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The interfacial properties of the system cerium(IV) oxide/poly(sodium 4-styrenesulfonate) (NaPSS) aqueous solution were studied in a broad pH region by means of inner surface ...potential, zeta potential and adsorption measurements. Surface potential data were obtained using a single crystal electrode, while zeta potential and adsorption data were obtained using synthetized CeO2 nanoparticles. In order to examine the adsorption of NaPSS on cerium(IV) oxide in detail, surface and electrokinetic potentials of ceria particles were measured in the absence and in the presence of NaPSS.
The results of surface potential measurements showed that negatively charged NaPSS molecules exhibit high adsorption affinity towards the CeO2 surface. Titration with NaPSS in the acidic region, where the ceria surface is originally positively charged, suggested that adsorption of negatively charged NaPSS molecules compensates positive charge at the surface and adsorption proceeds until the reversal of surface charge produces a critical value of the potential affecting the state of adsorbed NaPSS molecules. Adsorption of NaPSS on cerium(IV) oxide in the examined pH range was additionally confirmed by zeta potential and adsorption measurements in sodium chloride aqueous solution. From the measured pH dependence of the electrokinetic potential of CeO2 nanoparticles, isoelectric point was determined to be pHiep ≈ 5.4, while the electrokinetic potential in the presence of NaPSS was found to be negative in the whole investigated pH region. Finally, adsorption measurements were carried out which enabled the determination of the maximum surface concentration of the adsorbed polyelectrolyte as Γmax ≈ 1 μmol m−2.
Adsorption of polyions, strongly charged poly(N-ethyl-4-vinylpyridinium) cation (P4VP) weakly charged poly(allylammonium) cation (PAH) and weakly charged poly(acrylate) anion (PAA) on TiO
2
surface ...was investigated. The selected polyions have different functional groups and degree of polyion ionization, which affects the interactions with the TiO
2
surface. The effect of polyion adsorption on the inner surface potential and the electrokinetic potential were measured and analyzed. The inner surface potential of TiO
2
was measured by means of single crystal (SCr) electrodes with two different crystal orientation (001) and (100). The electrokinetic potential of titania particles was obtained from electrophoretic measurements. In suspensions, uncoated TiO
2
particles tend to aggregate and aggregation is reduced after polyion adsorption. The process of aggregation was monitored measuring the size of the particles. Since the surface charge of TiO
2
and the degree of polyion ionization depend on the composition of the solution, namely on pH and ionic strength, the adsorption of polyions on TiO
2
also depends on these parameters. The contribution of the surface charge and degree of polyion ionization of the selected polyelectrolytes to the rate of aggregation of TiO
2
particles was examined. It was found that in the case of weak polyelectrolyte the degree of polyanion ionization plays significant role in stabilization of titania suspensions.
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•The composition of nanoparticles affects their surface charge density.•Addition of GA increases size of Z and Z/R NPs.•Interactions with GA are the most intensive at pH = 4 for both ...Z and Z/R NPs.
The objective of this study was to investigate interactions of zein (Z) and zein/rosin (Z/R) nanoparticles with gum arabic (GA), at different pH. Nanoparticles were firstly prepared by antisolvent precipitation of biopolymers from aqueous ethanol solutions. Nanoparticles suspensions were then dialyzed against water in order to remove ethanol and other impurities, and water suspensions of zein and zein/rosin nanoparticles were obtained. It was shown that composition of nanoparticles affects their surface charge density. Zeta potential of nanoparticles was positive without GA and changed to negative after addition of GA, at all pH tested. SEM analysis proved both Z and Z/R nanoparticles to be spherical and in size around 200 nm. The effect of addition of GA on particle size was determined using dynamic light scattering method. It was found that addition of GA increases size of nanoparticles at pH = 4 and pH = 5.5, from 150 – 220 nm to 250 – 320 nm. However, at pH = 3 it causes aggregation process, and diameter of particles increases up to few micrometres. Isothermal titration calorimetry was used to measure enthalpy changes in reaction between Z or Z/R nanoparticles and GA. Results showed that reaction between GA and Z or Z/R NPs is exothermic at each pH tested, except for Z NPs at pH = 3, where it was endothermic. At presented pHs, Z/R NPs were less charged compared to Z NPs, and their surface get saturated with GA molecules more rapidly. Z NPs showed greater enthalpy change in reaction with GA, compared to Z/R NPs.
This study was carried out with the aim of establishing how the outcomes of polyelectrolyte multilayer formation can be predicted on the basis of the results of complexation studies in solution and
. ...For this purpose, the correlation between the processes of complex and multilayer formation involving three pairs of vinylic polyions in solutions of binary 1 : 1 sodium salts (NaX; X = F, Cl, Br, I, NO
, ClO
) was explored by means of dynamic and electrophoretic light scattering, potentiometry, microcalorimetry, spectrophotometry and quartz crystal microbalance. The gradual reactant mixing in solution at lower salt concentrations resulted in a Fuoss-Sadek sequence of events (primary complexes → secondary complexes → 1 : 1 flocculate), whereby the obtained nano-complexes could be successively overcharged. At high salt concentration and with excess polycation present, metastable nano-complexes and precipitates containing surplus of positively charged monomers were formed. The amount of extrinsically compensated charge was in accord with the polycation affinities toward counteranions, established by monitoring the electrolyte-induced aggregation of positively charged nano-complexes. Perfect analogy with respect to counteranion influence on the amount of adsorbed polycation was noticed for corresponding multilayers. Aside from providing a deeper understanding of interpolyelectrolyte neutralization, the gained insights can also be used to steer the polyelectrolyte multilayer composition and properties.
Among various parameters that influence the formation of polyelectrolyte complexes and multilayers, special emphasis should be placed on ion-specific and solvent effects. In our study, we ...systematically examined the above-mentioned effects on poly(diallyldimethylammonium chloride) (PDADMACl)-sodium poly(4-styrenesulfonate) (NaPSS) complexation in solution and at the surface by means of dynamic light scattering, ellipsometry and atomic force microscopy measurements. As solvents, we used water and water/ethanol mixture. The obtained results confirm the importance of ion-specific and solvent effects on complexes prepared in solution, as well as on multilayers built up on a silica surface. The experiments in mixed solvent solution showed that at a higher ethanol mole fraction, the decrease in monomer titrant to titrand ratio, at which the increase in the size of complexes is observed, takes place. The difference between chloride and bromide ions was more pronounced at a higher mole fraction of ethanol and in the case of positive complex formation, suggesting that the larger amount of bromide ions could be condensed to the polycation chain. These findings are in accordance with the results we obtained for polyelectrolyte multilayers and could be helpful for designing polyelectrolyte multilayers with tuned properties needed for various applications, primarily in the field of biomedicine.
In this study, the surface properties of Ti/TiO2 substrate before and after the adsorption of polyelectrolytes were investigated. As model polyelectrolytes, strongly charged polycation ...poly(diallyldimethylammonium) (PDADMA) and strongly charged polyanion poly(4-styrenesulfonate) (PSS) were used. Initially, the bare titanium substrate was characterized by means of ellipsometry, atomic force microscopy (AFM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and measurements of inner surface potential using crystal electrode (CrE). It was shown that the substrate surface is very smooth with the roughness of 3.5 nm and oxide layer thickness of 3.8 nm. After the adsorption of PDADMA and PSS, polyelectrolyte-coated titanium surface was examined using the above-mentioned methods under the same conditions. It was found that both PDADMA cations and PSS anions form a stable polymeric nanofilm on Ti/TiO2 surface that partially covers the surface, without significant impact on the surface roughness. The corrosion protection effectiveness values indicate that the corrosion properties were greatly enhanced upon polyion adsorption and polyelectrolyte coating formation on the flat TiO2 surface. The obtained results were additionally confirmed by inner surface potential measurements. According to the methods employed, PDADMA nanofilm modification offers enhanced corrosion protection to the underlying titanium material in sodium chloride electrolyte solution.
Preventing bacterial attachment to surfaces is the most efficient approach to controlling biofilm proliferation. The aim of this study was to compare anti-adhesion potentials of 5 and 50 mmol/L ...polyelectrolyte multilayers of poly(allylamine hydrochloride)/poly(sodium 4–styrenesulfonate), poly(4-vinyl-
-ethylpyridinium bromide)/ poly(sodium 4–styrenesulfonate), and poly(4-vinyl-
-isobutylpyridinium bromide)/poly(sodium 4–styrenesulfonate) against
. Glass surface was covered with five polyelectrolyte layers and exposed to bacterial suspensions. Poly(4-vinyl-
-ethylpyridinium bromide)/poly(sodium 4–styrenesulfonate) was the most effective against bacterial adhesion, having reduced it by 60 %, followed by poly(4-vinyl-
-isobutylpyridinium bromide)/poly(sodium 4– styrenesulfonate) (47 %), and poly(allylamine hydrochloride)/poly(sodium 4–styrenesulfonate) (38 %). Polyelectrolyte multilayers with quaternary amine groups have a significant anti-adhesion potential and could find their place in coatings for food, pharmaceutical, and medical industry.
Barley (
L.) is unjustly neglected today as a food grain. Interest in the use of barley in the food industry has increased recently. The reason for this is its content of dietary fibre, especially ...β-glucan, which has been shown to reduce blood cholesterol and lower blood sugar levels. The main nutritional components of barley and barley products, besides the mentioned β-glucan, are starch, sugar, proteins, fat and ash. Although not common in the production of bakery products, barley can be very easily involved in the production of the same products, and such products have improved nutritional characteristics and acceptable sensory characteristics, which make them desirable. Barley has great potential for use in a wide range of cereal-based foods as a partial or full replacement for currently used grains (such as wheat, oats, rice and corn). This article provides basic and general information about the use of barley in food and the processing of barley grains for use in the manufacturing of cereal-based products, with particular attention to the use of barley in the manufacturing of bread (flatbread and leavened bread), noodles and pasta, muffins and cakes and cookies and biscuits.
Numerous studies on the health and functioning of veterans and former prisoners of war have shown that the experience of war captivity is one of the most difficult human experiences. Captivity is ...often characterized by extremely difficult and inhumane conditions, as well as exposure to various forms of both psychological and physical abuse. Such traumatic experiences can lead to serious psychological consequences that can last for years, even decades after release from captivity. The aim of this paper is to present a brief overview of research that points to the specifics of wartime captivity and the long-term psychological consequences in veterans of former camp detainees, as well as the consequences suffered by their families and factors that, apart from the intensity of the trauma, contribute to the emergence and persistence of psychological disorders. From the presented research, it can be concluded that former prisoners of the camp represent an extremely vulnerable group of the social community and require long-term appropriate treatment, while the needs of veterans' families should not be neglected, with the necessity of including spouses and children in psychological and psychosocial treatments.
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