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Sökning: L773:1387 1811

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1.
  • Flodström, Katarina, et al. (författare)
  • Influence of the block length of triblock copolymers on th formation of mesoporous silica
  • 2003
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811. ; 59:2-3, s. 167-176
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of different block lengths of Pluronic surfactants, (EO)(x)-(PO)(y)-(EO)(x), in the formation of mesoporous silica has been investigated. The syntheses were performed in micellar solution of the surfactant under acidic conditions. The materials were characterized by SAXS, TEM and nitrogen adsorption measurements. The EO-block length of the polymers determines the mesostructure of the silica. For the hexagonal material (SBA-15) the wall thickness is largely dependent on the length of the EO-blocks, while the PO-block length has a great effect on the pore diameter. Furthermore, the PO-block length influences the templating ability, as longer PO-blocks result in more highly ordered domai s and well defined particles. The synthesis temperature also influences these parameters. (C) 2003 Elsevier Science Inc. All rights reserved.
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2.
  • Lundberg, Mats, et al. (författare)
  • Mesoporous thin films of high-surface-area crystalline cerium dioxide
  • 2002
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811. ; 54:1-2, s. 97-103
  • Tidskriftsartikel (refereegranskat)abstract
    • Mesoporous thin films of cerium dioxide were prepared by using a copolymer surfactant (Pluronics 123) at ambient conditions in alcohol as a solvent. The material was produced via a direct calcination step, without the necessity of a gelling stage. The synthesised CeO2 matrix was crystalline with a high surface area. The solution height over the synthesis vessel before the calcination step was found to play an important role in the direct calcination synthesis of mesoporous ceria. The material was characterised by scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, and determination of the specific surface area after the BET method. Small angle X-ray scattering was used to study differences in how the surfactant with ethanol as a solvent was ordered before and after addition of cerium chloride, prior to the calcination step.
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3.
  • Engström, V., et al. (författare)
  • The effect of seed size on the growth of silicalite-1 films on gold surfaces
  • 2000
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 38:1, s. 51-60
  • Tidskriftsartikel (refereegranskat)abstract
    • Silicalite-1 films grown on gold surfaces seeded with colloidal crystals with a size of 60, 165 and 320 nm were investigated by reflection–absorption infrared spectroscopy, scanning electron microscopy and X-ray diffraction in order to follow up the formation of nano-scale defects and to determine the optimal synthesis conditions for preparation of silicalite-1 films with a low concentration of defects. Using 60-nm-sized colloidal crystals, the seeding method was capable of producing silicalite-1 films with low concentrations of defects and with thicknesses ranging from 100 to 300 nm, which are predominantly oriented with the a-axis perpendicular to the surface. Hydrothermal treatment times of the 60-nm-seeded surfaces longer than 36 h as well as the seeding with 165 or 320 nm colloidal crystals substantially enhanced the formation of defects in the films.
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4.
  • Ganemi, B., et al. (författare)
  • Zeolite Cu-ZSM-5 : material characteristics and NO decomposition
  • 2000
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 38:2-3, s. 287-300
  • Tidskriftsartikel (refereegranskat)abstract
    • Zeolite ZSM-5 (SiO2/Al2O3 ratio 53:1) ion exchanged with Cu2+ to 0%, 74% and 160% was characterized by X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Infrared (IR) spectroscopy, Electron spectroscopy for chemical analysis (ESCA) and ammonia desorption. A more limited set of data was obtained for Cu-ZSM-5-33, ion exchanged with 0%, 104% and 210% Cu2+ ions. All catalysts lose water below 100°C. More strongly bound water, approximately two molecules per Cu2+ ion, emerge at a higher temperature. This corresponds either to an incomplete hydration shell for zeolite-bound Cu2+ ions or to the decomposition of Cu(OH)2 and simultaneous reactive adsorption of copper ions on the inner surface of the zeolite. The process occurs in the same temperature range, 150-350°C, where XRD reveals rearrangements in the H-form of the catalyst. Reactions between the exchangeable cations and the zeolite appear critical for lattice changes and possibly the formation and dispersion of catalytically active centers at these temperatures. Dehydroxylation and water desorption are observed between 350°C and 450°C for H-ZSM-5. This temperature range overlaps with the light-off temperature for direct NO decomposition over Cu-ZSM-5. This coincidence can be rationalized in terms of two effects of enhanced ionic mobility and dynamics of the zeolitic framework. ESCA shows that partial reduction, cupric to cuprous, occurs as a result of annealing in the same temperature range. It has been suggested that NO-derived surface intermediates act as site blockers for the direct decomposition below the light-off temperature until destabilized by lattice movements. The lower stability and thus higher mobility of low SiO2/Al2O3 ratio ZSM-5 zeolites would then rationalize an advantage of these materials as supports in catalysts for direct NO decomposition.
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5.
  • Hedlund, Jonas, et al. (författare)
  • Controlling the preferred orientation in silicalite-1 films synthesized by seeding
  • 1999
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 28:1, s. 185-194
  • Tidskriftsartikel (refereegranskat)abstract
    • Single crystal silicon (100) wafers were seeded with colloidal silicalite-1 crystals and hydrothermally treated in a precursor solution to grow thin silicalite-1 films. A total of 28 experiments in eight series were investigated with SEM and XRD to evaluate the preferred orientation of the crystals constituting the films. The investigated parameters in the film formation process were seed crystal size, amount of adsorbed seed crystals and film thickness after hydrothermal treatment of the seeded substrates. In thin films, most of the crystalline material is oriented with the b-axis perpendicular to the substrate surface. In thick films, most of the crystalline material is oriented with the a-axis perpendicular to the substrate surface. The change in preferred orientation with film thickness is faster when small seeds are used. The amount of adsorbed seeds has a larger influence on the preferred orientation when large seeds are used. A mechanism explaining these trends is proposed. The choice of size and coverage of seeds can be used to control the preferred orientation of the crystals in a film of given thickness within certain limitations.
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6.
  • Hedlund, Jonas, et al. (författare)
  • High-flux MFI membranes
  • 2002
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 52:3, s. 179-189
  • Tidskriftsartikel (refereegranskat)abstract
    • The synthesis and evaluation of high performance MFI-type membranes is described. These systems exhibit fluxes that are one to two orders of magnitude higher than previous literature reports, with comparable selectivities, when tested for various single component gases and for mixtures of C4, C6 and xylene isomers.These materials are the result of a rational fabrication approach targeting ultra-thin, defect-free MFI films on open supports by using a two-step support masking technique and a monolayer of colloidal nucleation seeds, followed by in situ hydrothermal growth, producing a defect-free film with a thickness of 0.5 μm. Reproducibility of the membrane preparation was excellent.
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7.
  • Lassinantti, Magdalena, et al. (författare)
  • Faujasite-type films synthesized by seeding
  • 2000
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 38:1, s. 25-34
  • Tidskriftsartikel (refereegranskat)abstract
    • Thin and continuous Faujasite-type films were synthesized on α-alumina wafers using a seeding technique. Surface modified wafers were seeded with colloidal zeolite Y crystals prior to film growth in a synthesis mixture. The effects of hydrothermal treatment on film thickness, morphology and preferred orientation of the crystals constituting the film were investigated using scanning electron microscopy and X-ray diffraction. During hydrothermal treatment a precipitate formed rapidly, leaving an almost clear solution in the upper part of the reactor. Experiments at 60–100°C were performed with the sample placed in the upper part of the synthesis solution. An increase in the film growth rate with increasing temperature was observed. Adsorbed seeds were shown to be oriented with the {1 1 1} pyramid, parallel to the substrate surface. A change in the orientation with film growth was noted, probably due to the attachment of secondary crystals to the growing film surface. In one experimental series, film growth was effected at the bottom of the tube at 100°C. Faster film growth and multilayered films were obtained. A decrease in the film thickness after prolonged hydrothermal treatment was observed in all experimental series. This is probably due to the dissolution of the film and formation of zeolite P in the synthesis solution. The thicknesses of the films synthesized in this work are in the range of 150–2700 nm. The films are promising candidates for use in membrane applications.
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8.
  • Li, Q., et al. (författare)
  • Nucleation period for TPA-silicalite-1 crystallization determined by a two-stage varying-temperature synthesis
  • 1999
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 31:1, s. 141-150
  • Tidskriftsartikel (refereegranskat)abstract
    • A two-stage-varying-temperature synthesis procedure, which involves a rapid change in temperature at some point during the course of crystallization, was applied to the synthesis of discrete colloidal particles of TPA-silicalite-1. As the duration of the period at the initial synthesis temperature was extended, the crystal concentration and ultimate crystal size varied until they were approximately equal to those obtained for a complete synthesis at the initial temperature. At this point in the crystallization, it was concluded that the nucleation stage was completed. For syntheses performed at 60, 80 and 100°C, the duration of the nucleation period determined by this method was about 100 h, between 4 and 6 h and less than 2 h, respectively. Thus, nucleation, for this system, is a continuous process, and it was found that the rate of nucleation, which is initially high, declines, throughout the nucleation period. In all cases, nucleation occurred during an induction period when little or no crystal growth was observed, which explains why the syntheses yielded a product with a rather narrow crystal size distribution. If, for the two-stage syntheses, the temperature change was made after completion of the nucleation period, the second synthesis temperature controlled only the linear growth rate of the crystals and the final yield of silicalite-1 obtained
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9.
  • Li, Qinghua, et al. (författare)
  • Synthesis and characterization of zoned MFI films by seeded growth
  • 2002
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 56:3, s. 291-302
  • Tidskriftsartikel (refereegranskat)abstract
    • Supported zoned and sandwiched MFI films were prepared by a two-step crystallization procedure, using seeds. In this work, a zoned MFI film is defined as one assembled by crystals propagating from the support to the film top surface with varying Al content along the length of the crystal. A sandwiched MFI film is referred to as one assembled by at least two layers of crystals. Six types of films were prepared, both zoned and sandwiched, with a high or a low Al-content in the ZSM-5 part and with varying order of the layers, i.e. ZSM-5 coated with silicalite-1 or vice versa. The films were characterized by SEM and TEM. The Al-distribution was measured by cross-sectional EDS, and the preferred orientation of the crystals could be determined by XRD. Truly zoned films are obtained when the compositional difference between the layers is relatively small, and the synthesis conditions are similar or when the first layer is silicalite-1. If the first layer is ZSM-5 and the synthesis conditions and/or the composition vary too much, a discontinuity occurs at the interface between the layers, and sandwiched film results, where nucleation of the second layer is initiated by secondary nucleation or by applying seeds.
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10.
  • Li, Qinghua, et al. (författare)
  • The nucleation period for crystallization of colloidal TPA-silicalite-1 with varying silica source
  • 2000
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 40:1-3, s. 53-62
  • Tidskriftsartikel (refereegranskat)abstract
    • The effect of varying silica source on the nucleation and crystallization of TPA-silicalite-1 was investigated. A direct experimental method, involving a two-stage varying-temperature synthesis, was used to determine the nucleation period for colloidal crystals of TPA-silicalite-1 with different silica sources, including tetraethoxysilane (TEOS) and amorphous silica (Ludox TM and Ludox LS). For syntheses performed at 60°C with TEOS as silica source, the duration of the nucleation was about 72 h, and a very rapid increase in the crystal population occurred during the initial crystallization time. However, with the amorphous silica sources (Ludox TM or Ludox LS), the duration of the nucleation period was extended to about 120 h, and the nucleation profile consisted of a self-accelerating nucleation rate at the beginning of the nucleation period. The two-stage synthesis method could be used to determine the nucleation profile for the various silica sources. However, this technique overestimated the crystal concentration at the earliest stage of nucleation with amorphous silica. The use of amorphous silica gave rise to a broader crystal size distribution compared to that of TEOS. However, it was found that for both TEOS and amorphous silica the vast majority of the nucleation occurred during an induction period when little or no crystal growth was observed. In addition, Raman spectroscopy revealed structural differences between Ludox TM and Ludox LS which may account for differences in the nucleation processes observed for these two amorphous silicas.
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11.
  • Mihailova, B., et al. (författare)
  • Vibrational spectroscopy study of the structure of silicalite-1 films on a gold surface
  • 1999
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 32:3, s. 297-304
  • Tidskriftsartikel (refereegranskat)abstract
    • The structure of silicalite-1 films grown on seeded gold surfaces is investigated by modelling the observed changes in the infrared reflection absorption (IRRA) spectra of samples treated for different times in the synthesis solution. The results show that a gradual deformation of the five-membered silicon-oxygen rings occurs during the first 11 h of the hydrothermal treatment which leads to breaking of Si---O---Si linkages and to formation of linear defects along the c-axis. Interactions between the dislocations and the grain boundaries during the further growth of the film provoke the appearance of void spaces in the grain boundary interface which may cause incipient cracking in the silicalite-1 films on seeded gold surfaces. The range 1000-1300 cm-1 in the IRRA spectra is found to be appropriate for estimating the quality of silicalite-1 films grown on metal surfaces.
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12.
  • Naydenov, Valeri, et al. (författare)
  • Spherical silica macrostructures containing vanadium and tungsten oxides assembled by the resin templating method
  • 2002
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 55:3, s. 253-263
  • Tidskriftsartikel (refereegranskat)abstract
    • Silica-based spherical macrostructures containing vanadium and tungsten oxides were prepared using anion exchange resin beads as a shape-directing macrotemplate in a multi-step procedure. In a first step resin beads were treated with a clear and homogeneous TPA-silicate synthesis solution at 170 °C for three different times and resin-silicate composites were obtained. Short treatment times resulted in amorphous silica whereas the longest time yielded highly crystalline silicalite-1. In a second step anionic vanadium or tungsten species were introduced into the resin-silicate composites by utilization of the residual ion exchange capacity of the resin. In a final step the ion exchange resin was removed by calcination leaving behind vanadium- or tungsten-containing silica spheres. The influence of the concentration and the pH of the solutions used for vanadium and tungsten ion exchange on the properties of the final spheres was investigated. The product particles were extensively characterized by XRD, SEM, AAS, nitrogen adsorption measurements, Raman and UV–vis diffuse reflectance spectroscopy. Generally, the nature of the metal species formed within the spheres was isolated and highly dispersed monomers in tetrahedral coordination in amorphous samples and V2O5 or WO3 crystallites in crystalline ones.
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13.
  • Qinghua, Li, et al. (författare)
  • Aging effects on the nucleation and crystallization kinetics of colloidal TPA-silicalite-1
  • 2001
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 43:1, s. 51-59
  • Tidskriftsartikel (refereegranskat)abstract
    • A direct experimental method, involving a two-stage varying-temperature synthesis, was utilized to investigate the effects of aging on the nucleation kinetics for the synthesis of nanosized TPA-silicalite-1 with various silica sources, including tetraethoxysilane (TEOS) and amorphous silica Ludox TM. For TEOS aging had only a mild influence on the nucleation and crystallization kinetics, whereas for Ludox TM dramatic changes occurred. After extended aging periods, the nucleation kinetics for syntheses with Ludox TM became similar to those for syntheses with TEOS, leading to increasing similarities in the properties of the products of the crystallization. Independent of aging time and silica source, the nucleation processes occurred over a substantial period of time, extending over the induction period, but were completed before crystal growth was detected. With increased aging, the nucleation period was gradually decreased and tended to be completed earlier in the induction period. Raman spectra revealed that with Ludox TM, aging enhanced the interaction between TPA+ and the silica species, leading to an increase in the concentration of precursor species for nucleation, which in turn accelerated the nucleation rate.
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14.
  • Schoeman, Brian J. (författare)
  • Analysis of the nucleation and growth of TPA-silicalite-1 at elevated temperatures with the emphasis on colloidal stability
  • 1998
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 22:1-3, s. 9-22
  • Tidskriftsartikel (refereegranskat)abstract
    • The question as to whether silicalite-1 grows via an aggregation of smaller particles or similar sized particles has been addressed by considering the fundamentals governing colloidal stability - the quantitative theory underlying colloidal stability being given by the extended Derjaguin-Landau and Verwey-Overbeek (DLVO) theory. Application of the extended DLVO theory to discrete colloidal particles in silicalite-1 precursor sols shows that a net repulsive interactive energy exists between the negatively charged particles. The thermal energy of the colloidal particles (1/2kT at 373 K, the crystallization temperature) is not sufficient to overcome the net repulsive energy barrier. The extended DLVO theory has been applied to two growth scenarios with similar results: growth by aggregation of particles of very different sizes and growth by aggregation of similar sized particles. The significance of these conclusions is that a proposed growth mechanism of MFI type zeolite (growth by aggregation of subcolloidal particles) is deemed not to be a reasonable description of molecular sieve growth. The conclusion that the colloidal crystals are stable with respect to aggregation is supported by experimental observations. The ideas presented in this study are based upon crystallization of molecular sieves from clear solutions in the presence of quaternary ammonium cations that play a significant role in the stabilization of the colloidal crystals. Extension of the ideas presented shows that the extended DLVO theory is equally applicable to wholly inorganic heterogeneous systems.
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15.
  • Tosheva, Lubomira, et al. (författare)
  • Silicalite-1 containing microspheres prepared using shape-directing macro-templates
  • 2000
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 35-36, s. 621-629
  • Tidskriftsartikel (refereegranskat)abstract
    • Silicalite-1 microspheres were prepared by a novel method based on the use of anion exchange resins as shape-directing macro-templates. In a first step, spherical beads of the ion exchange resin were hydrothermally treated in a silicalite-1 synthesis solution. This resulted in the crystallization of silicalite-1 in the pores of the resin and the formation of a silicalite-1/resin composite material. The organic ion exchange resin was then removed by calcination leaving self-bonded spherical particles of silicalite-1. The influence of the type of ion exchange resin, the treatment time as well as the weight ratio between synthesis solution and resin on the properties of the resultant materials were investigated. The silicalite-1 containing microspheres were characterized by XRD, Raman spectroscopy, SEM, nitrogen adsorption and microhardness measurements.
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16.
  • Tosheva, Lubomira, et al. (författare)
  • Silicalite-1 macrostructures – preparation and structural features
  • 2000
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 39:1-2, s. 91-101
  • Tidskriftsartikel (refereegranskat)abstract
    • Zeolite macrostructures in the form of silicalite-1 spheres were prepared using anion exchange resin beads as shape directing macrotemplates. The resin was removed after the synthesis by combustion leaving solid spherical particles identical in shape and size to the original resin beads. The formation of the silicalite-1 spheres was studied by Raman spectroscopy, X-ray diffraction, scanning electron microscopy and nitrogen adsorption measurements. Samples prepared for different times of treatment and at two different temperatures, 100°C and 165°C, were investigated. The spheres obtained for short treatment times consist of amorphous silica, which after longer hydrothermal treatment in the presence of TPA cations is partially or entirely transformed into an MFI structure. A single treatment at 100°C resulted in hard silicalite-1 spheres of low crystallinity, whereas fully crystalline spheres could be obtained by a treatment at the higher temperature. However, the spheres prepared at 165°C have inferior mechanical properties and can even loose their shape at certain conditions. A better control of both hardness and crystallinity was achieved by using a two-step synthesis procedure, where a treatment at 100°C was followed by a treatment at 165°C.
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17.
  • Tosheva, Lubomira, et al. (författare)
  • Zeolite beta spheres
  • 2001
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 48:1-3, s. 31-37
  • Tidskriftsartikel (refereegranskat)abstract
    • Zeolite beta was crystallized from clear homogeneous solutions within the pores of anion exchange resin beads. The organic macrotemplate was then removed by combustion leaving stable macrospheres of zeolite beta. The zeolite beta crystallization within the resin beads was investigated by X-ray diffraction, Raman spectroscopy, SEM and nitrogen adsorption measurements. Crystallization within the macrotemplates was compared with the crystallization from bulk solution. The influence of the resin beads on the crystallization process was investigated by increasing the amount of ion exchanger present during synthesis and also by preparing bulk samples in the absence of macrotemplates.
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18.
  • Wang, Zheng, et al. (författare)
  • Synthesis of thin silicalite-1 films on steel supports using a seeding method
  • 2002
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 52:3, s. 191-197
  • Tidskriftsartikel (refereegranskat)abstract
    • Thin and continuous silicalite-1 films with controllable thickness between 200 and 800 nm were synthesized on steel supports by a method employing seeding. A variety of steel types ranging from ordinary carbon steel to highly corrosion resistant steel were used. Continuous transparent silicalite-1 films were formed on all steel types after zeolite synthesis. The type of steel did not affect the film morphology, the thickness or the preferred orientation of the crystals. The (5 0 1) reflection dominates in the XRD pattern for thin films whereas the (1 0 1) and (3 0 3) reflections dominate for thicker films. The silicalite-1 films on various stainless steel supports were stable during calcination, whereas a relatively thick magnetite/hematite film formed on carbon steel upon calcination and the silicalite-1 film detached.
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19.
  • Abdel-Magied, Ahmed Fawzy, et al. (författare)
  • Hierarchical porous zeolitic imidazolate framework nanoparticles for efficient adsorption of rare-earth elements
  • 2019
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier. - 1387-1811 .- 1873-3093. ; 278, s. 175-184
  • Tidskriftsartikel (refereegranskat)abstract
    • Hierarchical porous zeolitic imidazolate frameworks nanoparticles (ZIF-8 NPs) were synthesized at room temperature via a template-free approach under dynamic conditions (stirring) using water as a solvent. The ZIF-8 NPs were evaluated as adsorbents for rare earth elements (La3+, Sm3+ and Dy3+). Adsorption equilibrium was reached after 7h and high adsorption capacities were obtained for dysprosium and samarium (430.4 and 281.1 mg g(-1), respectively) and moderate adsorption capacity for lanthanum (28.8 mg g(-1)) at a pH of 7.0. The high adsorption capacitiese, as well as the high stability of ZIF-8 NPs, make the hierarchical ZIF-8 materials as an efficient adsorbent for the recovery of La3+, Sm3+ and Dy3+ from aqueous solution.
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20.
  • Abdelhamid, Hani Nasser, et al. (författare)
  • Carbonized chitosan encapsulated hierarchical porous zeolitic imidazolate frameworks nanoparticles for gene delivery
  • 2020
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 302
  • Tidskriftsartikel (refereegranskat)abstract
    • Hierarchical mesoporous carbon (MPC) nanomaterials derived from the carbonized chitosan (CTS) encapsulated zeolitic imidazolate frameworks (ZIF-8) is synthesized and applied for gene delivery. The synthesis of ZIF-8 is achieved at room temperature using water as a solvent in the presence of CTS within 60 min. The synthesis method offered a hierarchical porous structure of ZIF-8. The carbonization of the prepared materials leads to the formation of MPC nanomaterials. MPC materials were applied as a non-viral vectors for gene delivery using two oligonucleotides (ONs) called Luciferase-expressing plasmid (pGL3), and splice correction oligonucleotides (SCO). The materials are biocompatible and showed insignificant toxicity. The transfection using MPC with and without cell-penetrating peptides (CPPs) was reported. MPC improved the transfection efficiency of CPPs (PepFect 14 (PF-14), and PF-221) by 10 fold due to the synergistic effect of MCP and CPPs. The reasonable mechanism for the cell transfection using these new vectors was also highlighted.
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21.
  • Abdelhamid, Hani Nasser, et al. (författare)
  • Gene delivery using cell penetrating peptides-zeolitic imidazolate frameworks
  • 2020
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 300
  • Tidskriftsartikel (refereegranskat)abstract
    • Cell-penetrating peptides (CPPs), and metal-organic frameworks (MOFs) are promising as next-generation for the delivery of gene-based therapeutic agents. Oligonucleotide (ON)-mediated assembly of nanostructures composed of hierarchical porous zeolitic imidazolate framework (ZIF-8), and nanoparticles such as graphene oxide (GO), and magnetic nanoparticles (MNPs) for gene therapy are reported. Five different types of non-viral vectors (ZIF-8, RhB@ZIF-8, BSA@ZIF-8, MNPs@ZIF-8, and GO@ZIF-8), and three gene therapeutic agents (plasmid, splice correction oligonucleotides (SCO), and small interfering RNA (siRNA)) were investigated. The polyplexes were characterized and applied for gene transfection. The materials show very low toxicity with high efficiency for luciferase transfection. ZIF-8 enhances the transfection of plasmid, SCO, siRNA of CPPs by 2-8 folds. The mechanism of the cell uptakes was also highlighted. Data reveal cell internalization via scavenger class A (SCARA).
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22.
  • Abdelhamid, Hani Nasser, et al. (författare)
  • Luminescence properties of a family of lanthanide metal-organic frameworks
  • 2019
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 279, s. 400-406
  • Tidskriftsartikel (refereegranskat)abstract
    • Two isostructural series of lanthanide metal-organic frameworks denoted as SUMOF-7II (Ln) and SUMOF-7IIB (Ln) (Ln = La, Ce, Pr, Nd, Sm, Eu, and Gd) were synthesized using4,4',4 ''-(pyridine-2,4,6-triyl)tris(benzoic acid) (H(3)L2) and a mixture of H(3)L2 and 4,4',4 ''-(benzene-1,3,5-triyl)tris(benzoic acid) (H3BTB) as linkers, respectively. Both series were characterized using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermal analysis (TGA), and photoluminescence spectroscopy. Photoluminescence measurements show that Eu-MOFs demonstrate a red emission while Pr- and Nd-MOFs display an emission in the near-infrared (NIR) range. On the other hand, La-, Ce-, Sm- and Gd-MOFs exhibit only a ligand-centered emission. The average luminescence lifetimes in the SUMOF-7IIB series are 1.3-1.4-fold longer than the corresponding ones in the SUMOF-7II series. SUMOF-7IIs show a good photo- and thermal stability. Altogether, the properties of SUMOF-7II and SUMOF-7IIB render them promising materials for applications including sensing, biosensing, and telecommunications.
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23.
  • Aguilar, Wilson, et al. (författare)
  • Dendritic growth of NBA-ZSM-5
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093.
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Crystallization of ZSM-5 zeolite from a gel using n-butylamine as structure-directing agent was studied. Extreme high-resolution transmission and scanning electron microscopy showed the presence of dendritic features that are present at the crystal surface during most of the reaction time that become smoother towards completion of the crystallization. In addition, a web that likely stems from the gel, comprised of alumina-rich nanoparticles between the dendrites at the surface of the crystals was also identified. When the gel is not in direct contact with the crystal surface, dendrites and the web are not observed, and the crystals grow faster. Thus, the alumina-rich web retards the crystal growth and cause the formation of dendritic features.
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24.
  • Al-Soubaihi, Rola, et al. (författare)
  • Synthesis of hierarchically porous silica aerogel supported Palladium catalyst for low-temperature CO oxidation under ignition/extinction conditions
  • 2020
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier. - 1387-1811 .- 1873-3093. ; 292
  • Tidskriftsartikel (refereegranskat)abstract
    • Synthesis of well-dispersed palladium nanoparticles within silica aerogel pores with controlled size was carried out using sol-gel synthesis under supercritical ethanol drying. The high concentration of silanol groups on silica (SiO2) surface facilitated a superior palladium (Pd) loading up to 10 wt %. The synthesized Pd/SiO2 nanocomposite aerogels were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopic methods. The silica aerogel supported catalysts were found to have a wide pore size distribution. TEM investigations confirmed that Pd nanocrystals were located within the SiO2 microspores and mesopores. The catalyst was evaluated for carbon monoxide (CO) oxidation reaction under ignition/extinction conditions. The synthesized catalyst demonstrated a high catalytic activity at low operating temperatures (<200 °C) compared to unsupported Pd nanoparticles or bare SiO2 aerogels. This enhancement in CO oxidation activity with Pd/SiO2 aerogel catalysts are attributed to the small Pd particles, Pd interaction with the surface of the underlying SiO2 and the better dispersion of Pd particles within the SiO2 pores. Porosity played a more important role during the extinction cycle as a result of the slow dissipation of the heat leading to hysteresis. We demonstrate the influence of porosity of catalyst supports on the size, dispersion, and catalytic activity of Pd nanoparticles.
  •  
25.
  • Andersson, N, et al. (författare)
  • Structural features and adsorption behaviour of mesoporous silica particles formed from droplets generated in a spraying chamber
  • 2004
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093. ; 72, s. 175-183
  • Tidskriftsartikel (refereegranskat)abstract
    • Spherical mesoporous particles have been produced by spraying hydrolysed alkoxide solutions containing templating amphiphilic molecules. The modified spray drying method produces up to 10 g/h of spherical non-hollow particles with a size of 1–5 m. Transmission electron microscopy and X-ray diffraction showed that well ordered internal 2D hexagonal mesostructures could be prepared using both nonionic block copolymers and cationic surfactants as the templating molecules. Disordered cubic and well ordered lamellar, onion like, particles were prepared from the block copolymer templates. Nitrogen sorption data and mercury porosimetry show that pore size distribution of the mesoporous particles is very narrow with pore sizes varying from 2.5 to 8.5 nm as a function of templating amphiphiles. We have shown that the mesoscopic pores are accessible after calcination and can be filled with relatively large molecules; the particles adsorbed more than 20% (by weight) of the cationic dye Janus Green B from aqueous solutions.
  •  
26.
  •  
27.
  • Asahina, Shunsuke, et al. (författare)
  • A new HRSEM approach to observe fine structures of novel nanostructured materials
  • 2011
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 146:1-3, s. 11-17
  • Tidskriftsartikel (refereegranskat)abstract
    • A new approach for observing fine structures of novel thin, nanostructured materials called through the employed to observe interesting features on a variety of new, catalyticallyimportant hierarchically porous rattlespheres.
  •  
28.
  • Atluri, Rambabu, et al. (författare)
  • Structural variations in mesoporous materials with cubic Pm(3)over-barn symmetry
  • 2010
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 133:1-3, s. 27-35
  • Tidskriftsartikel (refereegranskat)abstract
    • The fine structural details of mesoporous materials possessing Pmn symmetry prepared with varying amphiphilic surfactants under acid and alkaline conditions are investigated using electron crystallography and sorption studies. The structural data derived is used to understand the parameters that govern the formation of cavity–windows and to propose synthetic strategies in order to control independently the size of the cavities and cavity–windows. Results support that whilst attainment of Pmn cubic packing is due to the overall surfactant geometry, the formation of cavity–windows is associated with the hydration layer formed at the interphase between the surfactant and the silica wall. The charge density at the micelle surface may be tailored using two strategies: (i) using dicationic gemini surfactants at low pHs resulting in an increase in the hydration layer; or (ii) by using co-structure directing agents such as organoalkoxysilanes which reduce the hydration layer surrounding the micelles. The latter leads to the formation of higher cavity sizes and may be useful for tuning fine structural details of mesoporous materials when considering their use in important applications such as gas separation.
  •  
29.
  • Atluri, Rambabu, 1981-, et al. (författare)
  • Structural variations in mesoporous materials with cubic Pm3n symmetry
  • 2010
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 133:1-3, s. 27-35
  • Tidskriftsartikel (refereegranskat)abstract
    • The fine structural details of mesoporous materials possessing Pm3n symmetry prepared with varying amphiphilic surfactants under acid and alkaline conditions are investigated using electron crystallography and sorption studies. The structural data derived is used to understand the parameters that govern the formation of cavity-windows and to propose synthetic strategies in order to control independently the size of the cavities and cavity-windows. Results support that whilst attainment of Pm3n cubic packing is due to the overall surfactant geometry, the formation of cavity-windows is associated with the hydration layer formed at the interphase between the surfactant and the silica wall.  The charge density at the micelle surface may be tailored using two strategies: (i) using dicationic gemini surfactants at low pHs resulting in an increase in the hydration layer; or (ii) by using co-structure directing agents such as organoalkoxysilanes which reduce the hydration layer surrounding the micelles. The latter leads to the formation of higher cavity sizes and may be useful for tuning fine structural details of mesoporous materials when considering their use in important applications such as gas separation.
  •  
30.
  • Aziz, Baroz, 1980-, et al. (författare)
  • Quantification of chemisorption and physisorption of carbon dioxide on porous silica modified by propylamines : Effect of amine density
  • 2012
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 159, s. 42-49
  • Tidskriftsartikel (refereegranskat)abstract
    • Detailed molecular aspects of carbon dioxide sorption on porous silica with different amounts of tethered and cross-linked n-propylamine groups were investigated. Infrared spectroscopy was applied to directly quantify physisorbed and chemisorbed CO2 on the amine modified silicas. The fractions of physisorbed CO2 and various chemisorbed species were determined as functions of CO2 pressure and the amine density on the modified silica. Physisorbed CO2 was a minor portion of the total CO2 uptake at low pressures, but it’s contribution increased to ∼35% at 1 bar of CO2 when the propylamine surface density was low or medium (0.87-1.67 NH2/nm2). Chemisorption of CO2 dominated when the propylamine content was high (2.74 NH2/nm2). The quantities of propylammonium propylcarbamate ion pairs increased with increasing propylamine content. At low or medium amine surface densities (0.87-1.67 NH2/nm2) this increase was approximately proportional to the amine density, but the quantity of ion pairs increased very significantly when the propylamine content was high (2.74 NH2/nm2). This dependency on amine density is consistent with the idea that a sufficiently close proximity of propylamine groups allows a formation of ion pairs. The relative fractions of carbamic acid and silylpropylcarbamate were significant for materials on which ion pairs could not form. Furthermore, the quantities of carbamic acid increased with increasing amine densities suggesting that the ion pairs have a role to stabilize the labile carbamic acid through hydrogen bonds.
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31.
  • Ballem, Mohamed Ali, et al. (författare)
  • Growth of Gd2O3 nanoparticles inside mesoporous silica frameworks
  • 2013
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 168, s. 221-224
  • Tidskriftsartikel (refereegranskat)abstract
    • Gadolinium oxide (Gd2O3) nanoparticles with very small size and narrow size distribution were synthesized by infiltration of Gd(NO3)(3)center dot 6H(2)O as an oxide precursor into the pores of SBA-15 mesoporous silica using a wet-impregnation technique. High resolution transmission electron microscopy and X-ray diffraction show that during the hydrothermal treatment of the precursor at 550 degrees C, gadolinium oxide nanoparticles inside the silica pores are formed. Subsequent dissolution of the silica framework in aqueous NaOH resulted in well dispersed nanoparticles with an average diameter of 3.6 +/- 0.9 nm. If GdCl3 center dot 6H(2)O is used as precursor, GdOCl is formed instead of Gd2O3. The Gd2O3 nanoparticles showed a weak antiferromagnetic behavior, as expected.
  •  
32.
  • Ballem, Mohamed A., et al. (författare)
  • Influence of synthesis temperature on morphology of SBA-16 mesoporous materials with a three-dimensional pore system
  • 2010
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 129, s. 106-111
  • Tidskriftsartikel (refereegranskat)abstract
    • Spherical particles of mesoporous silica SBA-16 with cubic Im3m structure were synthesized at low pH using Pluronic F127 as template and TEOS as silica source. The diameter of the spherical particles can be controlled in the range of 0.5–8 μm by varying synthesis temperature from 1 °C up to 40 °C. A sharp transition from large particle sizes at approximately 20 °C to smaller ones is observed when the temperature is increased. It is suggested that this morphology transition is due to a change in hydrolysis and condensation rate of the silica source and as a result the assembly of F127 micelles will differ. The SBA-16 samples were characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption techniques.
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33.
  • Boström, Zebastian, 1983, et al. (författare)
  • Preparation of high silica chabazite with controllable particle size
  • 2014
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811. ; 195, s. 294-302
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work synthesis procedures for controlling particle size distributions of high silica chabazite (Si/Al=100) zeolites between 0.3-4.5 μm is described. The chabzite zeolite crystallization and crystal growth have been monitored using XRD, SEM and DLS. Hydrothermal treatment parameters such as time, temperature and agitation and gel composition parameters such as amounts of water and structure directing agent (SDA) have been correlated with chabazite zeolite crystal size, crystal shape, synthesis yield and crystallinity. From this data a chabazite zeolite formation and crystal growth mechanism based on experimental studies and previous studies has been proposed. It was also found that large aggregates formed in the chabazite zeolite gel before any hydrothermal treatment (1 μm large when using zeolite gel with composition 1Al2O3:100SiO2: 60TMAdaOH:3100H2O). The size controlling parameter and size controlling synthesis step of the chabazite zeolite (below 1 μm) has been identified as the primary fractal aggregation of the silicium/aluminium/SDA species.
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34.
  • Cai, Juanjaun, et al. (författare)
  • Preparation of carbon/cobalt composite from phenolic resin and ZIF-67 for efficient tannic acid adsorption
  • 2019
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier. - 1387-1811 .- 1873-3093. ; 287, s. 9-17
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present work, a carbon/cobalt composite was prepared and evaluated for adsorption of ecologically harmful tannic acid (TA). The composite was prepared by simply mixing phenolic resin with ZIF-67 and following by carbonization. TEM and SEM images showed that ZIF-67 was etched by phenolic resin and cobalt nanoparticles were formed and evenly distributed in carbon. Macroporous structure was generated between the carbonized phenolic resin and ZIF-67. N2 adsorption-desorption isotherms results exhibited that the composite also had both micro- and meso-pores (average pore size of 5 nm) with a high surface area of 393 m2 g−1. Porous structure and evenly distributed cobalt nanoparticles facilitated the diffusion and adsorption of TA due to the formation of the complex between TA macromolecules and cobalt. The highest observed adsorption amount was as high as 2778 mg g−1, significantly higher than that of the carbon prepared from carbonization of phenolic resin (205 mg g−1) and ZIF-67 (1375 mg g−1). The carbon composite material is easy to recover and reuse due to the magnetic property. The reuse experiment also showed high stability of the composite. All of the results indicated a great potential of the developed carbon composite material in wastewater treatment in the industry.
  •  
35.
  • Cardenas, Edgar, et al. (författare)
  • Influence of the internal structure of the gel on Al-zoning in NBA-ZSM-5 crystals
  • Ingår i: Microporous and Mesoporous Materials. - 1387-1811 .- 1873-3093.
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • The crystallization of ZSM-5 from a gel comprising n-butylamine as structure directing agent was investigated. The samples were characterized by X-ray diffraction, nitrogen gas adsorption, extreme high-resolution transmission and scanning electron microscopy, and energy dispersive spectroscopy. The gel was found to be composed by a silica-rich matrix embedded in a skeleton of alumina-rich nanoparticles. During growth of the crystals, the silica-rich matrix is consumed first, and an increasing fraction of the alumina-rich nanoparticles are utilized later in the growth process. This leads to a non-uniform consumption of the gel walls during crystal growth. Consequently, the Si/Al ratio of the gel is steadily decreasing, which is accompanied by a corresponding decrease in the Si/Al ratio from the center to the outer surface of the crystals, i.e. Al-zoning of the ZSM-5 crystals.
  •  
36.
  • Chen, Yanping, et al. (författare)
  • PKU-20 : A new silicogermanate constructed from sti and asv layers
  • 2016
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 224, s. 384-391
  • Tidskriftsartikel (refereegranskat)abstract
    • A new silicogermanate (PKU-20) was hydrothermally synthesized using triethylisopropylammonium cation as the structure directing agent in the presence of fluoride. Its structure was determined from a combination of synchrotron single crystal X-ray diffraction and powder X-ray diffraction data. PKU-20 crystallizes in the monoclinic space group C2/m, with the lattice parameters of a = 18.5901(6) angstrom, b = 13.9118 (4) angstrom, c = 22.2614(7) angstrom and beta = 100.1514 (12)degrees. The framework of PKU-20 is constructed from an alternate stacking of sti and asv layers. The sti layer is exactly the same as that in the STI framework, while the asv layer is a new layer sliced off from the ASV framework parallel to the (112) plane. The takeout scheme of the layer is discussed on the basis of a composite building unit D4R-/au-D4R. PKU-20 possesses a two-dimensional channel system, where the 10-ring channels parallel to the [010] direction are intercrossed by 12-ring pockets along the [101] direction.
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37.
  •  
38.
  • Cheung, Ocean, et al. (författare)
  • CO2 selective NaMg-CTS-1 and its structural formation from the titanium silicate based molecule sieve NaMg-ETS-4 upon dehydration
  • 2014
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 198, s. 63-73
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • A range of titanium silicates (ETS-4 and CTS-1) with interesting gas separation properties were studied as CO2 adsorbents. Some of these adsorbents, in particular NaMg-CTS-1, showed the ability to selectively adsorb CO2-over-N2. Partially exchanged NaM-ETS-4 (M = Mg, Ca, Sr and Ba) were synthesised in the Na+ form and ion exchanged with group 2 cations. All but NaBa-ETS-4 transformed into their CTS-1 counterparts, when these partially exchanged Na-ETS-4 were dehydrated. The transformation from ETS-4 to CTS-1 was monitored and studied extensively using diffraction and spectroscopic techniques. Powder X-ray diffraction allowed us to follow the changes of the unit cell parameters occurred at different temperatures. We combined high energy X-ray total scattering (analysed by pair distribution functions – PDF analysis), electron diffraction, infrared, Raman and Nuclear Magnetic Resonance (NMR) spectroscopy to study the transformation of ETS-4 to CTS-1. We understood that under dehydration steps, there was significant disruption to the Ti–O–Ti chain along the b-axis, which occurred concurrently with the distortion of the double 3-rings alongside of these chains. These changes were partly responsible for the contraction of the ETS-4 framework (and successive transformation to CTS-1). The new information allowed us to understand the interesting structures and sorption properties of these adsorbents
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39.
  • Cheung, Ocean, et al. (författare)
  • Silicoaluminophosphates as CO2 sorbents
  • 2012
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 156, s. 90-96
  • Tidskriftsartikel (refereegranskat)abstract
    • Silicoaluminophosphates (SAPO-17, SAPO-35, SAPO-56 and SAPO-RHO) synthesised via hydrothermal means are tested for their abilities to adsorb carbon dioxide. These 8-ring microporous phosphates show high capacities to adsorb CO2. SAPO-RHO has a high uptake of CO2 and a very low uptake of N-2 due to its narrow pore window aperture at 273 K. Its significant uptake of N-2 at 77 K is rationalised by a temperature induced shrinkage effect. SAPO-56 has a slightly higher CO2 capacity (5.42 mmol/g, 273 K, 101 kPa) and is less water sensitive than zeolite 13X. Cyclic adsorption and in situ infrared spectroscopy (IR) reveal that SAPOs retain 95% of their original CO2 capacity after six cycles and that adsorption occurs via physisorption. The calculated heat of adsorption for CO2 (at 0.2-0.7 mmol/g loading) on SAPO-56 and SAPO-RHO lies in the physisorption range (similar to 35 kJ/mol). SAPOs, in particular SAPO-56 and SAPO-RHO, possess many desirable properties and are potentially good adsorbents for CO2 capture in swing adsorption processes.
  •  
40.
  • Cho, Jung, 1991-, et al. (författare)
  • The synergistic development of electron crystallography and zeolite discovery
  • 2023
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 358
  • Tidskriftsartikel (refereegranskat)abstract
    • During the past decades, the advancement of new electron crystallographic techniques has made important impacts for the discovery of novel zeolites. High-resolution transmission electron microscopy (HRTEM) imaging directly reveals detailed structural features in zeolites, which is especially useful for studying disordered materials. 3D atomic structures of new zeolites are determined by combining HRTEM images along several projections. Electron diffraction techniques have evolved from 2D zonal-axis electron diffraction to 3D electron diffraction (3D ED), which has transformed a TEM into a single nanocrystal diffractometer for structural elucidation. The development of electron crystallography parallels the discovery of novel zeolites, where Corma's research group has played the key role and contributed to at least 30 zeolite frameworks in the Database of Zeolite Structures. Herein, we present how the ITQ zeolite materials developed by Corma's group pushed the development of electron crystallographic techniques, and how the new 3D ED techniques accelerated the discovery of novel zeolites. During the past 7 years, nearly 80% of new zeolite structures have been determined by electron crystallography. Detailed atomic structural information has been revealed from nano- and micrometer-sized crystals of extra-large pore zeolites, disordered zeolites, and low-dimensional zeolites such as nanotubes and nanosheets.
  •  
41.
  • Du, Xing-Hao, et al. (författare)
  • BODIPY-linked conjugated porous polymers for dye wastewater treatment
  • 2022
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier. - 1387-1811 .- 1873-3093. ; 332
  • Tidskriftsartikel (refereegranskat)abstract
    • As a new family of functional porous materials, conjugated porous polymers (CPPs) with tuneable porosities and molecular architectures show great potentials in adsorption, light harvesting, and catalysis applications. This paper describes the incorporation of strong visible-light absorbing BODIPY molecules into the skeleton of CPPs via Sonogashira coupling reactions. The obtained CPPs displayed integrated properties of high surface area, hierarchical porous structures and strong visible-light absorption. As a result, the CPPs showed relatively high adsorption capacity and high photocatalytic degradation efficiency towards organic dyes. Mechanism studies revealed that the CPPs enabled the generation of singlet oxygen species under light irradiation, accounting for the main driving force for the dye degradation. This study provides a new route for the development of organic adsorbents and photocatalysts for water treatment and purification.
  •  
42.
  • Falk, Yana Znamenskaya, et al. (författare)
  • Langmuir - Blodgett monolayers of SBA-15 particles with different morphologies
  • 2018
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier. - 1387-1811 .- 1873-3093. ; 256, s. 32-38
  • Tidskriftsartikel (refereegranskat)abstract
    • This study presents an optimized protocol for the deposition of mesoporous SBA-15 particles with platelet-like and rod-like morphologies on different types of supporting substrates using LangmuirBlodgett methodology, resulting in the formation of monolayers with porosity orientation controlled by the type, i. e. the morphology, of particles used over large areas. The morphology of the SBA-15 particles and specifically their aspect ratio are essential for the orientation of the particles and, hence, the orientation of the intrinsic porosity. Deposition on a surface, establishes a layer of SBA-15 platelets with pores oriented perpendicular to the substrate, or a layer of SBA-15 rods with pores oriented parallel to the substrate. In both cases, the oriented SBA-15 particles can be deposited onto areas that are larger than square centimeter using Langmuir-Blodgett technique. SEM characterization demonstrates formation of uniform close-packed layer of oriented mesoporous SBA-15 silica particles. Additionally, the particles coverage of the surface is independent and unaffected by the type of supporting substrate, which allows convenient experimental performance without requiring surface or particle modifications. In conclusion, Langmuir Blodgett is a convenient technique for deposition of mesoporous SBA-15 particles with different morphology types in order to obtain a close-packed layer. The methodology is suitable to create large area sensors, used in; for instance, bio-sensing applications. (C) 2017 Elsevier Inc. All rights reserved.
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43.
  • Fijneman, Andreas J., et al. (författare)
  • Local quantification of mesoporous silica microspheres using multiscale electron tomography and lattice Boltzmann simulations
  • 2020
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811. ; 302
  • Tidskriftsartikel (refereegranskat)abstract
    • The multiscale pore structure of mesoporous silica microspheres plays an important role for tuning mass transfer kinetics in technological applications such as liquid chromatography. While local analysis of a pore network in such materials has been previously achieved, multiscale quantification of microspheres down to the nanometer scale pore level is still lacking. Here we demonstrate for the first time, by combining low convergence angle scanning transmission electron microscopy tomography (LC-STEM tomography) with image analysis and lattice Boltzmann simulations, that the multiscale pore network of commercial mesoporous silica microspheres can be quantified. This includes comparing the local tortuosity and intraparticle diffusion coefficients between different regions within the same microsphere. The results, spanning more than two orders of magnitude between nanostructures and entire object, are in good agreement with bulk characterization techniques such as nitrogen gas physisorption and add valuable local information for tuning mass transfer behavior (in liquid chromatography or catalysis) on the single microsphere level.
  •  
44.
  • Filippov, Andrei, et al. (författare)
  • Self-Diffusion of Phosphonium Bis(Salicylato)Borate Ionic Liquid in Pores of Vycor Porous Glass
  • 2016
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 230, s. 128-134
  • Tidskriftsartikel (refereegranskat)abstract
    • 1H NMR pulsed field gradient was used to study self-diffusion of a phosphonium bis(salicylato)borate ionic liquid ([P6,6,6,14][BScB]) in the pores of Vycor porous glass at 296 K. Confinement in pores increases diffusion coefficients of the ions by a factor of 35. However, some [P6,6,6,14][BScB] ions demonstrated apparent diffusion coefficients much lower than their mean values, which may be due to partially restricted diffusion of the ions. We suggest that this fraction corresponds to areas where ions are confined by pore ‘necks’ (micropores) and empty voids. Heating of the ionic liquid / Vycor system at 330 K led to a change in the diffusivity of the ions, because of their redistribution in the pores. The size of the bounded regions is on the order of 1 µm, as estimated from the dependence of the ion diffusivity on the diffusion time.
  •  
45.
  • Frykstrand, Sara, et al. (författare)
  • On the pore forming mechanism of Upsalite, a micro- and mesoporous magnesium carbonate
  • 2014
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 190, s. 99-104
  • Tidskriftsartikel (refereegranskat)abstract
    • This work analyzes the pore forming mechanism and stability of Upsalite; an extraordinary moisture absorbing, high-surface area magnesium carbonate powder synthesised without the use of surfactants as pore forming agents. The pores in Upsalite were found to be created in a two-step process where the first step includes the formation of micropores by solvent evaporation and release of physically bound carbon dioxide, acting as an in-situ pore-forming template. In the second step, the micropores expand to mesopores due to partial decomposition of organic groups on the surface of the pore walls when the material is stored in air at moderate temperatures (70 °C). The resulting material has a narrow pore size distribution centered at 5 nm, and the amorphous structure is stable upon storage in a humid atmosphere.It was further shown that calcination at temperatures above 250 °C is required for complete removal of the organic surface groups in Upsalite. Prior to calcination, the organic groups present in the material act as barriers hindering water to induce crystallization of the bulk material. After calcination, however, Upsalite crystallizes into nesquehonite when stored at 100 % relative humidity for several days. The results presented herein are expected to be useful for the development of novel surfactant-free synthesis routes of porous materials as well as for the understanding of the long-term performance of such materials.
  •  
46.
  • Gao, Chuanbo, 1981- (författare)
  • Formation of mesoporous Co3O4 replicas of different mesostructureswith different pore sizes
  • 2009
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier. - 1387-1811 .- 1873-3093. ; 123, s. 314-323
  • Tidskriftsartikel (refereegranskat)abstract
    • Mesoporous metal oxides Co3O4 are prepared via hard templating synthesis method by using various mesoporous silicas with different pore size as templates. The pore size of the mesoporous silicas with the symmetry of two-dimensional (2d)-hexagonal p6mm, bicontinuous cubic Ia-3d and Pn-3m have been controlled in the range of 6.6–10.7, 4.2–7.5 and 5.1–6.7 nm, respectively, by choosing different surfactants and co-surfactants and by adjusting either the aging temperature or the ionization degree of the surfactant. The pore size of the silica template has been considered to be an important factor that determines the mesostructure of the resulting metal oxides. It has been found that for p6mm, it is easier to replicate the mesoporous symmetry at large size of mesopores. For Ia-3d, at large-pore size two sets of bicontinuous meso-channels are replicated into mesoporous Co3O4, while small-pore Ia-3d leads to replication of both one set and two sets of meso-channels. Co3O4 can replicate both one set and two sets of bicontinuous Pn-3m meso-channels at all pore sizes that can be obtained (5.1–6.7 nm), indicating the existence of ordered complementary micropores within the silica walls.
  •  
47.
  • Gao, Chuanbo, et al. (författare)
  • Mesostructured silica based delivery system for a drug with a peptide as a cell-penetrating vector
  • 2009
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 122:1-3, s. 201-207
  • Tidskriftsartikel (refereegranskat)abstract
    • A drug delivery system using mesostructured silica as a reservoir has been developed for the storage and controlled release of a drug with a cell-penetrating peptide (CPP) as a vector. We use fluorescein isothiocyanate (FITC) as the drug model and octaarginine (R8) as a vector to endow the drug with cell-penetrating property. The mesostructured silica reservoir system was prepared by using a one-pot liquid?crystal templating method, which is suitable for the encapsulation of intact FITC-R8 conjugates and sustained release of drugs without hampering their properties. The hydrophobic poly(propyl oxide) (PPO) shell of the pore-filling Pluronic F127 and the electrostatic interaction between R8 and siloxide ions on the pore walls act as the diffusion-limiting factors of the FITC-R8 conjugate. A sigmoidal in vitro release of FITC-R8 from mesostructured silica into phosphate buffered saline (PBS, pH 7.4) was observed and the typical release duration was 5 days at 37 ‹C. Release from the reservoir yielded significant elongation in duration of the FITC signals in DU145 cells by confocal microscopic analysis, compared with a single administration of FITC-R8.  
  •  
48.
  • Garcia, Gustavo, et al. (författare)
  • Synthesis of zeolite Y from diatomite as silica source
  • 2016
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 219, s. 29-37
  • Tidskriftsartikel (refereegranskat)abstract
    • Bolivian diatomite was successfully used as a silica source for the synthesis of zeolite Y. Prior to synthesis, the diatomite was leached with sulfuric acid to remove impurities and aluminum sulfate was used as an aluminum source. The raw materials were reacted hydrothermally at 100 °C in water with sodium hydroxide and different Na2O/SiO2 ratios were investigated. The final products were characterized by scanning electron microscopy, X-ray diffraction, gas adsorption and inductively coupled plasma-atomic emission spectroscopy. Diatomites originating from different locations and therefore containing different types and amounts of minerals and clays as impurities were investigated. After optimization of synthesis time, zeolite Y with low SiO2/Al2O3 ratio (3.0–3.9) was obtained at a high yield for high alkalinity conditions (Na2O/SiO2 = 0.85–2.0). Lower Na2O/SiO2 ratios resulted in incomplete dissolution of diatomite and lower yield. Nevertheless, decreasing alkalinity resulted in a steady increase of the SiO2/Al2O3 ratio in zeolite Y. Consequently, it was possible to synthesize almost pure zeolite Y with a SiO2/Al2O3 ratio of 5.3 for a Na2O/SiO2 ratio of 0.6, albeit at a low yield. In this respect, diatomite enables the synthesis of high silica zeolite Y and behaves similarly to colloidal silica in traditional syntheses, with both sources of silica having in common a high degree of polymerization. Interestingly, the presence of minerals and clays in the starting diatomite had marginal effects on the outcome of the synthesis. However, their dissolution resulted in presence of calcium and magnesium in the zeolite Y crystals. Finally, overrun of all investigated compositions resulted in the formation of zeolite P nucleating and growing onto dissolving zeolite Y crystals, which was shown to be triggered when aluminum was completely depleted at high alkalinity
  •  
49.
  • Geng, Shiyu, et al. (författare)
  • Monolithic carbon aerogels from bioresources and their application for CO2 adsorption
  • 2021
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier. - 1387-1811 .- 1873-3093. ; 323
  • Tidskriftsartikel (refereegranskat)abstract
    • Monolithic binder-free CO2 adsorbents with high adsorption capacity, selectivity, adsorption-desorption kinetics, and regenerability are highly desired to both reduce the environmental impact of anthropogenic CO2 emissions and purify valuable gases from CO2. Herein, we report a strategy to prepare monolithic carbonaceous CO2 adsorbents from low-cost and underutilized bioresources, which enabled the formation of a delicate anisotropic, hierarchical porous structure. With optimized material composition and processing conditions, the biobased carbon adsorbent demonstrated a CO2 adsorption capacity of 4.49 mmol g-1 at 298 K and 100 kPa, relatively weak adsorbent-adsorbate affinity, good CO2/N2 selectivity, and advantageous hydrophobicity against water vapor. Moreover, the unique anisotropic porous structure provided high stiffness and good flexibility to the adsorbent in the axial and radial directions, respectively. We confirmed that this type of carbon adsorbent could be packed in a column for dynamic CO2 capture independent of any binders, indicating its promising future for further development toward widespread utilization.
  •  
50.
  • Ghazaie, M., et al. (författare)
  • Study on release of naproxen and metformin encapsulated in biopolymer-inorganic mesoporous matrices as controlled drug-delivery systems
  • 2017
  • Ingår i: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811. ; 244, s. 291-300
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, a new methodology was applied for controlling the release of different drugs by encapsulating them in organic-inorganic hybrids via sol-gel technique. The assembled organic-inorganic hybrids had diverse BET surface area, porosity, and high heat resistance. The synthesized organic-inorganic hybrids were based on zirconium(IV) propoxide, and tetraethyl orthosilicate as precursor of inorganic network, and chitosan or N-triethylchitosan as organic or biopolymer components. In these hybrid composites, drug and biopolymer were coated with a mesoporous inorganic material. FT-IR, FE-SEM, DSC, BET, XRD techniques, and Zeta potential analysis used for investigating the formation of metformin/ chitosan@ZrO2 and sodium naproxen/N-triethylchitosan@SiO2 hybrid composites. Then for investigating the role of sol-gel process, the release of metformin and sodium naproxen in the prepared hybrid composites was investigated as model drugs. Compare to drugibiopolymer composite, incorporation of ZrO2 or SiO2 coating enhanced the drug entrapment appreciably, and naturally reduced the rate of drug release. For example, the metformin/chitosan composite without ZrO2 coating released the whole drug in less than10 h in pH 7.4 when the composite coated with ZrO2 released the entrapped drug after 25 h. (C) 2016 Elsevier Inc. All rights reserved.
  •  
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