Silica Hybrid Materials Research Articles

Tuneable mesoporous silica material for hydrogen storage application via nano-confined clathrate hydrate construction

Safe storage and utilisation of hydrogen is an ongoing area of research, showing potential to enable hydrogen becoming an effective fuel, substituting current carbon-based sources. Hydrogen storage is associated with a high energy cost due to its low density and boiling point, which drives a high price. Clathrates (gas hydrates) are water-based (ice-like) structures incorporating small non-polar compounds such as H2 in cages formed by hydrogen bonded water molecules. Since only water is required to construct the cages, clathrates have been identified as a potential solution for safe storage of hydrogen. In bulk, pure hydrogen clathrate (H2O-H2) only forms in harsh conditions, but confined in nanospaces the properties of water are altered and hydrogen storage at mild pressure and temperature could become possible. Here, specifically a hydrophobic mesoporous silica is proposed as a host material, providing a suitable nano-confinement for ice-like clathrate hydrate. The hybrid silica material shows an important decrease of the pressure required for clathrate formation (approx. 20%) compared to the pure H2O-H2 system. In-situ inelastic neutron scattering (INS) and neutron diffraction (ND) provided unique insights into the interaction of hydrogen with the complex surface of the hybrid material and demonstrated the stability of nano-confined hydrogen clathrate hydrate.

High-Performance Flexible Hybrid Silica Membranes with an Ultrasonic Atomization-Assisted Spray-Coated Active Layer on Polymer for Isopropanol Dehydration.

Organic-inorganic hybrid silica materials, incorporating an organic group bridging two silicon atoms, have demonstrated great potential in creating membranes with excellent permselectivity. Yet, the large-scale production of polymer-supported flexible hybrid silica membranes has remained a significant challenge. In this study, we present an easy and scalable approach for fabricating these membranes. By employing a sol-gel ultrasonic spray process with a single-pass method, we deposited a thin and uniform hybrid active layer onto a porous polymer substrate. We first optimized the deposition conditions, including substrate temperature, the binary solvent ratio of the silica sol, and various ultrasonic spray parameters. The resulting flexible hybrid silica membranes exhibited exceptional dehydration performance for isopropanol (IPA)/water solutions (IPA: 90 wt%) in the pervaporation process, achieving a water flux of 0.6 kg/(m2 h) and a separation factor of around 1300. This work demonstrates that the single-pass ultrasonic spray method is an effective strategy for the large-scale production of polymer-supported flexible hybrid silica membranes.

Characterization of antibody surface properties and selection of a diverse subset for development of a generic size-exclusion chromatography method

Aggregates are an important quality attribute for biotherapeutics because they can affect the safety and efficacy of the drug and they are therefore routinely monitored, mainly with size-exclusion chromatography (SEC). However, there is often a need to tailor a SEC method to a specific molecule. This study describes the development of a generic SEC method tested on 138 antibodies with the variable domains taken from clinical stage antibodies. We report on the discovery of a subset of 12 antibodies that represents the full range of physiochemical properties found in the 138 antibodies. This subset is shown to be an efficient and reliable test set when developing chromatographic methods for antibodies. An understanding of the nature of the analyte-stationary phase interactions was gained when using this set with its wide range of physiochemical properties. Highly hydrophobic antibodies interact strongly with some modern silica hybrid materials causing the elution time to increase significantly, while a hydrophilically modified hybrid surface showed highly reduced interactions for the hydrophobic antibodies. Highly hydrophilic antibodies, on the other hand, exhibited asymmetric peaks to a certain extent on all stationary phases, while the elution time was not affected. The developed SEC method was shown to have satisfactory performance in terms of linearity, repeatability, range, and accuracy and exhibit very narrow distributions of elution time and peak symmetry when testing the 138 antibodies indicating its generic performance.

Hybrid mesoporous silica materials templated with surfactant polyion complex (SPIC) micelles for pH-triggered drug release

New Surfactant PolyIon Complex (SPIC) micelles were assembled by electrostatic complexation of an antibacterial cationic surfactant, cetylpyridinium chloride (CPC), and a double hydrophilic block copolymer (DHBC) containing a neutral comb block of poly(oligo(ethylene glycol)) methyl ether acrylate (PEOGA) and a weak polyacid block of poly(acrylic acid) (PAA). The corresponding SPIC micelles, with a CPC/PAA core and a PEOGA corona, were successfully used as structure directing and functionalizing agents in a soft and sustainable sol-gel strategy, yielding hybrid mesoporous silica (MS) materials with a monomodal pore size distribution centred at 2.8 nm. The influence of synthesis parameters, including the pH, concentrations and ratios of components, was systematically investigated. The obtained hybrid MS materials were intrinsically functional, with PEOGA blocks anchored in silica walls via H-bonding, while weak polyacid blocks, complexed with CPC, were confined within the mesopores. The response of the materials to pH changes (pH 7.4, 4.2 and 3) indicated remarkable stability of the anchored DHBC, while CPC was selectively released under the acidic conditions typical of orodental biofilm microenvironments. This result is noteworthy, since the release of encapsulated amphiphilic drugs into water is less favorable than that of hydrophilic drugs. Owing to the control of their pore and functionality properties, ordered hybrid silica materials templated and functionalized with SPIC systems will be materials of choice for developing pH-responsive biomedical devices using wet processing techniques.

Synthesis of Organoalkoxysilanes: Versatile Organic–Inorganic Building Blocks

Organic–inorganic building blocks are an important class of hybrid materials due to the synergistic versatility of organic compounds with the robust properties of inorganic materials. Currently, the growing interest in silica hybrid materials to modify the physical and chemical properties of the silica network has led to an increasing interest in organoalkoxysilanes. A general formula of R-[Si-(OR’)3]n, with OR’ as a hydrolysable alkoxy group and R acting as the organic functional group (n ≥ 1), has led to precursors for many molecules. By introducing adequate organic moieties (R), organoalkoxysilanes effectively engage in surface and matrix modification of silica-based materials with smart-responsive units, coupling agents, targeting moieties, bioactive moieties etc., opening promising applications, specifically biomedical ones. Several synthetic procedures have been established to introduce the alkoxysilane moieties, including hydrosilylation, coupling reactions, and addition reactions to isocyanates. Herein, we review synthetic routes to organoalkoxysilanes and the relationship between structural features to design appropriate organoalkoxysilanes for specific applications.

Influence of Perfluorooctanoic Acid on Structural, Morphological, and Optical Properties of Hybrid Silica Coatings on Glass Substrates

In recent years, various coatings based on fluorinated materials, used in a commercial application, have been created through many preparation routes. However, the techniques utilized to realize these coatings required either expensive and complex equipment, imply multiple manufacturing steps, or are time- or cost-consuming. In this paper, the major target was to develop fluorinated hybrid coatings presenting sustainable hydrophobicity and good transparency simultaneously. The sol–gel method was proposed to obtain these fluorinated hybrid coatings because it does not require expensive equipment, or the existence of stabilizing agents that reduce the storage period, it consumes less energy, and it is easy to implement. The influence of perfluorooctanoic acid, utilized in the sol–gel processing of hybrid silica materials, on the structural, morphological, and optical properties of coatings deposited on glass substrates, was evaluated. Different silane precursors (tetraethyl orthosilicate (TEOS), triethoxymethylsilane (MTES), and trimethoxyhexadecylsilane (HDTMES)) were utilized to synthesize hybrid silica materials. The properties of the obtained materials were characterized by FTIR, UV–Vis, TEM, TGA, AFM, Ellipsometry, and Contact Angle analyses. FTIR spectroscopy shows the formation of a silica network tailored with organofunctional and fluoroalkyl groups. The fluorinated silica coatings presented smooth surfaces and good transparency, with a transmittance of ~90% in the visible range. It was found that the fluorinated silica materials improved the coating’s hydrophobicity (~110° in contact angle with water). These fluorinated silica materials can create multifunctional structures with antireflective and hydrophobic coatings for possible optical devices.

The Synthesis of Triamine Group Modified Silica Hybrid Material Coated on Muara Kencan Iron Sand for Hg (II) Adsorption

Hg metal was toxic and harmful to the environment because it does not biodegradation, can accumulate in living things, and pollute waters. One method that can be used was adsorption by inorganic-organic hybrid materials. This study aims to synthesize a triamine group modified silica hybrid material coated on iron sand or Magnetic Materials@Silica@Triamine (MM@SiO2@TA) to adsorb Hg(II) metal ions. The study began with the preparation of the iron sand of Muara Kencan Beach using magnets, washing using a solution of 1 M HCl and 0.5 M HF, and coating the material using sodium silica (SiO 25.5-28.5%) modified by a 99% triamine group with co-precipitation. The XRF characterization results showed that the magnetic material of the iron sand of Muara Kencan Beach has an iron oxide (magnetite) content of 73.31%. The iron oxide content increased after washing with HCl solution to 79.12% and HF solution to 81.81%. The results of FTIR, XRD, and TEM characterization showed that the MM@SiO2@TA was successfully synthesized with a size of 63.43 nm. The MM@SiO2@TA was tested to adsorb metal ion Hg(II) at a concentration of 100 ppm, pH 6, and a contact time of 1 hour. The AAS results showed that MM@SiO2@TA could adsorb metal ions Hg(II) as much as 60.82 ppm or 60.82%.

Hybrid silica material as a mixed-mode sorbent for solid-phase extraction of hydrophobic and hydrophilic illegal additives from food samples

In the current study, a novel kind of mixed-mode hydrophobic/hydrophilic hybrid silica material has been developed for the solid-phase extraction of hydrophobic and hydrophilic illegal additives from food samples. A hydrophobic hybrid silica material was first prepared by the sol-gel method with tetraethoxysilane, 3-aminopropyltriethoxysilane, and dimethyloctadecyl-[3-(trimethoxysilyl)propyl] ammonium chloride (DTSACl) as precursors. Subsequently, the hydrophobic hybrid silica material was activated by glutaraldehyde, followed by the covalent immobilization of polyethyleneimine (PEI). PEI and the octadecyl group of DTSACl produced the hydrophilic/hydrophobic features of the hybrid silica material. The developed material was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, solid-state nuclear magnetic resonance, zeta potential analyzer, and laser diffraction particle size analyzer, then applied as a hydrophobic and hydrophilic sorbent for the solid-phase extraction (SPE) of benzodiazepines from ginseng amino acid oral liquid as well as melamine and cyromazine from powdered milk, followed by RPLC/HILIC-MS/MS analysis. The composition and volumes for SPE loading and elution solutions were optimized in detail. Coupled with RPLC/HILIC-MS/MS, the proposed method provided satisfactory linearity in the range from 0.9–3.2 µg kg−1 to 100–250 µg kg−1 with the coefficients of determination higher than 0.99. The limits of detection ranged from 0.3 to 1.0 µg kg−1, and the recoveries ranged from 81.1% to 109.0% with the relative standard deviations less than 8.5% (n = 3). This report offers a new mixed-mode hydrophobic/hydrophilic hybrid silica material to extract trace hydrophobic and hydrophilic additives from complex samples.

Preparation and chiral resolution properties of bridged bis(cyclodextrin)s hybrid spheres for high performance liquid chromatography.

Selenium-bridged bis(β-cyclodextrin)s organic-inorganic hybrid silica material with regular spherical shape as new type of chiral stationary phase was directly synthesized under the one-pot hydrothermal synthesis method, and the chiral stationary phase was further characterized by infrared spectroscopy, scanning electron microscopy, thermogravimetry, and elemental analysis. The results of chiral separation showed that eight chiral compounds including various types of chiral alcohols and flavanone were successfully separated in the reversed-phase separation mode by high performance liquid chromatography, which showed the better chiral resolution effect than that on the C2 position of single β-cyclodextrin. The mechanism of chiral separation was likely due to multiple interactions such as inclusion, hydrogen bonding, electrostatic interaction, dipole-dipole interaction, and the synergistic effect of two cyclodextrins during the chiral resolution process. The synergy of the two cyclodextrins has great potential for development in chiral resolution.

The synthetic approaches, properties, classification and heavy metal adsorption applications of periodic mesoporous organosilicas

Periodic Mesoporous Organosilica (nano)materials (bulk PMO and PMO NPs), one of the most advanced organic–inorganic hybrid silica materials, are increasingly studied in recent years. Compared with other hybrid silica materials, PMOs have some unique advantages, such as robust porous channels, organic–inorganic framework, tunable pore size arrangement, biocompatibility, high organic contents and easy functionalization. They have attracted growing interest of study in some newly emerged fields including biology, biomedicine and catalysis. On the other hand, heavy metals in wastewaters severely pollute the environment and thus do harm to the aquatic ecosystems as well as human health, which is considered an urgent issue to be solved in modern society. It is very meaningful to use PMO materials to realize the effective detection of heavy metal ions and to solve their recovery. Herein, this review focuses on the synthetic strategies of PMO adsorbents as well as their performance and mechanism of adsorption for the heavy metals.

Lanthanide–based luminescent hybrid silica materials prepared by sol-gel methodologies: a review

Lanthanide–based luminescent hybrid silica materials prepared by sol-gel methodologies: a review

Selectivity enhancement for the separation of shape‐constrained isomers by particle size‐derived molecular ordering and density in reversed‐phase liquid chromatography

AbstractThe purpose of this study is to describe the enhancement of molecular‐shape selectivity and grafted polymer characteristics by altering the particle size, pore size, and polymer chains of polymer‐silica hybrid materials used in reversed‐phase liquid chromatography. The poly(octadecyl acrylate‐alt‐N‐octadecylmaleimide)‐grafted silica hybrid materials were prepared with 3 and 5 μm particle size silica, respectively. The alternating copolymerisations were conducted with 3‐mercaptopropyltrimethoxysilane‐modified silica via surface‐initiated radical chain transfer reactions. The polymer‐silica hybrid materials were characterised by elemental analyses, diffuse reflectance FTIR spectroscopy, solid‐state 13C and 29Si cross‐polarisation–magic‐angle spinning and suspended‐state 1H NMR spectroscopy. The NMR spectroscopy results revealed that the alkyl chains of 3 μm particle size phase are more ordered than those of 5 μm particle size phase at lower temperatures and vice versa at higher temperatures. After detailed characterisation, the hybrid materials were packed into a stainless‐steel column, and their chromatographic performance with polycyclic aromatic hydrocarbons was compared. Regardless of the grafting‐density, ordering of the alkyl chains, and column temperature, differences in molecular‐planarity selectivity molecular‐linearity were observed. Aspects of molecular‐shape selectivity were also evaluated using the standard reference material for priority pollutant polycyclic aromatic hydrocarbons.

Triazolyl Conjugated (Oligo)Phenothiazines Building Blocks for Hybrid Materials-Synthesis and Electronic Properties.

The Cu-catalyzed alkyne-azide 1,3-dipolar cycloaddition variant provides a highly efficient entry to conjugated triazolyl-substituted (oligo)phenothiazine organosilicon derivatives with luminescence and reversible redox characteristics. Furthermore, by in-situ co-condensation synthesis several representative mesoporous MCM-41 type silica hybrid materials with embedded (oligo)phenothiazines are prepared and characterized with respect to their structural and electronic properties. The hybrid materials also can be oxidized to covalently bound embedded radical cations, which are identified by their UV/Vis absorption signature and EPR signals.

Preparation and Characterization of New Sol-Gel Hybrid Inulin-TEOS Adsorbent.

A new biopolymer–silica hybrid material consisting of inulin and tetraethoxysilane (TEOS) for use as an adsorbent was successfully synthesized via the sol–gel method in acidic conditions. The hydrolysis and condensation processes were attained in water/ethanol solution. Three molar ratios of inulin:TEOS (1:1, 1:2, and 2:1) were prepared and dried at various temperatures (50, 60, and 70 °C). The optimized molar ratio of 2:1 with a drying temperature of 70 °C was found to obtain the best morphology and characteristics for absorbent properties. Fourier transform infrared spectroscopy (FTIR) analysis showed a strong interaction between inulin and TEOS, which was also observed using energy dispersive X-ray spectroscopy (EDX). Field emission scanning electron microscopy (FESEM) images revealed the presence of nanoparticles on the rough surface of the hybrid sol–gel. X-ray diffractometer (XRD) analysis showed the amorphous state of the silica network where the inulin existed as an anhydrous crystalline phase. Brunauer–Emmet–Teller (BET) analysis confirmed that the composite was mesoporous, with 17.69 m2/g surface area and 34.06 Å pore size. According to thermogravimetric analysis (TGA) results, the hybrid inulin-TEOS adsorbent was thermally stable under a temperature of 200 °C.

Hybrid Silica Materials Applied for Fuchsine B Color Removal from Wastewaters.

Hybrid materials, with applications in fuchsine B color removal from wastewaters, were obtained by in situ incorporation of platinum nanoparticles and/or Pt-porphyrin derivatives into silica matrices. The inorganic silica matrices were synthesized by the sol-gel method, conducted in acid-base catalysis in two steps and further characterized by Nitrogen porosimetry, Small Angle Neutron Scattering (SANS), Scanning electron microscopy, Atomic force microscopy and UV-vis spectroscopy. All of the investigated silica hybrid materials were 100% efficient in removing fuchsine B if concentrations were lower than 1 × 10−5 M. For higher concentrations, the silica matrices containing platinum, either modified with Pt-metalloporphyrin or with platinum nanoparticles (PtNPs), are the most efficient materials for fuchsine B adsorption from wastewaters. It can be concluded that the presence of the platinum facilitates chemical interactions with the dye molecule through its amine functional groups. An excellent performance of 197.28 mg fuchsine B/g adsorbent material, in good agreement with the best values mentioned in literature, was achieved by PtNPs-silica material, capable of removing the dye from solutions of 5 × 10−4 M, even in still conditions.

Enhanced adsorption and separation of Re(VII) using organic-inorganic hybrid silica adsorbent

We prepared a series of amino-functionalized organic-inorganic hybrid silica materials by post-modification (SBA-15-N) and one-pot (SS-0.5h-N) methods with different molar rate of APTES/SS (0.1:1, 0.2:1, 0.3:1, 0.5:1), and then took salicylaldehyde and epichlorohydrin as bridges, modified diisobutylamine on the hybrid silica to obtain the adsorbents containing tertiary amine groups. It was found that the combined use of organic and inorganic precursors (one-pot) destroys the ordered mesoporous structure, but the organic units distributed more homogeneously which conducive to the progress of adsorption. For the samples prepared by one-pot, the adsorption capacity increased dramatically when the molar rate of APTES/SS is 0.3:1 (SS-0.5h-0.3N-DIBA, 221.37 mg g−1), and the adsorption behavior obeys the Langmuir model. The adsorption mechanism could be electrostatic attraction and chelation effect between ReO4− and nitrogenous group which demonstrated by FT-IR and XPS. In addition, the SS-0.5h-0.3N-DIBA could effectively separate Re(VII) from coexisting metal ions (Cu(II), Zn(II), Mn(II)) at pH < 2. The adsorption capacity for Re(VII) kept stable after four cycles and 5.0% NH3·H2O as an eluent is environment friendly. Therefore, this study provided a new adsorbent based on sodium silicate for the separation of Re(VII) from mixed solution with the help of SS-0.5h-0.3N-DIBA.

Hybrid material by anchoring a ruthenium(ii) imine complex to SiO2: preparation, characterization and DFT studies.

Ruthenium–silica hybrid material (RuCl2(PR3)2-2-PyCH-AMPTSi/SiO2) was prepared and characterized by various spectroscopic techniques. A deconvolution procedure was applied to the spectroscopic data to deconstruct the overlapped bands. A density functional theoretical approach was applied to get insights into the electronic structure of the ruthenium coordination site and the functional RI-PBE-D3/Def2TZVP basis set was used for the optimization. Relativistic effects were considered using the zero-order regular approximation (ZORA). The anchoring process, evinced for each step of the synthesis of the hybrid material, was tracked by FT-IR analyses. The transitions observed in the FT-IR spectra were verified by DFT analyses, which agree with the experimental data. In the DRS-UV-Vis spectra, three main bands were detected by the deconvolution procedure that correspond to the charge transfer transitions, with the main contributions from ruthenium-chlorine and imine–pyridine fragments. TD-DFT results reveal that ruthenium-chlorine antibonding orbitals act as main charge donors, while pyridine–imine is the main charge acceptor.

Tailored structuring of functionalized silsesquioxanes in a one-step approach

The silica hybrid materials prepared from tailor-made precursors with different headgroups in several experimental conditions (acid or base catalysis in water or THF) were studied in order to identify the structure directing mechanisms.

Sensing application of novel nanocomposite based on lanthanide functionalized nanoporous material and polymer matrix

Recently, lanthanide hybrid material has aroused great interest because of its wide range application in lighting material, bio-imaging, chemical/biological sensing and so on. Here, a binary lanthanide terbium/mesoporous silica hybrid material (Tb@MCM-41), and a ternary lanthanide terbium/mesoporous silica/polyurethane hybrid material (Tb@MCM-41@PU) are reported. Typically, the lanthanide Tb3+ ions were connected onto the surface of mesoporous MCM-41 via the molecular bridge built by the synergy of silane coupling agent (APTEOS) and chelating reagent (DTPA), and then the resulted Tb@MCM-41 was encapsulated into a commercial polymer matrix (PU) to form Tb@MCM-41@PU composite film. The sensing experiments conducted in solution had proven that Tb@MCM-41 has good selective sensing ability to the dopamine molecular. And further experiments also indicated the Tb@MCM-41@PU composite film can be used as a very convenient sensor tool towards dopamine.

PEGylated perylene bisimides: Chromonic building blocks for the aqueous synthesis of nanostructured silica materials

Perylene dyes have applications in many fields. Herewith, we report on the synthesis and properties of a series of PEGylated perylene bisimides with varying PEG chain lengths. Such molecules are formed by a hydrophobic perylene core functionalized at the imide positions with hydrophilic non-ionic functional groups, which impart solubility and capacity to self-assemble in water. The diluted solutions of the synthesized molecules show interesting optical and fluorescent properties that depend on solvent and concentration; they also show surface activity and a lower critical solution temperature. Moreover, at high concentrations, the molecules produce lyotropic chromonic liquid crystals with nematic and hexagonal structures, formed by aligned molecular stacks. Such mesostructures were successfully exploited for the preparation of hybrid silica materials with ordered perylene nanostripes that generate aligned nanopores (of ca. 1.4 nm) upon calcination. It was found that the distance between perylene nanostripes and hence the pore wall thickness can be finely tuned by changing the length of the PEG chain.