Mesoporous Silica Spheres Research Articles

Characteristics of CO2 Capture by Tetraethylenepentamine Modified Mesoporous Silica Morphology

The objective of the study is to investigate the morphology effects of porous silica supports on the CO₂ capture performance of solid amine adsorbents. Mesoporous hollow silica spheres (MHSS) and mesoporous silica spheres (MSS) were synthesized and modified by wet impregnation with tetraethylenepentamine (TEPA) as solid adsorbents. The prepared adsorbents were characterized by TEM, XRD, N₂ adsorption/desorption, FT-IR, and TGA. The CO₂ capture performances of the adsorbents were evaluated using a flow method at atmospheric pressure. Gas chromatography was used to analyze the CO₂ concentration in the influent and effluent gas streams. Due to the excellent structural properties of the MHSS, it was found to be a better amine support than MSS. An increase in the amount of loaded TEPA improved the CO₂ adsorption capacity of the prepared adsorbents. The optimum CO₂ adsorption capacities were obtained with MHSS-47 and MSS-41.

Evaluating the internal structure of monodispersed mesoporous silica spheres by small-angle X-ray scattering

Although the spherical morphology and mesoporous structure of monodispersed mesoporous silica spheres (MMSS) have been extensively investigated by scanning electron microscopy and transmission electron microscopy, the statistical distribution of mesopores from the surface to the center of a particle, average density of the spheres, and volume fraction of silica have not been investigated. Herein, small-angle X-ray scattering (SAXS) was performed on aqueous dispersions of MMSS with diverse sphere diameter, mesopore radius, and nanoparticle inclusion. The SAXS spectra fitted by a spherical model showed that the mesopores were homogeneously distributed in each particle. The mass density of the MMSS was obtained from the zero scattering intensity, and the volume fraction of silica was calculated considering the absorbed water in the pores. While the sphere diameter and mesopore radius had little influence, nanoparticle inclusion induced an increase in the volume fraction of silica.

Facile preparation of redox-responsive hollow mesoporous silica spheres for the encapsulation and controlled release of corrosion inhibitors

The redox-responsive hollow mesoporous silica sphere (HMSS) as smart nanocontainer demonstrates great potential for active agent storage and controlled release. In the present work, HMSS was firstly prepared by surfactant assisted selective etching method. Then, target corrosion inhibitors, 2-mercaptobenzothiazole (MBT) molecules, were loaded and encapsulated with redox-responsive supramolecular nanovalves, ZnO quantum dots. Results reveal that obtained HMSS exhibits a hierarchical mesoporous structure consisting of hollow cavity and mesoporous shell. Corrosion inhibitors were successfully loaded and capped in HMSS nanocontainers, showing on-demand release behavior under specific environment. Moreover, the release efficiency gradually increased with increasing dosage of the reducing agent. Therefore, the novel smart nanocontainers with redox-responsive characteristics will offer a great promise for the development of new generation nano delivery system for corrosion protection accompanying redox environment change.

Experimental Assessment of the Structural Parameters of Highly Porous Silica: Probe Microscopy Data

The morphology of monodisperse spherical mesoporous silica particles with a regular pore structure is studied with atomic force microscopy. The size of nanotubes is found: the internal diameter is 2.6 nm, the external diameter is 4.8 nm, and the wall thickness is 1.1 nm. A method for assessing the strength parameters of highly porous materials is proposed. The calculated Young’s modulus of a nanotube along its axis is 91.7 GPa.

Organic Functionalization of Mesoporous Silica Spheres as a Nanovehicle for DOX pH-Triggered Delivery

Mesoporous silica (MS) spheres of different sizes with pH-responsive characteristics were synthesized based on Stöber’s theory. Organic functionalization with aminopropyl and carboxyl groups resulted in different materials, namely, MS@NH2@COOH. MS@NH2@COOH were observed to have a large number of carboxyl groups and multiamine chains, and were grafted into pore channels and pore outlets through systematic characterization analyses. All modified samples demonstrated the controlling of the delivery rate of DOX from the siliceous matrix. We also compared the drug release behavior of the DOX-loaded materials at high pH (7.4) and low pH (5.5) and studied the cytotoxicity on A549 cells. The experimental results indicated that the drug delivery system can better control drug release and have potential applications in the drug delivery field.

Encapsulated ultrafine and highly dispersed molybdenum dioxide nanoparticles in hollow mesoporous silica spheres as an efficient epoxidation catalyst for alkenes

A facile post-synthetic strategy was developed to functionalize the preformed hollow mesoporous silica spheres by encapsulating the molybdenum dioxide (MoO2) nanoparticles inside the interior cavity. Hollow mesoporous silica spheres were prepared and employed as carriers, and the encapsulation of MoO2 nanoparticles was achieved through a one-pot hydrothermal protocol. After characterization, the encapsulated MoO2 nanoparticles were certified to be ultrafine and highly dispersed, which greatly promoted the catalytic activity. The as-prepared catalysts were utilized in epoxidation of alkenes and exhibited as a promising catalyst in this reaction. After reacting for 10 h, the optimal catalyst MoO2@SiO2-1 achieved a conversion above 95% and selectivity above 95%, respectively. Moreover, the catalysts also exhibited good reusability, conversion of 78% and selectivity of 89% (reaction time 4 h) were still obtained after recycling for 5 times. Meanwhile, the employed facial and efficient hydrothermal approach could be expanded to other molybdenum modified heterogeneous catalysts in various applications.

Eye-Readable Detection and Oxidation of CO with a Platinum-Based Catalyst and a Binuclear Rhodium Complex.

Toxic gases that are colorless and odorless, such as CO, are a major environmental concern and require early detection to prevent serious toxicological effects. In this study, a unique system (Pt/HMSs-BRC) was fabricated by combining a catalyst (Pt/hollow mesoporous silica spheres, Pt/HMSs) with a silica gel containing an adsorbed chromogenic probe (binuclear rhodium complex, BRC). The process is a simple method to prepare well-dispersed and uniform Pt nanoparticles. The Pt/HMSs-BRC materials demonstrated early CO detection and excellent catalytic performance for CO oxidation. The probe exhibited remarkable color modulation from gray-violet to light-yellow when exposed to CO concentration levels above 50 ppm, and the color of the chromogenic probe was fully recoverable. By a kinetics-assisted discrimination method and DFT calculations, it was found that the corner Pt sites are the dominant active sites for CO oxidation.

Eye‐Readable Detection and Oxidation of CO with a Platinum‐Based Catalyst and a Binuclear Rhodium Complex

AbstractToxic gases that are colorless and odorless, such as CO, are a major environmental concern and require early detection to prevent serious toxicological effects. In this study, a unique system (Pt/HMSs‐BRC) was fabricated by combining a catalyst (Pt/hollow mesoporous silica spheres, Pt/HMSs) with a silica gel containing an adsorbed chromogenic probe (binuclear rhodium complex, BRC). The process is a simple method to prepare well‐dispersed and uniform Pt nanoparticles. The Pt/HMSs‐BRC materials demonstrated early CO detection and excellent catalytic performance for CO oxidation. The probe exhibited remarkable color modulation from gray‐violet to light‐yellow when exposed to CO concentration levels above 50 ppm, and the color of the chromogenic probe was fully recoverable. By a kinetics‐assisted discrimination method and DFT calculations, it was found that the corner Pt sites are the dominant active sites for CO oxidation.

Comparison of Polydopamine-Coated Mesoporous Silica Nanorods and Spheres for the Delivery of Hydrophilic and Hydrophobic Anticancer Drugs.

Mesoporous silica nanoparticles (MSNs) have been widely studied as drug delivery systems in nanomedicine. Surface coating of MSNs have enabled them to perform efficiently in terms of bioavailability, biocompatibility, therapeutic efficacy and targeting capability. Recent studies have suggested the use of polydopamine (PDA) as a facilitative coating for MSNs that provides sustained and pH-responsive drug release, owing to the adhesive “molecular-glue” function of PDA. This further endows these hybrid MSN@PDA particles with the ability to carry large amounts of hydrophilic drugs. In this study, we expand the feasibility of this platform in terms of exploring its ability to also deliver hydrophobic drugs, as well as investigate the effect of particle shape on intracellular delivery of both a hydrophilic and hydrophobic anticancer drug. MSN@PDA loaded with doxorubicin (hydrophilic) and fingolimod (hydrophobic) was studied via a systematic in vitro approach (cellular internalization, intracellular drug distribution and cytotoxicity). To promote the cellular uptake of the MSN@PDA particles, they were further coated with a polyethylene imine (PEI)-polyethylene glycol (PEG) copolymer. Drug-loaded, copolymer-coated MSN@PDA showed effective cellular uptake, intracellular release and an amplified cytotoxic effect with both doxorubicin and fingolimod. Additionally, rods exhibited delayed intracellular drug release and superior intracellular uptake compared to spheres. Hence, the study provides an example of how the choice and design of drug delivery systems can be tuned by the need for performance, and confirms the PDA coating of MSNs as a useful drug delivery platform beyond hydrophilic drugs.

Preparation of three-dimensional dendritic-like mesoporous silica particles and their pore size-dependent polishing behavior and mechanism

The type and structure of abrasive particles play a key role in the involved friction and wear processes during chemical mechanical polishing (CMP). This work aims to develop silica-based abrasives that improve both surface finish and removal rate. The uniform, three-dimensional, and dendritic-like mesoporous silica (D-mSiO2) spheres with sub-100 nm size were synthesized in a heterogeneous oil–water biphase reaction system. The pore size of 3D-dendritic channels could be adjusted by regulating hydrophobic solvents in the upper oil phase. The improvements of root-mean-square roughness (0.18–0.26 nm) and removal rate (192–260 nm/min) were achieved for the D-mSiO2 particles compared to colloidal silica abrasives (0.37 nm, 112 nm/min). A reduction from 2.90 to 0.48 and 2.60 to 0.42 nm for the maximum asperity height and the maximum valley depth respectively was also observed after CMP with D-mSiO2 abrasives. Furthermore, the D-mSiO2 particles with an enlarged pore size achieved a reduced surface roughness and an enhanced removal rate. The improved polishing performance may be attributed to the enlarged real contact area, the promoted tribo-chemical wear, and the enhanced adhesion effect between particles and surfaces. The contact area mechanism and the contact-penetration-adhesion model may be predominant and significant for D-mSiO2 abrasives, rather than the traditional the indentation-based mechanism and the indentation-sliding model. The unique three-dimensional mesopores of D-mSiO2 abrasives are expected to play key role in material removal processes, and it will have more hopeful prospects in CMP performance improvements.

Time- and dose-dependent gene expression analysis of macrophage response as a function of porosity of silica nanoparticles

There is a limited amount of information available on gene expression regulation of macrophages in response to changing the time of exposure, concentration, and physicochemical properties of nanomaterials. In this study, RAW264.7 macrophages were treated with spherical nonporous and mesoporous silica nanoparticles of similar size at different incubation times and concentrations. RNA-sequencing was used to study transcriptional profiles. Bioinformatics analyses, functional annotation clustering, and network analyses were employed to understand signaling pathways of cellular response as a function of porosity, incubation time, and concentration. Porosity introduced drastic changes to the genomic response of macrophages at equitoxic concentrations and incubation times. Direct relations between increases in time and concentration with an increased number of differentially expressed genes were observed.

Inducing Macrophages M2 Polarization by Dexamethasone Laden Mesoporous Silica Nanoparticles from Titanium Implant Surface for Enhanced Osteogenesis

The study conveys an idea to enhance the osseointegration of titanium implant (Ti) through modulating macrophages M2 polarization. The ~ 100 nm spherical mesoporous silica nanoparticles (MSN) that compromised of ~ 4-nm-diameter nano-tunnels were synthesized by the conventional “sol–gel” method, into which the dexamethasone (DEX) was loaded (DEX@MSN). The DEX@MSN could consistently release DEX and showed favorable cytocompatibility in RAW264.7 cells. The arginase-1 expression, a specific marker for macrophages M2 polarization, was also enhanced by DEX@MSN treatment. Then, the Ti was pre-treated with anodization under 5 V to generate the titania nanotubes with ~ 30 nm diameter (NT-30) and the DEX@MSN was introduced onto NT-30 surface via electrophoretic deposition, with the aid of chitosan. After optimizing the deposition parameters, the supernatants of RAW264.7 from the decorated implant surface could significantly promote the osteogenic differentiation of murine primary bone marrow mesenchymal stem cells. These findings demonstrate that delivery of DEX from implant surface can modulate the macrophages M2 polarization and result in favorable osteogenesis.

Porous N-doped carbon nanostructure integrated with mesh current collector for Li-ion based energy storage

A self-assembled mesoporous silica sphere templating process was developed to create hierarchical continuous porous coral reef like N-doped carbon nanostructures on stainless steel meshes as bifunctional electrodes for ultrahigh performance lithium ion based energy storage devices. The coral reef like carbon nanostructure achieved a high specific surface area of 1229 m2 g−1 and a large specific pore volume of 2.21 cm3 g−1, without application of chemical activations. The electrode, when serving as an anode for lithium ion batteries (LIB) or lithium ion capacitors (LIC), delivered an ultrahigh specific capacity of 2058 mAh g−1 at 0.2 A g−1. If used as a cathode for LICs, it generated a high specific capacity of 125 mAh g−1 at 0.1 A g−1. The LICs assembled from using the electrode as both the cathode and anode, exhibited a high energy density of 145 Wh kg−1 at a power density of 1.4 kW kg−1 and maintained an energy density of 58 Wh kg−1 under an ultrahigh power density of 27.3 kW kg−1, among the top tie of the state-of-the-art LICs. The cycling stability of the LIC was outstanding with a 85% capacity retention after 5000 cycle operations at 5 A g−1. The hierarchical continuous porous coral reef like N-doped carbonaceous nanostructure provides micropores as micro-reservoirs of Li ions for local and fast Li ion intercalation/de-intercalation, edge N-doping for additional redox pseudo-capacitances, and large pore volumes to accommodate the volume expansion/shrinkage at the charge/discharge cycles and to offer fast mass transfer path for electrolyte ions, altogether leading to the successful applications as bifunctional electrodes for Li ion based energy storage devices.

Facile synthesis of amino-functional large-size mesoporous silica sphere and its application for Pb2+ removal

Amino-functional large-size mesoporous silica spheres (LMS-AP) were successfully synthesized through a one-step method with (3-aminopropyl) triethoxysilane (APTES) addition during the pseudomorphic transformation process. LMS-AP were characterized using thermogravimetry-differential thermal analysis, Nitrogen adsorption-desorption measurement, infrared spectroscopy, and X-ray photoelectron spectroscopy. The study found that -NH2 was grafted into LMS, and the LMS-AP had a better thermal stability than other samples. The Pb2+ removal properties of LMS-AP were investigated using the static and dynamic experiments in simulated and real wastewater solutions. The kinetic and equilibrium experiments indicated that the adsorption process of LMS-AP fitted the Langmuir adsorption model and the pseudo-second-order kinetics model (R2 > 0.98), respectively. The maximum Qe (mg/g) was about 100 mg/g in the static adsorption condition. The adsorption mechanism of removal of Pb2+ was also investigated. In fix bed column experiments, LMS-AP exhibited excellent Pb2+ adsorption ability for simulated wastewater, with the maximum qe (mg/g) of 48.7 mg/g for particle size under 1-3 mm. Meanwhile in actual industrial wastewater treatment process, LMS-AP had a better Pb2+, Zn2+ and Cr (VI) removal efficiency of 80% and As (V) of 30-40% removal efficiency at initial pH 4, suggesting selective adsorption property for different heavy metal ions.

Cr doped mesoporous silica spheres for propane dehydrogenation in the presence of CO2: Effect of Cr adding time in sol-gel process

Abstract CrOX-doped mesoporous silica spheres (Cr/MSS-X) were prepared by adding Cr precursors at different preparation stages using sol-gel method (X = 1, 2, 3) and incipient-wetness impregnation method (X = 4), and their catalytic performances of propane oxidative dehydrogenation were evaluated in the presence of CO2. The results indicate that for the Cr/MSS-X catalysts prepared by sol-gel method, Cr adding time significantly influences the Cr dispersion, surface physic-chemical properties and their catalytic performance. Cr/MSS-2 catalysts obtained by adding Cr precursor after the tetraethyl-orthosilicate (TEOS) show the optimal catalytic activity. Although Cr/MSS-1 also shows good CrOX dispersion, part CrOX wrapped in the center of mesoporous silica spheres presents weaker catalytic activity. In this work, the catalyst preparation method is quite facile and has the potential to be utilized for industrial production.

Ultrasonic-assisted synthesis of hollow mesoporous silica as a toxic gases suppressant

Here, we present a facile ultrasonic-assisted method to fabricate hollow mesoporous silica spheres. The prepared hollow mesoporous silica spheres own well-regulated size, large specific surface area, and homogeneous mesoporous. Time-dependent experimental results depict that the formation of the hollow spheres undergoes a selective etching process. The results of fire toxic tests show that the toxic gases decomposed from the combustion of epoxy resin were observably inhibited with the incorporation of hollow mesoporous silica.

Synthesis of phosphonate-containing mesoporous silica spheres under basic condition

Phosphonate-containing mesoporous silica (PMPS) spheres were successfully synthesized using diethyl(2-bromoethyl)phosphonate and non-ionic and cationic surfactants. The spherical PMPS particles with the mesopores were effectively formed under the basic condition through the hydrolysis and condensation reactions of tetraethoxysilane, even though the BET surface area of the particles decreased with increasing the added phosphonate amount. The hollow structures with the mesopores were obtained in the preferential amount of the phosphonate.

A Facile Route to Synthesize Micron Size Nearly Spherical Mesoporous Silica Particles

AbstractFor many applications as structured packing material, the micron size spherical silica particles with the bicontinuous mesoporous structures are required. Herein, we report a facile route to synthesize the micron size nearly spherical mesoporous silica (MSNSMS) particles. The chitosan is crucial in the synthesis strategy as an adjuvant agent to facilitate the formation of the micron size nearly spherical particles. The MSNSMS particles demonstrate narrow mesopore and particle size distributions with the average particle sizes at 3.6 μm (MSNSMS‐0.5) or 4.7 μm (MSNSMS‐1). The MSNSMS samples possess the large ordered domains of pure bicontinuous mesoporous structure with the interpenetrating cylindrical pores at about 8 nm in diameter. The MSNSMS particles are promising structured packing material candidate for catalyst support applications.

One-pot synthesis of alkylammonium-functionalized mesoporous silica hollow spheres in water and films at the air\u2013water interface

This paper reports a one-pot sol–gel approach for the synthesis of the alkylammonium-functionalized mesoporous silica particles with hollow structures and mesoporous silica films via hydrothermal reaction through the self-assembly of N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TMAPS) and tetraethoxysilane (TEOS) as a silica source, dodecyldimethyl(3-sulfopropyl)ammonium hydroxide (DDAPS) and fluorocarbon anion (ammonium perfluorooctanoate (APFO)) as the structure-directing agent. The alkylammonium-functionalized hollow mesoporous silica particles exhibited a different morphology, mesoporosity, and hollow structure with a layered mesostructure in the shell according to the DDAPS/APFO surfactant molar ratios (DDAPS/APFO = 3/1~1/9 or APFO in the range of 10~80 mM), reaction times (6~48 h), and reaction temperatures (45~95 °C). Alkylammonium-functionalized hollow mesoporous silica particles with spherical morphologies were produced from precipitation in the bottom of the reaction bottle after the hydrothermal reaction. At a DDAPS/APFO surfactant ratio of 1/3, reaction temperature of 60 °C, and reaction times of 24 h and 48 h, the alkylammonium-functionalized hollow mesoporous silica spheres displayed a multilayered mesostructure in the shell. The sphere size could be controlled from ca. 76 nm to ca. 350 nm with a shell thickness of ca. 35 nm. In addition, alkylammonium-functionalized mesoporous silica films were produced at the air–water interface, whereas hollow mesoporous silica spheres were produced with precipitation in the bottom of the reaction bottle. The film thickness was controlled from ca. 210 nm to ca. 400 nm.

Design and Preparation of Hallow Mesoporous Silica Spheres Include CuO and Its Catalytic Performance for Synthesis of 1,2,3-Triazole Compounds via the Click Reaction in Water

Here, a novel nanostructured catalyst based on CuO included hallow mesoporous silica spheres (CuO–HMSS) was prepared for synthesis of 1,2,3-triazole compounds. The hallow silica spheres were synthesized via the hydrothermal procedure. The characterization of prepared catalyst was also performed applying several analysis techniques such as TEM and SEM, EDX, XRD, and ICP. CuO active sites in a hollow mesoporous silica shell are stably and efficiently attainable for conversion of precursors to triazole compounds.