Absence Of Electrolyte Research Articles

Analysis of a film-forming amine response in impedance spectra

In this study, a detailed analysis of the dielectric response of a film-forming amine (1,3 N-oleyl propanediamine (OLDA)) in impedance spectra is presented, addressing both “bulk” OLDA and adsorbed OLDA layer on a carbon steel surface. The dielectric response of the “bulk” OLDA in the absence of electrolyte over an extensive temperature range (-150 °C to 50 °C) was explored by broadband dielectric spectroscopy (BDS). Subsequently, the response of the OLDA adsorbed layer on the steel surface was analysed by electrochemical impedance spectroscopy (EIS), for various immersion times (2 min to100 min) and temperatures (25 °C to 75 °C) in an aqueous NaCl solution.Impedance spectra (BDS and EIS), interpreted through the complex conductivity formalism, showed a resistive behaviour in the mid-frequency range and a capacitive behaviour at higher frequencies. The high frequency capacitive response in EIS spectra was shown to contain contributions from the OLDA layer and from the electrochemical double layer, as well. The temperature dependency of the OLDA conductivity was found to be similar to the temperature dependency of the electrolyte resistance, suggesting that the electrolyte (water and ions) crossed the OLDA layer to reach the steel surface. The presence of gauche defects in the OLDA alkyl chain, revealed by polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) analyses, may be a contributing factor to the disorder in the adsorbed layer, facilitating electrolyte infiltration.

Heteroaggregation kinetics of oppositely charged nanoplastics in aquatic environments: Effects of particle ratio, solution chemistry, and interaction sequence

Interactions between positively charged amino-modified (APS) and negatively charged bare (BPS) polystyrene nanoplastics may cause heteroaggregation in aquatic environments. This study investigated the effects of particle concentration ratio, solution chemistry [electrolytes, pH, and natural organic matter (NOM)], and interaction sequence on their heteroaggregation kinetics. In the absence of electrolytes and NOM, the APS/BPS ratio for attaining maximum heteroaggregation rate (khetero) increased from APS/BPS= 3/7 to APS/BPS= 1/1 as pH increased from 4 to 10, indicating that electrostatic interactions dominated heteroaggregation. In the absence of NOM, khetero ranked APS/BPS= 2/3 > APS/BPS= 1/1 > APS/BPS= 3/2. Colloidal stability decreased linearly as pH increased from 4 to 8 at APS/BPS= 1/1, while diffusion-limited heteroaggregation persisted at pH 10. In NaCl solution, humic acid (HA) retarded heteroaggregation more effectively than sodium alginate (SA) via steric hindrance and weakening electrostatic interactions, following the modified Derjaguin-Landau-Verwey-Overbeek (MDLVO) theory. Compared with simultaneous interactions among APS, BPS, NaCl, and NOM, the NOM retardation effects on heteroaggregation weakened if delaying its interaction with others. In CaCl2 solution, the effects of NOM on heteroaggregation depended on counterbalance among charge screening, steric hindrance, and calcium bridging. These findings highlight the important role of heteroaggregation between oppositely charged nanoplastics on their fate and transport in aquatic environments.

Microfabrication and electrochemical behaviors of single microcrystal of copper-doped sodium chloride solid solution

Understanding the single-particle level of electrochemical processes taking place at the electrode/electrolyte interface is crucial for the rational development of high-performance and sustainable electrochemical microdevices. Based on scanning electrochemical cell microscope (SECCM) technology, copper-doped sodium chloride solid solution microcrystal was prepared in-situ and assembled into microdevices. In the process of synthesizing copper-doped sodium chloride solid solution, the redox behavior of Cu(II)-Cl system in the microelectrochemical cell was studied. The CV curve showed that the microdroplet contact between the microtubule and substrate was supersaturated, confirming the thin layer electrochemical response characteristics. By constructing the microcrystal between 2.5 µm spaced gold electrode pairs, the "solid" redox behavior of a single copper-doped sodium chloride microcrystal in the absence of electrolyte was studied. It is found that there is a well-resolved transformation between Cu(0), Cu(I) and Cu(II) in the microcrystal. It should be noted that the adsorbed water provides H+as a pair of ions, which plays an important role in the whole system. With the continuous progress of potential scanning, the solid-state CV curves of microcrystals gradually show semiconductor characteristics. This work presented herein is expected to promote the production of practical materials by SECCM and the practical application of on-site construction of electrochemical microsystem into all solid-state microdevices.

Modeling and Sizing of a Y-Shaped Laminar Flow Micro-Fluidic Fuel Cell

The high demand for portable and desktop electronic devices requires mobile energy sources. Electronic devices, in general, are small when they are portable and require autonomy, sustainability, efficiency, and large enough periods of operability. In that sense, microtechnology, a type of technology related to the manufacture of prototypes or three-dimensional high-precision products in various materials ranging in size from tenths of microns to a few millimeters, has reached a boom in microfabrication of devices that are not exclusively electronic. Applications in several fields show that micro-energy sources are a focal point for commercializing prototypes in the mobility sector.The energy demand to supply micro-devices has been increasing in recent years. Considering the power output of the laminar flow microfluidic fuel cell (LFFC), it is a suitable solution to provide the required electrical energy in small devices. The absence of electrolytes and no requirement of platinum as catalytic material are two of the most important advantages of this type of fuel cell. The current study provides detailed information about the design and characteristics of an LFFC. A complete analysis of the different channel shapes is considered in this study, with the Y-shaped channel being selected as the best option. The impact of the inclination degree for the inlet channels has been considered to evaluate the average velocity the flow acquires in the channel. In addition, the voltage-current behavior considering the materials, fuel/oxidant, and design characteristics has been obtained through modeling approaches. Figure 1. Velocity profile and Reynolds number in the mid-plane of the Y-channel design Figure 1

Operando Ambient Pressure X Ray Photoelectron Spectroscopy for Li-Ion Battery Electrode/Electrolyte Interface Probing

Electrochemical reactions occur at the electrode/electrolyte interface. In lithium-ion batteries, the reversible Li ion insertion/desertion from the interfaces of electrodes gives the capacity of the battery. The surface phase transition and component chemical states change during the lithiation/delithiation in turn hugely effect the further battery capacity and reversibility. In the past decades, many ex-situ characterizations gave some insights of electrode surface behavior after cycling. However, the surface chemistry of electrode relies decisively on the real battery operation condition, e.g. the passive layer formed on the electrode surface changes dramatically with the absence of electrolyte. Therefore it is emerging and necessary to develop operando study for electrode/electrolyte interface probing during battery cycling.X-ray photoelectron spectroscopy (XPS) as a surface sensitive technique detects the photoelectrons ejected from core level with certain pass energy. The binding energy of the electrons give the information of chemical composition and chemical states of the materials. Ambient pressure XPS, developed rapidly in recent years after since it gives possibility of the participation of gas and/ liquid phase, enabling the observation of structure dynamics during chemical reactions, thereby unprecedentedly extended the application of the technique. A method called dip-and-pull is used for operando liquid/solid interface probing. With a typical three-electrode system, the electrode is pulled up from the electrolyte with still contact to liquid to maintain the circuit. A thin film of electrolyte formed with a shape of meniscus at the interface of electrode, electrolyte and atmosphere is probed through. The probing of the electrochemical active surface through the liquid can be achieved with an optimized liquid layer and surface condition.In this study Lithium cobalt oxide (LCO), as the most widely used positive electrode for Li-ion battery with rock salt layered structure optimized for reversible Li intercalation/deintercalation, is used for interface dynamics investigation. As Li is deintercalated from LCO structure, the charge transfer from Li+ to Co-O environment causes a phase change. It was commonly assumed that the charge due to the deintercalation of Li from structure is fully transferred to Co3+, i.e. the loss of one electron contributes to one Co4+ from Co3+ oxidation. However, it is recently reported that the real condition maybe more complicated. The charge transfer from Li+ to Oa- (a<2) might take place especially during high voltage due to the hybrid fermi level of O and Co which might increase the mobility of Oa- and further results in cobalt reduction and oxygen evolution reaction. But the mechanism of structure evolution under corresponding potentials are very unclear. In this study, with the operando probing with APXPS, it is discovered that a native phase of Co2+ may play an unignorable role in the charge transfer, giving some new understandings of phase transition during lithiation/delithiation (see figure 1). With the development of APXPS for battery probing, combining with software data treatment, a clearer picture of phase evolution is possible to be given by time-resolved probing with APXPS. Potentially hidden intermediate states during electrochemical reactions which cannot be given from ex-situ probing are resolved. Figure 1

Modeling and Sizing of a Y-Shaped Laminar Flow Micro-Fluidic Fuel Cell

The high demand for portable and desktop electronic devices requires mobile energy sources. The energy demand to supply micro-devices has been increasing in recent years. Considering the power output of the membraneless microfluidic fuel cell (MMFC), it is a suitable solution to provide the required electrical energy in small devices. The absence of electrolytes and no requirement of platinum as catalytic material are two of the most important advantages of this type of fuel cell. The current study provides detailed information about the design and characteristics of an MMFC. A complete analysis of the different channel shapes is considered in this study, with the Y-shaped channel being selected as the best option. The impact of the inclination degree for the inlet channels has been considered to evaluate the average velocity the flow acquires in the channel flow. In addition, the voltage-current behavior considering the materials, fuel/oxidant, and design characteristics has been obtained through modeling approaches.

Mechanical properties and role of 2D alkynyl carbon monolayers in the progress of lithium-air batteries

Lithium-air batteries (LABs) have been proposed as power sources for developing electric vehicles due to their high theoretical capacity. The cathode of these batteries is typically constructed based on porous carbon allotropes. Two-dimensional (2D) alkynyl carbon materials (D-graphyne, P-graphyne, and QC-graphyne), show remark structure features and can provide a unique opportunity for designing the air cathode of the LABs. However, the physical characteristics of these 2D carbon monolayers have not been clear completely studied as air cathodes. Hence, in the current study, the effect of length, strain rate, temperature, and (CH3)2OS/LiPF6 non-aqueous electrolyte with 1 Molar concentration on mechanical features were investigated for 2D alkynyl sheets using molecular dynamics simulation. The results show that the mechanical stability is in the order of D- > P- > QC-graphyne, and the percentage difference of mechanical properties in the presence and absence of electrolyte is <13 % at 300 K. These results are proper for an air cathode because they reveal that the electrolyte cannot lead to significant mechanical weakness. The lithium diffusivity increases in the presence of 2D alkynyl carbon allotropes due to interfacial interactions. Moreover, 2D alkynyl monolayers provide the features of 2D graphene and γ-graphyne for lithium diffusivity that is essential due to high mechanical stability and ultrahigh capacity, respectively. The provided insight by this study highlights the 2D alkynyl monolayers which are more probable to be experimentally synthesized than other 2D graphyne families and show more desired physical characteristics for designing the air cathodes and decreasing charging time.

An exploration on CO faradaic efficiency with catalyst surface wettability ranging from hydrophilic to superhydrophobic

Hydrophobic electrode can facilitate CO2 mass transfer for carbon dioxide electroreduction reaction (CO2ER) in the microchannel reactor. However, ‘trade-off’ exists because the reaction cannot proceed in the absence of electrolyte. Therefore, effective control of wettability on the surface of the catalyst is significant to achieve efficient CO2ER performance. In this paper, a nanocone-shaped Zn@Ag has been fabricated through a simple two-step preparation process involving the hydrothermal treatment and the galvanic replacement. Further modification of the myristic acid (MA)/stearic acid (SA) layer on the nanocone by the immersion method can extend the interfacial wettability to the superhydrophobic scale. The experimental parameters including the time of three synthesis procedures were adjusted to regulate the dimensions and surface free energy of the nanocone. Consequently, the nanoncone catalyst itself possessed a maximum intrinsic water contact angle (CA) of ∼114°, while the SA modified catalyst demonstrated an outstanding water repellency with CA of ∼152°. The relationship between the CO Faradaic efficiency (FECO) and the surface wettability ranging from hydrophilic to superhydrophobic was ultimately explored. The optimal Zn@Ag@MA catalyst with appropriate hydrophobicity can achieve a FECO of 91%, which is nearly 20% higher than the hydrophilic/superhydrophobic counterpart. In situ attenuated total reflectance infrared (ATR-IR) tests verified that the hydrophobic catalyst can enhance CO2 concentration near the surface and promote the selectivity to CO.

Effects of Electrolytes on the Dediazoniation of Aryldiazonium Ions in Acidic MeOH/H2O Mixtures

Aryldiazonium, ArN2+, ions decompose spontaneously through the formation of highly reactive aryl cations that undergo preferential solvation by water, showing a low selectivity towards the nucleophiles present in their solvation shell. In this work, we investigate the effects of electrolytes (NaCl, LiCl, and LiClO4) on the dediazoniation of 2-, 3-, and 4-methylbenzenediazonium ions in acidic MeOH/H2O mixtures. In the absence of electrolytes, the rates of dediazoniation, kobs, increase modestly upon increasing the MeOH content of the reaction mixture. At any solvent composition, the rate of ArN2+ loss is the same as that for product formation. The main dediazoniation products are cresols (ArOH) and methyl phenyl ethers (ArOMe). Only small amounts (less than 5%) of the reduction product toluene (ArH), which are detected at high percentages of MeOH. Quantitative yields of are obtained at any solvent composition. The addition of LiCl or NaCl ([MCl] = 0–1.5 M) to the reaction mixtures has a negligible effect on kobs but leads to the formation, in low yields (&lt;10%), of the ArCl derivative. The addition of LiClO4 (0–1.5 M) to 20% MeOH/H2O mixtures has a negligible effect on both kobs and on the product distribution. However, at 99.5% MeOH, the addition of the same amounts of LiClO4 leads to a modest decrease in kobs but to a significant decrease in the yields of ArOMe. Results are interpreted in terms of the preferential solvation of perchlorate ions by the aryl cations, removing MeOH molecules from the solvation shell.

Controlled Synthesis of Polymethyl Methacrylate Latex Particles Armored by Fe3O4 via Pickering Emulsion Polymerization and Its Emulsifying Properties.

The fabrication of polymethyl methacrylate (PMMA) latexes armored with modified Fe3O4 (IO) nanoparticles by Pickering emulsion polymerization was described. Dynamic light scattering analyzed the IO/PMMA latex particle size. Thermogravimetric analysis evaluated the incorporation efficiency (IE) of IO nanoparticles and the surface coverage (Cov) of latex particles. Scanning electron microscopy confirmed the IO nanoparticles loaded on the latex surface. Both the original and dialyzed IO nanoparticles were used as stabilizers to discuss the influence of electrolytes in IO solution on the process of emulsion polymerization. In order to effectively control the IE, Cov, hydrophobic properties, and magnetization of latex particles, the kinds of monomers, pH, and solid content of dialyzed IO on the polymerization process were investigated. In addition, the conversion of monomers, the size, and the number of latex particles were learned deeply so as to reveal the key mechanism of the PMMA polymerization process in the absence of electrolytes. Moreover, IO/PMMA latex particles showed good magnetic properties and emulsifying ability. In view of these results, a simple and efficient method for preparing magnetic hybrid materials by Pickering emulsion polymerization was proposed.

On charge distribution and storage in porous conductive carbon structure

The charge storage and distribution in a porous conductive carbon material, in the presence and absence of electrolyte, are studied using the Poisson-Nernst-Planck equations for the first time in the literature. By solving the Laplace equation, it is found that the charge distribution inside the pores is negligible in the absence of the electrolyte. In the presence of cations and anions of the electrolyte inside the pores, the charge distribution on the pore surfaces and ionic concentration gradients in the electrolyte are numerically evaluated by solving the Poisson-Nernst-Planck equations. The modelling results predict the classic electric double layer structure for meso‑ and larger pores. For smaller nano-level pores, however, the equations predict a structural shift from a classic electric double layer towards a near-uniform ion storage inside the pores, that is, a concentration of counter ions within pores. The accuracy level of the results is then analysed considering modified Poisson-Nernst-Planck equations, relative permittivity variations of the electrolyte, and the validity of the continuum assumption. The modelling predictions are experimentally tested by measuring the charge storage under different electrolyte concentrations in two activated carbon samples with different pore structure characteristics.

Ammonia Synthesis at Ambient Conditions via Electrochemical Atomic Hydrogen Permeation.

Direct electrochemical nitrogen reduction holds the promise of enabling the production of carbon emission-free ammonia, which is an important intermediate in the fertilizer industry and a potential green energy carrier. Here we show a strategy for ambient condition ammonia synthesis using a hydrogen permeable nickel membrane/electrode that spatially separates the electrolyte and hydrogen reduction side from the dinitrogen activation and hydrogenation sites. Gaseous ammonia is produced catalytically in the absence of electrolyte via hydrogenation of adsorbed nitrogen by electrochemically permeating atomic hydrogen from water reduction. Dinitrogen activation at the polycrystalline nickel surface is confirmed with 15N2 isotope labeling experiments, and it is attributed to a Mars–van Krevelen mechanism enabled by the formation of N-vacancies upon hydrogenation of surface nitrides. We further show that gaseous hydrogen does not hydrogenate the adsorbed nitrogen, strengthening the benefit of having an atomic hydrogen permeable electrode. The proposed approach opens new directions toward green ammonia.

Effect of Electrolytes on Solution and Interfacial Behaviors of Double Chain Cationic-Nonionic Surfactant Mixtures for Hydrophobic Surface Wetting and Oil/Water Emulsion Stability Applications.

The solution behaviors of the binary mixture of double chain cationic surfactant didodecyldimethylammonium bromide (DDAB) with nonionic surfactants of varied head groups, EO-9 and EO-40, in the presence and absence of electrolytes were studied and found nonideal behavior. The different physicochemical properties such as Gibb's surface excess (Γ), minimum area per molecule (Amin), and interaction parameters at bulk (βM) and interface (βσ) were calculated. In the presence of nonionic surfactants, lowering of CMC, CVC, and surface tension at these two concentrations of DDAB were observed. The βM and βσ values indicate strong interaction between DDAB and EO-40 mixed system. Further, addition of electrolytes to the mixed systems show increased interaction and change of physicochemical properties because of the combination of electrical and salting out effects.

An unexpectedly high incidence of refeeding syndrome in patients with total parenteral nutrition in a reference university hospital

Refeeding syndrome occurs with the reintroduction of food after an individual has undergone a substantial period of malnutrition. The development of this condition is not uncommon but is neglected in most cases. To identify the incidence of refeeding syndrome in hospitalized patients undergoing total parenteral nutrition and factors that may be associated with this condition. Observational retrospective and prospective cohort study. Data collection took place at the Hospital de Clínicas de Porto Alegre, from 2015 to 2018. Data was collected consecutively from patient electronic medical records. All hospitalized individuals aged 18 years or more and having a prescription for total parenteral nutrition were included in the study. Exclusion criteria included patients with diabetic ketoacidosis; receiving renal replacement therapy or chronic kidney disease with a glomerular filtration rate <30mL/min; severe metabolic acidosis or any disease that could affect serum phosphorus levels. WinPepi software, version 11.65, was used to calculate sample size. Data analysis was performed using SPSS version 20.0. A 5% significance level was considered for the established comparisons. The project was approved by the Research Ethics Committee of Hospital de Clínicas de Porto Alegre (number 17-0313). Data from 97 patients was collected. The incidence of refeeding syndrome in our sample was 43.3% (n=42). Factors positively associated with the syndrome were use of standard parenteral nutrition (p<0.01), advancing age (mean 62.8yr versus 55.1yr; p=0.013), and amount of total energy administered, which were 25.6kcal/kg/day versus 23.6kcal/kg/day for patients with and without refeeding syndrome, respectively (p<0.01). The incidence of refeeding syndrome in individuals using total parenteral nutrition was high. The supply of a greater quantity of total energy in the first week of nutritional therapy, the absence of electrolytes in the parenteral nutrition solution and advancing age were all factors associated with the emergence of refeeding syndrome.

Roles of solution chemistry and reagent–reagent interaction on carboxymethylcellulose adsorption onto graphite and implications on its floatability

The influence of electrolytes (NaCl and CaCl2) and a copper sulphide collector (isopropyl ethyl thionocarbamate, IPETC) on adsorption of carboxymethylcellulose (CMC) onto a graphite surface were studied using adsorption tests, zeta potential measurements and floatability tests. Adsorption tests revealed negligible CMC adsorption in the absence of electrolytes and presence/absence of IPETC at lower CMC concentration of 0–100 mg/L, whereas CMC mild adsorption occurred at higher CMC concentration of 150–200 mg/L at pH 5.7 and 10. An increase in CMC adsorption was observed in the presence of electrolytes and their mixtures with IPETC. The CMC adsorption increased more in the presence of CaCl2 than NaCl, suggesting an effect of the cation valence. The addition of IPETC to NaCl solutions adversely affected the CMC adsorption and its effect was independent of the pH. Conversely, the addition of IPETC to CaCl2 solutions enhanced the CMC adsorption at pH 5.7, whereas it diminished at pH 10. The presence of electrolyte may induce the formation of complexes between CMC macromolecules with IPETC depending on the electrolyte type. Furthermore, CMC adsorption in presence of NaCl follows Langmuir isotherm whereas in presence of CaCl2 follows Freundlich isotherm. Moreover, the floatability tests indicated that the graphite floatability decreased more at pH 10 than at pH 5.7 in the presence of electrolytes. Only the floatability at pH 5.7 was comparable for both electrolytes. Finally, addition of IPETC to electrolyte solutions had a marked effect on graphite floatability. These findings have implications in copper sulphide flotation systems containing graphite as gangue in which IPETC is used as a collector and CMC as a depressant for graphite.

Slow Growth Approach for Lithium Ion Deposition on Lithium Metal Anode Surfaces

Lithium metal anodes are indispensable for next-generation batteries including Lithium-Sulfur and Lithium-air batteries which show high promise for electric vehicles and other energy storage applications. Challenges such as extreme reactivity and lithium dendrite formation have kept lithium metal anodes away from practical applications. Lithium dendrite formation on anode surfaces during the charging process originates from the inhomogeneous deposition of metallic lithium during the electrochemical reduction of lithium cations. However, the underlying mechanisms of Li ion deposition from the electrolyte solution onto the anode surface are still poorly understood due to its inherent complexity. In this work, Density Functional Theory (DFT) simulations and thermodynamic integration calculations are conducted to study the electron and ion transfer between lithium metal slab and the electrolyte in absence of an external field. The slow growth approach allow the energy barriers on the diffusion and deposition pathway to be studied. This method illuminate the underlying mechanisms on lithium-ion deposition and provide a better understanding of the early stages of dendrite nucleation. We explore the effect of the solvent chemistry and structure, distance of the solvated complex from the surface, anion-cation separation, and concentration of Li-salts on the deposition of lithium ions from the electrolyte phase onto the surface. It is found that the structure and properties of the solvation shell around the lithium cation has a great influence on the ability of the cation to diffuse as well as on its surrounding electron environment.

Multifunctional electrolyte additive for improved interfacial stability in Ni-rich layered oxide full-cells

Improving the interfacial stability between the electrode and the electrolyte at high voltage is a key to successfully obtain high energy-density Li-ion batteries. Therefore, this study is dedicated to a novel multifunctional electrolyte additive, methoxytriethyleneoxypropyltrimethoxysilane (MTE-TMS), able to stabilize the interface of both Ni-rich layered LiNi0.85Co0.1Mn0.05O2 (NCM851005) cathode and graphite anode in a full-cell. Electrochemical tests reveal that the addition of 1 wt% MTE-TMS significantly improves the long-term cycling stability of the graphite‖NCM851005 full-cell, with an achieved maximum capacity of 198 mAh g−1 and its excellent capacity retention of 84% after 100 cycles at C/5 using upper voltage cut-off of 4.3 V vs Li+/Li. In contrast, the standard electrolyte in absence of MTE-TMS leads to a rapid performance fade. The significantly improved electrochemical performance is attributed to the formation of a stable surface protective film at both the cathode and the anode surfaces upon long-term cycling in elevated voltage window, and thus suppressing the electrolyte decomposition at and structural degradation of both cathode and anode, resulting as well in reduced transition metal transfer between the two electrodes.

Chemical Modification of Cotton Cellulose by Carbamation with Urea and Its Dyeability with Reactive Dyes without the Use of Electrolyte

ABSTRACT Dyeing of cotton cellulose is done mostly with reactive dyes which form a strong covalent bond with the substrate. Reactive dyeing process requires a high amount of salt and alkali. Studies have been made to improve the exhaustion and reduce the use of a high amount of salt and alkali by cationization of the substrate. This study focuses on the carbamation of mercerized cotton cellulose for the purpose of preparing an alternative way of dyeing cotton fabric with Reactive dye in the absence of electrolyte. The effect of carbamation was shown by FTIR spectra qualitatively, where the optimal results were with urea concentration of 400 g/l, temperature of 135°C and time of 5 minutes. The carbamated cotton showed lower decomposition temperature than that of native cotton. The color strength, exhaustion, fixation and total dye utilization studies show good results compared to dyeing conventional cotton fabric.

Size-dependent aggregation of graphene oxide

Graphene oxides (GO) of highly polydisperse size distribution were prepared by the Brodie method and their dispersion stability was characterized. Exfoliation and fractionation led to well-defined particle populations in the Nano, classical Colloidal (submicron) and Micrometer size ranges, as revealed by atomic force microscopy and light scattering measurements. Time-resolved dynamic light scattering experiments revealed that aggregation processes are fully impeded in the intermediate pH regime of 3–13 in the absence of electrolytes. While the resistance against salt-induced aggregation increases with the pH due to the progressive ionization of the surface functional groups of GO sheets, their dispersions are inherently unstable at supramillimolar concentrations of strong acids and submolar concentrations of bases, in line with the DLVO theory. However, the aggregation behavior quantified by the critical coagulation concentrations (CCCs) shows surprisingly substantial platelet size dependence. The CCC of Nano Brodie-GO reaches 360 mm at pH = 12, which is one of the highest values ever reported for GO aqueous dispersions. These results provide useful quantitative information to design processable GO dispersions of pH- and size-tunable stability for future applications.

Влияние ионного состава криопротекторной среды и криоконсервирования на чувствительность эритроцитов человека к механическому стрессу

In this research, we have studied the impact of electrolytes and Ca2+ ions on the development of hemolytic damages in human erythrocytes in cryoprotectant solutions under mechanical stress, as well as the ei¬€ect of freeze-thawing of cells in the presence of glycerol and polyethylene glycol (PEG) on their mechanical stability. The decrease in mechanical stability of cells was found when the salt concentration in extracellular medium increased. At the same time, the absence of electrolytes in cryoprotectant solutions reduced their stability under mechanical stress as well. The Ca2+ introduction into the media increased the cell hemolysis only in the presence of PEG, but not glycerol, apparently due to dii¬€ erent ei¬€ects of these substances on the activity of Ca2+-regulating systems. The introduction of salt of ethylenediaminetetraacetic acid (EDTA) into the media composition reduced the erythrocyte membrane mechanical stability in the presence of the both cryoprotectants, which might be due to the chelator ei¬€ect on membrane-bound Ca2+. Cryopreservation of erythrocytes increased their sensitivity to mechanical stress, and even the cryoprotectant removal could not restore the cell properties up to the control parameters. Probl Cryobiol Cryomed 2019; 29(4): 317-331