SiO2 Core Shell Nanoparticles Research Articles

Controllable synthesis of core-shell SiO2@CeO2 abrasives for chemical mechanical polishing on SiO2 film

The controllable and facile synthesis of SiO2@CeO2 core-shell (CS) composite nanoparticles is crucial for various applications, i.e., chemical mechanical polishing (CMP), nanoreactors, and photocatalysis. However, it is still a challenge to control the synthesis of homogeneous CeO2-coated SiO2 core-shell nanoparticles without additional chemicals or organic solvents. The study investigated the influence of reaction atmosphere, initial pH of the silica colloidal, and the quantity of cerium nitrate on the ceria coating process systematically. Furthermore, the synthesis mechanism of CS composite nanoparticles was ascertained by monitoring changes in pH, zeta potential, secondary size, and morphology over time. The controllable growth of 3%− 67.5% ceria on the surface of silica is realized by controlling the method and timing of adding cerium nitrate and ammonia solution. X-ray photoelectron spectroscopy revealed the Ce-O-Si chemical bonding that combined with the CeO2 at the interfaces of SiO2 core at temperature of 80 °C without post-heating. The material removal rate (MRR) of SiO2 film increased from 32.27 to 294.02 Å/min equipped with CS-7.65% composite nanoparticles as abrasives demonstrated significant improvement. These findings provide valuable insights for the development of SiO2@CeO2 composite nanoparticles in subsequent research.

Light absorption enhancement in organic solar cell using non-concentric Ag:SiO2 core-shell nanoparticles

Low solar energy conversion efficiency prevents the widespread of organic solar cells; hence, metal nanoparticles have been used to overcome this problem without increasing cell thickness. We investigated light absorption enhancement in view of the embedment of Ag:SiO2 core-shell nanoparticles of different shell thicknesses, core offsets, offset orientation angles, and vertical mismatches between neighboring particles. The simulations were carried out using the finite element method. This is the first investigation in the use of asymmetric nanoparticles. At optimized conditions, absorption enhancement up to 345% compared to the one without the nanoparticles could be achieved. The enhancement was found much higher than that of the published values. The enhancement results were mainly from the increase of near-field localization and scattering in the active layer of solar cells due to the excitation of Fano resonances. The resonance occurred due to the non-symmetric nature of the core-shell nanoparticles.

Exploring the Si-precursor composition for inline coating and agglomeration of TiO2 via modular spray-flame and plasma reactor

Inline particle coating after the particle formation process to preserve its specific properties is hardly investigated scientifically. Tackling that issue, we have studied the use of three different vaporized organo-siloxanes (tetraethyl orthosilicate TEOS, hexamethyldisiloxane HMDSO, and octamethylcyclotetrasiloxane OMCTS) as precursors for direct inline coating of pristine titanium dioxide (TiO2) nanoparticles made via spray-flame synthesis. The inline silica (SiO2) coating of the formed titanium dioxide nanoparticles is achieved by vaporizing and sending the chosen organo-siloxane precursors into a cylindrical coating nozzle downstream the particle formation zone of the spray-flame. To further explore the effects on morphology and the quality of the resultant TiO2|SiO2 core-shell nanoparticles, a plasma discharge – i.e., dielectric barrier discharge source – is applied after the coating step. The TiO2|SiO2 core-shell nanoparticles are characterized using Transmission Electron Microscopy (TEM) and Scanning Transmission Electron Microscopy (STEM), X-Ray Diffraction (XRD), Fourier-Transform InfraRed spectroscopy (FTIR), Brunauer-Emmett-Teller surface area analysis (BET), elemental analysis, and dynamic light scattering (DLS).Results showed distinct core-shell nanoparticles with shell thicknesses of around 1.5 nm alongside the formation of unattached SiO2 nanoparticles due to homogenous nucleation of SiO2. As the precursor silicon content increased (TEOS < HMDSO < OMCTS), the homogenous nucleation rose to generate materials with high BET surface areas. When employing OMCTS, the high homogeneous nucleation rate led to SiO2 agglomeration, which resulted in large TiO2|SiO2 agglomerates. Morphologically, the phase composition of anatase/rutile of the produced coated nanoparticles did not vary significantly when compared with the reference uncoated TiO2 nanoparticles, indicating that the SiO2 coating is purely a surface phenomenon. Plasma discharge was shown to reduce coated particle agglomeration up to certain extend. Based on these findings, we conclude that the best studied parameters to benefit the synthesis of homogeneously coated TiO2|SiO2 nanoparticles are (i) using TEOS as a coating precursor to minimize SiO2 homogeneous nucleation and (ii) applying a plasma discharge to slightly reduce coated particle agglomeration.

Size-dependent critical transition in the origin of light emission from core–shell Si–SiO2 nanoparticles

Here, it is established that the origin of the photoluminescence of Si–SiO2 core–shell nanoparticles is strongly size-dependent, with large nanoparticles emitting mostly from the core, whereas small nanoparticles emit predominantly from the shell.

Amine-Functionalized Fe2O3–SiO2 Core–Shell Nanoparticles With Tunable Sizes

Iron oxide magnetic nanoparticles (MNPs) coated with uniform silica shell were synthesized through thermal decomposition and inverse microemulsion methods. The iron oxide MNPs were further coated with silica shells through hydrolysis reaction. For the resulting core–shell MNPs, size regulation of both the magnetic core and the porous shell were achieved, enabling the modulation of their magnetic properties and magnetic interactions. Core–shell MNPs were finally functionalized with amine groups, and immobilized on gold surface due to charge-neutral amine/gold interactions. It was observed that the immobilization process was enhanced under external magnetic field.

Effect of the magnetic core size of amino-functionalized Fe3O4-mesoporous SiO2 core-shell nanoparticles on the removal of heavy metal ions

Magnetite (Fe3O4)-mesoporous silica (mSiO2) core-shell nanoparticles are attractive heavy metal ion adsorbents. However, most studies have focused on the use of superparamagnetic Fe3O4 nanoparticles as core materials, resulting in low magnetic field responses due to their low susceptibility and saturation magnetization (Ms) values. Here, we report the synthesis, microstructure, and properties of ferrimagnetic Fe3O4-mSiO2 core-shell nanoparticles, focusing on the effects of the magnetic core size on their removal efficiency. We analyzed the magnetic properties and structural changes of the surface according to the magnetic core size and elucidated the correlation with the removal efficiency of heavy metal ions. Fe3O4 cores with diameters of 103, 123, or 207nm were synthesized by a modified polyol method, while the silica layer with a porous structure was coated using a sol-gel reaction. Amino-functionalized ferromagnetic Fe3O4-mSiO2 nanoparticles with different core sizes exhibited a faster and more efficient removal behavior of heavy metal ions than other reported superparamagnetic nanoparticles. The highest removal capacity of 84.4 mgg−1 for Cu2+ ions was observed with the nanoparticles having the largest specific surface area of 483.78m2g−1.

Tunable Amorphous Photonic Materials with Pigmentary Colloidal Nanostructures

Amorphous photonic structures using pigmentary α-Fe2O3/SiO2 core–shell nanoparticles are succesfully fabricated. The resulting non-iridicent brilliant colors can be manipulated by shell thickness, particle concentration, and external electrical stimuli using electrophoretic deposition process. Fully reversible and instantaneous color changes as well as noticeable difference between transmitted and reflected colors is observed.

Functionalized TiO2 nanoparticles by single-step hydrothermal synthesis: the role of the silane coupling agents.

A simple, robust and versatile hydrothermal synthesis route to in situ functionalized TiO2 nanoparticles was developed using titanium(IV) isopropoxide as Ti-precursor and selected silane coupling agents (3-aminopropyltriethoxysilane (APTES), 3-(2-aminoethylamino)propyldimethoxymethylsilane (AEAPS), and n-decyltriethoxysilane (DTES)). Spherical nanoparticles (ca. 9 nm) with narrow size distribution were obtained by using DTES or by synthesis performed without silane coupling agents. Rod-like nanoparticles along with 9 nm spherical nanoparticles were formed using aminosilane coupling agents because of a combination of oriented attachment of nanoparticles and specific adsorption of the aminosilane on crystallographic faces of anatase nanoparticles. The nanoparticles were functionalized in situ and became hydrophobic as silanes reacted to form covalent bonds on the surface of TiO2. The versatility of the aqueous synthesis route was demonstrated, and by selecting the type of silane coupling agent the surface properties of the TiO2 nanoparticles could be tailored. This synthesis route has been further developed into a two-step synthesis to TiO2–SiO2 core–shell nanoparticles. Combustion of the silane coupling agents up to 700 °C leads to the formation of a nanometric amorphous SiO2 layer, preventing growth and phase transition of the in situ functionalized nanoparticles.

Cyclodextrin‐Triazole Derivative Functionalized on Ag–SiO2 Core–Shell Nanoparticles via Click Chemistry

Click chemistry has provided a versatile strategy for functionalization in solution chemistry under mild reaction conditions with a high degree of functional group compatibility. Initially, silver (Ag) nanoparticles were prepared by the chemical reduction method, followed by the synthesis of silver–silica (Ag–SiO2) core–shell nanoparticles by the Stöber method. The Ag–SiO2 core shell nanoparticles were functionalized with the alkyne derivative. The cycloaddition reaction between the azide‐functionalized cyclodextrin and the alkyne‐functionalized Ag–SiO2 core–shell nanoparticles was carried out via the copper‐catalyzed click reaction, leading to the formation of the cyclodextrin‐triazole derivative on the Ag–SiO2 core–shell nanoparticles. The presence of the resulting cyclodextrin‐triazole derivative on the silver–silica core–shell nanoparticles was confirmed by Fourier transform infrared spectroscopy (FT‐IR), ultraviolet–visible spectroscopy (UV–vis), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA).

Solid phase extraction of Cd(II) and Pb(II) ions based on a novel functionalized Fe3O4@ SiO2 core-shell nanoparticles with the aid of multivariate optimization methodology.

This work describes novel Fe3O4@SiO2 core-shell nanoparticles functionalized with phenyl isothiocyanate and its application in the preconcentration of Cd(II) and Pb(II) ions. The parameters affecting the preconcentration procedure were optimized by a Box-Behnken design through response surface methodology. Three variables (extraction time, magnetic sorbent amount, and pH value) were selected as the main factors affecting the sorption step, while four variables (type, volume and concentration of the eluent; and elution time) were selected as effective factors of elution step in the optimization study. Following the sorption and elution, the ions were quantified by FAAS. The limits of detection were 0.05 and 0.9ngmL(-1) for Cd(II) and Pb(II) ions, respectively. The relative standard deviations were less than 6.4%. The sorption capacity (in mg g(-1)) of this new sorbent is 179 for Cd(II) and 156 for Pb(II). Finally, this nanocomposite was successfully applied to the rapid extraction of trace quantities of heavy metal ions from fish, sediment, soil, and water samples and satisfactory results were obtained.

Synthesis and characterization of fluconazole-functionalized magnetic nanoparticles as a catalyst for the synthesis of 3-aryl and 3-amino-imidazo[1,2-a]pyridines

Fluconazole immobilised on modified Fe3O4–SiO2 core–shell nanoparticles was synthesised, characterised and used as a catalyst in synthesis of 3-aryl and 3-amino-imidazo[1,2-a]pyridines.

Toxicity evaluation of Gd2O3@SiO2 nanoparticles prepared by laser ablation in liquid as MRI contrast agents in vivo.

Poor toxicity characterization is one obstacle to the clinical deployment of Gd2O3@ SiO2 core-shell nanoparticles (Gd-NPs) for use as magnetic resonance (MR) imaging contrast agents. To date, there is no systematic toxicity data available for Gd-NPs prepared by laser ablation in liquid. In this article, we systematically studied the Gd-NPs’ cytotoxicity, apoptosis in vitro, immunotoxicity, blood circulation half-life, biodistribution and excretion in vivo, as well as pharmacodynamics. The results show the toxicity, and in vivo MR data show that these NPs are a good contrast agent for preclinical applications. No significant differences were found in cell viability, apoptosis, and immunotoxicity between our Gd-NPs and Gd in a DTPA (diethylenetriaminepentaacetic acid) chelator. Biodistribution data reveal a greater accumulation of the Gd-NPs in the liver, spleen, lung, and tumor than in the kidney, heart, and brain. Approximately 50% of the Gd is excreted via the hepatobiliary system within 4 weeks. Furthermore, dynamic contrast-enhanced T1-weighted MR images of xenografted murine tumors were obtained after intravenous administration of the Gd-NPs. Collectively, the single step preparation of Gd-NPs by laser ablation in liquid produces particles with satisfactory cytotoxicity, minimal immunotoxicity, and efficient MR contrast. This may lead to their utility as molecular imaging contrast agents in MR imaging for cancer diagnosis.

Enhanced efficiency of polymer solar cells by incorporated Ag–SiO2core–shell nanoparticles in the active layer

In this article, we creatively incorporated Ag–SiO2 core–shell nanoparticles (Ag–SiO2-NPs) into photo-/electro-active layers consisting of poly(3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) in polymer solar cells (PSCs). By this way, the photovoltaic performances of PSCs have largely been enhanced. The results demonstrate a 13.50% enhancement of short-circuit photocurrent density (Jsc) and a 15.11% enhancement of power conversion efficiency (PCE) as the weight percent of doped Ag–SiO2-NPs is 1.5 wt% in the active layer of corresponding PSCs. We attribute the enhancement to the localized surface plasmon resonance (LSPR) effect of Ag–SiO2-NPs, by which the incident light harvesting is enlarged. Whereas, the incorporated bare Ag nanoparticles (Ag-NPs) in the active layer of PSCs decreases the PCE, which is ascribed to the quenching of excitons at the surface of Ag-NPs and the poor dispersion of Ag-NPs in the active layer. Importantly, this work provides a new approach to enhance the performance of PSCs via the LSPR effect of Ag–SiO2-NPs other than via non-circular nanometals.

Improved performance of nanocrystal memory for aminosilane-mediated Au–SiO2embedded core–shell nanoparticles

We present a memory property study of floating gate structure embedded with Au–SiO2 core–shell nanoparticles (NPs). Herein, the Au–SiO2 core–shell configuration was readily fabricated by a self-assembly (SAM) layer-by-layer process using 3-aminopropyltrimethoxysilane (APTMS) as a versatile mediator. This functional APTMS served as both a binder for adsorbing colloidal Au NPs onto the substrate and to self-organize a SiO2 ultra-thin shell to cover the Au NP cores. A two-run APTMS SAM process was employed to develop the core–shell configuration. The first-run APTMS formed a well-organized monolayer on the substrate which was responsible for the obtained uniform SAM with high density of Au NPs. Next, the second-run APTMS formed an APTMS bilayer around the Au NPs. During the SAM process, a polymerization process simultaneously occurred with the reaction of neighboring silanol groups to form an Si–O–Si network structure. The polymerization was completed by a 400 °C-annealing to form a SiO2 layer within the APTMS bilayer. In addition, the annealing also resulted in the decomposition of the APTMS and released the preformed SiO2 layer from the APTMS bilayer. The ultra-thin SiO2 layer was flexible enough to cover the Au NP cores, eventually constructing the Au–SiO2 core–shell structure. Compared to Au nanocrystal (NC) memory, Au–SiO2 core–shell NCs show a larger memory window and significantly improved retention performance, which are attributed to the SiO2 shell-induced superior NP/oxide interface qualities and the characteristics of the Au NPs.

The investigation of photo-induced chemiluminescence on Co2+-doped TiO2 nanoparticles and its analytical application

A novel space- and time-resolved photo-induced chemiluminescence (PICL) analytical method was developed based on the photocatalysis of the Co2+-doped TiO2 nanoparticles. The PICL reaction procedure under the photocatalysis of Co2+-doped TiO2 nanoparticles was investigated using cyclic voltammetry and potentiometry. Meanwhile, the effect of the electrical double layer outside the Co2+-doped TiO2 nanoparticles on the PICL was investigated by contrasting with the Co2+-doped TiO2-SiO2 core-shell nanoparticles. Significantly, the CL intensity increased apparently and the time of the CL was prolonged in the presence of procaterol hydrochloride because the mechanism of the enhanced PICL reaction may be modified. The route of the PICL was changed due to the participation of the procaterol hydrochloride enriched at the surface of the Co2+-doped TiO2-SiO2 in the PICL reaction, which prolonged the time of the CL reaction and resulted in the long-term PICL. The analytical characteristics of the proposed in-situ PICL method were investigated using the procaterol hydrochloride as the model analyte. The investigation results showed that this new PICL analytical method offered higher sensitivity to the analysis of the procaterol hydrochloride and the PICL intensity was linear with the concentration of the procaterol hydrochloride in the range from ca. 2.0 x 10(-10) to 1.0 x 10(-8) g mL(-1).

Room temperature single electron transistor with two-dimensional array of Au–SiO2 core–shell nanoparticles

The composite nanoparticles of gold core coated with SiO2 shell have been fabricated into 2-dimensional array on a silicon surface by a simple self-assembly method combined with the technique of AFM (atomic force microscopy) nanolithography. The double-barrier-tunneling junction with AFM tip was also fabricated for the room-temperature single-electron tunneling study, by which the AFM tip was orientated on the surface of the SiO2 coated gold composite nanoparticles. The 2D array shows well-pronounced Coulomb staircases with a period of 200 mV at room temperature, demonstrating single electron transistor behavior.