Related Surface Properties Research Articles

Human neutrophil elastase detection with fluorescent peptide sensors conjugated to cellulosic and nanocellulosic materials: part II, structure/function analysis

Human neutrophil elastase (HNE) is one of a number of proteases that is receiving increased attention as a marker for inflammatory diseases and sensor-based point of care diagnostics. Integral to sensor-based detection is the transducer surface, which is the platform of the sensor’s signal transmittance. Here we describe the bioactivity and related transducer surface properties of cellulose and nanocellulose matrices as peptide–cellulose fluorescent sensors. Detection sensitivity of the sensor signals for HNE levels typically found in chronic wounds is characterized. The fluorescent elastase peptide substrate, Succinamidyl-Ala-Ala-Pro-Val-amidylcoumadin (Pep) was employed in both cellulose and nanocellulose transducer surfaces evaluated for biosensor sensitivity to HNE. The cellulose transducers selected are filter paper (FP) and print cloth (PC) fabric and are comprised of processed cotton fibers. The nanocellulose transducers are the wood cellulose nanocrystals (wCNC) and the wood nanocellulose composites (wNCC). The wNCCs consist of blended quantities of nanocrystalline and microfibrillated cellulose at 66/33 and 50/50, and are characterized as thin films. The biosensor activity was in the order of wCNC-Pep > FP-Pep = NCC-Pep (50/50) > NCC-Pep (66/33) > PC-Pep. Sensor sensitivity correlated with specific surface area. A depiction of peptide substitution on nanocellulosic and cellulosic surfaces is rendered through peptide–cellulose crystallite models derived from X-ray diffraction analysis of the material, and the models discussed in light of biosensor structure activity relationships. In addition, the overall morphology, pore size and porosity of the materials are discussed for their suitability as protease sensors.

Exothermic effects and related surface properties of the ex situ presulfurized catalysts in fabrication and activation

An ex-situ presulfurization technology for transforming the metal oxides of hydrotreating catalyst to the corresponding metal oxy-sulfides was developed, involving pre-dispersion of an organo-nitrogen substance onto catalyst and a subsequent multi-step heat treatment. The inherence of exothermic effect involved in the ex situ pre-sulfurized catalyst fabrication and activation, and particularly the relationship between the exothermic effect and the surface property of catalyst were investigated. The results indicated that both the preparation parameters and the operating conditions can have effects on the exothermic behavior and surface state of the catalyst. The information obtained in the current study is useful for optimizing the EPRES process, essential for hydrotreating catalyst and its application.

Highly porous organic polymers bearing tertiary amine group and their exceptionally high CO2 uptake capacities

We report a very simple and unique strategy for synthesis of a tertiary amine functionalized high surface area porous organic polymer (POP) PDVTA-1 through the co-polymerization of monomers divinylbenzene (DVB) and triallylamine (TAA) under solvothermal reaction conditions. Two different PDVTA-1 samples have been synthesized by varying the molar ratio of the monomers. The porous polymeric materials have been thoroughly characterized by solid state 13C CP MAS-NMR, FT-IR and UV–vis spectroscopy, N2 sorption, HR TEM and FE SEM to understand its chemical environment, nanostructure, bonding, morphology and related surface properties. PDVTA-1 with higher amine content (DVB/TAA=4.0) showed exceptionally high CO2 uptake capacity of 85.8wt% (19.5mmolg−1) at 273K and 43.69wt% (9.93mmolg−1) at 298K under 3bar pressure, whereas relatively low amine loaded material (DVB/TAA=7.0) shows uptake capacity of 59.2wt% (13.45mmolg−1) at 273K and 34.36wt% (7.81mmolg−1) at 298K. Highly porous nanostructure together with very high surface area and basicity at the surface due to the presence of abundant basic tertiary amine N-sites in the framework of PDVTA-1 could be responsible for very high CO2 adsorption.

Organo-modified ZnO nanoparticles: tuning of the optical properties for PLED device fabrication

Organo-modified ZnO nanoparticles were synthesized in basic media through a co-precipitation method, starting from a solution of zinc acetate in methanol and three different organosilane species (i.e. 3-aminopropyl-triethoxy silane, isobutyl-triethoxy silane and phenyl-triethoxy silane). Following this one-pot procedure, highly luminescent nanoparticles with organic species covalently bound on the ZnO surface were successfully obtained. The samples were studied through a multidisciplinary approach aiming to define their structural, morphological and surface properties in relation to the different organosilanes used for the ZnO preparation. Furthermore, a comparison of the optical features of the produced materials was also attained. Among the different ZnO nanoparticles, those functionalized with isobutyl groups were added to a light-emitting poly(p-phenylene vinylene) derivative copolymer (Super Yellow of the Merck Company) in order to obtain a novel composite material with enhanced emission properties. The latter was used as an active layer in the fabrication of a highly efficient Polymeric Light Emitting Diode (PLED) device.

Surface Properties and Chemical Composition of Corncob and Miscanthus Biochars: Effects of Production Temperature and Method

Biochar properties vary, and characterization of biochars is necessary for assessing their potential to sequester carbon and improve soil functions. This study aimed at assessing key surface properties of agronomic relevance for products from slow pyrolysis at 250-800 °C, hydrothermal carbonization (HTC), and flash carbonization. The study further aimed at relating surface properties to current characterization indicators. The results suggest that biochar chemical composition can be inferred from volatile matter (VM) and is consistent for corncob and miscanthus feedstocks and for the three tested production methods. High surface area was reached within a narrow temperature range around 600 °C, whereas cation exchange capacity (CEC) peaked at lower temperatures. CEC and pH values of HTC chars differed from those of slow pyrolysis biochars. Neither CEC nor surface area correlated well with VM or atomic ratios. These results suggest that VM and atomic ratios H/C and O/C are good indicators of the degree of carbonization but poor predictors of the agronomic properties of biochar.

Characterization of Graphite Coatings Produced by CoBlast™ Technology

In this article, the surface characterization of graphite-based coatings deposited on metallic substrates at ambient temperature via a modified micro-blasting process technique named CoBlast™ is reported. The coated metals were characterized using scanning electron microscopy, energy-dispersive x-ray spectroscopy, x-ray diffractometer, and x-ray photoelectron spectroscopy. Surface roughness and contact angles were also evaluated. The results showed that the coated layer irrespective of the substrate type was hydrophobic and consisted of graphite, the grit material, and surface oxides, while surface roughness values varied from one substrate to the other. Implications of the resulting surface properties in relation to wear and corrosion applications are highlighted.

Effects of Solution Chemistry on Bacterial Adhesion with Phyllosilicates and Goethite Explained by the Extended DLVO Theory

Adhesion of Bacillus subtilis on kaolinite, montmorillonite, and goethite was investigated over a wide range of ionic strength (IS) and pH using batch experiment. The related surface properties (size, zeta potential, and hydrophobicity) under varying conditions were systematically determined and the interaction energy between the cell and minerals were calculated using the extended Derjaguin, Landau, Verwey, and Overbeek (ExDLVO) theory. Adhesion on kaolinite and montmorillonite increased with IS at low level (< 0.01 mol L−1 MgCl2) but declined at high IS level. An increase in IS generally depressed bacterial adhesion on goethite. Elevated pH resulted in decreasing the adhesions on all three minerals. The IS- and pH-effects on adhesion for phyllosilicate systems followed the ExDLVO predictions. For goethite systems, this theory predicted the adhesion trend with IS and that under basic pH, but failed to explain the adhesion at low pH. Such deviation from the theory possibly resulted from chemical interactions between extracellular polymeric substances on cell surface and goethite. These results imply that bacterial adhesions on phyllosilicates are primarily governed by the ExDLVO interactions, and those on iron oxides are mediated by the combination of ExDLVO and non-ExDLVO interactions.

Analysis of capsule related surface properties of Porphyromonas gingivalis isolates

To analyze the capsule related surface properties of Porphyromonas gingivalis (Pg) isolates. The transmission electron microscopy (TEM) was used to observe the capsule structure and the capsule thickness of 2 type of strains and 5 clinical isolates. Microbial adhesion to hydrocarbons (MATH) assay was used to qualitatively assess the hydrophobicity of each strain, and the capacities of these strains were investigated by autoaggregation assay.Ninety-six well biofilm assay and confocal laser scanning microscopy (CLSM) were applied to quantify and observe the biofilm produced by each strain. TEM showed the variety of capsule thickness of these strains.Virulent type strain W83 possessed thicker capsular structure than less-virulent type strain ATCC33277. The SJD4 possessed thicker capsule than other clinical isolates, followed by SJD11, SJD5, SJD2, and SJD12.Strains W83, SJD4, SJD11, with thicker capsule, were much more hydrophilic with lower MATH percentage, in accordance with a slow autoaggregation in incubation during a period of 240 min. Compared with W83, the hydrophobicity of strains ATCC33277, SJD5, SJD2, and SJD12, with thinner capsule, showed increased MATH percentage and autoaggregations. All clinical strains developed biofilm with different absorbance compared with type strains. The CLSM observation showed biofilm thickness of each strain, ranged from (14.74 ± 4.99) to (24.13 ± 5.45) µm. Strain W83 and SJD11 showed notable poor biofilm formation, while others developed dense and mature biofilm. There was a certain degree of linkage between the Pg capsule thickness and surface properties diversity.

Effect of Coal Combustion Products in Reducing Soluble Phosphorus in Soil II: Leaching Study

Phosphorus (P) management in agriculture is crucial for both environmental health and future availability of P resource. Application of P as fertilisers (organic or inorganic) often results in either P accumulation in soil or loss to water bodies, rendering them unavailable to crops. In this study, the mobility of inorganic (KH2PO4 (PP)) and organic (poultry manure (PM)) P sources, as affected by coal combustion products (CCPs: fly ash (FA) and fluidised bed combustion ash (FBC)) application to soils, was evaluated using column leaching experiments. The incubated samples were also characterised using X-ray diffraction (XRD) and scanning electron microscopy (SEM) to understand their surface properties in relation to P adsorption and leaching. The results showed differential effects of CCPs to P treatments—in the case of PP, the CCPs decreased P leaching by 12.11 % (FA) and 20.56 % (FBC), whereas in the case of PM treatment, both CCPs increased P in leachates by 35.53 % (FA) and 18.44 % (FBC). The decrease in P leaching for PP-treated soil as affected by CCPs was attributed to high pH and Ca concentration. There was a negative relationship between the increase in CCP-induced pH and P leaching demonstrating that pH plays a crucial role in P immobilisation, transformation and leaching. The increase in P leaching for CCP-incubated–PM-treated soils was because of the mineralisation of organic P from PM. The surface chemistry from XRD and SEM results showed an increased surface area for CCPs-incubated soil compared to the control and also showed the presence of Ca-rich minerals in CCPs such as ettringite, wollastonite and merwinite.

Long-term impact of agricultural practices on biological soil crusts and their hydrological processes in a semiarid landscape

The natural landscapes of semiarid areas worldwide comprise a series of scattered patches of shrubs within a matrix of biologically crusted soils (BSC). As BSCs are considered ecosystem engineers the relationships between the BSC and the shrub patches determine system functioning. The objective of our study was to investigate long-term effects of agricultural practices on biological soil crusts and their influence on hydrological aspects of a semiarid ecosystem. During 1991, we experimentally simulated five of the area's agricultural practices; 1) Scraping – the topsoil was removed to a depth of 2 cm, 2) Spraying – phototrophic organisms were chemically killed with herbicide, 3) Mowing – perennial vegetation was cut and spread to simulate grazing practices, 4) Car track – a heavy roller was used to simulate car-tracks, 5) Control – undisturbed natural plots. Sixteen years later, in 2007, these agricultural practices were found to have a long-term effect on the crusted soil surface and the related soil-surface properties. Mowing and car-track treatments led to decreased overland runoff and increased hydraulic conductivity, whereas scraping and spraying treatments led to increased overland runoff production and decreased hydraulic conductivity. We conclude that the practices had a long-term residual impact on BSC succession and related soil surface properties, which affected the hydrological processes and system functioning.

Thermophoresis of an Aerosol Sphere with Chemical Reactions

The thermophoretic motion of a spherical aerosol particle undergoing a chemical reaction in a uniformly prescribed temperature gradient is studied theoretically in the quasisteady limit of negligible Peclet and Reynolds numbers. The chemical reaction taking place within the particle can be either endothermic or exothermic. The Knudsen number is assumed to be small (of the order 0.1) so that the fluid flow is described by a model with a thermal slip, a temperature jump, and a frictional slip at the surface of the particle. The energy and momentum equations governing the system are solved analytically, and explicit expressions for the thermophoretic velocity of the particle are obtained. Results of the effect of the chemical reaction inside the particle on its thermophoresis are presented for various distributions of the composition-dependent factor or heat generation parameter of the chemical reaction as well as the relative thermal and surface properties of the aerosol sphere. When the composition-depende...

Decreasing pH trend estimated from 35-year time series of carbonate parameters in the Pacific sector of the Southern Ocean in summer

The Southern Ocean is an important region for investigation because it has a major effect on global air-to-sea CO2 fluxes and because of the ocean acidification resulting from the uptake of anthropogenic carbon, leading to serious consequences for marine ecosystems in the near future. We estimated long-term trends of ocean acidification in surface waters of the Pacific sector of the Southern Ocean, based on the summer observational records of oceanic CO2 partial pressure and related surface properties during 1969–2003. The computed pH time series exhibited substantial decreasing trends in the extensive region from the subtropical to polar zones. The mean rates of pH decrease over the 35-year period were 0.0011 to 0.0013yr−1 in the zones north of the Polar Front and were larger in the polar zone (0.0020yr−1). The contribution of trends in sea surface temperature to the trends of pH decrease was small in all zones. The high rate of pH decrease in the polar zone was attributed to the supply of dissolved inorganic carbon from lower layers, enhanced by intensified wind stress and superimposed onto the accumulation of anthropogenic CO2. A preliminary evaluation of thermodynamic changes in the upper carbonate system, using observational results, projected that the polar zone south of the Polar Front would be undersaturated with respect to aragonite in summer after 80 years.

Photocatalytic Activity and Related Surface Properties of Transparent ZnO Films Prepared by a Low‐temperature Aqueous Route

Transparent ZnO were prepared using solutions with various trisodium citrate concentrations by a spin-spray method at 90°C. The morphological and structural characteristics, as well as photocatalytic activity of the resulting ZnO films were examined with respect to the added trisodium citrate concentration. Photocatalytic activities of the ZnO films were evaluated from photodecomposition of methylene blue (MB) in aqueous solution. With increasing citrate concentrations, the ZnO films came to have higher transmittances in visible region but lower MB decomposition rate. Both high transmittance and high photocatalytic activity were achieved in the ZnO film prepared in the citrate concentration of 0.5 mm. The possible mechanism for the difference in photocatalytic activity by the samples prepared with the various concentrations of citrate was discussed from the viewpoint of film texture, crystal orientation and surface chemical state.

Surface properties of hydrogenated nanodiamonds: a chemical investigation

Hydrogen terminations (C-H) confer to diamond layers specific surface properties such as a negative electron affinity and a superficial conductive layer, opening the way to specific functionalization routes. For example, efficient covalent bonding of diazonium salts or of alkene moieties can be performed on hydrogenated diamond thin films, owing to electronic exchanges at the interface. Here, we report on the chemical reactivity of fully hydrogenated High Pressure High Temperature (HPHT) nanodiamonds (H-NDs) towards such grafting, with respect to the reactivity of as-received NDs. Chemical characterizations such as FTIR, XPS analysis and Zeta potential measurements reveal a clear selectivity of such couplings on H-NDs, suggesting that C-H related surface properties remain dominant even on particles at the nanoscale. These results on hydrogenated NDs open up the route to a broad range of new functionalizations for innovative NDs applications development.

Boundary effects on thermophoresis of aerosol cylinders

An analytical study is presented for the thermophoretic motion of a circular cylindrical particle in a gaseous medium with a transversely imposed temperature gradient near a large plane wall parallel to its axis in the quasisteady limit of negligible Peclet and Reynolds numbers. The Knudsen number is assumed to be small so that the fluid flow is described by a continuum model with a temperature jump, a thermal slip, and a frictional slip at the particle surface. The presence of the confining wall causes two basic effects on the particle velocity: first, the local temperature gradient on the particle surface is altered by the wall, thereby speeding up or slowing down the particle; secondly, the wall enhance the viscous retardation of the moving particle. Through the use of cylindrical bipolar coordinates, the transport equations governing this problem are solved and the wall effects on the thermophoresis of the aerosol cylinder are computed for various cases. The presence of the plane wall can reduce or enhance the particle velocity, depending upon the relative thermal conductivity and surface properties of the particle, the relative particle-wall separation distance, and the direction of the applied temperature gradient. The direction of the thermophoretic motion of a cylindrical particle near a plane wall is different from that of the prescribed thermal gradient, except when it is oriented parallel or perpendicular to the wall. The effects of the plane wall on the thermophoresis of a cylinder are found to be much more significant than those for a sphere at the same separation.

Galling related surface properties of powder metallurgical tool steels alloyed with and without nitrogen

Two types of powder metallurgical tool steels (i.e. with and without nitrogen) are investigated with respect to their galling related surface properties. Despite similar macrohardness values, Vancron 40 (nitrogen alloyed) exhibits superior wear behaviour as compared to Vanadis 10 (without nitrogen); demonstrating approximately 20 times longer life span when used as die material in powder compaction. The main failure mechanism is mild abrasive wear for Vancron 40 and early severe galling for Vanadis 10. One important difference causing the tribological discrepancy is supposed to be associated with the preferred formation of solid lubricant oxides of the Magnéli type on the Vancron 40 surface as compared to Vanadis 10. The VN precipitates in Vancron 40 have half the thermal conductivity compared to that of the VC precipitates existing in Vanadis 10. Hence, as a result of the local accumulation of frictional heat generated during powder compaction (or any other type of forming process), Magnéli phases of V 2O 5 and/or VO 2 are more easily formed and maintained on the Vancron 40 surface. With regard to surface oxides, the tool steels were studied by means of X-ray photoelectron spectroscopy (XPS). The tool steel surfaces were examined by means in situ SEM/AFM and electron backscatter diffraction (EBSD) for local adhesion force measurements and understanding the orientation of the phases, respectively. In addition, pin-on-disc wear tests were performed on the tool steels and the worn surfaces were analysed using scanning election microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDS).

Impacts of CuO x additive on the CO oxidation activity and related surface and bulk properties of a NANO-CeO2 Catalyst

Nano-particle, pure and CuO x -modified, fluorite-structured cubic-CeO2 were successfully synthesized with surface areas near 240 m2/g applying a microemulsion method with mixed templating surfactants (viz. DDAB and Brij®35). Following calcination at 400–800 °C, the products were characterized by X-ray powder diffractometry, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy, and, then, tested as catalysts for methylbutynol decomposition and CO oxidation in the gas phase. Results obtained showed the pure and CuO x -modified cerias to exhibit comparable activities towards the alcohol decomposition into acetone and acetylene, but the modified ceria exhibited considerably higher activity towards the CO oxidation than the pure one. The calcination product of CuO x -modified ceria at 800 °C was capable of lowering the light-off temperature of the CO oxidation from 300 °C (on the pure) down to 70 °C. Surface chemical consequences of the CuO x -modification, viz. increasing the Ce(III)/Ce(IV) atomic ratio, as well as the establishment of Cu(I) and Cu(II) sites, have been allocated the responsibility of the observed upsurge of the CO oxidation activity.

Decreasing pH trend estimated from 25-yr time series of carbonate parameters in the western North Pacific

We estimated long-term trends of ocean acidification in surface waters in latitudinal zones from 3°N to 33°N along the repeat hydrographic line at 137°E in the western North Pacific Ocean. Estimates were based on the observational records of oceanic CO2 partial pressure and related surface properties over the last two decades. The computed pH time series both for 25 yr in winter (late January.early February) and for 21 yr in summer (June.July) exhibited significant decreasing trends in the extensive subtropical to equatorial zones, with interannual variations that were larger in summer. The calculated rates of pH decrease ranged from 0.0015 to 0.0021 yr-1 (average, 0.0018 ± 0.0002 yr-1) in winter and from 0.0008 to 0.0019 yr-1 (average, 0.0013 ) 0.0005 yr-1) in summer. The thermodynamic effects of rising sea surface temperature (SST) accounted for up to 44% (average, 15%) of the trend of pH decrease in the subtropical region in winter, whereas a trend of decreasing SST slowed the pH decrease in the northern subtropical region (around 25°N) in summer. We used the results from recent trends to evaluate future possible thermodynamic changes in the upper ocean carbonate system.

Controlled removal of individual carbon nanotubes from vertically aligned arrays for advanced nanoelectrodes

A simple but effective method has been developed to controllably extract carbon nanotubes (CNTs) from their vertically aligned arrays on growth substrates. The intrinsic micron-scale roughness of the CNT surface enables the protruding nanotubes to make good contact with an adhesive layer which can then remove them from the array on the growth substrate. This approach allows us to manage and tailor the surface morphologies and related surface properties of CNT arrays. The patterned structure of CNT arrays with region-selective control over the density has been achieved. The ability of this process to tailor spacing between vertically aligned CNTs, as demonstrated, opens a new pathway to fabricate the CNT nanoelectrode arrays for applications in electroanalysis.

Thermophoretic motion of slightly deformed aerosol spheres

The thermophoretic motion of a slightly deformed aerosol sphere in a uniformly prescribed but arbitrarily oriented temperature gradient is analyzed in the steady limit of negligible Peclet and Reynolds numbers. The Knudsen number is assumed to be small so that the fluid flow is described by a continuum model with a temperature jump, a thermal slip, and a frictional slip at the surface of the particle. The energy and momentum equations governing the system are solved asymptotically using a method of perturbed expansions. To the second order in the small parameter characterizing the deformation of the aerosol particle from the spherical shape, the thermal and hydrodynamic problems are formulated for the general case, and explicit expressions for the thermophoretic velocity of the particle are obtained for the special cases of prolate and oblate spheroids. The agreement between our asymptotic results for a thermophoretic spheroid and the relevant exact or numerical solutions in the literature is quite good, even if the particle deformation from the spherical shape is not very small. Depending on the values of the relative thermal and surface properties of the aerosol spheroid, its thermophoretic mobility normalized by the corresponding value for a spherical particle with equal equatorial radius is not necessarily a monotonic function of the aspect ratio of the spheroid.