中央研究院 原子與分子科學研究所

Nonnoble metal catalysts are low-cost alternatives to Pt for the oxygen reduction reactions (ORRs), which have been studied for various applications in electrocatalytic systems. Among them, transition metal complexes, characterized by a redox-active single-metal-atom with biomimetic ligands, such as pyrolyzed cobalt–nitrogen–carbon (Co–N x /C), have attracted considerable attention. Therefore, we reported the ORR mechanism of pyrolyzed Vitamin B12 using operando X-ray absorption spectroscopy coupled with electrochemical impedance spectroscopy, which enables operando monitoring of the oxygen binding site on the metal center. material design strategies for high-performance electrocatalysts for fuel cell applications. Furthermore, the charge transfer mechanism between the catalyst and reactant enables further Co–O species formation. These experimental findings, provide insight into metal active-site geometry and structural evolution during ORR, which could be used for developing material design strategies for high performance electrocatalysts for fuel cell applications.

Availability of relativistically intense, single-cycle, tunable infrared sources will open up newareas of relativistic nonlinear optics of plasmas, impulse IR spectroscopy and pump-probeexperiments in the molecular fingerprint region. However, generation of such pulses is still achallenge by current methods. Recently, it has been proposed that time dependent refractiveindex associated with laser-produced nonlinear wakes in a suitably designed plasma densitystructure rapidly frequency down-converts photons. The longest wavelength photons slipbackwards relative to the evolving laser pulse to form a single-cycle pulse within the nearlyevacuated wake cavity. This process is called photon deceleration. Here, we demonstrate thisscheme for generating high-power (~100 GW), near single-cycle, wavelength tunable(3–20 μm), infrared pulses using an 810 nm drive laser by tuning the density profile of theplasma. We also demonstrate that these pulses can be used to in-situ probe the transient andnonlinear wakes themselves.

Fluorescent nanodiamond (FND) containing nitrogen-vacancy (NV) centers as built-in fluorophores exhibits a nearly constant emission profile over 550 – 750 nm upon excitation by vacuum-ultraviolet (VUV), extreme ultraviolet (EUV), and X- radiations from a synchrotron source over the energy (wavelength) range of 6.2 – 1450 eV (0.86 – 200 nm).  The photoluminescence (PL) quantum yield of FND increases steadily with the increasing excitation energy, attaining a value as great as 1700% at 700 eV (1.77 nm).  Notably, the yield curve is continuous, having no gap in the VUV to X-ray region.  In addition, no significant PL intensity decreases were observed for hours.  Applying the FND sensor to measure the absorption cross sections of gaseous O₂ over 110 – 200 nm and comparing the measurements with the sodium-salicylate scintillator, we obtained results in agreement with each other within 5%.  The superb photostability and broad applicability of FND offer a promising solution for the long-standing problem of lacking a robust and reliable detector for VUV, EUV, and X- radiations.