| 1. |
- Nikkanen, Juha-Pekka, et al.
(författare)
-
Synthesis of carbon nanotubes on FexOy doped Al2O3-ZrO2 nanopowder
- 2014
-
Ingår i: Powder Technology. - : Elsevier BV. - 0032-5910. ; 266, s. 106-112
-
Tidskriftsartikel (refereegranskat)abstract
- Carbon nanotubes (CNTs) were synthesized on liquid flame sprayed (LFS) powder substrate of iron oxide doped Al2O3-ZrO2. Iron oxide doped Al2O3-ZrO2 nanopowder was produced by injecting the liquid precursor of aluminium-isopropoxide, zirconium-n-propoxide, ferrocene and p-xylene into a high temperature (similar to 3000 K) flame. The precursor solution was atomized by high-velocity H-2 flow and injected into the flame where nanopartides were formed. The collected sample was used as a substrate material for the synthesis of CNTs. The CNTs were formed on the surfaces of the substrate powder by catalyzed decomposition of CH4. The particle morphology, size, phase composition and the nature of CNTs were determined by TEM, FE-SEM, XRD, XPS, Mossbauer and Raman spectroscopy. The collected powder consists of micron-sized agglomerates with nanosized primary particles. Tetragonal zirconia was detected while alumina was amorphous. In the carbonized sample multiwalled CNTs were obtained. (C) 2014 Elsevier B.V. All rights reserved.
|
|
| 2. |
- Björk, Emma M., 1981-
(författare)
-
Mesoporous Building Blocks : Synthesis and Characterization of Mesoporous Silica Particles and Films
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Catalyst supports, drug delivery systems, hosts for nanoparticles, and solar cells are just some examples of the wide range of exciting applications for mesoporous silica. In order to optimize the performance of a specific application, controlling the material’s morphology and pore size is crucial. For example, short and separated particles are beneficial for drug delivery systems, while for molecular sieves, the pore size is the key parameter.In this thesis, mesoporous silica building blocks, crystallites, with hexagonally ordered cylindrical pores were synthesized, with the aim to understand how the synthesis parameters affect the particle morphology and pore size. The synthesis of the particles is performed using a sol-gel process, and in order to increase the pore size, a combination of low temperature, and additions of heptane and NH4F was used. By variations in the amounts of reagents, as well as other synthesis conditions, the particle morphology and pore size could be altered. Separated particles were also grown on or attached to substrates to form films. Also, a material with spherical pore structure was synthesized, for the first time using this method.It was found that a variation in the heptane concentration, in combination with a long stirring time, yields a transition between fiber and sheet morphologies. Both morphologies consist of crystallites, which for the fibers are joined end to end, while for the sheets they are attached side by side such that the pores are accessible from the sheet surface. The crystallites can be separated to a rod morphology by decreasing the stirring time and tuning the HCl concentration, and it was seen that these rods are formed within 5 min of static time, even though the pore size and unit cell parameters were evolving for another 30 min. Further studies of the effects of heptane showed that the shape and mesoscopic parameters of the rods are affected by the heptane concentration, up to a value where the micelles are fully saturated with heptane. It was also observed that the particle width increases with decreasing NH4F concentration, independent of heptane amount, and a platelet morphology can be formed. The formation time of the particles decrease with decreasing NH4F, and the growth mechanism for platelets was further studied. The pore sizes for various morphologies were altered by e.g. variations in the hydrothermal treatment conditions, or the method for removing the surfactants.The separated particles can be attached to substrates, either during the particle synthesis or by post grafting prior to calcination. The film formation during the one-pot-synthesis was studied and a formation mechanism including nucleation of elongated micelles on the substrate was suggested. During the post grafting film synthesis, the medium in which the particles are dispersed, as well as functionalization of both particle and substrate are crucial for the post grafting process. The pores are easily accessible independent of the method, even though they are aligned parallel to the substrate when the one-pot-method is used, while post grafting gives a perpendicular pore orientation.In summary, this work aims to give an understanding for the formation of the synthesized material, and how to tune the material properties by alterations in parameter space. Successful syntheses of four different particle morphologies and two new types of films were performed, and the pore size could easily be tuned by various methods.
|
|
| 3. |
- Hussami, Linda
(författare)
-
Synthesis, Characterization and Application of Multiscale Porous Materials
- 2010
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis work brings fresh insights and improved understanding of nanoscale materials through introducing new hybrid composites, 2D hexagonal in MCM-41 and 3D random interconnected structures of different materials, and application relevance for developing fields of science, such as fuel cells and solar cells.New types of porous materials and organometallic crystals have been prepared and characterized in detail. The porous materials have been used in several studies: as hosts to encapsulate metal-organic complexes; as catalyst supports and electrode materials in devices for alternative energy production. The utility of the new porous materials arises from their unique structural and surface chemical characteristics as demonstrated here using various experimental and theoretical approaches.New single crystal structures and arene-ligand exchange properties of f-block elements coordinated to ligand arene and halogallates are described in Paper I. These compounds have been incorporated into ordered 2D-hexagonal MCM-41 and polyhedral silica nanofoam (PNF-SiO2) matrices without significant change to the original porous architectures as described in Paper II and III. The resulting inorganic/organic hybrids exhibited enhanced luminescence activity relative to the pure crystalline complexes.A series of novel polyhedral carbon nanofoams (PNF-C´s) and inverse foams were prepared by nanocasting from PNF-SiO2’s. These are discussed in Paper IV. The synthesis conditions of PNF-C’s were systematically varied as a function of the filling ratio of carbon precursor and their structures compared using various characterization methods. The carbonaceous porous materials were further tested in Paper V and VI as possible catalysts and catalyst supports in counter- and working electrodes for solar- and fuel cell applications.
|
|
| 4. |
- Kjellman, Tomas, et al.
(författare)
-
Independent Fine-Tuning of the Intrawall Porosity and Primary Mesoporosity of SBA-15
- 2013
-
Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 25:9, s. 1989-1997
-
Tidskriftsartikel (refereegranskat)abstract
- We present a study in which the intrawall porosity and primary mesoporosity. of SBA-15 are independently controlled by modifying the strength of the molecular interaction that governs the formation of the material. The interactions are targeted at specific times during the process of formation, which results in selective tuning of the porosity, while other characteristics of the SBA-15 material are retained. We show that the intrawall porosity can be considerably reduced by addition of NaI, but not NaCl, and that the shape of the primary mesopores can be influenced by a decrease in temperature, while while the two-dimensional hexagonal structure and the particle morphology and size remain unchanged. The timing of the "tuning event" is imperative. We show that a decrease in intrawall porosity by addition of NaI is generic to Pluronic-based mesoporous silica syntheses. This work demonstrates that the material characteristic of mesoporous silica is not necessarily restricted by the initial synthesis conditions as the material properties can be tuned by "actions" taken upon the ongoing synthesis. The triblock copolymer Pluronic P104 was used as a structure director and tetramethyl orthosilicate as a silica source. The materials have been characterized primarily with nitrogen sorption and small angle X-ray diffraction.
|
|
| 5. |
- Kupferschmidt, Natalia
(författare)
-
Toxicological and Immunomodulatory Properties of Mesoporous Silica Particles : Applications in Life Sciences
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Mesoporous silica particles offer great potential benefits as vehicles for drug delivery and in other biomedical applications. They present a high loading capacity due their ordered and size-tuneable pores that allow molecules to be loaded and released. In addition, they offer the possibility to enhance oral bioavailability of drugs with limited aqueous solubility and to protect pH sensitive drugs from the acidic conditions in the stomach on their way to the intestine.The aim of this thesis was to evaluate the biocompatibility and effects of mesoporous silica particles on immunocompetent cells. Subsequently, two potential life sciences applications were investigated: as adjuvants and as weight reduction agents.Adjuvants are used in vaccines in order to enhance the immunological response towards attenuated and poorly immunogenic antigens. Their function can be mediated through dendritic cells which have a central role in the control of adaptive immunity including immunological memory. Our results show that different types of mesoporous silica particles were able to tune the development of T cells both in human cell cultures and in mice. In contrast to the approved adjuvant alum (aluminium salts) which is a specific inducer of Th2-type immune responses, the particles induced more Th1-like responses, which may be desired in vaccines against allergy and intracellular pathogens such as viruses. Particle exposure to macrophages did not affect their cell function which is crucial for tissue homeostasis, wound repair and in prevention of autoimmune responses. Likewise, the cytokine secretion was not affected, which suggest that macrophages would not modulate the immune response towards the particles.Furthermore, mesoporous silica particles were highly tolerated at daily oral administrations of up to 2000 mg/kg doses for some of the materials prepared. Large pore mesoporous silica particles were shown to act as weight and body fat reduction agents without other observable pathological signs when administered in the diet of obese mice.Together; those results are promising for the development of mesoporous silica as drug delivery systems and adjuvants for oral administration of drugs or vaccines. Additionally, large pore mesoporous silica materials are potential agents for the treatment of obesity.
|
|
| 6. |
- Mille, Christian, 1982-
(författare)
-
Templating and self-assembly of biomimetic materials
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on the use of biomolecular assemblies for creating materials with novel properties. Several aspects of biomimetic materials have been investigated, from fundamental studies on membrane shaping molecules to the integration of biomolecules with inorganic materials.Triply periodic minimal surfaces (TPMS) are mathematically defined surfaces that partition space and present a large surface area in a confined space. These surfaces have analogues in many physical systems. The endoplasmic reticulum (ER) can form intricate structures and it acts as a replica for the wing scales of the butterfly C. rubi, which is characterized by electron microscopy and reflectometry. It was shown to contain a photonic crystal and an analogue to a TPMS. These photonic crystals have been replicated in silica and titania, leading to blue scales with replication on the nanometer scale. Replicas analyzed with left and right handed polarized light are shown be optically active.A macroporous hollow core particle was synthesized using a double templating method where a swollen block copolymer was utilized to create polyhedral nanofoam. Emulsified oil was used as a secondary template which gave hollow spheres with thin porous walls. The resulting material had a high porosity and low thermal conductivity.The areas of inorganic materials and functional biomolecules were combined to create a functional nanoporous endoskeleton. The membrane protein ATP synthase were incorporated in liposomes which were deposited on nanoporous silica spheres creating a tight and functional membrane. Using confocal microscopy, it was possible to follow the transport of Na+ through the membrane.Yop1p is a membrane protein responsible for shaping the ER. The protein was purified and reconstituted into liposomes of three different sizes. The vesicles in the 10-20 nm size range resulted in tubular structures. Thus, it was shown that Yop1p acts as a stabilizer of high curvature structures.
|
|
| 7. |
|
|
| 8. |
- Xu, Qian, et al.
(författare)
-
Nanopatterned zinc titanate thin films prepared by the evaporation-induced self-assembly process
- 2013
-
Ingår i: Thin Solid Films. - : Elsevier BV. - 0040-6090. ; 531, s. 222-227
-
Tidskriftsartikel (refereegranskat)abstract
- Nanopatterned thin films prepared by the evaporation-induced self-assembly process have up to now been limited to a few transition metal oxides (i.e. Al2O3, TiO2 and ZrO2). Here we describe the formation of zinc titanate nanoperforated thin films with different Zn/Ti ratios using the dipcoating process. Atomic force microscopy and scanning electron microscopy reveal that the structure consists of well-ordered pseudohexagonal nanoperforations in the range of 30 nm in diameter separated by 25 nm wide metal oxide ridges, while the film thickness is close to 2 nm. For films with a zinc precursor content up to 50 mol%, the well-organized structure of the thin film can be maintained, while at higher Zn contents the nanostructure is gradually becoming more disordered, which we have shown is consistent with the partial charge model. Grazing incidence X-ray diffraction measurements on the films calcined at 700 C indicate that the anatase phase of the pure TiO2 films is gradually consumed at the expense of a newly formed Zn2Ti3O8 phase upon increasing the Zn/Ti ratio in the starting precursor solution. The unique combination of the nanostructure with the zinc titanate composition grants these nanopatterned thin films significant application prospects in for instance optics and catalysis.
|
|
