Surface Of SiO2 Nanoparticles Research Articles

Heavy oil recovery by surface modified silica nanoparticle/HPAM nanofluids

Recent studies showed that the presence of dispersed nanoparticles (NPs) can increase the efficiency of polymer flooding. The network structure of polymer/NP hybrid dispersion has a significant impact on oil recovery. In this work, the surface of SiO2 NPs was modified by chemical grafting of octyltriethoxysilane (SiO2-OTES), oleic acid (SiO2-OAA) and stearic acid (SiO2-SAA) in an attempt to stimulate higher degree of interaction with partially hydrolyzed polyacrylamide (HPAM). Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and Fourier transform infrared (FTIR) spectroscopy were employed to characterize the modified silica NPs. In addition, ζ-potential, cryo-scanning electron microscopy (cryo-SEM), and linear and nonlinear rheology were used to evaluate the characteristics of the hybrid dispersion of HPAM/unmodified and modified SiO2 NPs. ζ-potential measurements showed that the addition of HPAM improved the colloidal stability of the modified and unmodified SiO2 NPs dispersed in deionized (DI) water. Moreover, the addition of HPAM reduced the size of the NP aggregates by effective steric repulsion. Small and large shear oscillatory deformation results showed that SiO2-OTES NPs improved the HPAM network significantly. Nevertheless, HPAM/NPs network formed with all the different SiO2 NPs severely decreased the intra-cycle shear-thickening behavior of the polymer. Lastly, the addition of 0.2 wt% SiO2-OTES NPs to the HPAM solution increased the ultimate oil recovery from 71.4% to 75.7% OOIP.

The effect of salts in aqueous media on the formation of the BSA corona on SiO2 nanoparticles

Protein-nanoparticle interactions are garnering attention due to their potential impacts on human health and environmental contamination. The colloidal properties of nanoparticles (NPs) in aqueous media may differ in the presence of natural materials such as salts and proteins. In this study, the interactions between bovine serum albumin (BSA) and fumed hydrophilic silicon dioxide (SiO2) NPs were studied in aqueous solutions under variable pH or ion composition. Investigation of hydrodynamic diameter and zeta potential changes to nanoparticles upon addition of BSA, the adsorption of BSA to the SiO2 NP surface, and the interaction energy between particles revealed that buffered solutions promote protein adsorption onto NPs and particle agglomeration. The effects of ionic salt solutions were dependent on the ion charge, with negatively charged ions stabilizing the system and positively charged ions promoting protein-nanoparticle interactions. These data highlight that physiologically relevant salts affect protein corona formation on non-toxic, amorphous SiO2 NPs and spur the need for well-defined characterization conditions when determining potential toxicity of NPs upon human or animal exposure.

Fabrication of a novel polyvinylidene fluoride membrane via binding SiO2 nanoparticles and a copper ferrocyanide layer onto a membrane surface for selective removal of cesium.

A novel polyvinylidene fluoride (PVDF) membrane was fabricated through chemical binding SiO2 nanoparticles (NPs) and copper ferrocyanide (CuFC) layers onto a membrane surface simultaneously to improve the removal efficiency of Cs. The results indicated that the SiO2 NPs were strongly deposited onto the membrane surface, and the CuFC layer was firmly attached on the surface of SiO2 NPs and the membrane. CuFC/SiO2/PVDF membrane remained stable after the acidic solution and sonication stress treatments. CuFC/SiO2/PVDF membrane showed good permeate flux and high selectivity on removal of Cs, and adsorbing capacity reached 1440.4 mg m-2 for Cs. The membrane remained high rejections of Cs in a wide pH, and could be regenerated well by H2O2 and N2H4. Selective adsorption and electrostatic interaction govern the rejection of Cs. The coexisting cations decreased the rejection of Cs mainly in accordance to the order of cations' hydration radii as K+ > Na+ > Ca2+ > Mg2+. In addition, the rejection of Cs could still reach 99.4% in 8 h in the filtration of humic acid solution and natural surface water. The membrane could removal of Cs from water effectively by directly rapid filtration, suggesting it can be applied as promising technology for radioactive wastewater treatment.

Preparation and characterization of modified SiO2 nanospheres with dichlorodimethylsilane and phenyltrimethoxysilane

In this study we synthesized spherical nanosilica by the Sol-Gel method using tetraethyl orthosilicate (TEOS), and the average particle diameter was measured by scanning electron microscopy (SEM). The surface of silica nanoparticles was modified with two kinds of silane coupling agents: dichlorodimethylsilane (DCDMS) and phenyltrimethoxysilane (PhTMS). We investigated the effect of the type of silane coupling agent with different functional groups (alkoxy or chloro) on the surface properties of modified silica by various analytical methods, i.e., FT-IR spectroscopy, CHN analysis, UV-visible spectra and thermogravimetric analysis (TGA) measurements. The particles modified with DCDMS showed larger grafting density from CHN analysis and higher weight loss from TGA measurement indicating the higher content of silane grafted on the surface of SiO2 nanoparticles. We suggest that the variations in grafting were dependent on the silane condensation which indicating the greater ability of condensation reaction of DCDMS with OH groups of silica rather than PhTMS.

Relaxation Processes at Interfaces in Polymer Nanocomposites

Polymer nanocomposites (PNC) where nanofillers such as nanoparticles and nanotubes are dispersed show better mechanical, electric and dielectric properties in comparison with the neat polymer matrix. The improvement of the properties is strongly dependent on the formation of interfacial regions between fillers and matrix polymer chains. A core-shell model [1], in which each nanofiller (core) is supposed to be covered with an interfacial polymer layer (shell) with slower dynamics than the bulk one, has been widely used to rationalize the property improvement. When the nanofiller fraction increases above a percolation threshold, the presence of nanofiller network can lead to the formation of interfacial regions with hierarchical dynamics. A quantitative understanding of the hierarchical nature in the relaxation dynamics of interfacial chains is critical for tailoring multiple properties of PNCs. In this study, the relaxation dynamics of a model rubber nanocomposite, nitrile-butadiene rubber (NBR) with silica (SiO2) nanoparticles, was characterized over broad temperature and frequency ranges by means of dielectric relaxation spectroscopy (DRS). As samples, NBR with a number-average molecular weight of 81.9k, a polydispersity index of 3.56 and a glass transition temperature (T g) of 242 K, and SiO2 nanoparticles with an average diameter of 18 nm, and their composites were kindly provided by Bridgestone Co., Ltd.. The weight content of acrylonitrile component in NBR was 34%, and the volume fraction of SiO2 nanoparticle in PNC (Φ) was varied from ~5 to ~30%. For DRS measurements, neat NBR and PNC films were prepared by a spin-coating method from tetrahydrofuran solutions onto quartz substrates coated with a 50 nm-thick Al layer. The films were dried in vacuum for 24 h at room temperature, and then a second 50 nm-thick Al layer was deposited on the surface of each film to form a parallel-plate capacitor. DRS measurements were conducted using a frequency response analyzer over the range from 10-1 to 106 Hz. Panels (a) and (b) of Figure 1 show representative examples of SEM images for PNC samples with Φ = 7 and 17 vol%, respectively. For the PNC sample with Φ = 7 vol%, SiO2 agglomerates with different sizes were distributed in the NBR matrix without the formation of long-range particle-particle structured network. In contrast, at Φ = 17 vol%, the SiO2 agglomerates tended to connect each other to form a long-range particle-particle network. This behavior has been experimentally confirmed in many nanocomposite systems. However, for a moment, it remains challenging to discuss a relationship between the particle-particle network and the relaxation dynamics of interfacial polymers. Panel (c) of Figure 1 shows dielectric loss (ε″) spectra for the neat NBR and PNCs as a function of frequency measured at 262 K. A strong peak representing the segmental relaxation process of NBR chains was observed around 5×102 Hz for each sample [2]. However, comparing with the neat NBR, the peak for the PNCs exhibited a decrease in amplitude and broadening on the low-frequency side. This trend became more remarkable for samples with higher Φ. This suggests the existence of a second relaxation process which represents the relaxation dynamics of the polymer shell layer surrounding SiO2 nanoparticle surface [1]. The ε′′ data for the neat NBR could be well fit using a Havriliak-Negami (HN) function with a single relaxation process [2]. However, a HN function with double relaxation processes and a conductivity term were necessary to well express the ε′′ data for the NBR-SiO2 films. The relaxation process of the shell layer was found to be slower than that of the bulk process by approximately two decades and almost independent of Φ. Panel (d) of Figure 1 shows temperature dependence of ε″. For all samples, a peak assignable to the segmental relaxation process was observed around 262 K. For the PNC films with Φ = 17 and 29 vol%, an additional peak was observed at a temperature higher than that for the bulk segmental relaxation peak by 50 ~ 80 K. The temperature elevation was more remarkable for the PNC sample with Φ = 29 vol%. Although the origin of this relaxation process can be hardly concluded, it seems reasonable to consider that it is arisen from slowed dynamics for chains restricted on the surface of SiO2 nanoparticles. [1] S. Cheng, S. Mirigian, J.-M. Y. Carrillo, V. Bocharova, B. G. Sumpter, K. S. Schweizer, and A. P. Sokolov, J. Chem. Phys. 143, 194704 (2015). [2] H. K. Nguyen, A. Konomi, S. Sugimoto, M. Inutsuka, D. Kawaguchi, and K. Tanaka, Macromol. Chem. Phys. 219, 1700329 (2018). Figure 1

SiO2 nanoparticle-assisted low-concentration viscoelastic cationic surfactant fracturing fluid

Attributing to its advantages including no residue, low friction and complete gel breaking, viscoelastic surfactant (VES) fracturing fluids are attracting more and more attention. However, high price and high consumption restrict the wide applications of VES. SiO2 nanoparticle-assisted VES fracturing fluid (NAVES) with low concentration is proposed in this study. The NAVES system consisting of 1% EDAA and 0.01% SiO2 maintains a shear viscosity of above 33 mPa·s at 70 °C for 2 h; in contrast, the viscosity of a 1% EDAA (VES) solution is 24 mPa·s at 70 °C for 2 h. This could be attributing to the formation of a strong dynamic network structure, in which the surfactant micelles attach to the surface of SiO2 nano-particles that are negatively charged through electrostatic interactions. The pseudo-crosslinking between the SiO2 and micelles also improves the shear resistance and relaxation time of the VES, without affecting the gel breaking performance. The NAVES system could break completely within 100 min, as reflected by the fact that its viscosity decreased to less than 3 mPa·s. The settling rate of quartz sand in an EDAA/SiO2 system at 25 °C was 0.0021 cm/s, which was lower than that of traditional VES fracturing fluid. Therefore, NAVES could serve as a low-concentration hydraulic fracturing fluid. In addition, the current study provides a cost-effective approach for hydraulic fracturing.

A facile approach to synthesize microencapsulated phase change materials embedded with silver nanoparicle for both thermal energy storage and antimicrobial purpose

In this study, a facile approach having the advantages of high efficiency and low-energy consumption for synthesis of microencapsulated phase change materials (MicroPCMs) with thermal energy storage and antimicrobial properties was demonstrated. Phase change materials (PCMs) was firstly encapsulated via the photocurable pickering emulsion polymerization technique, and then followed by silver reduction. The resulting microcapsules exhibited an excellent spherical morphology, narrow particle size distribution and a well-defined core-shell structure. The chemical composition and surface elemental distribution of Ag/SiO2-MicroPCMs were confirmed by the FTIR and EDS. The TEM observations indicated that Ag nanoparticles have been successfully attached on the surface of SiO2 nanoparticles. In addition, the results obtained from DSC and TGA indicated that the microcapsules achieved a good latent-heat storage capability, enhanced thermal reliability and stability. More importantly, Ag/SiO2-MicroPCMs was eventually combined with PVA hydrogel to prepare an antibacterial and thermoregulation composite material. As expected, the composite material obtained an excellent bactericidal properties, especially for Staphylococcus aureus. Furthermore, this composite material was also endowed with thermoregulation properties, due to the inherent latent heat storage characteristic of Ag/SiO2-MicroPCMs. It can be concluded that the microcapsules developed in this work show great potential in applications for thermal energy storage, food preservation, wound dressing, and etc.

Binding sites and structure of peptides bound to SiO2 nanoparticles studied by solution NMR spectroscopy

Understanding the mechanism of the interaction between inorganic materials and peptides is important for the development of organic/inorganic hybrid materials. The titanium-binding peptide (TBP; Arg1-Lys2-Leu3-Pro4-Asp5-Ala6) has been reported to possess a high binding affinity to SiO2 as well as TiO2 surfaces. Here, we report the binding modes and mechanism of the TBP to SiO2 nanoparticles. To accomplish this objective, we analyzed the binding sites of the TBP to a SiO2 surface and the structure of the TBP bound to the SiO2 using solution NMR spectroscopy. Saturation transfer difference (STD) NMR analysis was performed to identify the TBP sites that interact with the SiO2 surface, and then Arg1 and Asp5 were identified to be in close contact with the SiO2 surface. The structure of the TBP bound to SiO2 was well defined, and the Arg1 and Asp5 side chains face in the same direction. The combination of these results validates that the guanidyl group of Arg1 and the carboxyl group of Asp5 interact electrostatically with the silanol groups SiO− and SiOH2+ on the SiO2 surface, respectively. The binding mode of TBP/SiO2 was found to be different from that of the TBP/TiO2 system, which has been previously reported. Saturation transfer difference (STD) NMR analysis was performed to identify the titanium-binding peptide (TBP) sites that interact with the SiO2 nanoparticle surface, and then Arg1 and Asp5 were identified to be in close contact with the surface. The structure of the TBP bound to SiO2 determined by the NOESY measurement was well defined, and the Arg1 and Asp5 side chains face in the same direction. These results validates that the NH2+ of Arg1 and the COO− of Asp5 interact electrostatically with the SiO− and SiOH2+ on the SiO2 surface, respectively.

Molecularly imprinted polymers-based electrochemical DNA biosensor for the determination of BRCA-1 amplified by SiO2@Ag

A novel electrochemical DNA (E-DNA) biosensing strategy was designed and used for the detection of breast cancer susceptibility gene (BRCA-1). The biosensor was based on gold nanoparticles-reduced graphene oxide (AuNPs-GO) modified glass carbon electrode (GCE) covered with the layer of molecularly imprinted polymers (MIPs) synthesized with rhodamine B (RhB) as template, methacrylic acid (MAA) as the monomer, and Nafion as additive. The signal amplification tracing tag SiO2@Ag NPs were prepared by covering AgNPs on the surface of SiO2 nanoparticles in situ, and then DNA probes were modified on AgNPs by Ag-S bond, forming the composites SiO2@Ag/DNA. In presence of target DNA (T-DNA), homogeneous hybridization was performed with SiO2@Ag/DNA and RhB labeled DNA, and the resulting SiO2@Ag/dsDNA/RhB was specifically recognized by MIPs via the interaction between imprinting cavities and RhB. Under optimal conditions, the proposed biosensor exhibited wide linear range from 10 fM to 100 nM, low detection limit of 2.53 fM (S/N = 3), excellent selectivity, reproducibility, stability, and feasibility in serum analysis. Overall, these findings suggest the promising prospects of the proposed biosensing strategy in clinical diagnostics.

Luminescent SiO2 nanoparticles for cell labelling: Combined water dispersion polymerization and 3D condensation controlled by oligoperoxide surfactant-initiator

Hybrid polymer coated silica nanoparticles (NPs) were synthesized using low temperature graft (co)polymerization of trimethoxysilane propyl methacrylate (MPTS) initiated by surface-active oligoperoxide metal complex (OMC) in aqueous media. These NPs were characterized by means of kinetic, solid-state NMR, TEM and FTIR techniques. Two processes, namely the radical graft-copolymerization due to presence of double bonds and 3D polycondensation provided by the intra- or/and intermolecular interaction of organosilicic fragments, occurred simultaneously. The relative contribution of the reactions depending on initiator concentration and pH value leading to the formation of low cured polydisperse microparticles or OMC coated SiO2 NPs of controlled curing degree was studied. The availability of free-radical forming peroxide fragments on the surface of SiO2 NPs provides an opportunity for seeded polymerization leading to the formation of the functional polymer coated NPs with controlled particle structure, size, and functionality. Encapsulation of the luminescent dye (Rhodamine 6G) in SiO2 core of functionalized NPs provided a noticeable increase in their resistance to photo-bleaching and improved biocompatibility. These luminescent NPs were not only attached to murine leukemia L1210 cells but also tolerated by the mammalian cells. Their potential use for labeling of the mammalian cells is considered.

Hyperbranched poly(ethyleneimine) physically attached to silica nanoparticles to facilitate curing of epoxy nanocomposite coatings

There was a hope that highly reactive nanoparticles would strongly facilitate crosslinking in epoxy-amine systems. In this work, silica (SiO2) nanoparticles are physically modified with poly(ethyleneimine) as surface modifier. The SiO2 nanoparticles were synthesized and physically decorated with poly(ethyleneimine), then the untreated and surface-treated SiO2 nanoparticles were analyzed by FTIR, TGA and SEM techniques. The results show that poly(ethyleneimine) hyperbranched molecule is successfully attached to the surface of SiO2 nanoparticles enabling epoxy ring opening. Both untreated and modified particles are impregnated into an epoxy/amine system to fabricate nanocomposite coatings. The effect of the aforementioned SiO2 nanoparticles on the curing behavior of the epoxy/amine system was investigated by means of dynamic DSC analysis. The results demonstrated that, while addition of untreated silica nanoparticles could not seriously curing reactions, the introduction of poly(ethyleneimine)-modified SiO2 facilitated crosslinking of epoxy/amine system thanks to the abundance of amine reactive groups on the particle surface that gives worth to the poly(ethyleneimine)-modified SiO2 nanoparticles as a promising nanomaterial for manufacturing highly-curable epoxy-based nanocomposite coatings.

In-situ polymerization of silica/polydicyclopentadiene nanocomposites: Improved tribological properties and evaluation of interfacial compatibility

ABSTRACTPolymer materials concluding polydicyclopentadiene (poly-DCPD) are widely used in engineering fields but have low load-carrying capacities which limit its widely application. SiO2/poly-DCPD nanocomposites were prepared by in situ polymerization in this work. polystyrene (PS), chemically modified onto the surface of SiO2 nanoparticles to obtain oil-soluble polystyrene coated silica spheres with core-shell structure (PS@SiO2), was used to improve the interfacial compatibility between SiO2 nanoparticles and poly-DCPD matrix. Field-emission scanning electron microscope (FESEM) was used to observe and evaluate the interfacial structure of SiO2/poly-DCPD nanocomposites. The tribological behaviors of SiO2 /poly-DCPD nanocomposites with different PS@SiO2 loading have been investigated detailly in this work. The results showed that the addition of PS@SiO2 nanospheres could greatly decrease friction coefficient and wear rate of the SiO2/poly-DCPD nanocomposites, especially when the loading of PS@SiO2 nanospheres arrived to 4 wt%. The well interfacial compatibility between the PS shell layer of PS@SiO2 spheres and poly-DCPD matrix should be resposible for the improved tribological properties of SiO2 /poly-DCPD nanocomposites.

Silica /polydicyclopentadiene nanocomposites: Preparation, characterization, and mechanical properties

ABSTRACTSilica/poly-dicyclopentadiene (SiO2/poly-DCPD) nanocomposites with improved mechanical properties were successfully prepared by in-situ ring-opening metathesis polymerization (ROMP) using reaction injecting molding (RIM) technique in this work. To improve the interfacial compatibility between SiO2 nanoparticles and poly-DCPD matrix, polystyrene (PS) was chemically modified onto the surface of SiO2 nanoparticles to obtain oil-soluble polystyrene coated silica spheres with core-shell structure (PS@SiO2). The mechanical behaviors of SiO2 /poly-DCPD nanocomposites with different PS@SiO2 content have been investigated in detail. The improved mechanical properties of SiO2 /poly-DCPD nanocomposites were mainly attributed to the well interfacial compatibility between the PS shell layer of PS@SiO2 spheres and poly-DCPD matrix, which resulted from the swelling of DCPD monomer in PS shell before polymerization.

Bio-inspired self-assembly of waxberry-like core-shell SiO2@TiO2 nanoparticles towards antiglare coatings.

Waxberry-like core–shell SiO2@TiO2 nanoparticles were prepared by liquid-phase deposition (LPD) method. The dip-coating self-assembly of waxberry-like core–shell SiO2@TiO2 nanoparticles has been used to fabricate coatings with excellent antiglare properties in the large angle and wide wavelength range. The field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) measurements showed that the surface of SiO2 nanoparticles were coated by titania as a shell with controllable and uniform thickness. The ultraviolet visible near-infrared spectrophotometer (UV-Vis-NIR) results indicate that the maximum transmittance of the antiglare coating is up to 95.80% in the visible band, whereas that of the pure glass substrate is only 92.10%. The scattering and haze of the films have been measured to show that such specifically structured coatings exhibited good antiglare properties in the large angle and wide wavelength range.

Highly-Controllable Imprinted Polymer Nanoshell on the Surface of Silica Nanoparticles for Selective Adsorption of 17<i>β</i>-Estradiol

A highly-controllable core-shell silica-MIPs absorbent by anchoring a MIPs layer to the surface of SiO2 nanoparticles via a surface molecular imprinting process was prepared. The templates were covalently modified with functional monomers to form precursor EstSi. The latter together with coupling reagent KH-570, were grafted onto the surface of SiO2 nanoparticles before polymerization, to ensure the quantity and quality of imprinted sites on the surface of the covalently attached matrix. The as-synthesized core-shell nanomaterials (SiO2@MIP2) were then evaluated for selective adsorption of 17β-estradiol (E2) with Raman spectra as detection method. The results indicate that SiO2@MIP2 can fast and selectively adsorb E2 from structural analogues, with detection limit of 0.01 μmol/l.

Surface modified SiO2 nanoparticles by thiamine and ultrasonication synthesis of PCL/SiO2-VB1 NCs: Morphology, thermal, mechanical and bioactivity investigations

The influence of silica (SiO2) nanoparticles (NPs) on the properties of polycaprolactone (PCL) was investigated. Due to the intense tendency of SiO2 NPs to aggregation and their high surface energy, the surface of SiO2 NPs was treatment via Vitamin B1 (VB1) as a biosafe coupling agent. Novel PCL/SiO2-VB1 nanocomposites (NC) films by variety of percentage of SiO2-VB1 NPs were prepared under ultrasonic irradiation as an eco-friendly and fast procedure following by casting method. Fourier transform infrared spectroscopy and energy dispersive X-ray analysis exposed the presence of SiO2 NPs into the polymer matrix. A good distribution of the silica into the polymer matrix was detected by microscopic observations and EDX testing. According to the UV–Vis spectra, the absorption of prepared NCs was improved via increasing the amount of SiO2 NPs. PCL/SiO2-VB1 NCs showed more thermal stability compared to the pure polymer. The tensile test was investigated and good arrangement among the experimental data and the predicted flexibility of NCs was obtained. Moreover, PCL/SiO2-VB1 6wt% had noticeable increase values for tensile strength. Finally, in vitro bioactivity investigation designated that by rising SiO2 contents in the NCs, the amount of the hydroxyapatite formed was increased and NC films are bioactive and have a potential to be utilized in bone tissue engineering.

TiO2–SiO2 composite nanoparticles containing hindered amine light stabilizers encapsulated by MMA–PMPM copolymers

TiO2–SiO2 composite nanoparticles containing hindered amine light stabilizers (HALSs) were prepared by encapsulation of commercially available TiO2–SiO2 nanoparticles using methyl methacrylate (MMA) and 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate (PMPM) copolymers through mini-emulsion polymerization. The Fourier transform infrared spectral analysis (FTIR) showed that the hindered amine light stabilizer PMPM was incorporated into the TiO2–SiO2/P(MMA-co-PMPM) composite nanoparticles. The X-ray photoelectron spectroscopy analysis (XPS) showed that the surface of TiO2–SiO2 nanoparticles was enriched with HALS moieties. The formation of P(MMA-co-PMPM) random copolymers on the surface of TiO2–SiO2 nanoparticles was determined by differential scanning calorimetry (DSC), and the percentage of the chemically grafted P(MMA-co-PMPM) coverage on the TiO2–SiO2 nanoparticles surface was 40.9 wt% determined by thermogravimetric analysis (TGA), which revealed that the TiO2–SiO2 nanoparticles were successfully encapsulated by MMA–PMPM copolymers. Scanning electron microscopy analysis indicated that the TiO2–SiO2/P(MMA-co-PMPM) composite nanoparticles were mainly homogeneous spherical shape particles, with an average size of about 90 nm. Rhodamine B (Rh.B) photocatalytic degradation study revealed UV-shielding characteristics for TiO2–SiO2/P(MMA-co-PMPM) composite nanoparticles and showed a remarkable decrease in photocatalytic activity of TiO2–SiO2 nanoparticles. These results indicated that TiO2–SiO2/P(MMA-co-PMPM) composite nanoparticles may be promising light stabilizers with covalent functionalization of polymeric HALS, which has little photocatalytic activity, and can be introduced into the weathering-resistant polymer materials to improve their application properties.

Synthesis and characterization of Silica/polyvinyl imidazole/H2PO4-core-shell nanoparticles as recyclable adsorbent for efficient scavenging of Sm(III) and Dy(III) from water

In this study, we used Silica/polyvinyl imidazole core-shell nanoparticles impregnated with sodium dihydrogen phosphate (SiO2/PVI/H2PO4− NPs) for adsorption of samarium and dysprosium ions from aqueous solutions. The effects of the pH, adsorbent dose, contact time, and initial concentration of the adsorbate on the Core-shell nanoparticles adsorption capacity have been studied. The pH value for maximum removal of Sm (III) and Dy (III) on the core-shell nanoparticles surface were found to be 4. The saturated capacity of SiO2/PVI/H2PO4− NPs was up to 160mg.g−1 and 150mg.g−1at 25°C for Sm (III) and Dy (III) ions respectively. The obtained uptake data were analyzed by the Langmuir and Freundlich equations using a linearized correlation coefficient at room temperature. The Freundlich isotherm was found to fit well with the equilibrium data. The adsorption kinetics could be modeled by a pseudo-second-order rate expression. Thermodynamic investigation revealed the adsorption process of the studied ions is entropy driven. Furthermore, the performance of regeneration and reutilization were studied. The adsorbed Sm (III) and Dy (III) can be desorbed by 0.5mol/L HCl, with the desorption percentage of 90% for Sm (III) and Dy (III). After five adsorption–desorption cycles, the adsorption capacity shows a slight decrease (about 15%), implying that the SiO2/PVI/H2PO4− NPs can be used as an effective adsorbent for the removal and recovery of Sm(III) and Dy(III) from aqueous solution. The colloid stability of the SiO2/PVI/H2PO4− NPs was investigated by dynamic light scattering measurements. The SiO2/PVI/H2PO4− NPs are stable in adsorption media after five adsorption – desorption cycles. The high stability of SiO2/PVI/H2PO4− NPs can be attributed to steric stabilization by polyvinyl imidazole adsorbed on SiO2 nanoparticle surfaces.

Ultrasonic-assisted fabrication and characterization of PVC-SiO2 nanocomposites having bovine serum albumin as a bio coupling agent

In this work, SiO2 nanoparticles (NPs) were modified with bovine serum albumin (BSA) under ultrasound irradiations as a green and fast route to achieve their good dispersion. Subsequently, different weight percentages of the modified NPs (3, 6, and 9wt%) were incorporated in poly(vinyl chloride) (PVC) as the matrix. Thermogravimetric analysis of the SiO2-BSA NPs indicated that 12wt% of the modifier was loaded on the surface of SiO2 NPs. Encapsulation of the SiO2-BSA resulted in a meaningful improvement in the optical, mechanical and thermal characteristics of the prepared PVC nanocomposites (NCs). X-ray diffraction (XRD) patterns for the PVC/SiO2-BSA NCs showed a crystalline behavior for the NC with 6wt% of the SiO2-BSA originated from the phosphate buffer on the NPs. Water contact angle of the PVC/SiO2-BSA NCs showed that the hydrophilicity enhanced with increasing of the NPs contents.

Tetra-nickel substituted polyoxotungsate as an efficient sorbent for the isolation of His6-tagged proteins from cell lysate

By virtue of the flexible structure of polyoxometalates, Ni2+ is encapsulated into trivacant lacunary tungstophosphate ligands by the form of [Ni4] cluster to offer a tetra-nickel substituted polyoxotungsate K6Na4[Ni4(H2O)2(PW9O34)2] (Ni4P2). The Ni4P2 is then immobilized onto the surface of SiO2 nanoparticles by self-assembly under electrostatic interactions to give the product of Ni4P2@SiO2 composites. Due to the specific affinity between substituted Ni2+ in the polyoxotungsate and the histidine residues of protein, Ni4P2@SiO2 composites exhibit highly adsorption selectivity towards histidine protein. This Ni4P2@SiO2 composite is of high stability, and SDS-PAGE assay indicates that it can be used repeatedly as an efficient sorbent for the isolation of His6-tagged proteins from cell lysate with improved performance when compared with commercial NTA-Ni2+ column.