Silica Pore Walls Research Articles

Synthesis of Mesoporous Silica Adsorbent Modified with Mercapto–Amine Groups for Selective Adsorption of Cu2+ Ion from Aqueous Solution

In a sol–gel co-condensation, a mesoporous silica hybrid integrated with (3-mercaptopropyl)trimethoxysilane (TMPSH) was prepared and then reacted with allylamine via a post-surface functionalization approach. Approximately 15 mol% of TMSPSH was introduced into the mesoporous silica pore walls along with tetraethyl orthosilicate. The mercapto ligands in the prepared mesoporous silica pore walls were then reacted with allylamine (AM) to form the mercapto–amine-modified mesoporous silica adsorbent (MSH@MA). The MSH@MA NPs demonstrate highly selective adsorption of copper (Cu2+) ions (~190 mg/g) with a fast equilibrium adsorption time (30 min). The prepared adsorbent shows at least a five times more efficient recyclable stability. The MSH@MA NPs adsorbent is useful for selective adsorption of Cu2+ ions.

The Nature of Interface Interactions Leading to High Ionic Conductivity in LiBH4/SiO2 Nanocomposites.

Complex metal hydride/oxide nanocomposites are a promising class of solid-state electrolytes. They exhibit high ionic conductivities due to an interaction of the metal hydride with the surface of the oxide. The exact nature of this interaction and composition of the hydride/oxide interface is not yet known. Using 1H, 7Li, 11B, and 29Si NMR spectroscopy and lithium borohydride confined in nanoporous silica as a model system, we now elucidate the chemistry and dynamics occurring at the interface between the scaffold and the complex metal hydride. We observed that the structure of the oxide scaffold has a significant effect on the ionic conductivity. A previously unknown silicon site was observed in the nanocomposites and correlated to the LiBH4 at the interface with silica. We provide a model for the origin of this silicon site which reveals that siloxane bonds are broken and highly dynamic silicon–hydride–borohydride and silicon–oxide–lithium bonds are formed at the interface between LiBH4 and silica. Additionally, we discovered a strong correlation between the thickness of the silica pore walls and the fraction of the LiBH4 that displays fast dynamics. Our findings provide insights on the role of the local scaffold structure and the chemistry of the interaction at the interface between complex metal hydrides and oxide hosts. These findings are relevant for other complex hydride/metal oxide systems where interface effects leads to a high ionic conductivity.

Dihydropyrano quinoline derivatives functionalized nanoporous silica as novel fluorescence sensor for Fe3+ in aqueous solutions(aq)

A novel nanoporous silica-based fluorescence sensor with high selectivity and sensitivity was successfully prepared via grafting of 3-isocyanatopropyltriethoxysilane and dihydropyrano [3, 2-c] quinoline derivatives (DPQ) onto the pore walls of mesoporous silica. The attachment of fluorophore groups onto the surface of the SBA-15 was approved via TGA and FT‐IR spectroscopy. TGA analysis indicates a large weight loss about 49%, which is attributed to the binding of a large number of organic groups on the pores surface, which functional groups appeared in the FT-IR spectra. Structural characterization techniques have proved the type IV for N2 adsorption-desorption isotherm, which revealed the preservation of the mesoporous structure. Also, low-angle XRD, FESEM and TEM analyses demonstrate the formation of ordered and well-defined 2D hexagonal mesoporous structure (space group p6mm). Whereas, Fe3+ ions caused discernible fluorescence quenching of the fluorescence sensor, the other cations used did not significantly changed fluorescence emission of SBA-Si-DPQ. The fluorescence quenching of the sensor is attributed to the paramagnetic properties of Fe3+ ions that appear by complex formation between the urea group of the probe and Fe3+ ions. It is noteworthy that, the excitation at 310 nm caused an emission with a maximum at 478 nm wavelength. By the increasing concentration of the analytes, the emission intensity was decreased dramatically and good linearity observed between analytes concentrations and the fluorescence intensity quenching of the sensor. The measured detection limits for Fe3+ ions was 2.0 × 10−6 M.

Synthesis of bifunctional groups-integrated mesoporous silica hybrid adsorbent for simultaneous removal of Hg2+ and Cu2+ ions from aqueous solution

A mesoporous organosilica hybrid integrated with disulfide and amine groups was synthesized in a sol-gel co-condensation method using Pluronic P123 as structural directing surfactant. In the initial silane mixture, the organic functional groups content of disulfide and amine groups along with tetraethyl orthosilicate incorporated into the pore walls of mesoporous silica is approximately 30 mol/g (BDSTES: AAPTES is 15:15 mol/g). The surface area, pore volume and pore size of the prepared disulfide bridged and amine groups integrated mesoporous silica hybrid adsorbent (MSHA@SS-NH2) materials are approximately 462 m2/g, 0.58 cm3/g, and 2.6 nm, respectively. The MSHA@SS-NH2 adsorbent materials demonstrated that adsorption equilibrium could be achieved in 30 min and the adsorbed amount of Hg2+ and Cu2+ ions calculated to be about 166 mg/g and 153 mg/g, respectively, with the ∼ 90% of Hg2+ ions and ∼ 84% of Cu2+ ions removal capacity from the mixture of initial metal ions solutions (100 mg/L). By washing with 0.1 M HCl solution and regenerating with aqueous ammonia (3%) solution, the MSHA@SS-NH2 adsorbent demonstrated recyclable and reusable ability up to 5 times. As a result, the MSHA@SS-NH2 material developed could be used as an effective adsorbent for the simultaneous removal of Hg2+ and Cu2+ ions from wastewater.

A heterogeneous mesoporous catalyst based on anchored copper: Schiff base complex into SBA-15 for the synthesis of benzimidazoles from orthoesters

In this article, we report the synthesis of 2-substituted benzimidazoles via condensation of 1,2-phenylenediamines and orthoesters using a heterogeneous catalyst based on anchored copper-Schiff base complex into SBA-15 (Cu/SBA-15) as a modified nanoporous material. The catalyst has been prepared via a postsynthesis grafting method and the 2D hexagonal mesoporous structures of this hybrid have been confirmed by small-angle X-ray scattering, transmission electron microscopy, N2 adsorption–desorption isotherms and Fourier transform infrared spectroscopy. Our results show that the benzimidazole heterocycles were obtained in good to excellent yields under solvent-free conditions in the presence of entitled catalyst. The mesoporous silica pore walls of the catalyst create some advantages such as high specific surface area, good to excellent yields of the benzimidazole products, non-toxicity and reusability.

Highly selective fluorescence detection of Cu2+ based on Schiff base functionalized periodic mesoporous organosilicas.

A novel copper ion sensing periodic mesoporous organosilica (SCN-PMO) was obtained by incorporating a Schiff base-based fluorescent receptor into the pore walls of mesoporous silica, which exhibited a well ordered mesoporous structure and excellent optical properties demonstrated by various characterization results. SCN-PMO possessed high selectivity and sensitivity towards Cu2+ based on its specific fluorescence response. The detection limit of SCN-PMO could be as low as 6.7 × 10-7 M. Due to protection of the silica network, SCN chromophores in PMOs exhibited higher photostability and the resulting material possessed great repeatability. Additionally, the fluorescence changes of SCN-PMO towards copper ions in vivo (zebrafish) showed that SCN-PMO has potential application as a nanoprobe in biological fields.

Preparation and Evaluation of Precipitated Silica for CO2 Removal

In gas separation and purification, adsorption using solid sorbents is very well known as an effective technology for removing acid gases. There are many applications to this technology where grafting functional groups of amines into the pore walls of silica can create a distinct adsorbent type. With this manipulation adsorbents operating conditions, regeneration, selectivity, and stability maybe controlled for a particular application such as the food industry, pharmaceuticals, textile industry, manufacturing, and shown interest in greenhouse gases mitigation. CO2 adsorption using precipitated silica supported amine is an attractive method for carbon capture technologies due to its high loading capacity, regeneration potential and low cost. H2S removal using silica has shown high loading as demonstrated by (Vaewdaow Jaiboon et al., 2014) at around 50-60wt% with an Si-TRI grafted silica [1]. Simultaneous adsorption with silica has not been extensively studied due to greater modification to the experimental setup which involves using sequential sorption and double stage bed reactors with varying feed temperatures for each species as CO2 generally takes longer to adsorb compared to H2S adding to the complexity of the dual adsorption mechanism. The purpose of this study is to synthesize precipitated silica from sodium silicate using CO2 as an acidizing agent and then impregnate polyethyleneimine (PEI) to produce CO2 adsorbent experimentally. The novel silica loading and regeneration potential will be evaluated with CO2. The adsorbent with various PEI contents from 30 to 65 wt% was prepared by a wet impregnation method. The surface area, pore volume and pore size were analysed by a nitrogen adsorption/desorption method. A scanning electron microscope was used to study the structure of the adsorbent, and a Thermogravimetric analysis (TGA) was performed using a Thermogravimetric analyser (SDT Q600). Precipitated silica having surface area of 117.9 m2/ and pore volume of 1.52 cm3/g was synthesized and used for PEI impregnation. The CO2 adsorption performance was examined using a flow Micro Reaction Calorimeter (URC) by flowing pure CO2 into analysis cell under isothermal condition. CO2 adsorption experiments will be conducted at different adsorption and regeneration temperatures to determine optimum operation temperature for CO2 capture. Preliminary results show an increase in mass of CO2 per gram of adsorbent from 89.8 to 180.04 mg/g as PEI impregnated contents increasing from 30 -60wt%, respectively. Further tests have been carried at various temperatures ranging from 60-90°C and a general increase in loading capacity was observed. When the sample was regenerated at 60°C the adsorption capacity decreased slightly for lower PEI wt% but increased higher than the first trial for higher PEI wt%. in general, with PEI 65wt% the loading of the amine dropped significantly. The outcome of this research will help strengthen the understanding of precipitated silica subjected to CO2 loading and the translation of the experimental model to a simulation model used to mimic a full-scale adsorption plant. The affinity towards CO2 will aid in the global research endeavour to study different morphologies and their optimum application space.

Thick pore wall and strong stability of mesoporous silica supported HPW materials: Highly efficient catalysts for cellulose hydrolysis reaction

Without the addition of traditional hydrochloric acid, the thick pore walls of ordered mesoporous silica-supported HPW materials were prepared by one-pot co-condensation technology with phosphotungstic acid (HPW) as the acidic medium and active center. Compare with traditional HPW supported SBA-15 materials (HPW/SBA-15) which are synthesized in hydrochloric acid solution, the characterization results show that the pore wall thickness of the prepared HPW/OMS is 1 nm thicker than the traditional materials. The heterogeneous catalytic system provides a high cellulose conversion of 94.1% with 61.2% yield from reducing sugars. Furthermore, the solid acid catalyst could be easily recovered and recycled up to five times without significant loss of activity with no leaching of species to the reaction mixture.

Biological Evaluation of Black Chokeberry Extract Free and Embedded in Two Mesoporous Silica-Type Matrices.

Black chokeberry fruits possess a wide range of biological activities, among which the most important that are frequently mentioned in the literature are their antioxidant, anti-inflammatory, anti-proliferative, and antimicrobial properties. The present paper reports, for the first time, the encapsulation of the ethanolic extract of Aronia melanocarpa L. fruits into two mesoporous silica-type matrices (i.e., pristine MCM-41 and MCM-41 silica decorated with zinc oxide nanoparticles). The aim of this work was to evaluate the antiradicalic capacity, the antimicrobial potential, and the effects on the cell viability on a cancer cell line (i.e., A375 human melanoma cell line) versus normal cells (i.e., HaCaT human keratinocytes) of black chokeberry extract loaded on silica-type matrices in comparison to that of the extract alone. The ethanolic polyphenolic extract obtained by conventional extraction was characterized by high-performance liquid chromatography with a photodiode array detector (HPLC–PDA) and spectrophotometric methods. The extract was found to contain high amounts of polyphenols and flavonoids, as well as good radical scavenging activity. The extract-loaded materials were investigated by Fourier transform infrared spectroscopy, N2 adsorption–desorption isotherms, thermal analysis, and radical scavenger activity on solid samples. The black chokeberry extract, both free and loaded onto mesoporous silica-type matrices, exhibited a significant antioxidant capacity. Antibacterial activity was recorded only for Gram-positive bacteria, with a more potent antibacterial effect being observed for the extract loaded onto the ZnO-modified MCM-41 silica-type support than for the free extract, probably due to the synergistic effect of the ZnO nanoparticles that decorate the pore walls of silica. The cellular viability test (i.e., MTT assay) showed dose- and time-dependent activity regarding the melanoma cell line. The healthy cells were less affected than the cancer cells, with all tested samples showing good cytocompatibility at doses of up to 100 µg/mL. Improved in vitro antiproliferative and antimigratory (i.e., scratch assay) potential was demonstrated through the loading of black chokeberry extract into mesoporous silica-type matrices, and the screened samples exhibited low selectivity against the tested non-tumor cell line. Based on presented results, one can conclude that mesoporous silica-type matrices are good hosts for black chokeberry extract, increasing its antioxidant, antibacterial (on the screened strains), and in vitro antitumor (on the screened cell line) properties.

Effect of Nanoconfinement of Polyphenolic Extract from Grape Pomace into Functionalized Mesoporous Silica on Its Biocompatibility and Radical Scavenging Activity.

The aim of this paper is to assess the properties of Mamaia (MM) grape pomace polyphenolic extract loaded onto pristine and functionalized MCM-41 mesoporous silica as potential ingredients for nutraceuticals or cosmetics. The chemical profile of hydroalcoholic polyphenolic extracts, prepared either by conventional extraction or microwave-assisted method, was analyzed by reverse-phase high-performance liquid chromatography with photodiode array detector (HPLC-PDA) analysis, while their radical scavenger activity (RSA) was evaluated using DPPH (2,2-diphenyl-1-picrylhydrazyl radical) and ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) assays. The extract-loaded materials were characterized by Fourier transform infrared (FTIR) spectroscopy, N2 adsorption-desorption isotherms, thermogravimetric analysis, as well as RSA (DPPH and ABTS assays). The polyphenols release profiles from pristine and functionalized (with mercaptopropyl, propyl sulfonic acid, cyanoethyl and propionic acid moieties) MCM-41-type supports were determined in phosphate buffer solution (PBS) pH 5.7. For selected materials containing embedded phytochemicals, cellular viability, and oxidative stress level on immortalized mouse embryonic fibroblast cell line (NIH3T3) were evaluated. A more acidic functional groups linked on silica pore walls determined a higher amount of phytochemicals released in PBS. The extract-loaded materials showed a good cytocompatibility on tested concentrations. The embedded extract preserved better the RSA over time than the free extract. The polyphenols-loaded MCM-41-type silica materials, especially MM@MCM-COOH material, demonstrated a good in vitro antioxidant effect on NIH3T3 cells, being potential candidates for nutraceutical or cosmetic formulations.

Behaviour of ionic liquid adsorbed on the surface of nano silica particles and in confined system of silica matrices

This paper presents studies on behaviour of a solid ionic liquid (IL); 1-butyl-2,3-dimethylimidazolium hexafluorophosphate [BMMIM][PF6] based ionogels obtained by two different techniques, first by physical confinement of IL into nano porous silica matrix and second by adsorption of IL on the outer surface of nano silica particles. The properties of samples have been investigated using various experimental techniques like N2-sorption measurements, TEM, DSC, TGA, and FTIR. It has been observed that the properties of IL have been affected more in confined geometry of silica pores as compared to the adsorption on the surface of nano silica particles. Loading of IL initially increases size and volume of pores while decrease the surface area by ~ 23 %. However, further increase in loading of IL does not produce significant change. This might be explained on basis of π-π stacking of imidazolium ring and an additional π-π stacking association between imidazolium cations. The Fourier transform infrared (FTIR) results show that stronger interaction of IL with the silica pore wall surface in confined matrix while weaker interaction due to the interfacial interaction of nano silica particles with the ions of the IL in surface adsorbed IL. The interactions and method of confinement of IL have been found to be the key parameters that determine the properties of confined and adsorbed IL.

Removing Cd(II) from Aqueous Solution by Inverse Opal Hybrid SiO2

A hybrid adsorbent with inverse opal (IO) structure was prepared for removing Cd(II) from aqueous solution. The functional polymeric chains were grafted from the pore wall of IO silica to prepare the porous hybrid material by surface-initiated atom-transfer radical polymerization. Furthermore, the amidation reaction was carried out to obtain diethylenetriamine-modified hybrid adsorbent (IO SiO2-g-PAA-DETA). Batch adsorption of removing Cd(II) onto IO SiO2-g-PAA-DETA was studied as the effect of solution pH, adsorbent doses, contact time, ionic concentration, and temperature. When the grafted amount was 73%, the maximum adsorption capacity was obtained. The optimum adsorbent dose and pH value for adsorbing Cd(II) were found to be 5[Formula: see text]g/L and 0.5[Formula: see text]g/L, respectively. The adsorption capacity was almost unaffected by Na[Formula: see text] at low concentrations. The adsorption data was depicted by the corresponding models and the results displayed that adsorbing Cd(II) on IO SiO2-g-PAA-DETA followed the Freundlich and pseudo-first-order model. In addition, after six adsorption–desorption cycles, IO adsorbent could remain above 80% of the first adsorption ability while it was washed using 0.025[Formula: see text]M EDTA.

Tailored crystalline order of nascent polyethylene from metallocene supported on confined polystyrene

Building the desirable superstructure of polyethylene is one of the important topics for developing high value-added products, which brings potential benefits for society and sustainable development. Crystalline order is the ubiquitous superstructure for enhancing mechanical properties of polymeric materials. In this work, polystyrene copolymers (c-PS) are incorporated into pores of silica through the wet-impregnation procedure of styrene and p-chloromethyl styrene followed by the in-situ free-radical copolymerization. Metallocene catalyst is further immobilized on supported silica. This incorporated c-PS is proved to be coated on the surface of silica pore walls rather than blocking the interparticle channels. The swelling behavior of c-PS inside the pores are performed by pulsed field gradient NMR (PFG-NMR) and thermoporosimetry (TPM-DSC), where a swelling behavior is shown in the toluene owing to the matched solubility parameters between the c-PS and toluene. According to the swelling behavior of c-PS confined in the pores, a compartmentalization is created hindering the formation of chain overlaps and increasing the crystallinity order of nascent polymers. As a result, the nascent polyethylene with a high crystallinity (i.e., bulk crystallinity Xc,DSC = 72.9 % and linear crystallinity Xc,WAXD = 90.5 %) is synthesized. There is a considerable activity (i.e., 3.8 × 106 g PE·(molZr·h)−1) at 70 °C. Finally, the particle morphology of the nascent polyethylene is investigated based on the swelling behavior of c-PS.

In Situ Fourier Transform Infrared Study of the Effects of Silica Mesopore Confinement on Hydration of Ionic Liquid 1-Butyl-3-methylimidazolium Chloride

The absorption of water by ionic liquid 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]) confined in silica thin films with accessible 8 nm cylindrical mesopores was investigated and compared to that of bulk ionic liquid. Transmission Fourier transform infrared spectra were collected in situ at room temperature while the relative humidity (RH) of the environment (RH of 0% to 87%) was changed. Pore confinement induces binding of imidazolium rings with the silica pore wall under dry conditions, but hydration disrupts hydrogen bonding of imidazolium with both silica and Cl–, as interpreted from peak shifts corresponding to C–H vibrations on the imidazolium ring. Molecular interactions with water are similar regardless of confinement, but [BMIM][Cl] exhibits significantly reduced water uptake at RH > 15% due to nanopore charge and structuring effects associated with confinement. Deconvolution of OH stretching bands shows that weakly coordinated water is promoted in confined [BMIM][Cl], which may affect mechanisms of solubilization and catalysis in confined ILs.

Gas Responsive Nanoswitch: Copper Oxide Composite for Highly Selective H2S Detection

AbstractA nanocomposite material based on copper(II) oxide (CuO) and its utilization as a highly selective and stable gas‐responsive electrical switch for hydrogen sulphide (H2S) detection is presented. The material can be applied as a sensitive layer for H2S monitoring, e.g., in biogas gas plants. CuO nanoparticles are embedded in a rigid, nanoporous silica (SiO2) matrix to form an electrical percolating network of low conducting CuO and, upon exposure to H2S, highly conducting copper(II) sulphide (CuS) particles. By steric hindrance due to the silica pore walls, the structure of the network is maintained even though the reversible reaction of CuO to CuS is accompanied by significant volume expansion. The conducting state of the percolating network can be controlled by a variety of parameters, such as temperature, electrode layout, and network topology of the porous silica matrix. The latter means that this new type of sensing material has a structure‐encoded detection limit for H2S, which offers new application opportunities. The fabrication process of the mesoporous CuO@SiO2composite as well as the sensor design and characteristics are described in detail. In addition, theoretical modeling of the percolation effect by Monte‐Carlo simulations yields deeper insight into the underlying percolation mechanism and the observed response characteristics.

Development of New Bexarotene-loaded Mesoporous Silica Systems for Topical Pharmaceutical Formulations

The present study reports the first time use of MCM-41 mesoporous silica as highly efficient carrier for bexarotene - an antineoplastic agent specific for cutaneous T-cell lymphoma treatment. Bexarotene is highly toxic and poor-water soluble, having low bioavailability in the conventional pharmaceutical forms. Comparative uptake of bexarotene on amino-functionalized silica host at various functionalization degrees is discussed in details taking into account all structural features, of matrix as well as properties of the drug molecules. The obtained results proved a successful bexarotene loading on amino-functionalized MCM-41 silica. The bexarotene molecules are adsorbed on the active centers in non-crystalline state proving the major role of the silica amino-functionalization for the drug solubility and bioavailability enhancing. In vitro dissolution tests showed a prolonged release of bexarotene during 12 h, reaching 50% release of loaded active molecules. The prolonged release has been demonstrated to be a result of the presence of aminopropyl groups on the silica pore walls.

Size-Controlled Silver Nanoparticles Confined in Ordered Mesoporous Silica and Their Enhanced Catalytic Activities

A cooperative assembly route has been developed, by which silver nanoparticles with controlled sizes are incorporated into the channels of ordered cubic mesoporous silica (KIT-6) with different pore sizes (4.3–6.4[Formula: see text]nm). The samples were characterized by XRD, TEM, FT-IR, UV-Vis and N2physisorption. The pore wall of mesoporous silica can efficiently confine the growth of silver nanoparticles within the channels and their average sizes decreased with the pore size reduction of KIT-6. Catalytic activities of the resultant Ag/KIT-6-[Formula: see text] ([Formula: see text] stands for hydrothermal temperature) composite for reducing harmful organic dye Rhodamine B (Rh B) by sodium borohydride (NaBH4) were investigated. All the Ag/KIT-6 composite samples show great catalytic activities, among which Ag/KIT-6-80 with higher loading and smaller size of Ag nanoparticles exhibits higher catalytic activity than those of Ag/KIT-6-60 and Ag/KIT-6-100.

High Ion Conducting Nanohybrid Solid Polymer Electrolytes via Single-Ion Conducting Mesoporous Organosilica in Poly(ethylene oxide)

A novel mesoporous silica-based single-ion conductor for lithium-ion batteries was prepared via two-step selective functionalization of designated silica precursors into the inner pore wall of mesoporous silica. 2-[(Trifluoromethanesulfonylimido)-N-4-sulfonylphenyl]ethyl (TFSISPE) group was first incorporated as a silica precursor having an anionic weak-binding imide group, and a dense brush of oligo-poly(ethylene glycol) (oligo-PEG) moieties, solvating Li+, was cografted to produce functionalized mesoporous silica (FMS-TFSISPE) nanoparticles. FMS-TFSISPE showed a 2D hexagonal nanopore structure and a regular spherical shape with an average diameter of 50 nm. Poly(ethylene oxide) (PEO) was used to form a dispersion of the mesoporous silica nanoparticles into the polymer matrix. This new polymer–mesoporous silica nanohybrid solid electrolyte with the sole mobile Li ions (FMS-TFSISPE-PEO) exhibits attractive electrical, mechanical, and electrochemical properties. The ionic conductivity and storage modulus b...

Dimensionality of Diffusion in Flow-Aligned Surfactant-Templated Mesoporous Silica: A Single Molecule Tracking Study of Pore Wall Permeability

Flow-aligned mesoporous silica monoliths incorporating nanometer-sized cylindrical pores serve as models for materials with applications in chemical separations and catalysis. In many such systems, it is assumed that incorporated analytes or reagents are confined to and travel along the one-dimensional (1D) pores. Anisotropic motion is often inferred from ensemble measurements and knowledge of the material structure. In this report, single molecule tracking (SMT) is used to directly visualize the diffusive motions of uncharged, cationic, and anionic perylene diimide (PDI) dyes within the monoliths. The monolith pores are filled with Pluronic F127 surfactant, water, and alcohol. SMT data depict both isotropic and anisotropic diffusion for all three dyes. The charged dyes exhibit predominantly isotropic motions, suggesting these molecules readily pass through defects in the silica pore walls. In contrast, the motions of the uncharged PDI evolve to become more anisotropic with monolith aging. Results obtaine...

Conformational States of Ionic Liquid 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide in Bulk and Confined Silica Nanopores Probed by Crystallization Kinetics Study

The nonaqueous sol–gel process has been used to synthesize the “ionogels” by confining ionic liquid (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide; [EMIM][TFSI]) into silica gel matrices. The present study is concerned mainly with probing the conformational states of the IL ([EMIM][TFSI]) through crystallization kinetics study of the bulk and confined ionic liquid (IL) in nanopores of silica matrix. The crystallization kinetics has been studied by the isothermal method using differential scanning calorimetry (DSC). For bulk IL, DSC result shows three crystallization peaks due to different conformations of IL molecules. DSC results show that one of these crystallization peaks disappears upon confinement due to interaction of IL molecules with the silica pore wall surfaces. The crystallization kinetics of bulk and confined IL is quantified using the Avarami analysis. Confinement of IL results in a decrease of the Avarami exponent, indicating one-dimensional crystal growth. To support the res...