Porous Silica Matrix Research Articles

Deposition of CdSe Nanocrystals in Highly Porous SiO2 Matrices-In Situ Growth vs. Infiltration Methods.

Embedding quantum dots into porous matrices is a very beneficial approach for generating hybrid nanostructures with unique properties. In this contribution we explore strategies to dope nanoporous SiO2 thin films made by atomic layer deposition and selective wet chemical etching with precise control over pore size with CdSe quantum dots. Two distinct strategies were employed for quantum dot deposition: in situ growth of CdSe nanocrystals within the porous matrix via successive ionic layer adsorption reaction, and infiltration of pre-synthesized quantum dots. To address the impact of pore size, layers with 10 nm and 30 nm maximum pore diameter were used as the matrix. Our results show that though small pores are potentially accessible for the in situ approach, this strategy lacks controllability over the nanocrystal quality and size distribution. To dope layers with high-quality quantum dots with well-defined size distribution and optical properties, infiltration of preformed quantum dots is much more promising. It was observed that due to higher pore volume, 30 nm porous silica shows higher loading after treatment than the 10 nm porous silica matrix. This can be related to a better accessibility of the pores with higher pore size. The amount of infiltrated quantum dots can be influenced via drop-casting of additional solvents on a pre-drop-casted porous matrix as well as via varying the soaking time of a porous matrix in a quantum dot solution. Luminescent quantum dots deposited via this strategy keep their luminescent properties, and the resulting thin films with immobilized quantum dots are suited for integration into optoelectronic devices.

Revealing nanoscale sorption mechanisms of gases in a highly porous silica aerogel.

Geological formations provide a promising environment for the long-term and short-term storage of gases, including carbon dioxide, hydrogen and hydro-carbons, controlled by the rock-specific small-scale pore structure. This study investigates the nanoscale structure and gas uptake in a highly porous silica aerogel (a synthetic proxy for natural rocks) using transmission electron microscopy, X-ray diffraction, and small-angle and ultra-small-angle neutron scattering with a tracer of deuterated methane (CD4) at pressures up to 1000 bar. The results show that the adsorption of CD4 in the porous silica matrix is scale dependent. The pore space of the silica aerogel is fully accessible to the invading gas, which quickly equilibrates with the external pressure and shows no condensation on the sub-nanometre scale. In the 2.5-50 nm pore size region a classical two-phase adsorption behaviour is observed. The structure of the aerogel returns to its original state after the CD4 pressure has been released.

Ordered Mesoporous Silica Delivering siRNA as Cancer Nanotherapeutics: A Comprehensive Review.

Nanosized mesoporous silica has emerged as a promising flexible platform delivering siRNA for cancer treatment. This ordered mesoporous nanosized silica provides attractive features of well-defined and tunable porosity, structure, high payload, and multiple functionalizations for targeted delivery and increasing biocompatibility over other polymeric nanocarriers. Moreover, it also overcomes the lacunae associated with traditional administration of drugs. Chemically modified porous silica matrix efficiently entraps siRNA molecules and prevents their enzymatic degradation and premature release. This Review discusses the synthesis of silica using the sol-gel approach and the advantages with different silica mesostructure. Herein, the factors affecting the synthesis of silica at nanometer scale, shape, porosity and nanoparticle surface modification are also highlighted to attain the desired nanostructured silica carriers. Additional emphasis is given to chemically modified silica delivering siRNA, where the silica nanoparticle surface was modified with different chemical moieties such as amine modified with (3-aminoropyl) triethoxysilane, polyethylenimine, chitosan, poly(ethylene glycol), and cyclodextrin polymer modification to attain high therapeutic loading, improved dispersibility and biocompatibility. Upon systemic administration, ordered mesoporous nanosized silica encounters blood cells, immune cells, and organs mainly of the reticuloendothelial system (RES). Thereby, biocompatibility and biodistribution of silica based nanocarriers are deliberated to design principles for smart and efficacious nanostructured silica-siRNA carriers and their clinical trial status. This Review further reports the future scopes and challenges for developing silica nanomaterial as a promising siRNA delivery vehicle demanding FDA approval.

Remarkable enhancement of cinnamaldehyde antimicrobial activity encapsulated in capped mesoporous nanoparticles: A new “nanokiller” approach in the era of antimicrobial resistance

Combating antimicrobial resistance is one of the biggest health challenges because of the ineffectiveness of standard biocide treatments. This challenge could be approached using natural products, which have demonstrated powerful therapeutics against multidrug-resistant microbes. In the present work, a nanodevice consisting of mesoporous silica nanoparticles loaded with an essential oil component (cinnamaldehyde) and functionalized with the polypeptide ε-poly-l-lysine is developed and used as an antimicrobial agent. In the presence of the corresponding stimuli (i.e., exogenous proteolytic enzymes from bacteria or fungi), the polypeptide is hydrolyzed, and the cinnamaldehyde delivery is enhanced. The nanodevice's release mechanism and efficacy are evaluated in vitro against the pathogenic microorganisms Escherichia coli, Staphylococcus aureus, and Candida albicans. The results demonstrate that the new device increases the delivery of the cinnamaldehyde via a biocontrolled uncapping mechanism triggered by proteolytic enzymes. Moreover, the nanodevice notably improves the antimicrobial efficacy of cinnamaldehyde when compared to the free compound, ca. 52-fold for E. coli, ca. 60-fold for S. aureus, and ca. 7-fold for C. albicans. The enhancement of the antimicrobial activity of the essential oil component is attributed to the decrease of its volatility due to its encapsulation in the porous silica matrix and the increase of its local concentration when released due to the presence of microorganisms.

Enhanced morphological maintenance and redox stability by dispersing nickel ferrite into silica matrix for chemical looping hydrogen production via water splitting

Chemical looping hydrogen production (CLHP) is widely regarded as a clean and efficient route for high purity hydrogen production. However, a huge barrier is how to avoid serious deactivation caused by sintering and agglomeration of oxygen carriers. A novel fabrication process of highly dispersing NiFe2O4 into silica matrix is proposed. The oxygen carriers of NiFe2O4 completely dispersed over silica matrix (NFSM) are successfully synthesized. The characterizations, hydrogen production capacity and cycle redox performance of oxygen carriers are further investigated. The results illustrate that NiFe2O4 active components are homogeneously dispersed on the silica matrix without any impurities. NFSM demonstrates the highest reactivity with CO as well as the greatest hydrogen production of 296 mL/g due to the strong confinement effect of silica matrix and good particle dispersion. The porous silica matrix offers large amounts of channels for the lattice oxygen transport and effectively prevents Fe and Ni cations outward migration to particle surface, which actually inhibits the larger clusters and sintering. NFSM can keep stable hydrogen production of approximately 290 mL/g during the cyclic experiments. Briefly, the innovation method of embedding active component into well-established silica matrix supports contributes to the enhanced anti-sintering properties and redox stability of oxygen carriers.

Tannic Acid as a Versatile Template for Silica Monoliths Engineering with Catalytic Gold and Silver Nanoparticles.

Tannic acid in alkaline solutions in which sol-gel synthesis is usually performed with tetraethoxysilane is susceptible to various modifications, including formation of reactive radicals, oxidation under the action of atmospheric oxygen, self-association, and self-polymerization. Here, a precursor with ethylene glycol residues instead of ethanol was used, which made it possible to synthesize bionanocomposites of tannic acid and silica in one stage in neutral media under normal conditions without the addition of acid/alkali and organic solvents. Silica was fabricated in the form of optically transparent monoliths of various shapes with 2-4 nm pores, the radius of which well correlated with the size of a tannic acid macromolecule in a non-aggregated state. Polyphenol, which was remained in pores of silica matrix, served then as reducing agent to synthesize in situ gold and silver nanoparticles. As shown, these Au@SiO2 and Ag@SiO2 nanocomposites possessed localized surface plasmon resonance and high catalytic activity.

Porous silica matrix as an efficient strategy to boosted photocatalytic performance of titania/carbon composite

Semiconductor based photocatalysis is considered as a promising route for remediation of polluted water. However, there is still intensive research to overcome high recombination rate of electrons and holes, and low reaction rate, limiting large-scale applications. Therefore, it is crucial to focus on the fabrication of the optimal photocatalysts which could be practically utilized. In this contribution, we propose a composite composed of ultrasmall TiO2 nanoparticles embedded in silica/carbon matrix. This molecular hybrid was fabricated via anchoring a (3-aminopropyl) triethoxysilane on a surface of TiO2 and then the composite was encapsulated in a carbon sphere-like structure formed with biocompatible glucose as carbon precursor. As a result, such a system exhibited impressive photocatalytic activity in the degradation of methylene blue as a model hazardous organic dye. Among examined catalysts, the sample calcinated at 500 °C showed the highest photocatalytic efficiency (~100% photodegradation under UV light after 120 min and ~11.0–fold higher reaction rate constant in comparison to pristine TiO2) and the most enhanced photocurrent response upon irradiation with light 388 nm (~0.74 μA, which is 1.37–fold more compared with TiO2). Therefore, we provide new insights into the fabrication of carbon-based inorganic composite, which have great potential in water treatment.

Nano Ag0 decorated-silica matrix for the remediation of environmental pollutants: Visible-light driven Cr(VI) photoreduction, photodegradation of organic dye, nanomolar Hg2+ detection, and antimicrobial applications

BackgroundWater contamination with toxic heavy metals and dye colorants causes a harmful effect on all living organisms and affect ecosystem adversely. In this study, nano-Ag0 decorated porous silica matrix conjugated with alanine was investigated for multifunctionality including mercury (Hg2+) detection, visible-light photocatalytic performance for organic dye degradation, Cr(VI) photoreduction and antibacterial activity. MethodHRTEM and XRD verified the anchoring of crystalline Ag0 on silica matrix with devoid of impure phases. SEM and XPS analysis was carried out before and after Hg2+ interaction with nano-Ag0/silica probe to understand the variation in morphology, interactions, chemical states, and intrinsic mechanism. Significant findingsThe LOD of the present probe for the detection of Hg2+ was 12 nM. The Ag0-silica NPs incorporated paper strip and agarose gel was prepared and used for mercury detection by the naked eye. The silica stabilized Ag particles form conjugate with alanine and when it interacts with Hg2+, mercury oxidizes the Ag(0) to Ag(I) by amalgam formation resulting in pale-yellow color changing to colorless. Environmental parameters such as salinity, pH and temperature did not influence Hg2+ detection. In addition, photocatalytic activity of nano-Ag0/silica was tested with cationic methylene blue (MB) dye under visible light irradiation that showed 90.3% degradation. Further, the nano-Ag0/silica exhibited significantly superior Cr(VI) photoreduction activity. In addition, gram positive and gram negative bacterial strains showed higher growth inhibition upon exposure to Ag0-silica NPs.

Magnetic Study of CuFe2O4-SiO2 Aerogel and Xerogel Nanocomposites.

CuFe2O4 is an example of ferrites whose physico-chemical properties can vary greatly at the nanoscale. Here, sol-gel techniques are used to produce CuFe2O4-SiO2 nanocomposites where copper ferrite nanocrystals are grown within a porous dielectric silica matrix. Nanocomposites in the form of both xerogels and aerogels with variable loadings of copper ferrite (5 wt%, 10 wt% and 15 wt%) were synthesized. Transmission electron microscopy and X-ray diffraction investigations showed the occurrence of CuFe2O4 nanoparticles with average crystal size ranging from a few nanometers up to around 9 nm, homogeneously distributed within the porous silica matrix, after thermal treatment of the samples at 900 °C. Evidence of some impurities of CuO and α-Fe2O3 was found in the aerogel samples with 10 wt% and 15 wt% loading. DC magnetometry was used to investigate the magnetic properties of these nanocomposites, as a function of the loading of copper ferrite and of the porosity characteristics. All the nanocomposites show a blocking temperature lower than RT and soft magnetic features at low temperature. The observed magnetic parameters are interpreted taking into account the occurrence of size and interaction effects in an ensemble of superparamagnetic nanoparticles distributed in a matrix. These results highlight how aerogel and xerogel matrices give rise to nanocomposites with different magnetic features and how the spatial distribution of the nanophase in the matrices modifies the final magnetic properties with respect to the case of conventional unsupported nanoparticles.

Interfacial Conductivity Enhancement and Pore Confinement Conductivity-Lowering Behavior inside the Nanopores of Solid Silica-gel Nanocomposite Electrolytes.

Solid nanocomposite electrolytes (nano-SCEs) that exhibit higher ionic conductivity than the individual confined electrolyte were investigated for high-performance solid-state batteries. Understanding the behavior of Li-ion conduction through the pores is important to design ideal nanoporous structures for nano-SCEs, which are composed of an ionic liquid electrolyte (ILE) in a highly porous (∼90%) silica matrix. To establish the relationship between the pore structure of the silica matrix and the ionic conductivity of the solid nanocomposite, the liquid electrolyte fraction was successfully extracted from the nano-SCE to reveal the fragile porous silica matrix. A careful drying using the CO2 supercritical drying method helps in sustaining the original structure, preventing its collapse due to surface tension. The pore size distribution, Brunauer-Emmett-Teller (BET) surface area, and porosity were characterized using scanning electron microscopy, transmission electron microscopy, and N2 adsorption/desorption techniques. Our results revealed a wide size distribution of macropores and mesopores in the silica matrix. The pore size increased and the effective surface area decreased with increasing ILE/SiO2 molar ratio. The interface conductivity enhancement was found to increase with the thickness of the adsorbed (ice-like) bound-water layer on the silica surface, confirming that the strong hydrogen bonding of the adsorbed ionic liquid molecules on the bound-water layer causes the conduction promotion effect in the nano-SCE. In addition, a large number of small pores lead to a severe pore confinement effect that results in a decreased conductivity due to the increasing viscosity of the ILE filling the pores. The conductivity can be improved by realizing a nano-SCE with an optimized pore size to minimize the pore confinement effect.

Disentangling Electron-Phonon Coupling and Thermal Expansion Effects in the Band Gap Renormalization of Perovskite Nanocrystals.

The complex electron-phonon interaction occurring in bulk lead halide perovskites gives rise to anomalous temperature dependences, like the widening of the electronic band gap as temperature increases. However, possible confinement effects on the electron-phonon coupling in the nanocrystalline version of these materials remain unexplored. Herein, we study the temperature (ranging from 80 K to ambient) and hydrostatic pressure (from atmospheric to 0.6 GPa) dependence of the photoluminescence of ligand-free methylammonium lead triiodide nanocrystals with controlled sizes embedded in a porous silica matrix. This analysis allowed us to disentangle the effects of thermal expansion and electron-phonon interaction. As the crystallite size decreases, the electron-phonon contribution to the gap renormalization gains in importance. We provide a plausible explanation for this observation in terms of quantum confinement effects, showing that neither thermal expansion nor electron-phonon coupling effects may be disregarded when analyzing the temperature dependence of the optoelectronic properties of perovskite lead halide nanocrystals.

Physical, Chemical, and Genetic Techniques for Diatom Frustule Modification: Applications in Nanotechnology

Diatom frustules represent one of the most complex examples of micro- and nano-structured materials found in nature, being the result of a biomineralization process refined through tens of milions of years of evolution. They are constituted by an intricate, ordered porous silica matrix which recently found several applications in optoelectronics, sensing, solar light harvesting, filtering, and drug delivery, to name a few. The possibility to modify the composition and the structure of frustules can further broaden the range of potential applications, adding new functions and active features to the material. In the present work the most remarkable physical and chemical techniques aimed at frustule modification are reviewed, also examining the most recent genetic techniques developed for its controlled morphological mutation.

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.

In-situ incorporation of ruthenium/copper nanoparticles in mesoporous silica derived from rice husk ash for catalytic acetylation of glycerol

Abstract Ruthenium and copper nanoparticles were incorporated into MCM-41-like mesoporous silica via a fast sol-gel method at 80 °C using rice husk ash (RHA) as the silica source. The physico-chemical characterization of the synthesized materials was carried out using various analytical techniques. The X-ray diffraction results indicated that the mesoporous silica synthesized in this study had the standard MCM-41 structure. The Fourier transform infrared spectroscopy results showed that ruthenium and copper ions were successfully incorporated into the hexagonal framework of the mesoporous materials. The transmission electron microscopy results revealed that the RHA-MCM-41, MCM-41-10Ru, and MCM-41-10Ru10Cu samples consisted of ordered mesoporous straight channels. MCM-41-10Cu consisted of copper nanospheres. MCM-41-10Ru and MCM-41-10Ru10Cu showed ruthenium nanoparticle agglomerates distributed on their external MCM-41 framework surfaces. In the case of MCM-41-10Cu and MCM-41-10Ru10Cu, copper ions were homogeneously dispersed on the internal surface of the agglomerated porous silica matrix. The as-prepared Ru- and Cu-doped MCM-41 catalyst was used for the acetylation of glycerol. The catalyst showed a high conversion of 98% and high shape selectivity towards the formation of diacetin and triacetin unlike conventional silica-based catalysts, which show selectivity towards the formation of monoacetin.

Sintered porous glasses hosting luminescent species of different nature: Eu3+ ions and Tb3+-doped Ba2TiSi2O8 glass-ceramic powder

We report on the employment of a nano-porous Vycor-type glass as host for two luminescent substances of very different physical and chemical nature, which share the same porous space. Firstly, BTS:Tb3+ glass-ceramic nano-powders were infiltrated in the porous structure and secondly Eu3+ ions from a nitrate aqueous solution were included afterwards. Upon sintering, the porous silica matrix collapses, embedding both luminescent species. We focused on the micro and nano-structure of the sintered glasses. Upon sintering a europium silicate phase crystallizes as monocrystalline hexagonal nano-rods, which coexist with amorphous round particles below 100 nm enriched in Eu and Si. Both kinds of particles are embedded in a cristobalite matrix. The interesting microstructure is reported for the first time. The sintering heating rate influences the microstructure after the sintering. The microstructure was investigated by a last generation TEM microscope with aberration correction, EDXS and an exhaustive electron diffraction analysis. The inclusion of BTS:Tb3+ is only limited, and thus, the its role in the optical properties of the final material is negligible. Luminescence upon UV excitation shows the characteristic emission peaks of Eu3+. This work highlights the possibility of combining several luminescent materials inside a silica matrix.

Pore Structure Analysis of Silica-Gel Solid Nanocomposite Electrolytes with Surface Conduction Enhancement

Solid-state batteries are considered to reach the high energy densities needed for our emerging sustainable energy society. Recently, solid electrolytes (SE) with ion conductivities equalling or even surpassing that of liquid electrolyte solution are already available. However, the rigid nature of the SE powder materials caused poor interface contacts between individual electrolyte particles and with the active electrode particles. To solve this issue, a solid composite electrolytes (SCE) composed of ionic liquid (IL) and Li-salt supported on a porous inorganic matrix have been explored. [1] These composite electrolytes were prepared by sol-gel methods. The low viscous liquid sol-gel precursor can be impregnated into the porous powder electrodes and gelled in the electrodes, thus resulting in good interfacial contacts between the active electrode and the electrolyte. Further drying and curing make the composite electrodes compact, which results in high energy density. However, the ionic conductivity was typically lower than that of pure ionic liquid electrolyte (ILE) used in SCE. This is due to the increase of the IL viscosity in the nano-sized pores, which is known as IL confinement effect. [2] To overcome this problem, our group developed a new type of SCE with water-based sol-gel process, which is named “nano-SCE”. [3] We demonstrated systematic promotion of the Li-ion conductivity by controlling the IL molecules ordering on the silica pore surface with an functional adsorbed ice-water layer. The strong hydrogen bonding between the ice-water and the IL molecules induces the ordering of IL anions and cations on the silica surface. This interfacial interaction weakens the association between the Li-ion and its anion, thus enhancing the ion conductivity well beyond that of pure ILE. Further control of the porous structures will make the conductivity go higher, and thus can be a breakthrough technology to develop the high-conductive SEs. For designing the ideal porous structure and control the synthesis process of nano-SCEs, the silica nanoporous structure must be clarified. However, so far, it is difficult to characterize the silica matrix structure because the silica structure collapsed by the surface tension when the ILE is removed by rinsing with solvents such as ethanol and acetone and after drying both in ambient and vacuum. In this paper, we applied the CO2 supercritical drying method to extract ILE. A careful drying above CO2 super critical point enabled to keep the original structure avoiding the collapse due to the surface tension. The porous silica matrix was successfully obtained without damage or shrinkage. The porous structures of nano-SCEs with different IL/SiO2 material ratio were analysed by SEM, TEM, N2 adsorption/desorption and positron annihilation spectroscopy (PALS) technique. SEM and N2 adsorption/desorption analysis revealed that there are > 10 nm pores distributed, and their size and number were increased with ILE/SiO2 molar ratio. Our measurements confirmed that the IL confinement effect, that is, the conductivity of nano-SCE with smaller pore-size was lower due to the increasing of the viscosity of ILE filled in pores. In contrast, the surface area was decreased with ILE/SiO2 ratio due to the reduction of 5 nm size pores, which is characterized by PALS analysis. From the relationship between surface area and surface enhancement factor (sice-water/sdried) in Fig. 1, the surface conduction was verified to be increased with the surface area, indicating the conduction promotion effect was clearly related with the surface chemistry. A nano-SCE with higher conductivity can be realized by designing the pore structure with high surface area and optimized pore size. [1] J. Le Bideau, J. B. Ducros, P. Soudan and D. Guyomard, Solid-state electrode materials with ionic-liquid properties for energy storage: The lithium solid-state ionic-liquid concept, Adv. Funct. Mater., 2011, 21, 4073–4078. [2] S. Zhang, J. Zhang, Y. Zhang and Y. Deng, Nanoconfined Ionic Liquids, Chem. Rev., 2017, 117, 6755–6833. [3] P. M. Vereecken, X. Chen, K. B. Gandrud, B. Put, A. Sagara, M. Murata, M. Tomiyama, Y. Kaneko, M. Shimada, J. Steele, M. Roeffaers, M. Debucquoy and M. J. Mees, "Mechanism Analysis of Enhanced Li-Ion Conductivity in Mesoporous Silica-Based Solid Nano-Composite Electrolytes," ECS Meeting s, 2018, 470, MA2018-02. Fig. 1 The relationship between surface enhancement factor of nano-SCEs and BET surface area of porous silica matrix. The surface enhancement factor was defined as the ratio of the conductivity with and without functional ice-water layer on the silica surface. Porous silica was obtained by removal of ILE from nano-SCE with ethanol soaking for 36 hours at 40 oC and subsequent drying by CO2 super critical dryer. Figure 1

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.

Construction of uniform nanodots CeO2 stabilized by porous silica matrix for 1,2-dichloroethane catalytic combustion

The construction of uniform nanodots CeO2 stabilized by porous silica matrix (CeO2@SiO2-T) was synthesized by a spontaneous deposition method. Based on the XRD and TEM results, the CeO2 nanodots were highly dispersed on the porous silica matrix. The characterizations including O2-TPD, XPS, and NH3-TPD clarified that CeO2@SiO2-T catalysts possessed strong acidity, rich surface adsorbed oxygen species and oxygen mobility, which was beneficial to the improvement of adsorption and catalytic oxidation of 1,2-dichloroethane (DCE). The CeO2@SiO2-T catalysts exhibited high performance for DCE oxidation, in which the CeO2@SiO2-400 catalyst showed the best performance (T90 = 275 °C at a space velocity of 15000 h−1) and good stability (at 295 °C for 100 h). The characterization and activity test results showed that the richer acid sites were beneficial to the adsorption and activation of DCE, contributing to the subsequent HCl removal and vinyl chloride (VC) formation. Noticeably, the weak acid sites were more favorable for the improvement of catalytic activity. Then major of VC would be oxidized to adsorbed acetate, which could be further decomposed to COx and HCl. In addition, trace poly-chlorinated by-products were detected. The abundant surface adsorbed oxygen species and excellent oxygen mobility facilitated the further oxidation rather than the chlorination reactions.

Enhancing the lipase-mediated bioaccessibility of omega-3 fatty acids by microencapsulation of fish oil droplets within porous silica particles

Solid-state fish oil formulations composed of omega-3 (ω-3)-rich lipid droplets internalised within a nanostructured porous silica matrix have been engineered for the first time to optimise the bioaccessibility of ω-3 fatty acids. Silica-fish oil hybrid (SFOH) particles were fabricated by spray drying a submicron fish oil emulsion stabilised by hydrophilic porous silica particles. The integrity of the bioactive polyunsaturated acyl chain was preserved during synthesis and mid-term storage, highlighting the ability for silica to impart oxidative stability towards PUFA. 1H NMR analysis elucidated that the nanostructured silica network acted as a substrate-enzyme immobilisation template that facilitated enhanced fish oil hydrolysis kinetics through the interfacial activation of lipolytic enzymes, resulting in a 1.4-fold improvement in bioaccessibility compared to crude fish oil. Subsequently, this novel solid-state fish oil formulation has the potential to overcome stability drawbacks associated with PUFA and optimise the degree of ω-3 absorption into the systematic bloodstream.

Modulation of the electrocatalytic performance of PEDOT-PSS by reactive insertion into a sol-gel silica matrix

Poly(3,4-ethylenedioxythiophene) doped with poly-(styrenesulfonate), PEDOT–PSS, films synthesized by electrochemical methods can be considered as poor electrocatalyst for the oxidation of ferrocene in aqueous solution. The rate of electron transfer to that redox probe decays progressively as the amount of deposited polymer increases and the true electroactive area available for the electrochemical reaction shows quite modest figures. We present here an alternative, simple way to enhance the properties of this material which uses, exclusively, electrochemical synthesis methods. The electrocatalytic performance can be significantly improved by inserting the polymer within a pre-deposited, three-dimensional porous silica matrix forming an interpenetrating hybrid material. On the one hand, the modified PEDOT-PSS shows doping levels which trebles the unmodified material. On the other, the electron transfer constant and the true electroactive area for ferrocene oxidation increased by a factor of 2 and 4, respectively.