Nanosilica Surface Research Articles

An eco-friendly and energy-efficient protocol for the Heck reaction under solar radiation catalyzed by rice husk silica‐anchored cinchonine.Pd nanocomposite

An environmentally friendly and energy-efficient method for the carbon–carbon bond formation via cross-coupling Heck reaction using rice husk silica-anchored cinchonine.Pd nanocomposite as a heterogeneous catalyst under concentrated solar radiation is being reported. In this investigation, first, silica nanoparticles were synthesized using rice husks as available agricultural bioresources. Then, the surface of nano silica was modified by grafting (3-mercaptopropyl) trimethoxysilane, and after that, thiol-ene free radical reaction of its SH groups with alkene function of cinchonine by azobisisobutylonitrile initiator. Finally, the target nanocomposite, nano SiO2-S-Cin.Pd, was created via loading palladium nanoparticles into the mesoporous nanocomposite by its reaction by palladium acetate, followed by ethanol reduction. The structure and morphology of the nano SiO2-S-Cin.Pd nanocomposite was characterized using Fourier transform infrared spectra, X-ray diffraction patterns, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. The catalytic ability of this nanocomposite was investigated in the arylation of olefins in both concentrated solar radiation and conventional thermal conditions. A comparison of the conventional and CSR methods for C–C bond formation in PEG, showed that the CSR approach is a better alternative route with a high energy-saving strategy. The nanocatalyst is easily removed from the mixture and has been tested on several runs without a loss of catalytic activity. The heterogeneity of the nano SiO2-S-Cin.Pd catalyst was confirmed by hot filtration test. This method has the advantages of simple methodology, easy work-up, high yields, short reaction times, and greener conditions. In addition to convenience, this technology improves product purity and offers economic and environmental benefits.

Adenine‐Functionalized Dendritic Fibrous Nanosilica as Bifunctional Catalyst for CO2 Fixation into Cyclic Carbonate

AbstractCycloaddition of CO2 with epoxide to form cyclic carbonate is one of the most promising approaches to mitigate the rising level of CO2 in the atmosphere. Therefore, the design and synthesis of new materials which can efficiently catalyze such reactions has become an important research area. This article reports on the synthesis of a new material, adenine functionalized dendritic fibrous nanosilica (DAD), by functionalizing the surface of dendritic fibrous nanosilica (DFNS) with an N‐containing heterocyclic nucleobase adenine using a bifunctional isocyanate crosslinker ((EtO)3Si(CH2)3NCO). The surface amine functionalities enable DAD to show selective CO2 adsorption (0.44 mmol/g, at 1 bar CO2 pressure and 298 K temperature) due to acid‐base interaction between CO2 and amine groups. Moreover, DAD efficiently catalyzes the fixation of CO2 with a variety of epoxides into corresponding cyclic carbonates in the presence of TBAB (tetrabutylammonium bromide) co‐catalyst under solvent‐free conditions. The DFNS skeleton of DAD offers a high surface area for enhanced CO2 adsorption, while its organic surface groups, adenine and carbamide, boost the selectivity and activate the epoxide ring and CO2 for cycloaddition reaction. The strong covalent linkage of surface groups in DAD renders robust structural integrity, enabling the catalyst to be recycled multiple times with negligible reduction in its catalytic performance.

Sulfonic Acid Functionalized Precipitated Silica as Efficient Solid Acid Catalyst for Acetylation Reactions

Introduction: Precipitated Silica has very high commercial significance in terms of ease of preparation, market volume, cost benefits and a wide range of industrial applications. The surface silanol groups of Precipitated Silica can be modified with reactive organic functional groups to achieve desired properties for specific applications, including catalysis. Objective:: The objective of this study is to demonstrate sulfonic acid functionalized Precipitated Silica as a true heterogeneous catalyst in acetylation reaction, where the catalytic activity and desired product selectivity is a magnitude higher than industrial solid acid zeolite catalysts as well as similar catalysts reported in literature. Methods: A novel and cost-effective method for the functionalization of Precipitated Silica with sulfonic acid (–SO3H) is reported, where the silica nanoparticles are first functionalized in situ with a tetrasulfide organosilane, followed by oxidation of the tetrasulfide moiety to –SO3H groups, which are grafted to the surface silanol groups through covalent linkage. Results: CHNS analyses and XPS prove successful functionalization of –SO3H group onto the nano silica surface. The resultant material acts as a solid acid catalyst and shows exceptional activity in the acetylation of benzyl alcohol and >99% selectivity towards the desired product benzyl acetate. The resultant material can also be recycled and reused several times. Conclusion: The following factors make sulfonic acid functionalized Precipitated Silica a new generation of solid acid catalyst; (i) higher atom economy, (ii) recyclability and reusability, and (iii) significant cost benefits with respect to industrial catalysts.

Preparation of dense modified nanosilica superhydrophilic coatings on aluminum alloy surfaces by adjusting amino groups

In this work, a uniform superhydrophilic coating was prepared by grafting N-(2-aminoethyl)-3-aminopropyltriethoxysilane oligomers(AEAOS) onto nanosilica by using silane coupling agent modification and coated on the surface of aluminum alloys to reduce water droplet generation. The grafting and dispersibility of modified nanosilica and aminosilane oligomers were characterised using Fourier transform infrared (FTIR) and dynamic light scattering (DLS). The surface state, composition, and roughness of the coatings were characterised with scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and optical profilometer. The hydroxyl and organic content of modified nanosilica was analyzed by Thermogravimetric Analysis (TGA). The compactness of the coating film is analyzed by an electrochemical impedance. The hydrophilicity and adhesion of the coating films were evaluated by contact angle and adhesion testing. By adjusting the concentration of amino groups in the nanosilica sol, the results show that the amino groups promote the silane grafting on the surface of nanosilica. The 10% addition of AEAOS gives the modified silica film a contact angle of <5° with superhydrophilic properties. The polarization resistance of the superhydrophilic coating film is about 10 times higher than that of the original aluminum alloy. The surface of the coated films is homogeneous and dense, showing high resistance to polarization and good corrosion resistance.

Role of polyaniline coating on nanosilica particles in polyvinylidene fluoride nanocomposites for energy storage

Polymer nanocomposites, which are characterized by a high dielectric permittivity, are intensively studied for microelectronic devices and energy storage applications. Poly(vinylidene fluoride) (PVDF) has a higher dielectric permittivity among polymers, is flexible, lightweight and easy to be processed. One route to enhance its mechanical and dielectric properties is the addition of inorganic nanofillers. Therefore, PVDF was melt compounded with nanosilica in various proportions, from 5 to 30 wt%. For enhancing the stored and released electric energy densities, polyaniline (PANI) was obtained in situ on the surface of nanosilica in both acid and basic media; further the nanosilica particles coated with PANI were incorporated in PVDF by melt compounding to improve the dielectric properties by adding new interfaces. The addition of nanosilica in PVDF led to a strong increase in its storage modulus without reducing its good thermal stability. Moreover, an important increase in PVDF permittivity was determined by increasing content of nanosilica in nanocomposites. PANI coating influenced both thermal and mechanical properties and led to nanocomposites with more stable dielectric permittivity and lower dielectric loss than neat PVDF at frequencies between tens Hz and tens kHz, which is very important for energy storage applications.

Construction of Photoinitiator Functionalized Spherical Nanoparticles Enabling Favorable Photoinitiating Activity and Migration Resistance for 3D Printing.

A straight-forward method was exploited to construct a multifunctional hybrid photoinitiator by supporting 2-hydroxy-2-methylpropiophenone (HMPP) onto a nano-silica surface through a chemical reaction between silica and HMPP by using (3-isocyanatopropyl)-triethoxysilane (IPTS) as a bridge, and this was noted as silica-s-HMPP. The novel hybrid-photoinitiator can not only initiate the photopolymerization but also prominently improve the dispersion of nanoparticles in the polyurethane acrylate matrix and enhance the filler-elastomer interfacial interaction, which results in excellent mechanical properties of UV-cured nanocomposites. Furthermore, the amount of extractable residual photoinitiators in the UV-cured system of silica-s-HPMM shows a significant decrease compared with the original HPMM system. Since endowing the silica nanoparticle with photo-initiated performance and fairly lower mobility, it may lead to a reduction in environmental contamination compared to traditional photoinitators. In addition, the hybrid-photoinitiator gives rise to an accurate resolution object with a complex construction and favorable surface morphology, indicating that multifunctional nanosilica particles can be applied in stereolithographic 3D printing.

Silver Nanoparticles Functionalized Nanosilica Grown over Graphene Oxide for Enhancing Antibacterial Effect.

The continuous growth of multidrug-resistant bacteria due to the overuse of antibiotics and antibacterial agents poses a threat to human health. Silver nanoparticles, silica-based materials, and graphene-based materials have become potential antibacterial candidates. In this study, we developed an effective method of enhancing the antibacterial property of graphene oxide (GO) by growing nanosilica (NS) of approximately 50 nm on the graphene oxide (GO) surface. The structures and compositions of the materials were characterized through powdered X-ray diffraction (P-XRD), transmission electron microscopy (TEM), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), ultraviolet–visible spectroscopy (UV–VIS), dynamic light scattering (DLS), Raman spectroscopy (RM), Fourier-transform infrared spectroscopy (FTIR), Brunauer–Emmet–Teller (BET) surface area, and pore size determination. The silver nanoparticles (AgNPs) with an average diameter of 26 nm were functionalized on the nanosilica (NS) surface. The composite contained approximately 3% of silver nanoparticles. The silver nanoparticles on nanosilica supported over graphene oxide (GO/NS/AgNPs) exhibited a 7-log reduction of Escherichia coli and a 5.2-log reduction of Bacillus subtilis within one hour of exposure. Both GO/NS and GO/NS/AgNPs exhibited substantial antimicrobial effects against E. coli and B. subtilis

Study on modification of nano silica by [3- (2-Aminoethyl) aminopropyl] trimethoxy silane (KH-792) to reinforce polymer film based on epoxy resin Epon 1001X75

The surface of nano silica (NS) was modified by [3- (2-Aminoethyl) aminopropyl] trimethoxy silane (KH-792) to increase surface activity. Evaluate the efficiency of grafting [3- (2-Aminoethyl) aminopropyl] trimethoxy silane (KH-792) into NS was characterized by Fourier Transform Infrared Spectrometry (FTIR) and Thermo Gravimetric Analysis (TGA). NS and modified nano silica (m-NS) were dispersed into epoxy resin Epon 1001X75 by mechanical stirring and ultrasonic vibration. Epoxy resin Epon 1001X75 was cured with Epikure 3125 (Epi3125). The structural morphology and dynamic mechanical properties of materials were characterized by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Dynamic Mechanical Analysis (DMA). The results showed that NS was modified with the content of 20 wt% KH-792 for the highest denaturation efficiency. With adding the content of 1 wt% NS (NS-1), the mechanical properties of epoxy polymer film Epon 1001X75/Epi3125/NS-1 increased the impact strength from 20kG.cm to 52.5 kG.cm (increased by 162.5%). Adding the content of 2 wt% m-NS (m-NS-2) improved the impact strength of epoxy polymer film Epon 1001X75/Epi3125/m-NS-2 from 20 kG.cm to 55 kG.cm (increased by 175%). The glass transition temperature (Tg) of epoxy polymer composites Epon 1001X75/Epi3125, Epon 1001X75/Epi3125/NS-1, and Epon 1001X75/Epi3125/m-NS-2 gradually increased by 48 °C, 75 °C, and 79 °C. The obtained results showed that m-NS with KH-792 increased the mechanical properties of epoxy polymer film Epon 1001X75/Epi3125.

Covalently bonded sulfonic acid onto the surface of magnetic nanosilica obtained from rice husk: CoFe2O4@RH-Pr-SO3H as novel acid catalyst for synthesis of octahydroquinazolinone and 3,4-dihydropyrimidinone

In this research project, an environmentally friendly solid catalyst was synthesized from low-cost rice husk (RH–SiO2). Then, RH–SiO2 was applied to support cobalt ferrite (CoFe2O4) on the surface or inside the pores of amorphous SiO2. The nanoparticles were later modified by sulfonated (CoFe2O4@RH-Pr-SO3H) through modification with 3-mercaptopropyltrimethoxysilane (MPTMS) and subsequent oxidation with hydrogen peroxide (H2O2). The characterization techniques including FT-IR, BET, CHNS, FE-SEM, TEM, VSM, TGA-DTG, EDX and X-ray mapping confirm the structure of this supported complex. Furthermore, the effect of the preparation method of the catalyst CoFe2O4@RH-Pr-SO3H was extensively studied against the synthesis of 3,4-dihydropyrimidinones and octahydroquinazolinones. There are no harmful organic solvents used in the current approach. The nontoxic nature, short reaction times, easy recovery and efficient reusability of the CoFe2O4@RH-Pr-SO3H are advantages of this approach. The nanocatalyst could be recovered easily and reused several times without the loss of its activity.

Influence of nanosilica coating on the color and the microleakage of zirconia ceramics

Objective The purpose of this study was to assess the effect of Nano-silica Coating on the Color and the Microleakage of Zirconia Ceramics. Materials and methods: Eighty-five specimens of commercially available Yttrium-stabilized-zirconia ceramics were constructed and divided into forty-five discs (8 mm in diameter) with thickness (1.2mm) They were divided into three groups (thermocycling – nano-silica surface treatment – and thermocycling with nano-silica surface treatment) to assess the color parameters, while the other forty samples were divided into ( control group – thermocycling – nano-silica surface treatment – and thermocycling with nano-silica surface treatment) to perform a fully contoured crowns to assess the microleakage. Initial color measurements were taken using a digital spectrophotometer based on CIE L*a*b* color system using a spectrophotometer Standard permanent molar tooth preparation was conducted into a full veneer preparation. Nano silica sol-gel material painted on the fitting surface of zirconia ceramics in groups of nano-silica and nano-silica with thermocycling surface treatment and processed to firing that were finally cemented on the prepared teeth using resin adhesive luting agent. Samples in aged group were subjected to 5000 thermal cycles then crown samples were sectioned to measure the microleakage. Color measurements of all samples were measured again.

Effect of tri(methoxysilyl)propyl methacrylate silane modified nanosilica on some properties of acrylic coating

Acrylic emulsion resin is one of popular matrixes for both outside and inside coatings. It has low cost, high UV and weather resistance, good aesthetics and environmentally friendly. The introduction of inorganic additives in nanosize such as SiO2, TiO2, etc. into acrylic emulsion resin could improve the mechanical and thermal properties of the polymer matrix. The surface modification of nanoparticles can enhance the dispersibility of the nanoparticles in the polymer matrix. This paper presents the characteristics of nanosilica modified with different contents of tri(methoxysilyl)propyl methacrylate silane (MPTS) as a coupling agent and the effect of modified nanosilica on the abrasion resistance and thermal properties of acrylic emulsion resin. The infrared (IR) spectroscopy and thermo-gravimetric analysis (TGA) were used to evaluate the presence of MPTS on the surface of modified nanosilica. Grafting yield of MPTS on the surface of nanosilica was calculated from TGA diagrams. The obtained results showed that nanosilica was surface modified successfully by MPTS with a grafting yield of 47 % when using 3 wt.% of MPTS. After modification, the modified nanosilica became more hydrophobic and can disperse well in acrylic emulsion resin. The modified nanosilica improved significantly the abrasion resistance of acrylic coating as compared to neat acrylic resin and acrylic/unmodified silica nanocoating. The MPTS modified nanosilica has the potential to be applied as a reinforcing additive to acrylic emulsion resins to improve its abrasion resistance.

Removal of beta-lactam antibiotic in water environment by adsorption technique using cationic surfactant functionalized nanosilica rice husk

This study aims to investigate the adsorption characteristics of cationic surfactant, cetyltrimethylamonium bromide (CTAB) onto negatively nanosilica rice husk surface and the application for antibiotic treatment in water environment. Adsorption of CTAB onto nanosilica increased with an increase of solution pH, due to an enhancement of the electrostatic attraction between cationic methylamomethylamonium groups and negatively charged nanosilica surface enhanced at higher pH. Adsorption of CTAB decreased with a decrease of ionic strength while a common intersection point (CIP) was observed for adsorption isotherm at different ionic strengths, suggesting that hydrophobic interactions between alkyl chains in CTAB molecules significantly induced adsorption and admicelles with bilayer formation were dominant than monolayer of hemimicelles. The CTAB functionalized nanosilica (CFNS) was applied for removal of beta-lactam amoxicillin (AMX). The best conditions for AMX treatment using CFNS were selected as pH 10, contact time 60 min and CFNS dosage 10 mg/mL. Removal efficiency of AMX using CFNS reached to 100% under optimum conditions while it was only 25.01% using nanosilica without CTAB. The maximum AMX adsorption capacity using CFNS of about 25 mg/g was much higher than other adsorbents. The effects of different organics such as humic acid, anionic surfactant, and other antibiotics on AMX removal using CFNS were also studied. A two-step model can fit CTAB uptake isotherms onto nanosilica and AMX onto CFNS well at different KCl concentrations. Based on the desorption of CTAB with AMX adsorption as well as adsorption isotherms, the change in surface charge and functional vibration groups after adsorption, we indicate that AMX adsorption onto CFNS was mainly controlled by electrostatic interaction. We reveal that CFNS is an excellent adsorbent for antibiotic treatment from aqueous solution.

Durable self-polishing antifouling coating based on fluorine-containing pyrrolidone amphiphilic copolymer-functionalized nanosilica

Marine biofouling is detrimental to ships and has been a significant issue in the marine industry for several decades. The development of effective, long-term, and environment-friendly antifouling coating is important but remains a challenge in oceanographic engineering. A series of novel amphiphilic block copolymers (PVP-co-PTFEMA), containing hydrophilic segments (N-vinylpyrrolidone, or NVP) and hydrophobic segments (trifluoromethyl methacrylate, or TFEMA), are grafted on the nanosilica surface via surface-initiated atom transfer radical polymerization (SI-ATRP). The as-prepared amphiphilic copolymers-functionalized silica, SiO2-g-(PVP-co-PTFEMA), can be blended well with self-polishing resin, which could obtain a new type of self-polishing nanocomposite coating. The SiO2-g-(PVP-co-PTFEMA) based composite coating exhibits satisfactory antibacterial and antifouling properties due to the synergistic effect of a strong hydration layer of hydrophilic NVP fragments and low adhesion of hydrophobic TFEMA unit. The slow hydrolysis of the as-prepared self-polishing nanocomposite coating results in the formation of micro/nano structures due to the exposure of SiO2-g-(PVP-co-PTFEMA) in seawater. Moreover, the SiO2-g-(PVP-co-PTFEMA) based nanocomposite coating exhibits high mechanical durability. The as-prepared self-polishing nanocomposite coating combines outstanding antifouling performance and high mechanical durability, which could be an ideal choice in marine antifouling applications.

Correction: Determination of aflatoxin M1 using an aptamer-based biosensor immobilized on the surface of dendritic fibrous nano-silica functionalized by amine groups

Correction for ‘Determination of aflatoxin M1 using an aptamer-based biosensor immobilized on the surface of dendritic fibrous nano-silica functionalized by amine groups’ by Houman Kholafazad kordasht et al., Anal. Methods, 2019, 11, 3910–3919, DOI: 10.1039/C9AY01185D.

Synthesis of Mesoporous Silica and Graphene‐Based FeO and ZnO Nanocomposites for Nutritional Biofortification and Sustained the Productivity of Rice (Oryza sativa L.)

Considering nutrient delivery and micronutrient use efficiency problems, mesoporous nanosilica (mNs) and reduced graphene oxide (rGO)‐based iron and zinc nanocomposites were formulated. Prepared nanocomposites were characterized for FTIR spectroscopy, XRD, FE‐SEM, HR‐TEM, and AAS to examine surface functional groups, morphology, and structural composition. XRD spectrum confirmation with SAED image of nanosilica and graphene oxide nanocomposites confirms the polycrystalline and crystalline nature with 30–70‐nm crystal size. The SEM revealed that the modified surface of mesoporous nanosilica and reduced graphene oxide are well‐distributed clusters and are composed of targeted micronutrients. The impact of nano Fe and Zn foliar application was evaluated on rice grain fortification, productivity, and micronutrient use efficiency. The iron and zinc uptake at 60 days after sowing (DAT) and at harvest was significantly increased with foliar application of mNs and rGO‐based Zn at 30 ppm + Fe at 5 ppm nanocomposites as well as led to nutrient fortification by increasing grain uptake and content, with the application of 30 ppm zinc and 5 ppm iron through mNs resulted in an improvement of the rice grain yield by 53% over conventional fertilization. Besides significant increment in grain yield, foliar application of mNs and rGO‐based nanocomposites (Zn at 30 ppm + Fe at 5 ppm) increased the Zn and Fe use efficiency by 527 and 380%, respectively, over conventional micronutrient fertilization (ZnSO4 and FeSO4).

Gas-phase crosslinking of the lignin on the nanoscale fumed silica surface

A method for the polymerization modification of nanoscale fumed silica by crosslinking a lignin layer adsorbed on a nanosilica surface under a gas dispersion medium is described. A mixture of phenol and formaldehyde in the presence of HCl proved to be the most effective crosslinking agent. It has been suggested that the crosslinking of lignin molecules occurs by a mechanism similar to the production of phenol-formaldehyde resins.

Secondary structure of muramyl dipeptide glycoside in pristine state and immobilized on nanosilica surface

Fourier transform infrared spectroscopy (FT-IR) and temperature programmed desorption mass spectrometry (TPD-MS) data of O-glycoside MDP in pristine and immobilized on silica surface states indicate that O-glycoside MDP binds to the silica surface by means of carboxylic and NH moieties of isoglutamine. Moreover, pyrolysis of O-glycoside MDP on the silica surface proceeds through formation of additional product 3-iminopyridine-2(3H)-one, which identified in mass spectra as molecular ion with m/z 108 and its fragment ions with m/z 79, 77, 51. FTIR and TPD-MS data confirm existence of a MDP first β-turn on the silica surface resulting from the formation of a hydrogen bond between the NAc carbonyl and the L-Ala NH for MDP and its analogs, as reported previously.

In Ukrainian

The joint efforts of chemists, physicians and technologists conducting researches to create new medical sorbents and combined drugs based on nanosilica, which have not only a detoxifying effect, but also antibacterial, wound healing, hemostatic and other important properties. One of the stages of such a research is developing regulatory documentation. To control the quality of the sorbent, the method of point measurements is most often used, according to it, the amount of adsorption of the marker substance at the single point of the adsorption curve is determined. The suitability of sorbents based on nanosilicа for using is determined by the value of the adsorption capacity concerning to medical gelatin. No other requirements for the process of test adsorption of gelatin by the sorbent are given. although it is known that the adsorption of proteins depends on the pH of the solution. Its maximum value is reached at a pH value corresponding to the isoelectric point (pI) of the protein. Each protein can be characterized by its own isoelectric point. Domestic and foreign standards give only the value of “pH of aqueous solutions” of gelatin and do not contain the indicator “isoelectric point”. The aim of the work is to study the influence of the isoelectric point of gelatin on its adsorption on nanosilica surface at different pH to appreciate the suitability of conditions for determining the adsorption activity of medical sorbents based on nanosilica. The adsorption of three samples of gelatin was examined in the work: A – edible gelatin (pI = 4.3–4.8); B – that from the catalog “Merck” (pI = 4.3–4.8) and C – that from the catalog “Fluka” (pI = 7.5–7.7) on nanosilica surface in the pH range from 3 to 8. It has been shown that for samples A and B the dependence has a maximum at pH ~ 4.5–5; and for sample C, the adsorption increases monotonically with increasing pH. It was noted that at pH ~ 5 the adsorption values for all gelatin samples were approximately equal. The adsorption activity of nanosilica concerning to proteins determined from the isotherms and the method of point measurements is compared. It has been found that the adsorption value of gelatin A onto the nanosilica at Cinitial = 700 mg/100 ml is equal to the Aave value determined by the Langmuir isotherms. This fact verifies the applicability of the method of point measurements for nanosilica/gelatin system to characterize the pharmacological activity of nanosilica based sorbents.

Highly efficient visible-light-driven photocatalytic degradation of organic pollutants by using magnetically separable supported heterogeneous nanocomposites (SiO2/Fe3O4/Ag2WO4)

In this work, the heterogeneous photocatalyst (SiO2/Fe3O4/Ag2WO4) that is composed of active nanomaterials precipitated onto mesoporous nanosilica was synthesized using multistep methods. The nanosilica was synthesized using the Stöber method. 10% Wt. of Fe3O4 and Ag2WO4 NPs were precipitated on the surface of nanosilica to produce supported SiO2/Fe3O4/Ag2WO4 magnetic nanoparticles (MNPs). Different techniques were used to characterize the synthesized supported MNPs, including UV-DRS, XRD, VSM, BET, BJH, and FE-SEM. The photocatalytic degradation activity of synthesized supported MNPs was conducted through a batch reactor towards methylene blue dye (M.B) under visible light irradiation (40 W LED and 55 W Xenon lamps). The experimental results showed a high degradation efficiency (approximately 100%) related to SiO2/Fe3O4/Ag2WO4 after 45 min of irradiation time. The SiO2/Fe3O4/Ag2WO4 revealed high adsorption activity, where 60% of its removal efficiency was during the first 60 min of adsorption in the dark. The kinetics studies revealed that the photocatalytic activity of SiO2/Fe3O4/Ag2WO4 was nearly 4.2 and 3.9 times higher than pure Ag2WO4 and SiO2/Fe3O4, respectively. The significantly improved photocatalytic activity of the SiO2/Fe3O4/Ag2WO4 MNPs was attributed to their higher stability and specific surface area, in addition to a synergistic outcome between Ag2WO4 and SiO2/Fe3O4 that leads to efficient electron–hole pairs separation. The effects of several parameters were also examined for supported MNPs, including catalyst dose, initial concentration of M.B, pH, and H2O2 addition. The reusability and recyclability study revealed that the synthesized SiO2/Fe3O4/Ag2WO4 are highly stable and can be used with high feasibility for removal of different organic dyes from wastewater.

Anomalous Terminal Shear Viscosity Behavior of Polycarbonate Nanocomposites Containing Grafted Nanosilica Particles.

Viscosity controls an important issue in polymer processing. This paper reports on the terminal viscosity behavior of a polymer melt containing grafted nanosilica particles. The melt viscosity behavior of the nanocomposites was found to depend on the interaction between the polymer matrix and the nanoparticle surface. In the case of polycarbonate (PC) nanocomposites, the viscosity decreases by approximately 25% at concentrations below 0.7 vol% of nanosilica, followed by an increase at higher concentrations. Chemical analysis shows that the decrease in viscosity can be attributed to in situ grafting of PC on the nanosilica surface, leading to a lower entanglement density around the nanoparticle. The thickness of the graft layer was found to be of the order of the tube diameter, with the disentangled zone being approximately equal to the radius of gyration () polymer chain. Furthermore, it is shown that the grafting has an effect on the motion of the PC chains at all timescales. Finally, the viscosity behavior in the PC nanocomposites was found to be independent of the molar mass of PC. The PC data are compared with polystyrene nanocomposites, for which the interaction between the polymer and nanoparticles is absent. The results outlined in this paper can be utilized for applications with low shear processing conditions, e.g., rotomolding, 3D printing, and multilayer co-extrusion.