure-activity-relationship, molecular docking approaches to unfold the features accountable for their activities and binding patterns of the ligand-receptor complex respectively. ADME/T assessment of the ionic salts shows that all fifteen compounds qualified the ADMET profiling test (that means they exhibit drug-likeness features).
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