Importance Of Surface Structure Research Articles

Wettability Property In Natural Systems: A Case of Flying Insects

AbstractRecently, scientists have demonstrated that material surfaces in nature that possess special wettability properties are composed of micro- and nanostructures. In this study, we focused on the importance of surface structures in determining the wettability of wings of the flying insect species: Idea malabarica, Lucilia sericata and Chrysomya marginalis. Scanning Electron Microscopy (SEM) analysis indicates the different nano-/micro- structures identified on the wings. Surface roughness which plays a role in influencing the wettability was theoretically estimated from the SEM images. While the spherical liquid water droplets used for testing wettability were observed to float on the surface of the Idea malabarica and Lucilia sericata wings, the surface of the Chrysomya marginalis wing was made completely wet. The super-hydrophobicity of the Idea malabarica wing as compared to the near-hydrophobicity/mild hydrophilicity of the Lucilia sericata wing and the distinct hydrophilicity of the Chrysomya marginilis wing could be attributed to its complicated composition of nano-/microstructures and higher surface roughness value.

Impact of protecting ligands on surface structure and antibacterial activity of silver nanoparticles.

Silver nanoparticles (Ag NPs) have attracted much attention in the past decade because of their unique physicochemical properties and notable antibacterial activities. In particular, thiol-protected Ag NPs have come to the forefront of metal nanoparticle studies, as they have been shown to possess high stability and interesting structure-property relationships. However, a clear correlation between thiol-protecting ligands, the resulting Ag NP surface structure, and their antibacterial properties has yet to be determined. Here, a multielement (Ag and S), multi-edge (Ag K-edge, Ag L3-edge, S K-edge) X-ray absorption spectroscopy (XAS) methodology was used to identify the structure and composition of Ag NPs protected with cysteine. XAS characterization was carried out on similar-sized Ag NPs protected with poly(vinylpyrrolidone) (PVP), in order to provide a valid comparison of the ligand effect on surface structure. The PVP-Ag NPs showed a metallic Ag surface and composition, consistent with metal NPs protected by weak protecting ligands. On the other hand, the Cys-Ag NPs exhibited a distinct surface shell of silver sulfide, which is remarkably different than previously studied Cys-Ag NPs. The minimum inhibitory concentration (MIC) of both types of Ag NPs against Gram-positive (+) and Gram-negative (-) bacteria were tested, including Staphylococcus aureus (+), Escherichia coli (-), and Pseudomonas aeruginosa (-). It was found that the MICs of the Cys-Ag NPs were significantly lower than the PVP-Ag NPs for each bacteria, implicating the influence of the sulfidized surface structure. Overall, this work shows the effect of ligand on the surface structure of Ag NPs, as well as the importance of surface structure in controlling antibacterial activity.

Importance of surface structure on dissolution of fluorite: Implications for surface dynamics and dissolution rates

Dissolution rates are usually calculated as a function of surface area, which is assumed to remain constant ignoring the changes occurring on the surface during dissolution. Here we present a study of how topography of natural fluorite surfaces with different orientation changes during up to 3200h of dissolution. Results are analyzed in terms of changes in surface area, surface reactivity and dissolution rates.All surfaces studied present fast changes in topography during the initial 200h of dissolution. The controlling factors that cause the development of topography are the stability of the step edges forming the initial surface and its inclination to the closest stable planes, which are specific for each surface orientation. During an initial dissolution regime dissolution rates decrease significantly, even though the total surface area increases. During a second dissolution regime, some surfaces continue to present significant changes in topography, while for others the topography tends to remain approximately constant. The observed variation of dissolution rates are attributed to a decrease of the density of step edges on the surface and the continuous increase in exposure of more stable surfaces. Calculations of dissolution rates, which assume that dissolution rates are directly proportional to surface area, are not valid for the type of surfaces studied. Instead, to develop accurate kinetic dissolution models and more realistic stochastic dissolution simulations the surface reactivity, determined by the relative stability of the planes and type of edges that constitute a surface needs to be considered. Significant differences between dissolution rates calculated based on surface area alone, and based on surface reactivity are expected for materials with the fluorite structure.

Effect of surface structure on the charge storage capacity of carbon black electrodes

In this work we study the effect of surface structure on the charge storage capacity of carbon black electrodes with various changes in surface chemistry, morphology, and doping species. Cyclic voltammetry and chronopotentiometry studies, performed under alkaline conditions with carbon paste electrodes, indicate the importance of surface structure and grain size on the faradic and capacitive charge contributions of these materials. Among the various carbon blacks studied, the lithiated material shows superior charge storage capacity, suggesting the importance of alkaline metals and oxygenated groups on the carbon surface. For the graphitic carbon, the appearance of a reversible redox process with cycling resembles the electrochemical behavior reported for hydrogen storage in carbon nanotubes.

Comments on the paper of A.T. D'Agostino and P.N. Ross: “on the importance of surface structure in electrochemistry: the well-defined Au (111) single crystal electrode surface”

Comments on the paper of A.T. D'Agostino and P.N. Ross: “on the importance of surface structure in electrochemistry: the well-defined Au (111) single crystal electrode surface”

On the importance of surface structure in electrochemistry: the well-defined Au (111) single crystal electrode surface

Donnees sur l'etude par diffraction d'electrons lents de la structure UHV (d'ultravide) de cristaux d'or (111), sur les caracteristiques voltammetriques de cette surface et sur la stabilite de la structure UHV au cyclage anodique. Considerations sur les difficultes d'obtention d'une structure superficielle bien definie sur les cristaux d'Au (111)