Effective Surface Coverage Research Articles

Amphiphilic polymeric particles based on gradient and block copoly(2-oxazoline)s: Interplay between structure and Pickering emulsion properties

Pickering emulsions (PEs) offer enhanced stability and reduced toxicity compared to conventional emulsions. Recent advances in polymer chemistry have introduced poly(2-alkyl/aryl-2-oxazoline)s (PAOx) as promising alternative emulsifying materials. Known for their biocompatibility, tunability, and stability, PAOx can be rapidly synthesized via microwave-assisted methods. This study explores the use of amphiphilic and non-water-soluble PAOx to stabilize PEs through the formation of polymeric particles (PPs) via nanoprecipitation. Preliminary screening identified HLB5.0 PAOx as effective in forming well-defined PPs. We then investigated the effects of chain length and monomer distribution on the properties of PPs and PEs. Unlike block-based particles, the use of gradient PAOx allowed modulation of the particles’ glass transition temperature while maintaining their size and wettability. In Pickering emulsion formulations, PPs demonstrated effective surface coverage at low concentrations (≈ 0.9 wt%), with DP100-based particles providing enhanced stability and tunable viscosities. The formation of high internal phase PEs further highlights the applicative potential of PAOx, offering broad application prospects in various industries, including biomedicine, pharmaceuticals, and cosmetics.

Heterogeneous Dynamics of Sheared Particle-Laden Fluid Interfaces with Janus Particle Doping.

The formation of particle clusters can substantially modify the dynamics and mechanical properties of suspensions in both two and three dimensions. While it has been well established that large network-spanning clusters increase the rigidity of particle systems, it is still unclear how the presence of localized nonpercolating clusters affects the dynamics and mechanical properties of particle suspensions. Here, we introduce self-assembled localized particle clusters at a fluid-fluid interface by mixing a fraction of Janus particles in a monolayer of homogeneous colloids. Each Janus particle binds to a few nearby homogeneous colloids, resulting in numerous small clusters uniformly distributed across the interface. Using a custom magnetic rod interfacial stress rheometer, we apply linear oscillatory shear to the particle-laden fluid interface. By analyzing the local affine deformation of particles from optical microscopy, we show that particles in localized clusters experience substantially lower shear-induced stretching than their neighbors outside clusters. We hypothesize that such heterogeneous dynamics induced by particle clusters increase the effective surface coverage of particles, which in turn enhances the shear moduli of the interface, as confirmed by direct interfacial rheological measurements. Our study illustrates the microscopic dynamics of small clusters in a shear flow and reveals their profound effects on the macroscopic rheology of particle-laden fluid interfaces. Our findings open an avenue for designing interfacial materials with improved mechanical properties via the control of formation of localized particle clusters.

Molecular Factors of Ice Growth Inhibition for Hyperactive and Globular Antifreeze Proteins: Insights from Molecular Dynamics Simulation.

The molecular mechanism behind the ice growth inhibition by antifreeze proteins (AFPs) is yet to be understood completely. Also, what physical parameters differentiate between the AFP and non-AFP are largely unknown. Thus, to get an atomistic overview of the differential antifreeze activities of different classes of AFPs, we have studied ice growth from different ice surfaces in the presence of a moderately active globular type III AFP and a hyperactive spruce budworm (sbw) AFP. Results are compared with the observations of ice growth simulations in the presence of topologically similar non-AFPs using all-atom molecular dynamics simulations. Simulation data suggest that the ice surface coverage is a critical factor in ice growth inhibition. Due to the presence of an ice binding surface (IBS), AFPs form a high affinity complex with ice, accompanied by a transition of hydration water around the IBS from clathrate-like to ice-like. Several residues around the periphery of the IBS anchor the AFP to the curved ice surface mediated by multiple strong hydrogen bonds, stabilizing the complex immensely. In the high surface coverage regime, the slow unbinding kinetics dominates over the ice growth kinetics and thus facilitates the ice growth inhibition. Due to the non-availability of a proper IBS, non-AFPs form a low-affinity complex with the growing ice surface. As a result, the non-AFPs are continuously repelled by the surface. If the concentration of AFPs is low, then the effective surface coverage is reduced significantly. In this low surface coverage regime, AFPs can also behave like impurities and are engulfed by the growing ice crystal.

Controlling Surface-Immobilized Elastin-like Peptides for Electrochemical Sensing Applications

Surface-immobilized elastin-like peptides (ELPs), known for their stimuli-responsive behavior, represent a promising biomolecular platform for electrochemical sensing. Key to the success of this applications is understanding how ELPs assemble on electrode surfaces, how the assembly and configuration can be controlled, and how their structure impacts the accessibility of the solid surface to redox active species. Here, we share recent work where short ELPs with varying guest residues and sequence length were designed for gold electrode attachment, and the ability of a redox probe to access a gold surface was characterized by cyclic voltammetry. From these results, a quantitative model describing the relationship between ELP effective surface coverage as a function of the mean hydrophobicity and mass loading was elucidated, illustrating the ability to precisely control surface properties by tuning the ELP sequence. In addition, strategies for controlling surface-bound ELP assembly and properties will be discussed. Ultimately, our work demonstrates that controlling the assembly and ELP configuration on the solid surface leads to more favorable electrochemical sensing capacity.

Probing surface-adsorbate interactions through active particle dynamics

Adsorbate molecules present in a reaction mixture may bind to and block catalytic sites. Measurement of the surface coverage of these molecules via adsorption isotherms is critical for modeling and design of catalytic reactions on surfaces. However, it is challenging to measure isotherms in solution in a way that is directly relevant to catalytic activity under reaction conditions, particularly since adsorbates may bind with an enormous range of surface affinity parameters. Here we used the motion of self-propelled catalytic Janus particles, which employ the decomposition of hydrogen peroxide fuel as a propulsion mechanism, to determine the effective surface coverage of thioglycerol, furfural, and ethanol on a platinum surface as a function of concentration in aqueous solution by measuring the decrease in active motion due to the blocking of active sites. For strongly adsorbing thioglycerol, this effective coverage was compared and contrasted to the total adsorbed amount measured using inductively-coupled plasma analysis. Demonstrating the broad applicability of this approach, the surface affinity of the three adsorbates spanned more than four orders of magnitude. For each species, the adsorbate-mediated attenuation of active motion occurred over a wide concentration range and was well-described by a Langmuir isotherm. The strongly interacting thioglycerol had the highest affinity towards the surface (Ka = 15.5 ± 4.3 mM−1) and fully deactivated the active particle motion at surface saturation. Furfural had an intermediate affinity (Ka = 0.42 ± 0.07 mM−1) but did not fully block H2O2 access to the surface at apparent saturation, consistent with a maximum fractional surface coverage of θmax = 0.67. Ethanol exhibited even lower affinity (Ka = 0.0025 ± 2x10-4 mM−1) and its coverage saturated at only θmax = 0.38. Analysis of isotherms at elevated temperatures enabled direct extraction of the enthalpies of adsorption. The degree of surface coverage at adsorbate saturation appeared to correlate with the relative energies of adsorption for the different adsorbate species and was consistent with adsorbate saturation of one of multiple active site populations towards H2O2 decomposition. Moreover, computational investigations into solvent effects on furfural adsorption showed good quantitative agreement with the experimental results. This work leverages unique properties of active particles to explore fundamental catalysis questions and demonstrates a novel paradigm for significant and experimentally accessible multidisciplinary research.

A Novel Coverage Improved Deployment Strategy for Wireless Sensor Network

Coverage of the bounded region gets importance in Wireless Sensor Network (WSN). Area coverage is based on effective surface coverage with a minimum number of sensor nodes. Most of the researchers contemplate the coverage region of interest as a square and manifest the radio ranges as a circle. The area of a circle is much higher than the area of a square because of the perimeter. To utilize the advantage of the circle, the coverage region of interest is presumed as a circle for sensor node deployment. This paper proposes a novel coverage improved disc shape deployment strategy. Comparative analysis has been observed between circle and square regions of interest based on the cumulative number of sensor nodes required to cover the entire region. A new strategy named as disc shape deployment strategy is also proposed. Traditional hexagon and strip-based deployment strategies are compared with the disc shape deployment strategy. The simulation result shows that the circle shape coverage region of interest extremely reduces the required number of sensor nodes. The proposed deployment strategy provides desirable coverage, and it requires few more sensor nodes than hexagon shape deployment strategy.

Electrochemical processes mediated via adsorbed Enzymes: Flat and porous electrodes Compared. Understanding Nano-confinement

• Adsorbed-enzyme-mediated electrochemical processes are investigated via simulations. • Potential dependent Michaelis constants are explained. • Four classes of voltammograms are introduced to help understand current responses. • Porous electrodes can create enhanced effective surface coverage and sensing ability. We present theory for electrolysis at electrode surfaces modified by a layer of electroactive enzyme which can mediate the reduction of a substrate to a product. In particular, we compare and contrast immobilisation on flat surfaces with that on porous surfaces. We identify the conditions under which the adoption of porous electrodes facilitates markedly improves turnover rates and develop the analysis on the basis of the porous layer conferring a much-increased effective surface coverage. For both types of electrode, the role of the electrode potential in controlling the thermodynamics of the binding of the substrate with the reduced layer of immobilised enzymes is quantified, and the observation of apparent potential dependent Michaelis constants are explained. Four distinct classes of voltammetric responses are categorised allowing bottom-up process optimisation.

Quantification of Effects of Hydrophobicity and Mass Loading on the Effective Coverage of Surface-Immobilized Elastin-like Peptides for Electrochemical Applications

Polypeptide engineering allows for a high degree of control at the molecular level, and thus has emerged as a promising tool for surface modification. Immobilized elastin-like peptides (ELPs), known for their stimuli-responsive behavior, have recently gained attention due to their potential applications in electrochemical sensing as well as bioenabled electrode assembly. Key to the success of these applications is understanding how ELPs impact the access and electron transfer of reacting species to the solid surface. In this study, short ELPs with varying guest residues and sequence length were designed for gold electrode attachment, and the influence on the ability of a redox probe to access a gold surface was characterized by cyclic voltammetry. Based on the results, a quantitative model describing the relationship between ELP effective surface coverage as a function of the mean hydrophobicity and mass loading was elucidated, illustrating the ability to precisely control surface properties by tuning the ELP sequence. This model can be used to design surface-bound ELP sequences design that exhibit desired effective surface coverage for electrochemical applications.

Quantification of the effects of hydrophobicity and mass loading on the effective coverage of surface-immobilized elastin-like peptides

Elastin-like peptides (ELPs) immobilized to solid surfaces have recently gained attention for use in electrochemical applications in sensing as well as bioenabled electrode assembly. Key to the success of these applications is understanding how ELPs impact the access and electron transfer of reacting species to the solid surface (effective surface coverage). In this study, short ELPs with varying hydrophobicity and sequence length were designed for gold attachment, and the effect on the ability of a redox probe to access a gold surface was characterized by cyclic voltammetry. A quantitative model describing the relationship between ELP effective surface coverage as a function of mean hydrophobicity and mass loading was elucidated based on the results, showing the ability to precisely control surface properties by tuning the ELP sequence. This model will be useful for the design of surface-bound ELP sequences that exhibit desired effective surface coverage for electrochemical as well as biomaterial applications.

Synthesis of a new class of corrosion inhibitors derived from natural fatty acid: 13‐Docosenoic acid amide derivatives for oil and gas industry

As corrosion inhibitors, a series of new amide derivatives of 13‐docosenoic acid was synthesized in yields of above 90% by reacting 13-docosenoic acid with primary and secondary aliphatic and aromatic amines. The inhibition efficiencies (%IEs) of these compounds at various concentrations for the suppression of corrosion of mild steel in 1.00 M HCl exposed for 96 h (4 days) at temperatures in the range 298–333 K were measured via gravimetric corrosion measurements. At 100 ppm, all compounds yielded satisfactory corrosion %IE in 1.00 M HCl; compounds 2 and 7 exhibited remarkable %IE of 70.0 and 74.7%, respectively. The results of gravimetric measurements further revealed that compound 7 performed excellently at 60 °C, with %IE = 96.8 at 500 ppm. Quantum chemical density functional theory (DFT) calculations helped predict that compound 7 should have more aromatic character, enabling it to serve as a donor-center for the empty d-orbital of the metal atoms, leading to higher corrosion IE. The adsorption of the inhibitor molecules on the surface of mild steel followed the Langmuir adsorption model, and the free energy of adsorption (ΔGads) value indicated that the inhibitors are adsorbed through a combined physisorption and chemisorption mechanism to provide effective surface coverage.

Effect of the combined admixture of 4-methyl-norvalin and 2-Methoxy-4-formylphenol on the corrosion inhibition of low carbon steel in artificial seawater solution

The synergistic effect of 4-methyl-norvalin and 2-methoxy-4-formylphenol on the corrosion inhibition of low carbon steel in artificial seawater (3.5 wt.% NaCl solution) was studied with potentiodynamic polarization technique, open circuit potential measurement and optical microscopic analysis. Results obtained from the electrochemical test showed the organic derivatives performed effectively with optimal inhibition performance of 89%. Mixed type inhibition behavior was observed. Anodic corrosion potential shift occurred because of effective surface coverage of the inhibitor molecules. The adsorption mode was determined to occur through physisorption reaction from thermodynamic calculations in agreement with the Langmuir, Frumkin and Freundlich isotherms at correlation coefficients beyond 0.7. Corroded morphology of steel occurred without with inhibitor compared to the steel from solution at highest inhibitor concentration.

HIBISCUS LEAF MUCILAGE AS STABILISER FOR PHARMACEUTICAL DISPERSE SYSTEMS

Objective: Stable pharmaceutical disperse systems are defined as heterogeneous, biphasic systems as suspensions and emulsions, stabilized by third agent or stabilizer. The aim of the present investigation was to extract mucilage from the leaves of Hibiscus rosa-sinesnsis L. and explore its ability to function as stabiliser for adult (10%w/v) and paediatric (2.4%w/v) paracetamol (PCM) suspensions and 2% v/v sunflower oil emulsions.
 Methods: Isolated mucilage powder was subjected to phytochemical tests to identify the major phytochemical constituents, FTIR spectroscopy to establish compatibility with formulation ingredients, X-ray diffractometry to determine the crystalline nature and viscosity study by Ostwald viscometer and swelling behaviour in water to determine the swelling index.
 Results: Qualitative phytochemical screening of the mucilage (HM) revealed the presence of non-reducing sugars, gums and mucilage. HM possesses a highly amorphous structure with extremely low overall crystallinity. The mucilage belongs to the class of carbohydrate as it contains–OH groups with intermolecular hydrogen bonding, with 1→4 glycosidic bonds which accounts for its high hydration capacity. Swelling index and relative viscosity of 0.5% w/v mucilage in water was found to be 1050 and 4.84 respectively at 25 °C. Although adult PCM suspensions containing 4% w/v mucilage exhibited poor redispersibility, paediatric suspension containing 1 and 2% w/v mucilage showed gradual settling of particles with good re-dispersibility and flowability. Emulsion activity index (EAI) values of the three emulsions (0.5, 0.75 and 1%w/v HM) were found to be close to 2 g. m-1 ml-1suggesting concentration independent activity of HM as an emulsifier. Emulsion stability index (ESI) values at 72 h showed comparatively less stability with increasing concentration of mucilage probably due to polysaccharide chain overlapping at high concentration leading to less effective surface coverage per unit gum concentration.
 Conclusion: Therefore, hibiscus leaf mucilage has the capacity to stabilize a suspension or emulsion based on its capacity to adsorb onto solid or liquid interfaces.

The role of land surface versus drainage network characteristics in controlling water quality and quantity in a small urban watershed

AbstractThe processes that control run‐off quantity and quality in urban watersheds are complex and not well understood. Although impervious surface coverage has traditionally been used to examine altered hydrologic response in urban watersheds, several studies suggest that other elements of the urban landscape, particularly those associated with urban infrastructure and the drainage system, play an equally important role. The relative importance of impervious surfaces, stormwater ponds, expansion of the drainage network, and drainage network structures in controlling hydrologic response was examined in the subwatersheds of the Kromma Kill, an urban watershed located in Albany County, NY. In this study, geographic information systems was used to compute geospatial land surface and drainage network properties of 5 Kromma Kill subwatersheds. In these same subwatersheds, water quantity (rainfall and run‐off) and quality (macroinvertebrates, nitrate, total nitrogen, dissolved oxygen, total dissolved solids, and nonpurgable organic carbon) parameters were measured. Strong and significant correlations were identified between land surface and drainage network properties and field observations. Causal relationships were then tested using the Environmental Protection Agency's Stormwater Management Model. Field and model analyses suggest that whereas percent imperviousness is a dominant control on water quality, drainage density and slope are equally important. However, for water quantity, whereas imperviousness is positively correlated with increased run‐off volumes, drainage network properties and slope are the dominant controls on run‐off volumes. Results have important implications for stormwater management plans, especially those aimed at reducing the effective impervious surface coverage of urban watersheds. Reducing the percentage of effective imperviousness in a watershed is not a “one size fits all” solution and can help to meet some management objectives, such as reducing nitrogen concentrations and improving water quality, but may not serve as the most effective, and therefore economical, solution for every management objective including reducing run‐off volumes.

Systematic Approach to the Development of Microfabricated Biosensors: Relationship between Gold Surface Pretreatment and Thiolated Molecule Binding.

Despite the increasing popularity of microfabricated biosensors due to advances in technologic and surface functionalization strategies, their successful implementation is partially inhibited by the lack of consistency in their analytical characteristics. One of the main causes for the discrepancies is the absence of a systematic and comprehensive approach to surface functionalization. In this article microfabricated gold electrodes aimed at biosensor development have been systematically characterized in terms of surface pretreatment, thiolated molecule binding, and reproducibility by means of X-ray photoelectron scattering (XPS) and cyclic voltammetry (CV). It has been shown that after SU-8 photolithography gold surfaces were markedly contaminated, which decreased the effective surface area and surface coverage of a model molecule mercaptohexanol (MCH). Three surface pretreatment methods compatible with microfabricated devices were compared. The investigated methods were (i) cyclic voltammetry in dilute H2SO4, (ii) gentle basic piranha followed by linear sweep voltammetry in dilute KOH, and (iii) oxygen plasma treatment followed by incubation in ethanol. It was shown that all three methods significantly decreased the contamination and increased MCH surface coverage. Most importantly, it was also revealed that surface pretreatments may induce structural changes to the gold surfaces. Accordingly, these alterations influence the characteristics of MCH functionalization.

Fe-Porphyrin-Based Metal–Organic Framework Films as High-Surface Concentration, Heterogeneous Catalysts for Electrochemical Reduction of CO2

Realization of heterogeneous electrochemical CO2-to-fuel conversion via molecular catalysis under high-flux conditions requires the assembly of large quantities of reactant-accessible catalysts on conductive surfaces. As a proof of principle, we demonstrate that electrophoretic deposition of thin films of an appropriately chosen metal–organic framework (MOF) material is an effective method for immobilizing the needed quantity of catalyst. For electrocatalytic CO2 reduction, we used a material that contains functionalized Fe-porphyrins as catalytically competent, redox-conductive linkers. The approach yields a high effective surface coverage of electrochemically addressable catalytic sites (∼1015 sites/cm2). The chemical products of the reduction, obtained with ∼100% Faradaic efficiency, are mixtures of CO and H2. These results validate the strategy of using MOF chemistry to obtain porous, electrode-immobilized, networks of molecular catalysts having competency for energy-relevant electrochemical reactions.

Faradaic Impedance Spectroscopy for Detection of Small Molecules Binding using the Avidin-Biotin Model

The changes in the Faradaic impedance of gold/biomolecules system due to specific binding of small molecule to a significantly larger binding protein molecule were investigated. The biotin (244.31Da) - avidin (66000Da) couple was used as a model for small ligand - binding protein biorecognition. The study was carried out under open circuit potential in the presence of [Fe(CN)6]−3/−4 redox couple. An equivalent electrical circuit was proposed and used for the interpretation of the recorded impedance spectra.Adsorption of thiolated avidin increased the electron transfer resistance, Rct, by a factor of about 7.5 while subsequent addition of biotin within the concentration range of 4.1-40.9nM reduced the value of Rct by amount proportional to the biotin concentration. The addition of biotin did not affect, however, the equivalent double layer capacitance or other equivalent circuit parameters.A simple model based on effective surface coverage by the avidin molecules and the effect of the added biotin on electron transfer through the coated surface is proposed. A model for the minimum detection limit based on the random distribution of the binding protein and its dimensions is proposed.

Electrochemical study of multi-component additive behavior during copper electrodeposition with a microfluidic device and an electrochemical quartz crystal microbalance

The adsorption behavior of multi-component additives during Cu electrodeposition was investigated to examine the role of single species in the early period of Cu electrodeposition. First, the current density (i) transition curves were measured using a microfluidic device for rapid exchange from the base electrolyte to electrolytes with bis(3-sulfopropyl)-disulfide (SPS), Janus Green B (JGB), and polyethylene glycol (PEG) to determine the effective surface coverage ratio (θEFF) of the electrodes by PEG, which is the first result with the multi-component system using a microfluidic device. The desorption behavior of additives was also investigated, and the presence or absence of PEG was found to be a key factor in maintaining the additives’ effects. Finally, the increase in the weight on the electrode (Δm) by the additives was measured using a flow cell-type electrochemical quartz crystal microbalance (EQCM) to calculate θEFF by Δm, which revealed that the suppression of i was roughly dominated by the adsorbed PEG amount, even in a multi-component system.

Synthesis and Study of Corrosion Protection Efficiency of Silica Nanoparticles on Aluminium

Monodispersed silica nanoparticles (SNPs) were synthesized by cost effective aqueous-ethanolic route. The particle size was controlled by optimizing the synthetic conditions. The synthesized different size SNPs were used to study the corrosion protection efficiency on aluminium (Al) in alkaline medium by weight loss, Potentiodynamic polarization and surface morphology examination methods. It was found that SNPs with smaller particle sizes showed better protection efficiency compared to those of larger particles. The results were explained in terms of effective surface coverage by smaller sized SNPs.

Droplet nucleation on a well-defined hydrophilic-hydrophobic surface of 10 nm order resolution.

Water condensation on a hybrid hydrophilic-hydrophobic surface was investigated to reveal nucleation mechanisms at the microscale. Focused ion beam (FIB) irradiation was used to change the wettability of the hydrophobic surface with 10 nm order spatial resolution. Condensation experiments were conducted using environmental scanning electron microscopy; droplets, with a minimum diameter of 800 nm, lined up on the FIB-irradiated hydrophilic lines. The heterogeneous nucleation theory was extended to consider the water molecules attracted to the hydrophilic area, thereby enabling explanation of the nucleation mechanism under unsaturated conditions. Our results showed that the effective surface coverage of the water molecules on the hydrophilic region was 0.1-1.1 at 0.0 °C and 560 Pa and was dependent on the width of the FIB-irradiated hydrophilic lines and hydrophobic area. The droplet nucleation mechanism unveiled in this work would enable the design of new surfaces with enhanced dropwise condensation heat transfer.

Design of surfactant-substrate interactions for roll-to-roll assembly of carbon nanotubes for thin-film transistors.

Controlled assembly of single-walled carbon nanotube (SWCNT) networks with high density and deposition rate is critical for many practical applications, including large-area electronics. In this regard, surfactant chemistry plays a critical role as it facilitates the substrate-nanotube interactions. Despite its importance, detailed understanding of the subject up until now has been lacking, especially toward tuning the controllability of SWCNT assembly for thin-film transistors. Here, we explore SWCNT assembly with steroid- and alkyl-based surfactants. While steroid-based surfactants yield highly dense nanotube thin films, alkyl surfactants are found to prohibit nanotube assembly. The latter is attributed to the formation of packed alkyl layers of residual surfactants on the substrate surface, which subsequently repel surfactant encapsulated SWCNTs. In addition, temperature is found to enhance the nanotube deposition rate and density. Using this knowledge, we demonstrate highly dense and rapid assembly with an effective SWCNT surface coverage of ~99% as characterized by capacitance-voltage measurements. The scalability of the process is demonstrated through a roll-to-roll assembly of SWCNTs on plastic substrates for large-area thin-film transistors. The work presents an important process scheme for nanomanufacturing of SWCNT-based electronics.