Tuning Pore Dimensions of Mesoporous Inorganic Films by Homopolymer Swelling

The functionality and applications of mesoporous inorganic films are closely linked to their mesopore dimensions. For material architectures derived from a block copolymer (BCP) micelle coassembly, the pore size is typically manipulated by changing the molecular weight corresponding to the pore-forming block. However, bespoke BCP synthesis is often a costly and time-consuming process. An alternative method for pore size tuning involves the use of swelling agents, such as homopolymers (HPs), which selectively interact with the core-forming block to increase the micelle size in solution. In this work, poly(isobutylene)-block-poly(ethylene oxide) micelles were swollen with poly(isobutylene) HP in solution and coassembled with aluminosilicate sol with the aim of increasing the resulting pore dimensions. An analytical approach implementing spectroscopic ellipsometry (SE) and ellipsometric porosimetry (EP) alongside atomic force microscopy (AFM) and small-angle X-ray scattering (SAXS) in transmission and grazing-incidence (GISAXS) modes enabled us to study the material evolution from solution processing through the manifestation of the mesoporous inorganic film after BCP removal. The in-depth SE/EP analysis evidenced an increase of more than 45% in mesopore diameter with HP swelling and a consistent scaling of the overall void volume and number of pores. Importantly, our analytical toolbox enabled us to study the effect of swelling on the connecting necks between adjacent pores, with observed increases as high as ≈35%, offering novel pathways to sensing, electrochemical, and other mass-transfer-dependent applications

Assessing the operating temperature of multi-junction solar cells with novel rear side layer stack and local electrical contacts

Sub-bandgap sunlight provides a source of heat generation in solar cells that is detrimental to performance, especially in space applications where heat dissipation is limited. In this work we assess the impact that an advanced rear-side contact scheme for multi-junction solar cells has on the cell temperature. Our results show that this scheme reduces the optical power absorption below the bandgap of germanium by 81% compared to a standard, full metallization design. Measurements of the electrical and thermal power fluxes performed in vacuum demonstrate that this lower near-infrared light absorption results in 8% less heat dissipated in the cell with the novel rear-side contact scheme when operating at 25 ºC. Modelling of the operating temperature for both cells when fully encapsulated with glass indicates that this effect will also result in a reduction of the operating temperature of 9 ºC for the novel design

Structural Characterization of Mesoporous Thin Film Architectures: A Tutorial Overview

Mesoporous thin film architectures are an important class of materials that exhibit unique properties, which include high surface area, versatile surface functionalization, and bicontinuous percolation paths through a broad library of pore arrangements on the 10 nm length scale. Although porosimetry of bulk materials via sorption techniques is common practice, the characterization of thin mesoporous films with small sample volumes remains a challenge. A range of techniques are geared toward providing information over pore morphology, pore size distribution, surface area and overall porosity, but none of them offers a holistic evaluation and results are at times inconsistent. In this work, we present a tutorial overview for the reliable structural characterization of mesoporous films. Three model samples with variable pore size and porosity prepared by block copolymer (BCP) coassembly serve for a rational comparison. Various techniques are assessed side-by-side, including scanning electron microscopy (SEM), atomic force microscopy (AFM), grazing incidence small-angle X-ray scattering (GISAXS), and ellipsometric porosimetry (EP). We critically discuss advantages and limitations of each technique and provide guidelines for reliable implementation

Current trends in research, development and production of prophylactic vaccines : Report of Vaccipharma 2015 Congress

On June 14-19, 2015, the IUPHAR Section of Immunopharmacology and the Cuban Society of Pharmacology, together with the Latin- American Association of Pharmacology (ALF), Finlay Vaccine Institute and other prestigious Cuban scientific institutions, organized the Congress VACCIPHARMA 2015 (3rd International Congress on Pharmacology of Vaccines), held as part of the First International Convention IMMUNOPHARMACOLOGY–VACCIPHARMA 2015 (Meliá Marina Varadero Hotel, in Varadero beach, Cuba) VACCIPHARMA 2015 was organised into two large Workshops, addressing topics related to the research, development, clinical evaluation, production and quality control of Therapeutic and Prophylactic Vaccines, respectively. At the same time the Workshop on Prophylactic Vaccines was integrated by several Symposiums, focused on meningococcal, pneumococcal, enteric, tuberculosis and pertussis vaccines. About 250 delegates, including 100 international researchers from 15 countries, attended this meeting. The Congress had a remarkable Opening Session, with a Key Lecture given by the outstanding scientist Professor Dr. Shiv Pillai (United States of America), who talked about the changing views in the field of the immunology of vaccination and the challenges ahead. The aim of this review is to give an overview of the main topics discussed in the Prophylactic Vaccines Workshop, not as a complete narration of the events, but to provide an update of the latest state of the art and methodologies being applied to prophylactic vaccines with an expert commentary on the invited speakers

Block Copolymer Directed Metamaterials and Metasurfaces for Novel Optical Devices

Optical metamaterials are artificially engineered architectures that exhibit desired optical properties not found in nature. Bespoke design requires the ability to define shape, size, orientation, and composition of material structures on the nanometer length scale. Bottom-up self-assembly methods, such as block copolymer (BCP) templating, offer unique pathways to tailored features, at spatial resolution not routinely achieved by conventional top-down techniques. In this review, the authors provide the general readership with basic concepts of the underlying fabrication processes and examine optical phenomena arising from BCP-derived metamaterials and nanoresonators, with both dielectric and plasmonic characteristics. A number of diverse structural conformations designed by BCP templating and their implementation in optical devices is evaluated. The discussion includes 3D metamaterials, such as gyroidal and hyperbolic arrangements, as well as 2D metasurfaces. Based on recent developments in exploring these emerging structural and material configurations, the review further highlights unexplored opportunities offered by BCP self-assembly for novel metamaterials and metasurface devices

Novel approaches to acoustic immunosensing of extracellular vesicles

Extracellular vesicles (EVs) constitute a promising source of biomarkers for disease diagnostics and can be obtained via liquid biopsies from various bodily fluids. While much progress has been made in recent years, challenges remain on the sensitivity, specificity and clinical implementation of current analytical workflows

Alterations in microbial community composition with increasing fCO2: a mesocosm study in the eastern Baltic Sea

Ocean acidification resulting from the uptake of anthropogenic carbon dioxide (CO₂) by the ocean is considered a major threat to marine ecosystems. Here we examined the effects of ocean acidification on microbial community dynamics in the eastern Baltic Sea during the summer of 2012 when inorganic nitrogen and phosphorus were strongly depleted. Large-volume in situ mesocosms were employed to mimic present, future and far future CO₂ scenarios. All six groups of phytoplankton enumerated by flow cytometry ( &lt;  20 µm cell diameter) showed distinct trends in net growth and abundance with CO₂ enrichment. The picoeukaryotic phytoplankton groups Pico-I and Pico-II displayed enhanced abundances, whilst Pico-III, <i>Synechococcus</i> and the nanoeukaryotic phytoplankton groups were negatively affected by elevated fugacity of CO₂ (<i>f</i>CO₂). Specifically, the numerically dominant eukaryote, Pico-I, demonstrated increases in gross growth rate with increasing <i>f</i>CO₂ sufficient to double its abundance. The dynamics of the prokaryote community closely followed trends in total algal biomass despite differential effects of <i>f</i>CO₂ on algal groups. Similarly, viral abundances corresponded to prokaryotic host population dynamics. Viral lysis and grazing were both important in controlling microbial abundances. Overall our results point to a shift, with increasing <i>f</i>CO₂, towards a more regenerative system with production dominated by small picoeukaryotic phytoplankton.</p

Photoinduced non-adiabatic energy transfer pathways in dendrimer building blocks

The efficiency of the intramolecular energy transfer in light harvesting dendrimers is determined by their well-defined architecture with high degree of order. After photoexcitation, through-space and through-bond energy transfer mechanisms can take place, involving vectorial exciton migration among different chromophores within dendrimer highly branched structures. Their inherent intramolecular energy gradient depends on how the multiple chromophoric units have been assembled, subject to their inter-connects, spatial distances, and orientations. Herein, we compare the photoinduced nonadiabatic molecular dynamics simulations performed on a set of different combinations of a chain of linked dendrimer building blocks composed of two-, three-, and four-ring linear polyphenylene chromophoric units. The calculations are performed with the recently developed ab initio multiple cloning-time dependent diabatic basis implementation of the Multiconfigurational Ehrenfest (MCE) approach. Despite differences in short time relaxation pathways and different initial exciton localization, at longer time scales, electronic relaxation rates and exciton final redistributions are very similar for all combinations. Unlike the systems composed of two building blocks, considered previously, for the larger 3 block systems here we observe that bifurcation of the wave function accounted by cloning is important. In all the systems considered in this work, at the time scale of few hundreds of femtoseconds, cloning enhances the electronic energy relaxation by ∼13% compared to that of the MCE method without cloning. Thus, accurate description of quantum effects is essential for understanding of the energy exchange in dendrimers both at short and long time scales