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The thickness of the thin wetting film depends on disjoining pressure forces, and it evolves with pH evolution due to brine acidification at the physical and chemical conditions of geological carbon dioxide storage becoming thinner in response to dewetting. In the literature, molecular dynamic simulation (MDS) studies have been employed to understand the effect of pressure/capillary pressure on the thin wetting film evolution. In this paper, a theoretical approach based on the Frumkin–Derjaguin Equation (FDE), models of electric double layer repulsion, and van der Waals forces have been used for the calculation of the wetting film thickness. The approach excluded hydration forces contribution to disjoining pressure forces due partly to its poorly understood nature, and partly to the high salinity conditions encountered in geological carbon storage. Due to its promising global storage capacity compared to other lithologies, the carbon dioxide–brine–silica systems was chosen to simulate sandstone saline aquifers. The validation of the model benefited much from literature resources on data and a universal model of carbon dioxide–brine interfacial tension. Calculated results confirm pH-induced dewetting and they follow trends controlled by pH and pressure as found in the literature. The novelty of the paper can be seen from the fact that it has demonstrated a theoretical supplement to MDS studies in addition to justifying the fundamental utility and versatility of the FDE. Moreover, the paper links for the first time, a transcendental equation to the thin wetting film theory encountered in the carbon dioxide–solid–brine system found in geological carbon storage. [ABSTRACT FROM AUTHOR]

Abstract The thickness of the thin wetting film depends on disjoining pressure forces, and it evolves with pH evolution due to brine acidification at the physical and chemical conditions of geological carbon dioxide storage becoming thinner in response to dewetting. In the literature, molecular dynamic simulation (MDS) studies have been employed to understand the effect of pressure/capillary pressure on the thin wetting film evolution. In this paper, a theoretical approach based on the Frumkin–Derjaguin Equation (FDE), models of electric double layer repulsion, and van der Waals forces have been used for the calculation of the wetting film thickness. The approach excluded hydration forces contribution to disjoining pressure forces due partly to its poorly understood nature, and partly to the high salinity conditions encountered in geological carbon storage. Due to its promising global storage capacity compared to other lithologies, the carbon dioxide–brine–silica systems was chosen to simulate sandstone saline aquifers. The validation of the model benefited much from literature resources on data and a universal model of carbon dioxide–brine interfacial tension. Calculated results confirm pH-induced dewetting and they follow trends controlled by pH and pressure as found in the literature. The novelty of the paper can be seen from the fact that it has demonstrated a theoretical supplement to MDS studies in addition to justifying the fundamental utility and versatility of the FDE. Moreover, the paper links for the first time, a transcendental equation to the thin wetting film theory encountered in the carbon dioxide–solid–brine system found in geological carbon storage.

This article aims to study the effects of particle packing and inter-particle force on the rheological behaviors of binary cement paste. Fly ash (FA), ground granulated blast furnace slag (GGBFS), and limestone powder (LP) were added by 10 – 40% of cement weight to prepare the binary binder. The particle packing of each binary binder was analyzed based on the close packing theory and bulk density test. Atomic force microscopy and direct shear method were used to investigate the Hamaker constant and friction coefficient of different binders. Fresh pastes of every binder were prepared with variable solid volume fractions (w/b is 0.50, 0.55, and 0.60), and the rheology was measured by a rotary rheometer. Eventually, two empirical models were proposed to predict the yield stress and plastic viscosity of paste based on the porosity, friction coefficient, and w/b obtained from the experiments, and the accuracy of these new models was verified by ANOVA and p-value approach. The results show that particle packing and inter-particle force play a collaborative role in determining the rheological behavior of paste. Increasing particle packing or reducing inter-particle force (i.e., decreasing porosity or friction coefficient) benefits the enhancement of paste rheology. Moreover, an increase in the Hamaker constant leads to higher friction coefficients for binders. Comparisons between the predicted and experimental results demonstrated that these empirical models accurately capture the rheological behaviors of fresh pastes. [ABSTRACT FROM AUTHOR]

A simple relationship between the Hamaker constant and the Hansen solubility parameters for non-polar liquids is derived by combining a Hamaker constant/surface tension relationship derived by Israelachvili and a Hansen solubility parameters/surface tension relationship derived by Abbott. With this relationship, one can easily estimate the Hamaker constant of non-polar liquids on the basis of the database of the Hansen solubility parameters. This is an entirely new method for calculating the Hamaker constant without recourse to data on the frequency-dependent dielectric permittivity of those substances (which are required for the rigorous Lifshitz theory) and laborious numerical calculations. [ABSTRACT FROM AUTHOR]

This review article is devoted to the colloidal properties of fullerene solutions. According to generally accepted understandings, all solvents in relations to fullerenes are divided into "good", "poor", and "reactive". We have consistently considered the state of fullerenes in these systems. In "good", predominantly non-polar aromatic solvents and CS2, non-equilibrium dissolution methods lead to the formation of colloidal aggregates, whereas the utilization of equilibrium methods results in the formation of molecular solutions. The latter, however, have some unusual properties; new results considered in this review confirm previously expressed ideas about colloidal properties of these solutions. In "poor" (polar) solvents, lyophobic colloidal systems appear. Both "bottom-up" and "top-down" methods of preparation are well documented in the literature. However, N-methylpyrrolidine-2-one, DMSO, and DMF dissolve fullerenes quite easily and with less energy consumption. These solvents can be considered a subset of "poor" solvents that have some features of being "reactive" at the expense of basic properties. New data confirm that hydrosols of fullerenes are typical hydrophobic colloids that obey the Schulze–Hardy rule and other regularities in the presence of electrolytes. Organosols in acetonitrile and methanol are much less stable with respect to the effects of electrolytes. This allows us to assume a non-DLVO stabilizing factor in the hydrosols. Accordingly, a new estimate of the Hamaker constant of fullerene–fullerene interaction is proposed. In DMSO and DMF, the coagulation of fullerene sols is hindered due to strong solvation with these basic solvents. [ABSTRACT FROM AUTHOR]

Casimir–van der Waals forces are important in the self-assembly processes of nanoparticles. In this paper, using a hybrid approach based on Lifshitz theory of Casimir–van der Waals interactions and corrections due to the shape of the nanoparticles, it is shown that for non-spherical nanoparticles, the usual Hamaker approach overestimates the magnitude of the interaction. In particular, the study considers nanoplates of different thicknesses, nanocubes assembled with their faces parallel to each other, and tilted nanocubes, where the main interaction is between edges.

A simple relationship between the Hamaker constant and the Hansen solubility parameters for non-polar liquids is derived by combining a Hamaker constant/surface tension relationship derived by Israelachvili and a Hansen solubility parameters/surface tension relationship derived by Abbott. With this relationship, one can easily estimate the Hamaker constant of non-polar liquids on the basis of the database of the Hansen solubility parameters. This is an entirely new method for calculating the Hamaker constant without recourse to data on the frequency-dependent dielectric permittivity of those substances (which are required for the rigorous Lifshitz theory) and laborious numerical calculations.

Casimir–van der Waals forces are important in the self-assembly processes of nanoparticles. In this paper, using a hybrid approach based on Lifshitz theory of Casimir–van der Waals interactions and corrections due to the shape of the nanoparticles, it is shown that for non-spherical nanoparticles, the usual Hamaker approach overestimates the magnitude of the interaction. In particular, the study considers nanoplates of different thicknesses, nanocubes assembled with their faces parallel to each other, and tilted nanocubes, where the main interaction is between edges. [ABSTRACT FROM AUTHOR]

Surface potential is a key electrochemical property of colloids in the study of particle interactions. However, the specific ion effects are not involved in the existing measuring methods. In this study, approaches for the estimation of the surface potential of montmorillonite with or without consideration of the specific ion effects were explored through the montmorillonite particle aggregation in the presence of Li+, Na+, and K+ ions. The montmorillonite aggregation process exhibited remarkable specific ion effects, and the critical coagulation concentration (CCC) values show the following: Li+ (271.8 mm) > Na+ (130.8 mm) > K+ (85.04 mm). Based on the mathematic relationship between electrostatic repulsion and the van der Waals attractive interaction at the CCC, the fluctuation coefficient ß was obtained. The value of β could quantify the strength of the specific ion effects of different cations. Then, the fluctuation coefficient β was introduced into the classical method for calculating the surface potential, considering the specific ion effects. The quantificational sequence of the ionic specificity of K+ and Na+ was as follows: βK = 1.433 > βNa = 1.187. Simultaneously, the surface potential considering specific ion effects can be obtained by introducing this coefficient. Our findings provide ideas for getting reliable surface potentials of charged particles in different electrolyte environments.

Polyelectrolyte multilayers (PEMs) are known for being susceptible to structural and mechanical changes in response to the ionic environment. Herein, the changes of the internal structure and surface morphology of (PDDA/PSS)4 films in an aqueous solution with various ionic conditions were investigated from the aspects of thickness, refractive index, and surface roughness. It was found that the strength of electrostatic shielding and ion doping effect arising from counterions changes with the NaCl concentration rising from 0.0 to 1.0 mol/L, resulting in a V-shaped change of film thickness and a flatter surface morphology. The effect of ion species on the film structure depends on the hydration size of the ions and their position in the Hofmeister series. Based on the refractive index and surface roughness of PEMs obtained by ellipsometry and AFM, the ion-specific effect on the Hamaker constant was also discussed. [ABSTRACT FROM AUTHOR]

Allotropes of two crystalline carbons, diamond and graphite, are sp³ and sp² hybridized, respectively. In between these two, there is an intermediate structure i.e., the mixture of sp³ and sp² nanocrystalline hydrogenated diamond-like carbon (HDLC) thin films. HDLC thin films were synthesized by the biased enhanced nucleation (BEN) technique in the reactive gas-plasma process (RGPP) under the varying ratio of H2 and CH4 flow rates. There are numerous applications of these materials depending on their sp²/sp³ ratio and surface properties. The property, hydrophilic/hydrophobic nature of the film surfaces can be measured from the water contact angle on the HDLC surfaces easily which also depends on the sp²/sp³ ratio. In this paper, we have evaluated the sp²/sp³ ratio indirectly through the water contact angle of the HDLC thin film and under its annealing treatment at low pressure. The sp²/sp3 ratio and C1s bonding type were estimated by the XPS spectrum. The study of the surface topography of the HDLC film was made by AFM and SEM. In this study, it can be concluded that the water contact angle on the HDLC surface does not significantly affect the surface morphology. A quantitative relationship is found between the sp²/sp³ ratio and the water contact angle of HDLC with hydrogen content, measured by the Angus and Jansen equation, and the Hamaker constant estimated by AFM using different models. [ABSTRACT FROM AUTHOR]

Investigation of the parameters affecting the agglomeration process of nanoparticles and its morphology is a challenging research problem. In recent years, various computer simulation methods are developed to study the effect of different parameters on the process of agglomeration. This paper investigates the behavior of dry TiO2 nanoparticles in a three-dimensional periodic box. Simulations are performed using Discrete Element Method where contact force is modeled following the concept of Hertzian spring. Integrated van der Waals force is considered for the cohesion between particles. Thermal fluctuations to the nanoparticles are also accounted in the simulation. Morphological properties like porosity, coordination number and fractal dimension are used to characterize the agglomerate. Further, the impact of cohesiveness on the packing of agglomerate is investigated. Fractal dimension and coordination number saturate with the increase in cohesiveness of the system. Fractal dimension ranges between 1.60 − 1.80 validating the diffusion limited agglomeration regime of TiO2 nanoparticles. Correlation between porosity and cohesiveness could not be established with the performed simulations. [ABSTRACT FROM AUTHOR]

We recently proposed a simple method for calculating the Hamaker constant based on the Hansen solubility parameters for non-polar liquids. In the present paper we show that this method, which utilizes a relationship between the surface tension and the Hamaker constant of liquids derived by Israelachvili, can be applied equally to non- or weakly hydrogen-bonding polar liquids. We further extend our theory to cover the case of strongly hydrogen-bonding polar liquids by employing an improved relationship between the surface tension and the Hamaker constant for hydrogen-bonding polar liquids derived by David and Neumann. Our method for calculating the Hamaker constant based on the Hansen solubility parameters is shown to be generally valid for both non-polar liquids and most polar liquids. [Display omitted] • Hamaker constant is related to Hansen solubility parameters for polar liquids. • Hamaker constant for polar liquids can be calculated based on this relation. • There are some exceptions including methanol and ethanol. [ABSTRACT FROM AUTHOR]

[Display omitted] Analytical expressions for calculating Hamaker constant (HC) and van der Waals (VDW) energy/force for interaction of a particle with a solid water interface has been reported for over eighty years. This work further developed novel analytical expressions and numerical approaches for determining HC and VDW interaction energy/force for the particle approaching and penetrating air–water interface (AWI), respectively. The expressions of HC and VDW interaction energy/force before penetrating were developed through analysis of the variation in free energy of the interaction system with bringing the particle from infinity to the vicinity of the AWI. The surface element integration (SEI) technique was modified to calculate VDW energy/force after penetrating. We explain why repulsive VDW energy exists inhibiting the particle from approaching the AWI. We found very significant VDW repulsion for a particle at a concave AWI after penetration, which can even exceed the capillary force and cause strong retention in water films on a solid surface and at air–water-solid interface line. The methods and findings of this work are critical to quantification and understanding of a variety of engineered processes such as particle manipulation (e.g., bubble flotation, Pickering emulsion, and particle laden interfaces). [ABSTRACT FROM AUTHOR]

The topographical features on the individual particles in a powder and the surfaces with which they interact affect the powder adhesion. An experimental and modelling framework called the Enhanced Centrifuge Method (ECM) maps particle and surface properties onto 'effective' Hamaker constant distributions that describe the van der Waals (vdW) adhesion between a powder and a surface. The ECM was used to study the adhesion between polystyrene powder and silica surfaces to exemplify the 'effective' Hamaker constants quantify the effects of particle and surface properties on adhesion. Silica surfaces were polished to alter their surface roughness profiles to reveal levels of roughness in which the adhesion was controlled by either the powder or surface properties. This study revealed surface roughness height descriptions are inadequate descriptors of adhesion, and instead the frequency of roughness peaks to the particle size must be considered. This result was verified using an existing particle adhesion simulator. [Display omitted] • The centrifuge method was used to measure polystyrene particle adhesion to silica. • Effective Hamaker constants quantify effect of particle and surface properties. • Particle adhesion was measured against varying degrees of surface roughness. • Particle adhesion does not correlate directly with RMS roughness. • The adhesion depends on the scale of the particle size to the surface topography. [ABSTRACT FROM AUTHOR]

The aggregation behavior of ubiquitous dissolved black carbon (DBC) largely affects the fate and transport of its own contaminants and the attached contaminants. However, the photoaging processes and resulting effects on its colloidal stability remain yet unknown. Herein, dissolved biochars (DBioCs) were extracted from common wheat straw biochar as a proxy for an anthropogenic DBC. The influences of UV radiation on their aggregation kinetics were systematically investigated under various water chemistries (pH, electrolytes, and protein). The environmental stability of the DBioCs before and after radiation was further verified in two natural water samples. Hamaker constants of pristine and photoaged DBioCs were derived according to Derjaguin-Landau-Verwey-Overbeek (DLVO) prediction, and its attenuation (3.19 ± 0.15 × 10 -21 J to 1.55 ± 0.07 × 10 -21 J after 7 days of radiation) was described with decay kinetic models. Pearson correlation analysis revealed that the surface properties and aggregation behaviors of DBioCs were significantly correlated with radiation time ( p < 0.05), indicating its profound effects. Based on characterization and experimental results, we proposed a three-stage mechanism (contended by photodecarboxylation, photo-oxidation, and mineral exposure) that DBioCs might experience under UV radiation. These findings would provide an important reference for potential phototransformation processes and relevant behavioral changes that DBC may encounter.

As a fluid approaches three phase coexistence, adsorption may take place by the successive formation of two intervening wetting films. The equilibrium thickness of these wetting layers is the result of a delicate balance of intermolecular forces, as dictated by an underlying interface potential. The van der Waals forces for the two variable adsorption layers may be formulated exactly from Dzyaloshinskii-Lifshitz-Pitaevskii theory, and analytical approximations may be derived that extent well beyond the validity of conventional Hamaker theory. We consider the adsorption equilibrium of water vapor on Silver Iodide where both ice and a water layers can form simultaneously and compete for the vapor as the triple point is approached. We perform numerical calculations of Lifshitz theory for this complex system and work out analytical approximations which provide quantitative agreement with the numerical results. At the three phase contact line between AgI/water/air, surface forces promote growth of ice both on the AgI/air and the water/vapor interfaces, lending support to a contact nucleation mode of AgI in the atmosphere. Our approach provides a framework for the description of adsorption at three phase coexistence, and allows for the study of ice nucleation efficiency on atmospheric aerosols. [ABSTRACT FROM AUTHOR]

Calcium silicate hydrate (C-S-H) is the main binding phase of Portland cement concrete. Though C-S-H is known to be assembled from nanoscale features, there is little experimental study on how C-S-H nano solids interact with each other at the interface, which may hold the key to explain its macroscale strength, creep, and shrinkage behaviour. This work attempts to experimentally quantify the interactions between C-S-H solid surfaces using atomic force microscopy (AFM). We took a new approach to measure the surface adhesion under different relative humidity (R.H.) and calculate the Hamaker constant using an algorithm that eliminates the influence of surface roughness. The effect of chemical composition (e.g. Ca/Si ratio) and RH on surface forces, e.g. the van der Waals and capillary force, were systematically explored and compared with molecular calculation results. Our work provides an insight into the nexus of C-S-H chemistry – adhesion force – bulk mechanical properties. [ABSTRACT FROM AUTHOR]

Under ambient conditions, surfaces are rapidly modified and contaminated by absorbance of molecules and a variety of nanoparticles that drastically change their chemical and physical properties. The atomic force microscope tip–sample system can be considered a model system for investigating a variety of nanoscale phenomena. In the present work we use atomic force microscopy to directly image nanoscale contamination on surfaces, and to characterize this contamination by using multidimensional spectroscopy techniques. By acquisition of spectroscopy data as a function of tip–sample voltage and tip–sample distance, we are able to determine the contact potential, the Hamaker constant and the effective thickness of the dielectric layer within the tip–sample system. All these properties depend strongly on the contamination within the tip–sample system. We propose to access the state of contamination of real surfaces under ambient conditions using advanced atomic force microscopy techniques.

Thin polymeric coatings are commonly used for altering surface properties and modulating the interfacial performance of materials. Possible contributions from the substrate to the interfacial forces and effects are, however, usually ignored and are not well understood, nor is it established how the coating thickness modulates and eventually eliminates contributions from substrates to the van der Waals (vdW) interfacial force. In this study we quantified, by colloid-probe atomic force microscope (AFM) and by theoretical calculations, the interfacial vdW contributions from substrates acting through ethanol plasma polymer (EtOHpp) coatings of a range of thicknesses on Au and Si bulk materials. In approach force curves against EtOHpp-coated Au substrates the magnitude of the vdW force decreased as the EtOHpp coating thickness increased to 18 nm and then plateaued with further increases in coating thickness, providing direct evidence for a contribution to the total interfacial vdW force from the Au substrate acting through thin coatings. The experimental observations accord with theoretical calculations of the thickness dependence of Hamaker coefficients derived from rigorous simulation using the Lifshitz theory. In addition, the measured forces agree well with theoretical predictions including correction for finite roughness. Thus, our experimental and theoretical results establish how the thickness of polymer thin film coatings modulates the total interfacial vdW force and how this can be used to tune the net vdW force so as to either contain a large substrate contribution or arise predominantly from the polymeric overlayer. Our findings enable rational design of coating thickness to tailor interfacial interactions and material performance. [ABSTRACT FROM AUTHOR]

The paper is a theoretical study of mechanically activated processes in tribocontact, which lead to the formation of a lubricating film between rubbing bodies. The adhesive aspect of tribofilm formation is considered using the condition of the mechanical activation of the friction surface. This condition is satisfied when the adhesion energy becomes greater than the cohesion energy. The Hamaker constant is used to describe not only the adhesive interaction during friction, but also the amount of matter transferred when the mechanical activation condition is met. It is shown that the adhesive effect decreases with the second power of the distance from the friction surface. A relationship is derived that relates tribological characteristics to the Hamaker constant as the fundamental characteristic of the material. It is shown how the friction coefficient in the steady-state regime depends on the counterbody material and the antifriction transfer film material. Numerical results are compared to experimental data. [ABSTRACT FROM AUTHOR]

Graphene is a honeycomb hexagonal two-dimensional (2D) crystal nanomaterial with a thickness of only 0.334 nm. It has been widely used and studied because of its ultra-thin 2D nano-characteristics and excellent electrical, thermal, optical, and mechanical properties. With the continuous in-depth study of graphene, the liquid-phase dispersion of graphene has also achieved breakthroughs. This review summarizes the research progress of the liquid-phase exfoliation mechanism, exfoliation method, stable dispersion mechanism, and dispersion method of graphene in recent years. The research situations of the Hamaker constant theory in exfoliation mechanism and Hansen solubility coefficient theory in stable dispersion mechanism are mainly discussed. The shortcomings of the research are summarized and analyzes the graphene liquid phase dispersed in the important challenge in the future. The stable dispersion method of graphene is also summarized. In the future, the π-π interaction will be the most potential method for studying graphene stabilization.

Dispersion quality has a large influence on the resulting properties of filled polymers, hybrids and nanocomposites in general. Reducing the van der Waals forces and therefore, matching the refractive index between the filler and the matrix should improve dispersion in hybrid materials. However, in this case the usual light-based techniques cannot be used to assess dispersion quality. In this work, dispersions containing silica nanoparticles and a solvent mixture of 1-butanol and benzyl alcohol were analysed by rheological methods. The refractive index of the solvent was changed by varying the mixing ratio, and thus the effect of index difference on the filler-matrix interaction was investigated. In agreement with theory, a stronger gel network was observed when the refractive index of filler and solvent were matched. If the difference in refractive index of the two materials became too large, particles and solvent interaction was reduced, and agglomerates were formed. This resulted in a weaker gel network.

The fast-growing production and application of carbon nanotube (CNT) materials in a variety of industrial products inevitably lead to their release to wastewater and surface water. CNT would experience oxidization in wastewater treatment plant due to the presence of large amount of disinfectants, such as H 2 O 2 and O 3 , which in turn affects the environmental fates and risks of CNT. In this study, oxidized CNT materials (O-CNTs) were prepared by treating CNT with H 2 O 2 /UV and O 3 (denoting as H 2 O 2 -CNT and O 3 -CNT, respectively). A variety of characterizations indicated that oxygen containing groups were generated on CNT surface upon the oxidation, and the O/C ratio increased in the order of pristine CNT < H 2 O 2 -CNT < O 3 -CNT. In the presence of Na+, K+ and Mg2+, the O-CNTs displayed better colloidal stability than the pristine CNT, and the stability increased with the oxidation degree (indicated by O/C ratio). This could be explained by the more negative surface charge and stronger hydrophilicity of the O-CNTs. Unexpectedly, in the presence of Ca2+, the most oxidized O 3 -CNT exhibited the poorest colloidal stability. The abundant carboxyl groups in O 3 -CNT provided effective binding sites for cation bridging effect through Ca2+ and led to stronger aggregation. Increasing pH was more favorable to disperse CNTs (both O-CNT and pristine CNT) in the presence of Na+, but much less effective in inhibiting the aggregation of O 3 -CNT in presence of Ca2+. This could be explained by the stronger cation bridging effect due to enhanced deprotonation the –COOH groups at higher pH conditions. The calculated Hamaker constants of the CNTs decreased with the oxidation degree, implying that there was lower van der Waals force between the O-CNTs. The Derjaguin–Landau–Verwey–Overbeek (DLVO) calculation confirmed that O-CNTs had to overcome higher energy barrier and thus showed better colloidal stability than the pristine CNT in the presence of Na+. Image 1 • Oxidation treatments introduced oxygen containing functional groups on CNTs. • The O/C ratio and oxidation degree increased in the order of pristine CNT < H 2 O 2 -CNT < O 3 -CNT. • O-CNTs displayed better colloidal stability than pristine CNT in solutions containing Na+, K+ or Mg2+. • Increased hydrophilcity and more negative surface charges promoted the colloidal stability of O-CNTs. • In presence of Ca2+, O 3 -CNT exhibited the poorest colloidal stability due to cation-bridging effect. Capsule : Colloidal stability of CNTs relays on the intricate interplay between their surface O-functional groups and solution chemistry factors. [ABSTRACT FROM AUTHOR]

Colloidal stability of core–shell nanoparticles consisted of silver core and chitosan/dextran sulfate multilayer shell in NaCl and CaCl2 solutions was investigated. The critical concentration of coagulation and the Hamaker constant were calculated depending on the number of bilayers in the shell on the nanoparticle surface. The colloidal stability of the core–shell nanoparticles significantly increases with the shell growth. [ABSTRACT FROM AUTHOR]

Interaction energy calculations that assume smooth and chemically homogeneous surfaces are commonly conducted to explain bacteria retention on solid surfaces, but experiments frequently exhibit signification deviations from these predictions. A potential explanation for these inconsistencies is the ubiquitous presence of nanoscale roughness (NR) and chemical heterogeneity (CH) arising from spatial variability in charge (CH1), Hamaker constant (CH2), and contact angles (CH3) on these surfaces. We present a method to determine the mean interaction energy between a colloid and a solid-water-interface (SWI) when both surfaces contained binary NR and CH. This approach accounts for double layer, van der Waals, Lewis acid-base, and Born interactions. We investigate the influence of NR and CH parameters and solution ionic strength (IS) on interaction energy profiles between hydrophilic and hydrophobic bacteria and the SWI. Increases in CH1 and CH3 reduce the energy barrier and create deeper primary minima on net electrostatically unfavorable surfaces, whereas increasing CH2 diminishes the contribution of the van der Waals interaction in comparison to quartz and makes a more repulsive surface. However, these roles of CH are always greatest on smooth surfaces with larger fractions of CH. In general, increasing CH1 and CH3 have a larger influence on bacteria retention under lower IS conditions, whereas the influence of increasing CH2 is more apparent under higher IS conditions. However, interaction energy profiles are mainly dominated by small fractions of NR, which dramatically lower the energy barrier height and the depths of both the secondary and primary minima. This significantly increases the relative importance of primary to secondary minima interactions on net electrostatically unfavorable surfaces, especially for conditions that produce small energy barriers on smooth surfaces. Energy balance calculations indicate that this primary minimum is sometimes susceptible to diffusive removal depending on the NR and CH parameters.