Dynamic Surface Properties Research Articles

SiO2 aerogel modified aggregates: Preparation, heat resistance and improvement mechanism

Modification of natural aggregates using SiO2 aerogel solution can not only radically reduce the rutting disease of asphalt pavement, but also avoid the problems of poor heat-resistant performance, mechanical strength and durability of ordinary heat-resistant aggregates. The effects of SiO2 aerogel solution type, modification method and SiO2 aerogel solution dosage on the thermal resistance and adhesion properties of SiO2 aerogel-modified aggregates (SM-Agg) were explored by orthogonal tests. Based on scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and infrared thermography, the surface micromorphology, elemental composition and dynamic thermal resistance properties of natural aggregate and SM-Agg were analyzed, respectively. The results showed that Both SiO2 aerogel solution type and dosage significantly affect the evaluation indexes and the modification of natural aggregates by soaking method using ZN-S type SiO2 aerogel solution with 15 % of the aggregate mass could obtain SM-Agg with good heat resistance and adhesion properties. The surface of SM-Agg was covered with a “gel layer” containing uniform and densely distributed SiO2 aerogel particles. The temperature of the top surface of the 18.3-mm-thick SM-Agg specimen gradually changed from 2.2°C higher than that of the natural aggregate to about 1.8°C lower than that of the natural aggregate within 60 min of heating at 55°C. The “gel layer” containing SiO2 aerogel particles forms one or more layers of three-dimensional heat-blocking mesh on the aggregate surface, which dramatically reduces the heat transfer area, prolongs the heat transfer path within the specimen, and increases the heat-reflecting capacity of the aggregate surface.

Synthesis of vinyl functionalized polyurethane acrylate oligomers and their photopolymerization via thiol-ene click reaction

Functional polyvinylethylene glycols (PVEGs) with different central structures were synthesized by Pd/B synergistic catalysts and reacted with isophorone diisocyanate (IPDI) and 2-hydroxyethyl methacrylate(HEMA) to prepared pendent vinyl-functional polyurethane acrylates (VFPUAs). The photopolymerization of the obtained VFPUAs with pentaerythritol tetra(3-mercaptopropionate) (PETMP) in the presence of a photoinitiator proceeded smoothly via thiol-ene photo-click reaction to give a series of crosslinked materials by the variation of the chemical structure of VFPUAs and a ratio of thiols and enes. The curing behavior was studied by FT-IR and the properties of crosslinked materials were characterized by the test of gel content, swelling ratio and water absorption. The dynamic mechanical properties, mechanical properties, thermogravimetry and surface properties of the crosslinked materials were investigated and the performance of coating for the crosslinked film materials was also characterized. The crosslinked film materials can be further functionalized by post-crosslinking modification through thiol-ene photo-click reaction.

Photopolymerization of polyvinylethylene glycol oligomers by thiol‐ene click reaction

AbstractFunctional polyvinylethylene glycols (PVEGs) with pendent vinyl groups were synthesized by Pd/B synergistic catalysts and their structures were characterized by 1H NMR and FT‐IR. The photopolymerization of the obtained PVEGs with multifunctional thiols in the presence of a photoinitiator proceeded smoothly via thiol‐ene photo‐click reaction to give a series of crosslinked materials by the variation of the molecular weight of PVEGs and a ratio of thiols and enes. The curing behavior was studied by FT‐IR and the properties of crosslinked materials were characterized by the test of gel content, swelling ratio, and water absorption. The dynamic mechanical analysis, mechanical properties, thermogravimetry, and surface properties of the crosslinked materials were investigated and the performance of coating for the crosslinked film materials was also characterized. The crosslinked film materials can be further functionalized by post‐crosslinking modification through thiol‐ene photo‐click reaction.

Facile synthesis of phase-adjustable CsPbBr<sub>3</sub>-Cs<sub>4</sub>PbBr<sub>6</sub> composite nanocrystals and <i>in-situ</i> study of phase transformation process

All-inorganic cesium lead halide perovskites have shown great potential applications in optoelectronic field due to their fascinating optical properties. Although perovskite materials have achieved great success in various fields, their inherent ionic properties and high dynamic surface properties have led to their poor stability, hindering their applications. The preparation of CsPbBr<sub>3</sub>-Cs<sub>4</sub>PbBr<sub>6</sub> nanocrystals has proven to be an effective strategy to enhance their photoluminescence properties and stability. Herein, we report an easy synthesis of CsPbBr<sub>3</sub>-Cs<sub>4</sub>PbBr<sub>6</sub> nanocrystals with a diphase structure at room temperature by using Cs-OA, Pb-OA and TOABr as precursors in toluene. It is found that the phase transformation and the relative composition between CsPbBr<sub>3</sub> and Cs<sub>4</sub>PbBr<sub>6</sub> are dependent on the concentration of TOABr and the ratio of Cs/Pb. The <i>in-situ</i> PL experiments reveal that the formation of ~12 nm CsPbBr<sub>3</sub> nanocubes experiences the fast nucleation, the focusing growth of size-distribution in early growth stage and Ostwald ripening growth in the later stage at a TOABr concentration of 0.16 mmol. With the increase of concentration of TOABr or molar ratio of Cs/Pb > 1 (Cs/Pb < 1), [PbBr<sub>4</sub>]<sup>2–</sup> complex and [PbBr<sub>3</sub>]<sup>–</sup> complex can coexist and compete with each other in toluene, and the CsPbBr<sub>3</sub> nucleations dominate in the early stage, then CsPbBr<sub>3-</sub>Cs<sub>4</sub>PbBr<sub>6</sub> nanocomposites are gradually formed on CsPbBr<sub>3</sub> nucleations as photoluminescence centers due to the continuous generation of [PbBr<sub>4</sub>]<sup>2–</sup> complex between TOABr and Pb<sup>2+</sup>. The relative composition of Cs<sub>4</sub>PbBr<sub>6</sub> in CsPbBr<sub>3-</sub>Cs<sub>4</sub>PbBr<sub>6</sub> nanocomposites can be improved from 4% to 85% with the concentration of TOABr increasing or Cs/Pb < 1. The optimized CsPbBr<sub>3</sub>-Cs<sub>4</sub>PbBr<sub>6</sub> composite nanocrystals possess high PLQY and stability. Our work provides an understanding of the mechanism of phase transformation in cesium lead halide perovskite materials.

Dynamic Properties of Adsorption Layers of κ-Casein Fibrils.

The dynamic surface properties of native κ-casein solutions and aqueous dispersions of its fibrils differ significantly from the corresponding properties of the systems with globular proteins. The dependence of the dynamic surface elasticity of κ-casein solutions on surface pressure has a local maximum, indicating partial displacement of macromolecules from the proximal region of the surface layer to the distal one. This dependence becomes monotonic for fibril dispersions, similar to the results for dispersions of globular protein fibrils, but unlike the latter case, the surface elasticity close to the steady state reaches values that are approximately four times higher than the data for native protein solutions at the same concentrations.

The effects of surfactants on plunging breakers

The effects of surfactants on a mechanically generated plunging breaker are studied experimentally in a laboratory wave tank. Waves are generated using a dispersively focused wave packet with a characteristic wavelength of $\lambda _0 = 1.18$ m. Experiments are performed with two sets of surfactant solutions. In the first set, increasing amounts of the soluble surfactant Triton X-100 are mixed into the tank water, while in the second set filtered tap water is left undisturbed in the tank for wait times ranging from 15 min to 21 h. Increasing Triton X-100 concentrations and longer wait times lead to surfactant-induced changes in the dynamic properties of the free surface in the tank. It is found that low surface concentrations of surfactants can dramatically change the wave breaking process by changing the shape of the jet and breaking up the entrained air cavity at the time of jet impact. Direct numerical simulations (DNS) of plunging breakers with constant surface tension are used to show that there is significant compression of the free surface near the plunging jet tip and dilatation elsewhere. To explore the effect of this compression/dilatation, the surface tension isotherm is measured in all experimental cases. The effects of surfactants on the plunging jet are shown to be primarily controlled by the surface tension gradient ( $\Delta \mathcal {E}$ ) while the ambient surface tension of the undisturbed wave tank ( $\sigma _0$ ) plays a secondary role.

Dynamic Surface Properties of α-Lactalbumin Fibril Dispersions.

The dynamic surface properties of aqueous dispersions of α-lactalbumin (ALA) amyloid fibrils differ noticeably from the properties of the fibril dispersions of other globular proteins. As a result, the protocol of the application of ALA fibrils to form stable foams and emulsions has to be deviate from that of other protein fibrils. Unlike the fibrils of β-lactoglobulin and lysozyme, ALA fibrils can be easily purified from hydrolyzed peptides and native protein molecules. The application of the oscillating barrier method shows that the dynamic surface elasticity of ALA fibril dispersions exceeds the surface elasticity of native protein solutions at pH 2. ALA fibrils proved to be stable at this pH, but the stability breaks at higher pH levels when the fibrils start to release small peptides of high surface activity. As a result, the dynamic surface properties of ALA coincide with those of native protein solutions. The ionic strength strongly influences the adsorption kinetics of both fibril dispersions and native protein solutions but have almost no impact on the structure of the adsorption layers.

Ligation of Gold Nanoparticles with Self-Assembling, Coiled-Coil Peptides.

The surface of gold nanoparticles (AuNPs) can be conjugated with a wide range of highly functional biomolecules. A common pitfall when utilizing AuNPs is their tendency to aggregate, especially when their surface is functionalized with ligands of low molecular weight (no steric repulsion) or ligands of neutral charge (no electrostatic repulsion). For biomedical applications, AuNPs that are colloidally stable are desirable because they have a high surface area and thus reactivity, resist sedimentation, and exhibit uniform optical properties. Here, we engineer the surface of AuNPs so that they remain stable when decorated with coiled-coil (CC) peptides while preserving the native polypeptide properties. We achieve this by using a neutral, mixed ligand layer composed of lipoic acid poly(ethylene glycol) and lipoic acid poly(ethylene glycol) maleimide to attach the CCs. Tuning the surface fraction of each component within the mixed ligand layer also allowed us to control the degree of AuNP labeling with CCs. We demonstrate the dynamic surface properties of these CC-AuNPs by performing a place-exchange reaction and their utility by designing an energy-transfer-based caspase-3 sensor. Overall, this study optimizes the surface chemistry of AuNPs to quantitatively present functional biomolecules while maintaining colloid stability.

Dynamic Surface Properties of Fibrin

Dynamic Surface Properties of Fibrin

Can I Squeeze Through? Effects of Self-Avatars and Calibration in a Person-Plus-Virtual-Object System on Perceived Lateral Passability in VR.

With the popularity of Virtual Reality (VR) on the rise, creators from a variety of fields are building increasingly complex experiences that allow users to express themselves more naturally. Self-avatars and object interaction in virtual worlds are at the heart of these experiences. However, these give rise to several perception based challenges that have been the focus of research in recent years. One area that garners most interest is understanding the effects of self-avatars and object interaction on action capabilities or affordances in VR. Affordances have been shown to be influenced by the anthropometric and anthropomorphic properties of the self-avatar embodied. However, self-avatars cannot fully represent real world interaction and fail to provide information about the dynamic properties of surfaces in the environment. For example, pressing against a board to feel its rigidity. This lack of accurate dynamic information can be further amplified when interacting with virtual handheld objects as the weight and inertial feedback associated with them is often mismatched. To investigate this phenomenon, we looked at how the absence of dynamic surface properties affect lateral passability judgments when carrying virtual handheld objects in the presence or absence of gender matched body-scaled self-avatars. Results suggest that participants can calibrate to the missing dynamic information in the presence of self-avatars to make lateral passability judgments, but rely on their internal body schema of a compressed physical body depth in the absence of self-avatars.

Equilibrium and dynamic surface properties of cationic/anionic surfactant mixtures based on alcohol ether sulfate

The equilibrium and dynamic surface properties of anionic surfactant alcohol ether sulfate with different EO distribution(C-AE2S and N-AE2S) and cationic surfactant tetradecyltrimethylammonium bromide (TTAB) mixtures under different molar ratios were investigated. Their surface activities, adsorption, and spreading performances were investigated by static/dynamic surface tension measurements, molecular dynamics simulation, and dynamic contact angle techniques at 298 K. The static surface tension analysis reveals that the critical micellization concentration (cmc) values and the surface tension at cmc (γ cmc) of the binary systems are much lower than that of the individual component. Compared with C-AE2S/TTAB, N-AE2S/TTAB systems have higher cmc and lower γ cmc. It was found from the molecular dynamics simulation that negative charges of C-AE2S were drastically neutralized by the positively-charged TTAB at the interface in the system of C-AE2S/TTAB. The dynamic surface tension results indicate that the adsorption process of aqueous solutions for both C-AE2S/TTAB and N-AE2S/TTAB are mixed diffusion-kinetic adsorption mechanisms. From the dynamic contact angle measurements, it could be obtained that the mixtures exhibit better spreading behavior than that of the individual component and N-AE2S/TTAB systems have lower contact angles than that of C-AE2S/TTAB at the same mixing ratios.

Photoexcitation-Induced Assembly: A Bottom-Up Physical Strategy for Driving Molecular Motion and Phase Evolution

ConspectusIn the field of molecular assembly, photodriven self-assembly is a smart and crucial strategy to regulate the molecular orderliness, multiscale structure, and optoelectronic properties. Traditionally, photodriven self-assembly is based on photochemical processes, through molecular structural change induced by photoreactions. Despite great progress in the photochemical self-assembly, there still exists disadvantages (e.g., the photoconversion rate never reaches 100% with the possible side reactions). Therefore, the photoinduced nanostructure and morphology are often difficult to predict due to insufficient phase transition or defects. In contrast, the physical processes based on photoexcitation are straightforward and can fully utilize photons to avoid the drawbacks of photochemistry. The photoexcitation strategy excludes the change of molecular structure, only utilizing the molecular conformational change from the ground state to excited state. Then, the excited state conformation is employed to drive molecular movement and aggregation, further promoting the synergistic assembly or phase transition of the entire material system. The regulation and exploration of molecular assembly upon photoexcitation can open up a new paradigm to deal with the "bottom-up" behavior and develop unprecedented optoelectronic functional materials.This Account starts with a brief introduction to the problems faced by photocontrolled self-assembly and presents the photoexcitation-induced assembly (PEIA) strategy. Then, we focus on exploring PEIA strategy based on persulfurated arenes as the prototype. The molecular conformational transition of persulfurated arenes from the ground state to the excited state is conducive to the formation of intermolecular interactions, successively driving molecular motion, aggregation, and assembly. Next, we describe our progress in exploring PEIA of persulfurated arenes at the molecular level and then demonstrate that the PEIA of persulfurated arenes can synergistically drive molecular motion and phase transition in various block copolymer systems. Moreover, we provide the potential applications of PEIA in dynamic visual imaging, information encryption, and surface property regulation. Finally, an outlook on further development of PEIA is prospected.

Dynamic interfacial properties and foam behavior of licorice root extract solutions

Licorice (Glycyrrhiza glabra) is a useful plant of the family Fabaceae, with sweet-tasting roots. The root extract of this plant is rich in saponins, so it can be considered a source of natural surfactants. This research provides some applicable information about the dynamic surface tension and foam behavior of aqueous solutions of licorice root extract (LRE). The pendant drop shape analysis was utilized to study the surface tension and dilational surface rheology of LRE at the water/air interface. The Bikerman type experiment was used to measure foamability and foam stability of aqueous LRE solutions. The equilibrium surface tensions reveal that the LRE contains surface-active components and is capable of reducing the surface tension by 25 mN/m at the critical aggregation concentration (CAC). The surface dilational visco-elasticity measurements proved that the adsorption layers are predominantly of elastic nature. Also the foamability and foam stability show a meaningful correlation with the dynamic surface properties. This study aims to contribute to the development of appropriate utilization of the benefits provided by a biosurfactant source in foam-related commercial applications.

Interaction of catalyst nanoparticles and pollutant molecules in photocatalytic wastewater treatment: Novel characterization via dynamic surface properties

In photocatalytic processes for wastewater treatment, the degradation reactions mainly occurs at the surface of the catalyst and nearby regions. Therefore, understanding of the interactions between the catalyst and pollutant in a photocatalytic degradation system is of utmost importance, determining the affinity of the pollutant molecules to be attracted or repulsed from the photocatalyst particles. The aim of this experimental study is to get a better insight about the interactions between the catalyst nanoparticles and pollutant molecules via a novel characterization method based on dynamic surface phenomena analysis. Drop profile analysis tensiometry (PAT) is used for this purpose for dynamic surface tension and elasticity measurements of dye solutions (as pollutants), and in mixed solutions with catalyst particles at different pH conditions. The results demonstrate that the cationic dye Malachit Green (MG) has a low surface activity at pH 6.5, with an equilibrium surface tension about 69 mN/m. While it becomes much more surface active at pH 9 and surface tension is decreased to 59 mN/m. Adding TiO2 nanoparticles to MG solution at pH 9 causes a significant increase in surface tension, with much slower dynamics of adsorption at air/water interface. These results indicate a significant attraction and attachment of MG molecules to the surface of TiO2 nanoparticles, creating MG-TiO2 complexes, which have mobility much slower than the free MG molecules. This observation is in a good correlation with observed higher efficiency of MG degradation around pH 9. The capability of this novel experimental protocol is also examined for the anionic dye Eriochrom Black-T (EBT). According to the results, a significant interaction between TiO2 nanoparticles and EBT exist at pH 3, which is also well in accordance with reported higher efficiency of EBT degradation around pH 3. The elasticity measurements performed in this work, also support these results as an important characterization parameter for estimation of the molecular interactions in mixed adsorbed layers.

Dynamic surface properties of carboxyfullerene solutions

Application of conventional methods of dilatational surface rheology in combination with optical techniques and atomic force microscopy allowed determination of the surface properties of a water-soluble fullerene derivative, carboxyfullerene C60(C(COOH)2)3. It has been shown that the surface activity of this derivative is higher than that of other soluble fullerene derivatives, for example, of fullerenols. The dynamic surface elasticity of carboxyfullerene solutions reaches up to values of about 180 mN/m. Brewster angle microscopy indicates a liquid-like nature of carboxyfullerene adsorption layers. The application of atomic force microscopy shows that these adsorption layers consist of numerous interconnected surface aggregates. The size and number of aggregates increase during adsorption. The compression of carboxyfullerene spread layers results in its partial dissolution. At the same time, the compression isotherms indicate a high stability of the layers of carboxyfullerene aggregates.

Periodic structural changes in Pd nanoparticles during oscillatory CO oxidation reaction

Nanoparticle (NP) catalysts are ubiquitous in energy systems, chemical production, and reducing the environmental impact of many industrial processes. Under reactive environments, the availability of catalytically active sites on the NP surface is determined by its dynamic structure. However, atomic-scale insights into how a NP surface reconstructs under reaction conditions and the impact of the reconstruction on catalytic activity are still lacking. Using operando transmission electron microscopy, we show that Pd NPs exhibit periodic round–to–flat transitions altering their facets during CO oxidation reaction at atmospheric pressure and elevated temperatures. This restructuring causes spontaneous oscillations in the conversion of CO to CO2 under constant reaction conditions. Our study reveals that the oscillatory behavior stems from the CO-adsorption-mediated periodic restructuring of the nanocatalysts between high-index-faceted round and low-index-faceted flat shapes. These atomic-scale insights into the dynamic surface properties of NPs under reactive conditions play an important role in the design of high-performance catalysts.

Correlation of the renormalized Hilbert length for convex projective surfaces

AbstractIn this paper, we focus on dynamical properties of (real) convex projective surfaces. Our main theorem provides an asymptotic formula for the number of free homotopy classes with roughly the same renormalized Hilbert length for two distinct convex real projective structures. The correlation number in this asymptotic formula is characterized in terms of their Manhattan curve. We show that the correlation number is not uniformly bounded away from zero on the space of pairs of hyperbolic surfaces, answering a question of Schwartz and Sharp. In contrast, we provide examples of diverging sequences, defined via cubic rays, along which the correlation number stays larger than a uniform strictly positive constant. In the last section, we extend the correlation theorem to Hitchin representations.

Effect of Low Concentrations of Thrombin on the Dynamic Surface Properties of Fibrinogen Solutions

Effect of Low Concentrations of Thrombin on the Dynamic Surface Properties of Fibrinogen Solutions

Formation and phase behavior of porphyrin/arachidic acid mixed systems and morphology study of Langmuir-Schaefer thin films

ABSTRACT The paper is focused on the study of the dynamic surface properties of mixed monolayers of porphyrin and arachidic acid with various mole fractions at the air–water interface. The choice of porphyrin solid thin film as an object of study is explained by its high potential application in the area of photovoltaics and medicine. The Langmuir monolayers of porphyrin and arachidic acid were formed under different conditions using the Langmuir-Blodgett technique. The increase of subphase temperature led to a decrease in the rigidity of the porphyrin monolayer and leads to accelerating the relaxation process of the monolayer. The chosen surface pressure (4, 5, 15 and 35 mN/m) affected the stability of the floating monolayer. The higher miscibility of the monolayers was obtained at the mole fraction of porphyrin = 0.333. The change in the phase of monolayers surface was reported on the basis of surface potential data. The morphology properties of the mixed systems transferred on silicon substrates by Schaeffer method are studied.

Thermal nature of a generic null surface

Dynamical properties of a generic null surface are known to have a thermodynamic interpretation. Such an interpretation is completely based on an analogy between the usual law of thermodynamics and structure of gravitational field equation on the surface. Here we materialize this analogy and show that assigning a temperature on the null surface for a local observer is indeed physically relevant. We find that for a local frame, chosen as outgoing massless chargeless particle (or field mode), perceives a ``local unstable Hamiltonian'' very near to the surface. Due to this it has finite quantum probability to escape through acausal null path which is given by Maxwell-Boltzmann like distribution, thereby providing a temperature on the surface.