Showing papers on "Surface modification published in 2003"
TL;DR: In this paper, the chemical reduction of graphite oxide (GO) to graphite by either NaBH4 or hydroquinone and also its surface modification with neutral, primary aliphatic amines and amino acids are described.
Abstract: The chemical reduction of graphite oxide (GO) to graphite by either NaBH4 or hydroquinone and also its surface modification with neutral, primary aliphatic amines and amino acids are described. Treatment of GO with NaBH4 leads to turbostatic graphite that upon calcination under an inert atmosphere is transformed to highly ordered graphitic carbon, while the reduction with hydroquinone yields directly crystalline graphite under soft thermal conditions. On account of the surface-exposed epoxy groups present in the GO solid, its surface modification with neutral, primary aliphatic amines or amine-containing molecules (amino acids and aminosiloxanes) takes place easily through the corresponding nucleophilic substitution reactions. In this way, valuable GO derivatives can be obtained, like molecular pillared GO, organically modified GO affording in organic solvents stable organosols or hydrophilic GO affording in water stable hydrosols and possessing direct cation exchange sites. The potential combination of s...
1,168 citations
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07 Nov 2003TL;DR: In this article, the authors present an analysis of Diffraction patterns on the surface of liquid surfaces of liquid and liquid liquids. But their focus is on the electric double layer of the double layer.
Abstract: 1. Introduction 2. Liquid Surfaces 3. Thermodynamics of Interfaces 4. Charged Interfaces and the Electric Double Layer 5. Surface Forces 6. Contact Angle Phenomena and Wetting 7. Solid Surfaces 8. Adsorption 9. Surface Modification 10. Friction, Lubrication, and Wear 11. Surfactants, Micelles, Emulsions, and Foams 12. Thin Films on Surfaces of Liquids 13. Solutions to Exercises 14. Analysis of Diffraction Patterns
1,157 citations
TL;DR: In this paper, a series of new mesoporous silica materials with MCM-41 type of structure containing a homogeneous layer of organic functional groups inside the pores was prepared using a co-condensation method under low surfactant concentration condition.
Abstract: A series of new mesoporous silica materials with MCM-41 type of structure containing a homogeneous layer of organic functional groups inside the pores was prepared using a co-condensation method under low surfactant concentration condition. This reproducible synthetic approach resulted in high surface coverage with several functional groups such as a primary amine, secondary amine, urea, isocyanate, vinyl, and nitrile. In addition, the presence of organoalkoxysilane precursors during the base catalyzed condensation greatly influenced the final particle shape. By changing the precursor or its concentration, the particle morphology was tuned to various shapes, including spheres, tubes, and rods of various dimensions. The synthetic procedures that gave rise to the specific particle morphologies were investigated and the mechanism responsible for shape control was postulated. The structure and functionality of these materials were characterized by field-emission scanning electron microscopy, transmission elec...
749 citations
TL;DR: A review of surface modification techniques for polymers with graft chains can be found in this paper, focusing on grafting methods as well as the structure and function of grafted surfaces.
622 citations
TL;DR: In this paper, organic modification with aminopropyl group of two MCM-41 materials having different pore sizes (obtained from trimethylalkylammonium surfactants with different chain sizes (16 and 12 carbon atoms)) has been carried out in order to control the delivery rate of ibuprofen from the siliceous matrix.
Abstract: Organic modification with aminopropyl group of two MCM-41 materials having different pore sizes (obtained from trimethylalkylammonium surfactants with different chain sizes (16 and 12 carbon atoms)) has been carried out in order to control the delivery rate of ibuprofen from the siliceous matrix. This functionalization was performed by two different methods: the as-synthesized MCM-41 sample was treated with aminopropyltrimethoxysilane (method a), and the MCM-41 was first calcined and then funtionalized by reaction with aminopropyltrimethoxysilane (method b). The amount of ibuprofen adsorbed from hexane solution is lower for the C12 derived materials. A slower delivery rate has been observed for method b, whereas a minor influence of the pore size on the delivery rate has been found.
608 citations
TL;DR: In this article, multi-walled carbon nanotubes (MWCNTs) produced by arc-discharge method were treated with oxidising inorganic acids, which led to a reduced agglomeration.
565 citations
TL;DR: It is argued that stable dispersions of SWNTs with octadecylamine in tetrahydrofuran (THF) originate from the physisorption and organization of ODA along the SWNT sidewalls in addition to the originally proposed zwitterion model.
Abstract: Substantial separation of single-wall carbon nanotubes (SWNTs) according to type (metallic versus semiconducting) has been achieved for HiPco and laser-ablated SWNTs. We presently argue that stable dispersions of SWNTs with octadecylamine (ODA) in tetrahydrofuran (THF) originate from the physisorption and organization of ODA along the SWNT sidewalls in addition to the originally proposed zwitterion model. Furthermore, the reported affinity of amine groups for semiconducting SWNTs, as opposed to their metallic counterparts, contributes additional stability to the physisorbed ODA. This provides a venue for the selective precipitation of metallic SWNTs upon increasing dispersion concentration, as indicated by Raman investigations.
564 citations
TL;DR: This review looks at the efforts that are being made to modify the surface of poly(dimethylsiloxane) (PDMS) microchannels, in order to enhance applicability in the field of microfluidics.
Abstract: This review looks at the efforts that are being made to modify the surface of poly(dimethylsiloxane) (PDMS) microchannels, in order to enhance applicability in the field of microfluidics. Many surface modifications of PDMS have been performed for electrophoretic separations, but new modifications are being done for emerging applications such as heterogeneous immunoassays and cell-based bioassays. These new modification techniques are powerful because they impart biospecificity to the microchannel surfaces and reduce protein adsorption. Most of these applications require the use of aqueous or polar solvents, which makes surface modification a very important topic.
553 citations
TL;DR: Gold nanoparticles were selectively attached to chemically functionalized surface sites on nitrogen-doped carbon (CNx) nanotubes by electrostatic interaction between carboxyl groups on the chemically oxidized nanotube surface and polyelectrolyte chains as discussed by the authors.
Abstract: Gold nanoparticles were selectively attached to chemically functionalized surface sites on nitrogen-doped carbon (CNx) nanotubes. A cationic polyelectrolyte was adsorbed on the surface of the nanotubes by electrostatic interaction between carboxyl groups on the chemically oxidized nanotube surface and polyelectrolyte chains. Negatively charged 10 nm gold nanoparticles from a gold colloid suspension were subsequently anchored to the surface of the nanotubes through the electrostatic interaction between the polyelectrolyte and the nanoparticles. This approach provides an efficient method to attach other nanostructures to carbon nanotubes and can be used as an illustrative detection of the functional groups on carbon nanotube surfaces.
522 citations
TL;DR: Significantly more neurofilament positive staining was found on the coated electrode which indicated that the coatings had established strong connections with the neuronal structure in vivo.
506 citations
TL;DR: The ability to modify the surface of carbon nanotubes is of crucial importance for their utilization in different applications as discussed by the authors, and in this paper we report on the chemical modification of multi-w...
Abstract: The ability to modify the surface of carbon nanotubes is of crucial importance for their utilization in different applications. In the present paper we report on the chemical modification of multiw...
TL;DR: Single-walled carbon nanotubes were functionalized along their sidewalls with phenol groups using the 1,3-dipolar cycloaddition reaction, leading to the production of high molecular weight polymers with relatively large polydispersities.
Abstract: Single-walled carbon nanotubes were functionalized along their sidewalls with phenol groups using the 1,3-dipolar cycloaddition reaction. These phenols could be further derivatized with 2-bromoisobutyryl bromide, resulting in the attachment of atom transfer radical polymerization initiators to the sidewalls of the nanotubes. These initiators were found to be active in the polymerization of methyl methacrylate and tert-butyl acrylate from the surface of the nanotubes. However, the polymerizations were not controlled, leading to the production of high molecular weight polymers with relatively large polydispersities. The resulting polymerized nanotubes were analyzed by IR, Raman spectroscopy, DSC, TEM, and AFM. The nanotubes functionalized with poly(methyl methacrylate) were found to be insoluble, while those functionalized with poly(tert-butyl acrylate) were soluble in a variety of organic solvents. The tert-butyl groups of these appended polymers could also be removed to produce nanotubes functionalized wi...
TL;DR: Electrostatic layer-by-layer (LbL) self-assembly has shown broad biomedical applications in thin film coating, micropatterning, nanobioreactors, artificial cells, and drug delivery systems.
Abstract: The introduction of electrostatic layer-by-layer (LbL) self-assembly has shown broad biomedical applications in thin film coating, micropatterning, nanobioreactors, artificial cells, and drug delivery systems. Multiple assembly polyelectrolytes and proteins are based on electrostatic interaction between oppositely charged layers. The film architecture is precisely designed and can be controlled to 1-nm precision with a range from 5 to 1000 nm. Thin films can be deposited on any surface including many widely used biomaterials. Microencapsulation of micro/nanotemplates with multilayers enabled cell surface modification, controlled drug release, hollow shell formation, and nanobioreactors. Both in vitro and in vivo studies indicate potential applications in biology, pharmaceutics, medicine, and other biomedical areas.
TL;DR: In this paper, surface modification of rough, high-surface area, nanocrystalline titania thin-film photocatalysts was performed by gold deposition via electron beam evaporation, with an attempt to enhance the decomposition reaction rate of industrial water pollutants.
TL;DR: The effects of different poly(ethylene glycol) (PEG) attachment strategies upon the adhesion of a Gram-negative bacteria (Pseudomonas sp.) was tested and showed that both substrates were chemically uniform after each surface modification step.
Abstract: The effects of different poly(ethylene glycol) (PEG) attachment strategies upon the adhesion of a Gram-negative bacteria (Pseudomonas sp) was tested PEG was covalently immobilized, at the lower critical solution temperature of PEG, to a layer of branched poly(ethylenimine) (PEI) PEI was both physically adsorbed to a stainless-steel (SS) substrate and covalently immobilized to a carboxylated poly(ethylene terephthalate) (PET−COOH) surface On both substrates, the PEI and PEG grafting conditions were optimized so that the levels of surface coverage after each step were maximized and were the same on both substrates, as judged by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS) Also, ToF-SIMS imaging showed that both substrates were chemically uniform after each surface modification step Thus, the two surfaces differ only in the mode of attachment of PEI to the substrate In bacterial adhesion experiments, the optimal SS−PEG surface was not capable of reduci
TL;DR: In this paper, a commercially available activated carbon was modified with 1.0 M citric acid to improve copper ion adsorption from aqueous solutions and the results showed that the surface modification reduced the specific surface area by 34% and point of zero charge (pHpzc) of the carbon by 0.5 units.
TL;DR: The effect of oxidation on modification of single wall carbon nanotubes (SWCNTs) through successive purification steps has been studied in this paper, where the existence of functional groups in the raw SWCNT material and their modification and almost complete removal after the final annealing step was studied.
TL;DR: In this paper, the preparation and characterization of highly dispersed metal nanoparticles in mesoporous silica SBA-15 is reported, where organosilane is used to generate a monolayer of charged groups on the pore surface.
Abstract: The preparation and characterization of highly dispersed metal nanoparticles in mesoporous silica SBA-15 are reported. The functionalization with organosilane to generate a monolayer of charged groups on the pore surface facilitates uniform distribution of ion-exchanged metal precursors in the channels of SBA-15, which, upon reduction, results in highly dispersed metal nanoparticles supported in SBA-15. Under mild reduction conditions, the surface functionality remains and so allows further metal incorporation cycles to achieve higher metal loading. After reduction in hydrogen flow, disk-shaped Pt nanoparticles in Pt/SBA-15 and spherical Au nanoparticles in Au/SBA-15 have been characterized in the channels of SBA-15 by PXRD, XAS, and TEM. Secondary Pt incorporation in Au/SBA-15 produces coexisting small Pt nanoparticles with large Au nanoparticles in the host channels. This preparation method is capable of template synthesis of various metal nanostructures with controlled morphology and composition inside...
TL;DR: The correlations suggest the decrease in spin-orbital couplings and surface anisotropy of magnetic nanoparticles due to the surface coordination, which clearly shows the dependence on the size of nanoparticles.
Abstract: To understand the influence of surface interactions upon the magnetic properties of magnetic nanoparticles, the surface of manganese ferrite, MnFe(2)O(4), nanoparticles have been systematically modified with a series of para-substituted benzoic acid ligands (HOOC-C(6)H(4)-R; R = H, CH(3), Cl, NO(2), OH) and substituted benzene ligands (Y-C(6)H(5), Y = COOH, SH, NH(2), OH, SO(3)H). The coercivity of magnetic nanoparticles decreases up to almost 50% upon the coordination of the ligands on the nanoparticle surface, whereas the saturation magnetization has increased. The percentage coercivity decrease of the modified nanoparticles with respect to the native nanoparticles strongly correlates with the crystal field splitting energy (CFSE) Delta evoked by the coordination ligands. The ligand inducing largest CFSE results in the strongest effect on the coercivity of magnetic nanoparticles. The change in magnetic properties of nanoparticles also correlates with the specific coordinating functional group bound onto the nanoparticle surface. The correlations suggest the decrease in spin-orbital couplings and surface anisotropy of magnetic nanoparticles due to the surface coordination. Such surface effects clearly show the dependence on the size of nanoparticles.
TL;DR: The stability of APS in ethanol and that of mercaptopropyl-grafted silica (MPS) in water have been briefly considered and discussed with respect to practical applications of silica-based organic-inorganic hybrids, e.g., in separation science or in the field of electrochemical sensors.
TL;DR: In this paper, a surface treatment method, using a dielectric barrier discharge (DBD) of random filamentary type, was discussed. And the effects of air-DBD treatment on the surfaces of various polymer films and polymer-based fabrics were studied.
Abstract: In this paper, we report and discuss a surface treatment method, using a dielectric barrier discharge (DBD) of random filamentary type. This offers a convenient, reliable and economic alternative for the controlled modification (so far, largely dependent on surface oxidation) of various categories of material surfaces. Remarkably uniform treatment and markedly stable modified surface properties result over the entire area of the test surfaces exposed to the discharge even at transit speeds simulating those associated with continuous on-line processing. The effects of air-DBD treatment on the surfaces of various polymer films and polymer-based fabrics were studied. The dielectric barrier concerned has been characterized in terms of the energy deposited by the discharge at the processing electrodes and the resultant modifications of the surface properties of the treated samples were investigated using x-ray photoelectron spectroscopy, contact angle/wickability measurement and scanning electron microscopy. The influence of the surface treatment parameters, such as the energy deposited by the discharge, the inter-electrode gap and the treatment time were examined and related to the post-treatment surface characteristics of the materials processed. Relationships between the processing parameters and the properties of the DBD treated samples were thus established. Of the three process variables investigated, the duration of the treatment was found to have a more significant effect on the surface modifications found than did the discharge energy or the inter-electrode gap. Very short air-DBD treatments (fractions of a second in duration) markedly and uniformly modified the surface characteristics for all the materials treated, to the effect that wettability, wickability and the level of oxidation of the surface appear to be increased strongly within the first 0.1–0.2 s of treatment. Any subsequent surface modification following longer treatment (>1.0 s) was less important. The modification of the surface properties also appears to be stable with time, as minimal recovery of the surface properties is shown on ageing post-treatment. The behaviour of the woven textile polymers examined was found to be very similar, under DBD treatment, to that of thin-film variants based on the same polymers. For the porous textile fabrics examined, rapid and efficient treatment (fractions of a second) on both sides of the treated samples was found to be ensured. Thereby the system regime used offers the attractive prospect of controlling the modification of non-compact materials of various texture, porosity, etc. The DBD described system thus provides a chemically mild and mechanically non-destructive means of altering surface properties targeting improved surface characteristics and potentially better application performance.
TL;DR: The results are consistent with a diffusion controlled mechanism suggesting that DNA molecules bind irreversibly with the surface upon immobilization, and it is demonstrated directly that the segments of DNA molecules could move along the surface if the sample is imaged in aqueous solution without drying of the sample.
TL;DR: The results indicate that the surface composition of colloidal drug carriers affects their biodistribution in the eye and this surface modification approach can be used as a targeting strategy in ocular drug delivery.
01 Aug 2003-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, a quantitative characterization of the thin films with respect to the type and density of available groups at the surfaces is presented, and some possible applications of plasma-modified polymers are also discussed.
Abstract: Polymeric materials can be used in many application areas due to their mechanical (e.g. elastic) characteristics, chemical stability, and their light weight, as well as for their many design possibilities. Even in the fields of medicine and biotechnology many products are completely or partly made of polymers. In contact with biological systems, compatibility of these materials is not always given. To fulfill the requirements for medical applications, the surfaces have to be modified. Plasma techniques are demonstrated as an appropriate tool for the generation of the demanded surface properties. Experimental data are given for surface modification by plasma polymerization, with retention of the functional groups of the monomers used. Qualitative and quantitative characterization of the thin films with respect to the type and density of available groups at the surfaces is presented. Some possible applications of plasma-modified polymers are also discussed.
TL;DR: In this paper, the composition and properties of surface-modified Ti were investigated by a number of surface sensitive techniques: XPS, ATR-IR, atomic force microscopy and AFM force-separation curves.
TL;DR: The results showed that polyelectrolyte multilayered films neither induce cytotoxic effects nor alter the phenotype of the endothelial cells, thereby constituting an excellent material for endothelial cell seeding.
TL;DR: In this article, OA-modified SiO2 nanoparticles are shown to be able to cover and dispersion in mineral oil by oleic acid (OA) concentration.
TL;DR: In this paper, a number of monomers with a variety of functional groups have been successfully grafted from the surface of selected substrates, and the grafting efficiency determined using X-ray photoemission spectroscopy.
Abstract: Photografting has been used for the surface modification of a wide range of commercial commodity polymers such as poly- styrene, poly(methyl methacrylate), poly(dimethyl siloxane), polycarbonate, Parylene C, polypropylene, cyclic olefin copolymer, and hydrogenated polystyrene that are useful substrate materials for the fabrication of microfluidic chips. Since the chain propagation is initiated after UV light-activated abstraction of a hydrogen atom from the surface of channels within the materials, their permeability for UV light was tested and polyolefins were found to be the best candidates. A number of monomers with a variety of functional groups such as perfluorinated, hydrophobic, hydrophilic, reactive, acidic, basic, and zwitterionic have been successfully grafted from the surface of selected substrates, and the grafting efficiency determined using X-ray photoemission spectroscopy. Layered surface structures were prepared by consecutive grafting of different monomers. Our approach also enables photolithographic patterning of surfaces and specific functionalization of confined areas within the microchannel.
TL;DR: The main focus is on the improved electrophoretic separation by reducing analyte‐wall interactions and manipulation of electroosmosis in microchip electrophoresis.
Abstract: Different approaches and techniques for surface modification of microfluidic devices applied for microchip electrophoresis are reviewed. The main focus is on the improved electrophoretic separation by reducing analyte-wall interactions and manipulation of electroosmosis. Approaches and methods for permanent and dynamic surface modification of microfluidic devices, manufactured from glass, quartz and also different polymeric substrates, are described.
TL;DR: The high degree of resistance of the PEGylated surface to non-specific adsorption makes peptide-modified PLL-g-PEG a useful candidate for the surface modification of biomedical devices such as implants that are capable of eliciting specific interactions with integrin-type cell receptors even in the presence of full blood plasma.