Photonic stop bands in quasi-random nanoporous anodic alumina structures

The existence of photonic stop bands in the self-assembled arrangement of pores in porous anodic alumina structures is investigated by means of rigorous 2D finite- difference time-domain calculations. Self-assembled porous anodic alumina shows a random distribution of domains, each of them with a very definite triangular pattern, constituting a quasi-random structure. The observed stop bands are similar to those of photonic quasicrystals or random structures. As the pores of nanoporous anodic alumina can be infiltrated with noble metals, nonlinear or active media, it makes this material very attractive and cost-effective for applications including inhibition of spontaneous emission, random lasing, LEDs and biosensors

Effect of the anodization voltage on the porewidening rate of nanoporous anodic alumina

A detailed study of the pore-widening rate of nanoporous anodic alumina layers as a function of the anodization voltage was carried out. The study focuses on samples produced under the same electrolyte and concentration but different anodization voltages within the self-ordering regime. By means of ellipsometry-based optical characterization, it is shown that in the porewidening process, the porosity increases at a faster rate for lower anodization voltages. This opens the possibility of obtaining three-dimensional nanostructured nanoporous anodic alumina with controlled thickness and refractive index of each layer, and with a refractive index difference of up to 0.24 between layers, for samples produced with oxalic acid electrolytes

Fabrication of self-ordered nanoporous alumina for optical and structural characterization

Presentem la fabricació, caracterització estructural i òptica de membranes d'alúmina nanoporosa autoordenada. Les mostres han estat fabricades per el procés de doble anodització. La morfologia de les membranes obtinguda mitjançant les diferents condicions d'anodització ha estat examinada amb un microscopi electrònic d'escombrat per tal d'estimar les seves propietats geomètriques. Les propietats estructurals estudiades mitjançant difracció de raigs X mostren que durant el procés de recuit termic, des de 600 ºC fins a 1200 ºC, l'alúmina nanoporosa ha cristal·litzat des de la fase amorfa fins a les formes gamma i alfa (cristal·lines). L'espectre de la transmissió òptica de les membranes d'alúmina porosa autoordenada va ser mesurat mitjançant un espectròmetre UV-VIS en el rang 300 - 1000 nmWe present the fabrication and optical and structural characterization of self-ordered nanoporous alumina membranes. The samples were fabricated using a two-step anodization process. The morphology of the membranes produced using different anodizing conditions was examined with a scanning electron microscope in order to estimate their geometrical properties. The structural properties studied by X-ray diffraction showed that nanoporous alumina is crystallized from amorphous phase to gamma and alpha (crystalline) forms during annealing at 600 ºC to 1200 ºC. The optical transmission spectra of the membranes were measured using a UV-VIS spectrometer in the range of 300 - 1000 nm

Diphenylphenoxy-Thiophene-PDI Dimers as Acceptors for OPV Applications with Open Circuit Voltage Approaching 1 Volt

Two new perylenediimides (PDIs) have been developed for use as electron acceptors in solution-processed bulk heterojunction solar cells. The compounds were designed to exhibit maximal solubility in organic solvents, and reduced aggregation in the solid state. In order to achieve this, diphenylphenoxy groups were used to functionalize a monomeric PDI core, and two PDI dimers were bridged with either one or two thiophene units. In photovoltaic devices prepared using PDI dimers and a monomer in conjunction with PTB7, it was found that the formation of crystalline domains in either the acceptor or donor was completely suppressed. Atomic force microscopy, X-ray diffraction, charge carrier mobility measurements and recombination kinetics studies all suggest that the lack of crystallinity in the active layer induces a significant drop in electron mobility. Significant surface recombination losses associated with a lack of segregation in the material were also identified as a significant loss mechanism. Finally, the monomeric PDI was found to have sub-optimum LUMO energy matching the cathode contact, thus limiting charge carrier extraction. Despite these setbacks, all PDIs produced high open circuit voltages, reaching almost 1 V in one particular caseThis work was supported by the Spanish Ministry of Economy, Industry and Competitiveness (MEIC) (TEC2015-71324-R, CTQ2014-55798-R and TEC2015-71915-REDT (MINECO/FEDER))This work was supported by the Catalan Institution for Research and Advanced Studies (ICREA) (ICREA “Academia Award”, AGAUR 2017 SGR 017SGR1527

Achieving orphan designation for placental insufficiency: annual incidence estimations in Europe

Objective To determine whether a novel therapy for placental insufficiency could achieve orphan drug status by estimating the annual incidence of placental insufficiency, defined as an estimated fetal weight below the 10th centile in the presence of abnormal umbilical artery Doppler velocimetry, per 10 000 European Union (EU ) population as part of an application for European Medicines Agency (EMA ) orphan designation. Design Incidence estimation based on literature review and published national and EU statistics. Setting and population European Union. Methods Data were drawn from published literature, including national and international guidelines, international consensus statements, cohort studies and randomised controlled trials, and published national and EU statistics, including birth rates and stillbirth rates. Rare disease databases were also searched. Results The proportion of affected pregnancies was estimated as 3.17% (95% CI 2.93–3.43%), using a weighted average of the results from two cohort studies. Using birth rates from 2012 and adjusting for a pregnancy loss rate of 1/100 gave an estimated annual incidence of 3.33 per 10 000 EU population (95% CI 3.07–3.60 per 10 000 EU population). This fell below the EMA threshold of 5 per 10 000 EU population. Conclusions Maternal vascular endothelial growth factor gene therapy for placental insufficiency was granted EMA orphan status in 2015 after we demonstrated that it is a rare, life‐threatening or chronically debilitating and currently untreatable disease. Developers of other potential obstetric therapies should consider applying for orphan designation, which provides financial and regulatory benefits

Stacked nanoporous anodic alumina gradient-index filters with tunable multispectral photonic stopbands as sensing platforms

This study presents the development and optical engineering of stacked nanoporous anodic alumina gradient-index (NAA-GIFs) filters with tunable multispectral photonic stopbands for sensing applications. The structure of these photonic crystals (PC) is formed by stacked layers of NAA produced with sinusoidally modified effective medium. The progressive modification of the sinusoidal period during the anodization process enables the generation and precise tuning of the characteristic photonic stopbands (PSB) (i.e., one per sinusoidal period in the anodization profile) of these PC structures. Four types of NAA-GIFs featuring three distinctive PSBs positioned within the visible spectral region are developed. The sensitivity of the effective medium of these NAA-GIFs is systematically assessed by measuring spectral shifts in the characteristic PSBs upon infiltration of their nanoporous structure with analytical solutions of d-glucose with several concentrations (0.025–1 M). This study provides new insights into the intrinsic relationship between the nanoporous architecture of these PCs and their optical properties, generating opportunities to fabricate advanced optical sensing systems for high-throughput and multiplexed detection of analytes in a single sensing platform.Laura K. Acosta, Francesc Bertó-Roselló, Elisabet Xifre-Perez, Abel Santos, Josep Ferré-Borrull, and Lluis F. Marsa