Synthesis of superhydrophobic core–shell mesoporous silica nanoparticles

Mesoporous silica nanoparticles (MSNPs) have been used in variety of applications due to their morphology and porous structure. This work reports the one-pot synthesis of ultrahydrophobic MSNPs using N-cetyl-n,n,n trimethyl ammonium bromide as a cationic surfactant template and ethanol (EtOH) as a cosolvent to form mesopores in the MSNPs. The effects of EtOH on the size and the pore structure of the MSNPs were studied by scanning electron microscopy and transmission electron microscopy. The results show that an addition of EtOH led to an enlargement of the MSNPs and a change in pore structure from a lamellar structure to a radially oriented structure. Co-condensation with two different types of fluoroalkyl silanes; trimethyl(fluoromethyl)silane, and trichloro(1H,1H,2H,2H-perfluorooctyl)silane provided low surface energy MSNPs with a core–shell structure. An assembly on the surface of these F-MSNPs generated nanostructure surface roughness rendering an improvement in surface wettability with water contact angle of 158.6°, which is a characteristic of oleophobic and ultrahydrophobic material.     

Synthesis of multifunctional core–shell toughening agent with light stability and its application in polycarbonate

A light stabilizer compound of 2-(2′-propionyloxy-5′-methylphenyl) benzotriazole (AMB) was synthesized by the esterification of the 2-(2′-hydroxy-5′-methylphenyl) benzotriazole with acryloyl chloride (AC), and the AMB was then copolymerized with the methyl methacrylate (MMA), butyl acrylate (BA), and silicone monomers (D4) to prepare the silicone light toughener of poly(D4-MMA-BA-AMB). Effects of the AMB monomer on the conversion and polymerization stability and the toughening and photostabilizing effects of the poly(D4-MMA-BA-AMB) on the polycarbonate (PC) were studied. The prepared multifunctional toughening agent was characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, thermogravimetric analyzer, transmission electron microscopy, dynamic light scattering analyzer, and ultraviolet absorption spectroscopy. Results show that the prepared poly(D4-MMA-BA-AMB) toughening agent possessed core–shell structure and could effectively absorb the ultraviolet rays. Although the addition of the poly(D4-MMA-BA-AMB) toughening agent had a negative effect on the tensile strength of the PC, it could greatly improve the low-temperature notched impact strength, toughness performance, and yellowness performance of PC products after UV irradiation. Compared with the silicone toughening agent, the toughening agent of the poly(D4-MMA-BA-AMB) had better anti-ultraviolet property for the PC/poly(D4-MMA-BA-AMB) composite. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48747.     

Thermal,optical and dielectric properties of Zn–Al layered double hydroxide

Zn–Al–NO₃–layered double hydroxide (Zn–Al–NO₃–LDH) was prepared by the co-precipitation method at a constant pH of 7 and a ratio of Zn/Al = 4. A thermal treatment was performed for LDH at various temperatures. Powder XRD patterns showed that the layered structure of the LDH samples was stable below 200 °C, which was also confirmed by thermogravimetric (TGA) and differential thermal (DTA) analyses. Infrared spectra of the samples showed the characteristic peaks of LDH, and changes of these peaks were observed when thermal treatment was performed above 150 °C. Diffuse reflectance spectroscopy of the samples showed more than one energy gap at calcination temperatures below200 °C. In samples calcined at 200 °C and above only one energy gap was observed at approximately 3.3 eV. The photocatalytic activity was found to increase with the increase of the ZnO crystal size, which can be achieved by increasing the calcination temperature of the samples. Because of the presence of water molecules and anionic NO₃⁻ in the interlayer of the LDH, the dielectric response of the calcined LDH can be described by an anomalous low frequency dispersion using the second type of Universal Power Law for calcination temperatures below 200 °C. The dielectric response of the calcined LDH above 150 °C displays the dielectric relaxation behaviour of ZnO because of the formation of a ZnO phase in the LDH within this temperature range.     

Synthesis and characterization of novel bifunctional mesoporous silica catalyst and its scope for one-pot deacetalization–knoevenagel reaction

Bifunctional (both sulfonic and amine functionalized) mesoporous silica catalysts were prepared by hydrothermal method. (3-[2-(2-amino ethyl amino) ethyl amino] propyl trimethoxysilane) and (3-mercaptopropyl) trimethoxysilane respectively were used as amine and sulfonic sources. The synthesised bifunctional materials were fully characterized by BET, P-XRD, ²⁹Si CPMAS-NMR, FTIR, XPS and SEM spectral analysis. FTIR and NMR results endorse the successful grafting of organic amines and sulfonic group by surface silanol of silica. The presence of of N and S groups in the catalyst material was confirmed by the XPS spectra. Catalytic activity of the bifunctional material was tested for one-pot deacetalization–knoevenagel reaction, which gave excellent yield (95 %). Catalyst is reusable with little loss of activity up to 4 runs (<6 %).     

Preparation of dendritic–linear polyether-modified silica sol and its application in coatings

Dendritic–linear polyether-modified silica sol (DLPS) was synthesized using diethylenetriamine, methyl acrylate, epoxy-terminated polyether, triethoxysilane, and silica sol in five steps. The prepared sol was stable and transparent. DLPS was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and particle size distribution analysis. Subsequently, DLPS was examined as a stain-resistant additive in (paint) coatings. The surface of the sample coatings with and without DLPS additive was examined by scanning electron microscopy, energy-dispersive spectrometry analysis, and contact angle analysis. The results showed that the stain-resistant additive appeared on the surface of the coating, which made the surface more compact and hydrophilic. The performance of the stain-resistant additive was examined in commercial outdoor emulsion coatings (WB200). The result showed that the presence of the stain-resistant additive could enhance the stain resistance performance of paint. Furthermore, the stain resistance performance improved with increasing amounts of additive. Specifically, the stain resistance performance of paint improved by 40.63% in the presence of 6 wt% DLPS. Therefore, the current findings demonstrate the importance of DLPS in advancing progress and application in the paint coating industry.     

Synthesis of supramolecular biodendrimeric β-CD-(spacer-β-CD)21 via click reaction and evaluation of its application as anticancer drug delivery agent

The per-β-CD dendrimer (10), having 21 β-CD residues connected to the core β-CD in the primary and secondary sides with encapsulation efficacy and β-CDs moiety to preserve the biocompatibility properties was synthesized using click reaction. The dendritic network and β-CD cavity of the obtained dendrimer were utilized to form a supramolecular compound via the formation of a host-guest inclusion complex with methotrexate (MTX) drug molecule. The MTT assay of compound 10 showed very low toxicity on T47D cancer cells. In vitro drug release investigation at pHs 7.4, 5, and 3 indicated that the release manner was remarkably pH dependent.     

Cobalt doping stabilizes the expanded structure of layered double hydroxide cathodes for application in fast charging Ni–Zn batteries

Journal of Applied Electrochemistry - Improving the reversible capacity, fast chargeability, and cyclability of cathode materials are the primary challenges in the development of advanced...     

Synergistic effect of organically modified layered double hydroxide on thermal and flame-retardant properties of poly(butyl acrylate–vinyl acetate)

Organically modified layered double hydroxide (O-LDH) was successfully synthesized by coprecipitation and characterized through Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). O-LDH/poly(butyl acrylate–vinyl acetate) (P(BA-VAc) emulsion was prepared via in situ polymerization, then ammonium polyphosphate (APP) was introduced to obtain the O-LDH/APP/P(BA-VAc) flame-retardant latex. The flame retardancy and thermal behavior of the latexes after evaporation of water were investigated by the limiting oxygen index (LOI) test, vertical burning test (UL-94), and thermal gravimetric analysis (TGA). Compared with the APP/P(BA-VAc) composite, the LOI value of O-LDH/APP/P(BA-VAc) containing 0.5 wt.% O-LDH at the same total additive loading increased to over 30.0%, and its UL-94 increased from no rating to V-0. TG data show that the amount of residues increases obviously when O-LDH is added. The LOI values increased with increasing amounts of char residues. The morphology and microstructure of residues generated during the LOI test were investigated by scanning electron microscopy (SEM). FTIR and X-ray photoelectron spectroscopy (XPS) were used to determine the composition of the residues formed after combustion at 450 °C for 5 min to support a fundamental analysis of the mechanism of char formation.     

Synthesis of mesoporous α-MnO2 in manganese(II)-based deep eutectic solvent and their application in the absorption of Congo red

Mesoporous alpha-manganese dioxide (α-MnO₂) were synthesized from manganese(II)-based deep eutectic solvent (DES) of MnCl₂?4H₂O and acetamide in a 1:7 molar ratio. The DES can act as solvent and reducing reagent. As-prepared samples were characterized and used as absorbents for the removal of Congo red (CR) from aqueous solutions. Results show that the sample prepared at 70°C (M-70) could remove 93% CR from aqueous solutions in 30 min. The maximum adsorption capacity of the M-70 was estimated to be 54.85 mg/g. Finally, the exhausted M-70 can be regenerated by thermal desorption.     

Synthesis of gelatin–PVA adsorbent and its application in the separation of ginkgo flavonol glycosides and terpene lactones

Spherical adsorbents derived from the glutaraldehyde cross-linked hybrid of gelatin and polyvinyl alcohol (PVA) were synthesized, and their adsorption selectivity for ginkgo flavonol glycosides and terpene lactones was also investigated in detail. An adsorbent with an appropriate gelatin content can selectively adsorb flavonol glycosides with a high adsorption capacity based mainly on hydrogen bond interactions, while showing only a fairly low adsorption capacity for terpene lactones. A much higher adsorption affinity of flavonol glycosides than that of terpene was calculated from the adsorption isotherms. Thus, a simple preparative separation procedure for ginkgo flavonol glycosides and terpene lactones from a ginkgo leaf was established. An enriched extract containing flavonol glycosides of up to 60% and terpene lactones as low as 0.2% and an extract with a terpene lactones content up to 30% was prepared by this method, respectively.     

Poly(N-isopropylacrylamide)-coated β-cyclodextrin–capped magnetic mesoporous silica nanoparticles exhibiting thermal and pH dual response for triggered anticancer drug delivery

In this research a novel controlled anticancer drug delivery system with dual pH and thermal responses was designed based on magnetic mesoporous silica nanoparticles that were anchored by β-cyclodextrin and coated by poly(N-isopropylacrylamide) (PNIPAM). Results demonstrated that the behavior of doxorubicin (anticancer drug) release depended on pH and temperature conditions. At endosomal pH (pH 5.5) the amount of drug release enhanced because the cap was removed from the pores. Furthermore, PNIPAM shell collapsed above the lower critical solution temperature and the releasing of drug increased. Thus, this nanocarrier would have the potential to be applied in the tumor therapy.     

Synthesis and characterisation of nanocrystalline Ca–Al layered double hydroxide {[Ca2Al(OH)6]NO3.nH2O}: in vitro study

Abstract

Abstract

In this study, Ca–Al–NO₃ layered double hydroxide (LDH) nanoparticles of varying sizes were synthesised by a process involving co-precipitation under hydrothermal condition. This method produces stable homogeneous LDH suspensions under variable hydrothermal treatment conditions with particle size in the range of 7·5–2·5 μm. Layered double hydroxides were characterised by X-ray diffraction, Fourier transform infrared spectroscopy, thermal gravimetric/differential thermal analysis, scanning electron microscopy and transmission electron microscopy (TEM) and nanosizer analyses. By increasing the hydrothermal treatment time, the crystallinity and the particle size of obtained LDH increased. Scanning electron microscopy and TEM observations showed uniform hexagonal flake-like particles with high aspect ratio. Finally, Ca–Al–NO₃ LDH did not show any acute cytotoxic effect up to 100 μg mL^?1 as measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.     

Preparation and characterization of L-phenylalanine-derivatized β-cyclodextrin-bonded silica and its application on chiral separation of alanine acid racemates

A chiral adsorption material, L-phenylalanine-derivatized β-cyclodextrin-bonded silica (L-Phe-CD/SiO₂), was prepared and characterized by Fourier transform infrared (FT-IR), elemental analysis, field emission scanning electron microscope (FESEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TG) measurements. Langmuir and Freundlich isotherm models were employed to simulate the equilibrium data. The results showed that the equilibrium data were well represented by Langmuir isotherm model. Experimental data were analyzed using pseudofirst order and pseudo-second order kinetic models and the obtained results indicated that kinetics followed a pseudosecond order equation. The static adsorption experiments indicated that L-Phe-CD/SiO₂ had significantly higher adsorption capacity for L-alanine (L-Ala) compared with D-alanine (D-Ala); and the selectivity coefficient is 2.53. The result shows that the prepared L-Phe-CD/SiO₂ could be applied to chiral separation of the racemic alanine acid solution.     

Synthesis of conductive polyaniline–graphite nanocomposite in supercritical CO2 and its application in zinc-rich epoxy primer

Exfoliated polyaniline–graphite (PAniG) nanocomposite (NC) with high electrical conductivity was synthesized via in situ polymerization of aniline in the presence of intercalated graphite in ScCO₂ medium. Ammonium peroxydisulfate (NH₄)₂S₂O₈ (APS) was used as an oxidizing agent. The morphology and structure of synthesized PAniG NC was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FTIR). Synthesized PAniG NC was used to modify the barrier properties and cathodic protection behavior of a commercial zinc rich epoxy primer (c-ZRP) on low carbon steel (CS) substrate. The protective properties of original and modified ZRPs (m-ZRP) were investigated using open circuit potential (OCP) measurements and electrochemical impedance spectroscopy (EIS) method. It was found that after immersing coated CS for 365 days in 3.5% sodium chloride solution the OCP for m-ZRP remained at the cathodic protection region (lower than −0.86 V/SCE), while for c-ZRP it was passed out of protection region after immersing 100 days. EIS analysis revealed that in m-ZRP the zinc consumption and formation of zinc oxide was delayed and after 100 days of immersion, resistance of c-ZRP and m-ZRP reaches to 2.48 × 10⁴ Ω and 2.56 × 10³ Ω, respectively. Results revealed that the performance of m-ZRP improved due to the barrier properties of PAniG NC which added to the primer.     

Fabrication and sustained release properties of poly(ε-caprolactone) electrospun fibers loaded with layered double hydroxide nanoparticles intercalated with amoxicillin

Amoxicillin (AMOX) was intercalated in layered double hydroxide (LDH) nanoparticles by coprecipitation. LDH intercalated with AMOX (LDH/AMOX) was successfully encapsulated at different concentrations into poly(ε-caprolactone) (PCL) by the electrospinning technique. Mats of non-woven PCL fibers loaded with LDH/AMOX were obtained and characterized in terms of morphology and in vitro release. The fibrous structure of a pristine PCL sample was composed of individual, uniform, and randomly oriented fibers with an average diameter ranging around 0.8 μm. The addition of LDH/AMOX at different concentrations caused a slight increase of the average diameter and the presence of rare beads possibly due to clusters of the nano-hybrid on the surface of the microfibers.The release curves present a sustained release behavior, although an initial rapid drug release was found. The initial high-rate drug release period was followed by a second step in which the release is slow, extending for long time. The comparison of the release curves showed that the release of AMOX protected into the clay is slower than the release of the drug alone.     

Properties of electroless and electroplated Ni–P and its application in microgalvanics

Composition, microstructure, surface morphology, mechanical properties and electrochemical behaviour of electroless (el) and electroplated (ep) Ni–P deposits are studied using XPS, SEM–EDX, AFM, nanoindentation measurements, cyclic voltammetry and capacitance measurements. Ni–P layers were compared with ep Ni films and bulk Ni. Ni–P layers prepared by both techniques contain 12–14 wt% phosphorus, present in oxidation states of P⁰ and P³⁻. El and ep Ni–P deposits are amorphous and are characterised by a relatively low average surface roughness (2 and 4 nm, respectively). The ep layers possess a rhythmic-lamellar microstructure indicating a periodic change of electrodeposition conditions. The el Ni–P layers do not show such laminated structure but exhibit small surface pores, which are absent in the ep layers. Comparable values for the hardness and the reduced elasticity modulus of el and ep coatings are determined from the nanoindentation data. The observed small differences indicate that the mechanical properties of Ni–P deposits depend not only on the phosphorus content but also on the deposit microstructure. Microelectrochemical measurements with the so-called droplet cell show that the electrochemical behaviour of both el and ep Ni–P coatings is practically identical and does not depend on the location on the sample surface. Evolution of O₂ and H₂ on Ni–P are similar to pure Ni (ep and bulk), but the corrosion resistance in acid solution is much better. The very similar properties and electrochemical behaviour of el and ep Ni–P deposits suggest that both materials are suitable for various applications in microsystem technology. For different substrates and microstructures of different size and geometry, deposition conditions have still to be optimised.     

Surface modification of magnesium hydroxide and its application in flame-retardant oil-extended styrene–ethylene–butadiene–styrene/polypropylene composites

Magnesium hydroxide (MH) was modified with triethoxysilane and polymethyl–vinyl silicone rubber and used to prepare flame-retardant oil-extended styrene–ethylene–butadiene–styrene (O-SEBS)–polypropylene (PP) composites. The water contact angle of modified magnesium hydroxide (MMH) reached 141°; this indicated that MMH possessed excellent hydrophobic properties. The samples (1.6 mm) passed the UL-94 V-0 rating during vertical burning tests when the loading amount of MH or MMH was 70 wt %. This indicated the modification did not decrease the flame-retardant properties of MH. The tensile strength and elongation at break values of the MMH–O-SEBS–PP composites increased by 20.4 and 88.9%, respectively, compared with those of the MH–O-SEBS–PP composites. The modification of MH enhanced the interfacial compatibility between the flame retardant and the matrix; thus, the mechanical performance was enhanced. Moreover, MMH was scarcely extracted after water treatment for 168 h at 70 °C. As a result, the mechanical properties and flame retardancy of the MMH–O-SEBS–PP composites were well maintained after the water treatment. The modification of the MH endowed the O-SEBS–PP composites with an excellent compatibility and water-resistant performance. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47129.     

Synthesis of carbon–silica core–shell nanofibers from a dispersion of fluorinated carbon nanofibers in solvated polysiloxane

Carbon–silica core–shell fibers (which unusually consist of carbon nanofibers coated with silica) were synthesized using a two-step process. First, fluorination of carbon nanofibers (CNFs) allows their homogenous dispersion into a polysiloxane matrix. A longlife dispersion of nanofibers in solvated polysiloxane has been prepared. Second, the polysiloxane/fluorinated carbon was thermally treated in air until 700 °C. Defluorination and conversion of polysiloxane into silica occur and result in carbon–silica core–shell fibers. The thermal treatment of the polysiloxane/carbon and the resulting silica/carbon–silica core–shell nanostructures were investigated using solid state nuclear magnetic resonance using ¹⁹F, ¹³C ¹H, and ²⁹Si nuclei, X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopies.