Variations In Surface Chemistry Research Articles

Assembling Mixed Carboxylic Acid Molecules on Hierarchical Structured Aluminum Substrates for the Fabrication of Superoleophobic Surfaces with Controlled Oil Adhesion

AbstractControlling oil adhesion on the superoleophobic surfaces is very important in both fundamental research and practical applications. Herein, we report a new method through modification of mixed carboxylic acid (CH3(CH2)6COOH and CF3(CF2)6COOH) molecules on hierarchical structured aluminum substrates toward the fabrication of superoleophobic surfaces with tunable adhesion. The oil adhesion can be controlled by changing the concentration of CF3(CF2)6COOH (xF) in the modified solution. Detailed research indicates that the tunable effect is ascribed to the combined effect of the surface chemistry variation and the hierarchical structures on the substrates. Furthermore, we also demonstrate an application of our surfaces in a droplet‐based microreactor. The results reported here can not only provide a new idea for fabrication of superoleophobic surfaces with tunable adhesion but can also potentially be used in many applications, such as microfluidic devices and chemical microreactors.

XPS, TDS, and AFM studies of surface chemistry and morphology of Ag-covered L-CVD SnO2 nanolayers.

This is well known that the selectivity and sensitivity of tin dioxide (SnO2) thin film sensors for the detection of low concentration of volatile sulfides such as H2S in air can be improved by small amount of Ag additives. In this paper we present the results of comparative X-ray photoelectron spectroscopy (XPS), thermal desorption spectroscopy (TDS), and atomic force microscopy (AFM) studies of the surface chemistry and morphology of SnO2 nanolayers obtained by laser-enhanced chemical vapor deposition (L-CVD) additionally covered with 1 monolayer (ML) of Ag. For as deposited SnO2 nanolayers, a mixture of tin oxide (SnO) and tin dioxide (SnO2) with the [C]/[Sn] ratio of approximately 1.3 was observed. After dry air exposure, the [O]/[Sn] ratio slightly increased to approximately 1.55. Moreover, an evident increasing of C contamination was observed with [C]/[Sn] ratio of approximately 3.5. After TDS experiment, the [O]/[Sn] ratio goes back to 1.3, whereas C contamination evidently decreases (by factor of 3). Simultaneously, the Ag concentration after air exposure and TDS experiment subsequently decreased (finally by factor of approximately 2), which was caused by the diffusion of Ag atoms into the subsurface layers related to the grain-type surface morphology of Ag-covered L-CVD SnO2 nanolayers, as confirmed by XPS ion depth profiling studies. The variation of surface chemistry of the Ag-covered L-CVD SnO2 after air exposure observed by XPS was in a good correlation with the desorption of residual gases from these nanolayers observed in TDS experiments.

Surface Chemistry Consequences of Mg-Based Coatings on LiNi0.5Mn1.5O4 Electrode Materials upon Operation at High Voltage

LiNi0.5Mn1.5O4 epitomizes the challenges imposed by high electrochemical potential reactivity on the durability of high energy density Li-ion batteries. Postsynthesis coatings have been explored as a solution to these challenges, but the fundamentals of their function have not been ascertained. To contribute to this understanding, the surface of LiNi0.5Mn1.5O4 microparticles was modified with Mg2+, a coating component of literature relevance, using two different heat treatment temperatures, 500 and 800 °C. A combination of characterization tools revealed that Mg2+ was introduced mainly as an inhomogeneous MgO coating in the sample treated at 500 °C, and into the spinel lattice at the subsurface of the particles at 800 °C. Comparing the properties of these two different materials with an unmodified baseline afforded the opportunity to evaluate the effect of varying surface chemistries. Coulometry in Li metal half cells was used as a macroscopic measure of side reactions at the electrode–electrolyte interfa...

Trends in Adsorption Characteristics of Organic Molecules on Transition Metal Surfaces: Role of Surface Chemistry and Van Der Waals Interactions

The accurate description of interface characteristics between organic molecules and metal surfaces has long been debated in theoretical studies. A well-founded description of interface geometry and adsorption energy is highly desirable for these systems. Using first principles calculations with the inclusion of van der Waals interactions, we examine adsorption characteristics of few organic molecules on several transition metal surfaces. Our aim is to obtain insights into the role of vdW interactions in the adsorption characteristics as well as to build understanding how these functional treat the adsorption in varying surface chemistries. Furthermore, the comparisons made between the results obtained using different vdW functionals for each organic molecule type provide the means to assess their performance.This work is funded by the U.S. Department of Energy Basic Energy Science under Contract No DE-FG02-11ER16243

Benzene Adsorption on (110) Surfaces of Transition Metals: Role of Van Der Waals Interaction and Substrate

The characteristics of Benzene adsorption on metals and their alloy surfaces, and the interface features have been the subject of many experimental and theoretical studies. With the availability of the new vdW functionals, we revisit this organic molecule/metal system to assess the influence of vdW interactions on the adsorption as well as to examine the performance of these vdW functionals. We will present the adsorption geometries, adsorption energies and heights, the characteristics of interface electronic structure, and the charge transfer for Benzene adsorption on the (110) surfaces of seven transition metals; Au, Ag, Cu, Pd, Pt, Rh, and Ni. The calculations are carried out using PBE and vdW-DF family functionals implemented in the VASP package. We will provide comparisons with the available experimental and theoretical studies on the adsorption geometries and energies, and the effect introduced by varying surface chemistries. We will also provide comparisons with the recent study for Benzene adsorption on the (111) surfaces of the same metal substrates [1]. [1] H. Yildirim, T. Greber, and A. Kara J. Phys. Chem. C 2013, 117, 20572. This work is funded by the U.S. Department of Energy Basic Energy Science under Contract No DE-FG02-11ER16243

Tantalum coating on TiO2 nanotubes induces superior rate of matrix mineralization and osteofunctionality in human osteoblasts

Nanostructured surface geometries have been the focus of a multitude of recent biomaterial research, and exciting findings have been published. However, only a few publications have directly compared nanostructures of various surface chemistries. The work herein directly compares the response of human osteoblast cells to surfaces of identical nanotube geometries with two well-known orthopedic biomaterials: titanium oxide (TiO2) and tantalum (Ta). The results reveal that the Ta surface chemistry on the nanotube architecture enhances alkaline phosphatase activity, and promotes a ~30% faster rate of matrix mineralization and bone-nodule formation when compared to results on bare TiO2 nanotubes. This study implies that unique combinations of surface chemistry and nanostructure may influence cell behavior due to distinctive physico-chemical properties. These findings are of paramount importance to the orthopedics field for understanding cell behavior in response to subtle alterations in nanostructure and surface chemistry, and will enable further insight into the complex manipulation of biomaterial surfaces. With increased focus in the field of orthopedic materials research on nanostructured surfaces, this study emphasizes the need for careful and systematic review of variations in surface chemistry in concurrence with nanotopographical changes.

Nanoscale engineering of low-fouling surfaces through polydopamine immobilisation of zwitterionic peptides

We report a versatile approach for the design of substrate-independent low-fouling surfaces via mussel-inspired immobilisation of zwitterionic peptides. Using mussel-inspired polydopamine (PDA) coatings, zwitterionic glutamic acid- and lysine-based peptides were immobilised on various substrates, including noble metals, metal oxides, polymers, and semiconductors. The variation of surface chemistry and surface wettability upon surface treatment was monitored with X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Following peptide immobilisation, the surfaces became more hydrophilic due to the strong surface hydration compared with PDA-coated surfaces. The peptide-functionalised surfaces showed resistance to human blood serum adsorption and also effectively prevented the adhesion of gram-negative and gram-positive bacteria (i.e., Escherichia coli and Staphylococcus epidermidis) and mammalian cells (i.e., NIH 3T3 mouse embryonic fibroblast cells). The versatility of mussel-inspired chemistry combined with the unique biological nature and tunability of peptides allows for the design of low-fouling surfaces, making this a promising coating technique for various applications.

PH-Induced Reversible Wetting Transition between the Underwater Superoleophilicity and Superoleophobicity

Surfaces with controlled oil wettability in water have great potential for numerous underwater applications. In this work, we report a smart surface with pH-responsive oil wettability. The surface shows superoleophilicity in acidic water and superoleophobicity in basic water. Reversible transition between the two states can be achieved through alteration of the water pH. Such smart ability of the surface is due to the cooperation between the surface chemistry variation and hierarchical structures on the surface. Furthermore, we also extended this strategy to the copper mesh substrate and realized the selective oil/water separation on the as-prepared film. This paper reports a new surface with excellently controllable underwater oil wettability, and we believe such a surface has a lot of applications, for instance, microfluidic devices, bioadhesion, and antifouling materials.

Preparation of Copper Surfaces with Controlled Wettability Through the Molecular Self-assembling Process†

We report a novel method for the fabrication of copper surfaces with controlled wettability.Through modification of the nanostructured copper substrates with mixed thiol molecules of HS(CH 2) 9 CH 3 and HS(CH 2) 11 OH,surfaces with controlled wettability from superhydrophobicity to superhydrophilicity can be achieved by simply controlling the concentration of HS(CH 2) 11 OH in the modified solution.The controllability of the surfaces wettability can be ascribed to the combined effect of the surface chemistry variation and the hierarchical micro/nanostructures on the substrates.Especially the presence of hierarchical micro/nanostructures,which can provide a better control of the surface wettability between the two extremes: superhydrophobicity and superhydrophilicity.

Underwater Superoleophilic to Superoleophobic Wetting Control on the Nanostructured Copper Substrates

Surfaces with controlled underwater oil wettability would offer great promise in the design and fabrication of novel materials for advanced applications. Herein, we propose a new approach based on self-assembly of mixed thiols (containing both HS(CH2)9CH3 and HS(CH2)11OH) on nanostructured copper substrates for the fabrication of surfaces with controlled underwater oil wettability. By simply changing the concentration of HS(CH2)11OH in the solution, surfaces with controlled oil wettability from the underwater superoleophilicity to superoleophobicity can be achieved. The tunable effect can be due to the synergistic effect of the surface chemistry variation and the nanostructures on the surfaces. Noticeably, the amplified effect of the nanostructures can provide better control of the underwater oil wettability between the two extremes: superoleophilicity and superoleophobicity. Moreover, we also extended the strategy to the copper mesh substrates and realized the selective oil/water separation on the as-prepared copper mesh films. This report offers a flexible approach of fabricating surfaces with controlled oil wettability, which can be further applied to other ordinary materials, and open up new perspectives in manipulation of the surface oil wettability in water.

Trends in Adsorption Characteristics of Benzene on Transition Metal Surfaces: Role of Surface Chemistry and van der Waals Interactions

The accurate description of interface characteristics between organic molecules and metal surfaces has long been debated in theoretical studies. A well-founded description of interface geometry and adsorption energy is highly desirable for these hybrid inorganic/organic interfaces. Using first principles calculations with the inclusion of five van der Waals functionals (vdW-DF family), benzene (C6H6) adsorption on seven transition metal surfaces is studied to explore the performance of these vdW functionals under varying surface chemistry. Our results reveal that vdW interactions are crucial for an accurate description of bonding on transition metal substrates. We find that vdW interactions increase adsorption energy on coinage metal surfaces (Au, Ag, Cu) by about 0.7 eV, while they lead to even larger increases in the adsorption energies on the reactive transition metal surfaces (Pd, Pt, Rh, Ni). Our calculations also reveal that changes in adsorption energies stemming from vdW functionals show significa...

Non-wetting droplets on hot superhydrophilic surfaces

Controlling wettability by varying surface chemistry and roughness or by applying external stimuli is of interest for a wide range of applications including microfluidics, drag reduction, self-cleaning, water harvesting, anti-corrosion, anti-fogging, anti-icing and thermal management. It has been well known that droplets on textured hydrophilic, that is superhydrophilic, surfaces form thin films with near-zero contact angles. Here we report an unexpected behaviour where non-wetting droplets are formed by slightly heating superhydrophilic microstructured surfaces beyond the saturation temperature (>5 °C). Although such behaviour is generally not expected on superhydrophilic surfaces, an evaporation-induced pressure in the structured region prevents wetting. In particular, the increased thermal conductivity and decreased vapour permeability of the structured region allows this behaviour to be observed at such low temperatures. This phenomenon is distinct from the widely researched Leidenfrost and offers an expanded parametric space for fabricating surfaces with desired temperature-dependent wettability.

Dairy Biofilm: Impact of Microbial Community on Raw Milk Quality

AbstractThe aims of this study were (1) to characterize the dairy biofilm, and (2) to evaluate the impact on the raw milk quality. The ecological profile of biofilm revealed that gram‐positive bacteria and fungi exhibited a significantly higher biofilm organization than gram‐negative (43–64%). From 16S rDNA sequencing, microbial diversity of biofilm was constituted by Lactococcus lactis, Staphylococcus xylosus, Bacilus cereus, Candida albicans. The milk analysis in input and in output of pipelines has revealed that the rate of milk microbial community has increased to attempt 97 to 100%. The investigation of the impact of biofilm on the physicochemical properties of material has showed a decrease of hydrophobicity of stainless steel which become hydrophilic after 7 h of contact (ΔGiwi = 6.62 mJ/m2) and the increase of the electron donor character (γ− = 44.8 mJ/m2). While, after 24 h of contact, results showed a decrease of the hydrophilicity degree and surface energy components of stainless steel that become hydrophobic (ΔGiwi = −56.51 mJ/m2) and lowly electron donor (γ− = 2.3 mJ/m2).Practical ApplicationsDairy biofilm formation on stainless steel was investigated employing thermodynamic approach. The results revealed that the microbial adhesion on substrata was dependent on two factors: materials species and microorganisms community. These findings have important potential in the food process applicability as they suggest that the variation of surface chemistry could contribute to understand the biofilm formation to surface and also favor the protective biofilms approach on industry workshop surfaces that favors the antimicrobial coating of devices makes it simultaneously anti‐adhesive and give it antimicrobial activity.

Cu(II) incorporation to schwertmannite: Effect on stability and reactivity under AMD conditions

The formation, transformation and surface chemistry of iron oxides is geologically important in surface waters polluted by acid mine drainage (AMD). The geochemical behaviour of these oxides controls the availability and mobility of contaminants in such highly polluted systems. The low pH values, together with the presence of large amounts of sulphate, favour the formation of schwertmannite, which is a metastable iron oxide that is transformed to goethite under oxic conditions. However, in copper mining environments, co-precipitation of iron and copper ions is expected and therefore the surface chemistry of the iron oxides present in these systems may be different.Several schwertmannite samples were prepared in the presence of high concentrations of sulphate and different concentrations of copper to simulate copper-rich mining environments. Long-term transformation experiments were conducted to study the mineral oxide stability and variations in surface chemistry produced over a period of 15months. Schwertmannite-like particles were initially formed, but sulphate release and the dissolution and re-precipitation of iron and copper ions occurred under more acidic conditions throughout the experiment, which led to the formation of goethite-like particles. The capacity for arsenate adsorption was highest in the initial schwertmannite-like particles, and arsenate mobility increased in the presence of more stable iron mineral phases that were formed throughout the transformation experiment.

Powder Technology and Pharmaceutical Development: Particle Size and Particle Adhesion

Both the FDA (U.S. Food and Drug Administration) and ICH (International Conference on Harmonisation) have urged the incorporation of Quality by Design (QbD)1) into the manufacture of pharmaceutical products2).The performance of many pharmaceutical manufacturing processes and the performance of some pharmaceutical products requires a knowledge of powder properties. Under the principles of QbD it is possible to adjust processes to account for variations in powder properties. These adjustments, in turn, require knowledge of the relation between powder properties and manufacturing performance. This relation between powder properties and performance is often not well understood; thus, the required information is not collected.In this paper, particle-particle and particle-surface interactions are considered to be a source of product variability. As particle size effects are intertwined with particle adhesion effects this topic is also considered. From the discussion below, it can be seen that the surface chemistry of particles can vary due to mechanical treatment, crystallization solvent, and surface contamination. Variations in surface chemistry affect interparticle adhesion and thus may lead to process or product performance changes. Issues concerning the role of interparticle adhesion that are related to tableting and dry powder inhalers are discussed in some detail.It is clear that a deeper understanding of the powder state and the establishment of appropriate analytical tools will be required to fully implement QbD. Improvements in particle sizing technologies, improvements powder sampling procedures and measurements of particle surface properties will be required. It is hoped that this paper will stimulate thought on this issue.

The role of surface chemistry-induced cell characteristics on nonviral gene delivery to mouse fibroblasts

BackgroundGene delivery approaches serve as a platform to modify gene expression of a cell population with applications including functional genomics, tissue engineering, and gene therapy. The delivery of exogenous genetic material via nonviral vectors has proven to be less toxic and to cause less of an immune response in comparison to viral vectors, but with decreased efficiency of gene transfer. Attempts have been made to improve nonviral gene transfer efficiency by modifying physicochemical properties of gene delivery vectors as well as developing new delivery techniques. In order to further improve and understand nonviral gene delivery, our approach focuses on the cell-material interface, since materials are known to modulate cell behavior, potentially rendering cells more responsive to nonviral gene transfer. In this study, self-assembled monolayers of alkanethiols on gold were employed as model biomaterial interfaces with varying surface chemistries. NIH/3T3 mouse fibroblasts were seeded on the modified surfaces and transfected using either lipid- or polymer- based complexing agents.ResultsTransfection was increased in cells on charged hydrophilic surfaces presenting carboxylic acid terminal functional groups, while cells on uncharged hydrophobic surfaces presenting methyl terminations demonstrated reduced transfection for both complexing agents. Surface–induced cellular characteristics that were hypothesized to affect nonviral gene transfer were subsequently investigated. Cells on charged hydrophilic surfaces presented higher cell densities, more cell spreading, more cells with ellipsoid morphologies, and increased quantities of focal adhesions and cytoskeleton features within cells, in contrast to cell on uncharged hydrophobic surfaces, and these cell behaviors were subsequently correlated to transfection characteristics.ConclusionsExtracellular influences on nonviral gene delivery were investigated by evaluating the upregulation and downregulation of transgene expression as a function of the cell behaviors induced by changes in the cells’ microenvronments. This study demonstrates that simple surface modifications can lead to changes in the efficiency of nonviral gene delivery. In addition, statistically significant differences in various surface-induced cell characteristics were statistically correlated to transfection trends in fibroblasts using both lipid and polymer mediated DNA delivery approaches. The correlations between the evaluated complexing agents and cell behaviors (cell density, spreading, shape, cytoskeleton, focal adhesions, and viability) suggest that polymer-mediated transfection is correlated to cell morphological traits while lipid-mediated transfection correlates to proliferative characteristics.

Composites with Macroporous Poly(vinyl alcohol) Cryogels with Attached Activated Carbon Microparticles with Controlled Accessibility of a Surface

A set of glutaraldehyde (GA) cross-linked poly(vinyl alcohol)/activated carbon (PVA/GA/AC) composites prepared in the form of monolithic rods using a cryogelation technique and studied using adsorption, mercury porosimetry, scanning electron microscopy (SEM), and quantum chemistry methods display porosity similar to that of PVA/GA cryogel at a high GA content (content ratio GA/AC = 1 and GA/PVA = 0.2). GA cross-linked PVA multilayer coverage is an effective barrier for adsorption on AC particles. Variations in surface chemistry (AC initial and oxidized in air at 300 °C for 12 h) and content (14-62.5%w/w) of ACs in PVA/GA/AC composites relatively weakly affect their textural characteristics at a high GA content (specific surface area S(BET) < 120 m²/g, pore volume V(p) < 0.35 cm³/g). However, PVA/GA/AC composite rods formed with a lower concentration of GA (content ratio GA/AC = 1/6 and GA/PVA = 1/10) have significantly greater S(BET) (∼500 m²/g) and V(p) (>0.55 cm³/g) values because of improved accessibility of the AC surface. This provides better adsorption of methylene blue as a probe compound.

Directed Assembly of Janus Particles under High Frequency ac-Electric Fields: Effects of Medium Conductivity and Colloidal Surface Chemistry

The manipulation and assembly of polystyrene-based Janus particles of varied surface chemistry on one hemispherical particle surface under high frequency nonuniform ac-electric fields is examined experimentally by in situ microscopic observation. Strong effects of ac-field frequency, medium conductivity, and particle surface chemistry on the structure of Janus colloidal assembly are observed. At low medium conductivity, σ(m) from 0.0007 S/m to 0.0153 S/m, pearl chains of Janus particles are observed over the ac-frequency range from 25 kHz to 20 MHz, indicating the dielectrophoresis (DEP)-directed assembly. In contrast, the chaining of Janus particles is disrupted in a certain frequency range at high σ(m) from 0.0153 S/m to 0.116 S/m, suggesting the combining effects of both induced-charge electrophoresis (ICEP) and DEP. The critical transition frequency for the onset of the fractal aggregation at high σ(m) from 0.0153 S/m to 0.116 S/m is experimentally determined, showing a good agreement with the theoretically predicted upper ICEP frequency limit. Additionally, it is demonstrated that by using zwitterionic Janus particles, the assembled structure of Janus particles under ac-fields can be modified by the chemical coatings on each hemispherical surface of Janus particles.

Pt/carbon materials as bi-functional catalysts for n-decane hydroisomerization

The activity and selectivity of bi-functional carbon-supported platinum catalysts for the hydroisomerization of n-alkanes have been studied. The influence of the properties of the carbon support on the performance of the catalysts were investigated by incorporating the metallic function on a series of carbons with varied porosity (microporous: GL-50 from Norit, and mesoporous: CMK-3) and surface chemistry (modified by wet oxidation). The characterization results achieved with H2 chemisorption and TEM showed differences in surface metal concentrations and metal–support interactions depending on the support composition. The highest metal dispersion was achieved after oxidation of the carbon matrix in concentrated nitric acid, suggesting that the presence of surface functional sites distributed in inner and outer surface favors a homogeneous metal distribution. On the other hand, the higher hydrogenating activity of the catalysts prepared with the mesoporous carbon pointed out that a fast molecular traffic inside the pores plays an important role in the catalysts performance. For n-decane hydroisomerization of long chain n-alkanes, higher activities were obtained for the catalysts with an optimized acidity and metal dispersion along with adequate porosity, pointing out the importance of the support properties in the performance of the catalysts.

A study on fire retardancy and durability performance of bagasse fiber/polypropylene composite for outdoor applications

Wood–plastic composites (WPCs) and natural fiber composites (NFCs) are increasingly used in decking applications, where exterior exposure can lead to photodegradation and fungal deterioration. Since the fire retardancy is another proficiency concern of these composites, bagasse/polypropylene composites were produced by incorporation of commercially available additives including flame retardants, ultraviolet (UV) stabilizer, antifungal agent and color masterbatches. The addition of the flame retardant which decomposed at high temperature could result in NFC with significant decrease in burning rate (up to 98%) compared to the composite without flame retardant. Simultaneous effects of antifungal agent and green masterbatch lead to complete suppression of the fungal growth and reproduction on composites exposed to either Lentinus edodes, Pleurotus eryngii strain or each of them accompanied by Trichoderma sp. fungus. Durability performance followed by discoloration, mechanical properties loss and surface chemistry variation depended on all additives used. The results indicated that darker color pigment improved color stability and caused much lower fading for UV-stabilized NFC in comparison to the nonstabilized unpigmented composite.