Metal-free organic phosphorescent materials are attractive alternatives to the predominantly used organometallic phosphors but are generally dimmer and are relatively rare, as, without heavy-metal atoms, spin–orbit coupling is less efficient and phosphorescence usually cannot compete with radiationless relaxation processes. Here we present a general design rule and a method to effectively reduce radiationless transitions and hence greatly enhance phosphorescence efficiency of metal-free organic materials in a variety of amorphous polymer matrices, based on the restriction of molecular motions in the proximity of embedded phosphors. Covalent cross-linking between phosphors and polymer matrices via Diels–Alder click chemistry is devised as a method. A sharp increase in phosphorescence quantum efficiency is observed in a variety of polymer matrices with this method, which is ca. two to five times higher than that of phosphor-doped polymer systems having no such covalent linkage.

Optical methods for modulating cellular behavior are promising for both fundamental and clinical applications. However, most available methods are either mechanically invasive, require genetic manipulation of target cells, or cannot provide sub-cellular specificity. Here, we address all these issues by showing optical neuromodulation with free-standing coaxial p-type/intrinsic/n-type silicon nanowires. We revealed the presence of atomic gold on the nanowire surfaces, likely due to gold diffusion during the material growth. To evaluate how surface gold impacts the photoelectrochemical properties of single nanowires, we used modified quartz pipettes from a patch clamp and recorded sustained cathodic photocurrents from single nanowires. We show that these currents can elicit action potentials in primary rat dorsal root ganglion neurons through a primarily atomic gold-enhanced photoelectrochemical process.

The formation and relaxation of shish in molten isotactic polypropylene (iPP) and two samples containing different commercial nucleating particles was studied during and after continuous shear flow. In-situ measurements of the shish were made by simultaneous wide- and small-angle X-ray scattering (rheo-SAXS/WAXS) using synchrotron radiation. In the SAXS patterns, sharp meridional reflections were observed in all three samples during the initial stages of shear flow. Their presence indicates that shish form in discrete steps, by the aggregation of pointlike nuclei into oriented threads. Compared to pure iPP, the addition of both nucleants increased the amount and the dimensions of shish formed. However, the shish also relaxed faster in the presence of both nucleated materials. This behavior was attributed to the particles inducing lower molecular weight chains to participate in shish formation. The particle aspect ratio was observed to greatly influence shish formation. This is explained by modification of the local strain environment near the surface of the different shaped particles.

The morphological development of sheared isotactic polypropylene (iPP) containing different amounts of sodium benzoate (SB) has been investigated using wide-and small-angle X-ray scattering techniques. The microbeam of synchrotron radiation allows us to gain, precisely and efficiently, the local morphology at a given position with a good spatial resolution. The morphological distributions such as crystallinity, fractions of R-form and β-form crystals, crystal size, and orientation functions can therefore be well constructed through the shear field or temperature gradient. The distribution of crystallinity is changed from a U-shape without SB to an almost flat with SB, in company with a minimum fraction of R-form crystal and a maximum fraction of β-form crystal. The epitaxial growth of branched lamellae in the presence of SB is confirmed from the orientation functions of two axes using wide-angle diffraction. The effect of SB on the molecular orientation is understood from the orientation function of c-axis and the azimuthal patterns of small-angle scattering. It is found that both the molecular orientation and the lamellar orientation of the R-form crystal are increased with increasing SB. The thickness of crystalline lamellae with respect to flow direction is found to increase with increasing SB in the whole range from shear zone to core center. A slight declination of crystalline lamellae has been observed in the presence of SB.