Si(111) surface modified with alpha,beta-unsaturated carboxyl groups studied by MIR-FTIR

Gel Polymer Electrolytes for Lithium-Ion Batteries Enabled by Photo Crosslinked Polymer Network

We demonstrate a gel polymer electrolyte (GPE) featuring a crosslinked polymer matrix formed by poly(ethylene glycol) diacrylate (PEGDA) and dipentaerythritol hexaacrylate (DPHA) using the radical photo initiator via ultraviolet (UV) photopolymerization for lithium-ion batteries. The two monomers with acrylate functional groups undergo chemical crosslinking, resulting in a three-dimensional structure capable of absorbing liquid electrolytes to form a gel. The GPE system was strategically designed by varying the ratios between the main polymer backbone (PEGDA) and the crosslinker (DPHA) to achieve an optimal gel polymer electrolyte network. The resulting GPE exhibited enhanced thermal stability compared to conventional liquid electrolytes (LE) and demonstrated high ionic conductivity (1.40 mS/cm) with a high lithium transference number of 0.65. Moreover, the obtained GPE displayed exceptional cycle performance, maintaining a higher capacity retention (85.2%) comparable to the cell with LE (79.3%) after 200 cycles.

Structure of alkyne monolayers on hydrogen-terminated Si(100) surfaces investigated by external reflection infrared spectroscopy

Monolayers of terminal alkynes with long hydrocarbon chains C(n)H(2n+1)C≡CH (n = 10, 13, 16) were prepared on Si(100) substrates via thermally induced hydrosilylation and the surface orientation of the hydrocarbon chains was investigated by external reflection infrared spectroscopy. It was found that under rigorous exclusion of oxygen in the monolayer preparation process, all three compounds yield highly characteristic IR reflection spectra, consisting of upward-pointing ν(CH(2)) absorptions and downward-pointing ν(CH(3)) absorptions, indicative of a highly ordered anisotropic film structure. Via spectral simulations it was found that the methylene backbones (CH(2))(n) in these films adopt a uniform, all-trans conformation with a tilt angle of about 30° toward the surface normal, whereas the chain termini are disordered and give an isotropic film surface composed of randomly oriented CH(3) groups. Lower quality films, which are hardly distinguishable from highly ordered films by other methods, but have been shown to exhibit inferior electrical properties, are clearly identified in their infrared (IR) spectra as partly disordered structures. External reflection IR therefore proves to be an exceptionally sensitive tool to detect structural defects in these monolayers.

Electrodeposition of platinum and silver into chemically-modified microporous silicon electrodes

Electrodeposition of platinum and silver into hydrophobic and hydrophilic microporous silicon layers was investigated using chemically-modified microporous silicon electrodes. Hydrophobic microporous silicon enhanced the electrodeposition of platinum in the porous layer. Meanwhile hydrophilic one showed that platinum was hardly deposited within the porous layer and a filmy growth of platinum on the top of the porous layer was observed. On the other hand, the electrodeposition of silver showed similar deposition behavior between these two chemically-modified electrodes. It was also found that the electrodeposition of silver started at the pore opening and grew toward the pore bottom, while a uniform deposition from the pore bottom was observed in platinum electrodeposition. These electrodeposition behaviors are explained on the basis of the both effect, the difference in overpotential for metal deposition on silicon and on the deposited metal, and displacement deposition rate of metal.

Surface modification of silicon nanowires via copper-free click chemistry

A two-step process based on copper-free click chemistry is described, by which the surface of silicon nanowires can be functionalized with specific organic substituents. A hydrogen-terminated nanowire surface is first primed with a monolayer of an α,ω-diyne and thereby turned into an alkyne-terminated, clickable platform, which is subsequently coupled with an overlayer of an organic azide carrying the desired terminal functionality. The reactive, electron-deficient character of the employed diyne enabled a quantitative coupling reaction at 50 °C without metal catalysis, which opens up a simple and versatile route for surface functionalization under mild conditions without any potentially harmful additives.