Surface Modification Of Silica Particles Research Articles

Quantitative Assessment of Protein Adsorption on Microparticles with Particle Mass Spectrometry

In this paper, particle mass spectrometry (PMS), which consists of an aerodynamic desorption/ionization (AD) source, a quadrupole ion trap (QIT) mass analyzer, and a charge detector, was exploited to characterize the protein adsorption on microparticles based on the mass variations of microparticles before and after protein adsorption. This method is simple and has low sample cost. Importantly, its mass resolution is good enough to distinguish the microparticles with and without protein. For the adsorption of bovine serum albumin (BSA) on 3 μm porous poly styrene-divinylbenzene (poly S-DVB), the minimum mass increase that can be resolved by PMS corresponds to 128 fg (1.8 ng/cm(2)) or 1.17 × 10(6) BSA molecules on each poly S-DVB particle. With PMS, the adsorption process of BSA on poly S-DVB spheres was successfully characterized, and the obtained maximum adsorption capacity qm and dissociation constant Kd were consistent with that determined by the conventional depletion method. In addition, the influence of surface modification of silica particles on the enzyme immobilization was evaluated. Compared with C4 (propyldimethylsilane), C8 (octyldimethylsilane), and Ph (phenyldimethylchlorosilane), the CN (cyanoethyldimethylchlorosilane) functionalized silica particles were screened to be most beneficial for the immobilization of both lysozyme and trypsin.

Surface modification of silica particles assisted by CO2

This paper reports the synthesis of coating silica particles, in order to design hybrid materials with hydrophobic surface properties. The silica particles were prepared in basic conditions under atmosphere of carbon dioxide (CO2), using tetraethylorthosilicate (TEOS) as a precursor and octyltriethoxysilane (OTES) as a surface modifying agent. It was demonstrated that the contact angles of silica hybrid films could be changed by varying temperature and pressure of CO2. The investigation of the prepared hybrid materials by dynamic light scattering (DLS) and environmental scanning electron microscopy (ESEM), respectively, showed that they consisted mainly of particles with a diameter of 100–250nm. Fourier transform infrared (FT-IR) spectra indicate that the interaction between the coupling reagents, at different conditions, is mainly through chemical bonding.

Facile Modification of Surface of Silica Particles with Organosilanepolyol and Their Characterization

The surface modification of silica particles (SPs) was systemically conducted by the treatment of 0.1-10 wt % phenylsilanetriol (PST) on the basis of SPs used through two step processes: 1) the PST coating of SPs via evaporation under reduced pressure and 2) their thermal condensation leading to Si-O-Si bond formation via heating at <TEX>$130^{\circ}C$</TEX>. The evaluation of the modified SPs was conducted by the simple floating test on water and the measurement of the contact angle (CA) of water droplet on the 2-dimensional layer of modified SPs on slide glass. When PST was used about 2 wt % or above on the basis of SPs (about average size: 50 nm) used, the modified SPs were fully floated on the water and all dispersed into upper organic solvent layer after a shaking with the mixture of the water and benzene, indicating that the modified SPs have hydrophobic properties. The modified SPs were characterized by <TEX>$^{29}Si$</TEX> MAS NMR and physicochemical properties including SEM, TEM, BET, adsorption/desorption isotherms, etc. were measured and compared each other in details. This research demonstrates that the organosilanetriol is a good modifier applicable for the surface modification of inorganic oxide particles using a low amount of modifier on the basis of oxide particles used.

Ion transport in hybrid membranes based on MF-4SC and silica surface-modified with proton acceptor groups

Methods for synthesizing hybrid MF-4SC membranes containing silica whose surface has been modified with proton acceptor amine-containing groups (3-aminopropyl- and 3-(2-imidazoline-1-yl)-propyl-) are proposed. The incorporation of surface-modified silica particles into the membrane matrix leads to a decrease in the water uptake and exchange capacity compared to a membrane containing pure SiO2. The proton conductivity and diffusion permeability of NaCl and HCl solutions and the H+/Na+ ion interdiffusion are studied. The proton conductivity of the membranes containing surface-modified silica is higher than that of the parent membrane and the membrane containing pure SiO2. It is shown that the surface modification of silica with 5 mol % of nitrogen-containing groups results in a decrease in the diffusion permeability and an improvement in the ion transport selectivity. This extraordinary change in the properties is caused by an increase in the size of the pores and the channels that connect them, along with a significant decrease in the free volume within the pores. At the same time, an increase in the amount of modifying groups to 10 mol % leads to a sharp acceleration of the diffusion permeability and interdiffusion processes because of the formation of through pores in the membrane matrix.

Tuning the hydrophobicity of plasma polymer coated silica particles

The modification of particle hydrophobicity has been conventionally carried out using wet chemistry methods. This investigation has however applied plasma polymerisation as a novel approach to produce silica particles with tailored hydrophobicity. Deposition of plasma polymerised 1,7-octadiene (ppOD) was carried out using a radio frequency inductively coupled reactor fitted with a rotating chamber. Plasma polymerisation parameters were varied to study the hydrophobicity of hydrocarbon functionalised particles. The surface chemistry of the ppOD coated particles was analysed via X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. Deposition of ppOD coatings under low specific energy plasma conditions resulted in both chemically and hydrophobically heterogeneous ensemble of particles. Whereas optimised plasma conditions resulted in homogeneous ppOD coatings. Development of hydrophobicity in ppOD coated particles was confirmed by Washburn capillary rise measurements, film flotation tests and environmental scanning electron microscopy observations. Silica particles with a range of water contact angles from 36° to more than 90° were obtained by controlled deposition of ppOD films. Plasma polymerisation using a rotating reactor has shown to be an efficient approach in the surface modification of silica particles to obtain surfaces with controlled hydrophobicity, which are of direct interest in a diverse range of practical applications as well as fundamental studies.

Immobilization of laccase by Cu2+ chelate affinity interaction on surface-modified magnetic silica particles and its use for the removal of 2,4-dichlorophenol

Magnetic Cu(2+)-chelated silica particles that employ polyacrylamide as a metal-chelating ligand were developed and used to immobilize laccase by coordination. The particles were characterized by scanning electron microscope and Fourier transform infrared spectroscopy. The preparation, the enzymatic properties of the immobilized laccase, and its catalytic capacity for 2,4-dichlorophenol degradation were systemically evaluated. The results showed that immobilized laccase exhibited maximum enzyme activity when it was immobilized for 1h at a pH of 4.0 and a temperature of 5°C. The optimum laccase dose was 20mg/g of carrier. In comparison to free laccase, the immobilized laccase had better acid adaptability and thermal stability. Higher activity was observed for immobilized laccase at a pH range of 2.0 to 3.5 and temperatures from 25 to 40°C. The immobilized laccase that was prepared for this work exhibited a good catalytic capacity for removing 2,4-dichlorophnol from aqueous solutions.

Peptide-based surface modified silica particles: adsorption materials for dye-loaded wastewater treatment

Surface-modified silica particles were prepared via solid-phase grafting methodology, and their prospective utility in wastewater treatment was evaluated. The structure–activity relationship of the designed particles was investigated for silica surfaces grafted with various amino acid-based peptide molecules to determine the effect of the chemical nature on the adsorption capacity of these surface-modified silica particles. The successful grafting of the organic phase over the modified silica surface was confirmed on the basis of infrared absorption and solid-state 13C NMR data, as well as thermogravimetric and elemental analyses. The organically modified silica particles effectively adsorbed anionic targets such as organic dyes and surfactants from aqueous medium, and the adsorption behaviour followed pseudo-second order kinetics, which conformed to the Freundlich or Langmuir adsorption isotherms. Furthermore, hydrophobic interaction of the aliphatic peripherals of the modified silica with the alkyl tail of the surfactant was the major force for adsorption of the surfactants onto the modified silica, whereas π–π and electrostatic interactions played a major role in the adsorption of anionic dye molecules.

Existence of a Lower Critical Radius for Incorporation of Silica Particles into Zinc during Electro-codeposition

Recently, it was shown that the surface modification of silica particles with -SH functional groups enables their electro-codeposition with zinc. Here, however, we report that no incorporation into Zn can be observed for such modified particles with diameters of <100 nm, while incorporation is possible for particles with diameters of 225 nm and larger. Furthermore, when silica particles are functionalized with mixtures of -SH and -Cl functional groups, which affect the interface energy at the particle/metal interface differently but have similar interfacial energies for the particle/electrolyte interface, it is found that, for successful incorporation of the particles, a minimum amount of -SH functional groups is needed. An explanation for these observations has been derived based on energetic considerations regarding the interfaces involved in the process.

Electrophoretic impregnation of porous anodic aluminum oxide film by silica nanoparticles

In this paper, it is proposed to study the deposition of nanoparticles by electrophoretic deposition (EPD) inside a porous anodic aluminum oxide film. Despite the presence of a highly resistive barrier layer at the metal-anodic film interface, porous anodic films on AA 1050A were successfully filled by 16-nm, surface modified silica particles. During this study it was shown that both the colloidal suspension conductivity and the applied electric field drive the penetration into the porous film. FEG-SEM observations showed that large (130-nm diameter), linear pores of 10μm in length can be completely filled in 1min. These results attest that porous anodic films can be efficiently filled with nanoparticles by EPD despite the presence of the barrier layer.

Preparation of various Janus composite particles with two components differently combined

Janus composite particles with a combination of organic and inorganic substances were synthesized by soap-free emulsion polymerization in which an amphoteric initiator of 2,2′-azobis[N-(2-carboxyethyl)-2-2-methylpropionamidine] (VA-057) was employed to introduce a polystyrene (PSt) lobe onto silica cores surface-modified with 3-methacryloxypropyltrimethoxy silane (MPTMS). Thermogravimetric analysis and X-ray photoelectron spectroscopy were used to characterize the surface-modified silica particles and showed that a small amount of MPTMS introduced onto the surface of silica particles could successfully prepare SiO2–PSt Janus particles. The oxide part of SiO2–PSt Janus particles obtained with the polymerization was further surface-modified with 3-aminopropyltriethoxysilane (APS) to introduce positively charged amino groups on the silica surface. The silica surface modified with APS was covered with gold by electroless deposition in which a gold precursor of auric chloride was reduced with ascorbic acid in the presence of polyvinylpyrrolidone. The electroless deposition of gold successfully produced Janus particles with a combination of gold and PSt surfaces. Furthermore, dissolution of the polymer component of the Au–PSt Janus particles in tetrahydrofuran led to another Janus type of particles with an inorganic combination of Au and SiO2.

Effect of surface modification of silica nanoparticles on toxicity and cellular uptake by human peripheral blood lymphocytes in vitro

Silica nanoparticles have an interesting potential in drug delivery, gene therapy and molecular imaging due to the possibility of tailoring their surface reactivity that can be obtained by surface modification. Despite these potential benefits, there is concern that exposure of humans to certain types of silica nanomaterials may lead to significant adverse health effects. The motivation of this study was to determine the kinetics of cellular binding/uptake of the vinyl- and the aminopropyl/vinyl-modified silica nanoparticles into peripheral blood lymphocytes in vitro, to explore their genotoxic and cytotoxic properties and to compare the biological properties of modified silica nanoparticles with those of the unmodified ones. Size of nanoparticles determined by SEM varied from 10 to 50 nm. The average hydrodynamic diameter and zeta potential also varied from 176.7 nm (+18.16 mV) [aminopropyl/vinyl-modified] and 235.4 nm (−9.49 mV) [vinyl-modified] to 266.3 (−13.32 mV) [unmodified]. Surface-modified silica particles were internalized by lymphocytes with varying efficiency and expressed no cytotoxic nor genotoxic effects, as determined by various methods (cell viability, apoptosis/necrosis, oxidative DNA damage, chromosome aberrations). However, they affected the proliferation of the lymphocytes as indicated by a decrease in mitotic index value and cell cycle progression. In contrast, unmodified silica nanoparticles exhibited cytotoxic and genotoxic properties at high doses as well as interfered with cell cycle.

Composite membranes based on a sulfonated poly(arylene ether sulfone) and proton-conducting hybrid silica particles for high temperature PEMFCs

The organic–inorganic composite membranes are prepared by inserting poly(styrene sulfonate)-grafted silica particles into a polymer matrix of sulfonated poly(arylene ether sulfone) copolymer. The first step consisted in using atom transfer radical polymerization method to prepare surface-modified silica particles grafted with sodium 4-styrenesulfonate, referred to as PSS-g-SiO 2. Ion exchange capacities up to 2.4 meq/g are obtained for these modified silica particles. In a second step, a sulfonated poly(arylene ether sulfone) copolymer is synthesized via nucleophilic step polymerization of sulfonated 4,4′-dichlorodiphenyl sulfone, 4,4′-dichlorodiphenyl sulfone and phenolphthalin monomers in the presence of potassium carbonate. The copolymer is blended with various amounts of silica particles to form organic–inorganic composite membranes. Esterification reaction is carried out between silica particles and the sulfonated polymer chains by thermal treatment in the presence of sodium hypophosphite, which catalyzed the esterification reaction. The water uptake, proton conductivity, and thermal decomposition temperature of the membranes are measured. All composite membranes show better water uptake and proton conductivity than the unmodified membrane. Moreover, the membranes are tested in a commercial single cell at 80 °C and 120 °C in humidified H 2/air under different relative humidity conditions. The composite membrane containing 10%(w/w) of PSS-g-SiO 2 particles, which have ester bonds between polymer chains and silica particles, showed the best performance of 690 mA cm −2 at 0.6 V, 120 °C and 30 %RH, even higher than the commercial Nafion ® 112 membrane.

Ferromagnetic FePt-Nanoparticles/Polycation Hybrid Capsules Designed for a Magnetically Guided Drug Delivery System

The present Article describes the synthesis of ferromagnetic capsules approximately 330 nm in diameter with a nanometer-thick shell to apply to magnetic carriers in a magnetically guided drug delivery system. The magnetic shell of 5 nm in thickness is a nanohybrid, composed of ordered alloy FePt nanoparticles of approximately 3-4 nm in size and a polymer layer of a cationic polyelectrolyte, poly(diaryldimethylammonium chloride) (PDDA). The magnetic capsules have an excellent capacity for carrying medical drugs and genes. Surface-modified silica particles with PDDA were used as a template for the capsules. FePt nanoparticles were deposited on the PDDA-modified silica particles through a polyol method followed by dissolving the silica particles with a NaOH solution, resulting in the formation of the magnetic capsules as the final product. A three-dimensional hollow structure is maintained by the nanohybrid shell. The FePt-nanoparticles/PDDA nanohybrid shell also exhibits a ferromagnetic feature at room temperature because the FePt nanoparticles of an ordered-alloy phase are formed with the aid of PDDA despite the small size (3-4 nm).

Shape memory polyurethanes cross-linked by surface modified silica particles

Thermoresponsive polyurethane (PU)–silica nanocomposites were synthesized by incorporating silica particles as multifunctional cross-linkers into the PUvia sol–gel reactions. At 2 wt% silica, the composites showed over 99% shape fixity and shape recovery up to the 4th thermomechanical cycle along with outstanding mechanical properties in their rubbery as well as glass state. The incorporated nano-sized silica particles gave dual effects of multifunctional chemical cross-links and reinforcing fillers. The properties were favorably compared with those of uncross-linked PU and conventionally cross-linked PU.

Surface properties of silica nanoparticles modified with polymers for polymer nanocomposite applications

The surface of silica nanoparticles was modified with poly(ethylene glycol) methacrylate (PEGMA) or poly(propylene glycol) methacrylate (PPGMA) in order to improve the dispersion of nanoparticles in a polymer matrix. Nanosized silica particles were synthesized by the Stöber method with tetraethyl orthosilicate (TEOS). Silica nanoparticles were treated with triethoxyvinylsilane (VTES) as a coupling agent to introduce reactive groups and the PEG or PPG were then grafted onto the particle surface via UV-photopolymerization. Various analytical methods, i.e., scanning electron microscopy (SEM), thermogravimetry (TG), zeta potential measurement, and water vapor adsorption measurement were used to comprehensively characterize the unmodified(pure) and modified silica particles. The SEM images of the pure and modified particles demonstrated that both particles have a spherical shape and a uniform size without agglomeration. The silica particles modified with polymers showed higher weight loss than unmodified silica particles because of the decomposition of the organic polymers grafted onto the particles. The surface modification of silica particles with polymers decreased the zeta potential values of the silica surface. Modified silica particles had lower water vapor adsorption due to the hydrophobic surface property resulting from the polymers grafted onto the silica surface. In addition, we have developed an electrical conductivity measurement as a novel method to analyze the surface properties of silica nanoparticles. The modified silica particles had lower electrical conductivity than that of unmodified silica particles.

Surface modification of silica particles by dry coating: Characterization and powder ageing

In this study the dry coating experiments were performed with two different processes using a high energy impact coater “Hybridizer” (Nara) and a high shear mixer “Cyclomix” (Hosokawa). Silica gel particles ( d 50 = 55 µm) were coated with fine particles of magnesium stearate ( d 50 = 4.6 µm) at two different weight ratio of magnesium stearate, 5% and 15%. Several methods of characterization were used to study the effect of dry coating of the silica gel powder. The uncoated and coated silica gel particles were observed by environmental scanning electron microscopy (ESEM). The images have shown that a more uniform coating was obtained in the case of Hybridizer. The flowability of the different samples obtained with Hybridizer and Cyclomix have been characterized by measurements of the tapped and aerated densities. It has been shown that the flowability of silica gel treated in Hybridizer was not significantly affected whereas the flowability was reduced after treatment in the Cyclomix. The wettability of silica gel was determined by measurements of the contact angle between a water drop and a powder bed prepared for each sample. The results obtained have shown that the coating of silica gel powder by hydrophobic magnesium stearate in the two different devices, Hybridizer and Cyclomix, can improve its hydrophobic properties. The results of the different characterizations have been compared with those concerning the simple mixtures prepared by using a Turbula mixer. To investigate the stability and the ageing of silica gel particles after coating, three samples of silica gel coated with 15% (w/w) of magnesium stearate in the Hybridizer device have been stored under different relative humidities (RH). The temporal evolution of the contact angle and the volume of the drop water on the surface of the bed powder have been determined after 10 days or 36 days storage. The results have shown the influence of the relative humidity on the evolution of the coated silica gel particles. The surface of the host particles recovers its hydrophilic nature after 10 or 36 days storage under different relative humidity. No significant variations of the contact angle and the volume of the drop were recorded for the sample stored under dry atmosphere (RH < 12%). The ESEM observations of the different samples confirmed the results. A mechanism that can explain these ageing effects is proposed.

Particle–particle coating in a cyclomix impact mixer

Dry particle coating can be used to create new-generation materials by combining different powders exhibiting different physical and/or chemical properties. In such processes relatively large particles (host particles) are mechanically coated with fine particles (guest particles), without using solvents and subsequent drying, to create new functionalities or to improve initial characteristics. The coating of a host powder by guest particles can be performed in many different ways ranging from simple stirring of two components, to high energy impact coating. The purpose here is to examine the use of a Cyclomix high shear mixer granulator for the surface modification of silica particles by dry coating with magnesium stearate, and of cornstarch dry coated with hydrophilic or hydrophobic fume silica. Several powder characterisation methods have been used to study the physico-chemical properties of the coated particles. These include: Observation by environmental scanning electron microscopy (ESEM), Characterization of cohesion and flowability by tap density measurements, Determination of wettability by measurements of the contact angle between the coated particles and water. Measurement of moisture adsorption-desorption isotherms of uncoated and coated particles, and Tribo-electrification characteristics of the powders. The results show that the surface properties of the two host particles are changed, and that the Cyclomix can be used for dry particle coating to modify the properties of silica gel and cornstarch powders.

Preparation and properties of nano-silica modified negative acrylate photoresist

A series of silica modified photoresists had been successfully developed through incorporation of a particular nanoparticles suspension. Free radical polymerization was employed to synthesize the binder, an acrylate copolymer resin of benzyl methacrylate, methacrylic acid and 2-hydroxyethyl methacrylate, of the photoresist. The acid value, viscosity, molecular weight and thermal properties of the formed binders were measured. Then, surface-modified silica particles prepared by the sol–gel method were introduced to the photoresist. Because the modified silica particles contained considerable amount of reactive double bonds (C C) on their surfaces, they would react with the polyfunctional monomers in the photoresist to form an organic–inorganic nanohybrid. Fourier transform infrared spectrometer was used to analyze the evolution of chemical bonds at various stages of the preparation process. Thermal analyses including thermal gravimetric analyzer, differential scanning calorimeter and thermo-mechanical analyzer were used to evaluate the level of enhancement on thermal and dimensional stabilities of the photoresist due to silica incorporation.

Solid-Phase Synthesis of Amphiphilic Dendron-Surface-Modified Silica Particles and Their Application Toward Water Purification

Surface modification of silica particles by an amphiphilic poly(amido amine) (PAMAM) dendron and investigation of their advanced application toward water purification have been demonstrated. The amphiphilic dendron-surface-modified silica particles (C18GnS, n = 1−3) were prepared by solid-phase synthetic strategy including the propagation of PAMAM dendrons on silica surface through conventional divergent pathway and the end-group functionalization of dendrons by long aliphatic chains. Infrared absorption analyses confirmed the characteristic vibration modes of amide and methylene groups on the dendritic backbone and long alkyl peripherals, respectively. The gradual increasing amount of organic grafts determined by thermogravimetric and elemental analyses also supported the successful modification of amphiphilic dendron on the silica surface. C18GnS effectively adsorbed anionic targets such as organic dyes and surfactants in water, and the adsorption behavior obeyed a Langmuir adsorption isotherm. Moreover, the adsorption isothermal studies indicated that adsorption of surfactants on C18GnS was due to the assistance of hydrophobic interaction between the aliphatic peripherals on the dendron and the alkyl tail on the surfactant, while the electrostatic interaction with C18GnS mainly played a role for the adsorption of dyes. Anionic adsorbates were released from C18GnS in an alkaline environment because of the pH-dependent nature of PAMAM dendron, and thus the surface-modified silica particles were recovered and reused.

Nanoengineering of Surface Modified Silica Particles to Form Core-Shell and HollowNanospheres of Iron Oxide

The method of synthesizing nanoshell of alpha-Fe2O3 on silica core nanoparticle and hollow alpha-Fe2O3 nanoparticles is described. The silica particles of approximately 160 nm diameter were surface modified using 3-aminopropyltrimethoxysilane (APS) for easy adsorption of iron on it. These particles were treated with FeCl3 and further heat treated up to 1000 degrees C to get alpha-Fe2O3 shell of thickness approximately 20 nm. The hollow iron oxide particles were prepared using sacrificial core removal using dilute HF solution. The particles were characterized for their structure, morphology, bonding and surface chemistry using Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Fourier Transform Infra Red Spectroscopy (FTIR), and X-ray Photoelectron Spectroscopy (XPS).