Mesostructured Silica Research Articles

Facile Synthesis of Monodisperse Hollow Mesoporous Organosilica/Silica Nanospheres by an in Situ Dissolution and Reassembly Approach.

Hollow structured mesoporous organosilicas are a research hotspot because of their molecularly organic-inorganic hybrid frameworks, large void spaces, permeable shells, high surface areas, uniform pores, and various applications. However, the previous reported hard-core templating method and liquid-interface assembly approach suffered from complex preparation procedures and poor uniformity for the products. In this work, we demonstrate an in situ dissolution and reassembly method to synthesize monodisperse benzene-bridged hollow mesoporous organosilica/silica nanoparticles (HMOSNs) by sequential addition of tetraethoxysilane (TEOS) and 1,4-bis(triethoxysilyl)benzene in a solution containing a cetyltrimethylammonium bromide (CTAB) surfactant. The formation of HMOSNs is completed in one pot, which is very effective and convenient. The formation mechanism of HMOSNs is ascribed to the fact that TEOS first assembles with CTAB to form mesostructured silica cores, which further dissolve and migrate to the outer layers during the deposition of mesostructured organosilica shells. The prepared benzene-bridged HMOSNs possess uniform diameter (140 nm), large pore volume (2.79 m3/g), high specific surface area (2926 m2/g), and a high doxorubicin-loading content of 16.7%. HMOSNs can deliver doxorubicin (Dox) into human breast cancer cells and reduce their excretion. Thus, the Dox-loaded HMOSNs show a high killing effect against the cancer cells.

Bi-functionalized mesostructured silicas as reversed-phase/strong anion-exchange sorbents. Application to extraction of polyphenols prior to their quantitation by UHPLC with ion-trap mass spectrometry detection.

Hybrid mesostructured silicas with wormhole-like pore structure were synthesized and bi-functionalized with n-octyl (C8) and quaternary ammonium (NR4+) groups to obtain new sorbent materials for dispersive solid-phase extraction (dSPE) of polyphenols. Due to their nature of being both a reversed-phase and a strong anion-exchanger, the materials display mixed-mode retention mechanism. During the synthesis, the functionalization conditions were varied to obtain materials with different functionalization degree. The resulting materials (denoted as HMS-RPC8-SAX-1, HMS-RPC8-SAX-2 and HMS-RPC8-SAX-3) show high surface area, wormhole-like framework and controlled pore size. They were evaluated for multicomponent extraction of 22 polyphenols, including phenolic acids, flavonoids and stilbenes, from spiked juice samples. The sample extracts were analyzed by ultra-high performance liquid chromatography coupled to ion-trap tandem mass spectrometry. The adsorption capability, the amount of sorbent, the eluent and the elution volume were optimized. Best performance was achieved by using HMS-RPC8-SAX-2, which is the material with the highest fraction of NR4+ groups. This material has a large extraction capability and provides high recovery values of the target analytes (70-101%) as a result of its hydrophobic and anion-exchange interactions. The detection limits for polyphenols in juice range from 1 to 560ngmL-1. Graphical abstract Schematic presentation of dispersive solid-phase extraction of polyphenols from juice samples using a novel sorbent based on the bi-functionalization of mesostructured silica with n-octyl and quaternary ammonium groups, followed by ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) analysis. Due to the sorbent nature of being both a reversed-phase and strong anion-exchanger, the material displays mixed mode retention mechanism that improves its extraction capability.

PH-mediated control over the mesostructure of ordered mesoporous materials templated by polyion complex micelles.

Ordered mesoporous silica materials were prepared under different pH conditions by using a silicon alkoxide as a silica source and polyion complex (PIC) micelles as the structure-directing agents. PIC micelles were formed by complexation between a weak polyacid-containing double-hydrophilic block copolymer, poly(ethylene oxide)-b-poly(acrylic acid) (PEO-b-PAA), and a weak polybase, oligochitosan-type polyamine. As both the micellization process and the rate of silica condensation are highly dependent on pH, the properties of silica mesostructures can be modulated by changing the pH of the reaction medium. Varying the materials synthesis pH from 4.5 to 7.9 led to 2D-hexagonal, wormlike or lamellar mesostructures, with a varying degree of order. The chemical composition of the as-synthesized hybrid organic/inorganic materials was also found to vary with pH. The structure variations were discussed based on the extent of electrostatic complexing bonds between acrylate and amino functions and on the silica condensation rate as a function of pH.

Preparation and Characterization of UiO-66-Supported Cu–Ce Bimetal Catalysts for Low-Temperature CO Oxidation

A series of Zr-based metal–organic frameworks (UiO-66) supported CuO–CeO2 catalysts with various total metal loadings and various Cu/Ce ratios were prepared by using a co-impregnation method. The catalytic activities of the catalysts for low temperature oxidation of carbon monoxide were compared with that supported on the ZrO2 and mesostructured cellular foam silica. The results show that the catalysts supported by UiO-66 are expected to give the best catalytic activity, which should be attributed to the special construction of UiO-66. The samples were further characterized by XRD, TEM, N2 adsorption–desorption, H2-TPR, XPS, and in situ DRIFT. And the catalyst with a bimetallic loading of 50 wt% and Cu/Ce ratio of 3:7 (wt/wt) has the highest catalytic activity, which can be attributed to the larger amount of finely dispersed Cu species strongly interacting with CeO2, the highest amounts of oxygen vacancies and Cu+ species on the catalyst surface.

Structural and Oxidative Properties of Manganese Incorporated Mesostructure Silica for Methane Oxidation

Manganese catalysts containing templated mesostructured porous silica were prepared using different methods of preparation, namely, the direct hydrothermal (DHT), solid-state ion exchange (SSI), template ion exchange (TIE), and impregnation (Imp) methods. The physical-chemical properties of materials were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, FT-IR, TEM, EDX, UV-Vis, EPR, and H2 TPR techniques. The results of this study indicate that the obtained catalysts retained their hexagonal mesopore structure after introducing Mn into MCM-41. On the contrary, the crystalline phase of manganese oxide was stabilized on the external surface and inside the mesoporosity of the MCM-41 and seems to be dependent on the synthesis method used. Catalytic performances of synthesized materials were then investigated in methane oxidation at atmospheric pressure. The results showed that the metal loading and catalysts synthesis procedure influence the catalytic performance of the obtained materials. Moreover, the activity of the catalyst depends on the crystalline phase and particularly on the environment of the active phase.

Cell-penetrating peptide together with PEG-modified mesostructured silica nanoparticles promotes mucous permeation and oral delivery of therapeutic proteins and peptides.

Poor permeation across intestinal mucous barriers often limits the oral delivery of prospective therapeutic proteins and peptides (TPPs). In order to address this issue, cell penetrating peptide (CPP) together with PEG modified and pore-enlarged mesostructured silica nanoparticle (NP) were constructed to form the mucus-penetrating electrostatic particle-complexes, CPP/TPP/NP. Alone, CPP and TPP often present with poor stability, and their traditional electrostatic complex shows reduced pharmacodynamics. To provide satisfactory protection, silica NPs were loaded with CPP and TPP (CPP@NP and TPP@NP), respectively, and then CPP@NP and TPP@NP could together form CPP/TPP/NP via electrostatic interaction. As a result, CPP involvement with PEG modification showed an 8.45-, 1.62- and 5.09-fold increase in cellular uptake, exocytosis and final transcellular permeation in mucous conditions, respectively. It was found that CPP involvement mainly affected transport and exocytosis, and the PEG polymer significantly influenced mucous penetration and cellular uptake, which could further promote CPP ability for uptake and exocytosis. Additionally, NP-mediated CPP/TPP/NP showed a similar uptake mechanism with supporting carriers (clathrin-mediated endocytosis), and could strengthen transcellular routes (the endoplasmic reticulum-Golgi apparatus pathway and the lysosome route). Utilizing recombinant growth hormone (RGH) as a model TPP, oral administration of the RGH-loaded CPP/TPP/LMSN-PEG10k with hydrophilic and electroneutral properties induced 5.41- and 4.91-fold increases in pharmacodynamics in vitro and in vivo, respectively. Thus, CPP/TPP/NP significantly promoted mucous permeation and shows promising potential for oral delivery of TPPs.

Biomimetic Cu, Zn and Cu2 complexes inserted in mesoporous silica as catalysts for superoxide dismutation

Abstract Three CuZn-superoxide dismutase (SOD) functional mimics, [CuZn(dien)2(μ-Im)](ClO4)3 (1), [Cu2(dien)2(μ-Im)](ClO4)3 (2) (Im = imidazole, dien = diethylenetriamine), and [CuZn(salpn)Cl2] (3) (H2salpn = 1,3-bis(salicylideneamino)propane), were successfully inserted into the nanochannels of SBA-15 type mesoporous silica with retention of the silica mesostructure. X-ray absorption spectroscopic studies indicate that the encapsulated complexes keep unchanged the first-shell environment of Cu(II) and Zn(II) ions. Magnetic measurements suggest that the nanochannels constrain the geometry of the μ-imidazolate-Cu(II)2 core modifying the relative orientation of the two copper coordination planes. Confinement imposed by the silica nanochannels upon encapsulation of complexes 1 and 2 leads to stable hybrid materials at physiological pH with enhanced SOD activity relative to the free complexes. Unlike the imidazolato-bridged compounds, insertion of 3 in mesoporous silica leads to a less stable hybrid material exhibiting partial release into the aqueous solution and O2•− dismutation rate slower than the free complex. The covalent binding of a mononuclear Cu(dien)Im+ moiety to the mesoporous silica showed lower SOD activity than encapsulated imidazolato-bridged CuZn and Cu2 complexes. The results emphasize the positive effect of encapsulation on SOD activity of imidazolato-bridged dinuclear complexes.

Simultaneous determination of pindolol, acebutolol and metoprolol in waters by differential-pulse voltammetry using an efficient sensor based on carbon paste electrode modified with amino-functionalized mesostructured silica

In this work, hexagonal mesoporous silica (HMS) and amino-functionalized HMS (HMS-NH2) were prepared and incorporated into carbon paste electrodes (CPEs) to obtain electrochemical sensors for pindolol (Pin), acebutolol (Ace) and metoprolol (Met) determination in waters by voltammetric techniques. The materials were characterized and they showed high specific surface area, large pore volume and a quasi-spherical morphology. Firstly, the electrochemical behaviour of the modified CPEs was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Then, the dependence of the current intensity with the electrolyte support (type and pH) and the accumulation time was investigated to optimize the experimental conditions for simultaneous β-blockers determination by DPV. Results showed that the sensor modified with functionalized silica (NH2-HMS-CPE) exhibited strong adsorption activity, showing three well-defined peaks in the differential pulse voltammograms, that appeared at about +0.85 V (Pin), +1.11 V (Ace) and +1.45 V (Met). This fact can be attributed to the high surface area of the material, with a 3 D wormhole-like channel structure that favoured excellent pore accessibility, and the synergistic effect produced by the grafted amino groups producing hydrogen bond interactions with the oxygen atoms of the target β-blockers. The prepared sensor exhibits good reproducibility, wide linear ranges and very low detection limits (0.1, 0.046 and 0.23 μmol L−1 for Pin, Ace and Met, respectively). Moreover, the NH2-HMS-CPE was successfully applied for the simultaneous determination of Pin, Ace and Met in tap, mineral, river and sewage effluent waters with simple sample treatment (recoveries 97–112%).

Confinement of iPP chains in the interior of SBA-15 mesostructure ascertained by gas transport properties in iPP-SBA-15 nanocomposites prepared by extrusion

Different nanocomposites based on isotactic polypropylene (iPP) and mesoporous SBA-15 silica have been prepared by melt extrusion as an attempt of incorporating iPP within the nanometric SBA-15 pores by the action of shear forces during processing. The observed inclusion of iPP chains in the SBA-15 leads to a change in the gas transport properties of the resultant iPP/SBA-15 membranes together with the improvement of their ultimate mechanical performance. Existence of confinement effects is observed, consequently, by the exhibited transport properties and is confirmed through real-time variable-temperature Small Angle X-ray Scattering (SAXS) experiments with synchrotron radiation. The former indicates that the mesostructure of silica is full, i.e., these particles essentially act as fillers. The latest has been proved by the presence of a discontinuity in the intensity of the (100) SBA-15 diffraction, which turn SAXS measurements at variable temperature into a valuable means to corroborate the development of iPP crystallites within SBA-15 channels. Moreover, SAXS profiles provide information about the most probable long spacing of chains located outside the SBA-15 nanospaces. On the other hand, changes in the β viscoelastic relaxation have been correlated to the influence of SBA-15 in the iPP amorphous regions. All the structural features have been crucial for the understanding the mechanical response shown by these nanocomposites. Mesoporous particles exert a reinforcing role and reduce the deformation capacity in the ultimate materials as their content is increased.

Layered-Expanded Mesostructured Silicas: Generalized Synthesis and Functionalization

Mesostructured layered silicas have been prepared through a surfactant-assisted procedure using neutral alkylamines as templates and starting from atrane complexes as hydrolytic inorganic precursors. By adjusting the synthetic parameters, this kinetically controlled reproducible one-pot method allows for obtaining both pure and functionalized (inorganic or organically) lamellar silica frameworks. These are easily deconstructed and built up again, which provides a simple way for expanding the interlamellar space. The materials present high dispersibility, which results in stable colloidal suspensions.

One-Pot Hydrothermal Synthesis of Benzalkonium-Templated Mesostructured Silica Antibacterial Agents.

Novel mesostructured silica microparticles are synthesized, characterized, and investigated as a drug delivery system (DDS) for antimicrobial applications. The materials exhibit a relatively high density (0.56 g per 1 g SiO2) of benzalkonium chloride (BAC), pore channels of 18 Å in width, and a high surface area (1500 m2/g). Comparison of the small-angle X-ray diffraction (SAXRD) pattern with Barrett-Joyner-Halenda (BJH) pore size distribution data suggests that the 18 Å pores exhibit short-range ordering and a wall thickness of ca. 12 Å. Drug release studies demonstrate pH-responsive controlled release of BAC without additional surface modification of the materials. Prolonged drug release data were analyzed using a power law (Korsmeyer-Peppas) model and indicate substantial differences in release mechanism in acidic (pH 4.0, 5.0, 6.5) versus neutral (pH 7.4) solutions. Microbiological assays demonstrate a significant time-dependent reduction in Staphylococcus aureus and Salmonella enterica viability above 10 and 130 mg L-1 of the synthesized materials, respectively. The viability of cells is reduced over time compared to control samples. The findings will help in widening the use of BAC as a disinfectant and bactericidal agent, especially in pharmaceutical and food industries where Gram-positive and Gram-negative bacterial contamination is common.

Oxidative Desulfurization of Model Diesel Fuel by Vanadium Granular-Shape Mesoporous (V/GMS) Silica System as Nanocatalyst

The performance of V-containing granular-shape mesoporous (V/GSM) silica systems in oxidative desulfurization of model diesel fuel was studied. FTIR, XRD, SEM, TEM, N2 adsorption-desorption, UV-Vis, and NH3-TPD techniques were used to analyze the surface properties of the functionalized catalyst. The mesostructure of silica remains intact after vanadium modifications as shown by XRD and adsorption-desorption analysis, while spectroscopy indicates the successful impregnation of neat vanadium oxide inside the porous silica support. The oxidation desulfurization of model diesel fuel was effectively catalyzed by this catalyst and the highest activity was shown by 4.8% V/GSM catalyst. Compared with their conventional V/MCF and V/MCM-41 counterparts, SSM-supported vanadium catalysts showed much higher activity. This may be associated with the higher reducibility and better diffusion of reactants and products in V/MCF and V/MCM-41catalysts.

Zirconium-Loaded Mesostructured Silica Nanoparticles Adsorbent for Removal of Hexavalent Chromium from Aqueous Solution

Zirconium-loaded mesostructured silica nanoparticles (Zr/MSN) were developed for the removal of hexavalent chromium (Cr(VI)) from aqueous solutions. X-ray diffraction, transmission electron microscopy, and Brunauer–Emmett–Teller results revealed that both MSN and Zr/MSN showed a characteristic highly ordered hexagonal pore structure with a high specific area of 821–1219 m2 g–1. Fourier transform infrared analysis showed that the presence of Zr diminished the absorbance band that was assigned to silanol groups of the structural defect sites, while XPS analysis of the binding energy of Si–O–Zr indicated interactions between the silanol groups and zirconium. The interaction of zirconium and silanol groups from the structural defect sites generated bidentate zirconium, which acted as an active site for the adsorption. The experimental results showed that the modification of MSN with zirconium significantly enhanced the adsorption capacity for Cr(VI). The equilibrium isotherm data showed that the adsorption pr...

BPB dye confined growth of surfactant-assisted mesostructured silica matrix fiber optic sensing tracers

Thermally stable surfactant modified silica nano-matrix is synthesized by the sol–gel method at low temperature. The surfactant such as cetyltrimethylammonium bromide (CTAB) assisted silica matrix is encapsulated with bromophenol blue (BPB) for sensing activities. Prepared nano-matrix consists of numerous morphological structures such as a pseudo-spherical, hierarchal and islands. The morphology of mesoporous high surface area matrices is strongly affected by CTAB, BPB dye and the aging conditions that determine the transformation from disordered silica nano-matrix morphologies to ordered encapsulated structures. Furthermore, smooth surface matrices with low surface roughness 1.2 nm, low refractive index 1.36, large pores and small dimensions of heteroatoms contribute to the stable sensing activities. The response of coated fiber optic is determined at dynamic pH range 1–12. The prepared sensor has reversibility/repeatability, stability and fast response time of approximately 0.25 s in basic media. The accuracy of sensing device measurements in household ammonia solution and the borax solution suggested that prepared device has clear potential for daily life usage.

Platinum and Molybdenum Oxide Supported on Mesostructured Silica Nanoparticles for n-Pentane and Cyclohexane Isomerization

Alkane isomerization into its equivalent branched isomers has gained numerous attention as a reaction to obtain high quality fuel. In this study, platinum and molybdenum oxide supported on mesostructured silica nanoparticles (Pt/MoO3/MSN) was prepared via impregnation method and tested for n-pentane and cyclohexane isomerization. The catalyst was characterized by using X-ray diffraction (XRD), nitrogen (N2) physisorption, and pyridine Fourier-transform infrared (pyridine-FTIR) spectroscopy. The IR result revealed that the addition of Pt and MoO3 into MSN formed different strength of Lewis and Brönsted acid sites. It was observed that the catalyst possessed strong acid sites and several numbers of relatively weak Lewis and Brönsted acid sites. Pt/MoO3/MSN was catalytically active towards n-pentane and cyclohexane isomerization with conversion of 63 and 87%, respectively, at 300 °C. It was proposed that the addition of Pt might assist the generation of active protonic acid sites from molecular hydrogen via the mechanism of hydrogen spillover and hence improve isomerization reaction.

Direct synthesis of SILVER nanoparticles and polyaniline into the MESOPORES of SBA-15

The uniform structural pores architecture in nanoscopic domain of ordered mesoporous silicas, such as MCM-41 and SBA-15, can be used as a confined space to produce nanomaterials with controlled dimensions and cylindrical shape. In this study, we report the synthesis of a ternary nanocomposite constituted of silver nanoparticles and polyaniline concomitantly produced in the presence of SBA-15. The synthetic process involved firstly the adsorption of aniline vapor into the silica pores followed by its polymerization by reacting with the silver salt (AgN(SO2CF3)2) solubilized in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide (BMImTf2N). With this synthetic approach the reaction proceeded quickly and efficiently, generating the silver-polyaniline nanocomposite mainly into pores and without collapsing the silica mesostructure. Surface area and pore volume of SBA-15 decreased after the reaction proceeded, indicating the formation of polyaniline and silver nanoparticles composite inside the pores and complementary analysis evidenced the presence of some silver nanoparticles outside pores. The measured electrical conductivity of the ternary composite in the order of 10−6 S cm−1 was coherent to the presence of the polymer and silver nanoparticles inside the pores of the insulator SBA-15 mesostructure rather than on the surface of the particles. The prepared SBA-15 ternary nanocomposite presented higher silver nanoparticles loadings of and superior surface area than the ones observed to small pore silicas, such MCM-41. The improvement in textural properties of the nanocomposite are favorable aspects for the further development of sensors and catalysts.

Fabrication of β-cyclodextrin modified mesostructured silica coated multi-walled carbon nanotubes composites and application for paraben removal.

In this work, the novel β-cyclodextrin modified mesostructured silica coated multi-walled carbon nanotubes (MWCNTs) composites were synthesized and applied for the removal of parabens in aqueous solution. The prepared MWCNTs/SiO2/β-CD composites were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and thermogravimetric analysis. The effects of the amount of adsorbent, pH and elution solvents on the removal efficiency of parabens from water solutions were investigated. Under the optimized conditions, over 95% removal efficiency was achieved by using 40 mg of MWCNTs/SiO2/β-CD adsorbents to absorb the parabens from 60 mL of 0.5 μg/mL parabens solutions. The solution pH in the range from 5 to 9 has no influence on the removal efficiency and the parabens sorption capacity of the prepared adsorbents were around 0.75 μg/mg. Furthermore, the stability and reusability studies demonstrated that the prepared MWCNTs/SiO2/β-CD composites are cost-effective adsorbents for the removal of parabens from water with high regeneration efficiency. The composites fabricated in this study could become an attractive candidate for water purification.

Silica–Carbon Nanocomposite Acid Catalyst with Large Mesopore Interconnectivity by Vapor-Phase Assisted Hydrothermal Treatment

Mesostructured silica–carbon nanocomposites with large mesopore interconnectivity are created from sucrose as sustainable carbon source using a mild vapor-phase assisted hydrothermal treatment procedure. The resultant mesostructured silica–carbon nanocomposite can be readily sulfonated to provide a strong acid catalyst with high sulfonic acid density, or the carbon phases of the nanocomposite can be removed by calcination to produce a silica material with ultrahigh porosity (Vpore = 1.25 to 1.34 cm3 g–1). A superior catalytic activity is demonstrated for the solvent-less condensation of 2-methylfuran with furfural; both product yield and conversion rate surpass that of reference catalysts such as their counterparts from dry pyrolysis and the commercial strong acid resins. The enhanced catalytic activity is attributed to the higher SO3H acid density (0.64 to 1.08 mmol g–1), the larger and better communicating mesopores (Vmeso = 0.38 to 0.82 cm3 g–1) and the abundant presence of surface oxygen-containing fu...

Tailored doxycycline delivery from MCM-41-type silica carriers

Doxycycline, an antibiotic from the tetracycline class with a broad spectrum of activity, was used to prepare drug delivery systems based on pristine and functionalized mesostructured silica supports. MCM-41-type materials with different textural, structural, and surface properties were used to assess their influence on the drug release kinetics. Small- and wide-angle XRD, FTIR spectroscopy and N2 adsorption/desorption isotherms were used to characterize the carriers before and after doxycycline loading. The drug release experiments were performed in vitro in 0.2 M phosphate buffer solution at 37 °C, and the slowest drug release kinetics was obtained for magnesium-modified MCM-41 carrier. All drug-loaded materials exhibited good antibacterial activity against Klebsiella pneumoniae ATCC 10031 strain, similar to the drug alone.

Functionally Active Membrane Proteins Incorporated in Mesostructured Silica Films.

A versatile synthetic protocol is reported that allows high concentrations of functionally active membrane proteins to be incorporated in mesostructured silica materials. Judicious selections of solvent, surfactant, silica precursor species, and synthesis conditions enable membrane proteins to be stabilized in solution and during subsequent coassembly into silica-surfactant composites with nano- and mesoscale order. This was demonstrated by using a combination of nonionic ( n-dodecyl-β-d-maltoside or Pluronic P123), lipid-like (1,2-diheptanoyl- s n-glycero-3-phosphocholine), and perfluoro-octanoate surfactants under mild acidic conditions to coassemble the light-responsive transmembrane protein proteorhodopsin at concentrations up to 15 wt % into the hydrophobic regions of worm-like mesostructured silica materials in films. Small-angle X-ray scattering, electron paramagnetic resonance spectroscopy, and transient UV-visible spectroscopy analyses established that proteorhodopsin molecules in mesostructured silica films exhibited native-like function, as well as enhanced thermal stability compared to surfactant or lipid environments. The light absorbance properties and light-activated conformational changes of proteorhodopsin guests in mesostructured silica films are consistent with those associated with the native H+-pumping mechanism of these biomolecules. The synthetic protocol is expected to be general, as demonstrated also for the incorporation of functionally active cytochrome c, a peripheral membrane protein enzyme involved in electron transport, into mesostructured silica-cationic surfactant films.