Magnetic charge propagation upon a 3D artificial spin-ice

Magnetic charge propagation in spin-ice materials has yielded a paradigm-shift in science, allowing the symmetry between electricity and magnetism to be studied. Recent work is now suggesting the spin-ice surface may be important in mediating the ordering and associated phase space in such materials. Here, we detail a 3D artificial spin-ice, which captures the exact geometry of bulk systems, allowing magnetic charge dynamics to be directly visualized upon the surface. Using magnetic force microscopy, we observe vastly different magnetic charge dynamics along two principal directions. For a field applied along the surface termination, local energetics force magnetic charges to nucleate over a larger characteristic distance, reducing their magnetic Coulomb interaction and producing uncorrelated monopoles. In contrast, applying a field transverse to the surface termination yields highly correlated monopole-antimonopole pairs. Detailed simulations suggest it is the difference in effective chemical potential as well as the energy landscape experienced during dynamics that yields the striking differences in monopole transport.

A Bioinspired Strategy for Directional Charge Propagation in Photoelectrochemical Devices Using Supramolecular Machinery

Molecular photoelectrochemical (PEC) devices are hampered by electron–hole recombination after photoinduced electron transfer (PET), causing losses in power conversion efficiency (PCE). Inspired by natural photosynthesis, we demonstrate the use of molecular machinery as a strategy to inhibit recombination, through organization of molecular components and unbinding of the final electron acceptor after reduction. We show that preorganization of the macrocyclic 3-NDI-ring electron acceptor to the PSTATION dye forming the PSTATION:3-NDI-ring pseudorotaxane, enables a “ring launching” event, upon PET from PSTATION to 3-NDI-ring releasing 3-NDI-ring•−. Implementing PSTATION:3-NDI-ring into p-type dye-sensitized solar cells (p-DSSCs) revealed a fivefold increase in PCE compared to benchmark dye P1, unable to facilitate pseudorotaxane formation. This active repulsion of anionic 3-NDI-ring•− with concomitant reformation PSTATION:3-NDI-ring circumvents recombination at semiconductor–dye interface, affording a twofold enhancement in hole lifetime. We envision this concept of supramolecular-directed charge-propagation will encourage further integration of molecular machinery into PEC devices.

Charge Propagation along the Polymer Fiber of Polyhydroxybutyrate: Is it Possible to Apply the Cable Model?

This article considers experimental data on the surface charge propagation along the dielectric polymer fibers. Nonwoven polymer materials based on polyhydroxybutyrate obtained by electrospinning technique were used as an example of dielectric fibers in our experiments. Polymer fiber charging was investigated under the electron beam in a vacuum chamber of the scanning electron microscope. The fiber electric response registration was performed in a TV mode and in dynamic conditions using oscilloscopic sectioning visualization. Digitized images were processed using specialized software by Sobel-Feldman operator (Sobel filter), visualizing isopotential lines of the electron beam-induced emission. The results obtained were analyzed in the framework of the Roll’s cable model, which has been extrapolated from the electrical signal transduction along the nerve fibers to the charge propagation along the dielectric polymer fibers.

Plasmon-driven ultrafast point-projection electron microscopy

We implement a plasmon-driven ultrafast electron source in a point-projection electron microscope. A proof-of-principle experiment investigating the charge propagation in a single nanoresonator demonstrates an unprecedented spatiotemporal resolution of 20 nm and 25 fs.