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Showing papers on "Surface modification published in 2002"


Journal ArticleDOI
TL;DR: Through chemical functionalization of single-walled carbon nanotubes, the prerequisites for possible applications of such nanostructures are established and the current state of the literature is presented in this Minireview.
Abstract: Through chemical functionalization of single-walled carbon nanotubes, the prerequisites for possible applications of such nanostructures are established. The derivatized tubes differ from the crude materials in their good solubility, which enables both a more extensive characterization and subsequent chemical reactivity. Current derivatization methods include defect and covalent sidewall functionalization, as well as noncovalent exo- and endohedral functionalization. In this way, for example, a range of nanotubes can be prepared: with sidewall substituents, wrapped with polymers, or with guest molecules included. The current state of the literature is presented in this Minireview.

1,944 citations


Journal ArticleDOI
15 Oct 2002
TL;DR: The results reveal that when exposed to UV, the PDMS macromolecules in the surface region of Sylgard-184 undergo chain scission, involving both the main chain backbone and the side groups, and form a network whose wetting properties are similar to those of a UV-modified model PDMS.
Abstract: We report on the surface modification of Sylgard-184 poly(dimethyl siloxane) (PDMS) networks by ultraviolet (UV) radiation and ultraviolet/ozone (UVO) treatment. The effects of the UV light wavelength and ambient conditions on the surface properties of Sylgard-184 are probed using a battery of experimental probes, including static contact angle measurements, Fourier transform infrared spectroscopy, near-edge X-ray absorption fine structure, and X-ray reflectivity. Our results reveal that when exposed to UV, the PDMS macromolecules in the surface region of Sylgard-184 undergo chain scission, involving both the main chain backbone and the side groups. The radicals formed during this process recombine and form a network whose wetting properties are similar to those of a UV-modified model PDMS. In contrast to the UV radiation, the UVO treatment causes very significant changes in the surface and near-surface structure of Sylgard-184. Specifically, the molecular oxygen and ozone created during the UVO process interact with the UV-modified specimen. As a result of these interactions, the surface of the sample contains a large number of hydrophilic (mainly -OH) groups. In addition, the material density within the first approximately 5 nm reaches about 50% of that of pure silica. A major conclusion that can be drawn from the results and analysis described in this work is that the presence of the silica fillers in Sylgard-184 does not alter the surface properties of the UVO- and UV-modified Sylgard-184.

736 citations


Journal ArticleDOI
TL;DR: In this article, surface modification of nanocrystalline metal oxide particles with enediol ligands was found to result in altered optical properties of nanoparticles, and the surface modification results in a red shift of the semiconductor absorption compared to unmodified nanocrystites.
Abstract: Surface modification of nanocrystalline metal oxide particles with enediol ligands was found to result in altered optical properties of nanoparticles. The surface modification results in a red shift of the semiconductor absorption compared to unmodified nanocrystallites. The optical shift is correlated to the dipole moment of the Ti−ligand complexes at the particle surface and decreases with the ligand size. The binding was found to be exclusively characteristic of colloids in the nanocrystalline domain(<20 nm). X-ray near-edge structure measurements at Ti K edge indicate that in this size domain the surface Ti atoms adjust their coordination environment to form undercoordinated sites. These five-coordinated defect sites are the source of novel enhanced and selective reactivity of the nanoparticle toward bidentate ligand binding as observed using IR spectroscopy. Enediol ligands have the optimal geometry for chelating surface Ti atoms, resulting in a five-membered ring coordination complex and restored si...

680 citations


Journal ArticleDOI
TL;DR: In this paper, the structure of nanofiltration (NF) and reverse osmosis (RO) membranes modified using graft polymerization of acrylic (AA) monomers was visualized and analyzed using attenuated total reflection-Fourier transform infrared spectroscopy, atomic force microscopy and transmission electron microscopy.

462 citations


Journal ArticleDOI
TL;DR: The endothelial cell culture proved that the cytocompatibility of the aminolyzed PCL was improved slightly regardless of the NH(2) amount on the surface, and the cell attachment and proliferation ratios were obviously improved and the cells showed a similar morphology to those on tissue culture polystyrene.

447 citations


Journal ArticleDOI
TL;DR: The combination of high surface area, robust immobilization and inherent nanotube electrochemical properties is of promising application in bioelectrochemistry.
Abstract: Metalloproteins and enzymes can be immobilized on SWNTs of different surface chemistry. The combination of high surface area, robust immobilization and inherent nanotube electrochemical properties is of promising application in bioelectrochemistry.

409 citations


Journal ArticleDOI
TL;DR: A one-step procedure to covalently link polymers to the surface of PDMS microchannels by ultraviolet graft polymerization is demonstrated and it is shown that by using the appropriate monomer, it should be possible to use UV grafting to impart a variety of surface properties toPDMS microfluidics devices.
Abstract: Poly(dimethylsiloxane) (PDMS)-based microfluidic devices are increasing in popularity due to their ease of fabrication and low costs. Despite this, there is a tremendous need for strategies to rapidly and easily tailor the surface properties of these devices. We demonstrate a one-step procedure to covalently link polymers to the surface of PDMS microchannels by ultraviolet graft polymerization. Acrylic acid, acrylamide, dimethylacrylamide, 2-hydroxylethyl acrylate, and poly(ethylene glycol)monomethoxyl acrylate were grafted onto PDMS to yield hydrophilic surfaces. Water droplets possessed contact angles as low as 45° on the grafted surfaces. Microchannels constructed from the grafted PDMS were readily filled with aqueous solutions in contrast to devices composed of native PDMS. The grafted surfaces also displayed a substantially reduced adsorption of two test peptides compared to that of oxidized PDMS. Microchannels with grafted surfaces exhibited electroosmotic mobilities intermediate to those displayed ...

406 citations


Journal ArticleDOI
TL;DR: The physical chemistry of solution silicate species and surfactants in the synthesis of mesoporous silicas is reviewed and controls in surfactant packing and liquid crystalline phase transformation can lead to various tailored synthesis strategies.
Abstract: Micelle-templated mesoporous silica materials are rapidly becoming important in many fields of chemistry for hosting reactants or catalysts in confined space. Fine control of the pore size, wall structure, surface functionalization, defects, and morphology is needed for fine-tuning the pores as nanoreactors. We review the physical chemistry of solution silicate species and surfactants in the synthesis of mesoporous silicas. Controls in surfactant packing and liquid crystalline phase transformation can lead to various tailored synthesis strategies. Postsynthesis treatments further make more stable mesoporous materials.

395 citations


Journal ArticleDOI
TL;DR: The results suggest that anhydrous ammonia plasma treatment enhances the cell affinity of porous scaffolds and is suitable for human skin fibroblast cell growth.
Abstract: The fabrication and surface modification of a po- rous cell scaffold are very important in tissue engineering. Of most concern are high-density cell seeding, nutrient and oxygen supply, and cell affinity. In the present study, poly(L- lactic acid) and poly(L-lactic-co-glycolic acid) (70/30) cell scaffolds with different pore structures were fabricated. An improved method based on Archimedes' Principle for mea- suring the porosity of scaffolds, using a density bottle, was developed. Anhydrous ammonia plasma treatment was used to modify surface properties to improve the cell affinity of the scaffolds. The results show that hydrophilicity and surface energy were improved. The polar N-containing groups and positive charged groups also were incorporated into the sample surface. A low-temperature treatment was used to maintain the plasma-modified surface properties ef- fectively. It would do help to the further application of plasma treatment technique. Cell culture results showed that pores smaller than 160 m are suitable for human skin fibroblast cell growth. Cell seeding efficiency was main- tained at above 99%, which is better than the efficiency achieved with the common method of prewetting by etha- nol. The plasma-treatment method also helped to resolve the problem of cell loss during cell seeding, and the negative effects of the ethanol trace on cell culture were avoided. The results suggest that anhydrous ammonia plasma treatment enhances the cell affinity of porous scaffolds. Mass transport issues also have been considered. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 438-446, 2002

378 citations


Journal ArticleDOI
TL;DR: The first observation that after surface modification with carboxylate groups, the optical absorption of the first interband transition of as-treated water-soluble semiconducting SWNTs reversibly responds to the pH change in aqueous solutions is presented.
Abstract: There is great interest in using single-walled carbon nanotubes (SWNTs) as nanoscale probes and sensors in biological electronics and optical devices because the electronic and optical properties of SWNTs are extremely sensitive to the surrounding environments A well-controlled modification of SWNT surfaces may provide unique interfaces that are sensitive to the biological variables such as pH, glucose, various ions and proteins In this paper, we report a facile chemical routine to prepare water-soluble SWNTs that still retain their van Hove singularities after acid oxidative treatment The aqueous solutions (003−015 mg/mL) are stable for more than a month The solubility in water for as-treated SWNTs with surfaces modified by carboxylate groups provides us with a unique opportunity to reveal the relationship of the SWNT electronic and optical properties with pH Here we present the first observation that after surface modification with carboxylate groups, the optical absorption of the first interband

339 citations


Journal ArticleDOI
TL;DR: The surface modification with poly(vinylpyridine) via adsorption technique is suggested as a simple, effective and highly versatile method for the preparation of single, mixed, and multilayered assemblies of various nanoparticles on different substrates.
Abstract: Metal, metal oxide, and plastic surfaces were modified with poly(vinylpyridine) using adsorption, spin-coating, and dip-coating techniques and various metal, semiconductor, and dielectric nanoparticles were subsequently attached. Prior to the modification, the substrates were treated with glow discharge plasma for cleaning purposes and to introduce surface functional groups that are capable of interaction with the polymer. UV−vis absorption spectroscopy, atomic force, and electron scanning microscopies were used to characterize polymer layers and layers of immobilized nanoparticles. The surface modification with poly(vinylpyridine) via adsorption technique is suggested as a simple, effective, and highly versatile method for the preparation of single, mixed, and multilayered assemblies of various nanoparticles on different substrates.

Journal ArticleDOI
03 Mar 2002-Langmuir
TL;DR: In this article, the authors used X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) to evaluate the bioactivity of the modified Ti disks by incubating these disks in a physiological solution.
Abstract: Commercially pure titanium (cp Ti) is widely used in dental implantology. However, it is only passively integrated in bone and the resulting fixation in the bone, which is necessary for the function, is mainly mechanical in its nature. With the objective of increasing the chemical interaction between the implant and bone tissue, several phosphonic acids were synthesized and grafted onto titanium disks. The bare polished Ti disks (Ti P) and the grafting of three phosphonic acids (methylenediphosphonic acid (MDP), propane-1,1,3,3-tetraphosphonic acid (PTP), and ethane-1,1,2-triphosphonic acid (ETP)) on these disks were characterized with X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). These surface analytical techniques provided strong indications of the formation of a chemical link between the Ti implant and the phosphonic acid molecule. The bioactivity of the modified Ti disks was evaluated by incubating these disks in a physiological solution (Hank's ...

Journal ArticleDOI
TL;DR: Findings indicate that poly(alpha-hydroxy ester) materials can be readily mineralized using a biomimetic process, and that the impetus for mineral nucleation in this system appears more complicated than the simple electrostatic interactions proposed in previous biomineralization theory.
Abstract: Mineralization in biological systems is a widespread, yet incompletely understood phenomenon involving complex interactions at the biomacromolecule−mineral nucleus interface. This study was aimed at understanding and controlling mineral formation in a poly(α-hydroxy ester) model system, to gain insight into biological mineralization processes and to develop biomaterials for orthopaedic tissue regeneration. We specifically hypothesized that providing a high surface density of anionic functional groups would enhance nucleation and growth of bonelike mineral following exposure to simulated body fluids (SBF). Polymer surface functionalization was achieved via hydrolysis of 85:15 poly(lactide-co-glycolide) (PLG) films. This treatment led to an increase in surface carboxylic acid and hydroxyl groups, resulting in a substantial increase in polymer surface energy from 42 to 49 dynes/cm2. Treated polymers exhibited a 3-fold increase in heterogeneous mineral grown and growth of a continuous mineral film on the poly...

Journal ArticleDOI
TL;DR: In this article, the synthesis of unusually thick poly(2-hydroxyethyl methacrylate) (PHEMA) films on gold surfaces by surface-initiated atom transfer radical polymerization (ATRP) was reported.
Abstract: We report the synthesis of unusually thick poly(2-hydroxyethyl methacrylate) (PHEMA) films on gold surfaces by surface-initiated atom transfer radical polymerization (ATRP). Polymerization from the surface occurs rapidly at room temperature in aqueous media, resulting in the formation of 700 nm thick polymer films in just 12 h. Control experiments using neat monomer and catalyst (no water) yield films with thicknesses of only 6 nm, demonstrating the accelerating effect of water on surface-initiated ATRP. Kinetic studies reveal a nearly linear increase in thickness with reaction time, indicating that chain growth from the surface is a controlled process with some “living” character. A second block can be grown from dormant initiators at the end of PHEMA chains, providing further evidence of “living” chain ends. Derivatization of the hydroxyl groups of grafted PHEMA with a variety of molecules allows dense functionalization of these films. Reflectance FTIR spectroscopy shows a virtually quantitative yield i...

Journal ArticleDOI
11 Jan 2002-Langmuir
TL;DR: In this article, the authors evaluated the influence of substrate surface characteristics on protein adsorption processes and concluded that the supramolecular organization of the adsorbed layer is controlled both by surface chemistry and topography.
Abstract: To evaluate the influence of substratum surface characteristics on protein adsorption processes, we have investigated the adsorption (adsorbed amount, supramolecular organization) of collagen on model substrata exhibiting controlled topography and surface chemistry. Substrata were prepared in two steps: (i) gold deposition onto silicon wafers (smooth substrata) and onto a support with nanoscale protrusions created by colloidal lithography (rough substrata); (ii) functionalization with CH3 (hydrophobic) and OH (hydrophilic) groups, using alkanethiol self-assembly. Atomic force microscopy (AFM) images were recorded under water, prior to and after collagen adsorption, and the images were analyzed quantitatively using two independent approaches. On smooth substrata, collagen formed a similar to6 nm thick, homogeneous layer with low roughness on hydrophilic surfaces, and a similar to20 nm thick layer exhibiting elongated aggregated structures on hydrophobic surfaces. Film thickness measurements (AFM) together with X-ray photoelectron spectroscopy (XPS) revealed larger adsorbed amounts on hydrophobic surfaces compared to hydrophilic ones. On rough substrata, the adsorbed amounts were similar to those found on smooth substrata; however, the collagen molecules no longer formed aggregated structures on the hydrophobic surfaces. It is concluded that while the adsorbed amount is only affected by the surface chemistry, the supramolecular organization of the adsorbed layer is controlled both by surface chemistry and topography. The approach presented here will have great value in biophysics for investigating bioadsorption and bioadhesion processes on substrata of defined surface properties.

Journal ArticleDOI
TL;DR: In this article, carbon nanotubes were solubilized via functionalization with poly(propionylethylenimine-co-ethylenimines) and the diimide-activated amidation reaction for the functionalization was found to be signific...
Abstract: Carbon nanotubes were solubilized via functionalization with poly(propionylethylenimine-co-ethylenimine). The diimide-activated amidation reaction for the functionalization was found to be signific...

Journal ArticleDOI
18 Jan 2002-Langmuir
TL;DR: In this article, a new scheme for attachment of functionalized organic molecules to polycrystalline diamond films was proposed, where ultraviolet light was used to cause a local reaction between a hydrogen-terminated diamond surface and organic molecules present as a thin overlayer liquid film.
Abstract: We report a new scheme for attachment of functionalized organic molecules to polycrystalline diamond films. In this scheme, ultraviolet light is used to cause a local reaction between a hydrogen-terminated diamond surface and organic molecules present as a thin overlayer liquid film. Comparison of functionalized alkenes and alkanes shows that alkenes attach more efficiently. By attaching organic molecules with suitable protecting groups and then deprotecting after attachment to the surface, it is possible to prepare diamond surfaces terminated with carboxylic acid groups or with primary amine groups. These functional groups may serve as an attractive starting point for further chemical modification of diamond surfaces.

Journal ArticleDOI
TL;DR: In this article, a mixture of polyvinylidene fluoride (PVDF) and a free-radically synthesized amphiphilic comb polymer having a methacrylate backbone and poly(ethylene oxide) side chains was used to obtain a membrane with a surface coverage of up to 50 vol.

Journal ArticleDOI
TL;DR: In this paper, a dispersion of HiPco single-walled carbon nanotubes in methanol has been subjected to ozonolysis at −78 °C, followed by treatment with various reagents, in independent runs, to generate a higher proportion of carboxylic acid/ester, ketone/aldhehyde, and alcohol groups, respectively, on the nanotube surface.
Abstract: A dispersion of raw HiPco single-walled carbon nanotubes in methanol has been subjected to ozonolysis at −78 °C, followed by treatment with various reagents, in independent runs, to generate a higher proportion of carboxylic acid/ester, ketone/aldhehyde, and alcohol groups, respectively, on the nanotube surface. This protocol has been found to purify nanotubes by removing amorphous carbon and metal impurities. More importantly, as had been theoretically predicted, the reaction sequence has been found to ozonize (and hence, oxygenate) the sidewalls of these nanotubes, thereby broadening the chemical processability and reactivity of these nanomaterials. The derivatized materials have been characterized by means of SEM and TEM, and spectroscopically, using Raman, UV−vis−near-IR, and X-ray photoelectron spectroscopies.

Journal ArticleDOI
TL;DR: In this article, a novel chemical functionalization method for multiwalled carbon nanotubes (MWNTs), through an oxidation and silanization process, is presented, which allows us to have different organo-functional groups attached to the MWNTs, which improves their chemical compatibility with specific polymers for producing new nanotube-based composites.
Abstract: A novel chemical functionalization method for multiwalled carbon nanotubes (MWNTs), through an oxidation and silanization process, is presented. The method allows us to have different organo-functional groups attached to the MWNTs, which improves their chemical compatibility with specific polymers for producing new nanotube-based composites. The corresponding moieties were characterized by infrared, Raman and energy dispersion spectroscopies.


Journal ArticleDOI
TL;DR: The results suggested that the pre-deposition of HA onto these functionalized SAM surfaces might be an effective and fast way to prepare biomimetic apatite coatings on surgical implants.

Journal ArticleDOI
TL;DR: In this article, the surface energy of the hole collector electrode of photovoltaic devices is modified by deposition of self-assembled monolayers to favor segregation of hole-accepting component of the blend to the substrate.
Abstract: Surface treatment and solvent evaporation control are used to promote vertical segregation in polyfluorene-blend thin films. This surface-mediated control of the compositional structure in the direction normal to the plane of the film has important implications for optimizing charge transport in solution-processed conjugated polymer-blend optoelectronics. Here, the surface energy of the hole-collector electrode of photovoltaic devices is modified by deposition of self-assembled monolayers to favor segregation of the hole-accepting component of the blend to the substrate. Devices fabricated with intentionally vertically segregated blends showed external quantum efficiencies of up to 14%, which is ten times higher than that of devices fabricated without surface modification.

Journal ArticleDOI
TL;DR: The endothelial cell culture proved that the PCL membrane slightly modified with suitable amount of PMAA or gelatin had better cytocompatibility than control PCL orPCL membrane heavily modified with PMAAor gelatin.

Journal ArticleDOI
TL;DR: In this article, the morphology and structure of the coating layer have been characterized with scanning electron microscope and high-revolution transmission electron microscope (HRTEM) and it is found that the coating is amorphous and rather compact.

Journal ArticleDOI
30 Jul 2002-Langmuir
TL;DR: In this paper, surface modification of colloidal gold with 11-mercaptoundecanoic acid or 16mercaptohexadecanoic acid was performed in the absence or in the presence of the nonionic surfactant polyoxyethylene (20) sorbitan monolaurate (Tween 20).
Abstract: Surface modification of colloidal gold with 11-mercaptoundecanoic acid or 16-mercaptohexadecanoic acid was performed in the absence or in the presence of the nonionic surfactant polyoxyethylene (20) sorbitan monolaurate (Tween 20). The stability of the colloidal systems was assessed with optical absorption spectroscopy. The surface-modified nanoparticles were stable only within a narrow range of intermediate pH values when chemisorption of alkanethiols was performed in the absence of Tween 20. This was explained in terms of partial ionization of the surface carboxylic groups and charge neutralization at high pH values by counterions present in the buffer solutions. Formation of a physisorbed monolayer of Tween 20 onto the nanoparticles prior to chemisorption of alkanethiols resulted in surface-modified colloidal gold that was stable over a broader range of pH values. Parallel experiments demonstrated that self-assembled monolayers could form on flat substrates in the presence of Tween 20. Therefore, possi...

Journal ArticleDOI
26 Jul 2002-Langmuir
TL;DR: Proteins were precisely patterned on 2D sensor surfaces using photolithography and chemical selectivity to understand the interaction of proteins with SAMs at the molecular level and PEGs immobilized on bare silicon substrates showed resistance to protein adsorption.
Abstract: Proteins were precisely patterned on 2D sensor surfaces using photolithography and chemical selectivity. Microarrays of gold squares were fabricated on silicon substrates. The gold regions were modified with mixed COOH-terminated self-assembled monolayers (SAMs) to have a high affinity for the desired proteins or peptides. The silicon regions were modified with polyethylene glycol (PEG) by silanization to provide a high resistivity to protein adsorption. Protein surface coverage was visualized by fluorescence microscopy and atomic force microscopy (AFM). AFM was also used for studying protein morphology to understand the interaction of proteins with SAMs at the molecular level. Proteins and peptides immobilized on SAMs were examined by Fourier transform infrared (FTIR) spectroscopy. Contact angle measurements for surface wettability were conducted to confirm the success of the surface modification reactions. Protein resistance by the PEGs immobilized on bare silicon substrates and on the silicon regions o...

Journal ArticleDOI
TL;DR: The surface chemical characteristics of activated carbon treated by ozone and alkaline are determined in terms of surface functional groups and surface acidity.

Journal ArticleDOI
TL;DR: The thermal reaction of undecylenic acid with a hydrogen-terminated porous silicon surface takes place at 95°C to yield an organic monolayer covalently attached to the surface through Si-C bonds.
Abstract: The thermal reaction of undecylenic acid with a hydrogen-terminated porous silicon surface takes place at 95°C to yield an organic monolayer covalently attached to the surface through Si-C bonds. The acid terminal group remains intact and is not affected by the chemical process. Under the same conditions, alcohols break the Si-Si back bonds of the PSi matrix. In contrast, the acid function does not react with either the Si-H or the Si-Si bonds of the PSi surface and the reaction takes place at the terminal C-C double bond of the molecule. When the reaction was carried out with decanoic acid, under the same conditions, the reaction was not complete. The functionalized surfaces were characterized using transmission infrared and X-ray photoelectron spectroscopies. The effect of the chemical process on the photoluminescence has been studied, and the stability against corrosion in 100% humidity was verified using chemography. We have demonstrated that the derivatized surface with undecylenic acid can be activated by a simple chemical route using N-hydroxysuccimide in the presence of N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide hydrochloride.

Journal ArticleDOI
TL;DR: The surface morphology, crystalline structure, and electrochemical performance of the modified cathode material were characterized and compared with that of pristine LiCoO2 in this article, and it was found that surface modification can improve the structural stability of LiO2 without decreasing its available specific capacity.
Abstract: Commercial cathode material LiCoO2 was modified by coating its surface with a thin layer of amorphous magnesium oxide (MgO). The surface morphology, crystalline structure, and electrochemical performance of the modified cathode material were characterized and compared with that of pristine LiCoO2. It is found that surface modification can improve the structural stability of LiCoO2 without decreasing its available specific capacity. Specific capacities of 145, 175, and 210 mAh/g were obtained in test cells composed of MgO-coated LiCoO2 cathode material when charged to 4.3, 4.5, and 4.7 V (Li+/Li), respectively. This improvement is attributed to the pillaring effect of the Mg2+ ions in the interslab space of the lattice and the protective effect of the MgO film against the escape of Co4+ ions from the bulk of LiCoO2 particles. (C) 2002 The Electrochemical Society.