Mesoporous Samples Research Articles

Eco-Friendly Synthesis of Organo-Functionalized Mesoporous Silica for the Condensation Reaction

Amine-functionalised mesoporous silica was prepared by the sonication method, a green approach. The method used aminopropyl trimethoxy silane as the amine source and tetraethyl orthosilicate as a silica source. We distinguished its performance compared to the amine-functionalised mesoporous silica sample prepared by the co-condensation method. The sonication method offered better catalytic activity. The amine-functionalised material was fully characterised by different characterisation techniques such as X-ray diffraction, FTIR, CHN, and SEM. The 12.8% of amine-functionalised material (12.A-MCM-41-S) gave excellent selectivity (98%) and conversion (95%). The activity remained almost unchanged for four cycles.

Two-step combustion synthesis of single-phase mesoporous ScFeO3 with bixbyite structure and magnetically soft behavior

In this paper, we consider the possibility of obtaining cubic bixbyite-type scandium ferrite in the form of phase-pure nanopowders. The samples were obtained by solution combustion method with either lack or excess of fuel and represented an X-ray amorphous phase according to the X-ray diffraction (XRD) results. To obtain cubic scandium ferrite, the samples were subjected to heat treatment at 700 °C, determined using DTA/TGA. The XRD data analysis confirmed the formation of cubic scandium ferrite with an average crystallite size of ∼20 nm for the sample obtained with a lack of fuel and 13 nm with an excess of fuel. According to the low-temperature nitrogen adsorption-desorption technique, the specific surface of the mesoporous samples decreased after annealing from 39.7 m2/g to 20.5 m2/g for the sample obtained with a lack of fuel and from 82.7 m2/g to 34 m2/g for the sample obtained with excess fuel. Scanning electronic microscopy (SEM) results demonstrated the foam-like morphology of nanopowders and no significant changes in their microstructure after heat treatment. The magnetic properties of powders that have undergone heat treatment have been studied. Narrow M-H hysteresis loops and low values of the coercive force indicate ferromagnetic behavior of the synthesized nanoparticles, which is supported by low values of the coercive force (Hc = 345 Oe and 769 Oe), remanent magnetization (Mr = 0.65 emu/g and 0.26 emu /g) and saturation magnetization (Ms = 1.69 emu/g and 0.26 emu/g) for lack and excess of fuel, respectively. The obtained materials are classified as magnetically soft and can potentially be used in the creation of transformers, magnetic screens, magnetic memory systems, radio engineering, and computer technology.

Bimodal mesoporous CeO2–ZrO2-based materials prepared by PMMA nanosphere assisted co-precipitation and its thermal stability

Bimodal mesoporous CeO2–ZrO2-based materials (CZP) are designed and prepared for high specific surface area and thermal stability. CZP is prepared by co-precipitation method and with the help of poly(methyl methacrylate) (PMMA) nanospheres. Its specific surface area reaches 93.8 m2/g higher than 54.8 m2/g of the unimodal mesoporous sample prepared without PMMA nanospheres (CZ). The pores of CZP are in the range of 2–100 nm and concentrate at 4 nm and 14 nm. CZ has narrowly distributed pores ranging from 2 nm to 8 nm. PMMA nanospheres have little effect on the crystal structure of the CeO2–ZrO2-based materials. Compared to CZ, CZP shows higher thermal stability. The specific surface area of CZP is higher than that of CZ at 800 °C. At 1000 °C, CZP is sintered to sponge-like morphology with pores over 100 nm, while CZ is sintered to dense solid granular morphology. The influence of PMMA nanospheres on oxygen storage capacity (OSC) and redox properties is in line with the changes in specific surface area. In addition, 1000 °C aged CZP presents better three-way catalysts (TWC) performance compared to CZ because of the porous sponge-like morphology of CZP.

Hydrate formation in mesoporous materials: Thermodynamic modeling and experimental investigations

Until recently, analysis and interpretation of the equilibrium conditions of hydrate formation from water adsorbed in mesoporous materials have been carried out with the use of the Gibbs-Thomson equation. For this purpose, only the shift of equilibrium conditions due to the small size of hydrate particles formed in the confining pores was taken into account. A distribution of equilibrium temperatures of the hydrate formed in mesoporous materials was interpreted as a consequence of the existence of hydrate particles differing from each other in size. A new equation describing the equilibrium conditions for gas hydrate in thin pores of mesoporous materials is proposed in this work. This equation takes into account the size of hydrate particles together with the chemical potential of pore water in equilibrium with the hydrate. Thus, an increase in the temperature shift from the equilibrium curve causes simultaneous formation of hydrate in smaller and smaller pores, and an increase in the size of gas hydrate particles that have been previously formed in larger pores. The latter occurs due to gradual transformation into hydrate of the layer of bound water, located between the pore wall and hydrate particle being formed in the pore center. Modeling results are compared with the data obtained previously on the equilibrium conditions for the hydrate of carbon dioxide in mesoporous Al2O3 samples. It is demonstrated that experimental results are in reasonable qualitative agreement with the proposed model.

Repeatable catalyst, repeat customers

Mesoporosity was introduced into high-silica ZSM-5 zeolite (SiO2/Al2O3 = 417) by controlled desilication using the mixture of NaOH and TEAOH (tetraethylammonium hydroxide), and subsequent phosphorus modification was used to improve the structural stability and acidity reservation of the desilicated ZSM-5 samples during the procedure of severe steam aging treatment. The phosphorus modified mesoporous ZSM-5 sample along with parent ZSM-5, solo phosphorus modified ZSM-5 and mesoporous ZSM-5 were characterized by techniques of N2 adsorption-desorption, NH3-TPD (temperature programmed desorption), IR (infrared) spectroscopy of pyridine adsorption and 27Al & 31P MAS NMR spectroscopy. A mechanism for underlying chemistry of the combinative treatment was proposed. The aluminophosphate formed in the steam activation could interact with the framework aluminum on zeolite, thus achieved to the textural and acidity stabilization during the steam aging. The catalytic performance of these samples was tested by different hydrocarbon cracking reactions. It turned out that owing to its reduced diffusion limitation and stabilized acidity, the phosphorus modified mesoporous ZSM-5 sample exhibited the highest conversion in the bulky molecule cracking reaction. And in the 1-octene cracking reaction under harsh reaction conditions, the steamed phosphorus modified mesoporous ZSM-5 sample exhibited higher activity and more prolonged catalyst life compared to the other steamed catalysts, which could be attributed to the improved coke tolerance capability by mesoporosity introduction and the stabilized acid sites by phosphorus modification.

Converting polar silicon surfaces of ordered mesoporous materials to non-polar carbon surfaces for enhanced carbon dioxide capture

The ordered mesoporous carbon-silica composite samples were synthesized by the unremoved template agent (P123) or together with additional sucrose as carbon sources. The effects of sulfuric acid and sucrose added on the properties of the synthesized materials were discussed. Ordered mesoporous structures of the synthesized materials were examined by XRD, TEM, and the 77 ​K N2 adsorption-desorption isotherms characterization. Compared to the silicon SBA-15 sample, the pore walls of carbon-silica composite materials were covered with carbon film, so their pore sizes became smaller and their surface properties were changed from polarity to hydrophobicity. The capturing CO2 performances on two dry/wet carbon-silica samples (SC-1.5, SCC-2) were collected at 275 ​K. Whether or not pre-adsorbed water, the CO2 adsorption capacities of the carbon-silica composite samples were higher than that of SBA-15. For the wet SC-1.5 sample with the mass ratio water/dry sample (Rw) of 3, the capturing CO2 capacity was 32 ​mmol/g at the pressure of 3 ​MPa. The H2O/CO2 mole ratios of the wet SC materials under different Rw were all lower than the theoretical value (5.75). The mechanisms of capturing CO2 on wet carbon-silica composite materials were multiple, which included CO2 dissolution in water, CO2 adsorption in pore space, and CO2 gas hydrate formation. The suddenly increasing CO2 adsorption capacity on the wet SC-1.5 material was mainly due to the formation of CO2 gas hydrates in its pore spaces.

The investigation of adsorption desulphurization performance using bimetallic Cu[sbnd]Ce and Ni[sbnd]Ce mesoporous Y zeolites: Modification of Y zeolite by H4EDTA-NaOH sequential treatment

The microporous structure of Y zeolite strongly affects the function of adsorption desulphurization, especially when resistant compounds are present in fuel. The goal of this paper was to enhance a novel, hierarchically structured bimetal Y zeolite and to investigate the adsorption desulphurization performance from different model fuels that included toluene as a competitor. Mesoporosity was introduced in Y zeolite by the dealumination-desilication process with different concentrations of EDTA and NaOH to improve the pore structure. The synthesized samples were characterized by means of XRD, BET, FE-SEM, FT-IR, EDX and UV techniques. In the following, bimetallic CuCe and NiCe were impregnated on parent Y zeolite and mesoporous samples to increase the adsorption capacity. The prepared meso-CuCe and meso-NiCe were characterized and measured in the term of adsorption desulphurization with different model fuels contained thiophene and dibenzothiophene. The results showed that meso-NiCe increased the adsorption capacity of thiophene and dibenzothiophene up to 24.4 and 27.5 mg/g, respectively, which were almost 4.1 times more than the parent Y zeolite and after two cycles of regeneration by thermal method, the adsorption capacity hardly decreased. In addition, effect of toluene, initial concentration, time, and temperature were investigated on the adsorption capacity of the adsorbents.

Novel BiVO4/ZnO heterojunction for amended photoreduction of mercury (II) ions

In this research, mercury (II) ions were eliminated via photocatalytic reduction under visible light utilizing BiVO4/ZnO heterojunction. Different percentages of BiVO4 NPs were distributed uniformly over mesoporous ZnO surface. It has been demonstrated by TEM analysis that both pure mesoporous ZnO sample and the heterojunction containing 3 wt% BiVO4 NPs consist of almost homogenous spherical particles of about 25 nm diameter. The progressed BiVO4/ZnO nanocomposite containing 3 wt% BiVO4 NPs was able to accomplish comprehensive elimination of mercury (II) ions via photocatalytic reduction under visible light owing to its significant capacity to absorb light in visible region. Such heterostructure achieved almost complete (100%) photocatalytic proficiency towards mercury (II) ions reduction by the end of 45 min from the illumination by visible light. The photo-reduction rate of Hg2+ ions via practicing BiVO4/ZnO nanocomposite containing 3 wt% BiVO4 NPs was estimated at 14 times when related to that of pure mesoporous ZnO. The successful development of p-n heterojunction between ZnO (n-type) and BiVO4 (p-type) in addition to the accessible great surface area and the remarkable visible light absorption provided by such heterojunction could be regarded as the dominant causes of the distinct photo-reduction rate of Hg2+ ions. The heterojunction afforded via incorporating BiVO4 with ZnO facilitated the separation between the created charges and hindered the rate of the recombination between such charges as well.

High hydrothermal stability of mesoporous Ni-phyllosilicate spherical particles

We report mesoporous nickel-phyllosilicate spherical particles with very high hydrothermal stability. Mesoporous nickel-silica samples were prepared with a surfactant by a facile one-pot sol-gel reaction under ammonia basic conditions. Ni/Si molar ratio was adjusted as 0.3, 1, and 9. Hydrothermal stability was investigated inside distilled water at 100 °C both under a static condition inside a convection oven for 8 weeks and a reflux condition for 4 weeks. The crystal structure of mesopore framework was analyzed using X-ray diffraction before and after the hydrothermal treatment. Spherical particle shape and pore characterization were thoroughly investigated using transmission- and scanning electron microscopy as well as nitrogen adsorption-desorption isotherm after the hydrothermal treatment. Thermal stability and elemental electronic state were also analyzed using thermogravimetric analyzer and X-ray photoelectron spectroscopy. In this work, it is strongly suggested that mesoporous nickel-phyllosilicate particles can be used as a reusable catalyst and a versatile catalytic support material in various chemical industry including oil company.

Characterization and modeling of the temperature-dependent thermal conductivity in sintered porous silicon-aluminum nanomaterials

Nanostructured silicon and silicon-aluminum compounds are synthesized by a novel synthesis strategy based on spark plasma sintering (SPS) of silicon nanopowder, mesoporous silicon (pSi), and aluminum nanopowder. The interplay of metal-assisted crystallization and inherent porosity is exploited to largely suppress thermal conductivity. Morphology and temperature-dependent thermal conductivity studies allow us to elucidate the impact of porosity and nanostructure on the macroscopic heat transport. Analytic electron microscopy along with quantitative image analysis is applied to characterize the sample morphology in terms of domain size and interpore distance distributions. We demonstrate that nanostructured domains and high porosity can be maintained in densified mesoporous silicon samples. In contrast, strong grain growth is observed for sintered nanopowders under similar sintering conditions. We observe that aluminum agglomerations induce local grain growth, while aluminum diffusion is observed in porous silicon and dispersed nanoparticles. A detailed analysis of the measured thermal conductivity between 300 and 773 K allows us to distinguish the effect of reduced thermal conductivity caused by porosity from the reduction induced by phonon scattering at nanosized domains. With a modified Landauer/Lundstrom approach the relative thermal conductivity and the scattering length are extracted. The relative thermal conductivity confirms the applicability of Kirkpatrick’s effective medium theory. The extracted scattering lengths are in excellent agreement with the harmonic mean of log-normal distributed domain sizes and the interpore distances combined by Matthiessen’s rule.

Mesostructured Zn/ZSM‐5 Zeolite as Catalyst for Furan Deoxygenation,

AbstractThe furan conversion into aromatics over zinc promoted ZSM‐5 zeolites was studied in a continuous‐flow fixed‐bed reactor. Two series of microporous and mesoporous catalysts were prepared at different zinc loadings of 2 and 5 wt.%. It was intended to optimize the overall aromatics production and control coke accumulation over novel synthesized mesoporous ZSM‐5 catalyst, in a continuous flow reactor. The catalysts were characterized using X‐ray diffraction (XRD), nitrogen adsorption/desorption, ammonia temperature programmed desorption (TPD) and X‐ray photoelectron spectroscopy (XPS). The zinc loaded mesoporous materials exhibit an XRD pattern that matches with the ZSM‐5 XRD reference pattern. No extra peaks were observed in the XRD results indicating the high dispersion of zinc species. The initial furan conversion rate was higher over the microporous catalysts, and increased upon increasing metal loading, however contrary to the mesoporous samples, the microporous ones deactivated rapidly over 2 hours of time on‐stream. The results indicated that around 40 % of carbon in the fed furan, was recovered in aromatics when the new mesostructured zeolite catalyst was used, whereas this could be further increased to 50 % by the addition of zinc in the catalyst, benzene being the major product.

Advances in the understanding of mesoporous transition aluminas: Unveiling the correlation between morphology and thermostability

The thermostabilities of mesoporous γ-Al2O3 samples with similar initial surface areas and average pore radii, but significantly different pore volumes, were studied in detail. The results show that γ-Al2O3 with highest initial pore volume converts to α-Al2O3 at a significantly higher temperature, along with larger residual surface area and pore volumes after aging. These observations are directly related to the morphologies of the individual particles and the resulting aggregate structures, which were studied by automated crystallite orientation mapping (ACOM-TEM). Large particles with well-developed plate-like morphologies preferentially form dense stacks by assembly via the {110} main basal planes (pseudo-cubic lattice). This arrangement favors sintering and the formation of α-Al2O3 at comparatively low temperatures. Aluminas with higher proportions of the lateral {100} and {111} facets tend to form aggregate structures with higher porosities and lower interparticle contact areas, thus explaining their superior thermostabilities. These findings highlight the importance of the aggregate structure for the purposeful development of alumina-supported catalysts.

In Vitro Study of Doxorubicin Nanomedicine for Gastric Cancer Cells

In order to study the performance of doxorubicin nanomedicine on gastric cancer cells, the prepared mesoporous silica nanoparticle samples and the doxorubicin hydrochloride solution samples of different concentrations were synthesized and prepared to concentrations of 0.01 mg/ml and 0.03 mg/ml, 0.05 mg/ml, 0.07 mg/ml and 0.09 mg/ml respectively. Doxorubicin hydrochloride-loaded mesoporous silica nanoparticles samples were applied to the cultured gastric cancer cells. Through transmission electron microscope, specific surface area and pore size distribution analyzer, ultraviolet spectrophotometer and other instruments, test the morphology, surface area, pore volume and average pore size, drug release performance and adsorption of mesoporous silica nanoparticles samples loaded with doxorubicin hydrochloride- desorption performance, drug loading, drug loading and encapsulation rate, and gastric cancer cell survival rate, etc., so as to conduct in vitro research and analysis of doxorubicin drugs for gastric cancer cells. The test results show that mesoporous silica nanoparticles samples are suitable for drug delivery, with high drug loading and encapsulation rate and drug controlled release effect as the acidity of the buffer increases, it is beneficial to the release of drugs in the slightly acidic environment of the tumor site; mesoporous silica nanoparticles, the drug loading of the sample after three times of ultrafiltration is about 55 % and the encapsulation efficiency is above 90 %; as the sample concentration increases, the survival rate of gastric cancer cells gradually decreases. This shows that doxorubicin nanomedicine can be used to inhibit gastric cancer cells and can assist in the treatment of gastric cancer.

Afterglow luminescence phenomena in the porous anodic alumina

A series of mesoporous alumina layers obtained by anodic oxidation in solutions of H 2 SO 4 , H 3 PO 4 and H 2 C 2 O 4 were subjected to spectroscopic studies. Their photoluminescence was investigated mainly by the afterglow luminescence (A-Lum) method using a low-pressure mercury lamp emitting at 254 nm as the source of excitation. All mesoporous alumina samples (PAA) showed short-time emission (a few to a few 10 s) of biexponential decay. The intensity and shape of the emission spectra were proved to depend on the thermal treatment of Al/AL 2 O 3 samples, type of electrolyte used in their synthesis and excitation time. On the basis of the determined kinetic parameters of emission decay curves and emission spectra, significant differences were found between the A-Lum and photoluminescence phenomena for all systems studied. • Detection of afterglow luminescence of porous structures of amorphous alumina. • Analysis of the emission spectrum and kinetic curves of the A-Lum decay.

Fenton Stability of Mesoporous Ceria-Silica and Its Role in Enhanced Durability of Poly(arylene ether sulfone) Multiblock Copolymer Composite Membranes for Perfluorosulfonic Acid Alternatives.

To increase the stability of cerium scavengers, we doped cerium oxide on mesoporous silica powders for the application of an oxidative stabilizer. The oxidation–reduction reaction involving hydroxyl radicals (•OH) is investigated with Fenton’s test using eight types of Ce(IV)-mobile compositions of matter 41 (MCM-41) and Ce(III)-MCM-41 powder samples. As confirmed by X-ray photoelectron spectroscopy, the relative amount of Ce3+ inside the mesoporous samples decreases with the increasing time of treatment using the Fenton solution, whereas that of Ce4+ increases. 29Si CP-MAS NMR shows that the condensation of the siloxane bond varies according to the treating time up to 120 h. The mesoporous structure is also analyzed using synchrotron small-angle X-ray scattering and nitrogen adsorption. Further treatment with propane sulfonic acid ensured that the ionic conductivity of the sulfonated mesoporous silica did not decrease. The surface-modified mesoporous silica was incorporated in sulfonated poly(arylene ether sulfone) multiblock membranes. The sulfonated mesoporous silica could overcome the drawbacks of transition metal scavengers, such as a drop in ionic conductivity. Through experiments, we determined that the Ce-doped sulfonated mesoporous silica/sulfonated poly(arylene ether sulfone) composite membranes exhibit high oxidation stability when exposed to hydrogen peroxide and even higher proton conductivity than Nafion at a relative humidity over 60%.

Comparisons of visible-light driven photocatalytic CO2 conversion performances over mesoporous CdSxSe1–x with different molecular compositions

This study presents a synthesis method for nanowire arrayed mesoporous CdSxSe1-x compounds with different S/Se molar ratios. Both ternary and binary compound semiconductors are synthesized by hard-templating using SBA-15 as a silica template. The synthesized mesoporous materials have high specific surface areas of approximately 65–100 m2 g−1 and remarkable light absorption properties in the UV to visible light region (1.7–2.4 eV), and thus they are appropriate for the photo-conversion of CO2 into CO and CH4. The results show that the compositions of CdSxSe1-x excellently agree with the compositions of the reactants. Moreover, the band gaps of the mesoporous CdSxSe1-x samples could be directly tuned by varying the composition of the reactants. It is concluded that mesoporous CdSe achieves the highest CH4 yield rate, i.e., 0.382 μmol gcat–1 h–1, and CdS0.5Se0.5 achieves the highest CO yield rate (among all the samples synthesized), i.e., 5.633 μmol gcat–1 h–1. Also, it is found that the CO2 photoconversion performance on mesoporous II-VI photocatalyst are highly affected by CO2 adsorption capacities and photo-generated charge separation.

Mesoporous Carbon Xerogels Adsorbents for Adsorption of Cadmium and p-Nitrophenol Pollutants: Kinetic and Equilibrium Studies

Mesoporous carbon xerogels were prepared by carbonization of resorcinol-formaldehyde xerogel in presence of tannic acid as a soft-template at 700oC for 30, 60 and 90 min, respectively. Morphology, textural, surface functional surface groups and thermal analyses were measured. Their efficiency in liquid-adsorption of cadmium ions and PNP in a batch mode was carried out. Effect of some key factors such as pH, carbon dose, and contact time of cadmium ions and PNP as well as kinetic adsorption studies were performed. It was found that the obtained carbon xerogels of mesoporous structure have a moderate total surface area reached to 268 m2/g with various surface functional groups are effective sites for adsorbing cadmium ions and PNP from aqueous solutions. The adsorption behavior of both adsorbates on the prepared carbon samples was best described by the pseudo-second-order kinetic and Langmuir adsorption models. The maximum adsorption capacities of cadmium ions and PNP were 99 and 133 mg/g, respectively; onto the prepared carbon xerogel at 700oC and 60 min. As a result of these observations, the produced mesoporous carbon samples are very effective adsorbents for extracting considerable amounts of cadmium ions and PNP from aqueous solutions.

ON THE TRANSITION BETWEEN FERROMAGNETIC AND PARAMAGNETIC STATES IN MESOPOROUS MATERIALS WITH FRACTAL MORPHOLOGY

In this paper, we have shown how the presence of pores and pore morphology influence on magnetic phase transition temperatures in mesoporous ferromagnetic materials. Model calculations have demonstrated the possibility to obtain macroscopic mesoporous samples with notably reduced Curie temperatures which is also further depressed in the case the pore morphology is more complicated. The results have been obtained on the basis of the experimentally verified correlation between the Curie temperature and cohesive energy of the material and illustrated using the examples of pure mesoporous iron, nickel and cobalt while pore morphology has been determined by the methods of fractal geometry. Several practical applications of mesoporous materials with tuned values of the Curie temperature have also been discussed in the final section.

Driving Force of Molecular/Ionic Superfluid Formation

Driving Force of Molecular/Ionic Superfluid Formation

Milk derived highly ordered mesoporous carbon with CaF2 nanoclusters as an efficient electrode for supercapacitors

Here we report on the synthesis of highly ordered nanoporous carbon decorated with CaF2 nanoclusters along the pore wall structure using dairy milk as a carbon and calcium source through nano-hard templating approach wherein mesoporous silica SBA-15 with different pore diameters are used as template. CaF2 is introduced during the removal process of silica template and can help to enhance the charge transfer. Nitrogen adsorption results reveal that the prepared materials exhibit high specific surface area with bimodal porous structures which act as a media for the rapid ion transports through the regular and interconnected micro- and mesoporous structure. The mesoporous carbon samples also exhibit hexagonally ordered pores with rod shaped morphology, which is similar to that of the template, confirming that the templating process is successful. Finally, the optimised electrode is highly stable and offers the capacitance of 182 F g−1 at 0.5 A g−1 with almost 100% retention rate even after 5000 cycles due to a strong intimate coupling generated by the CaF2 nanoclusters within the wall structure. The electrode performance of milk derived carbon samples is much better than that of activated carbon, multiwalled carbon nanotubes and the mesoporous carbons without CaF2.