Mesoporous Silica MCM-41 Research Articles

Hierarchically Porous Three-Dimensional (3D) Carbon Nanorod Networks with a High Content of FeNx Sites for Efficient Oxygen Reduction Reaction.

Efficient, durable, and inexpensive electrocatalysts are recommendable for accelerating the kinetics of oxygen reduction reaction and achieving high performance. Herein, with predesigned hierarchically porous silica nanorods as a hard template, hierarchically macro-bimodal meso/microporous 3D carbon interwoven nanorod networks containing a high content of single-atom FeNx species (Fe/RNC) were prepared by melting of precursors and confined pyrolysis within the pores of the hard template. What distinguishes the use of silica nanorods as a hard template is that it not only provides a porous texture for confined pyrolysis of the precursors but also the interwoven texture of the nanorods gives rise to a macroporous mesh-like morphology. Benefiting from the ultrahigh iron content (5.69 wt %) of the FeNx sites, a 3D porous network configuration with high accessibility of active centers, as well as a high specific surface area of 793 m2g-1, the as-prepared Fe/RNC exhibited superior activity and durability for ORR and zinc-air batteries. For comparison, the catalyst Fe/NC-MCM, which was prepared with a similar procedure but with unimodal mesoporous silica MCM-41 nanoparticles as the hard template, possesses a less porous structure and active accessibility and thus exhibits inferior ORR activity. This work provides an effective design/nanoengineering for electrocatalysts in ORR and zinc-air batteries and will inspire more research on accessibility of active sites in non-noble carbon-based electrocatalysts.

Desulfurization of Real Diesel Fuel onto Mesoporous Silica MCM-41 Implementing Batch Adsorption Process: Equilibrium, Kinetics, and Thermodynamic Studies

In the current work, sulfur was removed from actual diesel fuel containing 1.2 wt.% sulfur from the Al-Dura Oil Refinery (Iraq), which was studied using adsorption desulfurization with the spherical mesoporous silica MCM-41. This study investigated the effects of different operating conditions, including the dose of MCM-41 (0.04-0.2 gm), time (60-180 min), and temperature (30-70°C). The optimal working conditions were determined to be 0.4 gm MCM-41, 180 min, and 70°C. After exploring the isotherm models of Langmuir, Freundlich, and Temkin, Temkin models with a correlation coefficient (R2 = 0.9996) were selected to best represent the stable data. The kinetics of sulfur components on MCM-41 were studied using pseudo-first-order and pseudo-second-order kinetic models and intra-particle diffusion. A pseudo-first-order adsorption kinetic model with a correlation coefficient (R2) of 0.9867 can accurately represent the adsorption process. Gibbs free energy (ΔGo), enthalpy (ΔHo), and entropy (ΔSo) were calculated as thermodynamic parameters. The adsorption of total sulfur-containing compounds onto mesoporous silica was spontaneous, endothermic, and increased the irregularity of the sulfur compounds on the surface of the adsorbent. The total sulfur content of actual diesel fuel was reduced from 1.2% to 0.84%, corresponding to a desulfurization efficiency of 29.72%. Consequently, the findings of this study might be used as a starting point for future research.

A Novel Formulation of Mesoporous Silica Nanoparticles Functionalized with Polyaniline Brush Polymer: Synthesis and Characterization

Mesoporous silica nanoparticles and polyaniline (PANI) are widely used in many potential applications. This work establishes a new formulation that functionalizes the surface of mesoporous silica MCM-41 nanoparticles with a brush polymer of polyaniline to synergistically combine their properties. The new formulation is designed to fit in many applications due to its high surface area and good electrical conductivity. Results showed the successful preparation of MCM-41 with a spherical porous structure. The polyaniline functionalization on MCM-41 was confirmed by FTIR.

Facile fabrication of Z-scheme TiO2/ZnO@MCM-41 heterojunctions nanostructures for photodegradation and bioactivity performance

Designing Z-scheme heterojunction materials as a highly efficient photocatalyst is essential in environmental remediation. Herein, a new type of TiO2/ZnO@MCM-41 (TZM-41) heterojunction photocatalyst was designed for degrading organic dyes from wastewater and antibacterial activity on Staphylococcus (S. aureus). First, mesoporous MCM-41 silica material was fabricated with the sol–gel method and then calcinated under 550 °C to form porous material. Subsequently, ZnO and TiO2 crystals were grown onto the MCM-41 surface to obtain a TZM-41 heterojunction photocatalyst. TZM-41 nanocomposite with visible light excitations revealed a maximum degradation of methylene blue (MB) and methyl orange (MO) under visible light irradiation. The reusability tests, reaction mechanism, reaction kinetics as well as TOC and COD tests were investigated on the photocatalytic performance. The findings obtained from the reaction mechanism, quenching radical test, and electron spin resonance (ESR) technique indicated that hydroxyl radicals (•OH) and superoxide anion (•O2−) play an essential role in organic dyes degradation. Furthermore, the antibacterial properties of ZnO and TZM-41 nanocomposite were evaluated on S. aureus. The current study provides new horizons to develop Z-scheme heterojunction materials for improvement in water treatment and remediation.

The phase change hysteresis characteristics ofNa2HPO4·12H2O: A molecular dynamics study

• The hysteresis degree of DSP is decreased after encapsulation. • The reason for the hysteresis is the difference in the molecular structure during the heating and cooling process. • The system energy of encapsulated DSP is mainly decided by “randomly distributed” molecules. • Molecular dynamics simulation of pure DSP and encapsulated DSP. There is a phenomenon of inconsistent melting and solidification behavior of PCM, which is called phase change hysteresis, generally expressed by the difference between melting temperature (T m ) and solidification temperature (T s ). The hysteresis degree (T m -T s ) is proportional to the energy loss of the system, if the temperature is beyond the operating temperature range of the system, the latent heat of the PCM cannot be exploited. The phase change hysteresis and supercooling were regarded as the same concept in previous studies no matter simulations or experimental research, which will lead to large errors. It is believed that there is a large hysteresis degree of inorganic PCM besides higher supercooling degree, poor chemical stability, and serious phase separation phenomenon, like Na 2 HPO 4 ·12H 2 O(DSP), which is prone to dehydrate from Na 2 HPO 4 ·12H 2 O to Na 2 HPO 4 ·7H 2 O during the heating and cooling process.DSP is adsorbed by SiO 2 via hydrogen bond, van der Waals force, and capillary effect, which can solve the above shortcomings. There are certain limitations in studying the hysteresis properties of PCM via experimental methods. As so far, the hysteresis properties of inorganic hydrated salts are rarely discussed in related papers, the reason for the hysteresis phenomenon is not explained, and the nucleation mechanism is not clear. Therefore, a composite phase change material (CPCM) model with DSP as the core and mesoporous silica MCM-41 as the shell was established in this work. The phase change hysteresis (PCH) characteristics are studied by analyzing the radial distribution function (RDF), self-diffusion coefficient(D), and density. The molecular motion of the interface layer was studied by the molecular dynamics(MD) method, and the arrangement of microscopic particles before and after adsorption was compared. The results showed that the hysteresis degree of DSP decreases to 1.5 °C after encapsulation by SiO 2 , which is because the effect of “Near-range ordered” molecules tend to disappear. After experimental verification, there is a 20% error between the simulation and experimental results. In addition, the reason for the hysteresis is the difference in the molecular structure that determines the energy of the system during the heating and cooling process. The purpose of this paper is to explain the reasons for the hysteresis from the view of microscopic and to provide a basis for the design of LHTES systems.

Preparation and Evaluation of SBA-16, ZSM-5 and MCM-41 Mesoporous Silica Nanoparticles as Drug Delivery System for Carvedilol

Carvedilol is a non-selective beta/alpha1 blocker that is broadly used in treatment of arrhythmia, congestive heart failure, hypertension, and myocardial infarction. Enhancing carvedilol low solubility and dissolution rate would help in improving the efficiency of the tablet dosage form. In this study, different types of silica nanoparticle (NPs) (SBA-16, MCM-41 and ZSM-5) were synthesized. Coupling of SBA-16 with 3-Aminopropyl-triethoxysilane (APTES) was performed to improve surface characteristics of SBA-16. Different methods to load carvedilol on these carriers were used with high-performance liquid chromatography (HPLC) as a method of analysis for carvedilol. For the characterization of the loaded NPs Fourier -transform infrared spectroscopy (FT-IR), X ray crystallography (XRD) and Therapeutic goods administration (TGA) were used. MCM-41 loaded with Carvedilol was decided to be formulated as tablet dosage and compared with tablets contain carvedilol without carrier. The results showed that SBA-16, SBA-16 coupled, ZSM-5 and MCM-41 carriers were used successfully to load carvedilol in a good drug load percent of 64.5, 69.3, 82 and 90%, respectively. MCM-41 gave highest loading efficiency of carvedilol using solvent evaporation method and the dissolution of carvedilol from powder was superior to the pure carvedilol where it gave 100% release of the drug at 15 minutes compared to 30% of pure carvedilol. MCM-41 loaded with carvedilol was successfully formulated as tablet dosage form according to the specifications of USP and the release of carvedilol from the prepared tablet was 99% at 15 min compared to the carvedilol released from tablets prepared using carvedilol powder which gave 38% which indicates the efficiency of the carrier in increasing the solubility and dissolution of carvedilol, a class II BCS drugs.

Modification of the MCM-41 mesoporous silica and its influence on the hydration and properties of a cement matrix

Recently, there has been a growing interest in materials that make it possible to reduce cement consumption in the concrete technology while improving the parameters of a final product. In this paper the validity of using, as an admixture to cement, the mesoporous silica of the MCM-41 structure type (MCM-41), modified with funcosil (hydrophobizing agent), triethanolamine, iron nitrate, and gluconic acid, has been analyzed. The effectiveness of the modification was evaluated on the basis of chemical and phase composition analysis, while the effect of admixtures on the cement matrix (CM) properties was additionally evaluated on the basis of selected physico-mechanical parameters and a hydration heat analysis. The results showed the quantitative effect of the modifications on the MCM-41 and CM composition. All the admixtures affected the rate and total amount of heat released during the hydration process. The presence of the triethanolamine and gluconid acid significantly delayed the main peak of the hydration process while the presence of the iron nitrate and gluconid acid decreased the total amount of heat released. Regardless of the maturation time, an increase in the CM compressive strength with the modified MCM-41 and a decrease in the percentage water loss during drying were observed. Only the gluconic acid modification caused a deterioration in the strength parameters. In conclusion, the use of the MCM-41 and its modifications in the production process of cement composites can positively affect the properties of the final product.

Hybridising inorganic materials with fluorescent BOPHY dyes: A structural and optical comparative study.

This study presents the design and characterization of new monochromatic light-harvesting systems based on inorganic porous materials hybridized with organic dye molecules within their structure. A new fluorescent BOPHY dye was prepared, characterized optically and used as both reference and synthetic precursor for two alkoxysilane derivatives that were incorporated separately within a silica structure. The dyes, one bearing one alkoxysilane group and the other one two, were co-condensed with tetraethyl orthosilicate to form a hybrid organo-silica framework, where they are found at specific locations. The structure of the new materials was analysed by powder XRD and TEM, which confirmed the presence of the hexagonal pore arrangement typical of mesoporous MCM-41 silica particles. The steady-state and time-resolved analysis showed that the particles where the dyes are most dispersed within the framework retain the highest fluorescence quantum yield, up to 0.63, in the green-yellow region of the visible spectrum. On the other hand, increasing the content of BOPHY units in the solid matrix seem to favour non-radiative deactivation pathways and aggregation phenomena, which lower the efficiency of light emission. The materials also exhibit interesting properties, such as a dual excited-state decay and fluorescence anisotropy. The short fluorescence lifetime, about 2 ns, matches the typical singlet lifetime of BOPHY dyes, whereas the long component, up to 20 ns, is attributed to delayed fluorescence, which could take place via charge recombination. Optical anisotropy experiments revealed that all materials show polarised light emission to a significant extent and, for most samples, it was also possible to determine a polarisation transfer decay trace, from 400 to 800 ps This is ascribed to the occurrence of energy migration between neighbouring dye units within the silica structure.

Nanocasting nanoporous nickel oxides from mesoporous silicas and their comparative catalytic applications for the reduction of p-nitrophenol

Herein, nanoporous nickel oxides were prepared through nanocasting using ordered- and less-ordered mesoporous silica templates, i.e., MCM-41 and KCC-1, respectively. The products resembled the replica of the inner architecture of each template. NiO-MCM-41 (nanocasted in MCM-41) possessed a highly ordered structure originating from the arrangement of nanorods resulting in a large specific surface area of 53 m2 g−1. On the other hand, NiO-KCC-1 (nanocasted in KCC-1) exhibited the combination of ordered nanorod and non-ordered foam-like structures with a less specific surface area of 23 m2 g−1. Ultimately, the catalytic tests in the reduction of p-nitrophenol (p-NP) with sodium borohydride (NaBH4) demonstrated that NiO-MCM-41 had significantly higher activity (kobs = 0.25 min−1) and better reusability (p-NP conversion of 92% after 3 times reactions) than those of NiO-KCC-1 (kobs = 0.14 min−1 and a 35% p-NP conversion after 3 times reactions) due to the more improved molecular diffusion within a highly ordered structure. The preferred mechanism was found to follow the Langmuir–Hinshelwood route in which both reactants (p-NP and [BH4]−) were initially adsorbed onto the surface of the catalyst.

Carbon dioxide adsorption/desorption performance of single- and blended-amines-impregnated MCM-41 mesoporous silica in post-combustion carbon capture

Abstract High-surface-area, hexagonal-structured mesoporous silica, MCM-41, was synthesized and wet impregnated with three different amines of 2-(ethylamino) ethanol (EAE), ethylenediamine (EDA), and tetraethylenepentamine (TEPA) for use as solid adsorbents in post-combustion CO2 capture application. The CO2 adsorption test was performed at 25°C and atmospheric pressure using 15/85 vol% of CO2/N2 at a 20-mL/minute flow rate. Desorption was carried out at 100°C under 20 mL/minute of N2 flow. The results show that the capacity and rate of CO2 adsorption obtained from all the amine-modified adsorbents were significantly increased with increasing amine loading due to carbamate formation. Desorption efficiency and heat duty for regeneration were also affected by the amount of amine loading. The more stable the carbamate produced, the higher the energy was required. They exhibited the highest adsorption–desorption performance at 60 wt% amines used for impregnation. Blended EAE/TEPA at different weight ratios at a total concentration at 60 wt% amines was impregnated on MCM-41 adsorbent. Sorbent impregnated with 50%/10% of EAE/TEPA showed the best performance of 4.25 mmolCO2/g at a high adsorption rate, a low heat duty of 12 kJ/mmolCO2 and with 9.4% reduction of regeneration efficiency after five repeated adsorption–desorption cycles.

Formulation and Biological Evaluation of Mesoporous Silica Nanoparticles Loaded with Combinations of Sortase A Inhibitors and Antimicrobial Peptides.

This study aimed to develop synergistic therapies to treat superbug infections through the encapsulation of sortase A inhibitors (SrtAIs; trans-chalcone (TC), curcumin (CUR), quercetin (QC), or berberine chloride (BR)) into MCM-41 mesoporous silica nanoparticles (MSNs) or a phosphonate-modified analogue (MCM-41-PO3−) to overcome their poor aqueous solubility. A resazurin-modified minimum inhibitory concentration (MIC) and checkerboard assays, to measure SrtAI synergy in combination with leading antimicrobial peptides (AMPs; pexiganan (PEX), indolicidin (INDO), and [I5, R8] mastoparan (MASTO)), were determined against methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The results demonstrated that the MCM-41 and MCM-41-PO3− formulations significantly improved the aqueous solubility of each SrtAI. The MICs for SrtAI/MCM-41-PO3− formulations were lower compared to the SrtAI/MCM-41 formulations against tested bacterial strains, except for the cases of BR/MCM-41 and QC/MCM-41 against P. aeruginosa. Furthermore, the following combinations demonstrated synergy: PEX with TC/MCM-41 (against all strains) or TC/MCM-41-PO3− (against all strains except P. aeruginosa); PEX with BR/MCM-41 or BR/MCM-41-PO3− (against MSSA and MRSA); INDO with QC/MCM-41 or QC/MCM-41-PO3− (against MRSA); and MASTO with CUR/MCM-41 (against E. coli). These combinations also reduced each components’ toxicity against human embryonic kidney cells. In conclusion, MCM-41 MSNs provide a platform to enhance SrtAI solubility and demonstrated antimicrobial synergy with AMPs and reduced toxicity, providing novel superbug treatment opportunities.

CO2 Capture over MCM-41 and SBA-15 Mesoporous Silicas Impregnated with Chitosan

CO₂ Capture over MCM-41 and SBA-15 Mesoporous Silicas Impregnated with Chitosan

Ternary nanocomposite of TiO2-ZnO/MCM-41: synthesis and electrochemical performance in supercapacitors

The development of composite materials in nano-scale for electrochemical activity has remained an enormous challenge in the supercapacitors (SCs) arena. In this work, a new type of ternary TiO2-ZnO/MCM-41 nanocomposite was designed and prepared for further improvement to the electrochemical performance. First, mesoporous MCM-41 silica material was prepared with a sol-gel method and then calcinate under 550 °C to form porous material. Subsequently, ZnO-TiO2 crystals were grown on the MCM-41 silica material surface via a solvothermal method to obtain ternary nanocomposite. The morphology and structure features of the ternary nanocomposite were investigated with FESEM, TEM, and AFM. From the BET analysis, the specific surface area (SSA) of the nanocomposite obtained 580 m2·g−1, which provided an excellent platform for the transmission of ions and electrons. After that, energy storage performance was evaluated by electrochemical measurements such as cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS). The electrochemical performance measurements demonstrate a specific capacitance (Cs) as high as 642.4 F·g−1. Moreover, it exhibits excellent cyclic stability with 98.7% capacitance retention after 5000 cycles, which is beyond that of most of the reported silica-based SCs. The current study provided a rational design and synthesis of multifunctional catalysts for the development of SCs applications.

Anti-blastocystosis activity of antioxidant coated ZIF-8 combined with mesoporous silicas MCM-41 and KIT-6

The biocompatible hybrid Zeolitic imidazolate framework-8 (ZIF-8)/structured silica nanocomposite can be loaded with antioxidants such as curcumin and resveratrol to offer multiple advantages of drug functionalization and structural stability. blastocystosis, an enteric parasite, has various outcomes and its treatment includes drugs which have side effects and do not result in a full cure. We aimed to design novel biocompatible nanocomposites containing natural antioxidant, resveratrol or curcumin and ZIF-8/mesoporous silica. We also assessed their anti-blastocystosis activities as bioactive novel nanocomposites. The nano-silica (MCM-41 and KIT-6) was synthesized using a hydrothermal technique and made composite with ZIF-8 using an ultrasonic technique. The antioxidants, curcumin and resveratrol, were loaded over ZIF-8/MCM-41 and ZIF-8/KIT-6 using a rotary evaporator technique to form novel nanocomposites with bioactive properties. The formulated nanocomposites were characterized. To test their biological activity, suspension of cultured blastocystosis cysts (subtype 3) were exposed to increasing concentrations of nanocomposites and the minimal lethal concentration of each nanocomposite was calculated. The bioactive nanocomposites (ZIF-8/KIT-6, ZIF-8/KIT-6/Resveratrol and ZIF-8/MCM-41/Curcumin) were formulated. Anti-blastocystosis activity of the tested nanocomposites was both dose and time dependent. ZIF-8/KIT-6/Resveratol showed the maximum percentage of growth inhibition (~ 100%) at a concentration of 500 µg/ml after 5 h of exposure. More than 90% of blastocystosis cysts’ growth was significantly inhibited at all concentrations of ZIF-8/MCM-41/Curcumin, with different times of exposure, while it occurred only at the highest concentration of ZIF-8/KIT-6 (800 µg/ml). Using cheap, simple, reproducible and scalable techniques, we nano-formulated innovative bioactive nanocomposites, by incorporating the bioactive ZIF-8 (Zn2+ with imidazole), structured mesosilica and natural antioxidant compounds, curcumin or resveratrol, to generate multifunctional modalities. These eco-friendly, naturally based, safe, economical, biocompatible, and bioavailable nanocomposites are potential nanotherapeutics. The anti-blastocystosis results of these three nanocomposites indicate their potentially promising innovative and safe use as alternative Blastocystosis therapies.

CO2 Adsorption on the N- and P-Modified Mesoporous Silicas.

SBA-15 and MCM-48 mesoporous silicas were modified with functionalized (3-aminopropyl)triethoxysilane (APTES) by using the post-synthesis method, thus introducing N- and P-containing groups to the pore surface. The structure of the newly synthesized modifiers (aldimine and aminophosphonate derivatives of (3-aminopropyl)triethoxysilane and their grafting onto the porous matrix were proved by applying multinuclear NMR and FTIR spectroscopies. The content of the grafted functional groups was determined via thermogravimetric analysis. The physicochemical properties of the adsorbent samples were studied by nitrogen physisorption and UV–Vis spectroscopy. The adsorption capacity of CO2 was measured in a dynamic CO2 adsorption regime. The modified silicas displayed an enhanced adsorption capacity compared to the initial material. The 13C NMR spectra with high-power proton decoupling proved the presence of physically captured CO2. A value of 4.60 mmol/g was achieved for the MCM-48 material grafted with the Schiff base residues. The total CO2 desorption was achieved at 40 °C. A slight decrease of about 5% in CO2 adsorption capacities was registered for the modified silicas in three adsorption/desorption cycles, indicating their performance stability.

Silica-catalyzed ozonation of 17α -ethinyl-estradiol in aqueous media-to better understand the role of silica in soils

A promising route for thorough removal of 17α-ethinyl estradiol (EE2) from aqueous media was achieved through ozonation using mesoporous silicas such SBA-15, SBA-16, MCM-41 and MCM-48 as catalysts. Comparison with aluminosilicates along with Zeta potential and particle size measurements allowed demonstrating that EE2 interaction with silanols and hydrophobic –Si-O-Si– groups are essential requirements for the catalytic activity. Acid-base interactions, if any, should have minor contribution. EE2 hydroxylation appears to be an early step in the ozonation on all catalysts, but MCM-41 showed increased activity in phenolic ring cleavage. Confrontation of HPLC-UV and UV–Vis and HPLC-UV measurements revealed highest catalytic activity for MCM-41 and to a lesser extend of MCM-48 due to their higher specific surface area and weaker acid character. These results provide valuable findings for judiciously tailoring optimum [EE2-Silica:Water] interactions for thorough oxidative degradation of endocrine disrupting compounds (EDC).

Insights Into the Mn(VII) and Cr(VI) Adsorption Mechanisms on Purified Diatomite/MCM-41 Composite: Experimental Study and Statistical Physics Analysis.

In this study, a purified diatomite (PD) with a concentration of diatom frustules more than 92% SiO2 was utilized to synthesize a composite of MCM-41 silica under hydrothermal conditions. The as-synthesized PD/MCM-41 composite was characterized and tested as an adsorbent for the removal of Cr(VI) and Mn(VII) ions from aqueous solution. Results of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FTIR) revealed that the diatom frustules of the PD were coated with MCM-41 mesoporous silica. Experimental isotherms of Cr(VI) and Mn(VII) adsorption were fitted to classical and advanced statistical physics models at 25°C–55°C and pH 3. The Langmuir model estimated monolayer adsorption capacities ranging from 144.1 to 162.2 mg/g for Cr(VI) and 166.2 to 177.0 mg/g for Mn(VII), which improved with increasing the solution temperature. Steric and energetic parameters obtained from a monolayer adsorption model with one adsorption site was utilized to explain the adsorption mechanism at a microscopic level. The number of Cr(VI) and Mn(VII) ions adsorbed on PD/MCM-41 active site (n) were 1.25–1.27 for Cr(VI) and 1.27–1.32 for Mn(VII), thus suggesting multi-interaction mechanisms. The density of PD/MCM-41 active sites (D M) was a key parameter to explain the adsorption of these heavy metals. The adsorbed quantities were maximum at 55°C, thus obtaining 102.8 and 110.7 mg/g for Cr(VI) and Mn(VII), respectively. Cr(VI) and Mn(VII) adsorption energies ranged from 18.48 to 26.70 kJ/mol and corresponded to an endothermic adsorption with physical forces. Entropy, free enthalpy, and internal energy associated to the adsorption of Cr(VI) and Mn(VII) ions were calculated, thus indicating that the removal of these pollutants was spontaneous. Overall, this article offers new interpretations for the Cr(VI) and Mn(VII) adsorption mechanisms on PD/MCM-41 composite, which are relevant to contribute to the development of effective water treatment processes.

Adsorption and Catalytic Activity of Gold Nanoparticles in Mesoporous Silica: Effect of Pore Size and Dispersion Salinity.

The assembled state of nanoparticles (NPs) within porous matrices plays a governing role in directing their biological, electronic, and catalytic properties. However, the effects of the spatial confinement and environmental factors, such as salinity, on the NP assemblies within the pores are poorly understood. In this study, we use adsorption isotherms, spectrophotometry, and small-angle neutron scattering to develop a better understanding of the effect of spatial confinement on the assembled state and catalytic performance of gold (Au) NPs in propylamine-functionalized SBA-15 and MCM-41 mesoporous silica materials (mSiO2). We carry out a detailed investigation of the effect of pore diameter and ionic strength on the packing and spatial distribution of AuNPs within mSiO2 to get a comprehensive insight into the structure, functioning, and activity of these NPs. We demonstrate the ability of the adsorbed AuNPs to withstand aggregation under high salinity conditions. We attribute the observed preservation of the adsorbed state of AuNPs to the strong electrostatic attraction between oppositely charged pore walls and AuNPs. The preservation of the structure allows the AuNPs to retain their catalytic activity for a model reaction in high salinity aqueous solution, here, the reduction of p-nitrophenol to p-aminophenol, which otherwise is significantly diminished due to bulk aggregation of the AuNPs. This fundamental study demonstrates the critical role of confinement and dispersion salinity on the adsorption and catalytic performance of NPs.

MAL: High performance method for loading hydrophobic molecular materials into MCM-41 mesoporous silica – analysis of confined L-tryptophan by Raman spectroscopy

The capabilities of the recent MAL (Milling-Assisted Loading) method were analyzed for the geometric confinement of amino acids within mesoporous silica matrices. The present study has shown a high filling degree (45 wt%) of L-tryptophan into unmodified MCM-41 pores. It was shown that the low-frequency Raman spectroscopy is a suited technique to determine that molecular materials are actually confined into silica-based ordered mesoporous materials from the analysis of lattice mode region, and to probe the molecular conformation of confined materials and their interaction with the pore surface from the analysis of internal vibrations.

Architectural design of core-shell nanotube systems based on aluminosilicate clay.

A nanoarchitectural approach to the design of functional nanomaterials based on natural aluminosilicate nanotubes and their catalysis, and practical applications are described in this paper. We focused on the buildup of hybrid core–shell systems with metallic or organic molecules encased in aluminosilicate walls, and nanotube templates for structured silica and zeolite preparation. The basis for such an architectural design is a unique Al2O3/SiO2 dual chemistry of 50 nm diameter halloysite tubes. Their structure and site dependent properties are well combined with biocompatibility, environmental safety, and abundant availability, which makes the described functional systems scalable for industrial applications. In these organic/ceramic hetero systems, we outline drug, dye and chemical inhibitor loading inside the clay nanotubes, accomplished with their silane or amphiphile molecule surface modifications. For metal–ceramic tubule composites, we detailed the encapsulation of 2–5 nm Au, Ru, Pt, and Ag particles, Ni and Co oxides, NiMo, and quantum dots of CdZn sulfides into the lumens or their attachment at the outside surface. These metal–clay core–shell nanosystems show high catalytic efficiency with increased mechanical and temperature stabilities. The combination of halloysite nanotubes with mesoporous MCM-41 silica allowed for a synergetic enhancement of catalysis properties. Finally, we outlined the clay nanotubes’ self-assembly into organized arrays with orientation and ordering similar to nematic liquid crystals, and these systems are applicable for life-related applications, such as petroleum spill bioremediation, antimicrobial protection, wound healing, and human hair coloring.