Synthesis of silica-coated rhodium nanoparticles in reversed micellar solution

Silica (SiO₂)-coated rhodium (Rh) nanoparticles were prepared using a water-in-oil microemulsion of polyoxyethylene (15) cetyl ether, cyclohexane and water. SiO₂-coated Rh nanoparticles were obtained by hydrolyzing metal alkoxide (tetraethylorthosilicate, TEOS) in the solution containing Rh complex nanoparticles followed by thermal and reduction treatments. In the SiO₂-coated Rh nanoparticle, a Rh particle with an average diameter of 4.1 nm was located nearly at the center of each spherical SiO₂ particle. The SiO₂ layer was approximately 15 nm thick. Since the Rh particle was wholly surrounded by SiO₂, the Rh particle of the SiO₂-coated Rh nanoparticle exhibited an extremely high thermal stability. Furthermore, the porous structure of the SiO₂ layer could be controlled by the hydrolysis conditions of TEOS.     

Fabrication of thermochromic composite using monodispersed VO2 coated SiO2 nanoparticles prepared by modified chemical solution deposition

Monodispersed thermochromic VO₂ particles were fabricated by VO₂ coating onto monodispersed SiO₂ nanoparticles with the modified chemical solution deposition technique using vanadium isopropoxide solution and monodispersed SiO₂ particle suspension solution. The average size of the resultant VO₂–SiO₂ particle was 57 nm and the coating thickness of the VO₂ layer was 6 nm. A thermochromic composite was fabricated using the VO₂–SiO₂ particles and a poly lactose acid polymer as a transparent matrix, and the transmittance of the composite at a high temperature was 10% less than that at a low temperature.     

Structural verification and optical characterization of SiO2–Au–Cu2O nanoparticles

In this paper, SiO₂–Au–Cu₂O core/shell/shell nanoparticles were synthesized by reducing gold chloride on 3-amino-propyl-triethoxysilane molecules attached silica nanoparticle cores for several stages. Cu₂O nanoparticles were synthesized readily with the size of 4–5 nm using a simple route of sol–gel method Then, they were clung to the surface of Au seeds. The morphology of the resultant particles was studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Transmission electron microscopy images demonstrate growth of monodispersed gold seeds and Cu₂O nanoparticles in narrow size up to 10 nm and 5 nm, respectively. The presence of gold and Cu₂O coating was confirmed by X-ray diffraction, Fourier transform infrared spectroscopy and UV–Vis spectroscopy. Absorption spectroscopy shows considerably 40 nm blue shift in absorption edge for SiO₂–Au–Cu₂O nanostructure rather than SiO₂–Au core/shell nanoparticles.     

pH-Dependent gold nanoparticle self-organization on functionalized Si/SiO2 surfaces

The self-organization of citrate- and acrylate-stabilized gold nanoparticles onto SiO₂/hydroxyl-, amino- and nitro-terminated surfaces was investigated as a function of pH. Bare clean Si/SiO₂ substrates were used as the SiO₂/hydroxyl-terminated surfaces and self-assembled monolayers (SAM) of (3-aminopropyl)trimethoxysilane (APTMS) and 3-(4-nitrophenoxy)-propyltrimethoxysilane (NPPTMS) on Si/SiO₂ were employed as the amino- and nitro-terminated surfaces, respectively. All the surfaces were fully characterized by contact angle, atomic force microscopy (AFM), ellipsometry and X-ray photoelectron spectroscopy (XPS). Citrate- and acrylate-stabilized gold nanoparticle stability was also investigated as a function of pH by UV–visible absorption spectroscopy and Z-potentiometry. The gold nanoparticle surface coverage of the substrates was independently estimated by AFM and XPS. The results show that colloid deposition on bare SiO₂/OH surfaces and on NPPTMS monolayers is negligible with the exception of acrylate-stabilized gold nanoparticles which were found to be immobilized on nitro-terminated surfaces at pH lower than 3.5. Nevertheless, APTMS monolayers interact strongly with citrate- and acrylate-stabilized gold nanoparticles exhibiting a dependence of the surface coverage from the pH of the colloidal solution.     

CeO2 nanocrystals: Seed-mediated synthesis and size control

This work reports on seed-mediated synthesis and size control of monodispersed CeO₂ nanoparticles. CeO₂ nanoparticles of mean size smaller than 2 nm were first prepared by a simple mixing of aqueous solution of cerium (IV) sulfate and ammonia solution at ambient conditions. Using these as-prepared fine particles as the tiny seeds, tunable sizes of CeO₂ nanoparticles were achieved via a facile hydrothermal treatment. All samples were characterized by X-ray diffraction (XRD), infrared (IR) spectroscopy, UV-vis spectroscopy, and thermogravimetric analysis (TGA). It is shown that in comparison with other inorganic cerium salts such as cerium (III) nitrates, cerium (IV) sulfate appears more suitable for forming CeO₂ nanoparticles at room temperature. Sulfate groups are strongly thermodynamically adsorbed on CeO₂ nanoparticle surfaces. The formation mechanism, surface hydration and sulfation characteristics of the resulting CeO₂ nanoparticles are also discussed.     

Roles of buffer solution and substrate surface on the characteristic of DNA network formed on SiO2

We clarified the roles of deoxyribonucleic acid (DNA) buffer solution and substrate surface on DNA attachment. We found that the buffer solution prepared by adding positively charged metallic ions (i.e., Mg²⁺ and Ca²⁺), improves the adhesion property of DNA on hydrophilic SiO₂. Furthermore, DNA network properties (i.e., cross-linked or stretched types) were mainly determined by the concentration of DNA, the time for immobilization, the roughness of SiO₂ substrate, and efficiency of metallic ions. We suggested in this work that various types of DNA networks could be formed on the SiO₂ substrate via a relatively simple method.     

Patterned immobilisation of silicon dioxide nanoparticles on the surface of a photosensitive polymer

A photosensitive co-polymer of styrene and 4-vinylbenzyl thiocyanate was synthesised and employed for the immobilisation of aminofunctionalised silica nanoparticles (SiO₂-NP) at the polymer surface. Upon UV irradiation of the co-polymer, isothiocyanate groups are generated by a photo-isomerisation reaction of the thiocyanate groups. The silica nanoparticles were selectively immobilised in irradiated areas by immersing the illuminated polymer surface in a solution of SiO₂-NP. Depending on the time of immersion and the nanoparticle concentration, different amounts of silica can be deposited in the irradiated areas, whilst no immobilisation of SiO₂-NP is observed in the non-irradiated areas. By using photolithographic methods, patterned silica structures (μm scale) were produced on the polymer surface. The SiO₂-NP covered surfaces are of potential interest to generate protective surface layers and to carry out further functionalisation reactions of the immobilised SiO₂-NP particles.     

Photothermal Study of Two Different Nanofluids Containing SiO2 and TiO2 Semiconductor Nanoparticles

Thermal and optical properties of two different nanofluids containing SiO₂ and TiO₂ semiconductor nanoparticles were studied by thermal lens spectrometry (TLS) and spectrophotometry. In the case of SiO₂ nanofluids the transmission electron microscopy technique was used to obtain the SiO₂ nanoparticle sizes to investigate the size effect of these nanoparticles on the sample thermal diffusivity which is important in some medical applications such as photothermal-modulated drug delivery systems. On the other hand for the case of TiO₂ nanofluids, the photopyroelectric technique, TLS, scanning electron microscopy, and X-ray diffraction were employed to investigate the concentration effect on the thermal properties of these nanofluids. Thermal diffusivities and effusivities as functions of the TiO₂ nanoparticle concentrations were obtained. From the experimental results, an incremental increase in the thermal diffusivities and effusivities was observed when the nanoparticle concentration was increased, indicating that the nanoparticle concentration is an important factor to be considered to obtain nanofluids with more thermal efficiency which are required for some applications, such as degradation of residual water.     

A simple route to disperse silver nanoparticles on the surfaces of silica nanofibers with excellent photocatalytic properties

In this work, monodispersed silver nanoparticles decorated SiO₂ nanofibers were synthesized by electrospinning method, followed by thermal treatment at 600 °C. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo-gravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS) were used to characterize the composite nanofibers. Accordingly, the detailed formation mechanism of SiO₂/Ag composite nanofibers was discussed. Furthermore, an excellent catalytic activity of SiO₂/Ag composite fibers was observed by a degradation reaction of methyl orange (MO) dye.     

Successive nucleation and a rodlike growth of SiOx nanoparticles into the pore bottoms of an anodic alumina template

Although the SiO_x nanoparticles were previously reported to electrochemically nucleate from the bottoms of the pore array formed in the AAO/Ti/Si system, new applications of anodic aluminum oxide templates, i.e., successive nucleation and a rodlike growth of SiO_x nanoparticles, were observed utilizing the subsequent annealing technique after the nanoparticle precipitation. Tailoring the pore bottom profile by doping type and level of wafers also critically affected to nucleate the SiO_x nanoparticles from the pore bottoms. By anodization, as previously reported, only one nanoparticle per each pore was generally precipitated from the pyramid-shaped Si-containing TiO_x nanopillars; however, subsequent annealing under a low pressure of hydrogen enabled the successive precipitation of nanoparticles. Annealing under atmospheric pressure with H₂ and N₂ resulted in the rodlike growth of a single nanoparticle without successive nanoparticle precipitation.     

Strengthening of basalt fibers with nano-SiO2–epoxy composite coating

Coatings, which were made from pure epoxy and SiO₂ nanoparticle modified epoxy composite, respectively, were applied onto the basalt fiber rovings. The SiO₂ nanoparticles were synthesized using a sol–gel method and modified using coupling agent. Fourier transform infrared spectroscopy (FT-IR) and Differential Scanning Calorimetry (DSC) analyses indicated the formation of modified SiO₂ nanoparticles. The SiO₂ nanoparticle–epoxy composite coating gave rise to a significant increase in the tensile strength of the basalt fibers as compared with the pure epoxy coating, and also the coating endowed the basalt fiber with a promising interfacial property in the basalt fiber reinforced resin matrix composite. The coating modification was an effective way in improving the mechanical properties of basalt fibers and the properties of basalt fiber/epoxy resin composites.     

Single w/o microemulsion templating of CdS nanoparticles

We report the synthesis of monodispersed CdS nanoparticle with tunable size by controlling the reaction aging time in a single water in oil (w/o) microemulsion system. The w/o microemulsion system consists of nonionic surfactant poly (oxyethylene)₅ nonyl phenol ether (NP5), poly (oxyethylene)₁₀ nonyl phenol ether (NP10), cyclohexane and aqueous solution (cadmium salt and thioacetamide). Thioacetamide (TAA) has been utilized as a source for slow release of sulfur ions in the in situ synthesis of CdS. UV-Visible spectra shows obvious blue shift for the CdS nanoparticles as compared to the bulk material due to quantum size effect. CdS nanoparticle size depends on the reaction aging time where longer reaction aging time yields bigger particles. CdS nanoparticles growth behaviour as a function of reaction aging time in the microemulsion system was characterized by UV-Visible spectroscopy. The particle growth follows a power law with an exponential in the order of 0.17. Energy Filter Transmissions Electron Microscopy (EFTEM) reveals monodispersed CdS nanoparticles with standard deviation, less than 8%.     

Fabrication of multilayered Au/silica/gadolinium compound core–shell particles and their imaging properties

The present work proposes a preparation method for multilayered Au nanoparticle/silica/gadolinium compound core–shell (Au/SiO₂/GdC) particles. Silica-coated Au core–shell (Au/SiO₂) particles with a size of 38.0?nm were prepared by a sol-gel reaction in the presence of the Au nanoparticles with a size of 15.5?nm. Multilayered Au/SiO₂/GdC particles with sizes of ca. 35–52?nm were prepared by a homogeneous precipitation reaction in the presence of Au/SiO₂ particles. The computed tomography (CT) value of the Au/SiO₂/GdC colloid solution containing 4.3?×?10^?2?M Au was 344.1?HU: Its converted CT value (CT divided by Au concentration) was as large as 8.0?×?10³?HU/M. The r₁ value of the Au/SiO₂/GdC colloid solution was as large as 3.5?mM^?1?s^?1.     

Biofunctionalization of silica microspheres for protein separation

Mercapto-silica (SiO₂–SH) microspheres were prepared via direct hydrolysis of 3-mercaptopropyltrimethoxysilane (MPS) in a basic aqueous solution. The content of surface thiol group (SH) of SiO₂–SH microspheres was measured by Ellman's reagent method and X-ray photoelectron spectroscopy (XPS) and the content of surface thiol group of SiO₂–SH microspheres is strongly dependent on the reaction conditions. The thermal stability of SiO₂–SH microspheres was evaluated by thermogravimetric (TG) analysis, which tended to reduce with the increase of content of surface thiol groups. SiO₂–SH microspheres can be easily modified with reduced glutathione (GSH) to generate SiO₂–GSH microspheres for the affinity separation of Glutathione S-transferase (GST). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was performed to examine the validity of the separation procedure. The results showed that SiO₂–GSH microspheres were efficient in GST affinity separation from mixed proteins.     

Amorphous Silica Nanoparticles Promote Monocyte Adhesion to Human Endothelial Cells: Size‐Dependent Effect

There is evidence that nanoparticles can induce endothelial dysfunction. Here, the effect of monodisperse amorphous silica nanoparticles (SiO₂‐NPs) of different diameters on endothelial cells function is examined. Human endothelial cell line (EA.hy926) or primary human pulmonary artery endothelial cells (hPAEC) are seeded in inserts introduced or not above triple cell co‐cultures (pneumocytes, macrophages, and mast cells). Endothelial cells are incubated with SiO₂‐NPs at non‐cytotoxic concentrations for 12 h. A significant increase (up to 2‐fold) in human monocytes adhesion to endothelial cells is observed for 18 and 54 nm particles. Exposure to SiO₂‐NPs induces protein expression of adhesion molecules (ICAM‐1 and VCAM‐1) as well as significant up‐regulation in mRNA expression of ICAM‐1 in both endothelial cell types. Experiments performed with fluorescent‐labelled monodisperse amorphous SiO₂‐NPs of similar size evidence nanoparticle uptake into the cytoplasm of endothelial cells. It is concluded that exposure of human endothelial cells to amorphous silica nanoparticles enhances their adhesive properties. This process is modified by the size of the nanoparticle and the presence of other co‐cultured cells.     

Microsphere‐Like SiO2/MXene Hybrid Material Enabling High Performance Anode for Lithium Ion Batteries

To address the non‐negligible volume expansion and the inherent poor electronic conductivity of silica (SiO₂) material, microsphere‐like SiO₂/MXene hybrid material is designed and successfully synthesized through the combination of the Stöber method and spray drying. The SiO₂ nanoparticles are firmly anchored on the laminated MXene by the bonding effect, which boosts the structural stability during the long‐term cycling process. The MXene matrix not only possesses high elasticity to buffer the volume variation of SiO₂ nanoparticles, but also promotes the transfer of electrons and lithium ions. Moreover, the microsphere wrapped with ductile MXene film reduces the specific surface area, relieves the side reactions, and enhances the coulombic efficiency. Therefore, superior electrochemical performance including high reversible capacity, outstanding cycle stability, high coulombic efficiency, especially in the first cycle, excellent rate capability as well as high areal capacity are acquired for SiO₂/MXene microspheres anode.     

Combined modeling and experimental studies of hydroxylated silica nanoparticles

Nanotechnology offers several opportunities to solve problems related with Oil and Gas industry. One of them is the possibility to use hard nanoparticles to control the wettability phenomena between the three-phase system (oil–water–minerals) at reservoir conditions of temperature, pressure, and salinity. Here, we present a combined experimental and modeling study of hydroxylated silica nanoparticles as candidate for improved oil recovery applications. In this work, we mainly focus on development of more realistic SiO₂-nanoparticle models and validating them against the experimental data. An efficient Monte Carlo scheme is proposed to generate realistic SiO₂ nanoparticle atomistic models (3–5 nm). Structural and spectroscopic properties such as Raman and Infrared were obtained through Molecular Dynamics (MD) calculations using a force field that mimics an ab initio data. We have also used Fourier transform infrared spectroscopy to identify chemical functional groups present in 5 nm unmodified (bare) silica nanoparticle dispersions. A good agreement between the MD simulations and experiments has been observed.     

An Assessment of the Impact of SiO2 Nanoparticles of Different Sizes on the Rest/Wake Behavior and the Developmental Profile of Zebrafish Larvae

In this study, zebrafish larvae are introduced as an in vivo platform to examine the neurotoxicity and developmental toxicity associated with continuous exposure to a concentration gradient of different sizes of SiO₂ nanoparticles (15 nm and 50 nm diameter) to determine the dose effect and size effect of SiO₂ nanoparticle (NP)‐induced toxicity. Bovine serum albumin (BSA‐V) is utilized as a stabilizing agent to prevent coagulation of the SiO₂ nanoparticles. To the best of our knowledge, this study is the first to describe locomotor activity assays linking rest/wake behavioral profiles for the purpose of investigating the neurotoxicity of NPs. In addition, developmental toxicological endpoints including mortality, LC₅₀, malformation, and cartilaginous deformity are assessed. The results show a concentration‐dependent increase in behavioral neurotoxicity, mortality, and malformation among larvae treated with the SiO₂ nanoparticles of 15 nm and 50 nm. A comparison of the 15 nm and 50 nm NPs by K‐means clustering analysis demonstrates that the 15 nm NPs have a greater neurotoxic effect than the 50 nm NPs, with the 50 nm NPs exhibiting greater developmental toxicity on the zebrafish larvae than the 15 nm NPs.     

Simple template-free solution route for the synthesis of Cu(OH)2 and CuO nanostructures and application for electrochemical determination three ß-blockers

The synthesis of Cu(OH)₂ nanoparticles in a solution phase has been realised with high yield at low cost by simply dropping ammonia solution into an aqueous solution of CuCl₂ at ambient temperature. Furthermore, well-defined CuO nanostructures were produced by thermal dehydration of the as-prepared Cu(OH)₂ nanostructures in the solid state. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) were used to characterise the products. The electrochemical behaviour of three ß-blocker drugs on copper-oxide nanoparticle modified carbon paste electrodes was investigated. The modified electrodes showed excellent catalytic activity towards the oxidation of atenolol, carvedilol and propranolol in buffer solution. The linear concentration range of the proposed sensor for the atenolol, carvedilol and propranolol detection were 12–96, 5–37 and 10–104?µM, respectively.     

Synthesis and properties of hollow silica nanoparticles

Hollow nanoparticles of silicon dioxide (SiO₂) have been obtained using Cu/SiO₂ core-shell nanoparticles as precursors. An original technique based on heating the precursor nanoparticles to T = 400°C followed by a nanochemical reaction of copper oxide separation from hollow silica particles has been proposed and implemented for the first time. The obtained hollow SiO₂ nanoparticles have been studied by transmission electron microscopy. Mechanisms involved in the formation of hollow silica nanoparticles are discussed.