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Rapid Synthesis of SBA-15 Rods with Variable Lengths, Widths, and Tunable Large Pores
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials . Linköping University, The Institute of Technology.ORCID iD: 0000-0002-2286-5588
2011 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 8, 4994-4999 p.Article in journal (Refereed) Published
Abstract [en]

Dispersed SBA-15 rods have been synthesized with varying lengths, widths, and pore sizes in a low-temperature synthesis in the presence of heptane and NH4F. The pore size of the material can systematically be varied between 11 and 17 nm using different hydrothermal treatment times And/or temperatures. The particle length (400-600 nm) and width (100-400 nm) were tuned by varying the HCl concentration. All the synthesized materials possess a large surface area of 400-600 m(2)/g And a pore volume of 1.05-1.30 cm(3). A, mechanism for the effect of the HCl concentration on the particle morphology is suggested. Furthermore, it is shown that the reaction time an be decreased to 1 h, with well-retained pore size and morphology. This work has resulted in SBA-15 rods with the largest pore size reported for this morphology.

Place, publisher, year, edition, pages
ACS American Chemical Society , 2011. Vol. 27, no 8, 4994-4999 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-67831DOI: 10.1021/la104864dISI: 000289321000091OAI: oai:DiVA.org:liu-67831DiVA: diva2:413599
Available from: 2011-04-29 Created: 2011-04-29 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Synthesis of Mesoporous Silica and their Use as Templates for Metal and Metal Oxide Nanoparticles
Open this publication in new window or tab >>Synthesis of Mesoporous Silica and their Use as Templates for Metal and Metal Oxide Nanoparticles
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis covers the synthesis and characterization of two types of mesoporous silica, SBA-15 silica with two-dimensional hexagonal arrangement, and SBA-16 silica with three-dimensional cubic arrangement. The obtained mesoporous materials were then used as hard templates for synthesizing of different types of nanostructures.

In the first part, the effects of some synthesis parameters on the morphology and texture properties of the mesoporous silica have been studied. By varying the synthesis temperature solid spheres of SBA-16 with different sizes were synthesized and by additions of heptane as a swelling agent, SBA-16 in a hollow-sphere morphology with a large pore size was obtained. In the case of SBA-15, dispersed rods were synthesized in the presence of heptane and NH4F in a low-temperature synthesis. The length of the rods was varied by changing the concentration of HCl, and the pore size was tuned by changing the hydrothermal treatment time and temperature. Furthermore, the reaction time was decreased with a well-retained pore size and morphology. This work has resulted in SBA-15 rods with large pore sizes for this morphology.

In the second part, SBA-15 and SBA-16 silica were used to synthesize different nanostructured materials such as metal and metal oxide nanoparticles. In fact, most of the work in this part is focused on the use of mesoporous silica as hard templates for synthesis of different types of nanoparticles. The synthesis of these nanoparticles was carried out by infiltration of a suitable precursor in the pores of the silica template. The mesoporous frameworks act as molds controlling the size and the final shape of the formed nanostructures. Subsequent dissolution of the silica templates by NaOH resulted in e.g., monodispersed zirconia, hematite, and cobalt nanoparticles with narrow size distributions.

Functionalization of the SBA-15 surfaces was carried out in the synthesis of cobalt nanoparticles. This functionalization plays a crucial role on the infiltration and reaction of the reagents in the pores of the silica. By functionalization of the external surface, a highly hydrophobic surface was achieved, which proved to be sufficient to avoid formation of large cobalt particles outside the silica channels, while the internal functionalization enhances the attraction of cobalt ions to the silica pores, and as a result the nanoparticles grew inside these pores.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2011. 76 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1372
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-67920 (URN)978-91-7393-156-4 (ISBN)
Public defence
2011-05-31, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2011-05-02 Created: 2011-05-02 Last updated: 2013-10-02Bibliographically approved
2. Controlling the Pore Size and Morphology of Mesoporous Silica
Open this publication in new window or tab >>Controlling the Pore Size and Morphology of Mesoporous Silica
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Mesoporous silica with a hexagonally ordered pore structure (SBA-15) has been synthesized. Through variations in the synthesis conditions several morphologies, such as fibers, sheets and separate rods, have been realized. Furthermore, additions of heptane and NH4F make it possible to synthesize SBA-15 with pores as large as 18 nm in the sheet morphology. Mechanisms for the formation of different morphologies have been suggested. In the case of fibers and sheets, the amount of heptane present during the synthesis determines the final morphology. For low concentrations, the heptane enters the micelles and increases the pore size while the particles (crystallites) attaches to each other end to end. When the heptane concentration increases, the heptane droplets increase in size, and above a critical droplet size the crystallites attach with one short end towards the droplet, forming the sheet morphology. The crystallites can also be separated. This is the case of the rod morphology. The separation is performed by shortening the stirring time and increasing the HCl concentration. The increased amount of HCl increases the hydration rate of the silica precursor, which can be used to control the thickness and length of the rods. Furthermore, the reaction time has been decreased from 20 h for all morphologies to less than 4 hours. The materials have been characterized with nitrogen sorption, electron microscopy and x-ray diffraction. Also, thermogravimetric analysis and fourier transformed infrared spectroscopy have been used for studying the removal of surfactants.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2010. 67 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1451
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-70405 (URN)LIU-TEK-LIC-2010:22 (Local ID)978-91-7393-305-6 (ISBN)LIU-TEK-LIC-2010:22 (Archive number)LIU-TEK-LIC-2010:22 (OAI)
Presentation
2011-11-03, Planck, Fysikuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2011-09-06 Created: 2011-09-06 Last updated: 2013-10-02Bibliographically approved
3. Mesoporous Building Blocks: Synthesis and Characterization of Mesoporous Silica Particles and Films
Open this publication in new window or tab >>Mesoporous Building Blocks: Synthesis and Characterization of Mesoporous Silica Particles and Films
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. 82 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1542
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-99858 (URN)10.3384/diss.diva-99858 (DOI)978-91-7519-516-2 (ISBN)
Public defence
2013-11-15, Visionen, Hus B, Campus Valla, Linköpings universitet, Linköping, 13:15 (English)
Opponent
Supervisors
Available from: 2013-10-22 Created: 2013-10-22 Last updated: 2013-10-22Bibliographically approved

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Johansson, EmmaBallem, MohamedCordoba Gallego, Jose ManuelOdén, Magnus

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