Browsing by Author "Losic, D"

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    Atomic layer deposition of SIO2 on porous alumina membranes: controlling the pore size and transport properties
    (SPIE, 2008-12-30) Velleman, L; Triani, G; Evans, PJ; Atanacio, AJ; Shapter, JG; Losic, D
    Atomic layer deposition (ALD) of SiO2 onto nanoporous alumina (PA) membranes was investigated with the aim of adjusting the pore size and transport properties. PA membranes from commercial sources with a range of pore diameters (20 nm, 100 nm and 200 nm) were used and modified by atomic layer deposition using tris(tert-butoxy)silanol and water as the precursor couple. By adjusting the number of deposition cycles, the thickness of the conformal silica coating was controlled, reducing the effective pore diameter, and subsequently changing the transport properties of the PA membrane. Silica coated PA membranes with desired pore diameters from <5 nm to 100 nm were fabricated. In addition to the pore size, the transport properties and selectivity of fabricated silica coated PA membranes were controlled by chemical functionalisation using a silane with hydrophobic properties. Structural and chemical properties of modified membranes were studied by dynamic secondary ion mass spectrometry (DSIMS) and scanning electron microscopy (SEM). Spectrophotometric methods were used to evaluate the transport properties and selectivity of silica coated membranes by permeation studies of hydrophobic and hydrophilic organic molecules. The resultant silica/PA membranes with specific surface chemistry and controlled pore size are applicable for molecular separation, cell culture, bioreactors, biosensing and drug delivery. © 2008 Society of Photo-Optical Instrumentation Engineers (SPIE)
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    Controlled pore structure modification of diatoms by atomic layer deposition of TiO2
    (Royal Society of Chemistry, 2006-09-04) Losic, D; Triani, G; Evans, PJ; Atanacio, AJ; Mitchell, JG; Voelcker, NH
    Diatoms produce diverse three-dimensional, regular silica structures with nanometer to micrometer dimensions and hold considerable promise for biological or biomimetic fabrication of nanostructured materials and devices. The unique hierarchical porous structure of diatom frustules is in particular attractive for membrane applications in microfluidic systems. In this paper, a procedure for pore size modifications of two centric diatom species, Coscinodiscus sp. and Thalassiosira eccentrica (T. eccentrica) using the atomic layer deposition (ALD) of ultrathin films of titanium oxide (TiO2) is described. TiO2 is deposited by sequential exposures to titanium chloride (TiCl4) and water. The modified diatom membranes were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray analysis (EDAX), and secondary ion mass spectrometry (SIMS). These techniques confirmed the controlled reduction of pore sizes while preserving the shape of the diatom membrane pores. Pore diameters of diatom membranes can be further tailored for specific applications by varying the number of cycles and by changing their surface functionality.© The Royal Society of Chemistry 2006
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    Fabrication of titania nanotube membranes by atomic layer deposition using nanoporous alumina as a template
    (Engineers Australia, 2011-09-18) Evans, PJ; Triani, G; Nambiar, M; Shapter, JG; Losic, D
    Conformal TiO2 films have been deposited onto highly oriented porous alumina arrays to characterise membranes with controlled pore modification. A suite of tools have been used to probe the evolution of these coated porous structures. Depth profiling by secondary ion mass spectroscopy revealed the distribution of elements Ti and O deposited throughout the coated porous alumina. High resolution imaging using scanning electron microscopy confirmed the reduction in pore-size as a function of deposition cycles. Following the removal of the porous alumina template, free-standing titania nanotubes were prepared which show the pore geometry of the alumina template was preserved. ©2011 Engineers Australia
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    Structural and chemical modification of porous alumina membranes
    (Elsevier, 2009-11) Velleman, L; Triani, G; Evans, PJ; Shapter, JG; Losic, D
    Structural and chemical modification of porous anodic alumina (AAO) membranes was investigated with the aim of fine-tuning pore diameters and chemical selectivity. AAO membranes from commercial sources with pore diameters (20, 100 and 200 nm) were used as the substrate. Atomic layer deposition (ALD) of silica (SiO2) has been used for membrane structural modification using tris(tert-butoxy)silanol and trimethylaluminium as the precursor couple. By adjusting the number of ALD deposition cycles (3–20), the effective pore diameter of AAO membranes was significantly reduced to desired values (<10 nm) improving the separation properties of commercial membranes. The chemical functionalization of silica coated AAO membranes with a perfluorodecyldimethylchlorosilane (PFDS) shows that the transport and selectivity properties of silica composite AAO membranes can be varied by functionalization using silane chemistry. The hydrophobic PFDS-modified membranes showed enhanced sensitivity (flux ratio 5.52) to the transport of hydrophobic molecules (tris(2,2′-bipyridyl)dichlororuthenium(II) hexahydrate (Rubpy), over hydrophilic molecules (rose bengal (RB)). Structural and chemical properties of modified membranes were confirmed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDAX), dynamic secondary ion mass spectrometry (DSIMS), and contact angle measurements. The resultant silica coated commercial AAO membranes with specific surface chemistry and controlled pore size are applicable for advanced molecular separation, cell culture, tissue engineering, biosensing and drug delivery. © 2009, Elsevier Ltd.
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    Study of titania modified porous alumina membranes for protein transport and separation
    (Engineers Australia, 2011-09-18) Nambiar, M; Evans, PJ; Triani, G; Shapter, JG; Losic, D
    The use of nanoporous membranes in molecular separation or sieving, which involve the separation of molecular mixtures, is gaining rapid interest. The ability to modify and alter their pore size and dimensions, along with the physical and chemical properties of the material that constitute these pores make them highly sensitive to such applications, particularly protein separation. Our study investigated the use of titania modified porous anodic alumina (AAO) membranes. Titania was deposited using atomic layer deposition (ALD) for different number of cycles in order to generate membranes with reduced poresizes ranging from 100nm-10nm. Protein permeation experiments using bovine serum albumin (BSA) and Lysozyme (Lys) were conducted to show selectivity in transport and separation of the proteins. Transport occurred by diffusion and a subsequent decrease in flow rate was observed with decrease in pore size of the membranes. In addition, the use of titania modified AAO membranes demonstrated minimal extent of non-specific absorption of proteins along the pores during permeation when subject to UV radiation. The resultant titania coated AAO membranes achieved controlled reduction of pore size using ALD and are thus, applicable for advanced protein transport, separation and catalysis. © 2011 Engineers Australia