The morphology of bulk heterojunction organic photovoltaic cells controls many of the performance characteristics of devices. However, measuring this morphology is challenging because of the small length-scales and low contrast between organic materials. Here we use nanoscale photocurrent mapping, ultrafast fluorescence and exciton diffusion to observe the detailed morphology of a high-performance blend of PTB7:PC71BM. We show that optimized blends consist of elongated fullerene-rich and polymer-rich fibre-like domains, which are 10–50 nm wide and 200–400 nm long. These elongated domains provide a concentration gradient for directional charge diffusion that helps in the extraction of charge pairs with 80% efficiency. In contrast, blends with agglomerated fullerene domains show a much lower efficiency of charge extraction of ~45%, which is attributed to poor electron and hole transport. Our results show that the formation of narrow and elongated domains is desirable for efficient bulk heterojunction solar cells.

Optical spectroscopic methods do not routinely provide information on higher order hierarchical structure (tertiary/quaternary) of biological macromolecules and assemblies. This necessitates the use of time-consuming and material intensive techniques, such as protein crystallography, NMR, and electron microscopy. Here we demonstrate a spectroscopic phenomenon, superchiral polarimetry, which can rapidly characterize ligand-induced changes in protein higher order (tertiary/quaternary) structure at the picogram level, which is undetectable using conventional CD spectroscopy. This is achieved by utilizing the enhanced sensitivity of superchiral evanescent fields to mesoscale chiral structure.

effectively a disposable consumable, with properties which can be easily tuned in the production process.The TPSs we generated can be considered to be hybrid structures, referred to as a solid-inverse structure, consisting of a solid nanostructure and an identical shaped void (inverse structure) directly above it. In line with Babinet's principle, the roles of electric and magnetic fi elds are switched between solid and inverse structures. The implications of this are that symmetry equivalent electric and magnetic modes of the solid and inverse structures are spatially located directly above each other, and can consequently couple in an analogous manner to hybridization of orbitals in molecular systems. [ 23 ] We show with our chiral hybrid metafi lms, that by controlling the spatial overlap between the solid and inverse structure, using fi lm thickness, the coupling between electric and magnetic modes can be controlled enabling the chiral/optical properties to be manipulated with relative ease. This is a far more versatile approach to manipulating coupling in hybrid metamaterials than the current paradigm of altering the geometric design. [ 24 ] Our work demonstrates that fi lm thickness is an important parameter in the metamaterial design tool kit. To illustrate the potential of the tunable "disposable" TPS, we present an exemplar case where a chiral substrate, consisting of a periodic array of "shuriken" indentations which are either left (LH) or right handed (RH), is used for picogram characterization of protein structure with "plasmonic polarimetry." [ 5 ] The combination of the low cost injection-molded templates and the tunability of the fi lms they can be used to produce, make the present study a signifi cant step in the technological application of metamaterials.The shuriken TPSs were fabricated using a new approach for templating Au fi lms on nanostructured polycarbonate substrates. Injection molding enables high-throughput manufacturing of sub-micrometer resolution nanosurfaces with high levels of reproducibility and quality. [ 21,25 ] In this work, we fabricate injection-molded polycarbonate templates, Figure 1 A, that consists of chiral shuriken shaped indentations, of either left or right handedness, arranged in a square lattice. A detailed description of the injection-molding process can be found elsewhere. [ 16,19,22,26 ] The depth of the indentation is 80 nm while the distance from the end of one arm to that of the end of the arm opposite is 500 nm. The periodicity of the array is 700 nm. Due to the nature of injection molding, the edges of the structure are not perfectly sharp and the inner walls of the structures are sloped by approximately 30° (see Supporting Information).We deposited fi lms of Au with thickness ranging from 20 to 100 nm on to the nanostructured polycarbonate template to produce the TPS samples, Figure 1 B,C. The continuous nature of the Au fi lms is evidenced by an absence of charging in scanning electron microscope (SEM) images of the substrates (see Artifi cially engineere...

Hydrogen bonded interactions are among the most important non-covalent interactions in supramolecular chemistry. The strength, selectivity and directionality inherent in hydrogen bonding processes have allowed the creation of complex and efficient molecular hosts capable of selective binding to a wide variety of complementary guests. Major advances in controlling host-guest complexation have occurred in the last decade, principally through systematic modification of the electrostatic properties and/or geometry of the hosts, thereby fine-tuning the molecular recognition event. More recently, systems have been developed which allow the effectiveness and selectively of hydrogen bonding interactions to be reversibly modulated by an external stimulus, more accurately mimicking biological systems and providing building blocks for the construction of novel advanced materials, sensors and devices. In this review, we highlight some of the methods available for modulating the strength and selectivity of hydrogen bonded interactions in synthetic host-guest systems.

In this article, we report the formation of micelles from a tetrathiafulvalene (TTF) end-functionalized poly(N-isopropylacrylamide) (poly(NIPAM)) derivative (1). We have determined the critical aggregation concentration (CAC) and average diameter of the micelles using fluorescence spectroscopy and dynamic light scattering experiments, respectively. We have exploited the NIPAM backbone of the polymer to thermally transform the swollen hydrophilic poly(NIPAM) derivative to a more globular hydrophobic state at the lower critical solution temperature (LCST). Finally, we have shown that we can exploit the chemical oxidation and complexation properties of the TTF unit to disrupt the micelle architecture to release the hydrophobic dye Nile Red from the interior of the micelle.