Core-shell Silica Microspheres Research Articles

In situ preparation of water-stable SiO2@mSiO2/CsPbBr3 and its application in WLED

Recently, all-inorganic perovskites as photoluminescent materials have attracted significant attention in the field of light-emitting diodes. However, their instability towards UV light, high temperature, and water has impeded widespread commercial applications. We propose a facile strategy for synthesizing CSSM-CPB by encapsulating perovskite CsPbBr3 (CPB) into the channels of core-shell silica microspheres (CSSM). Subsequently, the channels of CSSM-CPB were sealed with octadecyltrichlorosilane (ODS). Consequently, the stability of CSSM-CPB to UV light, high temperature, and water significantly improved. Notably, CSSM-CPB retains a high fluorescence emission intensity even after immersion in water for 30 days. Furthermore, the photoluminescence quantum yield of CSSM-CPB reaches 68%, compared to just 30% for discrete CPB. A CSSM-CPB-WLED was also developed, exhibiting a color temperature (Tc) of 5869 K, Commission Internationale de l′Éclairage (CIE) color coordinates of (0.34, 0.34), a luminous efficiency of 86.31 lm W−1, and a color gamut overlap with the NTSC space of approximately 121.1%. These results indicate a significant enhancement over CPB-WLED, suggesting that the stability of CPB can be improved through silica encapsulation and hydrophobic material sealing. This approach has potential for commercial application in display devices requiring high stability.

A brief review on recent advances in reverse phase HPLC

Modern chromatography is mostly used for analytical purposes. Modern pharmaceutical and biological analysis uses HPLC. It separates molecules from heterogeneous liquids and characterizes them. Mass spectrometry identifies peptides, proteins, and other compounds after high-performance liquid chromatography. HPLC's flexibility and dependability (pressure-driven liquid support) make it popular. However, fast separation often creates high operating pressure, which stresses HPLC equipment. Thus, core-shell silica microspheres and zirconia packing have been produced recently. Fused-core or superficially porous microspheres have solid cores with porous shells. Despite its low pressure, this device can separate small, large, and intricate molecules. It is effective and fast. UPLC offers greater resolution, sensitivity, and separation times than HPLC; however, it may be less reproducible. Rapid Resolution Liquid Chromatography (RRLC) is more precise and sensitive than HPLC, improving sample analysis quality and quantity. This review will highlight column technology basics and RP-HPLC advances and focuses on the concept of HPLC.

Flexible Radiative Cooling Textiles Based on Composite Nanoporous Fibers for Personal Thermal Management.

Passive radiative cooling textiles can reflect sunlight and dissipate heat directly to the outside space without any energy input. However, radiative cooling textiles with high performance, large scalability, cost effectiveness, and high biodegradability are still uncommon. Herein, we exploit a porous fiber-based radiative cooling textile (PRCT) via nonsolvent-induced phase separation and scalable roll-to-roll electrospinning technology. Nanopores are introduced into single fibers, and the pore size can be accurately optimized by managing the relative humidity of the spinning environment. The anti-ultraviolet radiation and superhydrophobicity of textiles were improved by the introduction of core-shell silica microspheres. An optimized PRCT yields a strong solar reflectivity of 98.8% and atmospheric window emissivity of 97%, which results in a sub-ambient temperature drop of 4.5 °C, with the solar intensity over 960 W·m-2 and 5.5 °C at night. For personal thermal management, it is demonstrated that the PRCT can obtain a temperature drop of 7.1 °C compared to the bare skin under direct sunlight. Given the excellent optical and cooling properties, flexibility, and self-cleaning property, PRCT was demonstrated to be a potential candidate for commercial applications in multifarious complex scenarios to afford a style for global decarbonization.

Anisotropic and Amphiphilic Mesoporous Core-Shell Silica Microparticles Provide Chemically Selective Environments for Simultaneous Delivery of Curcumin and Quercetin.

Porous silica materials are often used for drug delivery. However, systems for simultaneous delivery of multiple drugs are scarce. Here we show that anisotropic and amphiphilic dumbbell core-shell silica microparticles with chemically selective environments can entrap and release two drugs simultaneously. The dumbbells consist of a large dense lobe and a smaller hollow hemisphere. Electron microscopy images show that the shells of both parts have mesoporous channels. In a simple etching process, the properly adjusted stirring speed and the application of ammonium fluoride as etching agent determine the shape and the surface anisotropy of the particles. The surface of the dense lobe and the small hemisphere differ in their zeta potentials consistent with differences in dye and drug entrapment. Confocal Raman microscopy and spectroscopy show that the two polyphenols curcumin (Cur) and quercetin (QT) accumulate in different compartments of the particles. The overall drug entrapment efficiency of Cur plus QT is high for the amphiphilic particles but differs widely between Cur and QT compared to controls of core-shell silica microspheres and uniformly charged dumbbell microparticles. Furthermore, Cur and QT loaded microparticles show different cancer cell inhibitory activities. The highest activity is detected for the dual drug loaded amphiphilic microparticles in comparison to the controls. In the long term, amphiphilic particles may open up new strategies for drug delivery.

Bis(zinc(II)-dipicolylamine)-functionalized sub-2 \u03bcm core-shell microspheres for the analysis of N-phosphoproteome

Protein N-phosphorylation plays a critical role in central metabolism and two/multicomponent signaling of prokaryotes. However, the current enrichment methods for O-phosphopeptides are not preferred for N-phosphopeptides due to the intrinsic lability of P-N bond under acidic conditions. Therefore, the effective N-phosphoproteome analysis remains challenging. Herein, bis(zinc(II)-dipicolylamine)-functionalized sub-2 μm core-shell silica microspheres (SiO2@DpaZn) are tailored for rapid and effective N-phosphopeptides enrichment. Due to the coordination of phosphate groups to Zn(II), N-phosphopeptides can be effectively captured under neutral conditions. Moreover, the method is successfully applied to an E.coli and HeLa N-phosphoproteome study. These results further broaden the range of methods for the discovery of N-phosphoproteins with significant biological functions.

Research progress on core-shell silica stationary phases for high performance liquid chromatography

Fast and efficient separation by using high performance liquid chromatography (HPLC) is challenging for a wide range of samples. In recent years, core-shell silica microspheres have been widely investigated and used for highly efficient and fast separation under reasonably low pressure for small solutes, biopolymers, and complex samples. In this paper, the mechanism for fast separation and preparation methods of core-shell silica microspheres are introduced, along with their application for HPLC-based separation of small molecules, peptides, and biological macromolecules in HPLC. The developing trends of using core-shell microspheres in HPLC are also presented.

One-pot synthesis of SiO2@SiO2 core-shell microspheres with controllable mesopore size as a new stationary phase for fast HPLC separation of alkyl benzenes and β-agonists.

Monodisperse SiO2@SiO2 core-shell silica microspheres (CSSM) with enlarged mesopores perpendicular to the particles surface were prepared using a dual-templating approach. With cetyltrimethyl ammonium bromide as the template and octyltrimethyl ammonium bromide as an auxiliary chemical, the pore size can be enlarged from 2.6 to 10.6nm. The average shell thickness can be increased from 31nm to 97nm by adjusting the concentrations of the surfactants under continuous addition of tetraethyl orthosilicate. After coating twice, the resulting CSSM has a uniform mesoporous shell of about 198nm thickness and a narrow pore size distribution. The CSSM were then modified with octadecyltrichlorosilane to give a material referred to as CS-C18. It was evaluated by separating the mixture of methylbenzene (toluene), ethylbenzene, n-propylbenzene, n-butylbenzene, n-amylbenzene and hexylbenzene. The baseline separation of the six alkyl benzenes is achieved within 2min. Compared to a commercial column of type BEH-C18, CS-C18 shows a faster and better separation even at lower back pressure. It was also applied to the fast separation of benzo[a]pyrene, salbutamol, ractopamine and clenbuterolin residues in pork samples. The high column efficiency and better reproducibility suggest that the CSSM can be used as a matrix for fast separation and analysis of several kinds of small analytes. Graphical abstract A dual-templating approach was utilized to produce the core shell microsphere with controllable mesopore channels by using hexadecyltrimethylammonium bromide (CTAB) as the template and trioctylmethylammonium bromide (TOMAB) as an auxiliary chemical to enlarge the size of CTAB micelles.

Hybrid Organic-Inorganic Materials Containing a Nanocellulose Derivative as Chiral Selector.

Hybrid organic-inorganic materials (HOIM), with high mechanical stability, large surface area, tailored pore size, controlled morphology, and organic loading have shown superior chiral separation performance. In this chapter, the preparation of hybrid organic-inorganic materials of core-shell silica microspheres by a layer-by-layer self-assembly method is described. The enantioseparation performance by high-performance liquid chromatography is illustrated by various types of chiral compounds under normal- and reversed-phase elution conditions. The chiral selector of nanocrystalline cellulose derivative hybrid organic-inorganic materials showed good performance in the separation of enantiomers.

Multifunctional core-shell silica microspheres and their performance in self-carrier decomposition, sustained drug release and fluorescent bioimaging

An ideal nanocarrier system for drug delivery is that one made from biocompatible and biodegradable materials for safe excretion from the biological system, and often with additional imaging abilities. In the present work, new core-shell silica microspheres have been prepared, with carrier decomposition after drug release. Paclitaxel, which is one of the most efficient drugs against a wide range of malignancies was integrated into the silica core. The carrier decomposition resulted from the escape of drug molecules with loading capacity about 16.95%. To achieve the fluorescents properties of the synthesized material a biocompatible photoluminescent prepared carbon dots were inserted in a silica shell around the Ptx-SiO2 core. The resultant silica core-shell (Ptx-SiO2CDs-SiO2) NPs with average particle size around ~100 nm showed high fluorescent properties from the confocal laser scanning microscope observation. Further observation under UV-light at 365 nm also confirmed the photoluminescence. The Ptx-SiO2@CDs-SiO2 NPs were highly water soluble, and provide a sustained drug release as well as pH sensitivity. The incubation of A549 cells line with Ptx-SiO2@CDs-SiO2 NPs exhibits high cellular uptake as shown by CDs imaging. These properties in addition to the biocompatibility of Ptx-SiO2@CDs-SiO2 NPs and biodegradability of the silica core contributed simultaneously with the drug release process for easy body excretion after its functionality via renal system.

Fabrication of poly(o-anisidine) coated silica core–shell microspheres and their electrorheological response

In this work, silica/poly(o-anisidine) (POA) core–shell structured microspheres were synthesized by coating the silica core surface with POA with a help of a chemical grafting agent, N-[(3-trimethoxylsilyl)-propyl] aniline. The synthesized silica microspheres were then applied as a polymer/inorganic composite particle-based electrorheological (ER) fluid. The morphology of the silica/POA microspheres was examined by using both transmission electron microscopy and scanning electron microscopy, while their thermal properties and chemical structure were checked by thermogravimetric analysis and Fourier-transform infrared spectroscopy, respectively. The ER properties of the silica/POA particle-based ER fluid were examined by using a Couette-type rotational rheometer equipped with a high-voltage power supplier and analyzed by the Bingham model and modified Mason number. In order to obtain additional information about the electrical polarization properties, the dielectric spectra were measured by an LCR meter and fitted by using the Cole–Cole equation. Furthermore, suspension stability of the ER fluid was tested using Turbiscan.

Synthesis of SiO2@SiO2 core-shell microspheres using urea-formaldehyde polymers as the templates for fast separation of small solutes and proteins

Superficially porous core-shell silica microspheres (CSSMs) have been a great success for the fast separation of small molecules and proteins in recent years. In this paper, the CSSMs were synthesized by an improved polymerization-induced colloid aggregation (PICA) method using urea-formaldehyde polymers as the templates. The agglomeration of the functionalized silica core was avoided by the surface modification through reflux with ureidopropyltrimethoxysilane in the neutral ethanol solution at 80°C, and the secondary nucleation of the silica nanoparticles during the preparation process could also be inhibited via the optimization of the reaction conditions, such as pH, temperature, colloidal silica sol concentration and the reaction time. The controllable shell thickness and pore size of the synthesized monodisperse CSSMs were successfully obtained by adjusting the weight ratio of silica core/colloidal silica sol and the particle size of colloidal silica sol, respectively. The C18-modified CSSMs with different pore sizes were used to separate small solutes and proteins. The higher efficient separation and relatively low back pressure of the synthesized core-shell column demonstrate that the CSSMs have a great potential application for fast HPLC

Preparation of superficially porous core-shell silica particle with controllable mesopore by a dual-templating approach for fast HPLC of small molecules

A novel strategy to synthesize the monodisperse superficially porous core-shell silica microspheres (CSSMs) with enlarged mesopore channels perpendicular to the particles surface using a dual-templating approach was presented for the first time. With hexadecyl trimethyl ammonium bromide (CTAB) as the template and trioctylmethylammonium bromide (TOMAB) as an auxiliary chemical to enlarge the size of CTAB micelles, the pore size can be enlarged from 2.6nm to 10.6nm, the mesopore channels perpendicular to the surface of CSSMs can be obtained. The particles synthesized in this work have a uniform mesoporous shell of about 198.3nm in thickness over the silica core and possess a surface area of ca. 85.1m2/g, and narrow pore size distribution. This preparation method is highly versatile, controllable and easy to operate. The CSSMs obtained were modified with octadecyltrichlorosilane (ODS) to separate the alkyl benzene homologues. The higher efficient separation with fast flow rate and relatively low back pressure of the synthesized column demonstrate that the CSSMs have a great potential application for fast separation and analysis of small solutes with high performance liquid chromatography (HPLC).

Controllable Fabrication of Ag Nanoparticles-Coated Silica Core–Shell Microspheres and Its Optical Properties.

This paper described a one-step shell growth and extraordinarily facile method for the preparation of Ag nanoparticles-coated silica core–shell microspheres. The Ag nanoparticles could deposit on the silica microspheres to form continuous and compact shell layers at a balanced amount of polyvinyl pyrrolidone after the surface modification of the silica microspheres by (3-Mercaptopropyl) trimethoxysilane. The strong interactions between the thiol groups and Ag nanoparticles make it difficult to peel off the Ag shell from the core microspheres, obtaining extremely stable and homogeneous Ag nanoparticles-coated silica core–shell microspheres. Besides, the coating effect was controlled by varying the content of coupling agent, the type and amount of stabilizing agent, the quantity of silica microspheres as well as the mixing time between silica and silver ammonia solution. In addition, these Ag nanoparticles-coated silica core–shell microspheres were characterized using laser particle size analyzer (LPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The optical properties of the composite microspheres were observed by UV-vis spectroscopy.

Nanocellulose Derivative/Silica Hybrid Core-Shell Chiral Stationary Phase: Preparation and Enantioseparation Performance.

Core-shell silica microspheres with a nanocellulose derivative in the hybrid shell were successfully prepared as a chiral stationary phase by a layer-by-layer self-assembly method. The hybrid shell assembled on the silica core was formed using a surfactant as template by the copolymerization reaction of tetraethyl orthosilicate and the nanocellulose derivative bearing triethoxysilyl and 3,5-dimethylphenyl groups. The resulting nanocellulose hybrid core-shell chiral packing materials (CPMs) were characterized and packed into columns, and their enantioseparation performance was evaluated by high performance liquid chromatography. The results showed that CPMs exhibited uniform surface morphology and core-shell structures. Various types of chiral compounds were efficiently separated under normal and reversed phase mode. Moreover, chloroform and tetrahydrofuran as mobile phase additives could obviously improve the resolution during the chiral separation processes. CPMs still have good chiral separation property when eluted with solvent systems with a high content of tetrahydrofuran and chloroform, which proved the high solvent resistance of this new material.

Synthesis of nanospheres-on-microsphere silica with tunable shell morphology and mesoporosity for improved HPLC.

Core-shell particles have a wide range of applications. Most of the core-shell particles are prepared in two or multiple steps. Core-shell silica microspheres, with solid core and porous shell, have been used as novel packing materials in recent years for highly efficient liquid chromatography separation with relatively low back-pressure. These core-shell silica microspheres are usually prepared by the time-consuming layer-by-layer technique. Built on our previous report of one-pot synthesis of core-shell nanospheres-on-microspheres (termed as SOS particles for "spheres-on-spheres"), we describe here a two-stage synthesis for the introduction of shell mesoporosity into SOS particles with tunable shell morphology by co-condensation of tetraethyl orthosilicate (TEOS) with 3-mercaptopropyltrimethoxysilane (MPTMS) in the presence of surfactant in the second stage. With MPTMS as the primary precursor at the first stage, some other silica precursors (apart from TEOS) are also employed at the second stage. Expansion of the surfactant-templated mesopores with swelling agents during the reaction and by hydrothermal postsynthesis treatment is then performed to allow the pore sizes (> 6 nm) suitable for separation of small molecules in liquid chromatography. Compared to the standard SOS silica (both the nanospheres and microspheres contain nearly no mesopores), the introduction of mesoporosity into the nanosphere shell increases the separation efficiency of small molecule mixtures by 4 times as judged by the height equivalent plate number, while the separation of protein mixtures is not negatively affected.

Surface imprinting approach for preparing specific adsorbent for IgG separation

In this study, we focused our attention on preparing of a new adsorbent for specific separation of immunoglobulin G (IgG). In this respect, we applied core–shell surface imprinting approach. Silica microspheres were selected as core-material to prepare specific surface imprinted polymer against IgG. Silica surface was activated via acidic treatment and modified with 3-methacryloyloxypropyl trimethoxysilane (MPTMS). Then, IgG molecules were imprinted on the surface of microspheres by using N-methacryloyl-L-aspartic acid as complexing/functional monomer. The core–shell silica microspheres were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, thermo gravimetric analysis and zeta size analysis. Then, the microspheres were used for the separation of IgG from aqueous solution to evaluate/optimize conditions. The effect of parameters such as concentration, pH, ionic strength, and temperature on the separation of IgG were evaluated in their relevant ranges. The maximum IgG adsorption capacities of IgG-imprinted and non-imprinted core–shell silica microspheres were found to be 15.43 and 9.43 mg/g, respectively, at pH 6.0 phosphate buffer. 1.0 M NaCl was used as a desorption agent. Selectivity of the imprinted microspheres was also investigated by using human serum albumin and haemoglobin as competitor molecules.

Solid-phase extraction approach for phospholipids profiling by titania-coated silica microspheres prior to reversed-phase liquid chromatography-evaporative light scattering detection and tandem mass spectrometry analysis.

A novel strategy for selectively adsorbing phospholipids (PLs) on titania-coated silica core-shell microspheres (TiO2/SiO2) was developed. The TiO2/SiO2 microspheres were prepared through water-vapor-induced internal hydrolysis and then characterized by SEM, UV-vis spectroscopy, X-ray diffraction, and measurements of Brunauer-Emmett-Teller surface area. Analyses showed that the titania layer was uniformly distributed onto the surface of silica particles. The TiO2/SiO2 microspheres were employed as sorbent in solid-phase extraction (SPE), and their absorptive ability was investigated by reversed-phase liquid chromatography-evaporative light scattering detection (RPLC-ELSD). Important factors that affect the extraction, such as loading buffer, eluting buffer, and elution volume, were investigated in detail and optimized by using standard samples. Results reveal that the developed SPE approach had higher recoveries for PLs than that based on pure TiO2 particles. The proposed SPE method was used for extraction of PLs from serum and showed great potential for identifying more kinds of endogenous PL metabolites by ultra performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-QTOF MS). The proposed SPE method with the composite sorbent was used to screen PLs from a biological matrix with high selectivity and efficiency. This approach is a promising method for selective extraction of PLs in lipidomics or phospholipidomics.

Cellular uptake of ribonuclease A-functionalised core-shell silica microspheres.

Analysis of protein function in a cellular context ideally requires physiologically representative levels of that protein. Thus conventional nucleic acid-based transfection methods are far from ideal owing to the over expression that generally results. Likewise, fusions with protein transduction domains can be problematic whilst delivery via liposomes/nanoparticles typically results in endosomal localisation. Recently, polymer microspheres have been reported to be highly effective at delivering proteins into cells and thus provide a viable new alternative for protein delivery (protein transduction). Herein we describe the successful delivery of active ribonuclease A into HeLa cells via novel polymer core-silica shell microspheres. Specifically, poly(styrene-co-vinylbenzylisothiouronium chloride) core particles, generated by dispersion polymerisation, were coated with a poly(styrene-co-trimethoxysilylpropyl methacrylate) shell. The resultant core-shell morphology was characterised by transmission electron, scanning electron and confocal fluorescence microscopies, whilst size and surface charge was assessed by dynamic light scattering and zeta-potential measurements, respectively. Subsequently, ribonuclease A was coupled to the microspheres using simple carbodiimide chemistry. Gel electrophoresis confirmed and quantified the activity of the immobilised enzyme against purified HeLa RNA. Finally, the polymer-protein particles were evaluated as protein-transduction vectors in vitro to deliver active ribonuclease A to HeLa cells. Cellular uptake of the microspheres was successful and resulted in reduced levels of both intracellular RNA and cell viability.

Preparation of Zirconia Silica Core Shell Microspheres and Its Application for Highly Specific Phospholipids Enrichment

A strategy for selectively enrich phospholipids(PLs) using zirconia coated silica(ZrO2/SiO2) core-shell microspheres was developed.ZrO2/SiO2 was first prepared by NH3/H2O vapor-induced internal hydrolysis method,and characterized by SEM and UV-VIS.The results showed zirconia layer was coated on the surface of silica indeed.A method of reversed phase-high performance liquid chromatography-evaporative light scattering detector(RP-HPLC-ELSD) for the analysis of phospholipid standards was also established.A good separation of five standards was achieved by using methanol-water(including ammonium acetate) as mobile phase.Based on these methods,the absorption ability of ZrO2/SiO2 microspheres packed into the solid phase extraction(SPE) towards PLs was investigated.The results demonstrated ZrO2/SiO2 SPE column had a much higher selectivity and higher recoveries than those of bulk ZrO2 particles.In addition,the best recovery rate of PLs was obtained from 3.5% ZrO2/SiO2 materials.At last,the ZrO2/SiO2 microsphere was also applied to enrich endogenous phospholipids form human serum,and more metabolites were found by using ZrO2/SiO2 SPE column.

Controlled Synthesis of Monodisperse SiO2TiO2Microspheres with a Yolk–Shell Structure as Effective Photocatalysts

Monodisperse yolk-shell SiO(2) -TiO(2) microspheres were synthesized using core-shell silica microspheres as templates. In the absence of prior surface modifications, a uniform coating of the TiO(2) layer on the core-shell silica was achieved through a sol-gel route. Mesoporous silica shells between the outer TiO(2) shell and the SiO(2) core were selectively removed by using a weak base, yielding yolk-shell SiO(2) -TiO(2) microspheres (ys-SiO(2) @TiO(2) ). Using the same templates, we synthesized Pt-encased microspheres (SiO(2) @Pt-TiO(2) ), in which Pt nanoparticles are embedded between the SiO(2) core and the TiO(2) shell. Selective etching of the silica shells in SiO(2) @Pt-TiO(2) yields Pt-encased yolk-shell SiO(2) -TiO(2) microspheres (ys-SiO(2) @< Pt >TiO(2) ), which contain void spaces suitable for use as nanoreactors. The ys-SiO(2) @< Pt >TiO(2) catalyst shows enhanced hydrogen production from water under UV-light irradiation presumably as a result of multiple reflections within the void spaces and can be reused without losing their activity. Moreover, this core-shell template method is effective for the synthesis of other yolk-shell microspheres with different metal oxides.