Shape Of Silica Nanoparticles Research Articles

Synthesis of Hollow Mesoporous Silica Nanospheroids with O/W Emulsion and Al(III) Incorporation and Its Catalytic Activity for the Synthesis of 5-HMF from Carbohydrates

Controlling the particle size as well as porosity and shape of silica nanoparticles is always a big challenge while tuning their properties. Here, we designed a cost-effective, novel, green synthetic method for the preparation of perforated hollow mesoporous silica nanoparticles (PHMS-1) using a very minute amount of cationic surfactant in o/w-type (castor oil in water) emulsion at room temperature. The grafting of Al(III) through post-synthetic modification onto this silica framework (PHMS-2, Si/Al ~20 atomic percentage) makes this a very efficient solid acid catalyst for the conversion of monosaccharides to 5-HMF. Brunauer–Emmett–Teller (BET) surface area for the pure silica and Al-doped mesoporous silica nanoparticles (MSNs) were found to be 866 and 660 m2g−1, respectively. Powder XRD, BET and TEM images confirm the mesoporosity of these materials. Again, the perforated hollow morphology was investigated using scanning electron microscopic analysis. Al-doped hollow MSNs were tested for acid catalytic-biomass conversion reactions. Our results show that PHMS-2 has much higher catalytic efficiency than contemporary aluminosilicate frameworks (83.7% of 5-HMF yield in 25 min at 160 °C for fructose under microwave irradiation).

Физические закономерности влияния характеристик наполнителя на трибологические свойства полимерного нанокомпозита

The paper analyzes the patterns of influence of the characteristics of silica nanoparticles on the friction coefficient and wear parameters during friction of a polymer nanocomposite (PNC) on a steel counterbody. The studies were performed theoretically using the method of movable cellular automata and experimentally according to the "block-on-ring" scheme. The size and shape of silica nanoparticles and the sliding velocity were varied. The model also took into account the temperature dependence of the mechanical properties of materials. It was found that the low friction properties of PNC are caused by changing the mechanical properties of the materials of a transition tribolayer under conditions of frictional heating. It was shown also that the size of the nanofiller affects the stability of friction and wear mode.

Non‐close packaged monolayer of silica nanoparticles on silicon substrate using HF vapour etching

Ordered monolayer of silica nanoparticles assembled on solid substrates is useful for a variety of promising applications in photonics, plasmonics, and solar cell. Nanoparticles are usually assembled into close- or non-close-packed monolayer (CPM) form. The non-close packed monolayer can be directly deposited from mono-dispersed colloidal suspension onto a solid substrate in terms of using complicated techniques or tuning the size of nanoparticles in the CPM. An effective method for forming the non-close packed monolayer of silica nanoparticles is reported. Silica nanoparticles are self-assembled into the CPM on silicon substrate. The size of silica nanoparticles is tuned by high frequency vapour etching. The dependence of the size and shape of silica nanoparticles on etching time is presented. The effect of sintering conditions on the etching process is also investigated.

Manipulating Size and Shape of Silica Nanoparticles with Liquid-Phase Transmission Electron Microscopy

Recently developed liquid-phase transmission electron microscopy (LP-TEM) holds great potential for dynamic imaging of relevant processes taking place in liquids at nanoscale, such as the evolution of nanoparticles during synthesis or structural changes of nanomaterials under working conditions [1]. LPTEM studies performed in the past years mainly focused on the growth of metallic nanoparticles from solutions, and pointed to important effects the electron beam can have on systems under observation [2]. Amongst various electron beam effects observed in LP-TEM, radiolysis of water and aqueous solutions leads to the formation of species such as eaq, H, OH, H2, H2O2, H, OH. These species can locally change the chemistry in the LP-TEM cell, triggering reactions such as reduction of metal ions. In fact, electron beam induced nucleation of metal nanoparticles has been one of the main focuses of the LPTEM studies so far [2].

Influence of the size and shape of silica nanoparticles on the properties and degradation of a PBI-based high temperature polymer electrolyte membrane

The life time stability of membrane material is one of the major parameters regarding reliability of high temperature polymer electrolyte membrane fuel cells. Present work has improved fuel cell durability and chemical stability by incorporating cross-linked silica particles in phosphoric acid doped poly(2,2′-m-phenylene-5,5′-bibenzimidazole) membranes. Three different silica particle contents were generated in membranes by in-situ sol–gel reaction from the precursor tetraethoxy silane and cross-linked to the polymer chains by using (3-glycidoxypropyl)-methyldiethoxysilane. The size, shape and distribution of the silica nanoparticles were examined by transmission electron microscopy. The amorphous characteristics and the chemical composition of the silica particles were investigated using X-ray diffraction, electron diffraction and energy dispersive X-ray spectroscopy. Detailed statistical analysis showed that by increasing the tetraethoxy silane content, the particle size was reduced while the amount of particles was increased. Ex-situ membrane characterization and in-situ membrane electrode assembly testing revealed a high influence of the silica content on the mechanical stability and start–stop-cycling behavior. The improved lifetime durability of the organic–inorganic composite membrane was proven in comparison to the pure polybenzimidazole membrane in membrane electrode assemblies over 1300h under constant fuel cell operation in reformate.

Development of laser dye-doped silica nanoparticles embedded optical preform for bio-analysis

I present here the study of optical and fluorescence properties, structure and morphology of silica nanoparticles bearing laser dye molecules are electrostatically attached with high refractive index organic dopant in acrylic optical preform rod. The photo physical fluorescence behaviour of laser dye molecules at the surface of different size and shape of silica nanoparticles has been reported. The interaction of laser dye-nanoparticles, nature of particles, and effect of various sizes and shapes of silica nanoparticles on fluorescence properties has been investigated. The developed optical preform has high potential for possible applications as bio-analysis sensor probe.

Influence of surfactant surface coverage and aging time on physical properties of silica nanoparticles

The experimental results on the influence of surfactant surface coverage and aging time on physical properties of silica nanoparticles were reported. The spherical silica nanoparticles have been synthesized using polyethylene glycol (PEG) as the surfactant and oil shale ash (OSA) as a new silica source. In order to identify the optimal condition for producing the best quality silica nanoparticles with the good dispersion and uniformity, the effects of surfactant surface coverage and aging time were investigated. It was found that the particle size and distribution of silica nanoparticles depend on the concentration of PEG in dispersion. At relatively low concentration, 0–2 wt.%, the existing PEG is not sufficient to prevent further growth of the initially formed silica nanoparticles, leading to large aggregates of silica particles. When the PEG concentration increases to 3 wt.%, self-assembled PEG layer on the surface stabilizes the initially formed silica nanoparticles and the silica particles with average diameter of 10 nm are uniformly distributed. With further increasing the concentration of PEG, the number of PEG aggregates increases and silica nanoparticles are mainly formed inside the entangled PEG chains, resulting in an observation of clusters of silica nanoparticles. Moreover, it was found that as the aging time increased, the shape of silica nanoparticles becomes regular and the particle size distribution becomes narrow.

Catalytic growth of silica nanoparticles in controlled shapes at planar liquid/liquid interfaces.

The shape of silica nanoparticles is controlled when they are synthesized at liquid/liquid interfaces; the combination of organic and aqueous phases that form the interface can change the shape of silica into a triangle, cube, or rod.

Influence of Reaction Parameters on Size and Shape of Silica Nanoparticles

It was investigated that the effect of various synthesis parameters such as, types of silicon alkoxides and alcohols, ammonia (catalyst) concentration, and reaction temperature on the particle size and shape of silica nanosphere by Sol-Gel method. When different silicon alkoxides were used, the silica particles except tetramethylorthosilicate (TMOS), all were spherical, and after reaching a maximum, the sizes were decreased with carbon chain length due to its steric effect. As the alcohol chain length increased from methanol (MeOH) to n-butanol (BuOH), the average particle size was increased from 30 nm to 800 nm. In general, all are having narrow particle size except BuOH sample were distributed bimodally (150 and 800 nm). When ammonia concentration increases, the particles also increased, however on increasing the reaction temperature, the particle sizes were reduced.