Effect of molecular weight of PMMA on the conductivity and viscosity behavior of polymer gel electrolytes containing NH<Subscript>4</Subscript>CF<Subscript>3</Subscript>SO<Subscript>3</Subscript>

The addition of polymethyl methacrylate (PMMA) having different molecular weights to electrolytes containing ammonium trifluoromethanesulfonate (NH₄CF₃SO₃) in diethyl carbonate (DEC) has been found to result in conductivity enhancement and to yield gel electrolytes with conductivity higher than the corresponding liquid electrolytes. The increase in conductivity has been found to be due to the dissociation of undissociated NH₄CF₃SO₃ and ion aggregates present in the electrolytes, and this has been supported by Fourier transform infrared spectroscopy results, which suggests active interaction of PMMA and NH₄CF₃SO₃ in these gel electrolytes. The increase in conductivity also depends upon the molecular weight of the polymer used and is relatively more for PMMA having lower molecular weight. The increase in viscosity with PMMA addition also depends upon the molecular weight of the polymer and is closely related to the conductivity behavior of these electrolytes. Polymer gel electrolytes have been found to be thermally stable up to a temperature of 125 °C.     

Direct observation of optically induced transient structures in graphite using ultrafast electron crystallography

We use ultrafast electron crystallography to study structural changes induced in graphite by a femtosecond laser pulse. At moderate fluences of < or =21 mJ/cm2, lattice vibrations are observed to thermalize on a time scale of approximately 8 ps. At higher fluences approaching the damage threshold, lattice vibration amplitudes saturate. Following a marked initial contraction, graphite is driven nonthermally into a transient state with sp3-like character, forming interlayer bonds. Using ab initio density functional calculations, we trace the governing mechanism back to electronic structure changes following the photoexcitation.     

Computational and experimental investigations on the effect of crystallinity and crystal size on Na-transport in nanoscaled Si: implications for Si-based anodes for Na-ion batteries

Journal of Solid State Electrochemistry - While Li transport in Si is well understood, little is known about Na transport, despite Si being considered a potential anode material for the upcoming...     

Magnetic Purcell Enhancement in a Nanoantenna-Spherical Bragg Resonator Coupled System

In this work, a novel approach for enhancing magnetic fields in all-dielectric nanoantennas using Spherical Bragg Resonators (SBR) is proposed, which can boost quantum emitters' magnetic transitions. A matrix method has been used to optimize the magnetic dipole resonance of a SiO₂/Si core-shell spherical nanoantenna. The radiative and non-radiative decay rate of a Eu³⁺ emitter with a quantum efficiency of ∼80% is studied. The findings revealed that the magnetic dipole nanoantenna resonance coupling with the SBR mode significantly enhances the modal magnetic field. A 4-layer SiO₂/Si SBR results in a Purcell factor of $\approx 5\times {10}^3$, the highest it has found in the literature, to the best of the knowledge. The work offers a theoretical demonstration of the potential of SBR to improve the performance of dielectric nanoantennas.