Showing papers on "Surface modification published in 2012"

Synthesis of silica nanoparticles by sol-gel: size-dependent properties, surface modification, and applications in silica-polymer nanocomposites — a review

Abstract: Application of silica nanoparticles as fillers in the preparation of nanocomposite of polymers has drawnmuch attention, due to the increased demand for new materials with improved thermal, mechanical, physical, and chemical properties. Recent developments in the synthesis of monodispersed, narrow-size distribution of nanoparticles by sol-gel method provide significant boost to development of silica-polymer nanocomposites. This paper is written by emphasizing on the synthesis of silica nanoparticles, characterization on size-dependent properties, and surface modification for the preparation of homogeneous nanocomposites, generally by sol-gel technique. The effect of nanosilica on the properties of various types of silica-polymer composites is also summarized.

Surface modification using phosphonic acids and esters.

Abstract: Cleḿence Queffeĺec,† Marc Petit,†,‡ Pascal Janvier,† D. Andrew Knight, and Bruno Bujoli*,† †LUNAM Universite,́ CNRS, UMR 6230, Chimie Et Interdisciplinarite:́ Synthes̀e Analyse Modeĺisation (CEISAM), UFR Sciences et Techniques, 2, rue de la Houssinier̀e, BP 92208, 44322 NANTES Cedex 3, France ‡Universite ́ Pierre et Marie Curie (UPMC), CNRS, UMR7201, Institut Parisien De Chimie Molećulaire (IPCM), 4 place Jussieu, 75252 Paris Cedex 05, France Chemistry Department, Florida Institute of Technology, 150 West University Boulevard, Melbourne, Florida 32901, United States

Synthesis and characterization of magnetite nanoparticles via the chemical co-precipitation method

Abstract: Magnetite nanoparticles were synthesized via the chemical co-precipitation method using ammonium hydroxide as the precipitating agent. The size of the magnetite nanoparticles was carefully controlled by varying the reaction temperature and through the surface modification. Herein, the hexanoic acid and oleic acid were introduced as the coating agents during the initial crystallization phase of the magnetite. Their structure and morphology were characterized by the Fourier transform infrared spectroscopy (FTIR), the X-ray diffraction (XRD) and the field-emission scanning electron microscopy (FE-SEM). Moreover, the electrical and magnetic properties were studied by using a conductivity meter and a vibrating sample magnetometer (VSM), respectively. Both of the bare magnetite and the coated magnetite were of the cubic spinel structure and the spherical-shaped morphology. The reaction temperature and the surface modification critically affected the particle size, the electrical conductivity, and the magnetic properties of these particles. The particle size of the magnetite was increased through the surface modification and reaction temperature. In this study, the particle size of the magnetite nanoparticles was successfully controlled to be in the range of 10–40 nm, suitable for various biomedical applications. The electrical conductivity of the smallest particle size was 1.3 × 10−3 S/cm, within the semi-conductive materials range, which was higher than that of the largest particle by about 5 times. All of the magnetite nanoparticles showed the superparamagnetic behavior with high saturation magnetization. Furthermore, the highest magnetization was 58.72 emu/g obtained from the hexanoic acid coated magnetite nanoparticles.

Magnetically Driven Floating Foams for the Removal of Oil Contaminants from Water

Abstract: In this study, we present a novel composite material based on commercially available polyurethane foams functionalized with colloidal superparamagnetic iron oxide nanoparticles and submicrometer polytetrafluoroethylene particles, which can efficiently separate oil from water. Untreated foam surfaces are inherently hydrophobic and oleophobic, but they can be rendered water-repellent and oil-absorbing by a solvent-free, electrostatic polytetrafluoroethylene particle deposition technique. It was found that combined functionalization of the polytetrafluoroethylene-treated foam surfaces with colloidal iron oxide nanoparticles significantly increases the speed of oil absorption. Detailed microscopic and wettability studies reveal that the combined effects of the surface morphology and of the chemistry of the functionalized foams greatly affect the oil-absorption dynamics. In particular, nanoparticle capping molecules are found to play a major role in this mechanism. In addition to the water-repellent and oil-ab...

Synthesis and surface modification of uniform MFe2O4 (M = Fe, Mn, and Co) nanoparticles with tunable sizes and functionalities

Abstract: Cubic monodisperse MFe2O4 ferrite nanoparticles (M = Fe, Co, and Mn) with tunable sizes between 7 and 20 nm and a narrow size distribution have been achieved in a one step synthesis by thermal decomposition of Fe(III), Co (II), and Mn(II) oleates. These nanoparticles have been functionalized with dimercaptosuccinic acid (DMSA), 11-mercaptoundecanoic acid (MUA), and bis(carboxymethyl)(2-maleimidylethyl)ammonium 4-toluenesulfonate (MATS) to grant them aqueous stability and the possibility for further functionalization with different biomolecules. Their structural, magnetic, and colloidal properties have also been studied to determine their chemical and physical properties and the degree of stability under physiological conditions that will determine their future use in biomedical applications.

Functionality is Key: Recent Progress in the Surface Modification of Nanodiamond

Abstract: Nanoscale diamond has recently received considerable attention due to the various possible applications such as luminescence imaging, drug delivery, quantum engineering, surface coatings, seeding etc. For most of these fields a suitable surface termination and functionalization of the diamond materials are required. In this feature article we discuss recent achievements in the field of surface modification of nanoscale diamond including the establishment of a homogeneous initial surface termination, the covalent and non-covalent immobilization of different functional moieties as well as the subsequent grafting of larger (bio)molecules onto previously functionalized nanodiamond.

Oxygen radical functionalization of boron nitride nanosheets.

Abstract: The covalent chemical functionalization of exfoliated hexagonal boron–nitride nanosheets (BNNSs) is achieved by the solution-phase oxygen radical functionalization of boron atoms in the h-BN lattice. This involves a two-step procedure to initially covalently graft alkoxy groups to boron atoms and the subsequent hydrolytic defunctionalization of the groups to yield hydroxyl-functionalized BNNSs (OH-BNNSs). Characterization of the functionalized-BNNSs using HR-TEM, Raman, UV–vis, FTIR, NMR, and TGA was performed to investigate both the structure of the BNNSs and the covalent functionalization methodology. OH-BNNSs were used to prepare polymer nanocomposites and their mechanical properties analyzed. The influence of the functional groups grafted to the surface of the BNNSs is investigated by demonstrating the impact on mechanical properties of both noncovalent and covalent bonding at the interface between the nanofiller and polymer matrixes.

Recent advances in stealth coating of nanoparticle drug delivery systems

Abstract: Modifying surfaces of nanoparticles (NPs) with polyethylene glycol (PEG), the so-called PEGylation, is the most commonly used method for reducing premature clearance of NPs from the circulation. However, several reports point out that PEGylation may negatively influence the performance of NPs as a drug carrier. Alternative surface modification strategies, including substitute polymers, conditional removal of PEG, and biomimetic surface modification, may provide solutions for the limitations of PEG.

One‐Step Multipurpose Surface Functionalization by Adhesive Catecholamine

Abstract: Surface modification is one of the most important techniques in modern science and engineering. The facile introduction of a wide variety of desired properties onto virtually any material surface is an ultimate goal in surface chemistry. To achieve this goal, the incorporation of structurally diverse molecules onto any material surface is an essential capability for ideal surface modification. Here, we present a general strategy of surface modification, in which many diverse surfaces can be functionalized by immobilizing a wide variety of molecules. This strategy functionalizes surfaces by a one-step immersion of substrates in a one-pot mixture of a molecule and a catecholamine surface modification agent. This one-step procedure for surface modification represents a standard protocol to control interfacial properties.

Functionalized carbon nanotubes: biomedical applications

Abstract: Carbon nanotubes (CNTs) are emerging as novel nanomaterials for various biomedical applications. CNTs can be used to deliver a variety of therapeutic agents, including biomolecules, to the target disease sites. In addition, their unparalleled optical and electrical properties make them excellent candidates for bioimaging and other biomedical applications. However, the high cytotoxicity of CNTs limits their use in humans and many biological systems. The biocompatibility and low cytotoxicity of CNTs are attributed to size, dose, duration, testing systems, and surface functionalization. The functionalization of CNTs improves their solubility and biocompatibility and alters their cellular interaction pathways, resulting in much-reduced cytotoxic effects. Functionalized CNTs are promising novel materials for a variety of biomedical applications. These potential applications are particularly enhanced by their ability to penetrate biological membranes with relatively low cytotoxicity. This review is directed towards the overview of CNTs and their functionalization for biomedical applications with minimal cytotoxicity.

Molecular Structure of 3-Aminopropyltriethoxysilane Layers Formed on Silanol-Terminated Silicon Surfaces

Abstract: The use of the coupling agent, 3-aminopropyltriethoxysilane (APTES), in the silanization reaction with silanol-terminated silicon is an important surface modification reaction. Of particular importance is that the terminal amine functionalities of APTES are sufficiently exposed to the gas or liquid phase for further modifications, such as amide coupling reactions. Here, metastable induced electron spectroscopy (MIES) and UV photoelectron spectroscopy (UPS) were used to study the composition of the outermost layer of a silanol-terminated Si surface after silanization with APTES. High-resolution X-ray photoelectron spectroscopy (XPS) was used to validate the attachment of APTES to the surface. Density of States (DOS) calculations were employed for interpreting the MIE spectra. Findings showed that amine functionalities covered only a small fraction of the APTES-modified Si surface.

Synthesis of Surface-Functionalized WS2 Nanosheets and Performance as Li-Ion Battery Anodes

Abstract: Separation of bulk tungsten disulfide (or WS2) into few-layer two-dimensional (2-D) crystals is of interest because of their high surface area for certain chemical processes and size-dependent optical and electronic characteristics. Herein, we demonstrate a process that involves the physical separation of weakly bonded WS2 layers by use of a strong acid treatment (chlorosulfonic acid) at 2 mg/mL, followed by quenching in deionized (DI) water. X-ray photoelectron spectroscopy of the superacid-treated WS2 suggests the formation of W–O type bonds, signifying oxidation of tungsten and reduction of the sulfur phase. Thermogravimetric analysis showed a three-phase weight-loss pattern, suggesting acid functionalization of WS2 surfaces. We also studied the electrochemical behavior of an acid-treated WS2 anode in a lithium half-cell configuration that showed a three-step charge–discharge behavior, characteristic of a conversion reaction. The electrochemical capacity was 118 mAh/g after 50 cycles.

Improving the dielectric constants and breakdown strength of polymer composites: effects of the shape of the BaTiO3 nanoinclusions, surface modification and polymer matrix

Abstract: Flexible polymer composite films are prepared by a solution cast method with polar polyvinylidene fluoride (PVDF) or non-polar epoxy as the polymer matrix. BaTiO3 nanoparticles and BaTiO3 nanofibers with large aspect ratio are used as dielectric fillers after surface modification by polydopamine. The effects of filler shape, surface modification and polarity of polymer matrix on the microstructure, dielectric constants and breakdown strength of polymer composites are investigated in detail. Surface modification by polydopamine improves the compatibility between BaTiO3 and polymer as well as passivating the surfaces of BaTiO3. At the same volume fraction, composites filled with BaTiO3 nanofibers exhibit greater dielectric constants than the composites filled with BaTiO3 nanoparticles. The polydopamine layers on BaTiO3 nanofibers give rise to stronger interfaces between the fillers and polymer matrices. Improved breakdown strengths are achieved in both composites. This work may provide a general strategy for flexible polymer nanocomposites with greatly enhanced dielectric constants and breakdown strength.

Surface modification for PDMS-based microfluidic devices

Abstract: This review focuses on advances reported from April 2009 to May 2011 in PDMS surface modifications for the application in microfluidic devices. PDMS surface modification techniques presented here include improved plasma and graft polymer coating, dynamic surfactant treatment, hydrosilylation-based surface modification and surface modification with nanomaterials such as carbon nanotubes and metal nanoparticles. Recent efforts to generate topographical and chemical patterns on PDMS are also discussed. The described surface modifications not only increase PDMS wettability, inhibit or reduce non-specific adsorption of hydrophobic species onto the surfaces in the act, but also result in the display of desired functional groups useful for molecular separations, biomolecular detection via immunoassays, cell culture and emulsion formation.

Synthesis of graphene-multiwalled carbon nanotubes hybrid nanostructure by strengthened electrostatic interaction and its lithium ion battery application

Abstract: We report a novel way of synthesizing graphene-carbon nanotube hybrid nanostructure as an anode for lithium (Li) ion batteries. For this, graphene was prepared by the solar exfoliation of graphite oxide, while multiwalled carbon nanotubes (MWNTs) were prepared by the chemical vapor deposition method. The graphene–MWNT hybrid nanostructure was synthesized by first modifying graphene surface using a cationic polyelectrolyte and MWNT surface with acid functionalization. The hybrid structure was obtained by homogeneous mixing of chemically modified graphene and MWNT constituents. This hybrid nanostructure exhibits higher specific capacity and cyclic stability. The strengthened electrostatic interaction between the positively charged surface of graphene sheets and the negatively charged surface of MWNTs prevents the restacking of graphene sheets that provides a highly accessible area and short diffusion path length for Li-ions. The higher electrical conductivity of MWNTs promotes an easier movement of the electrons within the electrode. The present synthesis scheme recommends a new pathway for large-scale production of novel hybrid carbon nanomaterials for energy storage applications and underlines the importance of preparation routes followed for synthesizing nanomaterials.

Dynamics of ripple formation on silicon surfaces by ultrashort laser pulses in subablation conditions

Abstract: An investigation of ultrashort pulsed laser--induced surface modification due to conditions that result in a superheated melted liquid layer and material evaporation are considered. To describe the surface modification occurring after cooling and resolidification of the melted layer and understand the underlying physical fundamental mechanisms, a unified model is presented to account for crater and subwavelength ripple formation based on a synergy of electron excitation and capillary wave solidification. The proposed theoretical framework aims to address the laser--material interaction in subablation conditions and thus the minimal mass removal in combination with a hydrodynamics-based scenario of the crater creation and ripple formation following surface irradiation with single and multiple pulses, respectively. The development of the periodic structures is attributed to the interference of the incident wave with a surface plasmon wave. Details of the surface morphology attained are elaborated as a function of the imposed conditions, and results are tested against experimental data.

Surface-Plasmon-Induced Visible Light Photocatalytic Activity of TiO2 Nanospheres Decorated by Au Nanoparticles with Controlled Configuration

Abstract: This work is focused on the development of a surface plasmon-induced visible light active photocatalyst system composed of silica–titania core–shell (SiO2@TiO2) nanostructures decorated with Au nanoparticles (Au NPs). The influence of size and distribution of Au NPs on photocatalysis, its fabrication methods, and exploration of the mechanism of visible light activity were investigated. A favorable architecture of SiO2 beads with a thin layer of TiO2 was decorated with Au NP arrays having different size and areal density. Surface modification of SiO2@TiO2 leads to a viable and homogeneous loading of Au NPs on the surface of TiO2, which renders visible light-induced photocatalytic activity on the whole TiO2 surface. An optimized system employing Au NP arrays with 15 nm size and 700/μm2 density showed best catalytic efficiency due to a synergistic effect of the firm contact between Au NPs and TiO2 and efficiently coupled SPR excitation. A brief mechanism relating the electron transfer from surface-plasmon-st...

Biomimetic dopamine derivative for selective polymer modification of halloysite nanotube lumen.

Abstract: We demonstrate the use of a catecholic anchor (Dopa) for selective modification of the inner surface of an halloysite clay nanotube. Aqueous Dopa binds to alumina at the tube lumen and does not bind the silica surface under the same conditions. Selectivity of surface modification was evidenced using X-ray photoelectron spectroscopy (XPS) and 13C solid state NMR spectroscopy. Surface-initiated atom transfer radical polymerization (SI-ATRP) was performed through selectively adsorbed Dopa to graft a layer of polymer brush into the nanotube lumen.

The relationship of surface roughness and cell response of chemical surface modification of titanium

Abstract: Implant surface topography influences osteoblastic proliferation, differentiation and extracellular matrix protein expressions. Previous researches proved that chemical surface modification of titanium implants could be used to improve Bone-to-implant contact. In this study, the surface topography, chemistry and biocompatibility of polished titanium surfaces treated with mixed solution of three acids containing HCl, HF and H3PO4 with different etched conditions for example concentration, time and addition of calcium chloride were studied. Osteoblast cells (MG-63) were cultured on different groups of titanium surfaces. In order to investigate titanium surfaces, SEM, AFM and EDS analyses were carried out. The results showed that surfaces treated with HCl–HF–H3PO4 had higher roughness, lower cytotoxicity level and better biocompatibility than controls. Moreover, addition of calcium chloride into mixed solution of three acids containing HCl, HF and H3PO4 is an important, predominant and new technique for obtaining biofunction in metals for biomedical use including dentistry.