Submicrometer-sized Silica Particles Research Articles

Influence of Sodium Ions and Carbon Black on the Formation and Structural Color of Photonic Balls by Silica Particles.

In this study, photonic balls─spherical aggregates of submicrometer-sized silica particles with uniform particle size─were investigated as structural colored materials. The structural color of these photonic balls is influenced by the ordered arrangement of the silica particles. The research focused on how the addition of electrolytes, specifically NaCl, affects the formation of photonic balls to achieve the desired structural color. Without NaCl, the photonic balls formed onion-shaped colloidal crystals. At NaCl concentrations above 0.006 mol/L, the particles aggregated into short-range ordered structures. When the concentration exceeded 0.05 mol/L, the aggregates lost their spherical shape. The study also explored the addition of carbon black (CB), a water-dispersible material due to its surface charge. The findings revealed that NaCl induced the phase separation between the charged silica particles and CB, resulting in Janus-shaped photonic balls─one side exhibiting structural color and the other side appearing black due to the presence of CB. Changing the silica particle size altered the hues of these Janus-shaped photonic balls, though they appeared uniformly colored to the naked eye. While this study did not specifically examine the applications of Janus-shaped photonic balls composed of silica particles and CB, CB is known for its ability to absorb near-infrared radiation and convert it into heat as well as its conductive properties. Silica, on the other hand, has a low thermal conductivity and acts as an electrical insulator. The structurally colored Janus-shaped photonic balls created in this study may serve as pigments in applications requiring anisotropic heat generation and electrical conduction. Additionally, the study's findings suggest the potential for creating various types of Janus-shaped photonic balls from materials with differing densities.

Cross-Sectional Investigations of Spherical Colloidal Clusters from Submicrometer-Sized Silica Particles toward Designing Novel Photonic Materials

Cross-Sectional Investigations of Spherical Colloidal Clusters from Submicrometer-Sized Silica Particles toward Designing Novel Photonic Materials

Nature-Inspired Hierarchical Protrusion Structure Construction for Washable and Wear-Resistant Superhydrophobic Textiles with Self-Cleaning Ability.

The use of toxic components and short longevity greatly restricted the commercial application of superhydrophobic surfaces in oil-water separation, antifouling, and self-cleaning. To address these concerns, a durable, robust, and fluorine-free superhydrophobic fabric is prepared on account of inspiration of nature. In this work, submicrometer-sized silica particles with different particle sizes are deposited onto cotton fabrics, followed by hydrophobic modification of poly(dimethylsiloxane) (PDMS), and consequently bonded the substrate and coating via powerful covalent bonds through a simple dip-coating technique. The rough surface with an imitated lotus-leaf-like hierarchical protrusion structure is constructed by deposited submicrometer-sized particles with different particle sizes, while the fabric with a low surface energy is achieved by the hydrophobic modification of PDMS. Ultimately, the fabricated fabric exhibits extraordinary superhydrophobicity with a high water contact angle (WCA) of 161° and a small sliding hysteresis angle (SHA) of 2.4°. Besides, considerable mechanical stability to withstand 130 sandpaper abrasion cycles and 40 washing cycles, and chemical resistance with sustained superhydrophobic property in various harsh environments (e.g., boiling water, strong acid/base solutions, and various organic solvents), are presented. Moreover, higher than 90% separation efficiency with a contact angle >150 ° is produced even after 50 cycles when the fabricated fabric serves as a filter during the oil-water separation besides its outstanding staining resistance and self-cleaning property.

Ion-Beam Modification of Colloidal Silica Particle Masks to Tailor the Size of Ordered Arrays of Ag Nanostructures Produced by Nanosphere Lithography

ABSTRACTSpherical submicrometer-sized silica particles were prepared by the sol-gel method and deposited as a monolayer onto silicon wafers, in order to use them as a mask to create regular arrays of nanoscale surface features. Thus, by e-gun evaporation of a 50 nm thick Ag film through the silica mask, Ag nanostructures were obtained after removal of the silica monolayer. In order to tailor the mask characteristics (size and interparticle spacing), the silica masks were irradiated at room temperature with 4 and 6 MeV Si ions at different fluences up to 5×1015 ion/cm2, perpendicularly to the sample surface. After the irradiation the silica particles turned into oblate particles, as a result of the increase of the particle dimension perpendicular to the ion beam and the decrease in the parallel direction. By this way, the mask openings of the silica particle monolayer were modified as a function of the irradiation parameters, and the subsequent Ag e-gun evaporation allowed the formation of ordered arrays of Ag features. The size, shape and interparticle spacing of both the silica particles and the Ag deposits were determined by scanning electron microscopy.

Photoacoustic Studies of Colloidal Silica Particles after MeV Ion-Induced Shape Deformation

Ordered arrays of colloidal submicrometer-sized silica particles deposited onto silicon wafers were irradiated with MeV Si ions. The spherical silica particles turned into oblate particles as a result of the increase of the particle dimension perpendicular to the ion beam direction and the decrease in the parallel direction. Pulsed laser photoacoustic spectroscopy was used to study the structural changes of the silica particles after the ion-induced shape deformation. Our purpose is to correlate the mechanical vibrations generated by the pulsed laser as a function of the Si irradiation parameters: ion energy and fluence. Fast Fourier transform analysis of the photoacoustic signal was carried out in order to obtain the normal vibration modes of the system. The size, size distribution and shape of the silica particles were determined by scanning electron microscopy. Our results revealed significant structural differences between the spherical and the deformed silica particles.

A multinuclear solid-state magnetic resonance study on submicrometer-sized SiO 2 particles encapsulated by a PMMA shell

Submicrometer-sized silica particles encapsulated by poly(methyl methacrylate) via a novel methodology have been characterized by means of solid-state high-resolution NMR techniques. The organic–inorganic composite prepared under static conditions, using our previously published method, comprised silicacore–shell particles of approximately 180 nm functionalized with 3-(trimethoxysilyl)propyl methacrylate and an outer coating of poly(methyl methacrylate) with an approximate 10 nm thickness, shown by transmission electron microscopy, diffuse reflectance infrared Fourier transform spectroscopy, thermogravimetric analysis and differential scanning calorimetry. A systematic solid-state nuclear magnetic resonance study based on 29Si and 13C high-resolution techniques was performed herein for the submicrometer particles at the various stages of synthesis, thus characterizing the organic and inorganic components as well as their interface. The presence of TMSPM and PMMA was confirmed and the structural features of the TMSPM species characterized. Moreover, from a comparative study of functionalized silica samples with different average particle size, it was possible to reveal the significant effect of this parameter on the condensation reactions involved in the synthesis of such samples.

Energy-Dependent Deformation of Colloidal Silica Nanoparticles under Room Temperature Irradiation with MeV Si Ions

Spherical submicrometer-sized silica particles were prepared from a reaction mixture containing tetraethoxysilane, ammonia and ethanol, and deposited onto silicon wafers. The properties of these SiO2 particles depend on their size, size distribution and shape. Even if some of these characteristics can be perfectly controlled by appropriate synthesis conditions, several alternative approaches must be explored in order to modify the shape of silica particles. The samples were then irradiated at room temperature with Si ions at different energies (4, 6 and 8 MeV) and fluences up to 5×1015 Si/cm2, at an angle of 45° with respect to the sample surface. After the Si irradiation the spherical silica particles turned into ellipsoidal particles, as a result of the increase of the particle dimension perpendicular to the ion beam and a decrease in the parallel direction. This effect increases with the ion fluence and depends on the electronic energy loss of the impinging ions. We observed that the particle deformation decreases with the beam energy, mainly because our samples were irradiated at room temperature. Thermal effects must be studied in detail in order to elucidate the complete deformation mechanism, as the existence of additional mechanisms related to the electronic energy loss effects can not be excluded.

Encapsulation of submicrometer-sized silica particles by a thin shell of poly(methyl methacrylate)

Polymer encapsulation of submicrometer-sized silica particles by synthesis of the polymer shell, poly(methyl methacrylate) under static conditions in a reaction medium free of surfactants and stabilizing agents is described. The Stöber method, a base-catalyzed hydrolysis and condensation of tetraethyl orthosilicate is used for the synthesis of the monodisperse colloidal dispersion of silica particles. The silica particles are subsequently modified in situ with the surface grafting of the silane coupling agent, 3-(trimethoxysilyl)propyl methacrylate. Encapsulation is achieved using tetraethyl orthosilicate as a reaction medium, in which a thermally initiated radical polymerization of methyl methacrylate is promoted in the presence of the modified particles by a seeding method which leads to a thin coating of poly(methyl methacrylate), and hence silica core–shell particles. The complete encapsulation of individual silica spheres by poly(methyl methacrylate) is visually evidenced by TEM microscopy which reveals the presence of a polymer shell coating up to 10 nm. Evidence for the presence of a poly(methyl methacrylate) shell is further corroborated by DSC/TGA, DRIFT-IR and NMR measurements.

Synthesis of Highly Monodisperse Particles Composed of a Magnetic Core and Fluorescent Shell

Highly monodisperse particles composed of a magnetic silica core and fluorescent polymer shell were synthesized with a combined technique of heterocoagulation and soap-free emulsion polymerization. Prior to heterocoagulation, monodisperse, submicrometer-sized silica particles were prepared with the Stober method, and magnetic nanoparticles were prepared with a modified Massart method in which a cationic silane coupling agent of N-trimethoxysilylpropyl- N, N, N-trimethylammonium chloride was added just after coprecipitation of Fe (2+) and Fe (3+). The silica particles with negative surface potential were heterocoagulated with the magnetic nanoparticles with positive surface potential. The magnetic silica particles obtained with the heterocoagulation were treated with sodium silicate to modify their surfaces with silica. In the formation of a fluorescent polymer shell onto the silica-coated magnetic silica cores, an amphoteric initiator of 2,2'-azobis[ N-(2-carboxyethyl)-2-2-methylpropionamidine] (VA-057) was used to control the colloidal stability of the magnetic cores during the polymer coating. The polymerization of St in the presence of a hydrophobic fluorophore of pyrene could coat the cores with fluorescent polymer shells, resulting in monodisperse particles with a magnetic silica core and fluorescent polymer shell. Measurements of zeta potential for the composite particles in different pH values indicated that the composite particles had an amphoteric property originating from VA-057 initiator.

Deformation of colloidal silica particles using MeV Si ion irradiation

Spherical submicrometer-sized silica particles were prepared by the Stöber process, from a reaction mixture containing tetraethoxysilane, ammonia and ethanol, and deposited onto silicon wafers. While the properties of these SiO 2 particles depend on their size, size distribution and shape, monodisperse spherical particles were obtained with a narrow size distribution. The samples were then irradiated at room temperature with Si ions at two energies (4 MeV and 6 MeV) and fluences up to 5 × 10 15 Si/cm 2, at an angle of 45° with respect to the sample surface. The size, size distribution and shape of the silica particles were determined using scanning electron and atomic force microscopes. By means of the Si ion irradiation, the as-prepared spherical silica particles can be turned into ellipsoidal particles, as a result of an increase of the particle dimensions perpendicular to the ion beam and a decrease in the direction parallel to the ion beam. This effect increases with the ion energy and fluence, and depends on the electronic energy loss processes to which the impinging ions are subjected. Our results also suggest that the particle deformation is more important in the case of larger as-prepared silica colloids.

Rapid, Simple, and Sensitive Immunoagglutination Assay with SiO2 Particles and Quartz Crystal Microbalance for Quantifying Schistosoma japonicum Antibodies

The resurgence of the parasitic disease schistosomiasis calls for more efficient diagnostic tests. We developed a rapid, simple, portable, and sensitive immunoagglutination assay that uses SiO(2) particles and quartz crystal microbalance (QCM) for quantifying Schistosoma japonicum (Sj) antibodies (SjAb). We prepared submicrometer-sized silica particles derivatized with Sj antigens as replacements for traditional latex microspheres to specifically agglutinate in the presence of SjAb targets, and we used the QCM monitor to measure the resulting frequency shifts. We optimized the assay medium by adding poly(ethylene glycol) (PEG) as a response accelerator of immunoagglutination. To minimize or eliminate any nonspecific agglutination or adsorption interferences, we conducted appropriate sealing procedures separately for silica particles and the QCM probe. The measured frequency changes were linearly related to the SjAb concentrations in infected rabbit serum. The PEG-assisted immunoagglutination system was quantitatively sensitive to SjAb concentrations ranging from approximately 0.70 to 32.31 mg/L, with a detection limit of approximately 0.46 mg/L. The obtained linear regression equation was: y=43.61 x+80.44 (r=0.9872). Several serum specimens were evaluated with the developed QCM immunoassay and the results were compared with ELISA, validating the feasibility of practical applications. This novel immunoagglutination-based QCM detection format is rapid, simple to use, and more portable than conventional diagnostic immunoassays, thus offering a promising alternative tool that can be used for point-of-care clinical diagnosis of schistosomiasis, particularly in epidemic situations.

Synthesis of Well-Defined, Polymer-Grafted Silica Particles by Aqueous ATRP

Surface-initiated atom transfer radical polymerization (ATRP) of various hydrophilic methacrylate monomers on submicrometer-sized silica particles in aqueous media at 20 °C leads to polymer-grafted silica particles whose colloid stability depends on the nature of the grafted polymer. These new organic−inorganic hybrid particles have been extensively characterized by thermogravimetry, elemental microanalyses, FT-IR spectroscopy, dynamic light scattering, scanning electron microscopy, and X-ray photoelectron spectroscopy. They are expected to be interesting model colloids for evaluating theories of steric stabilization.