Cu-Kojic Acid Complex Anchored to Functionalized Silica-MCM-41: A Promising Regioselective and Reusable Nanocatalyst for Click Reaction

Cu-Kojic acid (KA) complex anchored to functionalized silica-MCM-41 was synthesized via the process of postgrafting and introduced as an effective, new, reusable, and thermally resistant heterogeneous nanocatalyst for the clean synthesis of 1H-1,2,3-triazoles from Click reaction of 2-(azidomethyl)-5-benzyloxy-4-pyrone and azido Kojic acid with a variety of terminal alkynes in excellent yields. The structure of nanocatalyst was analyzed by ICP, BET, XRD, EDS, SEM, TGA, TEM, and FT-IR techniques.

Tunable Effect of the Calcination of the Silanol Groups of KIT-6 and SBA-15 Mesoporous Materials

The calcination process is a crucial step during SBA-15 and KIT-6 synthesis. It is used to completely remove the organic template and condense silanol groups, and it allows the determination of the textural and physical properties of these materials, depending on the adopted conditions. Moreover, calcination influences the number of silanols available on the surface of the material. The concentration of silanols is important if these materials were synthesized for use in adsorption or functionalization. To understand and optimize the silanol groups of SBA-15 and KIT-6, in this study, the temperature and time calcination parameters were varied. The experiments were performed at 300, 400, and 500 °C for 300, 400, and 500 min. The results show that the ideal temperature to preserve the silanol groups is 300 °C, but to optimize the textural properties, it is better to calcine these molecular sieves at 400 °C. A calcination for 10 h did not give better results than a calcination for 5 h, demonstrating that the former duration is excessive for use.

Facile Fabrication of Flexible, Robust, and Superhydrophobic Hybrid Aerogel

Silica aerogels, which are constructed with silica nanoparticles and numerous nanoscale pores, have many outstanding attributes, but they are usually brittle and hydrophilic. For the construction of a robust aerogel, the novel polyhedral oligomeric silsesquioxane (POSS) was introduced to prepare a series of aerogels possessing particles covered with elastic cushion to improve the mechanical property. The multialkoxy POSS, which possessed stiff Si-O-Si nanocages and flexible alkyl chains, was synthesized via thiol-ene click chemistry. After a facile and efficient approach, a partially ordered structure of SiO₂ nanoparticles and organic elastic cushion would form spontaneously within the aerogels. With the POSS as the only precursor, several outstanding attributes were achieved in a single aerogel such as high specific surface area (SSA), high compression strength, high compression modulus, and noticeable compression flexibility. Meanwhile, the aerogel was superhydrophobic of which the contact angle (CA) was higher than 153°. Moreover, the potential application of oil-water separation is also presented.

Macrocyclic ligand decorated ordered mesoporous silica with large-pore and short-channel characteristics for effective separation of lithium isotopes: synthesis, adsorptive behavior study and DFT modeling

Effective separation of lithium isotopes is of strategic value which attracts growing attention worldwide. This study reports a new class of macrocyclic ligand decorated ordered mesoporous silica (OMS) with large-pore and short-channel characteristics, which holds the potential to effectively separate lithium isotopes in aqueous solutions. Initially, a series of benzo-15-crown-5 (B15C5) derivatives containing different electron-donating or -withdrawing substituents were synthesized. Extractive separation of lithium isotopes in a liquid-liquid system was comparatively studied, highlighting the effect of the substituent, solvent, counter anion and temperature. The optimal NH₂-B15C5 ligands were then covalently anchored to a short-channel SBA-15 OMS precursor bearing alkyl halides via a post-modification protocol. Adsorptive separation of the lithium isotopes was fully investigated, combined with kinetics and thermodynamics analysis, and simulation by using classic adsorption isotherm models. The NH₂-B15C5 ligand functionalized OMSs exhibited selectivity to lithium ions against other alkali metal ions including K(i). Additionally, a more efficient separation of lithium isotopes could be obtained at a lower temperature in systems with softer counter anions and solvents with a lower dielectric constant. The highest value separation factor (α = 1.049 ± 0.002) was obtained in CF₃COOLi aqueous solution at 288.15 K. Moreover, theoretical computation based on the density functional theory (DFT) was performed to elucidate the complexation interactions between the macrocyclic ligands and lithium ions. A suggested mechanism involving an isotopic exchange equilibrium was proposed to describe the lithium isotope separation by the functionalized OMSs.

The effect of compressed CO2 on the self-assembly of surfactants for facile preparation of ordered mesoporous carbon materials

The effect of compressed CO₂ on the properties of ordered mesoporous carbon (OMC) was investigated based on the self-assembly of surfactants in aqueous solution under mild conditions, and the acidic or basic conditions commonly used in traditional methods were substituted by compressed CO₂. Compressed CO₂ acts as both a physiochemical additive and a reagent to produce an acid catalyst in the synthesis. This new one-pot assembly approach can efficiently adjust the porous characteristics of OMC by employing different amounts of compressed CO₂, and the self-assembly mechanism is proposed. The spherical micelles formed by triblock copolymer Pluronic F127 serve as a structure-directing agent for the controllable synthesis of nanomaterials. Resorcinol/phloroglucinol and formaldehyde are used as carbon-yielding components. It was found that CO₂ can penetrate into the hydrocarbon-chain region of the F127 micelles, leading to template swelling and influencing the properties of OMC. The surfactant and precursors attracted by H-bonding interactions self-assemble and produce OMC after polymerization and carbonization. The resulting OMC as a supercapacitor electrode material exhibits outstanding specific capacitances, and the electrochemical performances change as the structural properties are varied.

New short-channel SBA-15 mesoporous silicas functionalized with polyazamacrocyclic ligands for selective capturing of palladium ions in HNO3 media

Novel polyazamacrocyclic ligand decorated short-channel mesoporous silicas with the ability to selectively capture palladium ions in HNO₃ solutions.

Three-Dimensionally Controllable Synthesis of Multichannel Silica Nanotubes and Their Application as Dual Drug Carriers

Three-dimensionally controllable multichannel silica nanotubes (MC-SNTs) have been constructed. Quaternary ammonium type (C_n H_2n+1 (CH₃ )₃ N⁺ ) surfactants were used as structure-directing agents (SDAs) in basic ammonia. A low concentration of block copolymer HO(CH₂ CH₂ O)₂₀ [CH₂ CH(CH₃ )O]₇₀ (CH₂ CH₂ O)₂₀ H (P123) was employed as an additive. The length, diameter, and pore size of MC-SNTs can be finely controlled in the range of 50 nm to 5 μm, 50 nm to 350 nm, and 2 nm to 3 nm by changing the molar ratio of P123 and SDA, the concentration of ammonia, and the length of carbon chain of SDAs, respectively. Observations based on transmission electron microscopy confirmed the role of P123 and ammonia in the self-assembly of micelles of SDA. Compared with the one-pot method reported previously, the aspect ratios (ARs; length/diameter) of obtained MC-SNTs were tunable in a wide range of approximately 1 to 100. The tunable MC-SNTs were used as dual drug-delivery carriers for anticancer drug doxorubicin (Dox) and anti-inflammatory drug ibuprofen (Ibu). Results of release behavior and toxicity to cancer cells of Dox-Ibu-loaded MC-SNTs with different ARs revealed that Dox and Ibu were successfully codelivered and did not interfere with each other. The produced MC-SNTs with larger AR values of showed advantages in the amount of accumulated dual drugs, the duration time of release, and inhibition of the growth of HeLa cells.

Enhancing adsorption efficiency of dichloroacetic acid onto mesoporous carbons: Procedure optimization, mechanism and characterization

Highly ordered mesoporous carbon may be directly synthesized via supramolecular self-assembly with in situ evaporation-induced crystallization process by controlling thermal reaction temperatures and carbon mass loading. In the present study, the effects of thermal reaction temperatures on the structural characterization and adsorption capacity of mesoporous carbon have been investigated and analyzed with orthogonal test experiments. The results show the carbonization temperature (R=32.1) plays a more important role than the self-assembly temperature (R=8.5) and thermal polymerization temperature (R=10.1) in manipulating the pore texture structures. The optimization grouping temperature was 40-110-500 °C. The optimum mesoporous carbon sample had the highest BET specific surface area (474 m(2)/g), the largest pore volume (0.46 cm(3)/g), and with reasonable uniform pore size distribution. The adsorption evaluation also shows the adsorption capacity is strongly correlated with the pore structure of mesoporous carbon, the optimized mesoporous carbon sample displayed the largest adsorption capacity (350 mg/g) at an initial concentration of 20.0 mg/L of dichloroacetic acid. The study results indicate optimization of thermal reaction parameters is an effective approach for synthesis of ordered mesoporous carbons.

Ordered mesoporous NiO with thin pore walls and its enhanced sensing performance for formaldehyde

A class of formaldehyde (HCHO) gas sensors with a high response were developed based on ordered mesoporous NiO, which were synthesized via the nanocasting route by directly using mesoporous silica as the hard template. A series of mesoporous NiO with different textural parameters such as specific surface area, pore size, pore wall thickness were achieved by selecting mesoporous silica with different pore sizes as templates. The gas sensing properties for formaldehyde (HCHO) of the NiO specimens were examined. The results show that this mesoporous NiO possesses a much higher response to HCHO even at low concentration levels than the bulk NiO, and a larger specific surface area and pore size as well as thinner pore walls would be beneficial for enhancing the sensing properties of NiO.

Ultrathin nanosheets constructed CoMoO4porous flowers with high activity for electrocatalytic oxygen evolution

Hierarchical CoMoO₄micro-flowers assembled from ultrathin nanosheets exhibit substantially higher electrocatalytic activity and stability than the IrO₂benchmark towards oxygen evolution.

Laccase biosensor based on phytic acid modification of nanostructured SiO₂ surface for sensitive detection of dopamine

In this work, three kinds of nanostructured silica-phytic acid (SiO2-PA) materials with diverse morphologies including spherical SiO2-PA (s-SiO2-PA), rod-like (r-SiO2-PA), and helical SiO2-PA (h-SiO2-PA) were prepared with the help of electrostatic interaction. The SiO2-PA nanomaterials with different morphologies were characterized by using transmission electron microscopy (TEM), Fourier transform infrared (FTIR), electrochemical impedance spectroscopy (EIS), and circular dichroism spectrum (CD). Diverse morphologies of SiO2-PA were used as electrode decorated materials to achieve a high efficiency for electrochemical dopamine (DA) detection. The laccase biosensors were fabricated by immobilizing different morphologies of SiO2-PA nanomaterials and laccase onto the glassy carbon electrode (GCE) surface, successively. Then the electrochemical responses of the different morphologies of nanostructured SiO2-PA nanomaterials to laccase were discussed. Results indicated that compared to laccase/s-SiO2-PA and laccase/r-SiO2-PA, the laccase/h-SiO2-PA-modified electrode showed the best electrochemical performances.

Template-free synthesis of mesoporous polymers

Mesoporous polyacrylamides with tunable porosities were synthesized in 1-alkyl-3-methylimidazolium tetrafluoroborates ([C_nmim][BF₄], n = 4, 6, 8, 10).

Spherical V-MCM-48: the synthesis, characterization and catalytic performance in styrene oxidation

High-quality spherical V-MCM-48 catalysts were successfully synthesized and showed higher catalytic activity for the selective oxidation of styrene to benzaldehyde.

Fabricating a sustained releaser of heparin using SBA-15 mesoporous silica

The sustained release of heparin in sufficient amounts and over long time is a challenge to drive the development of functional materials. In this paper SBA-15 mesoporous silica is selected in the search for a favorable morphology and optimized surface state for the sustained release of heparin. In situ carbonization of the template in the as-synthesized sample enables SBA-15 to possess narrowed channels with rougher surfaces, while modification with (aminopropyl)triethoxysilane (APTES) through a one-pot synthesis offers SBA-15 with positive charges to attract heparin through electro-static interactions. The structure of modified SBA-15 samples is assessed with XRD (powder X-ray diffraction analysis), nitrogen adsorption-desorption and electron microscopy techniques, and their performance is evaluated in adsorption and release of heparin. These modifications improve the heparin adsorption in SBA-15 and thus promote its sustained release, prolonging the release-equilibrium time up to 60 days. Among them, the SBA-15 sample modified with APTES can trap three times as much heparin as the parent SBA-15, and the release ratio is elevated to 80% (that of SBA-15 is 38%), realizing the best performance of controlling heparin release to date.

Preparation of titanium-grafted magnetic mesoporous silica for the enrichment of endogenous serum phosphopeptides

As one of the most important post-translational modifications, reversible phosphorylation of protein plays crucial roles in a large number of biological processes. Moreover, endogenous phosphopeptides are also associated with certain human diseases. An efficient enrichment and separation method is the premise for successful identification and quantification of phosphopeptides. In this work, titanium grafted magnetic mesoporous silica (Fe3O4@Ti-mSiO2) was developed and applied for the enrichment of endogenous phosphopeptides. Fe3O4@Ti-mSiO2 particles were prepared by grafting titanocene dichloride on the inner walls of magnetic mesoporous silica and then being calcined to remove cyclopentadienyl ligand. The physicochemical properties of the prepared materials were characterized by energy dispersive X-ray spectroscopy (EDX), nitrogen adsorption-desorption analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). For selective enrichment of phosphopeptides, the prepared Fe3O4@Ti-mSiO2 particles were applied for tryptic digests of β-casein, mixtures of β-casein and bovine serum albumin (BSA), and low-fat milk. Finally, Fe3O4@Ti-mSiO2 was successfully applied for the enrichment of endogenous phosphopeptides from human serum.

Reactive template-induced self-assembly to ordered mesoporous polymeric and carbonaceous materials

As an important method for preparing ordered mesoporous polymeric and carbonaceous materials, the organic template directed self-assembly is facing challenges because of the weak noncovalent interactions between the organic templates and the building blocks. Herein we develop a novel reactive template-induced self-assembly procedure for fabrication of ordered mesoporous polymer and carbon materials. In our approach, the aldehyde end-group of reactive F127 template can react with the resol building block to in-situ form a stable covalent bond during the self-assembly process. This is essential for an enhanced interaction between the resol and the template, thus leading to the formation of an ordered body-centered cubic mesostructure. We also show that the ordered mesoporous carbon product exhibits superior capacitive performance, presenting an attractive potential candidate for high performance supercapacitor electrodes.

Sustained release of heparin on enlarged-pore and functionalized MCM-41

Mesoporous silica MCM-41 and SBA-15 were chosen to study the adsorption and release of bulky biomolecule heparin, in order to develop new heparin controlled delivery system and expand the application of mesoporous materials in life science. To explore how the structure of support such as pore size and surface state affects the accommodation and release of heparin, we used decane as swelling agent to enlarge pores of MCM-41, introduced amino groups for improving the biocompatibility of support, and controllably retained templates in the as-synthesized sample. The influence of modification on the structure of samples was investigated by XRD and N(2) adsorption-desorption, whereas their performance of adsorbing and releasing heparin was assessed with that of toluidine blue method. Both enlarged pore and organic modification significantly promoted the adsorption and prolonged the release of heparin in MCM-41, and the release was characterized with a three-stage release model. The mechanism of heparin release from mesoporous material was studied by fitting the release profiles to the theoretical equation. As expected, some mesoporous composites could release heparin in the long term with tuned dosage.

Small-caliber vascular prosthesis prototype based on controlled release of heparin from mesochannels and its enhanced biocompatibility

A novel small-caliber vascular prosthesis prototype is proposed on the basis of a new heparin release system, that is, the controlled delivery of heparin from mesochannels. Fabrication of mesochannels on artificial biomaterials is successfully achieved through epitaxial growth of mesoporous silica nanoparticles on expanded polytetrafluoroethylene grafts, and thus heparin can be immobilized through a space limitation effect, thereby avoiding the loss of bioactivity and enabling long-lasting release. The adsorption and release of heparin are controlled by adjusting the adsorbate-adsorbent interaction through tailoring the mesostructure. Owing to the continuous and sustained release of heparin, the performances of artificial vessels are greatly improved, thus paving a new way to prepare functional blood-contacting biomaterials with high biocompatibility.

Rational design of single-site heterogeneous catalysts: towards high chemo-, regio- and stereoselectivity

The main methods for the design and preparation of single-site heterogeneous catalysts on inorganic oxide supports are described and reviewed. Catalytically active metal sites can be either introduced into the framework of porous materials via direct synthesis or added to a pre-existing support by post-synthesis techniques. Particular attention is paid to selected examples where the geometry, the nature and the chemical surroundings of the active single site is a key factor to obtain catalytic systems with enhanced chemo-, regio- and stereoselectivity. The ever-increasing capabilities of ‘nanoarchitecture’ at molecular level enable chemists to build ideal catalysts for the sustainable transformation of bulky and high added-value molecules.

Nanotexture Optimization by Oxygen Plasma of Mesoporous Silica Thin Film for Enrichment of Low Molecular Weight Peptides Captured from Human Serum

This study investigated the optimization of mesoporous silica thin films by nanotexturing using oxygen plasma versus thermal oxidation. Calcination in oxygen plasma provides superior control over pore formation with regard to the pore surface and higher fidelity to the structure of the polymer template. The resulting porous film offers an ideal substrate for the selective partitioning of peptides from complex mixtures. The improved chemico-physical characteristics of porous thin films (pore size distribution, nanostructure, surface properties and pore connectivity) were systematically characterized with XRD, Ellipsometry, FTIR, TEM and N(2) adsorption/desorption. The enrichment of low molecular weight proteins captured from human serum on mesoporous silica thin films fabricated by both methodologies were investigated by comparison of their MALDI-TOF MS profiles. This novel on-chip fractionation technology offers advantages in recovering the low molecular weight peptides from human serum, which has been recognized as an informative resource for early diagnosis of cancer and other diseases.