Novel Synthesis, Characterization and Amoxicillin Release Study of pH-Sensitive Nanosilica/Poly(acrylic acid) Macroporous Hydrogel with High Swelling

The effect of SiO2 nanoparticles on the formation of PAA (poly acrylic acid) gel structure was investigated with seeded emulsion polymerization method used to prepare SiO2/PAA nanoparticles. The morphologies of the nanocomposite nanoparticles were studied by transmission electron microscopy (TEM). Fourier-transform infrared (FTIR) spectroscopy results indicated that the PAA was chemically bonded to the surface of the SiO2 nanoparticles. Additionally, the resulting morphology of the nanocomposite nanoparticles confirmed the co-crosslinking role of the SiO2 nanoparticles in the formation of the 3D structure and hydrogel of PAA. SiO2/PAA nanocomposite hydrogels were synthesized by in situ solution polymerization with and without toluene. The morphology studies by field emission scanning electron microscopy (FESEM) showed that when the toluene was used as a pore forming agent in the polymerization process, a macroporous hydrogel structure was achieved. The pH-sensitive swelling behaviors of the nanocomposite hydrogels showed that the formation of pores in the gels structure was a dominant factor on the water absorption capacity. In the current research the absorption capacity was changed from about 500 to 4000 g water/g dry hydrogel. Finally, the macroporous nanocomposite hydrogel sample was tested as an amoxicillin release system in buffer solutions with pHs of 3, 7.2, and 9 at 37 °C. The results showed that the percentage cumulative release of amoxicillin from the hydrogels was higher in neutral and basic mediums than in the acidic medium and the amoxicillin release rate was decreased with increasing pH. Additionally, the release results were very similar to swelling results and hence amoxicillin release was a swelling controlled-release system.

The investigation of the average diameter of the SiO2 nanoparticles effect on the oil displacing efficiency from the pore in the rock formation using nanosuspension as a displacing agent

The numerical investigation of the nanofluid flow, which displaced the oil, in a microchannel was carried out. The effect of the average diameter of the SiO2 nanoparticles on the oil displacing efficiency by nanofluids for different sizes of microchannel at various Reynolds numbers was studied. A T-shaped microchannel with a vertical channel, called a pore channel, which imitated the pore in the rock formation was considered as a computational domain. The main flow channel width and height were 200 µm. The width and height of the pore channel were varied in the range from 100 µm to 800 µm. The Reynolds number varied from 0.1 to 100. The oil recovery coefficient, which is defined as the ratio of the displacing volume of oil from the pore to the volume of the pore was considered as the main studied characteristic. The nanofluid is considered a single-phase fluid with experimentally obtained properties. The mass concentration of SiO2 nanoparticles was 0.5%. The average diameters of nanoparticles were 5 nm, 18 nm, and 50 nm. It was found, that the oil recovery coefficient increased with a decrease in the average diameter of nanoparticles. It was obtained that the nanofluid can enhance the oil recovery several times compared to pure water.

Shear Bond Strength of Self-Adhesive Composite Containing TiO2 and SiO2 Nanoparticles with an Additional Etching Step for Orthodontic Brackets Bonding to Enamel

Introduction: Recently, nanoparticles such as nano-TiO2 have been added to some dental materials for enhancing dental carries prevention due to their antibacterial activity. Aim: This study aimed to assess the shear bond strength of a self-adhesive composite containing TiO2 and SiO2 nanoparticles for orthodontic bracket bonding. Materials and methods: This in vitro, experimental study was done on 70 extracted human premolars divided into 7 groups. Six groups of Vertise Flow self-adhesive composite samples were prepared: without any nanoparticles, with 0.5% and 1% TiO2 nanoparticles, 0.5% and 1% SiO2 nanoparticles, and 1% mixture of TiO2 and SiO2 nanoparticles so that nano-hybrid composites were prepared. Metal brackets were bonded with these samples as well as Transbond XT as the control group. The shear bond strength of the brackets to enamel was measured using a universal testing machine. The adhesive remnant index (ARI) score was also determined by a stereomicroscope. Data were analyzed by one-way ANOVA, Tukey&rsquo;s test and Kruskal-Wallis test. Results: The shear bond strength of the groups was significantly different (p=0.000). Pairwise comparisons revealed that the bond strength of Transbond XT group was significantly higher than others (p<0.05), followed by the 1% TiO2 group with significant differences with Vertise Flow and 0.5% TiO2 groups. The lowest value belonged to Vertise Flow with no nanoparticles. The ARI scores was different in the control group (p=0.000). Conclusions: Adding TiO2 and SiO2 nanoparticles to Vertise Flow self-adhesive composite not only did not adversely affect its shear bond strength, but also slightly increased it. Overall, the self-adhesive nano-hybrid composite containing TiO2 and/or SiO2 nanoparticles, following an additional etching step would be acceptable for bracket bonding and can be used clinically to benefit from the antimicrobial activity of these nanoparticles.

Robust and Highly Stretchable Chitosan Nanofiber/Alumina-Coated Silica/Carboxylated Poly (Vinyl Alcohol)/Borax Composite Hydrogels Constructed by Multiple Crosslinking

We investigated the mechanical and structural properties of composite hydrogels composed of chitosan nanofiber (ChsNF), positively charged alumina-coated silica (ac-SiO2) nanoparticles, carboxylated poly (vinyl alcohol) (cPVA), and borax. ChsNF/cPVA/borax hydrogels without ac-SiO2 exhibited high Young’s modulus but poor elongation, whereas cPVA/ac-SiO2/borax hydrogels without ChsNF had moderate Young’s modulus but high elongation. ChsNF/ac-SiO2/cPVA/borax hydrogels using both ChsNF and ac-SiO2 as reinforcement agents exhibited high extensibility (930%) and high Young′s modulus beyond 1 MPa at a high ac-SiO2 concentration. The network was formed by multiple crosslinking such as the complexation between borate and cPVA, the ionic complexation between ac-SiO2 and cPVA, and the hydrogen bond between ChsNF and cPVA. Structural analysis by synchrotron small-angle X-ray scattering revealed that the nanostructural inhomogeneity in ChsNF/ac-SiO2/cPVA/borax hydrogel was suppressed compared to those of the ChsNF/cPVA/borax and cPVA/ac-SiO2/borax hydrogels.

Preparation of Dual-Layered Core–Shell Fe3O4@SiO2 Nanoparticles and Their Properties of Plasmid DNA Purification

The rapid purification of biomaterials such as DNA, RNA, and antibodies has attracted extensive attention, and research interest has increased further with the COVID-19 pandemic. In particular, core–shell-structured superparamagnetic nanoparticles have been continuously studied for their application as biopurification materials. It has been reported that Fe3O4@SiO2 nanoparticles are one of the most promising candidates for separating nucleic acids via a simple and rapid process. This study proposed a fabrication method for dual-layered Fe3O4@SiO2 nanoparticles, in which the density of the SiO2 shell was controlled using an intermediate surfactant during the SiO2 coating. After the fabrication of dual-layered Fe3O4@SiO2 nanoparticles, structural, morphological, and magnetic analyses were conducted. The results showed that the Fe3O4 nanoparticles were surrounded by a dense layer 15.6~27.9 nm thick and a porous layer 24.2~44.4 nm thick, and had superparamagnetic properties with high saturated magnetization at room temperature (86.9 emu/g). Then, the optimal conditions for the biopurification material were suggested based on analysis of the selective separation of plasmid DNA.

SONOLUMINESCENCE SPECTROSCOPY OF COLLOIDAL SUSPENSIONS: MOLECULAR, IONIC AND ATOMIC LUMINESCENCE DURING SONOCHEMICAL DECOMPOSITION OF SILICON DIOXIDE NANOPARTICLES CONTAINING RUTHENIUM AND COPPER COMPOUNDS

The article is devoted to an example of the sonoluminescence spectroscopy use, which was previously known as a method for analyzing substances from the characteristic spectra of their sonoluminescence only in true solutions, for carrying out a similar analysis of substances contained in insoluble nanoparticles in colloidal suspensions. The solutions sonolysis, that is, their irradiation with ultrasound, is accompanied by the formation of cavitation bubbles that vibrate radially at the frequency of the ultrasonic field. Volatile components of the solution enter the bubbles, evaporating from the liquid-gas interface; nonvolatile components can penetrate into the bubble as a result of the injection of solution nanodroplets into the gas phase, which occurs during intense bubble movements accompanied by their deformation. In a nonequilibrium plasma periodically forming in cavitation bubbles, destruction occurs, as well as collisional excitation of these components, followed by luminescence. It has been shown that this mechanism of sonoluminescence also operates in colloidal suspensions, where substances are present in the form of nanoparticles with sizes less than 50 nm. Such nanoparticles penetrate into moving cavitation bubbles, without destroying them, as part of nanodroplets, and then undergo decomposition in bubble plasma with the excited particles generation as emitters of characteristic sonoluminescence. In this work, we synthesized colloidal suspensions in dodecane of porous SiO2 nanoparticles containing adsorbed Ru(bpy)3Cl2 and CuSO4 salts. During moving single-bubble sonolysis for these suspensions, characteristic emission spectra of Ru and Cu atoms, SiO molecules, and Ru(bpy)3 ions suitable for sonoluminescence spectroscopic analysis were recorded. By comparing the experimental and calculated (at different temperatures) luminescence spectra of Ru atoms, we estimated the electron temperature attained upon acoustic compression of single bubble in colloidal suspension in dodecane: Te = 7000 K.

Enhanced Foam Stability Using Nanoparticle in High Salinity High Temperature Condition for Eor Application

The capability of commercial nanoparticles to perform as foam stabilizer were investigated at reservoir temperature of 96°C. Al2O3, Fe3O4, Co3O4, CuO, MgO, NiO, ZrO2, ZnO and SiO2 nanoparticles that were characterized using XRD, FTIR, FESEM-EDX, TEM and PSA, were blended in the in-house formulated surfactant named IVF respectively at a particular ratio. The test was performed with and without the presence of reservoir crude oil. Results showed that formulation with nanoparticles enhanced foam stability by having longer foam half-life than the IVF surfactant alone, especially in the absence of oil. Only SiO2 nanoparticles were observed to have improved the foam stability in both test conditions. The unique properties of SiO2 as a semi-metal oxide material may have contributed to the insensitivity of SiO2 nanoparticle towards crude oil which is known as a foam destabilizer. The physical barrier that was formed by SiO2 nanoparticles at the foam lamella were probably unaffected by the presence of crude oil, thus allowing the foams to maintain its stability. In thermal stability tests, we observed the instability of all nanoparticles in the IVF formulation at 96°C. Nanoparticles were observed to have separated and settled within 24 hours. Therefore, surface modification of nanoparticle was done to establish steric stabilization by grafting macro-molecule of polymer onto the surface of SiO2. This in-house developed polymer grafted silica nanoparticles are named ZPG nanoparticles. The ZPG nanoparticles passed the thermal stability test at 96°C for a duration of 3 months. In the foam wetness analysis, ZPG nanoparticles were observed to have produced more wet foams than IVF formulation alone, indicating that ZPG is suitable to be used as foam stabilizer for EOR process as it showed catalytic behaviour and thermally well-stable at reservoir temperature.