Thermal vibrations and the dynamic disorder they create can detrimentally affect the transport properties of van der Waals bonded molecular semiconductors. The low-energy nature of these vibrations makes it difficult to access them experimentally, which is why we still lack clear molecular design rules to control and reduce dynamic disorder. In this study we discuss the promising organic semiconductors rubrene, 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothio-phene and 2,9-di-decyl-dinaphtho-[2,3-b:20,30-f]-thieno-[3,2-b]-thiophene in terms of an exceptionally low degree of dynamic disorder. In particular, we analyse diffuse scattering in transmission electron microscopy, to show that small molecules that have their side chains attached along the long axis of their conjugated core are better encapsulated in their crystal structure, which helps reduce large-amplitude thermal motions. Our work provides a general strategy for the design of new classes of very high mobility organic semiconductors with a low degree of dynamic disorder.

Many of the remarkable electrical and optical properties of organic semiconductors are governed by the interaction of electronic excitations with intra- and intermolecular vibrational modes. However, in specific systems this interaction is not understood in detail at a molecular level and this has been due, at least in part, to the lack of easy-to-use and widely available experimental probes of the structural dynamics. Here we demonstrate that thermal diffuse scattering in electron diffraction patterns from organic semiconductors, such as 6,13-bistriisopropyl-silylethynyl pentacene, allows the dominant lattice vibrational modes to be probed directly. The amplitude and direction of the dominant molecular motions were determined by comparison of the diffuse scattering with simulations and molecular dynamics calculations. Our widely applicable approach enables a much deeper understanding of the structural dynamics in a broad range of organic semiconductors.

In the 20 years since precession electron diffraction (PED) was introduced, it has grown from a little-known niche technique to one that is seen as a cornerstone of electron crystallography. It is now used primarily in two ways. The first is to determine crystal structures, to identify lattice parameters and symmetry, and ultimately to solve the atomic structure ab initio. The second is, through connection with the microscope scanning system, to map the local orientation of the specimen to investigate crystal texture, rotation and strain at the nanometre scale. This topical review brings the reader up to date, highlighting recent successes using PED and providing some pointers to the future in terms of method development and how the technique can meet some of the needs of the X-ray crystallography community. Complementary electron techniques are also discussed, together with how a synergy of methods may provide the best approach to electron-based structure analysis.

Metal fluorides, promising lithium-ion battery cathode materials, have been classified as conversion materials, due to the reconstructive phase transitions widely presumed to occur upon lithiation. We challenge this view by studying FeF3 using X-ray total scattering and electron diffraction techniques that measure structure over multiple length-scales coupled with DFT calculations, and by revisiting prior experimental studies of FeF2 and CuF2. Metal fluoride lithiation is instead dominated by diffusioncontrolled displacement mechanisms, a clear topological relationship between the metal fluoride Fsublattices and that of LiF being established. Initial lithiation of FeF3 forms FeF2 on the particle's surface, along with a cation-and stacking-disordered phase, A-LixFeyF3 -structurally related to α-/β-LiMn 2+ Fe 3+ F6, which topotactically transforms to Band then C-LixFeyF3, before forming LiF and Fe. Lithiation of FeF2 and CuF2 results in a buffer phase between FeF2/CuF2 and LiF. The resulting principles will aid future developments of a wider range of isomorphic metal fluorides.

Both magnetic and plasmonic particles are of increasing interest for biomedical applications. Magnetic particles are currently used for magnetic separation, to collect tagged cells or DNA sequences, [1][2][3] and for magnetically guided drug delivery. [4][5][6] A key advantage of magnetism lies in the ability to control motion at a distance without perturbing the biological system, as would occur with a large electric field. Noble-metal nanostructures are beneficial not only because of their relative ease of biofunctionalization, but also for plasmonic biosensing. [7][8][9][10] Unlike quantum dots, [11] these particles do not show optical bistability or blinking making them competitive with fluorophores for quantifying the number of cell surface markers. [12,13] The main advantages of plasmonic particles are their extremely large molar extinction coefficients and resonant Rayleigh scattering efficiencies, [8] and the exceptional sensitivity of the surface plasmon resonance peak wavelength to changes in the local dielectric environment. Individual plasmonic nanoparticles and nanorods have been detected by using dark field optical microscopy. [13][14][15][16][17] In fact, by using nonmagnetically responsive gold-coated silica particles ($150 nm), Halas and co-workers have demonstrated the capability of gold-shell nanoparticles in detecting low concentrations of analytes in whole blood within minutes without any sample preparation.[18]Here we describe the preparation of iron oxide/gold core/ shell nanoparticles that can be moved magnetically and imaged optically. The synthesis of large-diameter ($150 nm) magnetic plasmonic three-layer composite particles has previously been reported, [19] but our focus here is on smaller particles. The small size of these nanoparticles approaches that of cellmembrane-bound antigens, and is in a range in which particles can be spontaneously internalized by endocytosis. We expect that the combination of magnetic responsiveness, facile bioconjugation, and a localized surface plasmon resonance in these smaller nanoparticles will open new possibilities for in vitro molecular and cell biological applications, including intracellular mechanical and chemical composition analyses, and magnetophoretic cell sorting according to the expression level of cell surface receptors. The magnetic forcẽ F m ¼ ðm pt Á rÞB * that can be applied to a particle depends on the particle magnetic moment m pt . Since m pt ¼ M s V pt , where M s is the saturation magnetization of the material and V pt is the particle volume, a larger size is generally preferable for a strong magnetic response. Thus there is a compromise between large magnetic moments and the desirability of small sizes for new applications.Gold, silver, and SiO 2 core/Au shell particles have been used for plasmonic sensing, where the surface plasmon peak wavelength shifts in response to small changes in the dielectric environment near the particle surface. A core/shell structure with the noble metal in the shell enables the surface plasmon resona...

Meteorites contain a record of their thermal and magnetic history, written in the intergrowths of iron-rich and nickel-rich phases that formed during slow cooling. Of intense interest from a magnetic perspective is the “cloudy zone,” a nanoscale intergrowth containing tetrataenite—a naturally occurring hard ferromagnetic mineral that has potential applications as a sustainable alternative to rare-earth permanent magnets. Here we use a combination of high-resolution electron diffraction, electron tomography, atom probe tomography (APT), and micromagnetic simulations to reveal the 3D architecture of the cloudy zone with subnanometer spatial resolution and model the mechanism of remanence acquisition during slow cooling on the meteorite parent body. Isolated islands of tetrataenite are embedded in a matrix of an ordered superstructure. The islands are arranged in clusters of three crystallographic variants, which control how magnetic information is encoded into the nanostructure. The cloudy zone acquires paleomagnetic remanence via a sequence of magnetic domain state transformations (vortex to two domain to single domain), driven by Fe–Ni ordering at 320 °C. Rather than remanence being recorded at different times at different positions throughout the cloudy zone, each subregion of the cloudy zone records a coherent snapshot of the magnetic field that was present at 320 °C. Only the coarse and intermediate regions of the cloudy zone are found to be suitable for paleomagnetic applications. The fine regions, on the other hand, have properties similar to those of rare-earth permanent magnets, providing potential routes to synthetic tetrataenite-based magnetic materials.

Ultra-small superparamagnetic iron oxide nanoparticles (SPIOs) were synthesized by co-precipitation of iron chloride salts with ammonia and then encapsulated with thin (~2nm) layers of silica. The particles have been characterized for size, diffraction pattern, surface charge, and magnetic properties. This rapid and economical synthesis has a number of industrial applications; however, the silica-coated particles have been optimized for use in medical applications as MR contrast agents, biosensors, DNA capturing, bioseparation and enzyme immobilization

A simple synthetic route to highly luminescent, water-soluble CdTe nanoparticles and their use in biological imaging is presented. The new synthetic pathway utilises a simply-prepared, watersoluble tellurium precursor which is easily handled and stored and the resulting growth processes are discussed.