Infrared phononic nanoantennas:Localized surface phonon polaritons in SiC disks

The electromagnetic interaction of light with polar materials shows a sharp and well defined electromagnetic response in the infrared(IR)region that consists mainly of excitation of optical phonons.Similar to surface plasmons in the visible region,surface phonons can couple efficiently to infrared light in micron-sized antennas made of polar materials.We applied the boundary element method to calculating the infrared electromagnetic response of single SiC disks acting as effective infrared antennas as a function of different parameters such as disk size and thickness.We also analyzed the effect of locating a probing metallic tip near the SiC disk to scatter light in the proximity of the SiC disk,thereby obtaining new spectral peaks connected with localized modes between the tip and the SiC disk.We then further investigated their application in IR scanning probe microscopy.A near-field map of the phononic resonances enhances the understanding of the nature of the IR extinction peaks.

Design of active and stable catalysts by embedding nitrogen-doped carbon oxygen reduction reaction CoxOy nanoparticles into

The oxygen reduction reaction （ORR） is essential in research pertaining to life science and energy. In applications, platinum-based catalysts give ideal reactivity, but, in practice, are often subject to high costs and poor stability. Some costefficient transition metal oxides have exhibited excellent ORR reactivity, but the stability and durability of such alternative catalyst materials pose serious challenges. Here, we present a facile method to fabricate uniform CoxOy nanoparticles and embed them into N-doped carbon, which results in a composite of extraordinary stability and durability, while maintaining its high reactivity. The half-wave potential shows a negative shift of only 21 mV after 10,000 cycles, only one third of that observed for Pt/C （63 mV）. Furthermore, after 100,000 s testing at a constant potential, the current decreases by only 17%, significantly less than for Pt/C （35%）. The exceptional stability and durability results from the system architecture, which comprises a thin carbon shell that prevents agglomeration of the CoxOy nanoparticles and their detaching from the substrate.

Boron nitride nanoresonators for phonon-enhanced molecular vibrational spectroscopy at the strong coupling limit

Enhanced light-matter interactions are the basis of surface-enhanced infrared absorption(SEIRA)spectroscopy,and conventionally rely on plasmonic materials and their capability to focus light to nanoscale spot sizes.Phonon polariton nanoresonators made of polar crystals could represent an interesting alternative,since they exhibit large quality factors,which go far beyond those of their plasmonic counterparts.The recent emergence of van der Waals crystals enables the fabrication of highquality nanophotonic resonators based on phonon polaritons,as reported for the prototypical infrared-phononic material hexagonal boron nitride(h-BN).In this work we use,for the first time,phonon-polariton-resonant h-BN ribbons for SEIRA spectroscopy of small amounts of organic molecules in Fourier transform infrared spectroscopy.Strikingly,the interaction between phonon polaritons and molecular vibrations reaches experimentally the onset of the strong coupling regime,while numerical simulations predict that vibrational strong coupling can be fully achieved.Phonon polariton nanoresonators thus could become a viable platform for sensing,local control of chemical reactivity and infrared quantum cavity optics experiments.

Heavy ion ranges from first-principles electron dynamics

The effects of incident energetic particles,and the modification of materials under irradiation,are governed by the mechanisms of energy losses of ions in matter.The complex processes affecting projectiles spanning many orders of magnitude in energy depend on both ion and electron interactions.Developing multi-scale modeling methods that correctly capture the relevant processes is crucial for predicting radiation effects in diverse conditions.In this work,we obtain channeling ion ranges for tungsten,a prototypical heavy ion,by explicitly simulating ion trajectories with a method that takes into account both the nuclear and the electronic stopping power.The electronic stopping power of self-ion irradiated tungsten is obtained from first-principles timedependent density functional theory(TDDFT).Although the TDDFT calculations predict a lower stopping power than SRIM by a factor of three,our result shows very good agreement in a direct comparison with ion range experiments.These results demonstrate the validity of the TDDFT method for determining electronic energy losses of heavy projectiles,and in turn its viability for the study of radiation damage.