Maximum Negative Charge Research Articles

In vitro Function Study of Different Negative Charge Pullulan Nanoparticles for Sentinel Lymph Node Angiography.

Many dyes or radioactive markers used for sentinel lymph node (SLN) have the shortcomings of false positive and radiation injury. Indocyanine green (ICG) seems to have a lower false positive rate and tissue damage, without a clear field of vision during the operation. For the shortcomings, we successfully synthesized three anionic pullulan materials, changed the degree of hydrophobic for size controlling (< 50nm) to prepare CHP nanoparticles (NPs) and changed the succinyl degree to prepare CHPC NPs with different negative surface potential. The size of those NPs were less than 50nm under (transmission electron microscope) TEM, with hydrodynamic size of 90.67 ± 2.2 nm of CHP, 105.8 ± 1.7 nm of CHPC1 and 115.9 ± 2.3 nm of CHPC2. Moreover, the Zeta potential of CHP, CHPC1 and CHPC2 were -1.9 ± 0.2 mV, -9.6 ± 0.3 mV and -19.4 ± 0.7 mV. The size of ICG-loading CHP, CHPC1 and CHPC2 NPs increased to 109.4 ± 2.7 nm, 113.8 ± 1.2 nm and 30.6 ± 3.5 nm, as the zeta potential decreased to -2.7 ± 0.4 mV, -12.5 ± 1.6 mV and -23.1 ± 1.2 mV. With the increasing degree of succinyl, the size increased and the zeta potential decreased. At the same time, the higher degree of succinyl drug-loading NPs have lower release and have increased the stability of ICG. We found that the blank-NPs had no significant toxicity to normal cells (HSF), as the ICG@CHP group had larger toxicity than the CHPCs and control. Moreover, the cellular uptake was decreased with the increased degree of succinyl. In this study, we successfully prepared CHPC2 carriers with the maximum negative surface charge, for follow-up research and providing new ideas for SLN.

Adsorption Behavior of Toxic Carbon Dichalcogenides (CX2; X = O, S, or Se) on β12 Borophene and Pristine Graphene Sheets: A DFT Study.

The adsorption of toxic carbon dichalcogenides (CX2; X = O, S, or Se) on β12 borophene (β12) and pristine graphene (GN) sheets was comparatively investigated. Vertical and parallel configurations of CX2⋯β12/GN complexes were studied herein via density functional theory (DFT) calculations. Energetic quantities confirmed that the adsorption process in the case of the parallel configuration was more desirable than that in the vertical analog and showed values up to −10.96 kcal/mol. The strength of the CX2⋯β12/GN complexes decreased in the order CSe2 > CS2 > CO2, indicating that β12 and GN sheets showed significant selectivity for the CSe2 molecule with superb potentiality for β12 sheets. Bader charge transfer analysis revealed that the CO2⋯β12/GN complexes in the parallel configuration had the maximum negative charge transfer values, up to −0.0304 e, outlining the electron-donating character of CO2. The CS2 and CSe2 molecules frequently exhibited dual behavior as electron donors in the vertical configuration and acceptors in the parallel one. Band structure results addressed some differences observed for the electronic structures of the pure β12 and GN sheets after the adsorption process, especially in the parallel configuration compared with the vertical one. According to the results of the density of states, new peaks were observed after adsorbing CX2 molecules on the studied 2D sheets. These results form a fundamental basis for future studies pertaining to applications of β12 and GN sheets for detecting toxic carbon dichalcogenides.

Methylene blue adsorption on thermo plasma expanded graphite in a multilayer column system

The removal of dyes from wastewater is an important topic in environmental applications. Methylene blue (MB) is one of the most worrisome compounds, as it is widespread and used in many industrial activities. Adsorption represents an effective technique for the removal of this contaminant. Thermo plasma expanded graphite (TPEG) is an industrial material characterized by a fibrous morphology, a very low density and overlapped graphene layers. TPEG has a higher specific surface compared to conventional thermo-expanded graphite and it can establish effective attractive forces with charged pollutants. These properties make TPEG a very promising adsorbent material.In the present work, TPEG was tested in an innovative multilayer column system to treat MB contaminated solutions. Several batch experiments were carried out by varying pH, initial MB concentration and temperature.The optimal adsorption performance was assessed at pH 11, around which the TPEG assumed the maximum negative charge. Based on these results, the adsorption mechanism appeared to be related mainly to electrostatic interactions. At room temperature, the greatest amount of MB adsorbed on TPEG was detected by treating solutions with an initial concentration of 30 mgMB/L. The temperature increase from 20 to 40 °C caused an enhanced adsorption capacity when concentrations higher than 10 mgMB/L were treated. The adsorption trends were accurately described by a pseudo-second order kinetic law and the adsorption isotherms at 20 and 40 °C were found to follow both the features of Freundlich and Langmuir models. The adsorption capacity was estimated to reach threshold values around 95 mgMB/gTPEG and 265 mgMB/gTPEG at 20 and 40°C, respectively. The Gibbs energy change (ΔG°) was calculated to about −7.80 kJ/mol, which proved that the process is spontaneous from a thermodynamic point of view. Finally, it was verified that TPEG can be efficiently reused 5 times after a simple chemical regeneration phase with HCl.

Complete Prevention of Contact Electrification by Molecular Engineering

Summary Electrostatic charges are easily generated on surfaces during contact electrification. Although these invisible charges have emerged as a new dimension in mediating the functions of surfaces, such as energy conversion, liquid transport, reactivity, and adsorbability, the accumulation of charges on surfaces can also pose many undesirable consequences. Despite notable progress, existing approaches in engineering antistatic surfaces suffer from limitations such as the need to modify bulk materials or for delicate control of patterning on surfaces that rely on the neutralization of generated charges. Herein, we report a general toolbox for designing antistatic coatings by leveraging on chemically heterogeneous components with electron-donating and electron-accepting functions, i.e., N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and 1H,1H,2H,2H-perfluorooctyl trimethoxysilane, to molecularly engineer the surface potential to achieve an electrostatic homogeneity and completely prevent charge generation. Our approach is general, which allows the facile fabrication of antistatic coatings on various materials, even flexible and curved, with good re-writability and transparency.

Electrophysical Parameters of Plasma with a Charged Dust Cloud

The parameters of a low-pressure glow discharge in neon with solid microparticles are experimentally and numerically studied in order to determine the region of the existence of charged dust clouds that most strongly affect the electrophysical parameters of a gas-discharge plasma in neon. It is shown that dust clouds with the maximum total negative charge are formed at the average electron density of 108 cm–3 over the volume of the discharge. The obtained values of the plasma parameters with dust clouds are close to the values characteristic of the disturbed states of the ionosphere.

The reactivity of cinnamic acid derivatives as lignin precursors

Objectives. Cinnamic acid derivatives belong to a large class of phenolic compounds, which are widely distributed in plants and have high potential for use in the medical and industrial fields. They have various useful practical properties, e.g., antioxidant, anti-inflammatory, antiplatelet, and anti-melanogenic properties. Hydroxycinnamic acids are of particular interest as phenylpropanoids, which are the starting compounds of lignin. The aim of this work was to study the electronic structure and analyze the reactivity of the simplest representatives of phenylpropanoids formed during the biosynthesis of the coumaric (p-hydroxycinnamic), caffeic (3,4-dihydroxycinnamic), ferulic (3-methoxy-4-hydroxycinnamic), sinapic (3,5-dimethoxy-4- hydroxycinnamic), and 3,4-dimethoxycinnamic acids. These acids are the biogenetic precursors of most other phenolic compounds (coumarins, melanins, lignins, and flavonoids) and are found in almost all higher plants.Methods.Calculations with full optimization of the geometric parameters were performed using the original Hartree–Fock theory and hybrid density functional method. All calculations were performed using the Firefly program.Results.A comparative quantum chemical calculation of the geometric parameters of hydroxycinnamic acid molecules was conducted via two methods, and the values of the charges on atoms according to Mulliken were determined. It was found that with the addition of hydroxyl and methoxy substituents at the meta and para positions relative to the carboxyl fragment, the electron density shifts toward the benzene ring, and the symmetry of the molecule decreases. Additionally, in these structures, there is π,π-conjugation of the carboxyl fragment of the –СН=СНСООН molecule with the aromatic ring, which significantly affects the geometric configuration of the molecule. The maximum positive charge is concentrated on the C9 atom, while the maximum negative charge is on the oxygen atoms belonging to the methoxy substituents and the hydroxyl group, which confirms the role of oxygen atoms in the chemical transformations of acids.Conclusions.Two different methods were used to calculate the geometric, electronic, and energy parameters and electrophilicity indices of the studied hydroxycinnamic acids in the gas phase. The obtained values were consistent (within the limits of error) with the experimental data as well as the results described in earlier works’ calculations by other methods.

A Quantitative Structure-Activity Relationship Study on the Antimalarial Activities of 4-Aminoquinoline, Febrifugine and Artemisinin Compounds

Quantum chemical molecular descriptors representing different types of chemical reactivity were employed to investigate the antimalarial activities of 4-aminoquinoline, febrifugine, artemisinin and their derivatives. The quantitative structure-activity relationship results reveal that: (i) the antimalarial activities of 4-aminoquinoline compounds against the chloroquine-sensitive Plasmodium falciparum 3D7 strain are mainly affected by the electron flow and polarization interactions; (ii) The reactivity descriptors for the activities of febrifugine compounds against the chloroquine-resistant Plasmodium falciparum FCR-3 strain are the electron-acceptance chemical potential, the maximum nucleophilic and electrophilic local softness, the maximum positive charge of the hydrogen atom, etc.; (iii) The electron-donation chemical potential, the maximum negative charge, the inverse of the apolar surface area and the molar volume of artemisinin compounds are the most important descriptors for evaluating the activity against the chloroquine-resistant Plasmodium falciparum W-2 strain.

Influence of different processes of the electron emission on the ultrahigh charging of a dust particle in plasma by the energetic e-beam.

Results of numerical modeling of dynamics of ultrahigh charging of the dust particle surrounded with plasma and irradiated by an electron beam with high electron energy are given in the presented work. The e-beam was created by the pulsed open discharge in strongly overvoltage regime.The maximum negative charge accumulated on the irradiated particle is defined by the intensity of processes of charging and discharging of a target. In general, the process of charging is defined by e-beam parameters (its energy and the current density) while the discharging of a target depends on many processes, such as delivery of positive ions from the plasma onto a negatively charged target and also an emission of electrons from a target surface. In its turn, the electron emission from a surface is caused by the various processes including kinetic emission of electrons due to impact of the target by fast ions, secondary electron emission by e-beam, thermo-emission and auto-emission of electrons in case of strong heating of a particle and emergence of the strong electric field on a surface of the highly charged target. The ultrahigh charging of the dust particle irradiated by an e-beam with the energy of 25 keV was modeled. Results of numerical calculations about influence of the listed above discharging processes of a target on its maximum negative charge and potential have shown that the greatest contribution to the target discharging process belongs to the kinetic electron emission caused by fast positive ions.

Fabrication of cost effective g-C3N4+Ag activated ZnO photocatalyst in thin film form for enhanced visible light responsive dye degradation

The aim of this study is to analyze the photocatalytic dye degradation efficacy of ZnO/g-C3N4/Ag composite thin films prepared using a simple jet nebulizer spray pyrolysis technique. The XRD results confirm the presence of phases related to silver and graphitic carbon nitride in addition to the host ZnO wurzite structure. The photocatalytic studies show that the addition of Ag and g- C3N4 remarkably improves the photocatalytic efficiency of ZnO. The ZnO/g-C3N4/Ag thin film causes 96 and 99% decomposition of Methylene Blue (MB) and Malachite Green (MG) dye molecules, respectively. The mineralization of the dyes is confirmed by COD measurements. To find the optimum operating pH of the dye, the point of zero charge and the pH corresponding to the maximum surface negative charge of ZnO/g-C3N4/Ag film are found out experimentally. The possible mechanism and reasons for the enhanced photocatalytic activity of the ZnO/g-C3N4/Ag thin films are discussed with appropriate evidences and related literature.

A Quantitative Structure-Property Relationship Study of the Adsorption of Amino Acids on Kaolinite Surfaces

This article describes how the adsorption behaviors of various kinds of amino acids onto kaolinite surfaces were investigated by the quantum-chemical calculations and the quantitative structure-property relationships (QSPR). The QSPR results revealed that both adsorption energies of amino acids on tetrahedral Si-O and octahedral Al-O surfaces were mainly affected by the chemical potential and the negative of maximum negative charges of amino acids, which represent the electron flow and the hydrogen bonding between adsorbent-adsorbate interactions. The dispersion and polarization play a minor role in the amino acids adsorption on tetrahedral Si-O and octahedral Al-O surfaces, respectively.

Optimization of tetravalent manganese feroxyhyte's negative charge density: A high-performing mercury adsorbent from drinking water

This study demonstrates an optimization procedure for the development of an Hg-specified adsorbent able to comply with the regulation limit for drinking water of 1μg/L. On this purpose, the synthesis of Mn(IV)-feroxyhyte was modified to achieve high negative charge density by combining alkaline and extreme oxidizing conditions. In particular, precipitation of FeSO4 at pH9 and excess of KMnO4 follows a very fast nucleation step providing a product with very small nanocrystal size (1–2nm), high specific surface area (300m2/g) and maximum negative charge density (1.8mmol H+/g). The adsorbent was validated for Hg removal in batch experiments and column tests using natural-like water indicating an adsorption capacity as high as 2.5μg/mg at equilibrium concentration 1μg/L under reliable conditions of application. Importantly, the adsorption is an exothermic spontaneous process, resulting in the formation of inner sphere complexes by sharing both A-type and B-type oxygen atoms with the metal surface octahedral as revealed by the X-ray absorption fine structure results.

Theoretical Insights Elucidate Novel Active Phosphonate Esters—Cephalosporin Antibiotics’ Intermediate

Theoretical insights elucidate a series of active phosphonate esters application in preparation of Cephalosporin antibiotics’ intermediate. The B3LYP/6-311+G(d,p) method was employed to obtain the stable equilibrium geometries including comparing to the AE-active ester. It was found that the Ethyl-aminothiazoly Loximate (AT) molecule fragment is almost planar sheet, but it is almost perpendicular to the plane of phosphoryl ester. Moreover, the calculated Mulliken atomic charge distribution and frontier molecular orbital analysis of these esters showed that the amino N atom connected to the Thiazole ring of the AT had the maximum negative charge, which suggested that this area had high molecular activity. The value of ΔEL-H was energy gap between EHOMO and ELUMO and indicated that compound 6a had high reaction activity. The theory calculation results can explain the reaction mechanism well and predict that the novel active phosphonate ester has a hopeful application prospect in preparation of Cephalosporin antibiotics’ intermediate.

Quantum-chemical descriptors and the assessment of surface activity in coal flotation

The activity of reagents in coal flotation may be assessed on the basis of quantum-chemical descriptors. Semiempirical calculations indicate that hard electrophilic centers in the coal surface correspond to carbon atoms with maximum positive charge. The oxygen atoms are nucleophilic centers of complex terephthalates, which are characterized by maximum negative charges and therefore able to form donoracceptor complexes with electrophilic sections of the coal surface. The reaction corresponds to a charge-controlled mechanism.

Material Research on High-Quality Passivation Layers with Controlled Fixed Charge for Crystalline Silicon Solar Cells

We evaluated the three types of composition spread passivation layer, i.e., Al2O3–HfO2, HfO2–Y2O3, and Al2O3–Y2O3 systems, by combinatorial pulsed laser deposition to evaluate and control the fixed charge, while interface states were kept constant with a SiO2 interlayer. The flat-band voltage of the capacitance–voltage (C–V) curves was shifted widely from positive to negative by changing the composition. The calculated fixed charge in the Y2O3 was positive while those in the HfO2 and Al2O3 were negative. In the Al2O3–Y2O3 system, the fixed charge was significantly varied between -2.7 and 1.3×1012 cm-2 with composition spread. The maximum negative charge was found in the Al2O3 layer with a slight amount of Y2O3, while the maximum positive charge was realized with almost pure Y2O3. The fixed charge modifications were also found in the Al2O3–HfO2 and HfO2–Y2O3 systems. Additional oxidation after layer deposition also modified the fixed charge properties. The largest negative fixed charge of -3.1×1012 cm-2 was found in approximately HfO2:Y2O3=1:1 after the annealing process, while the largest positive charge of 1.3×1012 cm-2 was found for Y2O3 with Al2O3 incorporation. The passivation layers with controlled fixed charge can be promising materials for the high-quality passivation layer in crystalline silicon solar cells.

Influence of solution conditions and polymer chemistry on the adsorption behaviour of anionic dispersants onto chalcocite in aqueous media

The adsorption behaviour of two polymeric dispersants (Cyquest 3223: sodium acrylate/acrylamide co-polymer and P80: sodium allyl sulfonate/maleic acid co-polymer) onto chalcocite mineral particles has been investigated as a function of solution pH (5, 7 and 9) and different oxidative environments. The dissociation of both polymers in aqueous solutions in the pH range 2–10 was quite similar, commencing at pH 2 and finishing at ∼pH 7, where the polymers became fully ionised, reflecting maximum negative charge. Strong pH-dependent adsorption onto negatively charged chalcocite at pH 7 and 9 was observed, the behaviour consistent with polymer binding through a chemical complexation mechanism. Furthermore, the plateau adsorption density was ∼80% greater under air or O 2 gas saturation, than under N 2 gas saturation and ∼25% higher for P80 than Cyquest 3223. Unlimited polymer adsorption propensity was displayed at pH 5, with no polymer remaining in solution irrespective of initial polymer concentration. The polymer adsorption behaviour is rationalized in terms of dissolved Cu(II) metal ion mediation. Both lower pH and stronger oxidative environment (oxygen or air saturation) facilitated chalcocite oxidation, Cu(II) leaching and hydrolysis at chalcocite particle–solution interface. These subsequently fostered Cu(II)-polymer (carboxylic acid and sulfonate groups) complexation and adsorption, the extent of which was greatly attenuated under weak dissolution conditions of N 2 purging and high pH. Langmuirian polymer adsorption behaviour was displayed at pH 7 and 9, implying substantially homogeneous chalcocite surface adsorption sites.

Negative Electrospray Droplet Exposure to Gaseous Bases for the Manipulation of Protein Charge State Distributions

The exposure of electrospray droplets to vapors of reagents of various base strengths affects protein negative charge state distributions independent of initial solution conditions. Volatile bases are introduced into the counter-current nitrogen drying gas of an electrospray interface to interact with charged droplets as they undergo desolvation/disintegration, shifting charge state distributions of proteins to higher, more negative, charge states. Alterations of charge state distributions can implicate protein folding/unfolding phenomena. Species bound by relatively weak interactions can be preserved, at least to some extent, allowing for the observation of high charge states of protein-ligand complexes, such as high negative charge states of holomyoglobin. The binding of carbonic anhydrase with its Zn(2+) cofactor is apparently preserved when the holo-form of the protein is exposed to basic vapors (i.e., the Zn(2+) ion remains associated with the protein), but this prevents the appearance of charge states higher than -17. Charge state distributions of proteins containing disulfide bonds shift slightly with the leak-in of basic vapors, but when these disulfide bonds are reduced with dithiothreitol in solution, charge states higher than the number of acidic sites (Asp, Glu, and C-terminus) are observed. Since there is no observed change in the distributions of buffered proteins exposed to these reagent vapors, the charge state changes are attributed largely to a pH affect. High pK(a) and highly volatile reagents have been found to be the most effective in terms of observing the maximum negative charge state of the biomolecule of interest.

Direct Correlation of the Crystal Structure of Proteins with the Maximum Positive and Negative Charge States of Gaseous Protein Ions Produced by Electrospray Ionization

Electrospray mass spectrometric studies in native folded forms of several proteins in aqueous solution have been performed in the positive and negative ion modes. The mass spectra of the proteins show peaks corresponding to multiple charge states of the gaseous protein ions. The results have been analyzed using the known crystal structures of these proteins. Crystal structure analysis shows that among the surface exposed residues some are involved in hydrogen-bonding or salt-bridge interactions while some are free. The maximum positive charge state of the gaseous protein ions was directly related to the number of free surface exposed basic groups whereas the maximum negative charge state was related to the number of free surface exposed acidic groups of the proteins. The surface exposed basic groups, which are involved in hydrogen bonding, have lower propensity to contribute to the positive charge of the protein. Similarly, the surface exposed acidic groups involved in salt bridges have lower propensity to contribute to the negative charge of the protein. Analysis of the crystal structure to determine the maximum charge state of protein in the electrospray mass spectrum was also used to interpret the reported mass spectra of several proteins. The results show that both the positive and the negative ion mass spectra of the proteins could be interpreted by simple consideration of the crystal structure of the folded proteins. Moreover, unfolding of the protein was shown to increase the positive charge-state because of the availability of larger number of free basic groups at the surface of the unfolded protein.

Lithium and lanthanum complexes with acenaphthylene dianion. Molecular structure of [Li(Et2O)2]2μ2:η3[Li(η3:η3-C12H8)]2 complex

The lithium complex with the acenaphthylene dianion [Li(Et2O)2]2μ2:η3[Li(η3:η3-C12H8)]2 (1) was synthesized by the reduction of acenaphthylene with lithium in diethyl ether. According to the X-ray diffraction data, compound 1 has a reverse-sandwich structure with the bridging dianion μ2:η3[Li(η3:η3-C12H8)]2. Two lithium atoms in complex 1 are located between two coplanar acenaphthylene ligands of the μ2:η3[Li(η3:η3-C12H8)]22– dianion and are η3-coordinated with the five- and six-membered rings. The lanthanum complex with the acenaphthylene dianion [LaI2(THF)3]2(μ2-C12H8) (2) was synthesized by the reduction of acenaphthylene in THF with the lanthanum(iii) complex [LaI2(THF)3]2(μ2-C10H8) containing the naphthalene dianion. The 1H NMR spectrum of complex 2 in THF-d8 exhibits four signals of the acenaphthylene dianion, whose strong upfield shifts compared to those of free acenaphthylene indicate the dianionic character of the ligand. The highest upfield chemical shift belongs to the proton bound to the C atom on which, according to calculation, the maximum negative charge is concentrated.

Effect of surface material on electrostatic charging of houseflies (Musca domestica L).

Houseflies (Musca domestica L) accumulated electrostatic charges when walking over clean, uncharged dielectric surfaces. The charges elicited on a walking housefly by a range of materials were quantified, allowing a triboelectric series to be determined relative to M domestica. This ranged from surfaces that charged individuals positively, e.g. Correx (corrugated polypropylene) [.1 (+/- 4.2)pC], to those that applied a negative charge, e.g. clear cast acrylic [-14.9 (+/- 2.9)pC]. Maximum positive and negative charges accumulated by individual M domestica were +73 and -27 pC. Replicate measurements on the same fly and surface showed little variation. Variation between individuals was not related to sex and was not consistent between surfaces. Different materials charged M domestica significantly differently and individual flies had significantly different charging properties. Variation in temperature between 21.3 degrees C and 24.7 degrees C and humidity between 24% and 41% RH significantly affected charge accumulated by M domestica on some surfaces, although further experimentation is needed to confirm this. The implications of this work are discussed in relation to insect trap design and pollination biology.

Electric charge on small silicone oil droplets dispersed in ionic surfactant solutions

The effect of the type and the concentration of ionic surfactants on the electric charge on small silicone oil droplets is studied by using an electrical suspension method. The adsorption process of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), is characterized by gradual neutralization of the negative charge on the oil-in-water (O/W) emulsion droplets at low surfactant concentrations. As the surfactant concentration increases, the adsorption process leads to the charge reversal. The point of charge reversal (pcr) occurs approximately at 2.5×10 −6 M CTAB. Further increasing the surfactant concentration causes an increase in the positive charge and eventually results in the maximum positive charge on the oil droplets near the critical micelle concentration (CMC) of CTAB. The limited charge reflects the saturation of the adsorption of surfactant molecules on the oil–water interface. In an anionic surfactant solution of sodium dodecyl sulphate (SDS), however, the silicone oil droplets are all negatively charged and the negative charge increases with increasing the surfactant concentration. The saturation state is also observed for the anionic surfactant adsorption. The maximum negative charge is achieved when SDS concentration approaches its CMC. In addition, two types of ionic adsorption onto the oil–water interface may occur for NaCl electrolyte solutions containing either CTAB or SDS: the surfactant adsorption and the electrolyte adsorption, although the former is much stronger than the latter. At constant surfactant concentration, their cooperation strengthens the charge at lower NaCl concentrations and leads to the strongest charge at some concentration. However, their competition at higher NaCl concentrations reduces the charge on the oil droplets.