Nanoporous Silica Research Articles

Polyethylene in Dead-End Silica Nanopores: Forces and Mobility from Non-Equilibrium Statistical Mechanics and Exchange Spectroscopy Nuclear Magnetic Resonance

Polyethylene in Dead-End Silica Nanopores: Forces and Mobility from Non-Equilibrium Statistical Mechanics and Exchange Spectroscopy Nuclear Magnetic Resonance

Surface Interactions and Nanoconfinement of Methane and Methane plus CO2 Revealed by High-Pressure Magic Angle Spinning NMR Spectroscopy and Molecular Dynamics.

This study explores the fundamental, molecular- to microscopic-level behavior of methane gas confined into nanoporous silica proxies with different pore diameters and surface-to-volume (S/V) ratios. Surfaces and pore walls of nanoporous silica matrices are decorated with hydroxyl (-OH) groups, resembling natural heterogeneity. High-pressure MAS NMR was utilized to characterize the interactions between methane and the engineered nanoporous silica proxies under various temperature and pressure regimes. There was a change in the chemical shift position of confined methane slightly in the mixtures with nanoporous silica up to 393 K, as shown by high-pressure 13C-NMR. The 13C-NMR chemical shift of methane was changed by pressure, explained by the densification of methane inside the nanoporous silica materials. The influence of pore diameter and S/V of the nanoporous silica materials on the behaviors and dynamics of methane were studied. The presence of CO2 in mixtures of silica and methane needs analysis with caution because CO2 in a supercritical state and gaseous CO2 change the original structure of nanoporous silica and change surface area and pore volume. According to simulation, the picosecond scale dynamics of methane confined in larger pores of amorphous silica is faster. In the 4 nm pore, the diffusivity obtained from MD simulations in the pore with a higher S/V ratio is slower due to the trapping of methane molecules in adsorbed layers close to the corrugated pore surface. In contrast, relaxation measured with NMR for smaller pores (higher S/V) exhibits larger T1, indicating slower relaxation.

Effect of Binding Linkers on the Efficiency and Metabolite Profile of Biomimetic Reactions Catalyzed by Immobilized Metalloporphyrin.

The investigation of liver-related metabolic stability of a drug candidate is a widely used key strategy in early-stage drug discovery. Metalloporphyrin-based biomimetic catalysts are good and well-described models of the function of CyP450 in hepatocytes. In this research, the immobilization of an iron porphyrin was performed on nanoporous silica particles via ionic interactions. The effect of the metalloporphyrin binding linkers was investigated on the catalytic efficiency and the metabolic profile of chloroquine as a model drug. The length of the amino-substituted linkers affects the chloroquine conversion as well as the ratio of human major and minor metabolites. While testing the immobilized catalysts in the continuous-flow reactor, results showed that the presented biomimetic system could be a promising alternative for the early-stage investigation of drug metabolites regarding analytical or synthetic goals as well.

Dynamic NMR Relaxometry as a Simple Tool for Measuring Liquid Transfers and Characterizing Surface and Structure Evolution in Porous Media.

Porous media containing voids which can be filled with gas and/or liquids are ubiquitous in our everyday life: soils, wood, bricks, concrete, sponges, and textiles. It is of major interest to identify how a liquid, pushing another fluid or transporting particles, ions, or nutriments, can penetrate or be extracted from the porous medium. High-resolution X-ray microtomography, neutron imaging, and magnetic resonance imaging are techniques allowing us to obtain, in a nondestructive way, a view of the internal processes in nontransparent porous media. Here we review the possibilities of a simple though powerful technique which provides various direct quantitative information on the liquid distribution inside the porous structure and its variations over time due to fluid transport and/or phase changes. It relies on the analysis of the details of the NMR (nuclear magnetic resonance) relaxation of the proton spins of the liquid molecules and its evolution during some process such as the imbibition, drying, or phase change of the sample. This rather cheap technique then allows us to distinguish how the liquid is distributed in the different pore sizes or pore types and how this evolves over time; since the NMR relaxation time depends on the fraction of time spent by the molecule along the solid surface, this technique can also be used to determine the specific surface of some pore classes in the material. The principles of the technique and its contribution to the physical understanding of the processes are illustrated through examples: imbibition, drying or fluid transfers in a nanoporous silica glass, large pores dispersed in a fine polymeric porous matrix, a pile of cellulose fibers partially saturated with bound water, a softwood, and a simple porous inclusion in a cement paste. We thus show the efficiency of the technique to quantify the transfers with a good temporal resolution.

Elucidation of Enhanced Lithium Conductivity in Nanoporous Ionogel Using Solid State NMR

AbstractNanostructured solid composite electrolyte or nano‐SCE, which is composed of an ionic liquid, nanoporous silica, and residuals of immobilized precursor components, shows promising synergistic properties. The ionic conductivity of nano‐SCE is in the range of 2–5 mS cm−1, which exceeds the bulk ionic liquid conductivity at ambient temperature, while maintaining characteristics of a solid electrolyte such as having no leakage issues as the ionic liquid is confined, and lower flammability compared to conventional liquid electrolytes. In this study, the underlying mechanism of enhanced conductivity is investigated by using magic angle spinning NMR and NMR relaxometry analysis. Water, one of the volatile precursor molecules has shown to play a key role in the final conductivity and stability at the solid‐electrolyte interface, as it enhances the temperature range in which the ionic liquid remains mobile. In line with previous studies, water with lowered mobility is found in the silicon matrix. The activation energies of lithium ion transfer probed by NMR relaxometry, however, do not change as function of water content. The increase in bulk mobility of lithium ions under ambient conditions compared to water‐less nano‐SCE is found to be the origin of the altered conductivity of this material.

Quest for optimal nanoconfinement for hydrate-based CO2 capture

CO2 capture is a viable solution for mitigating the global CO2 emission in the atmosphere. Hydrate-based CO2 capture is a promising technology. In this study, the CO2 hydrate formation thermodynamics and kinetics, along with the factors that influence CO2 capture in nanoporous silica gels (named S9, S26, and S77 with an average pore size of 9, 26 and 77 nm, respectively), with different degrees of nanoconfinement were investigated. The CO2 hydrate phase equilibrium and dissociation heat were determined by heat flow analysis. The heat flow curves revealed the formation of both confined- and bulk-phase hydrates in S9 and only bulk-phase hydrate in S26 and S77. The phase equilibrium temperature of the confined-phase hydrate was about 10 K lower than that of the bulk-phase hydrate and the dissociation heat of confined phase hydrate is 285.81 J/g in S9. According to the pressure curves, the CO2 hydrate formation time in S9 was 2–3.5 times longer than that in S26 and S77. Compared with dry silica gel, the supersaturated one was more conducive to CO2 capture. Under the same water saturation condition, the CO2 capture ability of S26 and S77 was stronger than that of S9, and the effect of water saturation was dominant over that of pressure. Thus, nanoconfinement in S9 has an adverse effect on hydrate-based CO2 capture whereas that in S26 and S77 is advantageous to it. This study provides an important fundamental basis for enhancing the hydrate-based CO2 capture ability via nanoconfinement in silica gel.

Molecular simulation studies on the water/methane two-phase flow in a cylindrical silica nanopore: Formation mechanisms of water lock and implications for gas hydrate exploitation

The water/gas two-phase flow is a frequently encountered question in the percolation field, and is especially important for the exploitation of natural gas hydrates because their decomposition products are exactly liquid water and natural gas. We studied the water/methane two-phase flow in a hydrophilic cylindrical nanopore by performing molecular simulations, and obtained high-quality nanoflows under different water saturation (Sw) thanks to the newly established nano-manometer method to control pressure difference accurately. With increasing Sw, the methane flow decreases almost linearly until a sudden stop when Sw ≥ 0.52. The formation of the water lock accounting for this phenomenon is observed clearly, and the larger Sw, the earlier formation of the water lock as well as the longer water lock. Based on careful data analysis, a water lock model and its formation mechanism are newly proposed with two pieces of strong evidence — the continuous reduction of the surface area of the water/gas interface when the water lock forms and the existence of maximum thickness of water film for different Sw. Thus, the competition between the surface tension of the water/gas interface and the adsorption of the water/wall interface controls the development of the water lock. These findings are very helpful for understanding the two-phase percolation and optimizing the gas production and water removal schemes during hydrate exploitation. In addition, the nano-manometer can be widely used in other nanoflow simulations for measuring the local pressure accurately.

Nanoporous Silica–Alumina Films Fabricated on Silicon Photonic Chips for Selective Ammonia Sensing

Surface-modified nanoporous silica films offer attractive features for analyte-specific gas detection applications. Here we demonstrate the integration of highly porous silica–alumina films on silicon nanophotonic chips and their performance in selective NH3 detection. Prototype sensors with microporous as well as mesoporous silica films were assembled. The incorporation of aluminum in trace amount needed to generate acid sites was achieved during film deposition or using postsynthesis atomic layer deposition. Silicon photonic micro-ring resonators functionalized with both techniques demonstrated a selective response to NH3 relative to CO2. Furthermore, the response was rapid and reversible. The role of preadsorbed water vapor on the reversible nature of the sensor is also investigated. Experimental observations indicate that water vapor preadsorbed on the films leads to fast sensor recovery while maintaining selectivity toward NH3. This could be attributed to the relatively less strong and still selective binding of NH3 on protonated water molecules preadsorbed on the surface acid sites. The potential of modified nanoporous films for portable and low-cost NH3 sensing on optical chips demonstrated here can be exploited in health care as well as industrial applications.

Biohybrid Membrane Formation by Directed Insertion of Aquaporin into a Solid-State Nanopore.

Biohybrid nanopores combine the durability of solid-state nanopores with the precise structure and function of biological nanopores. Particular care must be taken to control how biological nanopores adapt to their surroundings once they come into contact with the solid-state nanopores. Two major challenges are to precisely control this adaptability under dynamic conditions and provide predesigned functionalities that can be manipulated for engineering applications. In this work, we report on the computational design of a distinctive class of biohybrid active membrane layers, built from the directed-insertion of an aquaporin-incorporated lipid nanodisc into a model alkyl-functionalized silica pore. We show that in an aqueous environment when a pressure difference exists between the two sides of the solid-state nanopore, the preferential interactions between the hydrocarbon tail of the lipid molecules that surround the aquaporin protein and the alkyl group functionalizing the interior surface of the silica nanopore enable the insertion of the aquaporin-incorporated lipid shell into the nanopore by forcing out the water molecules. The same preferential interactions are responsible for the structural stability of the inserted aquaporin-incorporated lipid shell as well as the water sealing properties of the lipid–alkyl interface. We further show that the aquaporin protein stabilized in the alkyl-functionalized silica nanopore preserves its biological structure and function in both pure and saline water, and, remarkably, its water permeability is equal to the one measured in the biological environment. The designed biohybrid membrane could pave the way for the development of durable transformative devices for water filtration.

Surface Modification of Magnetic Nanoporous Silica with Carbon Based Materials for Enhancing Organic Dye Removal

The issue of wastewater from the dyeing industry entering the environment has significantly impacted both humans and other species. The dye blocks the photosynthesis process of aquatic plants and causes oxygen depletion in the marine environment. The dye is difficult to remove from wastewater due to their aromatic chemical structure. When the dye enters to human body, it can cause cancer, cell damage, and life-threatening conditions. Different methods have been investigated to remove the dye such as precipitation, photocatalytic, ion exchange, and membrane filtration. Those methods were difficult to apply on wide scale due to either their high cost or low efficiency. Adsorption is still an economical and effective method due to the cheap production cost and the reusability of the materials.Nanomaterials have great promises in improving many issues related to energy, catalysis, biomaterials, sensing applications and designing novel adsorbent materials [1-31]. Nanosize adsorbent materials have been utilized and great affinity for removing inorganic and organic species.In this study, we develop a new method of modifying and activating the magnetic zeolite Y, as a nanoporous adsorbent by utilizing cetyltrimethyl ammonium bromide (CTAB). We applied mechanochemical synthesis method to combine CTAB with magnetic zeolite Y. The composite was applied to adsorb methylene blue. The adsorbing efficiency was monitored by UV-Vis spectrophotometer. The study showed that at 500 mg/L, the composite adsorbed 12% of methylene blue. At 1000 mg/L and 5000 mg/L, the composite adsorbed 71% and 100% of methylene blue, respectively. References ME Mahmoud, MA Khalifa, YM El Wakeel, MS Header, TM Abdel-Fattah, Journal of Nuclear Materials 487, 13-22 (2017)C Huff, T Dushatinski, TM Abdel-Fattah, International Journal of Hydrogen Energy 42 (30), 18985-18990 (2017)M Stacey, C Osgood, BS Kalluri, W Cao, H Elsayed-Ali, T Abdel-Fattah, Biomedical Materials 6 (1), 011002 (2011)SE Mohmed Labeb, Abdel-Hamed Sakr, Moataz Soliman, Tarek M.Abdel-Fattah, Optical Materials 79, 331-335 (2018)ME Mahmoud, MM Osman, SB Ahmed, TM Abdel-Fattah, Chemical engineering journal 175, 84-94 (2011)TM Abdel-Fattah, ME Mahmoud, Chemical engineering journal 172 (1), 177-183 (2011)R Bhure, TM Abdel-Fattah, C Bonner, JC Hall, A Mahapatro, Journal of biomedical nanotechnology 6 (2), 117-128 (2010)TM Abdel-Fattah, D Loftis, A Mahapatro, Journal of biomedical nanotechnology 7 (6), 794-800 (2011)OH Elsayed-Ali, T Abdel-Fattah, HE Elsayed-Ali, Journal of hazardous materials 185 (2-3), 1550-1557 (2011)R Bhure, A Mahapatro, C Bonner, TM Abdel-Fattah, Materials Science and Engineering: C 33 (4), 2050-2058 (2013)BE Bishop, BA Savitzky, T Abdel-Fattah, Ecotoxicology and Environmental Safety 73 (4), 565-571 (2010)C Huff, JM Long, A Heyman, TM Abdel-Fattah, ACS Applied Energy Materials 1 (9), 4635-4640 (2018)TM Abdel-Fattah, EM Younes, G Namkoong, EM El-Maghraby, Synthetic Metals 209, 348-354 (2015)S Ebrahim, M Soliman, TM Abdel-Fattah, Journal of electronic materials 40 (9), 2033-2041 (2011)SH Lapidus, A Naik, A Wixtrom, NE Massa, V Ta Phuoc, L del Campo, Crystal growth & design 14 (1), 91-100 (2014)A Mahapatro, TD Matos Negrón, C Bonner, TM Abdel-Fattah, Journal of Biomaterials and Tissue Engineering 3 (2), 196-204 (2013)S Ebrahim, M Labeb, T Abdel-Fattah, M Soliman, Journal of Luminescence 182, 154-159 (2017)T Dushatinski, C Huff, TM Abdel-Fattah, Applied Surface Science 385, 282-288 (2016)ME Mahmoud, SS Haggag, MA Rafea, TM Abdel-Fattah, Polyhedron 28 (16), 3407-3414 (2009)C Huff, JM Long, A Aboulatta, A Heyman, TM Abdel-Fattah, ECS Journal of Solid State Science and Technology 6 (10), M115 (2017)A Wixtrom, J Buhler, T Abdel-Fattah, Journal of Chemical Education 91 (8), 1232-1235 (2014)ME Mahmoud, SS Haggag, TM Abdel-Fattah, Polyhedron 26 (14), 3956-3962 (2007)TM Abdel-Fattah, ME Mahmoud, MM Osmam, SB Ahmed, Journal of Environmental Science and health, part A 49 (9), 1064-1076 (2014)ME Mahmoud, TM Abdel-Fattah, MM Osman, SB Ahmed, Journal of Environmental Science and Health, Part A 47 (1), 130-141 (2012)C Huff, E Biehler, Q Quach, JM Long, TM Abdel-Fattah, Colloids and Surfaces A: Physicochemical and Engineering Aspects 610 (5), 125734 (2021)K Foe, G Namkoong, TM Abdel-Fattah, H Baumgart, MS Jeong, DS Lee, Thin solid films 534, 76-82 (2013)M Abdel-Fattah, A Wixtrom, K Zhang, W Cao, H Baumgart, ECS Journal of Solid State Science and Technology 3 (10), M61 (2014)C Huff, T Dushatinski, A Barzanji, N Abdel-Fattah, K Barzanji, ECS Journal of Solid State Science and Technology 6 (5), M69 (2017)TM Abdel-Fattah, B Bishop, Journal of Environmental Science and Health, Part A 39 (11-12), 2855-2866 (2014)Quach, E. Biehler, A. Elzamzami, C. Huff, J.M. Long, T.M. Abdel Fattah, Catalysts, 11, 118 (2021).E. Biehler, Q. Quach, C. Huff, T. M. Abdel-Fattah, Materials, 15, 2692 (2022).

Diffusio-osmosis of oil–CO2 mixture in inorganic nanopores

Diffusio-osmosis is the interfacial transport induced by solute density gradient and plays an essential role in many micro/nanofluidic systems. Here, we report the molecular dynamics simulations of the diffusio-osmosis of oil–CO2 mixture in silica and calcite nanopores. We show that, under the high solute (CO2) density considered, although the enrichment of CO2 near calcite walls is substantially higher than that near silica walls, the diffusio-osmosis in calcite pores is only marginally stronger. This phenomenon is attributed to the significantly different molecular structures and hydrodynamic properties of interfacial fluids in the two pores caused by the CO2 adsorption on their walls, which is in turn traced to the different physical chemistry of the silica and calcite walls. Using continuum simulations parameterized by the diffusio-osmosis characteristics obtained in our molecular modeling, we show that, for the oil transport through slit pores driven by pressurized CO2, the diffusio-osmosis becomes important compared to the Poiseuille flow when the pore width decreases below a few tens of nanometers and its significance compared to the Poiseuille flow increases quadratically as the pore width decreases.

Deliquescence of NaCl Confined in Nanoporous Silica.

The deliquescence behavior of salt nanocrystals is different from that of bulk crystals. Here, we report the first systematic measurements of the deliquescence relative humidity (DRH) of sodium chloride crystals confined in various nanoporous silica materials with pore diameters ranging from 8 to 89 nm. Deliquescence humidities were determined by water vapor sorption measurements. In comparison to the DRH of bulk NaCl crystals (75.3% RH), the DRH decreases from 73 to 58% as the pore size decreases from 89 to 8 nm. In contrast, according to literature data, the DRH of NaCl aerosol nanoparticles increases with decreasing crystal size. A thermodynamic model approach, based on the combined use of an ion-interaction model, the Laplace equation, and the Kelvin equation, is used to calculate the influence of the confinement in nanopores on the solid-liquid and liquid-vapor phase equilibria. These calculations reveal that the main reason for the decrease in the DRH in nanopores is the concave curvature of the liquid-vapor interface that is formed during deliquescence. The same model approach shows that the increase in DRH of nanosized aerosol particles is due to the convex curvature of the liquid-vapor interface, whereas the effect of increases in solubility with decreasing crystal size is small.

Weak Coordinating Character of Organosulfonates in Oriented Silica Films: An Efficient Approach for Immobilizing Cationic Metal-Transition Complexes.

Iron (II) tris(2,2′-bipyridine) complexes, [Fe(bpy)3]2+, have been synthesized and immobilized in organosulfonate-functionalized nanostructured silica thin films taking advantage of the stabilization of [Fe(H2O)6]2+ species by hydrogen bonds to the anionic sulfonate moieties grafted to the silica nanopores. In a first step, thiol-based silica films have been electrochemically generated on indium tin oxide (ITO) substrates by co-condensation of 3-mercaptopropyltrimethoxysilane (MPTMS) and tetraethoxysilane (TEOS). Secondly, the thiol function has been modified to sulfonate by chemical oxidation using hydrogen peroxide in acidic medium as an oxidizing agent. The immobilization of [Fe(bpy)3]2+ complexes has been performed in situ in two consecutive steps: (i) impregnation of the sulfonate functionalized silica films in an aqueous solution of iron (II) sulfate heptahydrate; (ii) dipping of the iron-containing mesostructures in a solution of bipyridine ligands in acetonitrile. The in situ formation of the [Fe(bpy)3]2+ complex is evidenced by its characteristic optical absorption spectrum, and elemental composition analysis using X-ray photoelectron spectroscopy. The measured optical and electrochemical properties of immobilized [Fe(bpy)3]2+ complexes are not altered by confinement in the nanostructured silica thin film.

Confinement-Driven Heterogeneous Benzene Crystallization in Silica Nanopores

Nanoconfinement alters the thermodynamics, dynamics, and kinetics of fluids hosted in nanoscale solid nanopores to an extent that depends on the characteristics of the confining space and the chemistry of the confined fluids. Confinement-induced alterations in the phase behavior of confined energetic fluids under high pressure or low temperature are highly relevant to subsurface and subsea phenomena such as fluid flow in porous media, hydrate formation and dissociation, and gas storage capacity. Although extensive efforts have been directed toward understanding the phase behavior of confined fluids, the role of solid–liquid interfaces in the phase transitions of organic liquids has not been resolved yet. In this study, we explore the onset and growth of benzene crystallization confined in 6 nm sized SBA-15 silica nanopores in the temperature range 300–200 K using in situ extended range small-angle and wide-angle X-ray scattering (SAXS/WAXS) measurements and atomistic classical molecular dynamics (MD) simulations. The crystallization onset of confined benzene depresses to 265 K compared to the freezing point of bulk benzene (∼278 K), followed by the continuous growth of the emerged crystals in the pore space with complete crystallization at 200 K. The orientation of the emerged benzene crystals is dominated by parallel (π–π stacking) and perpendicular (T-shape stacking) orientations along the cylindrical pore radius and pore length, respectively. The onset of benzene crystals occurs heterogeneously on the pore surface and grows continuously toward the pore center. Further, confined benzene undergoes a dynamical crossover from fragile to strong dynamics behavior, inferred from the rotational and translational diffusion. The insights provided by this study have significant implications for the phase transitions of confined organic liquids that are relevant to a wide range of applications in the biological, geological, environmental, and chemical fields.

Nanoporous silica gel can compete with the flower stigma in germinating and attracting pollen tubes.

To find nanoporous substrates with hydrodynamic properties useful for pollen hydration and germination, we used the glassy Silica gel and Vycor scales and pollen with different morphological and physiological traits, that of Crocus vernus, and that of Narcissus poeticus. For in vitro tests, the scales were spread on microscope slides, hand pollinated, and incubated. Pollen germination was evaluated with the stereomicroscope and the tube growth was explored with scanning electron microscopy (SEM). The in vivo tests were carried out by sprinkling the stigmas of the Crocus plants with Silica gel scales and immediately after having pollinated them by hand, the plants were incubated. Three hours later, the stigmas were removed and treated for observation with SEM. In vitro the pollen of both species germinated on Silica gel with percentages similar to those of the in vivo and in vitro controls, accumulating fibrillary material at the interface. The tubes grew perpendicular to the surface of the scales, trying to penetrate the scales to the point of flattening with the apex. On Crocus stigmas sprinkled with Silica gel scales, pollen developed tubes that grew to the scales rather than penetrating the papillae. The results underline the close interaction of pollen with nanoporous artificial material, so much so that its pollen tubes are attracted to the Silica scales more than to the stigma papillae that arises from a mechanism of natural selection.

Local and diffusive dynamics of LiCl aqueous solutions in pristine and modified silica nanopores.

We use 1H, 2H, and 7Li nuclear magnetic resonance to investigate local and diffusive dynamics of LiCl-7H2O and LiCl-7D2O solutions in pristine and functionalized silica nanopores in a component-selective manner. Recently, we showed that the solution dynamics become slower when the diameter of the pristine pores is reduced. Here, we determine the effects of (aminopropyl)triethoxysilane and dye surface functionalizations on the motions of the water molecules and lithium ions from ambient temperatures down to the glass transition. The local and diffusive solution dynamics are similar in both functionalized pores but, on average, slower than in pristine pores with comparable diameters. When the exchange between different confinement regions is sufficiently slow at reduced temperatures, bimodal water and lithium dynamics may be observed. We attribute this bimodality to bulk-like motion in the pore centers and slowed-down motion at the pore walls. For the lithium ions, a bimodality observed in the pristine pores is absent in the functionalized ones. We conjecture that the steric hindrance and electrostatic interactions associated with the grafted functional groups interfere with the formation of a defined electric double layer, while the enhanced surface roughness and unequal charge distribution result in overall slower dynamics. Thus, the nature of the walls is an important parameter for the solution dynamics. Thereby, in situ measurements of the pH value inside the silica pores using the grafted dye molecules reveal that observed changes in the pH value in response to the surface functionalization are of limited relevance for the water reorientation.

Trithiocyanuric acid-functionalized nanoporous silica: synthesis and application as an Ag+ selective optical probe

Trithiocyanuric acid-functionalized nanoporous silica: synthesis and application as an Ag+ selective optical probe

Highly silver-selective fluorescent sensor based on functionalized nanoporous silica (SBA-Pr-NMP) in aqueous media

Highly silver-selective fluorescent sensor based on functionalized nanoporous silica (SBA-Pr-NMP) in aqueous media

Cultivation of Navicula sp. on rice straw hydrolysate for the production of biogenic silica

Rice straw hydrolysate (RSH) prepared at room temperature was found to be rich in silica (140 ± 4.1 mg L-1) and other nutrients (nitrate-N: 160 ± 4.3 mg L−1, total dissolve phosphate: 164 ± 6.7 mg L−1, ammoniacal-N: 439.8 ± 17 mg L−1). The aim of this work was to study four RSH dilutions (10, 30, 50, 70% v/v) to cultivate Navicula sp. with modified ASN-III as a control. The best result was achieved in 30% RSH in terms ofdoubling time (d = 1.49 days) and growth rate (µmax = 0.46 day−1). Compared to control, specific growth rate and biomass productivity were increased by 2.93 folds and 1.85 folds, respectively. Cultivation in 5 L reactor with optimized 30% RSH yielded frustule (54.2 ± 1.9%), carbohydrate (12.4 ± 1.2%), lipid (18.9 ± 1.4%), and protein (8.2 ± 0.6%). The residual solid fraction showed 18.99% increased theoretical methane yield than raw rice straw. Overall, the present process offers a sustainable solution to manage rice straw residue and recover nanoporous silica.

Enabling tandem oxidation of benzene to benzenediol over integrated neighboring V-Cu oxides in mesoporous silica

The direct tandem oxidation synthesis of benzenediol from benzene could simplify or even avoid the separation and purification of reaction intermediates, which is promising but challenged because of the further required immediate consecutive activation of intermediate phenol. In this work, a synergistic benzene tandem-oxidation catalyst that V-Cu bimetallic oxides modified nanoporous silica (VCu-NS) was constructed via a facile assembly strategy which involves addictive negative anion citric acid mediating the intercalation of metal-citric acid chelate in mesopore of silica and subsequent thermal calcination inducing dual-metal active site formation. Such a tactic could make amorphous VOx species well covered on the surface of mesopore, and ultrafine copper oxide particles surrounded and neighbored by highly dispersed VOx with strong interplay in mesopore, which was comprehensively confirmed by various characterizations. Benefiting from the unique V-Cu neighboring effect, the desorption of formed phenol over the catalytic site might be restricted therefore easily further activated by the formed reactive oxidative species, 3VCu-NS shows synergetic tandem-oxidation catalytic activities for benzene towards benzenediol with a selectivity of 57%. The result allows optimal 3VCu-NS to be a promising catalyst for benzenediol synthesis from benzene.