A Library of Late Transition Metal Alloy Dielectric Functions for Nanophotonic Applications

Accurate complex dielectric functions are critical to accelerate the development of rationally designed metal alloy systems for nanophotonic applications, and to thereby unlock the potential of alloying for tailoring nanostructure optical properties. To date, however, accurate alloy dielectric functions are widely lacking. Here, a time‐dependent density‐functional theory computational framework is employed to compute a comprehensive binary alloy dielectric function library for the late transition metals most commonly employed in plasmonics (Ag, Au, Cu, Pd, Pt). Excellent agreement is found between electrodynamic simulations based on these dielectric functions and selected alloy systems experimentally scrutinized in 10 at% composition intervals. Furthermore, it is demonstrated that the dielectric functions can vary in very non‐linear fashion with composition, which paves the way for non‐trivial optical response optimization by tailoring material composition. The presented dielectric function library is thus a key resource for the development of alloy nanomaterials for applications in nanophotonics, optical sensors, and photocatalysis.     

Metal-Mediated Base Pairing of Rigid and Flexible Benzaldoxime Metallacycles

Oligonucleotides incorporating a central C-nucleoside with either a rigid or flexible benzaldoxime base moiety have been synthesized, and the hybridization properties of their metallacyclic derivatives have been studied by UV melting experiments. In all cases, the metallated duplexes were less stable than their unmetallated counterparts, and the metallacyclic nucleobases did not show a clear preference for any of the canonical nucleobases as a base-pairing partner. With palladated oligonucleotides, increased flexibility translated to less severe destabilization, whereas the opposite was true for the mercurated oligonucleotides; this reflects the greater difficulties in accommodating a rigid Pd^II-mediated base pair than a rigid Hg^II-mediated base pair within the base stack of a double helix.     

Prolonged Dye Release from Mesoporous Silica‐Based Imaging Probes Facilitates Long‐Term Optical Tracking of Cell Populations In Vivo

Nanomedicine is gaining ground worldwide in therapy and diagnostics. Novel nanoscopic imaging probes serve as imaging tools for studying dynamic biological processes in vitro and in vivo. To allow detectability in the physiological environment, the nanostructure‐based probes need to be either inherently detectable by biomedical imaging techniques, or serve as carriers for existing imaging agents. In this study, the potential of mesoporous silica nanoparticles carrying commercially available fluorochromes as self‐regenerating cell labels for long‐term cellular tracking is investigated. The particle surface is organically modified for enhanced cellular uptake, the fluorescence intensity of labeled cells is followed over time both in vitro and in vivo. The particles are not exocytosed and particles which escaped cells due to cell injury or death are degraded and no labeling of nontargeted cell populations are observed. The labeling efficiency is significantly improved as compared to that of quantum dots of similar emission wavelength. Labeled human breast cancer cells are xenotransplanted in nude mice, and the fluorescent cells can be detected in vivo for a period of 1 month. Moreover, ex vivo analysis reveals fluorescently labeled metastatic colonies in lymph node and rib, highlighting the capability of the developed probes for tracking of metastasis.     

Modulating the Mechanical Performance of Macroscale Fibers through Shear‐Induced Alignment and Assembly of Protein Nanofibrils

Protein‐based fibers are used by nature as high‐performance materials in a wide range of applications, including providing structural support, creating thermal insulation, and generating underwater adhesives. Such fibers are commonly generated through a hierarchical self‐assembly process, where the molecular building blocks are geometrically confined and aligned along the fiber axis to provide a high level of structural robustness. Here, this approach is mimicked by using a microfluidic spinning method to enable precise control over multiscale order during the assembly process of nanoscale protein nanofibrils into micro‐ and macroscale fibers. By varying the flow rates on chip, the degree of nanofibril alignment can be tuned, leading to an orientation index comparable to that of native silk. It is found that the Young's modulus of the resulting fibers increases with an increasing level of nanoscale alignment of the building blocks, suggesting that the mechanical properties of macroscopic fibers can be controlled through varying the level of ordering of the nanoscale building blocks. Capitalizing on strategies evolved by nature, the fabrication method allows for the controlled formation of macroscopic fibers and offers the potential to be applied for the generation of further novel bioinspired materials.     

Modeling the importance of biota and black carbon as vectors of polybrominated diphenyl ethers (PBDEs) in the Baltic Sea ecosystem

The POPCYCLING-Baltic model, a nonsteady state spatially resolved mass balance model of chemical transport in the Baltic Sea environment was modified to include black carbon (BC), dissolved organic carbon (DOC) and food-web bioaccumulation. The importance of these modifications to the transport of PBDE congeners BDE-47, -99, -153, and -209 was assessed by comparing time-series simulated with and without black carbon and biota between 1970 and 2005. Inclusion of black carbon improved the model fit to measurements from air, soil, and biota, and had a major effect on the mass balance. Modeled bulk concentrations of PBDEs in sediments and soils increased by a factor of 3 while concentrations in biota decreased by a factor of 2-5. Black carbon also doubled the recovery time of the system due to the limited availability of PBDEs for degradation. In comparison, the inclusion of biota had only a minor effect on the overall mass balance and recovery times. The modified model is constructed as a flexible matrix and can also be applied to persistent organic pollutants in other ecosystems besides the Baltic Sea.     

Crosslinkable poly(lactic acid)‐based materials: Biomass‐derived solution for barrier coatings

The demand for biobased barrier packaging alternatives is constantly growing. Poly(lactic acid) (PLA)‐based polymers are one of the most extensively studied biomass‐derived synthetic polymers; however, they typically lack water‐barrier properties. We synthesized a copolymer of d ,l ‐lactic acid, 1,4‐butanediol, and itaconic acid [poly(d ,l ‐lactic acid–1,4‐butanediol–itaconic acid) (PLABDIA)] via bulk polycondensation. The radical crosslinking reactions of the synthesized polymer were investigated with bulk crosslinking trials to find a formulation that was suitable for a rapidly crosslinkable barrier coating. The crosslinking efficiency was tested with methacrylate and acrylate crosslinkers together with peroxide radical initiators. Poly(ethylene glycol) diacrylate (number‐average molecular weight = 250 g/mol) together with dilauroyl peroxide proved to be the best crosslinker–initiator combination. An aqueous dispersion of PLABDIA was prepared with a thermomechanical method and applied to commercial boxboard on a pilot‐scale line coater. With a coating weight of 10 g/m², a water vapor transmission rate of 22.8 g/m²d was achieved, and this coating outperformed commercial extruded PLA coatings. The samples also showed very good grease resistance and would, therefore, be a good solution for the packaging of dry and fatty goods. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44326.     

Incorporation of reactive silver‐tricalcium phosphate nanoparticles into polyamide 6 allows preparation of self‐disinfecting fibers

Polymer fibers are used for a wide range of materials in contact with the human body. Since bacterial contamination may cause diseases, it is desirable to provide fibers with antimicrobial properties. This work investigates the ability of silver‐tricalcium phosphate nanoparticles (Ag/TCP) to build a reactive system when incorporated in polyamide fibers. In the presence of bacteria, the TCP carrier particles are biodegraded and trigger the release of silver. For this work, Ag/TCP nanoparticles (1.3 wt% silver) were produced by flame spray synthesis and subsequently processed with polyamide 6 to fibers (125‐μm thick, containing 260 ppm silver) with the aid of extrusion and melt‐spinning for subsequent antibacterial testing. The fibers were contaminated with the clinically relevant strains Escherichia coli or Streptococcus sanguinis, respectively. The reactive fibers demonstrated significantly reduced plate count within 24 h (the number of colony forming units was reduced by 99.999% with E. coli and 99.6% with S. sanguinis compared with pure PA6 reference fibers). These reactive properties of easily integrated antibacterial silver suggest an implementation of intelligent fibers to a wide range of applications. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Filter Clogging by Bimodal Aerosol

Pressure drop evolution during filtration of bimodal aerosol was studied experimentally. A low-pressure drop pre-filter upstream of the actual collection filter was demonstrated to significantly reduce the pressure drop growth rate, when the aerosol is dominated by coarse particles. The pressure drop evolution during depth-filtration, that took place mainly in a pre-filter, could be predicted by adding up the separately measured contributions from the unimodal fine and coarse aerosols. However, the cake filtration (pre-filter was not used) of coarse particles alone resulted in a faster clogging rate as compared to the same amount of coarse particles accompanied with fine particles (mass ratio coarse:fine 3:1). Apparently, fine particles deposited on coarse particles affect their surface properties and thus the porosity of the cake formed.