Lifshitz-van Der Waals Acid-base Approach Research Articles

Strategy of selecting solvent systems for spherical agglomeration by the Lifshitz-van der Waals acid-base approach

A strategy for rationally selecting solvent systems of spherical agglomeration is proposed for the first time. It emphasizes that followed by crystallization and phase separation, spherical agglomeration can be achieved only when the solvent system can induce wetting and adhesion which are estimated by the Lifshitz-van der Waals acid-base approach. Especially for wettability of bridging liquid, solvent and anti-solvent, the strategy indicates that it is of great importance for a successful solvent system. Valid systems therefore are selected in the first place while invalid ones are removed effectively according to the wettability difference. Based on the strategy, valid solvent systems for cefotaxime sodium and benzoic acid spherical agglomeration were selected successfully from 720 and 2184 systems respectively without missing the reported systems. The strategy also predicted no valid systems for potassium chloride, maltitol and trisodium phosphate in the given solvent combinations, which agreed with the experiment results.

Design and mechanism of the formation of spherical KCl particles using cooling crystallization without additives

Potassium chloride crystals are cubic, which often leads to caking and greatly limits their applications. This caking can be overcome by modifying the crystal shape toward sphericity. Spherical particles have a high anti-caking ability and flowability. In this work, spherical KCl particles were prepared using a simple cooling crystallization process designed to function without additives. Among the four main processes in the crystallization of spherical particles, i.e., nucleation, growth, agglomeration, and attrition, agglomeration is the greatest contributor to the formation of spherical KCl particles, which were prepared following the principle that the adhesion force must be larger than the dispersion force. The adhesion free energy between KCl particles and solvents (i.e., water, n-hexane, formamide, diazomethane, methanol, ethanol, ethyl acetate, ethylene glycol, and dimethyl sulfoxide) was calculated using the Lifshitz–van der Waals acid–base approach, and water was found to be the most appropriate solvent because of its attractive interaction with the crystals. According to the relationship between the adhesion force and dispersion forces, we found that the stirring rate should be lower than 1300 rpm. Additionally, the effects of stirring rate and cooling rate on the KCl products were investigated and optimized, and the optimal conditions were found to be 400–500 rpm and 10–15 min/°C, respectively. All of the spherical KCl products prepared under the optimal conditions show a better morphology, flowability, and anti-caking performance than the original crystals.

Physico-chemical surface properties of microalgae

This study reports a comprehensive set of experimentally measured physico-chemical surface properties of 12 different microalgae including fresh and seawater species of green algae, diatoms and cyanobacteria. The surface free energy and its components including the acid-base (AB), van der Waals (LW), electron donor/acceptor parameters were quantified based on contact angle measurements along with the Lifshitz–van der Waals acid–base approach using the probe liquid surface tension parameters proposed by van Oss et al. as well as by Della Volpe and Siboni. Moreover, the zeta and surface potentials of all species were determined using electrophoretic mobility measurements along with using Smoluchowski's model. Finally, the free energy of cohesion of the microalgae was also determined based on the calculated surface energy properties. The results showed that the electron donor parameter correlated well with the free energy of cohesion in all groups of microalgae. Moreover, species known to form colonies and exhibit benthic cultures had distinctly hydrophobic surfaces compared to microalgae prefering planktonic growth. These results indicate the importance of surface hydrophobicity for causing biofouiling or flocculation of cultures. Finally, the zeta potentials did not show a distinctive trend with the types of microalgae but the surface potentials were markedly larger for the salt water species. The reported methods and data are expected to provide critical information for researchers and technology developers concerned with cell to cell and cell to substrata interactions of microalgae in algal biomass cultivation and harvesting, biofouling of membranes and surfaces, as well as cell-surface interactions in photosynthetic microbial fuel cell technologies.

Synergetic Effect of Grit-Blasting and Atmospheric Cold Plasma Pretreatments on the Surface Free Energy of a Fibreglass/Epoxy Vinyl Ester Composite

For the first time, the efficiency of different surface pretreatment approaches prior to adhesive bonding of a fibreglass-reinforced epoxy vinyl ester thermoset composite has been investigated. It was found that grit-blasting generally had a negligible effect on the surface free energy (SFE) calculated using the Owens, Wendt, Rabel, and Kaelble method, as well as the Lifshitz–van der Waals/acid-base (LWAB) approach. However, contrary to abrading, grit-blasting has shown its efficiency to flatten sharp surface irregularities and introduce surface roughness features suitable to adhesive bonding processes. With or without a previous grit-blasting step, argon gas atmospheric cold plasma treatment has shown a slight to moderate efficiency in increasing the SFE polar component of the composite. However, it was found that the addition of 0.07% oxygen to the argon plasma readily allows an important gain in the SFE polar component. Indeed, when processed at a speed of 30 m/min on a previously grit-blasted composite surface, the Ar/O2 atmospheric cold plasma treatment increases the surface free energy to values >73 mJ/m2, making the surface condition optimized for structural adhesive bonding. An oxidation mechanism of the composite surface exposed to atmospheric cold plasma was suggested on the basis of correlations established between the polar part of SFE obtained from the Owens et al. method, acid/base components calculated using the LWAB approach, and ATR infrared spectroscopy signatures obtained for a model polyolefin material.

Interfacial Energetics of Bacterial Silicification

Silica nanoparticle size distributions were measured from transmission electron micrographs of bacterial cells in thin-sectioned hot spring sediment samples, as well as specimens from laboratory experiments on bacterial silicification. Diameters of silica nanoparticles on bacterial cells were smaller than corresponding values of those occurring away from bacteria in the same fields of view. Regression analysis of the particle size data and application of the Lifshitz-van der Waals Acid-Base approach to evaluations of solid surface energy established that the size difference extends from a nearly 40% decrease in the mean interfacial energy of silica nanoparticles on bacteria (0.9 mJ/m 2 ) as opposed to free in aqueous suspension (1.2 mJ/m 2 ). In thermodynamic terms, the lower interfacial energy serves to reduce equilibrium solubility values, and enhance nucleation rates, of silica nanoparticles on bacteria cells. The well documented culmination of these events in hot spring sediments and experimental studies is rapid preferential silicification and structural preservation of bacterial cells.

Conformational Reorientation of Immunoglobulin G During Nonspecific Interaction with Surfaces

To achieve a better understanding of the nonspecific adsorption process of proteins on solid surfaces, the mechanism of this interaction was investigated by a model system comprising the structurally flexible ("soft") protein goat anti-rabbit immunoglobulin G and a set of chemically defined surfaces. The thermodynamic properties of both protein and surfaces were derived from contact angle measurements by applying the Lifshitz-van der Waals acid-base approach, and the Gibbs free enthalpy of interaction was calculated. The protein shows two conformational states, one hydrophobic and the other hydrophilic. The interaction energy indicates that the hydrophobic conformation favorably adsorbs onto the surfaces. With real-time binding kinetics, measured by a supercritical angle fluorescence biosensor, we show that during the nonspecific adsorption the protein performs a reorientation in its three-dimensional amino acid structure from a hydrophilic to a hydrophobic molecular structure. Unlike the rates of adsorption and desorption, the transition rate is independent of the type of surface and only influenced by the structural reorganization of the protein.

Surface properties of polyethylene after low-temperature plasma treatment

The effect of oxygen and ammonia plasma treatments on changes of the surface properties of linear high-density polyethylene (HDPE) was studied. Surface energies of the polymer substrates were evaluated by contact angle measurements using Lifshitz-van der Waals acid-base approach. The surface energy of untreated HDPE is mainly contributed by Lifshitz-van der Waals interactions. After 5 min of plasma treatment, hydrogen bonds are formed on the surface, which is reflected in predominant acid-base interactions. The SEM results obtained demonstrate considerable changes of the surface roughness due to different types of the plasma gas used. Evolution of oxygen- or amino-containing moieties was detected by XPS and ATR FT IR. The prepared polyethylene surfaces were used as a basic support for further fabrication of novel hybrid biocomposite sandwich structures.

Assessing short-range membrane–colloid interactions using surface energetics

The contribution of acid–base (AB) (polar) interactions to the total interaction energy between membranes and colloids was investigated. The surface energetics of several membranes and colloids were evaluated using the Lifshitz–van der Waals acid-base approach. This provides the van der Waals (LW) and polar interaction energies between various surfaces from measurements of contact angles of different probe liquids on these surfaces. In addition, the surface potentials of the membranes and colloids were determined using electrokinetic measurements, yielding the electrostatic (EL) interaction between these surfaces. The three interaction energy components (LW, EL, and AB) were combined according to the extended Derjaguin–Landau–Verwey–Overbeek (extended DLVO or XDLVO) approach to evaluate membrane–colloid interaction energies. Predictions of interaction energy based on the XDLVO approach were compared to the corresponding predictions from the classical DLVO theory. For all the membrane–colloid combinations studied, the DLVO potentials were quite similar. However, inclusion of AB interactions resulted in a substantially different (qualitative and quantitative) prediction of short-range (separation distances <5 nm) interaction energies for several of the membrane–colloid combinations investigated. Finally, all of the membranes studied were found to have substantially low surface energies compared to the colloids and the interaction energy between the membranes and colloids was primarily dictated by the surface energies of the colloids. Fouling experiments for a membrane and three colloids supported the fouling trends predicted by the XDLVO approach.

Comparison of the Lifshitz–van der Waals/acid–base and contact angle hysteresis approaches for determination of solid surface free energy

Total surface free energy, γS TOT, for several solids (glass, PMMA, duralumin, steel and cadmium) was calculated from the surface free energy components: apolar Lifshitz–van der Waals, γS LW, and acid–base electron–donor, γS -, and electron–acceptor, γS +. Using van Oss and coworkers' approach (Lifshitz–van der Waals/acid–base (LWAB) approach), the components were determined from advancing contact angles of the following probe liquids: water, glycerol, formamide, diiodomethane, ethylene glycol, 1-bromonaphthalene and dimethyl sulfoxide. Moreover, receding contact angles were also measured for the probe liquids, and then applying the contact angle hysteresis (CAH) approach very recently proposed by Chibowski, the total surface free energy for these solids was calculated. Although the thus determined total surface free energy for a particular solid was expected to depend on the combination of three probe liquids used (LWAB approach), as well as on the kind of the liquid used (CAH approach), surprisingly the average values of the surface free energy from the two approaches agreed very well. The results obtained indicate that both approaches can deliver some useful information about the surface free energy of a solid.

Investigation of the effect of substrata on the surface free energy components of silica gel determined by thin layer wicking method

The components of surface free energy of silica gel deposited on glass plates, aluminium or plastic sheets (commercial Merck's plates for TLC) were determined by applying two theoretical approaches: the Lifshitz-van der Waals acid-base approach (LWAB), the geometric mean of apolar and polar interactions approach (GM). The thin layer wicking method was applied. Besides, from the measured contact angles of probe liquid (diiodomethane, α-bromonaphthalene, water, formamide, glycerol and ethylene glycol) surface free energy components were calculated for the substrata on which the silica gel was deposited. In this case the equation of state (ES) was additional by applied. The study has shown that both the kind of substratum and that of the chambers used for measuring the penetration rate of the liquid do not influence the calculated values of the surface free energy components of silica gel. The components calculated from the two models of interfacial interactions: γLWs and γABs or γds and γps appeared to be practically the same if diiodomethane and α-bromonaphthalene were considered as weakly polar liquids, i.e. donor-acceptor interactions in the surface tension were taken into account. However, when γl+ and γl− of these liquids are neglected, considerable differences occur, particularly in the determined value of Lifshitz-van der Waals component. The values of the total surface free energy of substrata calculated by applying three thermodynamic approaches are very similar, but if diiodomethane and α-bromonaphthalene are considered as weakly polar liquids this similarity is more distinct.

Determination of physicochemical parameters of solids covered with conditioning films from groundwaters using contact angles. Comparative analysis of different thermodynamic approaches utilizing a range of diagnostic liquids

Contact angles of two polar [water (w) and formamide (f)] and two apolar diagnostic liquids [α-bromonaphthalene (α-br) and diiodomethane (di)] were measured on substrata (andesite, shale, stainless steel and polypropylene) either clean or coated with conditioning films from groundwaters collected from shallow and deep bores. The equation of state (ES), the Lifshitz-van der Waals acid-base approach (LWAB) and the geometric mean equation (GME) were evaluated for calculation of the following parameters: surface free energy ( γ s) and its components ( γ s p = polar and γ s d = apolar components in GME as well as γ s lw, γ s − and γ s + = Lifschitz-van der Waals, electron-donor and electron-acceptor components in LWAB) in addition to solid-liquid interfacial tension ( γ SL), particle-solid interfacial tension ( γ SP) and free energy of adhesion of particle to substrata ( ΔF adh). The Gram-negative bacterium SW8 grown under carbon-limited conditions was used as a model particle. On high-energy surfaces, γ s was highest in approaches with water whereas on synthetic medium-energy materials all approaches produced similar estimates for γ s. On many mineral surfaces, however, approaches with α-br provided significantly larger γ s than those with di. On low-energy surfaces, apolar liquids generally provided higher estimates for γ s than polar liquids. The generally similar trends for γ s in approaches with polar liquids differed from those observed in approaches with apolar liquids. In GME, the values of γ s d correlated only between pairs with the same apolar liquid. The trends for γ s lw and γ s d were similar in approaches with di. γ s p determined with polar liquids generally correlated with each other and the trends were similar to those of γ s −, but not γ s + · γ s − was practically identical with γ s p calculated with the GME pair f/w, as were γ s calculated with di or α-br in ES and γ s lw obtained in triplets with the respective apolar liquid. The trends of γ s-ES of water and formamide were similar to those of γ s − and of γ s p in GME pairs involving polar liquids. γ SL, γ SP and ΔF adh of approaches involving water contact angles differed considerably; however, similar trends were obtained with all approaches for γ SL and with four approaches for ΔF adh. Every approach produced a unique trend for γ SP. Results obtained with ES on most interfaces were not consistent with fundamental premises of the equation of state theory and values for the dispersive component of surface free energy appeared to be generally underestimated in the GME approach. LWAB w/f/di was found to be the most suitable approach for surface analysis of the interfaces investigated in this work.

Adhesion of a Primary Colonizing Marine Bacterium to Conditioned Substrata Correlates Occasionally with Physicochemical Parameters Derived from Contact Angles

Stainless steel, germanium, polypropylene, and perspex were coated with films derived from marine and freshwater samples and from solutions of model compounds (bovine serum albumin, lactoglobulin, myoglobin, and humic acids). Contact angles of water, formamide, and diiodomethane were measured on clean and conditioned substrata as well as on carbon- and nitrogen-limited cells of the Gram-negative bacterium SW8. The following physicochemical parameters were calculated by the Lifshitz–van der Waals acid–base approach: surface free energy and its three components (Lifshitz–van der Waals, electron-donor, and electron-acceptor), solid–water and bacterium–water interfacial tensions, and free energy of adhesion of bacterium to substratum. Although strongly affected by conditioning films, adhesion of carbon- and nitrogen-limited SW8 to clean and coated surfaces generally did not correlate with contact angle-derived physicochemical parameters. The only exception was attachment of carbon-limited SW8 to clean and coated germanium surfaces, where good correlations were obtained with the electron-donor component of surface free energy, the substratum–water interfacial tension, and the free energy of adhesion, suggesting that electron-donor components did play a major role in the adhesion of this phenotype to these surfaces.

Comparative analysis of thermodynamic approaches and diagnostic liquids for determination of contact angle-derived physicochemical parameters of solids coated with conditioning films: A practitioner's perspective

The equation of state (ES), the Lifshitz-van der Waals acid-base approach (LWAB), and the geometric mean equation (GME) were evaluated for calculation of physicochemical parameters from contact angles of the four diagnostic liquids: water (w), formamide (f), α-bromonaphthalene (α-br), and diiodomethane (di) measured on clean and conditioning film-coated substrata (stainless steel, germanium, polypropylene, perspex). Surface free energy and its components (dispersive and polar components in GME, as well as Lifshitz-van der Waals, electron-donor and electron-acceptor components in LWAB) were assessed in all approaches with all liquid combinations possible. The Gram-negative bacterium SW8 grown under carbon-limited conditions was used to calculate the solid-bacterium interfacial free energy and the free energy of adhesion of SW8 to solid substrata. These two parameters and the solid-liquid interfacial free energy were calculated only for combinations of diagnostic liquids that included water contact angles. Actual values of physicochemical parameters on high and low energy interfaces often differed between approaches or within an approach when different diagnostic liquids or combinations thereof were used. However, the same values of surface free energy were obtained on high and medium energy surfaces with the combinations LWAB w/f/di, LWAB w/f/α-br, ES f, GME f/α-br, and GME f/di. Approaches involving polar liquids produced similar trends for surface free energy and solid-liquid interfacial free energy. Results obtained with ES on high and low energy substrata were not consistent with fundamental premises of the theory and the dispersive component of surface free energy was generally underestimated in the GME approach. LWAB w/f/di was found to be the most suitable approach for analysis of the surfaces investigated in this work.

Conditioning Film-Induced Modification of Substratum Physicochemistry—Analysis by Contact Angles

Stainless steel, germanium, polypropylene, and perspex were coated with films derived from marine and freshwater samples and from solutions of model compounds (bovine serum albumin, lactoglobulin, myoglobin, and humic acids). Contact angles of water, formamide, and diiodomethane measured on clean and conditioned interfaces were used to calculate physicochemical surface properties by the Lifshitz–van der Waals acid–base approach, including interfacial parameters for the interaction of carbon- and nitrogen-limited cells of the Gram-negative bacterium SW8 with these surfaces. The interaction parameter φ was evaluated as an indicator of the chemical constitution of conditioned interfaces. Surface free energy and its Lifshitz–van der Waals component were modified by 59 and 66% of conditioning films, respectively, but these alterations were relatively small. The acid–base components of surface free energy and the free energy of adhesion of bacteria to substrata were, however, substantially affected by the coatings. Most films did not modify the interaction parameter φ. Those which did increased the φ of polymeric surfaces and decreased it on stainless steel. The solid–water interfacial tension (γSW), which was larger than the solid–bacterium interfacial tension (γSB) on 97% of surfaces, was reduced by 61% of the conditioning films and increased by 14% of the coatings. The γSBof nitrogen-limited cells was smaller than the γSBof carbon-limited organisms on 92% of substrata. Values of γSBof carbon- and nitrogen-limited organisms were negative on 17 and 69% of the surfaces, respectively. More coatings modified the γSBof nitrogen-limited cells (97%) than the γSBof carbon-limited SW8 (72%). The free energy of adhesion was negative on 31% of interfaces but similar for both phenotypes. It was altered by 91% of conditioning films, which generally reduced its value.