SiO2 Shell Research Articles

Surface physicochemical characteristics for sodium ion removal with sodium silicate modified magnetite core-shell nanoparticles and activation of their plasmid DNA purification ability

In this study, it is investigated the elimination of residual sodium ions from sodium silicate (Na2SiO3) modified Fe3O4@SiO2 nanoparticles, via the additional acidic treatment. Residual sodium ions are generated from the Na2SiO3 precursor during the titration for the fabrication of the Fe3O4@SiO2 core-shell structure; however, they were entirely removed after the in situ additional titration at pH 3 using a 1 M of hydrochloric acid (HCl). The thickness of the SiO2 shell layer of each nanoparticle was measured to 10 nm and the morphology of SiO2 shell on the Fe3O4 core were not significantly different after acid treatment to remove the residual sodium ions. However, the absolute zeta potential of the Na2SiO3-modified Fe3O4@SiO2 was decreased about 20% after HCl treatment (−52.5 ± 3.0 mV). In addition, the mean particle size of the Na2SiO3-modified Fe3O4@SiO2 was increased (363.98 nm) and the polydispersity index, which indicates dispersibility was increased (0.23) since residual sodium ions were eliminated by the acid treatment. It is assumed that the reducing anions in the diffuse layer of the particle due to the elimination of the residual sodium, as the counter ion, decreased the surface charge, thereby reducing the repulsive force between the Fe3O4@SiO2 nanoparticles. Then Fe3O4@SiO2 nanoparticles were utilized for separating plasmid DNA and separated plasmid DNA was measured with agarose gel electrophoresis and the absorbance monitoring. The efficiency of the DNA purification of the Na2SiO3-modified Fe3O4@SiO2 measured to 43.3 ± 5.2 ng/μl which was 58% increased after acid treatment. As a result, the dispersion/magnetic properties and DNA purification efficiency of the Na2SiO3-modified Fe3O4 became equivalent to the characteristics of the TEOS-modified Fe3O4@SiO2 using the additional acid treatment for sodium ions removal.

Microstructure evolution and growth mechanism of core-shell silicon-based nanowires by thermal evaporation of SiO

Core-shell structured SiC@SiO2 nanowires and Si@SiO2 nanowires were prepared on the surface of carbon/carbon (C/C) composites by a thermal evaporation method using SiO powders as the silicon source and Ni(NO3)2 as the catalyst. The average diameters of SiC@SiO2 nanowires and Si@SiO2 nanowires are about 145 nm, and the core-shell diameter ratios are about 0.41 and 0.53, respectively. The SiO2 shells of such two nanowires resulted from the reaction between SiO and CO and the reaction of SiO itself, respectively, based on the model analysis. The growth of these two nanowires conformed to the vapor—liquid—solid (VLS) mode. In this mode, CO played an important role in the growth of nanowires. There existed a critical partial pressure of CO (pC) determining the microstructure evolution of nanowires into whether SiC@SiO2 or Si@SiO2. The value of pC was calculated to be 4.01×10−15 Pa from the thermodynamic computation. Once the CO partial pressure in the system was greater than the pC, SiO tended to react with CO, causing the formation of SiC@SiO2 nanowires. However, the decomposition of SiO played a predominant role and the products mainly consisted of Si@SiO2 nanowires. This work may be helpful for the regulation of the growth process and the understanding of the growth mechanism of silicon-based nanowires.

One-Step Synthesis of Multi-Core-Void@Shell Structured Silicon Anode for High-Performance Lithium-Ion Batteries.

The core-void@shell architecture shows great advantages in enhancing cycling stability and high-rate performance of Si-based anodes. However, it is usually synthesized by template methods which are complex and environmentally unfriendly and would lead to low-efficiency charge and mass exchange because of the single-point van der Waals contact between the Si core and the shell. Here, a facile and benign one-step method to synthesize multi-Si-void@SiO2 structure, where abundant void spaces exist between multiple Si cores that are multi-point attached to a SiO2 shell through strong chemical bonding, is reported. The corresponding electrode exhibits highly stable cycling stability and excellent electrochemical performance. After 200 cycles at a current density of 0.1 A g-1 and then another 200 cycles at 1.2 A g-1 , the electrode outputs a specific capacity of 1440 mAh g-1 . Even at 2.0 A g-1 , it outputs a specific capacity as high as 1182 mAh g-1 . Such an anode can match almost all the cathode materials presently used in lithium-ion batteries. These results demonstrate the multi-Si-void@SiO2 as a promising anode to be used in future commercial lithium-ion batteries of high energy density and high power density.

Electrochemiluminescence biosensor for determination of lead(II) ions using signal amplification by Au@SiO2 and tripropylamine-endonuclease assisted cycling process.

MXene@Au as the base and Au@SiO2 as signal amplification factor were used for constructing an ultrasensitive "on-off" electrochemiluminescence (ECL) biosensor for the detection of Pb2+ in water. The use of MXene@Au composite provided a good interface environment for the loading of tris(2,2-bipyridyl)ruthenium(II) (Ru(bpy)32+) on the electrode. Based on resonance energy transfer, the Au (core) SiO2 (shell) (Au@SiO2) nanoparticles stimulate electron transport and promote tripropylamine (TPrA) oxidation. The luminescence effect of Au@SiO2 was five times that of AuNPs and SiO2 nanomaterials alone, and the ECL intensity was greatly improved. In addition, Pb2+ activated the aptamer to exert its endonuclease activity, which realized the signal cycle amplification in the process of Pb2+ detection. When Pb2+ was added, the ECL signal weakened, and the Pb2+ concentration was detected according to the decreased ECL intensity. Under optimized experimental conditions, this aptamer sensor for Pb2+ has a wide detection range (0.1 to 1 × 106ng L-1) and a low detection limit (0.059ng L-1). The relative standard deviation (RSD) of the sensor is 0.39-0.99%, and the recovery of spiked standard is between 90.00 and 125.70%. The sensor shows good selectivity and high sensitivity in actual water sample analysis. This signal amplification strategy possibly provides a new method for the detection of other heavy metal ions and small molecules.

Preparation and characterization of ZnO/SiO2@n-octadecane nanocapsule for ultraviolet absorbing and photothermal conversion energy storage

In this work, PCM nanocapsules composed of ZnO/SiO2 shell and n-octadecane core were successfully synthesized by emulsion polymerization and hydrothermal method. The crystallinity of ZnO was enhanced on the SiO2 shell by MPTS modification. The granule-like ZnO were distributed on the SiO2 shell. The encapsulation rate of n-octadecane in nanocapsules was about 45.2 % with enthalpy of 95.0 J/g melting at room temperature 28.3 °C. Furthermore, due to the presence of ZnO, the synthesized PCM nanocapsules had excellent UV absorption properties for whole wavelengths, and the absorbed UV light can be converted into heat energy for storage, and the photothermal conversion efficiency had reached 25.0 %. Hence, the prepared ZnO/SiO2@n-octadecane nanocapsules had broad application prospects due to its thermal energy storage, UV protection and photothermal conversion performance.

Experimental investigations on the thermal performance and phase change hysteresis of composite phase change material Na2HPO4·12H2O/SiO2

Integrating hydrated salt phase change material (PCM) into building envelopes is a promising method for achieving building energy saving. However, the hydrated salt suffers from the issues of supercooling, phase separation, leakage and phase change hysteresis. In this work, a novel form-stable composite phase change material (CPCM) with mesoporous silica (SiO2) encapsulating Na2HPO4·12H2O(DHPD) was synthesized by porous matrix composite technology. Thereinto, Na4P2O7·10H2O(TPD) used as the nucleating agent suppressed the supercooling phenomenon, 3 % sucrose can solve the issue of the water molecules loss of DHPD and phase separation.18 % SiO2 was favored for preventing leakage. The modified CPCM exhibited good chemical compatibility, higher charge-discharge efficiency, and good thermal stability via DSC, SEM, XRD, FT-IR and TG tests. According to experimental results, the surface area and pore volume of CPCM decreased, and the weight loss rate was lower than that of pure DHPD. The FT-IR and XRD tests indicated that only physical interaction occurred between the DHPD core and the SiO2 shell. Moreover, it displayed excellent thermal reliability after 500 melting-freezing cycles. Furthermore, the phase change onset temperature, supercooling, and hysteresis degree of CPCM at different melting states during partial melting phase transition were studied. It was found that the hysteresis degree of CPCM decreases with the increase in melting ratio, which may be related to the volume-free energy of PCM.

Core-shell FeNi@SiO2 composite with enhanced microwave absorption performance

In this work, a core-shell FeNi@SiO2 composite is constructed by modified Stöber method. Through adjusting the content of Tetra-Ethyl OrthoSilicate (TEOS) to control the thickness of the SiO2 shell, four FeNi@SiO2 powder samples with different SiO2 mass fractions were prepared, where magnetic FeNi@SiO2 microsphere with the core of FeNi is completely coated by SiO2. Herein, the electromagnetic parameters of the composites are effectively tuned by the combination of magnetic FeNi with dielectric SiO2. Results show that when the mass fraction of SiO2 is 35 %, the prepared FeNi@SiO2 powder sample exhibits good absorption performance, the minimum reflection loss (RL) reaches − 36.25 dB at 2.6 mm with the effective absorption bandwidth (RL<−10 dB) of 6 GHz (9.5–15.5 GHz) at 2.0 mm. It is believed that its good absorbing performance originates from the synergistic effect of the conductivity loss, dielectric polarization loss and magnetic loss of core-shell FeNi@SiO2 composite. This work provides a versatile strategy for FeNi@SiO2 composite with unique core-shell structures on excellent and tunable microwave absorption performance.

Y2W3O12@SiO2 composite particles for regulating thermal expansion and interfacial reactions in BaZr0.1Ce0.7Y0.1Yb0.1O3-δ/AISI 441 joints

Y2W3O12 particles with negative thermal expansion (NTE) can offset the high thermal expansion of Ag-based sealants, thus relieving the residual stress of electrolyte/interconnect joints in protonic ceramic fuel cell (PCFC) stacks. Nevertheless, violent interfacial reactions between Y2W3O12 particles and BaZr0.1Ce0.7Y0.1Yb0.1O3-δ electrolyte have severely restricted the application of these NTE particles. Herein, novel Y2W3O12@SiO2 composite particles with a core-shell structure are successfully designed to address this conundrum. The thermal expansion coefficient of Ag-based sealant is lowered from 19.7 to 14.6 ppm/K by adding 20 wt% Y2W3O12@SiO2 particles. During joining, the SiO2 shell significantly reduces the reaction consumption of Y2W3O12, fully exploiting its NTE properties. Meanwhile, a tiny portion of SiO2 participates in and regulates interfacial reactions, generating mechanically matched reaction layers. Finite element simulation demonstrates that introducing Y2W3O12@SiO2 particles significantly releases the compressive X-stress near the BaZr0.1Ce0.7Y0.1Yb0.1O3-δ interface, thus increasing the joint strength from ∼25.3 to ∼32.4 MPa. Obtained joints maintain long-term stability in oxidizing and reducing atmospheres at 600 °C, suggesting the applicability of Y2W3O12@SiO2 composite particles in fabricating PCFC stacks. Our work provides a new strategy for preparing NTE materials with controllable interfacial reactions and service capability under extreme conditions.

Influence of acid and alkali reaction system on the morphology and thermal properties of paraffin@SiO2 phase change microcapsules for heat storage

Phase change materials are preferred in the field of thermal energy storage in low-medium temperature. Paraffin@SiO2 microcapsules were prepared by a sol–gel method at an acid and alkali reaction system. The field emission scanning electron microscope, Fourier transform infrared spectroscope, differential scanning calorimetry, and thermogravimetric analyzer were adopted to investigate the effect of the acid and alkali reaction system on the morphology, latent heat, and thermal stability of PA@SiO2 microcapsules. In the acid reaction system, the particle size and latent heat of PA@SiO2 microcapsules are in the range from 15 to 30 μm and from 132 to 174 J/g, respectively. However, comparing with the acid reaction system, there was a remarkable reduction in the particle size and latent heat of microcapsules prepared in the alkali reaction system. The initial weightlessness temperatures of PA@SiO2 microcapsules were 40 °C higher than that of paraffin, indicating that the SiO2 shell was beneficial to the microcapsule structure.

SPION nanoparticles for delivery of dopaminergic isoquinoline and benzazepine derivatives

Superparamagnetic iron nanoparticles (SPIONs) have become one of the most useful colloidal systems in nanomedicine. We report here the preparation of new hybrid core@shell systems based on SPION nanoparticles coated with a SiO2 shell (SPION@SiO2) and functionalized with carboxyl groups (SPION@SiO2-COOH). A series of new N-alkylamino- and N-alkylamido-terminated 1-phenyl- tetrahydroisoquinolines (THIQs) and 3-tetrahydrobenzazepines (THBs) derivatives presenting -SMe and -Cl groups, respectively, with potential dopaminergic activity, are synthesized and incorporated to the hybrid system. We include the synthetic details for THIQs and THBs derivatives preparation and investigate the influence of the terminal-functional group as well as the number of carbon atoms linked to THIQ and THB molecules during the coupling to the SPION@SiO2-COOH. Nuclear magnetic resonance (NMR) and electron ionization mass spectrometry (EI-MS) are used to characterize the synthesized THIQs and THBs. High-angle annular dark-field transmission electron microscopy (HAADF-TEM), energy dispersive X-ray transmission electron microscopy (EDX-TEM), and proton high-resolution magic angle spinning NMR spectroscopy1H HRMAS-NMR) are used to confirm the presence of THB and THIQ molecules onto the surface of the nanoparticles. The hybrid SPION@SiO2-THIQ and THB systems show significant activity toward the D2 receptor, reaching Ki values of about 20 nM, thus having potential application in the treatment of central nervous system (CNS) diseases.

Doxorubicin-Loaded Core-Shell UiO-66@SiO2 Metal-Organic Frameworks for Targeted Cellular Uptake and Cancer Treatment.

Beneficial features of biocompatible high-capacity UiO-66 nanoparticles, mesoporous SiO2, and folate-conjugated pluronic F127 were combined to prepare the core–shell UiO-66@SiO2/F127-FA drug delivery carrier for targeted cellular uptake in cancer treatment. UiO-66 and UiO-66-NH2 nanoparticles with a narrow size and shape distribution were used to form a series of core–shell MOF@SiO2 structures. The duration of silanization was varied to change the thickness of the SiO2 shell, revealing a nonlinear dependence that was attributed to silicon penetration into the porous MOF structure. Doxorubicin encapsulation showed a similar final loading of 5.6 wt % for both uncoated and silica-coated particles, demonstrating the potential of the nanocomposite’s application in small molecule delivery. Silica coating improved the colloidal stability of the composites in a number of model physiological media, enabled grafting of target molecules to the surface, and prevented an uncontrolled release of their cargo, with the drawback of decreased overall porosity. Further modification of the particles with the conjugate of pluronic and folic acid was performed to improve the biocompatibility, prolong the blood circulation time, and target the encapsulated drug to the folate-expressing cancer cells. The final DOX-loaded UiO-66@SiO2/F127-FA nanoparticles were subjected to properties characterization and in vitro evaluation, including studies of internalization into cells and antitumor activity. Two cell lines were used: MCF-7 breast cancer cells, which have overexpressed folate receptors on the cell membranes, and RAW 264.7 macrophages without folate overexpression. These findings will provide a potential delivery system for DOX and increase the practical value of MOFs.

Polystyrene‐Silica Colloidal Janus Particles with Uniform Shapes and Complex Structures

AbstractColloidal Janus particles with well‐controlled parameters are sought for a range of applications in mesoscale self‐assembly, stabilization of Pickering emulsion, and development of multifunctional devices, among others. Herein, a versatile method for fabricating polystyrene‐silica (PS‐SiO2) Janus particles featuring complex shapes and structures is developed by swelling PS@SiO2 core–shell spheroids. When the PS encapsulated in a rigid SiO2 shell is swollen by a good solvent for PS, the swelling‐induced pressure will result in an uneven distribution of stress acting on the SiO2 shell, as determined by the intrinsic symmetry of a spheroid. When the stress reaches a threshold value, the swollen PS will preferentially poke out from equatorial sites on the SiO2 shell to form T‐shaped Janus particles comprised of PS and SiO2 compartments. The size of the PS portion can be controlled by varying the extent of swelling, while the size, shape, and shell thickness of the SiO2 portion are determined by the original PS spheroids and the SiO2 coating. This solution‐phase method holds promise to produce Janus particles with diverse shapes, structures, and compositions for various applications. The T‐shaped Janus particles can serve as an emulsifier to effectively stabilize an oil‐in‐water (O/W) Pickering emulsion for at least 35 days.

Role of SiO2 Coating on YAG:V3+,Nd3+ Nanoparticles in Luminescence Thermometry

Coating luminescent nanoparticles with a SiO2 shell provides numerous benefits, which include improving the dispersibility of nanoparticles, reducing their cytotoxicity, and facilitating their biofunctionalization. However, from the perspective of luminescent thermometry, it is important that such a procedure does not alter the thermometric properties of the luminescent nanothermometer. Therefore, in this work, the effect of the SiO2 encapsulation procedure on the thermometric properties of YAG:V3+,Nd3+ nanoparticles was investigated. It was demonstrated that increasing the thickness of the SiO2 layer increases the thermal stability of the luminescence of V3+ ions. However, it was demonstrated that a high relative sensitivity of 1.5%/K at 500 K can be maintained for a luminescence thermometer while keeping a thin SiO2 shell.

Thermally Stable Red‐Emitting Mixed Halide Perovskite Nanocrystals Enabled by Solid Reaction and Co‐Doping Process

AbstractRapid performance degradation as temperature increases for metal halide perovskite nanocrystals (NCs) greatly restricts the practical application for lighting and display. This problem is even more grievous for the mixed‐halide perovskite NCs because of severe ions migration. Here, a solid‐reaction process in the N2 atmosphere is devised, in which the red‐emitting (631 nm wavelength) mixed halide CsPbBr1.5I1.5 NCs with a coating of SiO2 shell are achieved. Meanwhile, the Zn2+ and K+ ions are co‐doped into the crystal lattice to enhance the radiative decay rate and decrease the trap density of the NCs. The photoluminescence quantum yield of the co‐doped NCs reaches 64.5%, which is one of the highest values for the reported mixed‐halide perovskite NCs obtained by the solid reaction. Importantly, the dopant of K+ enters into the interstitial position of the perovskite structure to increase the structural rigidity, which inhibits exciton–phonon interaction and elevates thermal activation energy, thus improving thermal quenching resistance to sustain high emission intensity at high temperature (&gt;353 K). Furthermore, the red backlight emitting diode based on the NCs exhibits no decay in luminescence intensity after continuous operation for 700 h at 353 K, representing remarkable stability for the commercial application.

Coulombic interaction: The origin of hollow silica nanoparticles from charged polystyrene template

The research on the preparation and application of monodispersed hollow silica nanoparticles (HSNs) has never been stopped during the past few decades, but its formation mechanism has always been a topic worthy of debate. Herein, the typical template strategy was adopted to reveal the driving force of forming HSNs including three vital stages: preparation of well-defined sacrificial polystyrene (PS) nanosphere templates, deposition of silicon dioxide on PS template to form PS/SiO2 core/shell composites by a modified Stöber method, calcination of PS templates to generate HSNs. Therein, the deposition step determined if hollow structure can be obtained. PS templates with different sizes and surface properties were used to evaluate the deposition process, which was carefully monitored and characterized by microscopies (SEM, Cryo-FIB/SEM, and TEM), dynamic light scattering (DLS), and Zeta Potential. We found that only positively charged PS templates can induce the deposition of hydrolyzed silicon source, in the form of negatively charged solid SiO2 nanoparticles with the diameter of ~20 nm under the catalysis of alkali, by the Coulombic interactions. Then the deposited SiO2 shell could grow up due to the rapid condensation of silanol groups on both SiO2 shells and free solid SiO2 nanoparticles under alkaline condition. This article for the first time proved the formation process and mechanism of HSNs in detail, demonstrating great potential for regulating and preparing various functional hollow nanoparticles by diverse supramolecular interactions.

Facile functionalization of YVO4:Eu3+: From nanoparticles to luminescent PMMA nanocomposites for radiation detectors

YVO4:Eu3+ is a luminescent material that has been widely used in cathode ray tubes and plasma display panels. Nowadays, different applications are being explored. Fiber-optic Dosimetry (FOD) is an alternative to traditional dosimetry systems for radiotherapy treatments. Although some published results have demonstrated the potential of using YVO4:Eu3+ as nanometer powder for FOD systems, none of them tend to improve its tissue equivalence, a significant limitation. One possible solution could be to disperse the NPs in a tissue-equivalent polymer matrix, like Poly Methyl Methacrylate (PMMA). Consequently, YVO4:Eu3+/PMMA nanocomposites were developed using NPs synthesized according to a combustion method previously reported. This work focuses on studying two different NPs functionalization strategies. One of them involves the synthesis of a SiO2 shell and a posterior treatment with Oleic Acid (OA). The other involves the use of a silane (3-(Trimethoxysilyl)propyl methacrylate, TMSPM) as a coupling agent. Both strategies allow the surface modification of NPs. The study of luminescence properties of NPs showed no significant changes between both functionalized NPs related to Eu3+ spectrum characteristic peaks. However, YVO4:Eu3+@TMSPM has better performance (the reduction in YVO4:Eu3+@TMSPM is about 15%, while in YVO4:Eu3+@SiO2@OA is 62%). On the other hand, functionalized nanoparticles were used to develop polymeric nanocomposites (PNCs) by in situ polymerization of Methyl Methacrylate using a cyclic triperoxide as initiator. Functionalized NPs were characterized by Fourier Transform Infrared Spectroscopy, Transmission Electron Microscopy, Dynamic Light Scattering, Thermogravimetric Analysis, and luminescence measurements. Films were obtained by dissolution of the PNCs, and their luminescent properties were also studied. Results indicate that although the strategy that involves the silica shell plus OA is better in terms of cover density, the TMSPM promotes a better dispersion on the polymer matrix.

Modulation of electromagnetic absorption and shielding properties of geopolymer nanocomposites by designing core–shell structure of carbon nanotubes

In this work, an electromagnetic (EM) protective building material was developed by combining silica (SiO2)-grafted carbon nanotubes (S@CNTs) with geopolymer (GeoP). The EM absorption and shielding properties of the GeoP nanocomposites were modulated by tailoring the SiO2 shell thickness. With the increase in shell thickness, the attenuation coefficient decreased, while the impedance matching degree, which acted as a prerequisite for evaluating EM absorption performance, improved. As a result, the minimum reflection loss (RLmin) reached −38.4 dB at 11.1 GHz and the effective absorption bandwidth of 3.4 GHz with a thickness of 2.9 mm was obtained. Practically, the electron transport capability was promoted with a thinner SiO2 shell, leading to an improvement in electrical conductivity. As the conductivity increased, the EM interference shielding effectiveness (SE) increased to 11.0 dB, while the RLmin also increased to −8.7 dB. Based on the underlying mechanism analysis, the strategy for modulating EM performance can be extended to other building materials.

Biodegradable wood plastic composites with phase change microcapsules of honeycomb-BN-layer for photothermal energy conversion and storage

A novel thermal energy storage (TES) composites system consisting of the microPCMs based on n-octadecane nucleus and SiO2/honeycomb-structure BN layer-by-layer shell as energy storage materials, and wood powder/Poly (butyleneadipate-co-terephthalate) (PBAT) as the matrix, was created with the goal of improving the heat transmission and photothermal responsiveness of building materials. The microPCMs were made via mini-emulsion interfacial polycondensation and electrostatic self-assembly to anchor BN on the surface of the SiO2 shell. The two kinds of microPCMs we designed had regular spherical morphology, BN was successfully anchored outside the SiO2 shell, showing a honeycomb structure and good heat storage performance (140.4 J/g and 140.6 J/g). The thermal energy storage wood plastic composites (TES WPCs) had considerable energy storage capacity and temperature regulation ability. The TES WPCs with the unique honeycomb structure of BN-MicroPCMs (BN-WPC) had better heat transfer performance and photothermal conversion efficiency (69.54%), and the thermal conductivity, specific heat capacity and energy storage efficiency of which were increased by 75.06%, 87.06% and 200% respectively. Meanwhile, the unique honeycomb structure strengthened the interfacial bond strength of TES WPCs and brought satisfactory mechanical strength, and the tensile strength, elongation at break, bending strength and bending modulus of BN-WPC are increased by 51.16%, 97.01%, 81.28% and 742.74%, respectively compared with the WPC added with S-MicroPCMs (S-WPC). These results indicated that this research by designing the BN honeycomb structure layer on the traditional microPCMs surface, obtained the rapid thermal response of high-performance TES WPCs in residential construction, thermal energy storage, solar energy collection system and thermal regulation has broad application prospects.

Strecker synthesis of α-aminonitriles using Au nanoparticles‏¬‏ capped with porous SiO2 shell (Au@pSiO2) as a highly efficient and recyclable nanostructured catalyst

Nano Au@porous SiO2 as a heterogeneous catalyst characterized by UV-Vis, XRD, TEM, and ICP-AES analysis. Amount of Au in Au@pSiO2 showed the 3.85% wt of Au in Au@porous SiO2 and the peak at 523 nm in UV-Vis spectrum dedicated to Au NPs. The prepared catalyst used in the condensations of various aldehydes and amines with smooth nucleophilic addition with trimethylsilyl cyanide through the one-pot three-component Strecker reaction for the preparation of α-aminonitrile derivatives in good to excellent yields at room temperature under solvent free reaction conditions. Short reaction periods, rapid access to products, ease of catalyst separation and simple workup, high chemical and thermal stability and reducing the leaching of the nanocatalyst into the environment are the important advantages of this nanocatalyst.

Synchronous enhancements in dielectric performances and thermal conductivity of β-SiCw/PVDF nanocomposites through building crystalline SiO2 shell as an interlayer

Synchronous enhancements in dielectric performances and thermal conductivity of β-SiCw/PVDF nanocomposites through building crystalline SiO2 shell as an interlayer