Electron Viscosity Research Articles

Magnetohydrodynamics and electron-electron interaction of massless Dirac fermions

The magnetotransport properties of massless Dirac fermions in a gapless HgTe quantum well are investigated. In samples with narrow channels, a large negative magnetoresistance with a Lorentzian profile is observed, which is interpreted as a manifestation of electron viscosity due to electron-electron interaction. Comparison of experiment with theory yields the shear stress relaxation time of the Dirac fermions caused by electron-electron scattering.

Formulation and characterization of curcumin-loaded microemulsions: Evaluation of antioxidant stability and in vitro release

In this study, oil-in-water (O/W) and water-in-oil-in-water (W/O/W) microemulsions (MEs) were synthesized as the carrier for curcumin delivery as a means to improve water solubility and antioxidative stability. MEs were characterized by measuring particle size, polydispersity index (PDI), transmission electron microscope, viscosity, and electrical conductivity. Furthermore, the position of curcumin in MEs was probed by proton nuclear magnetic resonance spectroscopy (1H NMR), and MEs antioxidant capacity and in vitro release of curcumin were investigated. Curcumin-loaded MEs were constituted of spherical droplets with a mean particle size of 10.0–20.0 nm and PDI of 0.2–0.3. 1H NMR confirmed that curcumin is embedded in the inner structure of MEs. Collectively, MEs synthesized in this study were shown to extremely improve solubility of curcumin. Furthermore, assessment of in vitro release and storage stability of the two experimentally-synthesized MEs showed that W/O/W ME had greater sustained release and antioxidant activity compared to O/W ME. No significant differences between storage at 4 °C and 25 °C were observed for the two evaluated ME. Our work illustrated that O/W and W/O/W MEs were well qualified for the delivery of curcumin.

Synthesis, characterization, DFT calculation, DNA binding and antimicrobial activities of metal complexes of dimedone arylhydrazone

The diazotization, coupling and metallization process was employed to create hydrazone chelating ligand (HL) and its Co(II), Cu(II) and Ni(II) complexes. Elemental analysis, FT-IR, UV–visible, thermal analysis, 1H NMR, and 13C NMR were utilized to propose their structures. The reaction between metal (II) with HL produced mononuclear complexes and the molar conductivity results demonstrated that the complexes are all non-electrolytes that fall within a certain range 8–12 Ω−1 cm2 mol−1. Co(II) and Ni(II) complexes have pseudooctahedral coordination geometry, whereas Cu(II) complexes have square planar coordination geometry. The metal ion interacts with the ligand. as a monobasic bidentate by (CO) as well as deprotonating hydrazone moiety (NH). Besides, the optimized structure, bond lengths, and angles of the ligand and its complexes determined quantum chemical parameters were estimated by molecular modeling. Electronic absorption dilution and viscosity analysis techniques were used to study the compounds' DNA binding activities. With a binding constant in the 5.13 × 105 M−1 range. The results revealed that the complexes bind to CT-DNA in grooves followed by partial incorporation of the ligand between the DNA base stacks. The cytotoxicity of the new complexes was examined versus human carcinoma cell lines, HepG-2 & MCF-7, and compared to positive controls as vinblastine and colchicine. The DPPH free radical-scavenging assay was used to evaluate the anti-oxidant capacity of all compounds in-vitro. Finally, the antimicrobial activities of the complexes against fungal (Candida albicans), gram negative bacteria (Escherichia coli), and gram positive bacteria (Escherichia coli) were investigated using the disc-diffusion process (Staphylococcus aureus).

High Performance Aqueous Li-Ion Flow Capacitor Realized Through Microstructure Design of Suspension Electrode.

Suspension electrode is the core of flowable electrochemical energy storage systems, which are considered suitable for large-scale energy storage. Nevertheless, obtaining suspension electrodes with both low viscosity and high conductivity is still a big challenge. In present work, spinel LiMn2O4 was chosen as an example to make suspension with low viscosity and high conductivity through microstructure morphology control of solid particles and the contact mode between active materials and conductive additives in suspension electrode. By coating a thin layer of polyaniline on the surface of spherical spinel LiMn2O4, the resulting suspension showed much higher electronic conductivity (about 10 times) and lower viscosity (about 4.5 times) as compared to irregular and bare spinel LiMn2O4-based suspension counterpart. As a result, the Li-ion flow capacitor based on LiMn2O4 and activated carbon suspensions exhibited a record energy density of 27.4 W h L−1 at a power density of 22.5 W L−1 under static condition to date, and can be smoothly work under an intermittent-flow mode. The strategy reported in this work is an effective way for obtaining suspension electrodes with low viscosity and high electronic conductivity simultaneously. It can not only be used in the flow capacitors, but also can be extended to other flowable electrochemical energy storage systems.

PROCESSING AND CHARACTERIZATION OF ECO-FRIENDLY CUTTING FLUID WITH NANO ADDITIVES FOR TURNING OPERATION

Machining quality depends on numerous factors such as speed, feed rate, quality of the materials, the cutting fluids used and so on. The quality of machining components can also be improved by using appropriate cutting fluids. In this study, the three different types of eco-friendly cutting fluids based on coconut oil with nano boric acid particles were synthesized with nanoadditives and characterized during the lathe-turning operation of mild steel. The obtained results were compared between the dry/plain turning (without the cutting fluid) and the turning with the cutting fluids like coconut oil and mineral oil with nanoparticles. In industries, a wide variety of cutting fluids are used; however, most of these cutting fluids are made up of synthetic materials which may affect the environment significantly. Hence, it is essential to develop eco-friendly cutting fluids for environmental sustainability. Here, the cutting fluids were characterized by the morphological study on nanoparticles (400[Formula: see text]nm) and the machined surface using scanning electron microscope (SEM), viscosity test, flash and fire point, surface roughness on machined part, tool tip-workpiece interface temperature, cutting force and flank wear measurement. The results showed that cutting fluids with 0.5% of boric acid had better performance.

Effects of cationic modifier type on the structure and morphology of organo-montmorillonite and its application properties in a high-temperature white oil system

Three types (eight modifiers with three radical groups) of cationic modifiers aliphatic quaternary ammonium salts (AlQAS), aromatic quaternary ammonium salts (ArQAS), and polyoxyethylene quaternary ammonium salts (PoQAS), were used to modify montmorillonite (Mt) and prepare cationic-organo-montmorillonites (COMt). COMt was characterized by X-ray diffraction, scanning electron microscopy, contact angle, thermogravimetry, optical microscopy, gel volume, viscosity, and thixotropy to explore modifier type effects on the structure, morphology, and properties of COMt, as well as investigate the application properties in white oil system. The results show that eight cationic modifiers all entered the Mt. layer to form intercalated COMt. The modifier type significantly influences the structure, morphology, and properties of the obtained COMt and the application properties in white oil system. The basal spacing of PoQAS COMt (d001 = 4.33 nm ~ 5.28 nm) was the larger than ArQAS COMt (d001 = 3.14 nm ~ 3.60 nm) and AlQAS COMt (d001 = 2.91 nm ~ 3.66 nm). The morphologies of the three types of COMt lamella were all in a loose state. The order of COMt lamellar loosening degree with the same chain length was PoQAS COMt > ArQAS COMt > AlQAS COMt. The thermal stability and lipophilicity of the COMt powders were consistent with the morphology results. In the white oil system at 180 °C, XRD results showed that the thermal stability of PoQAS COMt was the best (maintaining the structure of PoQAS COMt and no Mt. generation), followed by ArQAS COMt, and AlQAS COMt had the worst thermal stability. The viscosity and thixotropy of three types COMt was ArQAS COMt better than PoQAS COMt and AlQAS COMt, PoQAS COMt better than AlQAS COMt. Research also showed that the steric hindrance, electropositivity of the modifier molecule, and modifiers' thermal stability are positively related to the thermal stability of COMt in white oil. This work provides a basis and other ideas in understanding the relationships between radical groups types, the structures of quaternary ammonium salts, the thermal stability of COMt, and selecting and developing new modifiers.

Development and characterization of nano-emulsions and nano-emulgels for transdermal delivery of statins

ABSTRACT Background Oral administration of statins for the treatment of familial hypercholesterolemia results in poor therapeutic outcomes and patient compliance. An alternative administration route is proposed to circumvent the current limitations. This research is aimed at developing nano-emulsions and nano-emulgels as the ultimate potential delivery systems of statins for administration via the transdermal route. Methods Oil-in-water (o/w) nano-formulations (nano-emulsions and nano-emulgels) containing 2% (w/w) of the selected statin and 8% apricot kernel oil as oil phase were formulated. The nano-formulations were characterized using transmission electron microscopy (TEM), pH, viscosity, droplet size and zeta-potential. Results Nano-emulsions’ and nano-emulgels’ droplet size ranged between 114.23–169.83 nm and 149.83–267.53 nm, respectively. The addition of Carbopol® Ultrez 20 increased the nano-emulsions’ viscosity (3.59–8.38 cP) resulting in the formation of nano-emulgels (viscosity: 1911.00–46,090.00 cP). The entrapment efficiency (90.77–99.55%) confirmed the incorporation of the statins. Membrane release studies indicated that statins were released at higher flux values in nano-emulsions compared to their respective nano-emulgels. Ex vivo (skin diffusion) studies indicated higher median values in the nano-emulgels compared to their nano-emulsion counterparts. Conclusions The results indicate the benefits of nano-emulsions and nano-emulgels as potential alternative delivery systems for the transdermal delivery of statins.

Synthesis, Characterization and DNA Binding Studies of Some Hydrazide Derivatives Schiff Base Metal Complexes of Mn(II), Co(II/III), Ni(II), Cu(II) and Zn(II) Metal Ions

Eighteen metal complexes were synthesized by using four different Schiff base ligands, (1E)-1-((6-methyl-4-oxo-4H-chromen-3-yl)methylene)carbohydrazide (L1), 6-[2-(salicylidene)hydrazinyl]-N′-(salicylidene)nicotinohydrazide (HL2), 6-hydrazinyl-N′-(6-methyl- 4-oxo-4H-chromen-3-yl-methylene)nicotinohydrazide (HL3) and (E)-6-hydrazinyl-N′-(1-(2,3-dihydro- 1,3-dioxo-1H-inden-2-yl)-ethylidene)pyridine-3-carbohydrazide (L4). Characterization of the metal complexes were carried out by using various physico-chemical techniques. Complexes 1, 3, 4, 6, 11, 14, 15, 16, 17 and 18 have been found octahedral structures while the metal complexes 2, 5, 8, 10 and 13 have tetrahedral structures. And, complexes 7, 9 and 12 have square planar structures. Thermal study has revealed the presence of lattice and coordinated water molecules in the complexes. From powder X-ray diffraction study, it was suggested that a monoclinic system for complexes 2 and 14 while a triclinic system for the complexes 3, 4, 5, 9, 11, 13 and 15. The interaction of the ligands and their metal complexes with calf thymus DNA (CT-DNA) has been studied by electronic absorption, cyclic voltammetry and viscosity methods.

Viscosity of two-dimensional electrons

The hydrodynamic regime of electron transport has been recently realized in conductors with ultra-low densities of defects. Although relaxation processes in two-dimensional (2D) fluids have been studied in many theoretical works, the viscosity of the realistic Fermi gas of 2D electrons having the quadratic energy spectrum and interacting by Coulomb's law has not been reliably determined either in theory or in experiment up to now. Here we construct a theory of viscosity and thermal conductivity in such system. We compare the calculated viscosity of the 2D electron Fermi gas and the previously known viscosity of a 2D Fermi liquid with available experimental data extracted from the hydrodynamic negative magnetoresistance of the best-quality GaAs quantum wells. Based on this comparison, we argue that measurements of the temperature dependence of the viscosity can allow to trace the transition between an electron Fermi liquid and a Fermi gas.

Synthesis, characterization, ADMET, in vitro and in vivo studies of mixed ligand metal complexes from a curcumin Schiff base and lawsone

Complexes are currently synthesized from plant origin because of their therapeutic effect against certain diseases with toxicity. Hence, in this work, four new transition metal(II) mixed ligand complexes have been synthesized using a curcumin Schiff base (primary ligand) and lawsone (as co-ligand). The geometry of these complexes was explored by elemental analyses, molar conductance, thermal analysis, magnetic moment values, IR, NMR, Mass, electronic and EPR spectral studies. Electronic absorption titrations, viscosity measurements and molecular docking studies reveal that all the metal complexes interact with the CT DNA by groove binding. Among all the complexes, the copper(II) complex (complex 1) exhibits a higher Kb value (3.5 × 10−4 M) which reveals that it has a strong binding efficiency toward the CT DNA. The complexes also possess strong DNA cleavage efficiency. Cytotoxicity investigations on Artemia salina show that all the complexes possess higher cytotoxic effect than the ligand. Moreover, all the metal complexes have better antimicrobial efficacy than the ligand. Swiss ADME, PASS and pkCSM online softwares are helpful to predict the pharmacokinetic and biological actions of the curcumin Schiff base. Theoretical results obtained from the in silico study are experimentally corroborated by in vivo anti-inflammatory screening study. All the above studies demonstrate that the copper complex possesses biological activity similar to that of the drug like molecules. Research Highlights Synthesis and characterization of four novel transition mixed ligand complexes using plant moieties Promising in vivo anti-inflammatory agents and in vitro DNA metallonucleases Cytotoxicity investigation on Artemia salina Higher cytotoxic effect for the complexes than the ligand Identification of copper(II) complex as lead like molecule among all

Antioxidant, antimicrobial, DNA binding and cleavage studies of novel Co(II), Ni(II) and Cu(II) complexes of N, O donor Schiff bases: Synthesis and spectral characterization

A series of bivalent metal complexes M(L1)2 and M(L2)2 where M = Cu(II), Ni(II), Co(II) and HL1=2-((E)-(4-(trifluoromethoxy)phenylimino)methyl)-4-chlorophenol, HL2=2-((E)-(4-(trifluoromethoxy)phenylimino)methyl)-4-nitrophenol were synthesized and characterized by elemental analysis, SEM, Mass, 1H NMR, 13C NMR, UV–Vis, FT-IR, ESR and magnetic susceptibility measurements. Based on the analytical and spectral data a square planar geometry has been assigned to all the metal complexes. DNA binding properties of these complexes have been explored using electronic absorption spectroscopy, fluorescence spectroscopy and viscosity measurements. The experimental evidence indicated that these binary complexes strongly bind to calf thymus DNA through an intercalation method. DNA cleavage efficacy of these metal(II) complexes have been investigated with super-coiled pBR322 DNA by gel electrophoresis in presence of H2O2 and UV light, and found that all complexes showed better nuclease activity. The in vitro antimicrobial activity results by paper disc method against few bacterial pathogens such as Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus as well as fungal species Aspergillus niger and Candida albicans showed that the complexes are more biocidal than free ligands. Further, the compounds were screened for antioxidant activity using 1,1-diphenyl-2-picryl hydrazyl (DPPH) which was compared with a standard drug ascorbic acid.

Preparation and Characterization of Rutile Titania Nanofluids Stabilized in Different Surfactants Base Fluids

Background: Improvement of conventional heat transfer fluids for achieving higher energy efficiencies in thermal equipment is a key parameter to conserve energy in industries. The heat transfer fluids such as water, oil and ethylene glycol greatly suffer low heat transfer performance in industrial processes. There is a need to develop new types of heat transfer fluids that are more effective in terms of heat transfer performance. Nanofluids enhance thermal conductivity and improve the thermal performance of heat transfer systems. Methods: New titania nanofluid samples consisting of 0.0625 to 1% TiO2 nanoparticles were prepared and characterized. The method of preparation was based on prior precipitation of TiO2 from an ammoniacal solution of pH 9 and calcination at 900°C. Solubilization, homogenization and stabilization of the of the nanoparticles were performed by sonication in the presence of sodium dodecyl sulfate (SDS) anionic surfactant and cetyltrimethylammonium bromide (CTAB) cationic surfactant. Results: This treatment was also utilized to increase the stability and improve the thermal properties of the fluid. Conclusion: Several characterization techniques including measurements of hydrodynamic size distribution, zeta potential, transmission electron microscopy (TEM), viscosity, density, specific heat, thermal conductivity, and sedimentation photo capturing were used to measure and confirm the stability and sedimentation rate of the prepared nanofluids.

Non-Linear Optical Property and Biological Assays of Therapeutic Potentials Under In Vitro Conditions of Pd(II), Ag(I) and Cu(II) Complexes of 5-Diethyl amino-2-({2-[(2-hydroxy-Benzylidene)-amino]-phenylimino}-methyl)-phenol.

Herein, we report facile procedures for synthesis of a new Schiff base ligand (H2L,5-Diethylamino-2-({2-[(2-hydroxy-benzylidene)-amino]-phenylimino}-methyl)-phenol) and its Ag(I), Pd(II) and Cu(II) complexes. The structure of the H2L ligand as well as its metal complexes was deduced based on wide range of analytical, structural and spectroscopic tools, along with theoretical evidence via density functional theory (DFT) calculations. The obtained results indicated that the Schiff base (H2L) ligand acts as a tetradentate N2O2 donor with two azomethine nitrogen’s (N1, N2) and two deprotonated phenolic oxygens (O1, O2) atoms. A distorted octahedral structure is assigned to [CuL(OH2)2]·3/2H2O complex and square planar structure for PdL and AgL complexes. The electronic structure and non-linear optical (NLO) property of the prepared compounds were discussed theoretically by the B3LYP/GENECP program. Results revealed that all complexes have non-planner geometries as indicated from the dihedral angles. The charge transfer occurs within the synthesized complexes as indicated from the calculated energy gap between HOMO and LUMO energies. The H2L ligand and its complexes are excellent candidates for NLO materials as implied from their hyperpolarizabilities and polarizabilities values. The biological activities of the prepared complexes against selected microorganisms and cancer cell lines gave good growth inhibitory effect. The biocidal potencies of the ligand and its complexes can be arranged as follows: AgL > CuL > PdL > H2L, as compared to the used standard drugs. The antiproliferative activity of the studied complexes against different carcinoma cell lines such as liver (Hep-G2), breast (MCF-7) and colon (HCT-116) followed the order H2L < AgL< PdL < CuL < vinblastine. Probing the binding interactions of prepared complexes with calf thymus (CT)-DNA using electronic absorption, gel electrophoresis and viscosity measurements revealed strong interaction via intercalation modes, as also evidenced by their molecular docking study.

Insoluble dietary fibre from okara (soybean residue) modified by yeast Kluyveromyces marxianus

Insoluble dietary fibre (IDF) accounts for more than 90% of the total dietary fibre in okara and has the potential as a functional ingredient. However, IDF in raw okara has some disadvantages when used in food industries so its modification is needed. This paper focused on IDF in okara modified by fermentation by Kluyveromyces marxianus. Two kinds of modified IDFs, namely, MIDF1 and MIDF2, were obtained through simple fermentation and the combination of fermentation and β-glucosidase hydrolysis at home. The purity of IDF ranged from 75.83 (OIDF) to 81.0 (MIDF1) and 87.70 g/100 g (MIDF2). Colour analysis, scanning electron micrographs, bulk density and viscosity showed positive effects for modification. The functional properties of SC, WHC, OHC, GAC and CAC in MIDF were all increased in modified IDF, but MIDF2 showed a more favourable effect than MIDF1. Overall, the research demonstrated that K. marxianus fermentation can improve the structure and function of IDF from okara, which provides guidance for the development and utilization of okara in the food industry.

Electron hydrodynamics in anisotropic materials

Rotational invariance strongly constrains the viscosity tensor of classical fluids. When this symmetry is broken in anisotropic materials a wide array of novel phenomena become possible. We explore electron fluid behaviors arising from the most general viscosity tensors in two and three dimensions, constrained only thermodynamics and crystal symmetries. We find nontrivial behaviors in both two- and three-dimensional materials, including imprints of the crystal symmetry on the large-scale flow pattern. Breaking time-reversal symmetry introduces a non-dissipative Hall component to the viscosity tensor, and while this vanishes for 3D isotropic systems we show it need not for anisotropic materials. Further, for such systems we find that the electronic fluid stress can couple to the vorticity without breaking time-reversal symmetry. Our work demonstrates the anomalous landscape for electron hydrodynamics in systems beyond graphene, and presents experimental geometries to quantify the effects of electronic viscosity.

Splitting shock heating between ions and electrons in an ionized gas

When a shock passes through an ionized plasma, a question exists about how much of the shock energy should go to the ions and how much should go to the electrons. Until recently, we have used the simplest possible model (based on Zel’dovich and Raizer [1], dumping all of the shock energy into the ions and ignoring the electronic fluid completely. However, we have become aware of work from the early 2000’s by Velikovich et al. [2] that has convinced us that a more sophisticated approach can be worthwhile in problems that involve ionization of elements with atomic number (Z) as low as five or six.We describe an approach for splitting the shock energy according to the values of ion and electron viscosity. We examine several calculations to explore the difference between our previous approach and our new one. Finally, we conclude with a brief discussion of when ion/electron shock heat splitting will matter and when it will not, along with some ideas for future research.

Manifestations of classical size effect and electronic viscosity in the magnetoresistance of narrow two-dimensional conductors: Theory and experiment

We develop a classical kinetic theory of magnetotransport of 2D electrons in narrow channels with partly diffusive boundary scattering and apply it to description of magnetoresistance measured in the temperature interval 4.2-30 K in long mesoscopic bars fabricated from high-purity GaAs quantum well structures. Both experiment and theory demonstrate a number of characteristic features in the longitudinal and Hall resistances caused by the size effect in two dimensions owing to the high ballisticity of the transport. In addition to the features described previously, we also reveal a change in the slope of the first derivative of magnetoresistance when the cyclotron orbit diameter equals to half of the channel width. These features are suppressed with increasing temperature as a result of the electronic viscosity due to electron-electron interaction. By comparing theory and experiment, we determine the characteristic time of relaxation of angular distribution of electrons caused by electron-electron scattering.

Novel dibenzoxanthenes compounds inhibit human gastric cancer SGC-7901 cell growth by apoptosis

In our previous work, we have synthesized a series of dibenzoxanthenes which showed antitumor activity. However the antiproliferation ability toward gastric cancer cells and the mechanism still is not known. Three new dibenzoxanthenes were synthesized by oxidized the binaphthol in this study. We studied the interaction between compounds and Calf thymus (CT-DNA) by electronic absorption titration, luminescence spectra, viscosity experiments and DFT computation. The mode of compounds binding with DNA was intercalation. We demonstrated that compounds inhibited the proliferation of gastric cancer cells by MTT assay. The antitumor effect of these compounds was triggered by S phase cell cycle arrest and induced the apoptosis of cells. The mitochondrial pathway of apoptosis was confirmed by the loss of mitochondrial membrane potential, the release of cyto C, the decrease expression of Bcl-2 protein and the increase expression of cleaved PARP, Bax, Bid, Bad proteins. Compounds also enhanced the concentration of calcium and ROS in SGC-7901 cells. All the above results indicated that compounds 4a-4c strongly suppressed the proliferation of gastric cancer cells via inducing cell cycle arrest and cell apoptosis, suggesting that compounds are potential novel therapeutic agents for gastric cancer.

Synthesis, DFT calculation, DNA-binding, antimicrobial, cytotoxic and molecular docking studies on new complexes VO(II), Fe(III), Co(II), Ni(II) and Cu(II) of pyridine Schiff base ligand

A new H2L ligand (6, 6′-(pyridine-2, 6-diylbis(azan-1-yl-1-ylidene))bis(methan-1-yl-1-ylidene)bis(2-ethoxyphenol) was obtained from the reaction of 2, 6- diamino pyridine and 3- ethoxy salicyaldehyde in 1:2 molar ratio and fully characterized using elemental analyses and spectroscopic tools. The reaction of a ligand with the different metal salts yields five new complexes CuL, CoL, NiL, FeL, and VOL. The new complexes were identified according to the results of elemental analyses, IR and UV–vis spectra, magnetic moment, molar conductance and thermal analyses (TGA). From the conductivity data, it is deduced that all complexes are non-electrolytes. FT-IR spectra displayed that the Schiff base ligand coordinated to the metal ions in a manner with ONNO donor sites, the nitrogen atom of the pyridine ring, the nitrogen of one azomethine group and two oxygen atoms of the two phenolic OH groups. The results of electronic spectra and magnetic susceptibility confirmed octahedral geometry of FeL complex and square pyramidal geometry for CoL, CuL and VOL and square planar for NiL. The electronic structure of H2L ligand and its complexes were investigated theoretically at the DFT-B3LYP-311 G** level of the theory. FT-IR spectra established the involvement of pyridine nitrogen in the coordination process. The presence of coordinated water molecules inside the coordination sphere of the complexes CoL, CuL and FeL are supported by TGA studies. The antimicrobial activities of the ligand and its complexes were determined against two Gram-positive bacteria (B. subtitles and S. aureus) and two Gram-negative (E. coli and P. vulgaris) and two fungus (Candida albicans and Aspergilla’s fumigates). The results showed that the complexes behaved as better antimicrobial agents than the ligand, VOL complex shows exceptional antimicrobial efficacy. The order of increasing the antibacterial and antifungal potency is H2L < NiL < CuL < CoL < FeL < VOL. The binding of the complexes with CT-DNA was followed using electronic absorption, viscosity and gel-electrophoresis measurements. These studies confirmed that the complexes bind to CT-DNA through a groove binding mode with certain affinities (Kb = 6.25 × 105, 5.50 × 105, 3.20 × 105, 2.50 × 105 and 1.52 × 105 for CuL, FeL, VOL, NiL, and CoL respectively). Moreover, cytotoxic effect against hepatocellular carcinoma cell line (HEP-G2) was screened. The IC50 values of the ligand and complexes suggest that the compounds possess very good cytotoxic activity and follow the order: CuL >FeL>VOL>NiL>CoL > H2L. These results strongly agree with results of binding constant of CT-DNA with different metal complexes.

Control of electron-electron interaction in graphene by proximity screening

Electron-electron interactions play a critical role in many condensed matter phenomena, and it is tempting to find a way to control them by changing the interactions’ strength. One possible approach is to place a studied system in proximity of a metal, which induces additional screening and hence suppresses electron interactions. Here, using devices with atomically-thin gate dielectrics and atomically-flat metallic gates, we measure the electron-electron scattering length in graphene and report qualitative deviations from the standard behavior. The changes induced by screening become important only at gate dielectric thicknesses of a few nm, much smaller than a typical separation between electrons. Our theoretical analysis agrees well with the scattering rates extracted from measurements of electron viscosity in monolayer graphene and of umklapp electron-electron scattering in graphene superlattices. The results provide a guidance for future attempts to achieve proximity screening of many-body phenomena in two-dimensional systems.