Structural tuning of photoluminescence in nanoporous anodic alumina by hard anodization in oxalic and malonic acids

We report on an exhaustive and systematic study about the photoluminescent properties of nanoporous anodic alumina membranes fabricated by the one-step anodization process under hard conditions in oxalic and malonic acids. This optical property is analysed as a function of several parameters (i.e. hard anodization voltage, pore diameter, membrane thickness, annealing temperature and acid electrolyte). This analysis makes it possible to tune the photoluminescent behaviour at will simply by modifying the structural characteristics of these membranes. This structural tuning ability is of special interest in such fields as optoelectronics, in which an accurate design of the basic nanostructures (e.g. microcavities, resonators, filters, supports, etc.) yields the control over their optical properties and, thus, upon the performance of the nanodevices derived from them (biosensors, interferometers, selective filters, etc.).Abel Santos, Maria Alba, Mahbubur M Rahman, Pilar Formentín, Josep Ferré-Borrull, Josep Pallarès, Lluis F Marsa

Tunable Fabry-Perot interferometer based on nanoporous anodic alumina for optical biosensing purposes

Here, we present a systematic study about the effect of the pore length and its diameter on the specular reflection in nanoporous anodic alumina. As we demonstrate, the specular reflection can be controlled at will by structural tuning (i.e., by designing the pore geometry). This makes it possible to produce a wide range of Fabry-Pérot interferometers based on nanoporous anodic alumina, which are envisaged for developing smart and accurate optical sensors in such research fields as biotechnology and medicine. Additionally, to systematize the responsiveness to external changes in optical sensors based on nanoporous anodic alumina, we put forward a barcode system based on the oscillations in the specular reflection.Abel Santos, Victor S Balderrama, María Alba, Pilar Formentín, Josep Ferré-Borrull, Josep Pallarès, Lluís F Marsa

Photoluminescence and cathodoluminescence of Eu:La2O3 nanoparticles synthesized by several methods

Abstract : Europium-doped La2O3 nanocrystalline powders with sizes ranging from 4 nm to 300 nm have been obtained by the modified Pechini, hydrothermal with conventional furnace, hydrothermal with microwave furnace, and precipitation with ultrasonic bath methods. X-ray diffraction techniques were used to study the evolution of the prepared gels towards the desired crystalline phase. We determined the size and the morphology of the nanoparticles by electronic microscopy. Finally, we studied and analyzed the luminescence properties of the trivalent europium in the hexagonal La2O3 nanocrystals by photoluminescence and cathodoluminescence

Nanoporous anodic alumina obtained without protective oxide layer by hard anodization

Abstract not availableA. Santos, P. Formentín, J. Ferré-Borrull, J. Pallarès, L.F. Marsa

Effects of the nanostructure and fabrication process on the photoluminescence properties of PFO nanopillar arrays

Abstract not availableLluis F. Marsal, Raquel Palacios, Pilar Formentín, Abel Santos, Josep Ferré-Borrull and Josep Pallarè

Collagen and fibronectin surface modification of nanoporous anodic alumina and macroporous silicon for endothelial cell cultures

Abstract Background The ability to direct the cellular response by means of biomaterial surface topography is important for biomedical applications. Substrate surface topography has been shown to be an effective cue for the regulation of cellular response. Here, the response of human aortic endothelial cells to nanoporous anodic alumina and macroporous silicon with collagen and fibronectin functionalization has been studied. Methods Confocal microscopy and scanning electron microscopy were employed to analyse the effects of the material and the porosity on the adhesion, morphology, and proliferation of the cells. Cell spreading and filopodia formation on macro- and nanoporous material was characterized by atomic force microscopy. We have also studied the influence of the protein on the adhesion. Results It was obtained the best results when the material is functionalized with fibronectin, regarding cells adhesion, morphology, and proliferation. Conclusion These results permit to obtain chemical modified 3D structures for several biotechnology applications such as tissue engineering, organ-on-chip or regenerative medicine

Effect of the La(OH)3 preparation method on the surface and rehydroxylation properties of resulting La2O3 nanoparticles

10.1007/s11051-013-1479-7Several lanthanum hydroxides (28¿146 m2/g) were prepared by different procedures involving precipitation and hydrothermal methods by conventional heating or with microwaves. The use of ultrasounds during precipitation led to the formation of additional crystalline phases whereas the aging treatment with microwaves decreased the temperature needed to form the lanthanum oxide phase when compared with the samples aged by conventional heating. After calcination, La2O3 samples showed similar BET surface areas (3¿5 m2/g) but different particle sizes ranging from 150 to 600 nm depending on the La(OH)3 preparation method, as observed by TEM. La2O3 samples were completely rehydroxylated after 80 h of exposure to atmospheric air at controlled humidity conditions recovering only partially the surface areas of the La(OH)3 precursors (14¿18 m2/g). The progress of rehydroxylation with time occurred in several steps at different rates. Rehydroxylation rate mainly depended on the particle size and surface area of the lanthanum oxide sample. Therefore, the method used to prepare the initial lanthanum hydroxide affects the surface and rehydroxylation properties of the subsequent lanthanum oxide sample

Nanoporous anodic alumina barcodes: toward smart optical biosensors

Toward a smart optical biosensor based on nanoporous anodic alumina (NAA): by modifying the pore geometry in nanoporous anodic alumina we are able to change the effective medium at will and tune the photoluminescence of NAA. The oscillations in the PL spectrum are converted into exclusive barcodes, which are useful for developing optical biomedical sensors in the UV-Visible region.Abel Santos, Victor S. Balderrama, María Alba, Pilar Formentín, Josep Ferré-Borrull, Josep Pallarès and Lluís F. Marsa

Synthesis of Ordered Polymer Micro and Nanostructures Via Porous Templates

The deposition of specific materials into ordered pores arranged in a regular lattice allows the fabrication of ordered fiber arrays. Polymer micro- and nanofibers using macroporous silicon and nanoporous alumina templates were fabricated employing a vacuum infiltration method for Poly(methyl methacrylate) (PMMA) structures or a melt-assisted template wetting into the pores for Poly(3-hexylthiophene) (P3HT) structures. We have studied how the aspect ratio of the micro- and nanopores and the kind of polymer influence the structures fabrication.Peer Reviewe

Synthesis of ordered polymer micro and nanostructures via porous templates

The deposition of specific materials into ordered pores arranged in a regular lattice allows the fabrication of ordered fiber arrays. Polymer micro- and nanofibers using macroporous silicon and nanoporous alumina templates were fabricated employing a vacuum infiltration method for Poly(methyl methacrylate) (PMMA) structures or a melt-assisted template wetting into the pores for Poly(3-hexylthiophene) (P3HT) structures. We have studied how the aspect ratio of the micro- and nanopores and the kind of polymer influence the structures fabrication.Peer Reviewe