Presence Of Silica Particles Research Articles

Facile Synthesis of Poly(methyl methacrylate) Silica Nanocomposite Monolith by In Situ Free Radical Polymerization of Methyl Methacrylate in the Presence of Functionalized Silica Nanoparticles.

Novel porous poly(methyl methacrylate) (PMMA) silica nanocomposites have been produced by utilization of polymerization-induced phase separation in a simple one-pot approach. A facile free radical polymerization of MMA in the presence of surface methacrylate-functionalized silica nanoparticles was carried out in ethanol-based solvents, successfully producing novel, morphologically designable porous nanocomposite monoliths. Differing from standard free radical polymerization in solution, a mixture of good and poor solvents (ethanol/N,N-dimethylformamide ratio) for the resulting polymer was used to trigger spinodal phase separation. The influence of monomer concentration, as well as solvent composition, on the morphology of the resulting porous polymers has been investigated. Porous monolith structures composed of connected particles and co-continuous morphologies were observed under a scanning electron microscope depending on the polymerization conditions. The resulting polymers were insoluble and showed swelling characteristics in some organic solvents that are capable of dissolving regular PMMA, indicating covalent bonds between the functionalized silica nanoparticles and the polymer chains. The presence of silica particles in the final polymer was proven via an ATR-IR analysis. The glass transition temperature of the present PMMA-silica nanocomposite was higher than that of the conventional PMMA. The porous polymer immersed in a mixed organic solvent showed coloration induced by the Christiansen effect.

High Adsorption Capacity of Ammonia Gas Pollutant Using Adsorbents of Carbon Composites

Air pollution is one of the most environmentally harmful to the human health and the climate change. The present study is aimed to investigate the effectiveness and capability of novel composite adsorbents prepared from modification of activated carbons (ACs) in the removal of air pollutants. The effect of both triethoxysilane propylamine (TEPSA) and carbon nanotube (CNT) on the adsorption properties of AC (TEPSA/CNT/AC); in addition, silica gel prepared from TEPSA to form silica nanoparticles (SiNP) along with CNT and AC (SiNP/CNT/AC), was studied. Ammonia gas (NH3) was used in this study as a typical emerging gas air pollutant. The physicochemical characteristics of the prepared ACs samples were analyzed using BET surface area, SEM, EDX, TEM and FTIR. Their results proved considerable changes in the porosity and surface functional groups after modifying AC surface with TEPSA or SiNP and CNT instantly. The adsorption findings showed that the NH3 removal efficiency using the prepared AC samples reached almost 97, 86 and 75% during 90 min at 25 °C for each sample of SiNP/CNT/AC, TESPA/CNT/AC and AC, respectively. Adsorption of NH3 relied mainly on the presence of silica particles and mesopore distributions in CNT rather than large total surface area in AC alone. Thus, the combination of SiNP as silanol and siloxane groups with CNT on AC surface raised significantly the adsorption capacity of NH3 from 194 to 300 mg/g. Conclusively, the SiNP/CNT/AC sample exhibited the best performance among all prepared samples used for the adsorption of NH3 gas from the indoor air. Also, Langmuir and Freundlich models were applied, and the results revealed that Freundlich model fits well the equilibrium adsorption data.

Tailoring Pickering Double Emulsions by in Situ Particle Surface Modification

Fundamental studies on the formation and stability of Pickering double emulsions are crucial for their industrial applications. Available methods of double emulsion preparation involve multiple tedious steps and can formulate a particular type of double emulsion, that is, water-in-oil-in-water (w/o/w) or oil-in-water-in-oil (o/w/o). In this work, we proposed a simple single-step in situ surface modification method to stabilize different types of double emulsions using hematite and silica particle systems which involves the addition of oleic acid. In the emulsification studies, we use (i) a combination of hematite and oleic acid, which is termed the binary system, and (ii) a mixture of hematite and silica particles together with oleic acid, which is designated as the ternary system. The wettability of hematite particles is tuned by direct or sequential addition of oleic acid to the water-decane medium. The direct surface modification (which involves the addition of a known quantity of oleic acid to the oil-water mixtures at once) of hematite particles in both binary and ternary systems shows transitional phase inversion from oil-in-water (o/w) to water-in-oil (w/o) emulsions. However, sequential surface modification results in the transition of a single emulsion to double emulsions. In the case of the binary system, the sequential surface modification of the hematite-particle-stabilized o/w emulsion can be converted into double emulsions of o/w/o type. However, in the case of the ternary system, i.e., in the presence of silica particles, sequential surface modification of hematite particles stabilizes both single (o/w) and double (w/o/w and o/w/o) emulsions. The critical concentration of oleic acid required to form a double emulsion is observed to be dependent on the ratio of the surface area of the silica particle to the total surface area of particles (S) and mixing protocols. A study of the size distribution of oil and water droplets of double emulsions shows that droplet size can be controlled by oleic acid concentration and magnitude of S. The arrangements of the particles at interfaces are visualized by SEM imaging. In this way, we developed an easy and novel single-step method of double emulsion preparation and provide a strategy to tailor the formation of different types of emulsions with a single/binary particle system by sequential in situ surface modification of the particles.

Genotoxicity Response of Fibroblast Cells and Human Epithelial Adenocarcinoma In Vitro Model Exposed to Bare and Ozone-Treated Silica Microparticles

Indoor air pollutants (IAP), which can pose a serious risk to human health, include biological pollutants, nitric oxide (NO), nitrogen dioxide (NO2), volatile organic compounds (VOC), sulfur dioxide (SO2), carbon monoxide (CO), carbon dioxide (CO2), silica, metals, radon, and particulate matter (PM). The aim of our work is to conduct a multidisciplinary study of fine silica particles (<2.5 μm) in the presence or absence of ozone (O3), and evaluate their potential cytotoxicity using MTS, micronucleus, and the comet test in two cell lines. We analyzed A549 (human basal alveolar epithelial cell adenocarcinoma) and Hs27 (human normal fibroblasts) exposed to dynamic conditions by an IRC simulator under ozone flow (120 ppb) and in the presence of silica particles (40 μg/h). The viability of A549 and Hs27 cells at 48 and 72 h of exposure to silica or silica/ozone decreases, except at 72 h in Hs27 treated with silica/ozone. The micronucleus and comet tests showed a significant increase in the number of micronuclei and the % of DNA in the queue, compared to the control, in both lines in all treatments, even if in different cell times/types. We found that silica alone or with more O3 causes more pronounced genotoxic effects in A549 tumor cells than in normal Hs27 fibroblasts.

Droplet Formation and Growth Mechanisms in Reaction-Induced Spontaneous Emulsification of 3-(Trimethoxysilyl) Propyl Methacrylate.

Spontaneous emulsification of 3-(trimethoxysilyl) propyl methacrylate (TPM) can produce complex and active colloids, nanoparticles, or monodisperse Pickering emulsions. Despite the applicability of TPM in particle synthesis, the nucleation and growth mechanisms of TPM emulsions are still poorly understood. We investigate droplet formation and growth of TPM in aqueous solutions under quiescent conditions. Our results show that in the absence of stirring the mechanisms of diffusion and stranding likely drive the spontaneous emulsification of TPM through the formation of co-soluble species during hydrolysis. In addition, turbidity and dynamic light scattering experiments show that the pH modulates the growth mechanism. At pH 10.1, the droplets grow via Ostwald ripening, while at pH 11.5, the droplets grow via monomer addition. Adding surfactants [Tween, sodium dodecyl sulfate (SDS), or cetyltrimethylammonium bromide] leads to <100 nm droplets that are kinetically stable. The growth of Tween droplets occurs through addition of TPM species while the number density of droplets is kept constant. In addition, in the presence of the ionic surfactant SDS, electrostatic repulsion between the solubilized TPM species and SDS leads to a significant increase in the number density of droplets as well as additional nucleation events. Finally, imaging of the solubilization of TPM in capillaries shows that in the absence of a surfactant, TPM hydrolysis is likely the rate-limiting step for emulsification, whereas the presence of silica particles in the aqueous phase likely acts as a catalyst of TPM hydrolysis. Our experiments highlight the importance of diffusion and solubilization of TPM species in the aqueous phase in the nucleation and growth of droplets.

Interactions between silica particles and model phospholipid monolayers

The rapid increase in the air pollution level observed in recent years is considered to be one of the main social and economic problems due to the strong direct influence on living organisms. From the point of view of proper prophylaxis, explanation of the mechanism of the impact of suspended dust particles (PMs ≤ 10 µm) on model biological membranes at the molecular level is becoming increasingly important. In this work, we present the effects of the quantity and distribution of solid silica particles on the properties of Langmuir monolayers formed by the main phospholipids of biological membranes, i.e. 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-ethanolamine (POPE). Dispersions of silica particles (0.1%, 1.0% and 2.5%) have been added to the DPPC or POPE to form a mixed monolayer and investigated using a combination of Langmuir trough technique and Brewster Angle Microscopy (BAM). This study shows that the presence of silica particles (PMs) affects the run of the surface pressure–area (π–A) isotherm, leading to a different phase behaviour of the monolayer and it also has an impact on the lipid membrane morphology. Moreover, relaxation experiments of the phospholipid-PMs monolayer were performed to determine the influence of both concentration and distribution of silica particles on the stability of phospholipid membrane.

The Use of Silica Microparticles to Improve the Efficiency of Optical Hyperthermia (OH).

Although optical hyperthermia could be a promising anticancer therapy, the need for high concentrations of light-absorbing metal nanoparticles and high-intensity lasers, or large exposure times, could discourage its use due to the toxicity that they could imply. In this article, we explore a possible role of silica microparticles that have high biocompatibility and that scatter light, when used in combination with conventional nanoparticles, to reduce those high concentrations of particles and/or those intense laser beams, in order to improve the biocompatibility of the overall procedure. Our underlying hypothesis is that the scattering of light caused by the microparticles would increase the optical density of the irradiated volume due to the production of multiple reflections of the incident light: the nanoparticles present in the same volume would absorb more energy from the laser than without the presence of silica particles, resulting either in higher heat production or in the need for less laser power or absorbing particles for the same required temperature rise. Testing this new optical hyperthermia procedure, based on the use of a mixture of silica and metallic particles, we have measured cell mortality in vitro experiments with murine glioma (CT-2A) and mouse osteoblastic (MC3T3-E1) cell lines. We have used gold nanorods (GNRs) that absorb light with a wavelength of 808 nm, which are conventional in optical hyperthermia, and silica microparticles spheres (hereinafter referred to as SMSs) with a diameter size to scatter the light of this wavelength. The obtained results confirm our initial hypothesis, because a high mortality rate is achieved with reduced concentrations of GNR. We found a difference in mortality between CT2A cancer cells and cells considered non-cancer MC3T3, maintaining the same conditions, which gives indications that this technique possibly improves the efficiency in the cell survival. This might be related with differences in the proliferation rate. Since the experiments were carried out in the 2D dimensions of the Petri dishes, due to sedimentation of the silica particles at the bottom, whilst light scattering is a 3D phenomenon, a large amount of the energy provided by the laser escapes outside the medium. Therefore, better results might be expected when applying this methodology in tissues, which are 3D structures, where the multiple reflections of light we believe will produce higher optical density in comparison to the conventional case of no using scattering particles. Accordingly, further studies deserve to be carried out in this line of work in order to improve the optical hyperthermia technique.

Electron paramagnetic resonance of sonicated powder suspensions in organic solvents

The chemical effects of the acoustic cavitation generated by ultrasound translates into the production of highly reactive radicals. Acoustic cavitation is widely explored in aqueous solutions but it remains poorly studied in organic liquids and in particular in liquid/solid media. However, several heterogeneous catalysis reactions take place in organic solvents.Thus, we sonicated trimethylene glycol and propylene glycol in the presence of silica particles (SiO2) of different sizes (5–15 nm, 0.2–0.3 µm, 12–26 µm) and amounts (0.5 wt% and 3 wt%) at an ultrasound frequency of 20 kHz to quantify the radicals generated. The spin trap 5,5-dimethyl-1-pyrrolin–N-oxide (DMPO) was used to trap the generated radicals for study by electron paramagnetic resonance (EPR) spectroscopy. We identified the trapped radical as the hydroxyalkyl radical adduct of DMPO, and we quantified it using stable radical 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) as a quantitation standard. The concentration of DMPO spin adducts in solutions containing silica size 12–26 µm was higher than the solution without particles. The presence of these particles increased the concentration of the acoustically generated radicals by a factor of 1.5 (29 µM for 0.5 wt% of SiO2 size 12–26 µm vs 19 µM for 0 wt%, after 60 min of sonication). Ultrasound produced fewest radicals in solutions with the smallest particles; the concentration of radical adducts was highest for SiO2 particle size 12–26 µm at 0.5 wt% loading, reaching 29 µM after 60 min sonication. Ultrasound power of 50.6 W produced more radicals than 24.7 W (23 µM and 18 µM, respectively, at 30 min sonication). Increased temperature during sonication generated more radical adducts in the medium (26 µM at 75 °C and 18 µM at 61 °C after 30 min sonication). Acoustic cavitation, in the presence of silica, increased the production of radical species in the studied organic medium.

Fluorescent Nanocomposites: Hollow Silica Microspheres with Embedded Carbon Dots.

Intrinsically fluorescent carbon dots may form the basis for a safer and more accurate sensor technology for digital counting in bioanalytical assays. This work presents a simple and inexpensive synthesis method for producing fluorescent carbon dots embedded in hollow silica particles. Hydrothermal treatment at low temperature (160 °C) of microporous silica particles in presence of urea and citric acid results in fluorescent, microporous and hollow nanocomposites with a surface area of 12 m2 /g. High absolute zeta potential (-44 mV) at neutral pH demonstrates the high electrosteric stability of the nanocomposites in aqueous solution. Their fluorescence emission at 445 nm is remarkably stable in aqueous dispersion under a wide pH range (3-12) and in the dried state. The biocompatibility of the composite particles is excellent, as the particles were found to show low genotoxicity at exposures up to 10 μg/cm2 .

Short-term oral administration of non-porous and mesoporous silica did not induce local or systemic toxicity in mice

In this study, two sets of methyl-coated non-porous and mesoporous amorphous silica materials of two target sizes (100 and 300 nm; 10–844 m2/g) were used to investigate the potential role of specific surface area (SSA) and porosity on the oral toxicity in mice. Female Swiss mice were administered by oral gavage for 5 consecutive days. Two silica dose levels (100 and 1000 mg/kg b.w.) were tested for all four materials. All dispersions were characterized by transmission electron microscopy (TEM) and Nanoparticle tracking analysis (NTA). Batch dispersions of porous silica were rather unstable due to agglomeration. Animals were sacrificed one day after the last administration or after a three-week recovery period. No relevant toxicological effects were induced by any of the silica materials tested, as evaluated by body weight, gross pathology, relative organ weights (liver, spleen, kidneys), hematology, blood biochemistry, genotoxicity (Comet assay in jejunum cells and micronucleus test in peripheral blood erythrocytes), liver and small intestine histopathology, and intestinal inflammation. The presence of silica particles in the intestine was evaluated by a hyperspectral imaging microscopy system (CytoViva) using histological samples of jejunum tissue. Silica spectral signatures were found in jejunum samples with all the treatments, but only statistically significant in one of the treatment groups.

Immunity to the Dual Threat of Silica Exposure and Mycobacterium tuberculosis.

Exposure to silica and the consequent development of silicosis are well-known health problems in countries with mining and other dust producing industries. Apart from its direct fibrotic effect on lung tissue, chronic and immunomodulatory character of silica causes susceptibility to tuberculosis (TB) leading to a significantly higher TB incidence in silica-exposed populations. The presence of silica particles in the lung and silicosis may facilitate initiation of tuberculous infection and progression to active TB, and exacerbate the course and outcome of TB, including prognosis and survival. However, the exact mechanisms of the involvement of silica in the pathological processes during mycobacterial infection are not yet fully understood. In this review, we focus on the host's immunological response to both silica and Mycobacterium tuberculosis, on agents of innate and adaptive immunity, and particularly on silica-induced immunological modifications in co-exposure that influence disease pathogenesis. We review what is known about the impact of silica and Mycobacterium tuberculosis or their co-exposure on the host's immune system, especially an impact that goes beyond an exclusive focus on macrophages as the first line of the defense. In both silicosis and TB, acquired immunity plays a major role in the restriction and/or elimination of pathogenic agents. Further research is needed to determine the effects of silica in adaptive immunity and in the pathogenesis of TB.

The effect of ionisation of silica nanoparticles on their binding to nonionic surfactants in oil–water system: an atomistic molecular dynamic study

ABSTRACTIn this study, the adsorption of nonionic surfactant, triethylene glycol monododecyl ether (C12E3), on a surface of silica nanoparticle (NP) has been studied with variation in the degree of ionisation (DI) of silica NP using all-atom molecular dynamic simulations in hexadecane–water system. Hydrogen bonding is found to be responsible for the adsorption of C12E3 on NP, particularly at low DI. We observe that with increasing DI of NP, the amount of adsorption of C12E3 on NP reduces, which is negligible beyond DI ∼ 0.5. The decrease in the adsorption with increasing DI is due to the decrease in the number of hydrogen bonds formed by the silica NP with surfactant molecules. Potential of mean force (PMF) profiles indicate attractive interactions between NP and C12E3 for DI < 0.5, and for larger DI depletion effect is observed. This work explains the unusual effect of nonionic surfactant on interfacial tension in the presence of silica particles as observed in recent experiments.

Foam and thin films of hydrophilic silica particles modified by β-casein

HypothesisFoaming properties of particle dispersions can be modified by addition of amphiphiles. The molar ratio between particles and amphiphiles will influence the wetting properties of the particles as well as the bulk concentration of the amphiphiles. This will have an effect on air/water interfacial composition as well as on the thin film and foam stability of the mixed system. ExperimentsIn this research foams and thin films of hydrophilic silica particles in presence of β-casein (β-CN) were investigated with different particle sizes and varying β-CN/silica weight ratios (between 1:10 and 1:100). Samples were characterized for particles size, morphology as well as contact angle and related to their foaming, interfacial, and thin film properties. FindingsA threshold weight ratio of β-CN/silica was found to be 1:50 for foam stabilization with mixtures containing silica particles no larger than 1 μm and 1:30 for film stabilization with mixtures containing larger particles. At the interface, the modified silica particles were rather diluted without much interaction for surface compressions up to 30%. Large silica particles (0.0015% β-CN, Csilica ≤ 0.15%) were dragged to the periphery of the thin liquid films but no decrease of the inner film draining rate by a decrease of capilary pressure gradient across the film was observed. The depletion of β-casein in the bulk by particles played a major role in foam destabilization.

Unusual Interfacial Freezing Phenomena in Hexacontane/Silica Composites.

The crystallization behaviors of n-hexacontane (C60H122)/Stöber silica (SiO2) composites with various compositions were investigated by a combination of differential scanning calorimetry (DSC), solid-state 13C nuclear magnetic resonance (solid-state 13C NMR), and proton NMR relaxation experiments. By means of DSC, C60H122 molecules in C60H122/silica composites were observed to be involved in the interfacial freezing not present in the free bulk C60H122. The orientation of C60H122 molecules, being preferentially normal to silica surface, was confirmed by grazing incidence X-ray diffraction experiments on thin n-hexacontane film adsorbed on the silicon wafer with a native SiO2 layer. Inferred from the solid 13C NMR data, the interfacial monolayer is in orthorhombic phase with certain chain disorders. It is speculated that the "interfacial freezing" of C60H122 formed in the presence of silica particles is driven by the combination of the strong attraction between the molecules and the enhanced number of interfacial molecules on the silica surface.

DEVELOPMENT OF HIGH PERFORMANCE RUBBER COMPOSITES FROM ALKOXIDE-BASED SILICA AND SOLUTION STYRENE–BUTADIENE RUBBER

ABSTRACT The solution SBR and silica-based composites are prepared by hydrolysis of tetraethylorthosilicate in the presence of an organic solution of SBR and n-butylamine as catalyst. Further addition of bis[3-(triethoxysilyl)propyl]tetrasulfide, a silane coupling agent, improves the performance and properties of the composites. All the results are compared with commercial precipitated silica at similar loading conditions. The generated silica particles from this alkoxide route resulted in lower Mooney viscosity of the compound and showed less filler flocculation compared with standard commercial precipitated silica in reference compounds. A detailed dynamic mechanical study also indicated that alkoxide silica in model tire compounds could offer a lower rolling resistance and a higher wet skid resistance compared to the reference. Other properties such as heat build-up, rebound resilience, and hysteresis loss were found to be very promising for alkoxide silica composites, too. The silica particles (aggregated) developed by the alkoxide method were relatively large (∼150–200 nm) compared with the primary particles of precipitated commercial silica. The synthesis of sol–gel silica particles in presence of the polymer allowed for the trapping of some polymer molecules inside the filler aggregates and therefore offers exceptional mechanical reinforcement of the rubber.

Polymer-silica nanocomposite membranes for CO2 capturing

Reducing carbon dioxide (CO2) is an area of great interest in current international efforts geared toward lowering emissions and combating global warming. In this work, amino-silica composite membranes were prepared and used to capture carbon dioxide. The surface of silica particles was chemically modified with amine to efficiently capture carbon dioxide. The phase separation technique was used to prepare the membranes from a composite containing polyvinylidene-fluoride-hexafluoropropylene (PVDF-HFP), amino-silica particles, acetone and water. SEM images revealed that the membranes composed of multilayers of porous polymer uniformly impregnated with silica particles. Both XRD and FTIR results have validated the perfect integration of silica particles within the polymeric network. The mechanical properties of the membrane are improved by the presence of silica particles as proved by the high tensile strength value (1.5N/cm2) obtained for the PVDF-HFP/SiO2 membrane compared to 0.9N/cm2 obtained for bare PVDF-HFP membrane. Also, we succeeded in recording SEM images to show that the plastic deformation of the film is associated with the formation of macro-holes. To the best of our knowledge this is the first time for such results to be monitored with SEM to observe the macroscopic evolution of the structure. Additionally, the surface area was significantly increased from 3.8m2/g for bare PVDF-HFP membrane to 116.4m2/g for PVDF-HFP impregnated with silica particles. Moreover, the CO2 separation efficiency depends on both surface area and the quantity of amino-SiO2 added to the membrane. The addition of amino-silica particles leads to a significant uptake of carbon dioxide compared to non-modified polymer membrane. The results obtained indicated that combing the phase separation with amino silica particles provided a cost-effective route to scaling up the synthesis of membranes that were mechanically stable and highly efficient at CO2 capture.

Surface-anchored counterions on weak chiral anion-exchangers accelerate separations and improve their compatibility for mass-spectrometry-hyphenation

In the present work we propose new variants of chiral stationary phases (CSP) with tert-butylcarbamoylquinine (tBuCQN) as chiral selector molecule. Four tBuCQN-CSPs with distinct bonding chemistries are compared in terms of their pH-dependent surface charge by ζ-potential determinations, by achiral and chiral liquid chromatographic tests and LC–ESI–MS hyphenation. In one embodiment tBuCQN was immobilized on 3-mercaptopropylmethylsilyl-modified silica by thiol-ene click reaction (brush type CSP with selector coverage of 0.38mmol/g). In another embodiment, poly-(3-mercaptopropyl)-methylsiloxane was coated onto vinylized silica particles in presence of tBuCQN and radical initiator. The tBuCQN selector was then immobilized onto the polysiloxane film which in turn was crosslinked to the vinyl-surface in a simultaneous double click reaction leading to a CSP with enhanced stability due to multiple linkages (0.29mmol/g tBuCQN). Aliquots of each of the two CSPs were further modified by oxidation of free residual thiol groups to sulfonic acid functionalities to obtain strongly acidic endcapping groups which act as immobilized counterions of the chiral WAX CSPs (0.2mmol/g sulfonic acid co-ligands for brush type CSP). This caused secondary repulsive interactions, hence balanced interactions of the target analytes (chiral acids) at the WAX site and decreased non-specific interactions. Furthermore, this rendered possible the use of milder elution conditions, i.e. lower ionic strength, for acidic compounds. Separation performance was maintained and slightly improved, respectively, when using polar organic or reversed-phase type elution mode in chiral separations which were significantly accelerated (isoeluotropic conditions could be achieved with ca. factor 40 lower counterion concentration in the mobile phase). Thus, LC–ESI–MS enantiomer separations could be readily performed at very low ionic strength conditions (10mM acetate) which is favorable due to less ion suppression. In addition to this the newly developed stationary phases showed complementary retention profiles in RP- and HILIC-mode which make these type of stationary phases also promising tools for achiral applications in pharmaceutical analysis, especially as orthogonal separation principle e.g. in 2D-LC and impurity profiling.

Thermo-responsive hydrogels containing mesoporous silica toward controlled and sustainable releases

Here we prepare thermo-responsive hydrogel containing mesoporous silica (KIT-6) with high surface area. Our hybrid hydrogel is prepared by gelation of NIPAM monomer with mesoporous silica particles in presence of cross linker. Owing to the doped mesoporous silica, a large amount of guest molecules are adsorbed easily. With increase of temperature, the hybrid hydrogel shrinks to retard the release of guest molecules.

Facile Preparation of Litchi-Like Polystyrene-Silica Hybrid Particles via Dispersion Polymerization

The composite particles with litchi-like morphologies attributing to the combination of inorganic silica seed and polymer nodules were synthesized successfully using a modified dispersion polymerization method. Dispersion polymerization of styrene was achieved in the presence of silica particles and the formed polystyrene nanoparticles were absorbed onto the surface of silica particles. The effects of the adding amount of St monomer on the particle morphologies was investigated.

Force interactions between magnetite, silica, and bentonite studied with atomic force microscopy

Iron ore pellets consist of variety of mineral particles and are an important refined product used in steel manufacturing. Production of high-quality pellets requires good understanding of interactions between different constituents, such as magnetite, gangue residues, bentonite, and additives. Much research has been reported on magnetite, silica, and bentonite surface properties and their effect on pellet strength but more scant with a focus on a fundamental particle–particle interaction. To probe such particle interaction, atomic force microscopy (AFM) using colloidal probe technique has proven to be a suitable tool. In this work, the measurements were performed between magnetite–magnetite, bentonite–magnetite, silica–bentonite, and silica–magnetite particles in 1 mM CaCl2 solution at various pH values. The interaction character, i.e., repulsion or attraction, was determined by measuring and analyzing AFM force curves. The observed quantitative changes in interaction forces were in good agreement with the measured zeta-potentials for the particles at the same experimental conditions. Particle aggregation was studied by measuring the adhesion force. Absolute values of adhesion forces for different systems could not be compared due to the difference in particle size and contact geometry. Therefore, the relative change of adhesion force between pH 6 and 10 was used for comparison. The adhesion force decreased for the magnetite–magnetite and bentonite–silica systems and slightly increased for the magnetite–bentonite system at pH 10 as compared to pH 6, whereas a pronounced decrease in adhesion force was observed in the magnetite–silica system. Thus, the presence of silica particles on the magnetite surface could have a negative impact on the interaction between magnetite and bentonite in balling due to the reduction of the adhesion force.