Effect Of Silica Coating Research Articles

Effect of silica-coating on crystal structure and magnetic properties of metallic nickel particles

The development of a simple method that perfectly controls the oxidation and aggregation of metallic particles has been performed. In the present work, metallic nickel (Ni) particles were used as a control, and silica-coating of them was performed to control oxidation and aggregation of them. Metallic Ni particles with a particle size of 924.1 ± 315.7 nm were synthesized in water and exposed to air. Nickel(II) acetate tetrahydrate, hydrazine, and poly(sodium 4-styrenesulfonate) were used as the Ni source, reducing reagent, and stabilizer, respectively. Silica-coating of the metallic Ni particles was performed by adding tetraethylorthosilicate/(3-aminopropyl)triethoxysilane/ethanol solution to the metallic Ni particle colloid solution (Ni/SiO2). The uncoated metallic Ni particles and metallic Ni in the Ni/SiO2 particles began to be oxidized while annealing in air to form NiO at 400 and 500 °C, respectively; the oxidation of metallic Ni particles was controlled by the silica coating. The Ni/SiO2 particles prepared and annealed at 100–300 °C showed soft magnetic behavior, and the saturation magnetization of g-Ni was almost comparable to that of bulk metallic Ni. In addition, the Ni/SiO2 particles annealed even at 500 °C still had soft magnetic behavior, which also supported that the oxidation of metallic Ni particles was successfully controlled by the silica coating.

The Effect of Silica Coating on the Drug Release Profile and Biocompatibility of Nano-MOF-5

The purpose of this study was the surface modification of nano MOF-5 (NMOF-5) or IRMOF-1 (Zn4O(C8H4O4)3) in order to prevent its rapid degradation in the phosphate-buffered saline (PBS), along with the simultaneous increase in its biocompatibility. The NMOF-5 sample was synthesized under the ultrasound irradiation and then it was loaded with acetaminophen and ibuprofen. Each assembly (NMOF-5@drug) was then coated with a silica layer. The obtained nanoparticles were identified by FT-IR spectroscopy, N2 adsorption porosimetry (BET), X-ray powder diffraction (XRD), the thermogravimetric analysis (TGA), and the field emission scanning electron microscopy (FE-SEM). UV/Vis spectroscopy was used to determine the release profile of the drugs from the bare and silica coated assemblies. Silica coating resulted in an enhanced stability in PBS, and the sustained release of each drug was achieved within 3 days. MTT (Methylthiazolyldiphenyl-tetrazolium bromide) assay on NIH3T3 mouse embryonic fibroblast cells as a model of the cell line showed that silica coating NMOF-5 with silica leads in the more biocompatibility and less cytotoxicity. The cell viability was increased up to 100% for the silica coated NMOF-5 compared to the bare NMOF-5. NMOF-5 and NMOF-5@silica were utilized in the injectable drug delivery for the first time. In this study, the toxicological studies about silica coated NMOF-5 in the drug delivery systems were developed.

Porous versus Dense ‐ Effect of Silica Coating on Contrast Enhancement of Iron Carbide Nanoparticles in T2‐Weighted Magnetic Resonance Imaging

AbstractMagnetic nanoparticles development is an intense subject in various biomedical applications. Among these applications, magnetic nanoparticles as contrast agents are of special interest for improving the diagnostic accuracy of magnetic resonance imaging (MRI). We report here the synthesis of magnetic iron carbide nanoparticles and their stabilization in aqueous media. The challenge of achieving phase transfer of hydrophobic iron carbide nanoparticles to hydrophilic media was addressed by silica shell. Silica coated iron carbide nanoparticles were fabricated with both mesoporous and dense silica shells followed by investigating the impact of such a coating on their performance as T2‐negative contrast agents in MRI. The crystalline structure of silica coated iron carbide nanoparticles was confirmed via X‐ray diffraction (XRD) analysis. Fourier transform infrared spectroscopy (FTIR) demonstrated formation of the silica coating and transmission electron microscopy (TEM) confirmed the core@shell morphology of silica coated iron carbide nanoparticles. Mesoporous and dense silica coated iron carbide nanoparticles exhibited high transverse relaxivity values of 457 and 365 mM−1s−1, respectively. The enhanced MRI efficiency obtained from the silica coated iron carbide nanoparticles highlights these core@shell structures as promising negative contrast agents. Based on the results, the nature of silica coating both in porous or dense forms has a significant effect on water relaxivity which makes the iron carbide@mesoporous silica nanoparticles highly efficient T2 contrast agents.

Effect of Silica Coating with Different Luting Cements on the Bond Strength of a Zirconia Based Ceramic

Statement of the problem: Debonding is a common cause of failure in zirconia-basedrestorations. Despite the use of resin cements and surface treatments, the rate of success remainsto be questioned.Purpose: The purpose of this study was to evaluate the effect of surface treatment using asilica coating (Co-Jet) method with different luting cements on the shear bond strength to zirconiasamples. The hypothesis was that surface treatment with different luting cements will influence thebond strength at the ceramic-cement interface.Materials and Methods: In this study 30 zirconia samples were constructed and underwentsurface treatment using a silica coating method (Co-Jet system). Zirconia samples were then bondedto composite samples using different luting agents (Bifix QM, Panavia 2.0 and Multilink Automix).Samples underwent a thermocycling aging process before shear bond strength was tested.Results: The highest shear bond strength was recorded with the Panavia 2.0 group while thelowest was with the Bifix QM group.Conclusions: Within the limitations of this study, the use of a Co-Jet sand silica coating systemwith Panavia 2.0 showed superior bond strength than the other luting cements.

The Effect of Silica Coatings on the Structural, Magnetic and Antimicrobial Properties of Silver Doped Manganite Magnetic Nanoparticles for Biomedical Applications

Surface modification of magnetic nanoparticles with biocompatible materials is usually required for biomedical applications. La0�80Ag0�15MnO3 (LAMO) magnetic nanoparticles (MNPs) were synthesized by the sol–gel auto combustion synthesis with the nanoparticles subsequently coated with silica. The effect of the coatings on the structural, morphology, magnetic properties, colloidal stability and antimicrobial properties of LAMO nanoparticles were studied using powder X-ray diffraction, thermogravimetric analysis, field emission scanning electron microscopy, zeta potential and vibrating sample magnetometer. The crystalline perovskite structure of LAMO was retained after silica coating but with a reduction in crystallinity. Also, there was a reduction of agglomeration and average crystallite size (48 nm) were the same after silica coating. The zeta potential of the coated sample revealed a considerable high colloidal stability value (−27.70 mV) at physiological pH 7.4. The magnetization values of 26 emu/g and 25 emu/g recorded for bare and coated LAMO samples, respectively show that LAMO MNPs retained its ferromagnetic behaviour after silica coating. Bare and silica coated LAMO gave very high bactericidal effect against S. aureus however, there was no change in the antimicrobial properties of LAMO MNPs with silica coating. These results show that while the silica coating influences greatly the morphology and colloidal stability of LAMO nanoparticles, it had virtually no effect on the crystalline structure and size, magnetization and the antimicrobial properties.

Effects of Silica Coating by Physical Vapor Deposition and Repeated Firing on the Low-Temperature Degradation and Flexural Strength of a Zirconia Ceramic.

To examine the application of physical vapor deposition (PVD) silica coating as an approach to retard low temperature degradation (LTD) for dental applications. Accelerated aging characteristics of heat- and surface-treated zirconia material were also investigated by exposing specimens to hydrothermal treatment. The specimens (90 disc-shaped specimens [15 mm ×1.2 mm]) were divided into 9 groups (n = 10) according to the test protocol: Ctrl, control (no surface treatment); Ag, autoclave aging; GrAg, grinding + aging; SiAg, silica coating + aging; GrSiAg, grinding + silica coating + aging; 3FAg, 3-time firing + aging; Gr3FAg, grinding + 3-time firing + aging; 5FAg, 5-time firing + aging; Gr5FAg, grinding + 5-time firing + aging. Accelerated aging was performed in a steam autoclave (134°C, 2 bars) for 12 hours. Following each treatment protocol, X-ray diffraction (XRD) analysis was used to estimate the relative amount of monoclinic phase and corresponding transformed zone depth (TZD). Additionally, a biaxial flexure test was used to calculate the flexural strength. Statistical analysis was conducted with one-way ANOVA and Fisher's LSD test (p < 0.05). The tetragonal-to-monoclinic transformation was retarded by PVD silica coating only on ground surfaces. Ground and heat-treated specimens exhibited the lowest monoclinic content after aging. The biaxial flexural strength value of the GrAg group was significantly higher than the values in all of the other groups except the SiAg group. The flexural strength value of the GrSiAg group was significantly higher than that of the 3FAg group. There was no statistically significant difference between the other groups (p > 0.05). Grinding decreased the susceptibility of zirconia to LTD and increased the flexural strength. PVD silica coating and repeated firing decreased the monoclinic content only in ground specimens during aging.

Effects of silica-coating on surface topography and bond strength of porcelain fused to CAD/CAM pure titanium.

The aim of this study was to evaluate the shear bond strength of porcelain fusing to titanium and the effects of surface treatment on surface structure of titanium. In the shear bond strength test, titanium surface treatments were: conventional, silica-coating without bonding agent, and silica-coating with bonding agent. Titanium surface treatments for analysis by the atomic force microscope (AFM) were: polishing, alumina sandblasting and silica-coating. The shear bond strength value of silica-coating with bonding agent group showed significantly higher than that of other groups. In AFM observation results, regular foamy structure which is effective for wetting was only observed in silica-coating. Therefore, this structure might indicate silicon. Silica-coating renders forms a nanoscopic regular foamy structure, involved in superhydrophilicity, to titanium surface, which is markedly different from the irregular surface generated by alumina sandblasting.

The effect of silica-coating on catalyst recyclability in ionic magnetic nanoparticle-supported Grubbs–Hoveyda catalysts for ring-closing metathesis

The Grubbs–Hoveyda type ruthenium–carbene complexes have been covalently immobilized on both silica coated and uncoated magnetic nanoparticles utilizing an imidazolium salt linker. These MNP-supported catalysts showed comparable catalytic activity to the homogeneous imidazolium salt-tagged ruthenium catalyst in the ring-closing metathesis (RCM) of dienes, and could effectively catalyze RCM reactions in the presence of only 0.85 mol% Ru. The MNP-supported ruthenium catalysts could be easily recovered using an external magnet. The recyclability of the silica-coated MNP-supported catalysts was superior to silica uncoated MNP-supported catalysts allowing reuse 14 times, due to the increased compatibility of the silica-coated MNPs with the reaction medium.

The effect of silica-coating by sol-gel process on resin-zirconia bonding

The effect of silica-coating by sol-gel process on the bond strength of resin composite to zirconia was evaluated and compared against the sandblasting method. Four groups of zirconia samples were silica-coated by sol-gel process under varied reagent ratios of ethanol, water, ammonia and tetraethyl orthosilicate and for different deposition times. One control group of zirconia samples were treated with sandblasting. Within each of these five groups, one subgroup of samples was kept in dry storage while another subgroup was aged by thermocycling for 6,000 times. Besides shear bond testing, the surface topography and surface elemental composition of silica-coated zirconia samples were also examined using scanning electron microscopy and X-ray photoelectron spectroscopy. Comparison of silica coating methods revealed significant differences in bond strength among the Dry groups (p<0.001) and Thermocycled groups (p<0.001). Comparison of sol-gel deposition times also revealed significant differences in bond strength among the Dry groups (p<0.01) and Thermocycled groups (p<0.001). Highest bond strengths were obtained after 141-h deposition: Dry (7.97±3.72 MPa); Thermocycled (2.33±0.79 MPa). It was concluded that silica-coating of zirconia by sol-gel process resulted in weaker resin bonding than by sandblasting.

Effects of Silica-Coating on the Photoinduced Hole Formation and Decomposition Activity of Titanium Dioxide Photocatalysts Under UV Irradiation

Contrary to the general knowledge in practical use of TiO2 photocatalyst, that silica coating improves weather resistance by inhibiting chemical activity against resin, the present study revealed that the number of photoinduced holes was increased and the decomposition activity to gaseous reactants was persistent as the effect of silica coating. Silica-coating did not block the hole formation, but prevent the adsorption of the reaction intermediates to sustain the photocatalytic activity.

Effect of Silica Coating on the Thermal Stability of Tantalum Based Nitrides Pigments

The colored TaON and Ta3N5 were synthesized by ammonolysis of amorphous Ta(OH)5 in the temperature range of 800-1000°C. Ta(OH)5 were prepared by titration process from TaCl5. TaON were synthesized at 900°C for 2 hr, and Ta3N5 were synthesized at 1000°C for 5 hr. In general, Ta3N5 powders were easily oxidized at 500°C with changing colority from red to white. To minimize the oxidation problem of Ta3N5 powders, we proposed silica coated system using TEOS and APTES as a surfactant. Tonality of silica coated Ta3N5 has very little changing which means silica coating actually minimizes the oxidation of the Ta3N5 particles.

Formation of Carbon Nanotubes through Ethylene Decomposition over Supported Platinum Catalysts: Effects of Silica Coating on Catalytic Performance of Platinum

Abstract Pt metal particles supported on carriers such as MgO and SiO2 showed high activity for the formation of carbon nanotubes (CNTs) through ethylene decomposition at 973 K. However, these CNTs were not uniform in diameter because of the sintering of Pt metal particles during the reaction. Covering Pt catalysts with silica prevented the sintering of Pt metal particles during ethylene decomposition, resulting in the formation of CNTs with a uniform diameter.

The Effect of Silica Coating on the Optical Response of Sub-micrometer Gold Spheres

The effects derived from the growth of silica shells on the optical properties of sub-micrometer gold spheres have been investigated as a function of shell thickness. The dipole plasmon resonance mode of these large spheres has been found to be significantly more sensitive to changes in the medium refractive index than the quadrupolar mode, in agreement with theoretical modeling based on the boundary element method (BEM) for concentric spheres. Near-field maps of both resonance modes in such coated nanoparticles show that the areas with significant near-field enhancement get progressively located within the silica shell as its thickness increases, with basically no enhancement outside of the shell when this is thicker than the sphere radius.

Effect of Silica Coating on Flexural Strength of Fiber Posts

Effect of Silica Coating on Flexural Strength of Fiber Posts

ルチル型チタニア微粒子の光触媒活性におよぼすシリカ被覆処理の影響

ルチル形チタニア微粒子 (TOP (R)) の光触媒活性を低下させることを目的として, 2種類の方法でシリカ被覆を試みた。1つは, ケイ酸ナトリウム水溶液からの析出反応を用いる従来法であり, 他の1つは, ヶイフッ化水素酸水溶液からの析出反応を利用した液相成膜 (LPD) 法である。TOP (R)) の光触媒活性の評価には, 硝酸銀を含む懸濁液への光照射によりTOP (R) 上に析出した単位表面積当りの銀の重量 (z値) を用いた。その結果, LPD法でシリカ被覆処理したTOP (R) のz値は, 従来法で処理したものの約1/10であることが明らかとなった。透過型電子顕微鏡写真とX線光電子分光法による分析結果は, 従来法よりもLPD法による方がシリカ被覆膜は均一であり, また, ち密な構造をしていることを示唆しており, このために優れた光触媒活性抑制効果を発現するものと考えられた。