Silica Santa Barbara Amorphous-15 Research Articles

Amine-Impregnated Dendritic Mesoporous Silica for the Adsorption of Formaldehyde.

To adsorb and remove formaldehyde, which is a harmful volatile organic chemical (VOC) detected indoors, an alkylamine was introduced into the substrate as a formaldehyde adsorbent. In this study, Tetraethylenepentaamine (TEPA) was introduced into the mesoporous silica using the amine impregnation method. Since the impregnated alkylamine can block the pores of the silica substrate, the pore size and pore volume are very important factors for its use as a substrate for an adsorbent. Focusing on the substrate's pore properties, Santa Barbara Amorphous-15 (SBA-15) was chosen as a conventional one-dimensional pore-structured mesoporous silica, and dendritic mesoporous silica (DMS) as a three-dimensional pore-structured mesoporous silica. To 1 g each of silica substrate DMS and SBA-15, 0, 0.5, 1.5, and 2.5 g of TEPA were introduced. A fixed concentration and amount of formaldehyde gas was flowed through the adsorbent and then the adsorbent was changed to the 2,4-Dinitrophenylhydrazine (2,4-DNPH) cartridge to adsorb the remaining formaldehyde. According to the methods recommended by the World Health Organization (WHO) and National Institute for Occupational Safety & Health (NIOSH), the formaldehyde captured by 2,4-DNPH was analyzed using high-performance liquid chromatography (HPLC). A comparison of DMS and SBA-15 in the amine impregnation method shows that not only surface area, but also large pore size and high pore volume, contribute to the formaldehyde adsorption ability.

Antitumor potential of cisplatin loaded into SBA-15 mesoporous silica nanoparticles against B16F1 melanoma cells: in vitro and in vivo studies

CP (cisplatin) and mesoporous silica SBA-15 (Santa Barbara amorphous 15) loaded with CP (→SBA-15|CP) were tested in vitro and in vivo against low metastatic mouse melanoma B16F1 cell line. SBA-15 only, as drug carrier, is found to be not active, while CP and SBA-15|CP revealed high cytotoxicity in lower μM range. The activity of SBA-15|CP was found similar to the activity of CP alone. Both CP and SBA-15|CP induced inhibition of cell proliferation (carboxyfluorescein succinimidyl ester - CFSE assay) along with G2/M arrest (4′,6-diamidino-2-phenylindole - DAPI assay). Apoptosis (Annexin V/ propidium iodide - PI assay), through caspase activation (apostat assay) and nitric oxide (NO) production (diacetate(4-amino-5-methylamino-2′,7′-difluorofluorescein-diacetat) - DAF FM assay), was identified as main mode of cell death. However, slight elevated autophagy (acridine orange - AO assay) was detected in treated B16F1 cells. CP and SBA-15|CP did not affect production of ROS (reactive oxygen species) in B16F1 cells. Both SBA-15|CP and CP induced in B16F1 G2 arrest and subsequent senescence. SBA-15|CP, but not CP, blocked the growth of melanoma in C57BL/6 mice. Moreover, hepato- and nephrotoxicity in SBA-15|CP treated animals were diminished in comparison to CP confirming multiply improved antitumor potential of immobilized CP. Outstandingly, SBA-15 boosted in vivo activity and diminished side effects of CP.

Composites of nanodimensional glass in the system Na2O–SiO2/Mesoporous silica and their high ionic conductivity

Nanodimensional glass samples of compositions xNa2O-(100–x)SiO2, with x having values of 25, 35, and 45, have been synthesized within the nanochannels of diameter ca. 5 nm of mesoporous silica SBA-15 (Santa Barbara Amorphous 15) by a sol–gel technique. The dc electrical conductivities of the nanocomposites, as well as of bulk glasses, have been determined in the temperature range 300–500 K by carrying out ac impedance measurements over the frequency range 20 Hz to 1 MHz on samples of diameter ca. 10 mm and thickness ca. 0.7 mm, and determining the intersection points of the arcs of circles in the complex impedance plots at high frequency with the real axis. The conductivities of the nanocomposites were found to be 4–5 orders of magnitude higher than those of the corresponding bulk glasses at room temperature. This may be ascribed to the presence of greater free volume in the nanoglasses as compared to their bulk counterparts, thus providing faster pathways for ion migration therein, and hence drastically lowering the activation energy of sodium ion migration. The nanocomposite with 45 mol% Na2O exhibited an electrical conductivity of the order of 10−3 S cm−1 at room temperature (ca. 300 K). The nanocomposites also showed outstanding electrochemical performances. The maximum specific capacitance was seen for the nanocomposite with nanoglass composition 45Na2O–55SiO2, amounting to 1344 F/g at a scan rate of 10 mV/s. Around 88.8% retention of capacitance over 100 successive cycles indicates good sustainability of the samples. These nanocomposites are thus highly promising for the fabrication of solid-state sodium-ion batteries.

Supersaturable organic-inorganic hybrid matrix based on well-ordered mesoporous silica to improve the bioavailability of water insoluble drugs

Mesoporous silica with uniform 2-D hexagonal pores has been newly employed as facile reservoir to impove the dissolution rate of water insoluble drugs. However, rapid drug release from mesoporous silica is usually accompanied by the generation of supersaturated solution, which leads to the drug precipitation and compromised absorption. To address this issue, a supersaturated ternary hybrid system was constructed in this study by utilizing inorganic mesoporous silica and organic precipitation inhibitor. Vinylprrolidone-vinylacetate copolymer (PVP VA64) with similar solubility parameter to model drug fenofibrate (FNB) was expected to well inhibit the precipitation. Mesoporous silica Santa Barbara amorphous-15 (SBA-15) was synthesized in acidic media and hybrid matrix was produced by hot melt extrusion technique. The results of in vitro supersaturation dissolution test obviously revealed that the presence of PVP VA64 could effectively sustain a higher apparent concentration. PVP VA64 was suggested to simultaneously reduce the rate of nucleation and crystal growth and subsequently maintain a metastable supersaturated state. The absorption of FNB delivered by the organic-inorganic hybrid matrix was remarkably enhanced in beagle dogs, and its AUC value was 1.92-fold higher than that of FNB loaded mesoporous silica without PVP VA 64. In conclusion, the supersaturated organic-inorganic hybrid matrix can serve as a modular strategy to enhance the oral availability of water insoluble drugs.

Multifunctional and Environmentally Friendly TiO2-SiO2 Mesoporous Materials for Sustainable Green Buildings.

This work deals with the formulation of environmentally friendly, cheap, and readily-available materials for green building applications, providing the function of air purificator by improving the safety and the comfort of an indoor environment. High surface area TiO2–SiO2 samples, prepared by a simple, cost effective, and scalable synthetic approach, proved to be effective in maximizing the properties of each component, i.e., the photocatalytic properties of titania and the high surface area of silica. TiO2 was introduced onto an ordered mesoporous silica Santa Barbara Amorphous-15 (SBA-15), that is featured by interesting insulating features, by using an incipient wetness impregnation method. The photocatalytic activity was evaluated in gas phase oxidation of ethylbenzene, which was selected as model volatile organic compound (VOC) molecule. The morphological, textural and structural features along with the electronic properties, the hydrophilicity and heat capacity of the materials were investigated in depth by scanning electron microscopy, powder X-ray diffraction, N2 physisorption, diffuse reflectance UV-Vis, FT-IR spectroscopies, and modulated DSC (MDSC) dynamic scan. Outstanding performances in the ethylbenzene abatement results are promising for further application in the green building sector.

Phase Behavior and Ion Dynamics of Nanoconfined LiBH4 in Silica

The increasing demand for high capacity yet safe storage of renewable energy calls for the development of all-solid-state batteries. A major hurdle in this development is the identification of new suitable types of solid-state electrolytes. Nanoconfined lithium borohydride is a solid-state electrolyte candidate due to its high lithium-ion mobility at ambient temperatures. The origin of the high lithium-ion mobility is not fully understood, however. We studied nanocomposites of lithium borohydride and nanoporous silica Santa Barbara Amorphous-15 (SBA-15) with different pore sizes, using 1H, 6,7Li, and 11B solid-state NMR at various temperatures, to get in-depth insights into the phase behavior and ion dynamics of lithium borohydride in the silica pores. The results allow us to formulate a detailed model for lithium borohydride confined in SBA-15; bulklike LiBH4 is separated from the pore walls by an amorphous, highly LiBH4 fraction displaying both Li+ and BH4 - diffusion even at ambient temperatures. As shown by 11B temperature-jump exchange NMR, this fraction increases as a function of temperature. Li+ exchange between the bulklike and dynamic LiBH4 fraction is slow at ambient temperatures, but at elevated temperatures (≥90 °C), above the phase transition of the bulklike fraction, lithium ions rapidly diffuse through both LiBH4 fractions and exchange between these confined fractions at rates approaching the megahertz time scale.

Giant magnetodielectric effect in composites of nanodimensional spin glass of system CoO-SiO2 and mesoporous silica SBA-15

Abstract Nanodimensional silica-based spin glasses of compositions xCoO-(100-x)SiO2 with x having values 20 and 30 were synthesized by sol-gel method within mesoporous silica SBA-15 (Santa Barbara Amorphous-15) having a pore diameter ~5.5 nm. X-ray photoelectron spectroscopy (XPS) analysis showed the presence of both Co2+ and Co3+ species within the glasses. This caused electronic conduction in this amorphous system. The nanoglasses exhibited resistivity values at room temperature which were about three orders of magnitude lower than those of the corresponding bulk glasses. The resistivity data for the nanodimensional glasses on analysis confirmed the conduction to arise due to small polaron hopping between the localized states represented by these ions with an activation energy in the range 0.08–0.07 eV. The inter-site separation values extracted from the analysis of the resistivity data were found to lie in the range 6.7–6.6 A. The values of magnetodielectric (MD) parameter for the different nanocomposites were rather large with the highest value found to be in the range 523–49% for the frequencies 1 kHz and 1 MHz in case of nanocomposite with a glass composition 30CoO-70SiO2. The dissipation factor for the samples was, however, in the range 0.3–1.6. By using suitable measuring frequency the dissipation factor could be brought down to a value less than 1.0 with the M.D. parameter exhibiting values in the range 10–49%. The results were fitted to Catalan’s model based on two dielectrics with different resistivity values connected in series. The satisfactory fit of the experimental data to the theoretical model based on a negative magnetoresistance of the nanoglasses leads to the conclusion that an enhancement of spin polarized electron hopping is the reason behind this effect. The results obtained should be further explored to find applications of these materials as magnetic sensors as well as magnetically controlled supercapacitors.

Co-enhance bioactive of polymer scaffold with mesoporous silica and nano-hydroxyapatite

Mesoporous silica Santa Barbara Amorphous-15 (SBA15) and nano-hydroxyapatite (nHA) were introduced in poly-l-lactic acid (PLLA) scaffold fabricated by selective laser sintering to co-enhance the bioactivity. On the one hand, the active elements silicon and calcium released respectively by the degradation of SBA15 and nHA were favorable for stimulating cell response. On the other hand, the hydrated silica gel layer derived from SBA15 could adsorb calcium ions released from nHA, thereby co-promoting apatite nucleation and growth. The experimental results showed that the formation of bone-like apatite on the scaffold was accelerated under simulated body fluid, indicating a good biomineralization capacity. Moreover, the scaffold demonstrated a good cell response in promoting the attachment of cell and the expression of alkaline phosphatase activity. Besides, SBA15 and nHA not only improved the hydrophilicity of the scaffold (the water contact angle changed from 107.4° to 57.8°), but also retarded the pH reduction by neutralizing the acidic hydrolysate of PLLA. These results indicated that the PLLA-SBA15-nHA scaffold may be potential candidates for bone repair.

Synthesis of lithium superionic conductor by growth of a nanoglass within mesoporous silica SBA-15 template

Nanodimensional silica based glasses containing alkali ions have recently been grown using suitable templates. These have shown electrical properties drastically different from those of their bulk counterpart. We have synthesized silicophosphate glasses having lithium ions with concentrations of 15–35 mole% Li2O within mesoporous silica SBA-15 (Santa Barbara amorphous-15) comprising of pores of diameter ~5 nm. The nanoglasses are characterized by electrical conductivities 5–6 orders of magnitude higher than those of the corresponding bulk glasses. These properties are attributed to the presence of a larger free volume in the nanoglasses as compared to their bulk states. The nanocomposites with 35 mole% Li2O exhibit an electrical conductivity of ~3 10−4 S · cm−1 at around room temperature. The activation energy for Li+ ion migration has been estimated from the conductivity-temperature variation to be 0.078 eV. These nanocomposites are believed to be ideally suited for the fabrication of solid state lithium ion batteries. We have also explored the efficiency of silicophosphate glass powders as possible electrode materials. Glass of composition 70SiO2/30P2O5 was prepared by using Pluronic P-123 tri-block copolymer along with suitable precursor sols. Cyclic voltammetric and galvanostatic charge/discharge measurements were carried out on the samples prepared in combination with suitable conductive fillers using a two-electrode system. These exhibited a high specific capacitance of 356 F g−1 making them ideally suitable as electrode materials for making a lithium ion solid state battery system.

Supersaturable solid self-microemulsifying drug delivery system: precipitation inhibition and bioavailability enhancement.

Solid self-emulsifying drug delivery system (SSEDDS), which incorporates liquid SEDDS into a solid dosage form, has been recently introduced to improve the oral bioavail-ability of poorly water-soluble drugs. However, supersaturated drug generated by SSEDDS is thermodynamically unstable and tends to precipitate rapidly prior to absorption, resulting in compromised bioavailability. The aim of this study was to construct a novel supersaturated SSEDDS (super-SSEDDS) by combining SSEDDS with appropriate precipitation inhibitor. Fenofibrate (FNB), a sparingly soluble drug, was selected as a model drug in this study. An optimized SSEDDS was prepared by solvent evaporation by using mesoporous silica Santa Barbara Amorphous-15 as the inert carrier. Supersaturation assay was conducted to evaluate the precipitation inhibition capacity of different polymers, and the results showed that Soluplus® could retard the FNB precipitation more effectively and sustain a higher apparent concentration for ~120 min. This effect was also clearly observed in the dissolution profiles of FNB from SSEDDS under supersaturated condition. The study of the mechanism suggested that the inhibition effect might be achieved both thermodynamically and kinetically. The area under the concentration–time curve of the super-SSEDDS was 1.4-fold greater than that of SSEDDS in the absence of Soluplus, based on an in vivo pharmacokinetic study conducted in beagle dogs. This study has demonstrated that the approach of combining SSEDDS with Soluplus as a supersaturation stabilizer constitutes a potential tool to improve the absorption of poorly water-soluble drugs.

Multifunctionalized mesoporous silica as an efficient reversed-phase/anion exchange mixed-mode sorbent for solid-phase extraction of four acidic nonsteroidal anti-inflammatory drugs in environmental water samples

A mesoporous silica Santa Barbara Amorphous-15 (SBA-15) has been first functionalized with 3-[2-(2-aminoethylamino)ethylamino]propyl-trimethoxysilane (a silane with three amines) and then reacted with an excess of phenyl glycidyl ether to generate a mixed-mode anion-exchanger containing both anion-exchange (three amines) and reversed-phase (multiple ether-linked phenyls) functionalities in a single branched ligand. The resulting material has been characterized by scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption measurements, Fourier-transform infrared spectroscopy, and elemental analysis. The results obtained indicated a BET specific surface area (SBET) of 362.5m2g−1, a pore volume of 0.70cm3g−1 with a narrow pore size distribution centered at 6.6nm, and carbon and nitrogen contents of 28.30% and 2.84%, respectively. The dimensions of these particles (∼5μm diameter, ∼60μm length), their large surface areas, their high-density functionalities and anion-exchange mixed-mode characteristics make them very attractive for highly effective solid phase extraction (SPE) of acidic nonsteroidal anti-inflammatory drugs (NSAIDs). The important parameters on extraction efficiency including sample pH, breakthrough volume, type and volume of eluent were optimized. A simple and sensitive analytical method based on mixed-mode SPE coupled to high-performance liquid chromatography with ultraviolet detection (HPLC-UV) was developed and successfully applied to the analysis of four NSAIDs (ketoprofen, naproxen, diclofenac, and ibuprofen) in spiked real water samples with satisfactory recoveries (80.6–110.9%) and repeatability (relative standard deviation <11.3%, n=3). The limit of detections of four NSAIDs were 0.006–0.070μgL−1 for tap water, and 0.014–0.16μgL−1 for river water and wastewater, with the enrichment factors of 806–1109-fold.

Enhancing in vitro dissolution and in vivo bioavailability of fenofibrate by solid self-emulsifying matrix combined with SBA-15 mesoporous silica

Mesoporous silica Santa Barbara amorphous-15 (SBA-15), derived from supermolecular assemblies of surfactant Pluronic® P123 with well-ordered 2-D hexagonal pores, was investigated as a reservoir to construct a novel solid self-emulsifying matrix for enhancing the oral bioavailability of fenofibrate (FNB). The emulsification rate and droplet size of a liquid self-emulsifying delivery system (SEDDS) were analyzed for optimization. SBA-15 was then added to the ethanol solution containing liquid SEDDS, and the obtained suspension changed into solid SEDDS matrix via solvent evaporation. The characterizations by SEM and XRD revealed that the solid matrix consisted of particles with smooth surface and FNB was completely transformed into molecular or amorphous state in the formulation. When introduced to aqueous media under gentle agitation, the solid matrix exhibited excellent self-emulsification properties and formed a uniform microemulsion with mean diameter of 117.35±2.33nm. The solid SEDDS matrix showed faster in vitro release rate than the raw powder and commercial capsule. The absorption of FNB delivered by solid SEDDS matrix was significantly improved in beagle dogs, and its Cmax and AUC values were about 8- and 4-fold greater than those of commercial products, respectively. In conclusion, SBA-15 emerged as a promising reservoir for SEDDS to enhance the bioavailability of poorly water-soluble drugs, which may provide a new strategy for advanced therapies.

Adsorption of strontium from aqueous solution by silica mesoporous SBA-15

The removal of 90Sr in liquid radioactive wastes is an important issue for waste disposal. In this paper, mesoporous silica SBA-15 (Santa Barbara amorphous 15) was employed to be a new sorbent for the sorption of Sr(II) from aqueous solution under different experimental conditions. Results showed that Sr(II) sorption with SBA-15 is fast with the equilibrium time within 100 min. The sorption is pH-dependent and good adsorption is at a relatively high pH and low ionic strength. Results suggest that SBA-15 is a potential sorbent for fast and efficient removal of Sr(II) from Sr-contaminated waste water.

CO2 adsorption on Santa Barbara Amorphous-15 (SBA-15) and amine-modified Santa Barbara Amorphous-15 (SBA-15) with and without controlled microporosity

Mesoporous silica SBA-15 samples with and without controlled framework microporosity were prepared and used directly or impregnated with polymer amine as adsorbent for CO2. These samples were evaluated for their ability to adsorb CO2 by obtaining their equilibrium adsorption isotherms using volumetric adsorption at three different temperatures of 273K, 278K and 283K. The data obtained were analyzed using Freundlich adsorption isotherm model while the isosteric heats of adsorption were estimated by the Clausius–Clapeyron equation. Under comparable conditions, the adsorption performance of silica SBA-15 was found to be strongly dependent upon the framework microporosity. However, the microporosity contribution to CO2 adsorption in amine-modified SBA-15 was not obvious as amine blocked micropores and dominated CO2 adsorption. The SBA-15 sample with higher microporosity displayed higher CO2 uptake and the CO2 uptake by amine-modified SBA-15 samples correlated with their total surface areas, as expected. These findings revealed the importance of surface area in designing an adsorbent for CO2.

Grafting of lignin onto nanostructured silica SBA-15: preparation and characterization

The slow decline in oil reserves with mounting oil prices is pushing industry to find more sustainable sources for industrial manufacturing. Lignin is the second most abundant natural renewable biopolymer that is underutilized and has many functional groups (–OH, phenolics) that make the biopolymer a convenient substrate for materials manufacturing by the industry. The present study thus describes grafting of lignin onto nanostructured silica SBA-15 (Santa Barbara amorphous 15) by first silylating lignin with triethoxychlorosilane followed by treatment of silylated lignin with SBA-15. The resulting nanocomposite denoted as LIG–SBA-15-G was then characterized by powder X-ray diffraction, infra-red (FTIR), 31P nuclear magnetic resonance (31P NMR), N2 adsorption (BET), scanning and transmission electron micrographs (SEM and TEM) and thermogravimetric analysis (TGA). X-ray data showed that LIG–SBA-15-G exhibited hexagonal structure closely similar to that observed for the SBA-15 host. FTIR of LIG–SBA-15-G showed characteristic absorption bands from lignin and attenuated Si–OH band due to its conversion to Si–O–Si ether bonds. Whereas, 31P NMR revealed that the majority of hydroxyl groups in lignin were replaced by Si–O–LIG ether bonds in LIG–SBA-15-G. SEM images of LIG–SBA-15-G displayed little changes in the macroscopic structure as compared to SBA-15. TEM images showed some disordered area in LIG–SBA-15-G and the grafted lignin appeared as black film on the silica surface. Using BET analysis the surface area of LIG–SBA-15-G was found to be 560 m2 g−1. Finally, TGA showed that LIG–SBA-15-G was more thermally stable than lignin and contained 13 % w/w lignin. Understanding the physicochemical and structural properties of the resulting lignin-nanosilica hybrid material should help engineer a robust and sustainable biomaterial suitable for various application, e.g. removal of contaminants from contaminated water.