Mesoporous Silica SBA-15 Research Articles

Synthesis of sustainable rice husk ash-derived nickel-decorated MCM-41 and SBA-15 mesoporous silica materials for hydrogen storage

To promote sustainability, it is essential to make use of biomass waste to create resources that can be transformed into mesoporous materials like silicates. These materials can be used as effective adsorbents for solid-state H2 storage systems. To meet the requirements of these systems, materials must be inexpensive, possess high specific surface areas, have proper pore arrangements, and exhibit reasonable H2 uptake. In this study, sustainable rice husk ash-derived MCM-41-RHA and SBA-15-RHA mesoporous silica materials were developed. These materials were engineered with different levels of Ni loading (2.5–10 wt%) and are used for H2 storage. The prepared MCM-41-RHA and SBA-15-RHA materials have a high BET-specific surface area of 1092.6 m2/g and 539.2 m2/g, respectively, with a mesopore distribution. The best results were observed for samples with a Ni loading of 5 wt%, such as MCM-41-RHA-Ni5 and SBA-15-RHA-Ni5, which demonstrated the highest H2 uptake of 3.64 wt% and 2.48 wt%, respectively, at 77 K and 1 bar. This was due to the strong interaction between the adsorbent and split over hydrogen despite the decrease in the BET-specific surface area after the incorporation of Ni. The enhanced interaction was evidenced by the increased isosteric heat of adsorption observed for MCM-41-RHA-Ni5 and SBA-15-RHA-Ni5, ranging from 21.1 to 8.1 kJ/mol, in contrast to the range of 6.9 to 4.1 kJ/mol for the pristine MCM-41-RHA and SBA-15-RHA. After five successive H2 uptake/release cycles, more than 92 % of the initial capacity was retained. This study presents a sustainable and cost-effective RHA-derived mesoporous silica material decorated with Ni- nanoparticles for solid-state H2 storage.

Pyrene and Eu3+ modified mesoporous silica used as a fluorescent probe for ratiometric detection of tetracycline antibiotics

The detection of residual tetracycline antibiotics (TCs) in the aquatic environment is important because of the irreversible damage of TCs to the ecosystem and human health. Considering the photostability, sensitivity, and accuracy of the detection systems, mesoporous SBA-15 silica material was an ideal support matrix for improving photostability because it can protect the optical properties of fluorescent signals. To achieve ratiometric detection (with sensitivity and accuracy), pyrene and Eu3+ as two fluorescent signals were implemented into SBA-15, and an organic–inorganic hybrid fluorescent nanoprobe Py/EDTA-SBA-15@Eu3+ was constructed. In the presence of TCs, the red emission of Eu3+ in the nanoprobe was sensitized, and the fluorescence resonance energy transfer occurred from pyrene to Eu3+, resulting in the increased emission of Eu3+ at 617 nm and the decreased emission of pyrene at 384 nm. By monitoring the fluorescent intensity changes at 617 and 384 nm (F617/F384), the nanoprobe achieved the ratiometric detection of oxytetracycline (OTC) and tetracycline (TC) in the range of 0.20–80 and 0.40–80 μM, respectively, with detection limits of 0.18 nM for OTC and 5.83 nM for TC. In addition, the practical application of the nanoprobe was validated in tap water and honey samples.

Experimental study of Cu(en)(H2O)2SO4 embedded into mesoporous silica matrix SBA-15 with the hexagonal arrangement of pores

In this work, we present an experimental study to find the optimal way of encapsulation of the magnetic quasi-two-dimensional system Cu(en)(H2O)2SO4 (en = ethylenediamine = C2H8N2) in mesoporous silica SBA-15 with hexagonal pore morphology with a pore size of 5 nm. Our main goal is to achieve the most significant possible degree of pore filling and to study the effect of encapsulation of complex Cu(en)(H2O)2SO4 in SBA-15 silica on the magnetic properties of the studied complex by means of electron paramagnetic resonance (EPR) and magnetization measurements. It was found that the adsorption equilibrium during the adsorption of the Cu(en)(H2O)2SO4 complex from the solution to SBA-15 was reached after only 24 h, and the samples prepared by adsorption for a longer time (72 h, 14 days) did not show an increased amount of the loaded complex. The degree of pore filling represents around 60 % of the total volume of internal pores. The analysis of temperature dependence of susceptibility, the field dependence of magnetization, and EPR spectra showed that due to the encapsulation of Cu(en)(H2O)2SO4 complex in mesoporous silica, the magnetic correlations between Cu(II) ions are significantly weakened, yielding paramagnetic behavior in the studied system.

Functionalization of SBA-15 mesoporous silica for highly efficient adsorption of glutathione: Characterization and modeling studies

BackgroundPristine SBA-15 and amine or thiol-functionalized SBA-15 materials were synthesized, characterized, and highlighted by studying the glutathione (GSH) adsorption process in aqueous solutions. MethodsIn this study, SBA-15 mesoporous materials were functionalized with 3-aminopropyltriethoxysilane (APTS) and (3-mercaptopropyl)triethoxysilane (MPTES) in order to introduce amine and thiol groups onto the surface by using a post-grafting method, respectively. For comparison, the SBA-15-based materials were used as adsorbents to further investigate the adsorption behaviour of GSH under various experimental conditions. Significant findingsTo examine the underlying mechanism of the adsorption process, the kinetics of the GSH adsorption onto SBA-15-based adsorbents were fitted using pseudo-first order, pseudo-second order, Elovich, and Aharoni models. Adsorption isotherms showed that the Freundlich isotherm model was the most appropriate to simulate the adsorption of GSH molecules onto SBA-15-NH2 adsorbent and the Langmuir isotherm model for the two other substrates. In addition, the adsorption thermodynamics confirmed the exothermic behaviour of GSH adsorption process onto the SBA-15-SH adsorbent. In contrast, the capture of GSH molecules by the SBA-15-OH and SBA-15-NH2 adsorbents follows an endothermic reaction process. Finally, the adsorption nature of GSH onto SBA-15 adsorbents is classified as physisorption.

Evaluation of tumor growth remission in a murine model for subcutaneous solid tumors – Benefits of associating the antitumor agent crotamine with mesoporous nanosilica particles to achieve improved dosing frequency and efficacy

Crotamine is a highly cationic polypeptide first isolated from South American rattlesnake venom, which exhibits affinity for acidic lysosomal vesicles and proliferating cells. This cationic nature is pivotal for its in vitro cytotoxicity and in vivo anticancer actions. This study aimed to enhance the antitumor efficacy of crotamine by associating it with the mesoporous SBA-15 silica, known for its controlled release of various chemical agents, including large proteins. This association aimed to mitigate the toxic effects while amplifying the pharmacological potency of several compounds. Comprehensive characterization, including transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential analysis, confirmed the successful association of crotamine with the non-toxic SBA-15 nanoparticles. The TEM imaging revealed nanoparticles with a nearly spherical shape and variations in uniformity upon crotamine association. Furthermore, DLS showed a narrow unimodal size distribution, emphasizing the formation of small aggregates. Zeta potential measurements indicated a distinct shift from negative to positive values upon crotamine association, underscoring its effective adsorption onto SBA-15. Intraperitoneal or oral administration of crotamine:SBA-15 in a murine melanoma model suggested the potential to reduce the frequency of crotamine doses without compromising efficacy. Interestingly, while the oral route enhanced the antitumor efficacy of crotamine, pH-dependent release from SBA-15 was observed. Thus, associating crotamine with SBA-15 could reduce the overall required dose to inhibit solid tumor growth, bolstering the prospect of crotamine as a potent anticancer agent.

Orange Carotenoid Protein in Mesoporous Silica: A New System towards the Development of Colorimetric and Fluorescent Sensors for pH and Temperature.

Orange carotenoid protein (OCP) is a photochromic carotenoprotein involved in the photoprotection of cyanobacteria. It is activated by blue-green light to a red form OCPR capable of dissipating the excess of energy of the cyanobacterial photosynthetic light-harvesting systems. Activation to OCPR can also be achieved in the dark. In the present work, activation by pH changes of two different OCPs-containing echinenone or canthaxanthin as carotenoids-is investigated in different conditions. A particular emphasis is put on OCP encapsulated in SBA-15 mesoporous silica nanoparticles. It is known that in these hybrid systems, under appropriate conditions, OCP remains photoactive. Here, we show that when immobilised in SBA-15, the OCP visible spectrum is sensitive to pH changes, but such a colorimetric response is very different from the one observed for OCP in solution. In both cases (SBA-15 matrices and solutions), pH-induced colour changes are related either by orange-to-red OCP activation, or by carotenoid loss from the denatured protein. Of particular interest is the response of OCP in SBA-15 matrices, where a sudden change in the Vis absorption spectrum and in colour is observed for pH changing from 2 to 3 (in the case of canthaxanthin-binding OCP in SBA-15: λMAX shifts from 454 to 508 nm) and for pH changing from 3 to 4 (in the case of echinenone-binding OCP in SBA-15: λMAX shifts from 445 to 505 nm). The effect of temperature on OCP absorption spectrum and colour (in SBA-15 matrices) has also been investigated and found to be highly dependent on the properties of the used mesoporous silica matrix. Finally, we also show that simultaneous encapsulation in selected surface-functionalised SBA-15 nanoparticles of appropriate fluorophores makes it possible to develop OCP-based pH-sensitive fluorescent systems. This work therefore represents a proof of principle that OCP immobilised in mesoporous silica is a promising system in the development of colorimetric and fluorometric pH and temperature sensors.

Design and synthesis of ZnGlu MOF/SBA-16 nanocomposite, and its performance as an environmentally friendly nanocomposite for solvent-free chemical fixation of CO2 to epoxides for high-yield synthesis of cyclic carbonates

In this study, ZnGlu MOF has been immobilized into hexagonal mesoporous silica SBA-16 to fabricate ZnGlu MOF/SBA-16 hybrid material. The prepared hybrid material was introduced as a sustainable green nanocomposite for CO2 epoxidation to cyclic carbonates under solvent-free conditions at low pressure of CO2 (5 bar). The structure of the obtained nanocomposites is authenticated using various analytical techniques like FT-IR, XRD, SAXRD, CO2-TPD, NH3-TPD, BET, TEM, FE-SEM, EDX, EDX-mapping, and ICP-OES. For making a greener process, ZnGlu MOF/SBA-16 nanocomposite showed remarkable catalytic activity for converting CO2 with diverse epoxides toward five-membered cyclic carbonates prepared without using any toxic metals and reagents. The presence of the mesoporous silica SBA-16 has improved reactants diffusion and molecular accessibility for suitable interactions in Lewis acid centers, which led to MOFs outperforming in the efficient chemical fixation of CO2. Also, the essential role of free amino groups in ZnGlu MOF was shown as base sites and H-bonding groups when suggesting a possible reaction mechanism. This efficient, and convenient catalytic system can be separated by filtration, and its original activity was maintained for five successive cycles under the same reaction conditions. The above nanocomposite, with great potential, can be used to catalyze different chemical reactions for industrial purposes.

Distribution and Mobility of Amines Confined in Porous Silica Supports Assessed via Neutron Scattering, NMR, and MD Simulations: Impacts on CO2 Sorption Kinetics and Capacities.

ConspectusSolid-supported amines are a promising class of CO2 sorbents capable of selectively capturing CO2 from diverse sources. The chemical interactions between the amine groups and CO2 give rise to the formation of strong CO2 adducts, such as alkylammonium carbamates, carbamic acids, and bicarbonates, which enable CO2 capture even at low driving force, such as with ultradilute CO2 streams. Among various solid-supported amine sorbents, oligomeric amines infused into oxide solid supports (noncovalently supported) are widely studied due to their ease of synthesis and low cost. This method allows for the construction of amine-rich sorbents while minimizing problems, such as leaching or evaporation, that occur with supported molecular amines.Researchers have pursued improved sorbents by tuning the physical and chemical properties of solid supports and amine phases. In terms of CO2 uptake, the amine efficiency, or the moles of sorbed CO2 per mole of amine sites, and uptake rate (CO2 capture per unit time) are the most critical factors determining the effectiveness of the material. While structure-property relationships have been developed for different porous oxide supports, the interaction(s) of the amine phase with the solid support, the structure and distribution of the organic phase within the pores, and the mobility of the amine phase within the pores are not well understood. These factors are important, because the kinetics of CO2 sorption, particularly when using the prototypical amine oligomer branched poly(ethylenimine) (PEI), follow an unconventional trend, with rapid initial uptake followed by a very slow, asymptotic approach to equilibrium. This suggests that the uptake of CO2 within such solid-supported amines is mass transfer-limited. Therefore, improving sorption performance can be facilitated by better understanding the amine structure and distribution within the pores.In this context, model solid-supported amine sorbents were constructed from a highly ordered, mesoporous silica SBA-15 support, and an array of techniques was used to probe the soft matter domains within these hybrid materials. The choice of SBA-15 as the model support was based on its ordered arrangement of mesopores with tunable physical and chemical properties, including pore size, particle lengths, and surface chemistries. Branched PEI─the most common amine phase used in solid CO2 sorbents─and its linear, low molecular weight analogue, tetraethylenepentamine (TEPA), were deployed as the amine phases. Neutron scattering (NS), including small angle neutron scattering (SANS) and quasielastic neutron scattering (QENS), alongside solid-state NMR (ssNMR) and molecular dynamics (MD) simulations, was used to elucidate the structure and mobility of the amine phases within the pores of the support. Together, these tools, which have previously not been applied to such materials, provided new information regarding how the amine phases filled the support pores as the loading increased and the mobility of those amine phases. Varying pore surface-amine interactions led to unique trends for amine distributions and mobility; for instance, hydrophilic walls (i.e., attractive to amines) resulted in hampered motions with more intimate coordination to the walls, while amines around hydrophobic walls or walls with grafted chains that interrupt amine-wall coordination showed recovered mobility, with amines being more liberated from the walls. By correlating the structural and dynamic properties with CO2 sorption properties, novel relationships were identified, shedding light on the performance of the amine sorbents, and providing valuable guidance for the design of more effective supported amine sorbents.

Removal of aqueous uranyl ions using titania-supported mesoporous silica composite with the synergistic effect of coupled adsorption and photocatalytic reduction of U(VI)

The aim of this study is to determine and compare the adsorption capacities, kinetic and thermodynamic parameters of the adsorption process of uranyl ions from aqueous solution on nanotube titania impregnated mesoporous silica SBA-15 (TNT-SBA-15) and naked SBA-15 (nSBA-15) adsorbents. The TNT-SBA-15 composite containing various molar ratio of nanotube titania to silica (TNT-SBA-15(m:n)) in the matrix was synthesized by the sol–gel/impregnation method using sodium silicate as a silica precursor, sulphuric acid and nanotube titania. Batch adsorption experiments showed that the maximum adsorption capacity (qmax) of the TNT-SBA-15(m:n = 1:1) composite under indoor light be as high as 2.65 mMoleU g−1 that was 1.4 times higher than that of nSBA-15 under the same conditions. Under UV (300 W) illumination the qmax of TNT-SBA-15(1:1) adsorbent reached 3.49 mMoleU g−1 that was 2 times higher than the qmax in the dark. The increase in qmax of the TNT-SBA-15(1:1) composite in the two experiments was attributed to the synergistic effect of coupled sorption and photocatalytic reduction of U(VI) by titania following the deposition of uranium (IV) (hydr)oxide on the surface of the adsorbent. The adsorption process followed a pseudo-second kinetic model. The activation energy was found to be 160 and 135 kJ Mole−1 for the adsorption on nSBA-15 and TNT-SBA-15(1:1), respectively. The isotherm of the adsorption process follows the Langmuir as well as Freundlich models. The adsorption is an endothermic and spontaneous process. Adsorbed TNT-SBA-15 can be easily regenerated in 0.3 M HNO3 solution, and the qmax of the adsorbent was maintained at 95% the initial qmax after three consecutive adsorption–desorption cycles. These results revealed that, though TNT-SBA-15 made from inexpensive reagents could be an effective adsorbent for uranyl removal from wastewater.

The Critical Role of Ligand Flexibility on the Activity of Free and Immobilized Mn Superoxide Dismutase Mimics

In low-molecular-weight Mn superoxide dismutase (SOD) mimics, the ligand plays a key role in tuning the reactivity of the metal center with O2•−. We used three ligands differing in their donor sites, flexibility and/or charge, to compare the redox properties and SOD activity of the resulting Mn complexes: 1,3-bis[(pyridin-2-ylmethyl)(propargyl)amino]propane (pypapn), 1,3-bis(pyridin-2-ylmethyleneamino)propane (py2pn) and 1,4-bis(salicylidenamino)butane (H2salbn). These ligands afford Mn complexes that, in aqueous solution, exist as mononuclear species [Mn(II)(pypapn)(H2O)2]2+, [Mn(II)(py2pn)(H2O)2]2+ and [Mn(III)(salbn)(H2O)2]+. The relative reactivity of these compounds with O2•− at pH 7.8, [Mn(pypapn)(H2O)2]2+ > [Mn(salbn)(H2O)2]+ > [Mn(py2pn)(H2O)2]2+, is independent of the redox potential but strongly depends on the ligand flexibility which becomes a critical feature when the reaction occurs through an inner-sphere electron-transfer mechanism. Immobilization was used to isolate and protect the catalyst from dissociation or dimerization during catalysis. [Mn(pypapn)(H2O)2]2+, with the alkyne group, was covalently grafted to azide functionalized mesoporous silica through click chemistry, while [Mn(py2pn)(solv)2]2+ and [Mn(salbn)(solv)2]+ were encapsulated in SBA-15 mesoporous silica through ionic exchange. The retention or enhancement of the SOD activity and the improved stability of the covalently attached catalyst and the doubly charged complex encapsulated in the silica pores, make them suitable for use in aqueous media.

Hydrogen sulfide removal from low concentration gas streams using metal supported mesoporous silica SBA-15 adsorbent

The removal of hydrogen sulfide (H2S) from gas mixtures is paramount as it can cause environmental damage, corrosion, and catalyst poisoning even at low concentration levels (100–200 mg/L). In this work, a series of Fe-Cu oxides supported SBA-15 materials were prepared using the wet incipient impregnation method with different Fe and Cu atomic ratios to evaluate the H2S removal performance. It was found that the H2S adsorption capacity generally increases with an increase in the CuO loading, with a Cu-Fe atomic ratio of 1.0:0.3 displaying the highest breakthrough H2S adsorption capacity of 74.08 mg H2S/g-sorbent. Through the XPS results, the adsorbent existed in the form of sulfate, sulfide, and elemental sulfur after reacting with H2S. In particular, it was confirmed that Fe2O3 helps to improve the H2S removal performance by creating an alkaline environment. The material with superior performance showed high capacity at low concentration compared to several published reports.

Urea-Functionalized mesoporous silica SBA-15 for heavy metal Adsorption: Synthesis, Characterization, and optimization

This study investigates chromium, cadmium, and lead ions adsorption on mesoporous silica SBA-15 functionalized by the urea amine group (Urea-SBA-15). Parameters affecting adsorption by Urea-SBA-15 were the initial concentration of heavy metals, contact time, pH, adsorbent concentration, and temperature. Optimum adsorption performance was achieved at pH = 2.5 for Cr(VI), pH = 5 for Cd(II), and pH = 4 for Pb(II), a contact time of 2 h for Cr(VI) and Cd(II) and 1.5 h for lead, an adsorbent concentration of 2.5 g/L, temperature equal to 45 °C, and a heavy metals concentration of 25 ppm. The obtained results were consistent with Langmuir and pseudo-second-order models. The highest adsorption capability for Cr(VI), Cd(II), and Pb(II) were 26.83, 30.53, and 43.85 mg/g, respectively. Laboratory results showed that due to an increased adsorption capacity, the Urea-SBA-15 adsorbent is promising for heavy metal ions removal from water resources.

Honeycomb-like SBA-15 parceled in 2D GO for ultrafiltration membranes fabrication with ultrahigh permeability and enhanced anti-fouling performance

Novel 3D mesoporous silica SBA-15 and 2D graphene oxide (GO) composite nano-fillers incorporated polysulfone (PSf) ultrafiltration (UF) membranes (GO-SBA-15/PSf) were first prepared via blending modifications by non-solvent induced phase separation (NIPs). 3D honeycomb-like SBA-15 not only improved the surface hydrophilicity but also provided extra nano-channels parceled in 2D GO networks for convenient hydrone transport via confinement-effect. The lamellar GO networks relieved the agglomeration of inorganic materials inside the polymer, anticipating in the interfacial polymerization reaction. GO-SBA-15/PSf UF membranes were systematically investigated using contact angle, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscope (AFM) and Brunauer-Emmett-Teller (BET) methods. The pure water flux reached 641.7 L m-2h−1 which was 3 times than that of pristine PSf membranes (229.2 L m-2h−1) under the pressure of 0.1 MPa. Negative charge of GO generated electrostatic repulsion with protein, which facilitated a high rejection of 98.22% and excellent FRR value of 85% that was 1.5 times than that of pristine PSf membranes (58%). The UF membranes fabricated by new multidimensional nano-fillers overcame the trade-off effect between permeability and protein rejection.

Preparation of β-Cyclodextrin Conjugated, Gelatin Stabilized SBA 15-CuInS2/ZnS Quantum Dot Nanocomposites for Camptothecin Release

Camptothecin (CPT) is a potential anticancer drug. However, it faces challenges due to its poor water solubility and the need for an efficient drug release system. Herein, we developed a novel system composed of gelatin stabilized, mesoporous silica SBA15 encapsulated CuInS2/ZnS (CIS/ZnS) quantum dots (QDs) conjugated with β-cyclodextrin (β-CDs) for its potential use in the release of CPT. In this multifunctional system, β-CDs served as the drug carrier, SBA15 encapsulated QDs is capable of imaging and the gelatin was used to enhance the carrier-drug interaction. Fourier transform infrared (FTIR) analysis confirmed the successful conjugation of β-CDs to the Gel-SBA15 CIS/ZnS QDs, while optical analyses revealed excellent emission properties and high photostability. The β-CD-conjugated Gel-SBA15-CIS/ZnS QD nanocomposite was used to obtain the soluble derivate of CPT which further demonstrated a drug release profile following the triphasic model. Overall, the improved photostability and acceptable drug release profile of the β-CD conjugated Gel-SBA15-CIS/ZnS QD nanocomposite hold great promise for both imaging and therapeutic applications.Graphical

Melamine functionalized mesoporous silica SBA-15 for separation of chromium (VI) from wastewater

In this study, a Melamine-functionalized mesoporous silica-SBA-15 (Melamine-MS-SBA-15) adsorbent was synthesized to remove Cr(VI) from wastewater. The mesoporous silica-SBA-15 adsorbent was first synthesized using the hydrothermal method and post-synthesis under toluene reflux. Then, 3-aminopropyl trimethoxy silane was added to the adsorbent surface and it was further modified by melamine to obtain the final product. SBA-15 well-performed after Melamine functionalization against the Cr(VI) removal due to the conversion of physisorption to chemisorption adsorption. The adsorption of Cr(VI) using the Melamine-MS-SBA-15 was studied. XRD, BET, SEM, FTIR, TGA, and zeta potential analyses were used to characterize the adsorbent. Parameters affecting adsorption including pH (3–9), initial concentration (20–200 ppm), contact time (1–24 h), adsorbent dose (1.5–15 mg L−1), and temperature (18–30 °C). Optimal results were pH = 3, an initial concentration of 20 ppm, an adsorbent dose of 4 mg L−1, a contact time of 6 h, and a temperature of 18 °C. The results of isotherm and kinetics model studies were consistent with Temkin and pseudo-second-order models, respectively. The thermodynamics parameters confirmed the spontaneous reaction. Experimental results showed that functionalization of the adsorbent surface of MS-SBA-15 with melamine increased the adsorption efficiency and adsorption capacity. The highest adsorption capacity for Cr(VI) was about 50 mg/g. The maximum adsorption efficiency for solutions containing Cr(VI) was about 84%. Increasing the adsorption concentration in a fixed value of the heavy metal concentration increased the adsorption capacity and increasing the heavy metal concentration, increased the adsorption capacity.

Nonionic surfactant-templated mesoporous silica as supports for nickel active catalysts in liquid phase organic compounds oxidation

Three surfactants were selected from a series of EOx/POy/EOx triblock copolymers and ethoxylated octylphenol as nonionic templating agents for the synthesis of silica mesoporous materials at room temperature and by hydrothermal treatment. The surfactants were ethylene oxide-propylene oxide-ethylene oxide tri-block copolymers (Pluronic F68) and a polydisperse ethoxylated octylphenol (Triton X-100). The obtained materials were compared with SBA-15 mesoporous silica synthesized with Pluronic P123 surfactant and were used as support to obtain Ni and NiTi-silica catalysts (2.5% NiO, 5% TiO2). The synthesized materials were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption, IR and UV-Vis spectroscopy. Catalytic and photocatalytic activity of Ni and NiTi-silica samples were tested, with and without H2O2, for phenol and Brilliant Blue FCF dye oxidative degradation in the liquid phase. The obtained results showed a significant effect of surfactant on silica structure, morphology and texture, and catalytic and photocatalytic properties.

Effect of Surface Organo-Silanization on SBA-15 Mesoporous Silicas in CO2 Adsorption Processes: Design, Synthesis, and Computational Studies

Carbon dioxide solid sorbents produced from mesoporous functionalized silica microparticles (SBA-15) have been investigated (i) theoretically using density functional theory and (ii) evaluated empirically for assessing their CO2 adsorption capacity. Two different families of organosilyl groups have been tested possessing a common anchoring group (silanol), in one extreme, but bearing two different types of CO2 sensitive groups in the other extreme; (i) hyperbranched polymeric PAMAM moieties, carrying multiple −NH2 groups, and (ii) a collection of linear functional ending groups such as −SH, −SO3H, −guanidine (Gdn), −NH2, −NCO, and −N3. The adsorption isotherms revealed that SBA-15 bearing (3-aminopropyl)triethoxysilane (APTES) showed an impressive 3.4-fold adsorption enhancement at 1 bar and 50 °C when compared to the pristine SBA-15, following a straightforward synthetic protocol. The maximum adsorption capacity was increased from 0.34 mmol/g (SBA-15) to 1.15 mmol/g (SBA-15@NH2) under conditions relevant to CO2 capture (1 bar and 50 °C). We also found intriguing certain discrepancies observed between the calculated CO2 isotherms and the theorized binding energy in two of the materials. This will be addressed in the present work.

Probing the Morphology and Mobility of Amines in Porous Silica CO2 Sorbents by 1H T1–T2 Relaxation Correlation NMR

Molecular and oligomeric amines supported in porous oxide supports are a promising class of CO2 sorbent materials studied for CO2 removal from diverse streams such as flue gas and ambient air. Among the various amines investigated, low molecular weight, hyperbranched poly(ethyleneimine) (PEI), and tetraethylenepentamine (TEPA) are among the most extensively studied. While macroscopic structure–performance relationships relating the support structure, amine loading, and other factors affecting CO2 sorption capacities and kinetics have been developed, structural and dynamic information about the organic amine phase in the porous support is less plentiful. The structure and mobility of amines impregnated in the pores of porous supports directly impact gas sorption, as the accessibility of amine sites in the pores directly relates to amine distribution in the pores and overall pore filling as well as the dynamics of the amine chains. Here, we prepare a family of mesoporous silica SBA-15 materials containing varying loadings of oligomeric (PEI) and molecular (TEPA) amines. 1H T1–T2 relaxation correlation solid-state NMR experiments are used to characterize the structural and dynamic properties of the confined amines. Both TEPA and PEI are shown to form multiple different domains in the pores, each with distinguishable dynamic properties. TEPA and PEI form more rigid layers around the silica support walls at lower organic loading fractions, characterized by lower mobilities, followed by the formation of more mobile domains less engaged in pore wall interactions at higher loadings. TEPA shows faster mobilities than PEI because of its lower molecular weight. TEPA also appears to more easily transfer between domains within the pores, leading to generally faster CO2 uptake rates with higher sorption capacities, while PEI located closer to the pore walls remained much less mobile and is thus less engaged in CO2 capture.

Glassy and Rubbery Epoxy Composites with Mesoporous Silica

The reinforcing efficiency of SBA-15-type mesoporous silica, when used as additive in epoxy polymers, was evaluated in this study. The effects of silica loading and its physicochemical characteristics on the thermal, mechanical, and viscoelastic properties of glassy and rubbery epoxy mesocomposites were examined using SBA-15 mesoporous silicas with varying porosities (surface area, pore size, and volume), particle sizes, morphologies, and organo-functionalization. Three types of SBA-15 were used: SBA-15 (10) with 10 nm pore diameters and long particles, SBA-15 (5) with 5 nm pore diameters and short particles, and SBA-15 (sc) with 10 nm pore diameters and short particles (“sc” for short channel). SBA-15 (10) was modified with propyl-, epoxy-, and amino-groups to study the effect of functionalization. The glassy or rubbery epoxy polymers and mesocomposites were produced by the crosslinking of a diglycidyl ether of bisphenol A (DEGBA) epoxy resin with isophorone diamine (IPD) or Jeffaminje D-2000, respectively. Mesoporous silica was uniformly dispersed inside the polymer matrices; however, the opacity levels between the rubbery and glassy samples were different, with completely transparent rubbery composites being prepared with as high as a 9 wt. % addition of SBA-15. The mechanical and thermal performance properties of the mesocomposites were dependent on both the type of the curing agent, which affected the cross-linking density of the pristine polymer matrix, and the characteristics of the mesoporous silica variants, being, in general, improved by the addition of up to 6 wt. % silica for the glassy polymers and up to 9 wt. % for the rubbery polymers.

Effect of CeO2/spherical silica and halloysite nanotubes engineered for targeted drug delivery system to treat breast cancer cells

Cerium oxide nanoparticles (CeO2 NPs) and flavonoid curcumin that has been widely studied for treating diseases involving high reactive oxygen species (ROS). In nanotherapeutics, the particle size, shape, metal oxide dispersity and surface properties of nanocarriers are vital for drug delivery and therapeutic efficiency. Here, cisplatin release behavior on cerium impregnated two different shaped nanocarriers, CeO2/monodispersed spherical silica (Sil) and CeO2/halloysite (Hal) nanotube was studied for potential anti-cancer therapies. For comparison, CeO2 impregnated mesoporous silica MCM-41, SBA-16, Hydroxyapatite and clay were prepared. Subsequently, the nanocomposites were coated with curcumin (25% wt/wt), and cisplatin (Cp) functionalization (5% wt/wt). 5wt%CeO2/Hal/Cp and 5wt%CeO2/Sil/Cp samples were pegylated using lyophilization technique. Physico-chemical analyses revealed the nanosized distribution of CeO2 and functionalization of cisplatin and curcumin. Cp release was studied using automated Franz cell and dialysis membrane techniques. The different structured nanocarriers delivering mechanism was studied by determining the drug kinetic release using four different kinetic models (first order, second order, Higuchi and Korsmeyer-Peppas). In vitro cytotoxicity assay of nano formulations along with free cisplatin and curcumin (Cur) were tested against the breast cancer cell line (MCF-7) for multiple timepoints by MTT assay. The results reveled the efficacy of 5wt%CeO2/Sil/Cp/Cur nanoparticles in delivering cisplatin. On the other hand, 5wt%CeO2/Hal/Cur nanoparticles enhanced the uptake of curcumin in comparison to free curcumin. Overall, pegylated CeO2/Silica nano formulation demonstrated an effective carrier to cisplatin for potential treatment of breast cancer.