Showing papers on "Surface modification published in 2014"

Carbon nanotubes: properties, synthesis, purification, and medical applications

Abstract: Current discoveries of different forms of carbon nanostructures have motivated research on their applications in various fields. They hold promise for applications in medicine, gene, and drug delivery areas. Many different production methods for carbon nanotubes (CNTs) have been introduced; functionalization, filling, doping, and chemical modification have been achieved, and characterization, separation, and manipulation of individual CNTs are now possible. Parameters such as structure, surface area, surface charge, size distribution, surface chemistry, and agglomeration state as well as purity of the samples have considerable impact on the reactivity of carbon nanotubes. Otherwise, the strength and flexibility of carbon nanotubes make them of potential use in controlling other nanoscale structures, which suggests they will have a significant role in nanotechnology engineering.

Covalent surface modification of oxide surfaces.

Abstract: The modification of surfaces by the deposition of a robust overlayer provides an excellent handle with which to tune the properties of a bulk substrate to those of interest. Such control over the surface properties becomes increasingly important with the continuing efforts at down-sizing the active components in optoelectronic devices, and the corresponding increase in the surface area/volume ratio. Relevant properties to tune include the degree to which a surface is wetted by water or oil. Analogously, for biosensing applications there is an increasing interest in so-called “romantic surfaces”: surfaces that repel all biological entities, apart from one, to which it binds strongly. Such systems require both long lasting and highly specific tuning of the surface properties. This Review presents one approach to obtain robust surface modifications of the surface of oxides, namely the covalent attachment of monolayers.

Thin-Film Composite Polyamide Membranes Functionalized with Biocidal Graphene Oxide Nanosheets

Abstract: Fouling of membranes by microorganisms is a major limiting factor in membrane separation processes. Novel strategies are therefore required to decrease the extent of bacterial growth on membranes. In this study, we confer strong antimicrobial properties to thin-film composite polyamide membranes by a simple graphene oxide surface functionalization. Using amide coupling between carboxyl groups of graphene oxide and carboxyl groups of the polyamide active layer, graphene oxide is irreversibly bound to the membrane. Surface binding of graphene oxide is demonstrated by scanning electron microscopy and Raman spectroscopy. Direct contact of bacteria with functionalized graphene oxide on the membrane surface results in 65% bacterial inactivation after 1 h of contact time. This bactericidal effect is imparted to the membrane without any detrimental effect to the intrinsic membrane transport properties. Our results suggest that functionalization of thin-film composite membranes with graphene oxide nanosheets is a ...

Maximum surface charge density for triboelectric nanogenerators achieved by ionized-air injection: methodology and theoretical understanding.

Abstract: For the maximization of the surface charge density in triboelectric nanogenerators, a new method of injecting single-polarity ions onto surfaces is introduced for the generation of surface charges. The triboelectric nanogenerator's output power gets greatly enhanced and its maximum surface charge density is systematically studied, which shows a huge room for the improvement of the output of triboelectric nanogenerators by surface modification.

Harvesting water wave energy by asymmetric screening of electrostatic charges on a nanostructured hydrophobic thin-film surface

Abstract: Energy harvesting from ambient water motions is a desirable but underexplored solution to on-site energy demand for self-powered electronics. Here we report a liquid-solid electrification-enabled generator based on a fluorinated ethylene propylene thin film, below which an array of electrodes are fabricated. The surface of the thin film is charged first due to the water-solid contact electrification. Aligned nanowires created on the thin film make it hydrophobic and also increase the surface area. Then the asymmetric screening to the surface charges by the waving water during emerging and submerging processes causes the free electrons on the electrodes to flow through an external load, resulting in power generation. The generator produces sufficient output power for driving an array of small electronics during direct interaction with water bodies, including surface waves and falling drops. Polymer-nanowire-based surface modification increases the contact area at the liquid-solid interface, leading to enhanced surface charging density and thus electric output at an efficiency of 7.7%. Our planar-structured generator features an all-in-one design without separate and movable components for capturing and transmitting mechanical energy. It has extremely lightweight and small volume, making it a portable, flexible, and convenient power solution that can be applied on the ocean/river surface, at coastal/offshore areas, and even in rainy places. Considering the demonstrated scalability, it can also be possibly used in large-scale energy generation if layers of planar sheets are connected into a network.

Polydopamine-based simple and versatile surface modification of polymeric nano drug carriers.

Abstract: The surface of a polymeric nanoparticle (NP) is often functionalized with cell-interactive ligands and/or additional polymeric layers to control NP interaction with cells and proteins. However, such modification is not always straightforward when the surface is not chemically reactive. For this reason, most NP functionalization processes employ reactive linkers or coupling agents or involve prefunctionalization of the polymer, which are complicated and inefficient. Moreover, prefunctionalized polymers can lose the ability to encapsulate and retain a drug if the added ligands change the chemical properties of the polymer. To overcome this challenge, we use dopamine polymerization as a way of functionalizing NP surfaces. This method includes brief incubation of the preformed NPs in a weak alkaline solution of dopamine, followed by secondary incubation with desired ligands. Using this method, we have functionalized poly(lactic-co-glycolic acid) (PLGA) NPs with three representative surface modifiers: a small ...

Nanofibrillated cellulose: surface modification and potential applications

Abstract: Interest in nanofibrillated cellulose has been increasing exponentially because of its relatively ease of preparation in high yield, high specific surface area, high strength and stiffness, low weight and biodegradability etc. This bio-based nanomaterial has been used mainly in nanocomposites due to its outstanding reinforcing potential. Solvent casting, melt mixing, in situ polymerization and electrospinning are important techniques for the fabrication of nanofibrillated cellulose-based nanocomposites. Due to hydrophilic character along with inherent tendency to form strong network held through hydrogen-bonding, nanofibrillated cellulose cannot uniformly be dispersed in most non-polar polymer matrices. Therefore, surface modification based on polymer grafting, coupling agents, acetylation and cationic modification was used in order to improve compatibility and homogeneous dispersion within polymer matrices. Nanofibrillated cellulose opens the way towards intense and promising research with expanding area of potential applications, including nanocomposite materials, paper and paperboard additive, biomedical applications and as adsorbent.

Insights into the catalytic activity and surface modification of MoO3 during the hydrodeoxygenation of lignin-derived model compounds into aromatic hydrocarbons under low hydrogen pressures

Abstract: MoO3 is an effective catalyst for the hydrodeoxygenation (HDO) of lignin-derived oxygenates to generate high yields of aromatic hydrocarbons without ring-saturated products. The catalyst is selective for the C–O bond cleavage under low H2 pressures (≤1 bar) and temperatures ranging from 593 to 623 K. A bond-dissociation energy analysis of relevant phenolic C–O bonds indicates that the bond strengths follow an order of Ph–OH > Ph–OMe > Ph–O–Ph > Ph–O–Me. However, for all model compounds investigated, the MoO3 catalyst preferentially cleaves phenolic Ph–OMe bonds over weaker aliphatic Ph–O–Me bonds. Characterisation studies reveal that the catalyst surface undergoes partial carburisation as evidenced by the presence of oxycarbide- and oxycarbohydride-containing phases (i.e., MoOxCyHz). The transformation of bulk phases and the surface modification of MoO3 by carbon–H2 are investigated to understand the role of surface carbon in the stabilisation and enhanced activity of the partially reduced MoO3 surface.

Surface Functionalization of Thin-Film Composite Membranes with Copper Nanoparticles for Antimicrobial Surface Properties

Abstract: Biofouling is a major operational challenge in reverse osmosis (RO) desalination, motivating a search for improved biofouling control strategies. Copper, long known for its antibacterial activity and relatively low cost, is an attractive potential biocidal agent. In this paper, we present a method for loading copper nanoparticles (Cu-NPs) on the surface of a thin-film composite (TFC) polyamide RO membrane. Cu-NPs were synthesized using polyethyleneimine (PEI) as a capping agent, resulting in particles with an average radius of 34 nm and a copper content between 39 and 49 wt.%. The positive charge of the Cu-NPs imparted by the PEI allowed a simple electrostatic functionalization of the negatively charged RO membrane. We confirmed functionalization and irreversible binding of the Cu-NPs to the membrane surface with SEM and XPS after exposing the membrane to bath sonication. We also demonstrated that Cu-NP functionalization can be repeated after the Cu-NPs dissolve from the membrane surface. The Cu-NP functi...

Surface Modification of Aramid Fibers by Bio-Inspired Poly(dopamine) and Epoxy Functionalized Silane Grafting

Abstract: A novel biomimetic surface modification method for meta-aramid (MPIA) fibers and the improvement on adhesion with rubber matrix was demonstrated. Inspired by the composition of adhesive proteins in mussels, we used dopamine (DOPA) self-polymerization to form thin, surface-adherent poly(dopamine) (PDA) films onto the surface of MPIA fibers simply by immersing MPIA fibers in a dopamine solution at room temperature. An epoxy functionalized silane (KH560) grafting was then carried out on the surface of the poly(dopamine)-coated MPIA, either by a “one-step” or “two-step” method, to introduce an epoxy group onto the MPIA fiber surface. The surface composition and microstructure of the modified MPIA was characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The results indicated successful grafting of KH560 on the PDA-coated MPIA surface. A single-fiber pull...

Colloidal-sized metal-organic frameworks: synthesis and applications.

Abstract: Colloidal metal–organic frameworks (CMOFs), nanoporous colloidal-sized crystals that are uniform in both size and polyhedral shape, are crystals composed of metal ions and organic bridging ligands, which can be used as building blocks for self-assembly in organic and aqueous liquids. They stand in contrast to conventional metal–organic frameworks (MOFs), which scientists normally study in the form of bulk crystalline powders. However, powder MOFs generally have random crystal size and shape and therefore do not possess either a definite mutual arrangement with adjacent particles or uniformity. CMOFs do have this quality, which can be important in vital uptake and release kinetics.In this Account, we present the diverse methods of synthesis, pore chemistry control, surface modification, and assembly techniques of CMOFs. In addition, we survey recent achievements and future applications in this emerging field. There is potential for a paradigm shift, away from using just bulk crystalline powders, towards us...

Plasma surface modification of polymers: relevance to adhesion

Abstract: Preface TECHNOLOGY REVIEW Plasma surface modification of polymers for improved adhesion: a critical review E.M. Liston, L. Martinu and M.R. Wertheimer CHARACTERIZATION OF PLASMA-TREATED SURFACES XPS studies of in situ plasma-modified polymer surfaces L.J. Gerenser Multitechnique study of hexatriacontane surfaces modified by argon and oxygen RF plasmas: effect of treatment time and functionalization, and comparison with HDPE F. Clouet, M.K. Shi, R. Prat, Y. Holl, P. Marie, D. LA(c)onard, Y. De Puydt, P. Bertrand, J.-L. Dewez and A. Doren Plasma surface modification of polyethylene: short-term vs. long-term plasma treatment R. Foerch, G. Kill and M.J. Walzak Plasma oxidation of polystyrene vs. polyethylene R.K. Wells, J.P.S. Badyal, I.W. Drummond, K.S. Robinson and F.J. Street Evolution of the surface composition and topography of perfluorinated polymers following ammonia-plasma treatment T.R. Gengenbach, X. Xie, R.C. Chatelier and H.J. Griesser Surface fluorination of polyethylene films by different glow discharges. Effects of frequency and electrode configuration Y. Khairallah, F. Arefi, J. Amouroux, D. Leonard and P. Bertrand Reactivity of a polypropylene surface modified in a nitrogen plasma F. Poncin-Epaillard, B. Chevet and J.-C. Brosse PRACTICAL APPLICATIONS OF PLASMA-TREATED SURFACES Chemical reactions on plasma-treated polyethylene surfaces M. Morra, E. Occhiello and F. Garbassi Immobilization of polyethylene oxide surfactants for non-fouling biomaterial surfaces using an argon glow discharge treatment M.-S. Sheu, A.S. Hoffman, B.D. Ratner, J. Feijen and J.M. Harris Plasma surface treatment of poly(p-phenylene benzobisthiozol) fibers Y. Qiu, S. Deflon and P. Schwartz CO2 plasma modification of high-modulus cerbon fibers and their adhesion to epoxy resins R.E. Allred and W.C. Schimpf Oxygen plasma modification of polyimide webs: effect of ion bombardment on metal adhesion F.D. Egitto, L.J. Matienzo, K.J. Blackwell and A.R. Knoll Enhancement of the sticking coefficient of Mg on polypropylene by in situ ECR-RF Ar and N2 plasma treatments M. Collaud, S. Nowak, O.M. KA ttel and L. Schlapbach Improved adhesion between plasma-treated polyimide film and evaporated copper N. Inagaki, S. Tanaka and K. Hibi

Overcoming the limitations of directed C–H functionalizations of heterocycles

Abstract: In directed C-H activation reactions, any nitrogen or sulphur atoms present in heterocyclic substrates will coordinate strongly with metal catalysts. This coordination, which can lead to catalyst poisoning or C-H functionalization at an undesired position, limits the application of C-H activation reactions in heterocycle-based drug discovery(1-5), in which regard they have attracted much interest from pharmaceutical companies(3-5). Here we report a robust and synthetically useful method that overcomes the complications associated with performing C-H functionalization reactions on heterocycles. Our approach employs a simple N-methoxy amide group, which serves as both a directing group and an anionic ligand that promotes the in situ generation of the reactive PdX2 (X = ArCONOMe) species from a Pd(0) source using air as the sole oxidant. In this way, the PdX2 species is localized near the target C-H bond, avoiding interference from any nitrogen or sulphur atoms present in the heterocyclic substrates. This reaction overrides the conventional positional selectivity patterns observed with substrates containing strongly coordinating heteroatoms, including nitrogen, sulphur and phosphorus. Thus, this operationally simple aerobic reaction demonstrates that it is possible to bypass a fundamental limitation that has long plagued applications of directed C-H activation in medicinal chemistry.

Porous silicon chemical sensors and biosensors: A review

Abstract: The use of porous silicon (PSi) as a sensor for detection of various analytes is reviewed. The optical or electrical properties of PSi are key sensing parameters that have been used in many chemical and biological sensing applications. PSi is a promising candidate due to ease of fabrication, large surface area, various accessible pore sizes and morphologies, controllable surface modification and its compatibility with conventional silicon processing technology. The adsorption of chemical or biological molecules into the pores modifies the electrical and/or optical properties, allowing convenient and sensitive measurement approach. In this review, we provide a critical assessment of the development of PSi as a promising material for chemical and biosensing applications. Formation procedures of PSi with various pore sizes and morphologies are firstly given. Surface properties and structural characteristics of the material are briefly described. The recent progress on utilization of such porous structures in chemical and biosensing applications is then addressed in the context of surface chemistry effects and nanostructures, measuring approaches, operating concepts and device sensitivity and stability. Finally, concluding remarks with existing challenges that hinder the material for commercial use are highlighted.

Gradient nanostructure and residual stresses induced by Ultrasonic Nano-crystal Surface Modification in 304 austenitic stainless steel for high strength and high ductility

Abstract: In this study, the effects of Ultrasonic Nano-crystal Surface Modification (UNSM) on residual stresses, microstructure changes and mechanical properties of austenitic stainless steel 304 were investigated. The dynamic impacts induced by UNSM leads to surface nanocrystallization, martensite formation, and the generation of high magnitude of surface compressive residual stresses (−1400 MPa) and hardening. Highly dense deformation twins were generated in material subsurface to a depth of 100 µm. These deformation twins significantly improve material work-hardening capacity by acting both as dislocation blockers and dislocation emission sources. Furthermore, the gradually changing martensite volume fraction ensures strong interfacial strength between the ductile interior and the two nanocrystalline surface layers and thus prevents early necking. The microstructure with two strong surface layers and a compliant interior embedded with dense nanoscale deformation twins and dislocations leads to both high strength and high ductility. The work-hardened surface layers (3.5 times the original hardness) and high magnitude of compressive residual stresses lead to significant improvement in fatigue performance; the fatigue endurance limit was increased by 100 MPa. The results have demonstrated that UNSM is a powerful surface engineering technique that can improve component mechanical properties and performance.

Polydopamine as an efficient and robust platform to functionalize carbon fiber for high-performance polymer composites.

Abstract: Carbon fibers (CFs), which exhibit excellent physical performances and low density, suffer from their low surface activity in some application. Herein, based on dopamine chemistry, we proposed an efficient method to functionalize them: through a simple dip-coating procedure, the CFs were inverted from amphiphobic to hydrophilic with deposition of polydopamine film. Furthermore, using polydopamine as a bridge, the hydrophilic functionalized CFs were transformed to be oleophilic after following octadecylamine grafting. To illustrate applications of this functionalization strategy, we added 15 wt % functionalized CFs into polar epoxy and nonpolar poly(ethylene-co-octene), and as a consequence, their tensile strength respectively increase by 70 and 60%, which show greater reinforcing effect than the unmodified ones (35 and 35%). The results of dynamic mechanical analysis and scanning electron microscope observations indicate that this polydopamine-based functionalization route brought about satisfactory impro...

Recent developments of thiacalixarene based molecular motifs

Abstract: Thiacalixarenes, a subclass of "third generation" calixarenes, exhibit many interesting features such as enlarged ring size, facile chemical modification, and metal complexation due to the presence of bridging sulfur atoms. The thiacalixarene scaffold is a unique host with vast possibilities for functionalization not only at the upper and lower rim but also at the bridging sulfide groups. Modified thiacalixarenes have been used for many applications such as the detection and separation of biologically important cations, anions, and bio-analytes, mimicking molecular logic gates and devices, and synthesis of self-assembled coordination cages, multinuclear complexes, magnetic materials and luminescent materials. This review article summarizes recent developments in the derivatization methods of thiacalixarenes and their utilization in various applications.

Hydrophobic modification on surface of chitin sponges for highly effective separation of oil.

Abstract: A highly hydrophobic and oleophilic chitin sponge was synthesized, for the first time, via a freeze-dried method and then by using a thermal chemical vapor deposition of methyltrichlorosilane (MTCS) at different relative humidity. Fourier-transform infrared, energy-dispersive X-ray spectra, and scanning electron microscopy confirmed that the silanization occurred on the pore wall surface of the chitin sponge. The MTCS-coated chitin sponge had interconnected open-cell structures with the average pore size from 20 to 50 μm, and the MTCS nanofilaments immobilized on the chitin matrix, leading to the high hydrophobicity, as a result of the existence of a solid/air composite rough surface. Cyclic compression test indicated that the hydrophobic chitin sponges exhibited excellent elasticity and high mechanical durability. The sponges could efficiently collect organics both on the surface and bottom from the water with the highest 58 times of their own weight absorption capacities through the combination of the p...

Enhanced energy storage density in poly(vinylidene fluoride) nanocomposites by a small loading of suface-hydroxylated Ba0.6Sr0.4TiO3 nanofibers.

Abstract: The ceramic–polymer nanocomposites consisting of Ba0.6Sr0.4TiO3 nanofibers (BST60 NF) with a large aspect ratio prepared via electrospinning and employing surface hydroxylated as fillers and poly(vinylidene fluoride) (PVDF) as matrix have been fabricated by a solution casting method. The nanocomposites exhibit enhanced permittivity, reduced loss tangents and improved breakdown electric field strength at a low volume fraction of hydroxylated BST60 NF. The energy density of the nanocomposites is significantly enhanced, and the maximal energy density of 6.4 J/cm3 is obtained in the composite material with 2.5 wt % hydroxylated BST60 NF, which is more than doubled as compared with the pure PVDF. Such significant enhancements result from combined effect of the large aspect ratio, the surface modification and the improved crystallinity of the nanocomposites induced by the hydroxylated BST60 NF. This work may provide a route for using the hydroxylated ceramic nanofibers to enhance the dielectric energy density i...

Controllable fabrication of nanostructured materials for photoelectrochemical water splitting via atomic layer deposition

Abstract: Photoelectrochemical (PEC) water splitting is an attractive approach to generate hydrogen as a clean chemical fuel from solar energy. But there remain many fundamental issues to be solved, including inadequate photon absorption, short carrier diffusion length, surface recombination, vulnerability to photo-corrosion, and unfavorable reaction kinetics. Owing to its self-limiting surface reaction mechanism, atomic layer deposition (ALD) is capable of depositing thin films in a highly controllable manner, which makes it an enabling technique to overcome some of the key challenges confronted by PEC water splitting. This tutorial review describes some unique and representative applications of ALD in fabricating high performance PEC electrodes with various nanostructures, including (i) coating conformal thin films on three-dimensional scaffolds to facilitate the separation and migration of photocarriers and enhance light trapping, as well as realizing controllable doping for bandgap engineering and forming homojunctions for carrier separation; (ii) achieving surface modification through deposition of anti-corrosion layers, surface state passivation layers, and surface catalytic layers; and (iii) identifying the main rate limiting steps with model electrodes with highly defined thickness, composition, and interfacial structure.