Increased Surface Activity Research Articles

Flooding triggers increased surface activity in a bottom-dwelling turtle.

Flooding triggers increased surface activity in a bottom-dwelling turtle.

Effect of pH on the interfacial and foaming properties of Maillard reaction-modified proteins

The interfacial and foaming properties of two conjugates obtained by Maillard reaction was determinate, at heating times of 36 and 60 h. The effect of covalent interaction between β-lactoglobulin (β-Lg) and two dextran molecular weights (10 and 20 kDa) were evaluated at pH 7 and pH 5, establishing protein controls, mixed systems, and mixing controls for each system. At pH 7, the first conjugate showed an increase in surface activity, while the other showed an opposite effect on the glycosylation process. At pH 5, both conjugates showed a low surface activity, evidenced in the diffusion constants. Less foaming stability was observed at pH 5, compared to pH 7, related to the formation of protein aggregates due to the proximity to their pI. Both conjugates showed greater stability, at both pH 7 and pH 5, with respect to their control systems, due to greater steric-type interaction forces between adjacent bubbles when the interface could be stabilized by glycosylates than when there is only protein. These results indicate that glycosylated b-Lg could find use as an additive and foaming agent, particularly in acidic foods.

Selective proteolysis of β-conglycinin as a tool to increase air-water interface and foam stabilising properties of soy proteins

Proteolysis of food proteins changes their conformation and often generates bioactive peptides, leading to improved nutritional value and techno-functional properties. Protein isolates that originated from plants are generally a mixture of several proteins. Enzymatic hydrolysis of such mixtures has a drawback, as it is often unclear which proteins in the mixture are hydrolysed, leading to poorly reproducible outcomes. In the present study, we applied a controlled methodology, called selective proteolysis, and investigated its effects on the air-water interface and foam stabilising properties of soy protein isolate (SPI). We selectively hydrolysed 7S β-conglycinin of SPI, while 11S glycinin remained relatively intact. Hydrolysates were obtained at two different degrees of hydrolysis (DH). Selective hydrolysis resulted in increased surface activity, and a higher foamability, which nearly doubled. The size of the peptides seemed to significantly affect the mechanical properties of the layer at the air-water interface, which was studied by removing peptides smaller than 14 kDa via dialysis. Peptides smaller than 14 kDa were found to hinder the interfacial network formation, while peptides larger than 14 kDa increased the interfacial stiffness. This was also reflected in the foam stability, as the hydrolysate with a low DH resulted in significantly higher foam stability than the hydrolysates with higher DH. We demonstrated that the selective proteolysis of β-conglycinin can increase the soy protein interface and foam stabilising properties, which could lead to new healthy and more sustainable food products.

Study on modification of nano silica by [3- (2-Aminoethyl) aminopropyl] trimethoxy silane (KH-792) to reinforce polymer film based on epoxy resin Epon 1001X75

The surface of nano silica (NS) was modified by [3- (2-Aminoethyl) aminopropyl] trimethoxy silane (KH-792) to increase surface activity. Evaluate the efficiency of grafting [3- (2-Aminoethyl) aminopropyl] trimethoxy silane (KH-792) into NS was characterized by Fourier Transform Infrared Spectrometry (FTIR) and Thermo Gravimetric Analysis (TGA). NS and modified nano silica (m-NS) were dispersed into epoxy resin Epon 1001X75 by mechanical stirring and ultrasonic vibration. Epoxy resin Epon 1001X75 was cured with Epikure 3125 (Epi3125). The structural morphology and dynamic mechanical properties of materials were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Dynamic Mechanical Analysis (DMA). The results showed that NS was modified with the content of 20 wt% KH-792 for the highest denaturation efficiency. With adding the content of 1 wt% NS (NS-1), the mechanical properties of epoxy polymer film Epon 1001X75/Epi3125/NS-1 increased the impact strength from 20kG.cm to 52.5 kG.cm (increased by 162.5%). Adding the content of 2 wt% m-NS (m-NS-2) improved the impact strength of epoxy polymer film Epon 1001X75/Epi3125/m-NS-2 from 20 kG.cm to 55 kG.cm (increased by 175%). The glass transition temperature (Tg) of epoxy polymer composites Epon 1001X75/Epi3125, Epon 1001X75/Epi3125/NS-1, and Epon 1001X75/Epi3125/m-NS-2 gradually increased by 48 °C, 75 °C, and 79 °C. The obtained results showed that m-NS with KH-792 increased the mechanical properties of epoxy polymer film Epon 1001X75/Epi3125.

A thermodynamic investigation of the effect of cationic structure on the self-aggregation behavior of Surface-Active ionic liquids in the presence of an amino acid

A series of imidazolium-based ionic liquids (ILs) with varying side alkyl chain length at N3 position which includes [C12mim][Br], [C12eim][Br], and [C12bim][Br] have been synthesized and characterized by 1H NMR. Then, their aggregation behavior in the presence of different concentrations of the amino acid L-Tryptophan (L-Trp) at different temperatures has been examined using conductometric, tensiometric, and UV–vis (absorption spectra) techniques. The critical micelle concentration (CMC) of ILs has been investigated in the absence and presence of amino acid to acquire a better understanding of the colloidal behavior of ILs in presence of amino acid as an external additive. The addition of amino acid is observed to reduce the CMC values of the ILs examined in an aqueous media. Likewise, applying a charged pseudo-phase model of micellization, the thermodynamic parameters of micellization, such as a change in standard free energy (ΔGmo), change in standard enthalpy (ΔHmo), and change in standard entropy (ΔSmo), have been scrutinized from the dependence of CMC on temperature. The surface tension approach was also used to evaluate interfacial characteristics. It was discovered that increasing the length of the side chain increases surface activity. All of the estimated parameters were utilized to determine the electrostatic and hydrophobic contributions of IL to the formation of micellar aggregates.

Study on the effect of imidazolium ionic liquid as a modulator of corrosion inhibition of anionic surfactant sodium dodecyl sulfate (SDS) on mild steel in sodium chloride solution

Present paper reports investigation done on two organic compounds to test them as corrosion inhibitors for mild steel exposed to neutral NaCl solution. Organic compounds capable of corrosion inhibition must form a protective film over the metal surface. This is usually possible since many of these organic compounds possess strong interaction properties with metal and get adsorbed over its surface. These organic compounds contain electronegative functional groups and atoms like S, N, P, and O, which form center for establishment of adsorption process. Accordingly, SDS and DMImCl were chosen as organic compounds to test as corrosion inhibitors. Electrochemical polarization tests, performed in this study, reveal decrease in corrosion rate of mild steel in NaCl solution by 14.3 to 6.08 mpy (mils per year) corresponding to increased inhibition efficiency of 57.3% on addition of up to 200 ppm SDS. On mixing 200 ppm of DMImCl in NaCl + SDS solution, the inhibition efficiency enhances to 85.1%. Similar outcome is also noticed from Electrochemical impedance and weight loss test results. Analysis of results obtained through FTIR, SEM/EDAX indicate adsorption of SDS/DMImCl mixture on the mild steel surface.Tensiometry tests, on ionic solution, reveal decrease in surface tension on addition of inhibitors with consequently increased surface activity and hydrophobic interaction between chains of the two inhibitors. Calculation done on the adsorption process indicates it to be ‘Langmuir adsorption isotherm’. This inference suggests that binding sites on steel surface are identical and homogeneously distributed. This layer is covered with a monolayer of adsorbed molecules i.e. DMImCl and SDS which is responsible for corrosion inhibition.

Effect of molasses on protein content of fresh water fish, Puntius chrysopterus

It was examined whether molasses was toxic to the freshwater fish, Puntius chrysopterus. There was a 5 percent LC50 value for Molasses. Rapid, jerky swimming with seemingly random motions; toxic convulsions; postural instability; an increase in surface activity and opercular movements; a loss of equilibrium; these are all symptoms of the Molasses poisoning. A layer of mucus formed over the gills, and the lamellae of the gills changed from red to brown. The fish were swimming in isolation from one another until they all perished. Protein was shown to be diminished throughout all fish tissues following exposure to a sub-lethal quantity of molasses.

Phosphorus-modified Pt@Cu surfaces for efficient electrocatalysis of hydrogen evolution

Phosphorus-modified Pt@Cu (Pt/P@Cu) was fabricated through a one-step method as a self-standing electrocatalyst, leading to increased surface activity sites, reduced charge transfer resistance and enhanced HER performance in neutral medium.

Preparation and characterization of a novel functionalized agricultural waste-based adsorbent for Cu2+ removal: Evaluation of adsorption performance using response surface methodology

In this study, it was aimed to the improvement of adsorption capability with a novel modification method based on increasing surface activity of flaxseed waste (FW), an agricultural waste product, and the investigation of its usability as an effective adsorbent for Cu2+ removal. The modification method involves functionalization of FW with iron by adding FeCl3 to medium in presence of N, N-Dimethyl-formamide, poly (N-vinyl-pyrrolidone), and hexamethylenetetramine. The effect of parameters was investigated by conventional univariate analysis. In addition, Response Surface Methodology (RSM) based on multivariate analysis was used to improve the performance of Cu2+ adsorption onto iron-modified flaxseed waste (M − FW). Cu2+ removal efficiency was achieved as 91.46% ± 2.34 (N = 2) at an equilibrium time of only 15 min under determined optimum conditions as Co: 75 ppm, pH: 4.7, and m: 0.23 g. RSM was successfully applied for the prediction of adsorption. Adsorption nature was as a single-layer adsorption with a maximum adsorption capacity (Qmax) of 7.64 mg/g. The adsorption mechanism, determined to be chemically controlled, an exothermic and non-spontaneous process. Furthermore, pH-dependent adsorption showed that electrostatic interactions between M − FW and Cu2+ ions play an important role in adsorption mechanism. The results of characterization studies showed that a large surface area was provided with increased porosity of structure and desired changes occurred in target functional structures with modification. Moreover, modification and reusability of M − FW were evaluated in terms of overall sustainability and waste management. The results indicated that M − FW has potential for usability to remove heavy metals like Cu2+ in environmental remediation applications.

An analysis of SmBa0.5Sr0.5Co2O5+δ double perovskite oxide for intermediate–temperature solid oxide fuel cells

The main obstacle to solid oxide fuel cells (SOFCs) implementation is the high operating temperature in the range of 800–1,000 °C so that it has an impact on high costs. SOFCs work at high temperatures causing rapid breakdown between layers (anode, electrolyte, and cathode) because they have different thermal expansion. The study focused on reducing the operating temperature in the medium temperature range. SmBa0.5Sr0.5Co2O5+δ (SBSC) oxide was studied as a cathode material for IT-SOFCs based on Ce0.8Sm0.2O1.9 (SDC) electrolyte. The SBSC powder was prepared using the solid-state reaction method with repeated ball-milling and calcining. Alumina grinding balls are used because they have a high hardness to crush and smooth the powder of SOFC material. The specimens were then tested as cathode material for SOFC at intermediate temperature (600–800 °C) using X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), electrochemical, and scanning electron microscopy (SEM) tests. The X-ray powder diffraction (XRD) pattern of SBSC powder can be indexed to a tetragonal space group (P4/mmm). The overall change in mass of the SBSC powder is 8 % at a temperature range of 125–800 °C. A sample of SBSC powder showed a high oxygen content (5+δ) that reached 5.92 and 5.41 at temperatures of 200 °C and 800 °C, respectively. High diffusion levels and increased surface activity of oxygen reduction reactions (ORRs) can be affected by high oxygen content (5+δ). The polarization resistance (Rp) of samples sintered at 1000 °C is 4.02 Ωcm2 at 600 °C, 1.04 Ωcm2 at 700 °C, and 0.42 Ωcm2 at 800 °C. The power density of the SBSC cathode is 336.1, 387.3, and 357.4 mW/cm2 at temperatures of 625 °C, 650 °C, and 675 °C, respectively. The SBSC demonstrates as a prospective cathode material for IT-SOFC

Effects of snake fungal disease on short-term survival, behavior, and movement in free-ranging snakes.

Pathogenic fungi are increasingly associated with epidemics in wildlife populations. Snake fungal disease (SFD, also referred to as Ophidiomycosis) is an emerging threat to snakes, taxa that are elusive and difficult to sample. Thus, assessments of the effects of SFD on populations have rarely occurred. We used a field technique to enhance detection, Passive Integrated Transponder (PIT) telemetry, and a multi-state capture-mark-recapture model to assess SFD effects on short-term (within-season) survival, movement, and surface activity of two wild snake species, Regina septemvittata (Queensnake) and Nerodia sipedon (Common Watersnake). We were unable to detect an effect of disease state on short-term survival for either species. However, we estimated Bayesian posterior probabilities of >0.99 that R. septemvittata with SFD spent more time surface-active and were less likely to permanently emigrate from the study area. We also estimated probabilities of 0.98 and 0.87 that temporary immigration and temporary emigration rates, respectively, were lower in diseased R. septemvittata. We found evidence of elevated surface activity and lower temporary immigration rates in diseased N. sipedon, with estimated probabilities of 0.89, and found considerably less support for differences in permanent or temporary emigration rates. This study is the first to yield estimates for key demographic and behavioral parameters (survival, emigration, surface activity) of snakes in wild populations afflicted with SFD. Given the increase in surface activity of diseased snakes, future surveys of snake populations could benefit from exploring longer-term demographic consequences of SFD and recognize that disease prevalence in surface-active animals may exceed that of the population as a whole.

EVALUATION OF MEDIAN LETHAL CONCENTRATION (LC ) 50 OF MYSTUS VITTATUS (BLOCH) FOR COPPER SULPHATE

The toxic effect of Copper on freshwater catfish Mystus vittatus was studied. The LC values of copper in Mystus 50 vittatus for 24, 48, 72 and 96 hours were 20.589, 16.497, 11.815 and 8.665 mg/L respectively. The cat fish was silvery grey in body in the control group throughout the experiment. The body colour changed from original silvery grey to dark colour in heavy metal treated fish. The fish maintained in freshwater behaved normal as usual. But when the fish was exposed to copper, erratic swimming, abnormal posture, dis-balance, sluggishness, imbalance in posture, increase in surface activity, opercular beating, and gradual loss of equilibrium and spreading of excess of mucus all over the surface of the body were observed.

Adsorption of Equimolar Mixtures of Cationic and Anionic Surfactants at the Water/Hexane Interface

In mixed solutions of anionic and cationic surfactants, called catanionics, ion pairs are formed which behave like non-ionic surfactants with a much higher surface activity than the single components. In equimolar mixtures of NaCnSO4 and CmTAB, all surface-active ions are paired. For mixtures with n + m = const, the interfacial properties are rather similar. Catanionics containing one long-chain surfactant and one surfactant with medium chain length exhibit a strong increase in surface activity as compared with the single compounds. In contrast, catanionics of one medium- and one short chain surfactant have a surface activity similar to that of the medium-chain surfactant alone. Both the Frumkin model and the reorientation model describe the experimental equilibrium data equally well, while the adsorption kinetics of the mixed medium- and short-chain surfactants can be well described only with the reorientation model.

Design of Surfactant Tails for Effective Surface Tension Reduction and Micellization in Water and/or Supercritical CO2.

The interfacial properties and water-in-CO2 (W/CO2) microemulsion (μE) formation with double- and novel triple-tail surfactants bearing trimethylsilyl (TMS) groups in the tails are investigated. Comparisons of these properties are made with those for analogous hydrocarbon (HC) and fluorocarbon (FC) tail surfactants. Surface tension measurements allowed for critical micelle concentrations (CMC) and surface tensions at the CMC (γCMC) to be determined, resulting in the following trend in surface activity FC > TMS > HC. Addition of a third surfactant tail gave rise to increased surface activity, and very low γCMC values were recorded for the double/triple-tail TMS and HC surfactants. Comparing effective tail group densities (ρlayer) of the respective surfactants allowed for an understanding of how γCMC is affected by both the number of surfactant tails and the chemistry of the tails. These results highlight the important role of tail group chemical structure on ρlayer for double-tail surfactants. For triple-tail surfactants, however, the degree to which ρlayer is affected by tail group architecture is harder to discern due to formation of highly dense layers. Stable W/CO2 μEs were formed by both the double- and the triple-tail TMS surfactants. High-pressure small-angle neutron scattering (HP-SANS) has been used to characterize the nanostructures of W/CO2 μEs formed by the double- and triple-tail surfactants, and at constant pressure and temperature, the aqueous cores of the microemulsions were found to swell with increasing water-to-surfactant ratio (W0). A maximum W0 value of 25 was recorded for the triple-tail TMS surfactant, which is very rare for nonfluorinated surfactants. These data therefore highlight important parameters required to design fluorine-free environmentally responsible surfactants for stabilizing W/CO2 μEs.

Experimental evaluation of cationic-Schiff base surfactants based on 5-chloromethyl salicylaldehyde for improving crude oil recovery and bactericide

In this study, a new family of cationic and cationic–Schiff Base surfactant was synthesized namely; N-(3-formyl-4-hydroxybenzyl)-N, N-dimethylhexadecan-1-aminium chloride (FHDHAC), (E)-N-(3-((butylimino)methyl)-4-hydroxybenzyl)-N,N-dimethylhexadecan-1-aminium chloride (4-IMHDAC), (E)-N-(3-((hexylimino)methyl)-4-hydroxybenzyl)-N,N-dimethylhexadecan-1-aminium chloride (6-IMHDAC) and (E)-N-(4-hydroxy-3-((octylimino) methyl)benzyl)-N,N-dimethylhexadecan-1-aminium chloride (8-IMHDAC) were prepared from 5-chloromethyl salicylaldehyde compound (5-CMS). The chemical structures of 5-CMS, 4-IMHDAC, 6-IMHDAC, and 8-IMHDAC are characterized using FTIR, 1H NMR instruments. The surface activity measurements of the prepared compounds showed a gradual increase in surface activity by increasing the alkyl chain length. Adsorption and micellization thermodynamic functions revealed the higher tendencies of the different surfactants towards adsorption at the organic/polar phase. The synthesized surfactants were evaluated in the enhanced oil recovery process and showed excellent efficiency (63.98%, 71.25%, and 75.72% for 4-IMHDAC, 6-IMHDAC, and 8-IMHDAC, respectively) during the recovery process near their critical micelle concentrations. The prepared surfactants showed high antimicrobial efficacy against different bacteria and fungi.

Influence of thermally induced structure changes in diluted β-lactoglobulin solutions on their surface activity and behavior in foam fractionation

Surface activity is an intrinsic protein feature, leading to the capability of aqueous protein solutions to form foam. This feature provides opportunities for downstream processing, such as usage of foam fractionation for purification. In order to investigate the impact of the surface activity on the performance of the foam fractionation process, protein solutions with different surface activity were produced by different thermal denaturation of aqueous β-lactoglobulin solutions. The effectiveness of the denaturation procedure was verified with circular dichroic spectroscopy, and the impact on surface activity was determined via dynamic surface tension measurement. The increased surface activity resulted in higher foamate flow rates. Furthermore, the effects could be correlated with secondary structure changes and with the dynamic surface pressure. The new result of this study is that the effect of the denaturation of a protein on foam fractionation depends on the protein concentration. At the lower feed concentration, effects became visible, which could not be observed at the higher concentration.

Effect of plasma-assisted laser pretreatment of hard coatings surface on the physical and chemical bonding between PVD soft and hard coatings and its resulting properties

This research reveals for the first time, how different surface pretreatments (including mechanical polishing, plasma etching, femtosecond laser texturing, and plasma-assisted femtosecond laser texturing) on the PVD hard coatings impact the physical and chemical bonding between PVD soft and hard coatings and its resulting properties. Therefore, the as-deposited TiAlN coatings were served as substrates for the following pretreatments and the deposition of WS2 soft coatings. The scratch tests and dry wear tests were carried out to investigate the adhesion and tribological performance of these WS2/TiAlN soft/hard composite coated samples. Results show that uniform and periodic nano-textures are fabricated on the TiAlN coatings surface by the plasma-assisted laser texturing, which results in high compressive stress and increased surface activity. Thus, the critical load of WS2 coatings deposited on the plasma-assisted laser textured TiAlN substrates (FN = 46 N) exhibits higher values in comparison with the WS2 coatings deposited on untreated TiAlN substrate (FN = 28 N). And, an obviously increasing in wear life of WS2 coatings from 2400 s to 5200 s is achieved by plasma-assisted laser texturing. Additionally, the growth mode of WS2 coatings deposited on the plasma-assisted laser pretreated TiAlN substrare is changed from Volmer–Weber model to Stranski–Krastanov model.

Strain effects on the Co oxidation state and the oxygen dissociation activity in barium lanthanum cobaltite thin films on Y2O3 stabilized ZrO2

Tensile strain increases surface activity of cobaltite cathode oxides like Ba(La)CoO3 for solid oxide fuel cells and electrolysers (SOFCs/SOECs).

Evaluation of surface activity of hot-dip galvanized steel after alkaline cleaning

The surface activity of hot-dip galvanized steel was evaluated after alkaline cleaning by exposing the cleaned specimens in humid supercritical carbon dioxide, followed by extraction and quantification of the formed corrosion products. Different free alkalinities of the cleaning bath were studied to obtain information on the evolution of zinc surface activity at different levels of surface etching. Surface reactivity of uncleaned galvanized steel is restricted and local, with major contributions from grain boundaries and intermetallic particles. Formation of zinc corrosion products took place in uncleaned samples exclusively on and around these sites. Al2O3 removal by alkaline cleaning gradually increased the surface activity. The major increase in surface activity was achieved when increasing the free alkalinity from 0.5 to 4.0 mEq/L, which was shown by formation of zinc corrosion products within zinc grains. The surface activity was confirmed by applying a titanium hexafluoride pretreatment on the cleaned panels and measuring the lateral microscale uniformity of the formed layer. The uniformity increased when larger areas of galvanized steel became activated by alkaline cleaning. Reactivity of zinc is rather difficult to quantify when setting up an industrial cleaning sequence for galvanized steel. Controlled exposure of cleaned samples in humid supercritical carbon dioxide, followed by quantification of oxidized zinc, provides a straightforward method to evaluate zinc reactivity.

Surface functionalization of nano MgO particles with nickel and cobalt

In the present work, nano magnesium oxide (MgO) particles were coated with nickel and cobalt to increase surface activity of the nano particles. Prior to coating process, surfaces of MgO particles were sensitized and then activated using SnCl2 and HCI, and PdCl2 and HCI solutions, respectively. In electroless coating bath, nickel sulfate (NiSO4·6H2O), cobalt sulfate (CoSO4.6H2O), sodium hypophosphite (NaH2PO2·H2O) and sodium citrate (Na3C6H5O7.5H2O) were used as Ni++ and Co++ sources, reducing agent and complexing agent, respectively. The morphology, characterization and chemical composition of coating were characterized by Raman spectroscopy, scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), x-ray diffraction and transmission electron microscope (TEM). Results showed that particle surfaces were coated by nickel and cobalt, and nickel deposition ratio compared to cobalt deposition was more successfully carried out. It was worthily noted that size of samples with coated nickel and cobalt did not converted from nano scale to micro scale, and the mobility and electro-kinetic nature of particles in electrolyte have an important effect on deposition mechanism of coatings.