Approaches to separations using silica colloidal membranes

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Title Approaches to separations using silica colloidal membranes
Publication Type dissertation
School or College College of Science
Department Chemistry
Author Igancio-de Leon, Patricia Anne Argana
Date 2012-08
Description This thesis describes the synthesis and properties of free-standing nanoporous silica colloidal membranes where the molecular transport is controlled on the basis of size, charge, and chiral selectivity. To achieve this, free-standing membranes were prepared from colloidal solutions of silica nanospheres and the nanopore size and surface functionality were varied. First, Au-coated membranes were prepared and the transport of neutral and charged small molecules through Au-coated silica colloidal membranes modified with poly(methacrylic acid) was studied. Polymer length was controlled by polymerization time to produce pH- and ion-responsive brushes inside the nanopores. By monitoring the flux of a diffusing species, it was demonstrated that the polyelectrolyte brush undergoes swelling and collapse when the pH is increased and decreased, respectively. We also observed an expansion and contraction in the absence and presence of counterions (e.g., Na+(aq) and cationic dye Rhodamine B), respectively. We studied the transport of enantiomers of a chiral dye molecule through silica colloidal membranes with attached chiral moieties. We used small molecules and polymers of amino acid derivatives and chiral calixarenes capable of chiral recognition as a result of stereochemically dependent noncovalent interactions with the diffusing molecule. We found that the selectivity remains approximately the same for membranes modified with small molecules and with polymers. This suggests that enantiopermselectivity depends primarily on the strength of noncovalent interactions rather than the availability of recognition sites. Next, the transport of various generations of dendrimers through silica colloidal membranes was studied in a proof-of-concept experiment to demonstrate the size-selectivity of our materials. Smaller dendrimers were found to diffuse faster and selectivity is improved by using smaller nanopores. Finally, the transport of proteins through silica colloidal membranes was studied as a function of nanopore size and surface functionality. Poly(ethylene glycol) chains were attached inside the nanopores to minimize nonspecific protein adsorption. The membranes exhibit size-selectivity where smaller proteins generally diffused faster. From the results of this preliminary investigation, we propose that protein-nanopore interactions also affect diffusion rates and selectivity.
Type Text
Publisher University of Utah
Subject Charge-selective separations; Chiral separations; Colloidal membranes; Nanoporous; Silica; Size-selective separations
Dissertation Name Doctor of Philosophy
Language eng
Rights Management Copyright © Patricia Anne Argana Ignacio-de Leon 2012
Format application/pdf
Format Medium application/pdf
Format Extent 5,362,102 bytes
Identifier etd3/id/3411
ARK ark:/87278/s6cz6ggx
Setname ir_etd
ID 196975
Reference URL https://collections.lib.utah.edu/ark:/87278/s6cz6ggx
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