Seung Han Ryu

Highly conductive polymer composites incorporated with electrochemically exfoliated graphene fillers

Highly conductive polymer composites were fabricated with a novel type of graphene-based filler, electrochemically exfoliated graphene sheets (EGs) produced without conventional oxidation/reduction of graphene oxide (GO). The high electrical conductivity of 417 ± 83 S m−1 at a content loading of 5.8 vol% and a low percolation threshold of 0.37 vol% could be attainable. Microscopic and spectroscopic investigations demonstrated the effective dispersion of EG-fillers on the surface of polymer particles and visualized the actual conducting channel between the polymer matrices.

Near-infrared absorbance properties of Cu2−xS/SiO2 nanoparticles and their PDMS-based composites

We synthesized different Cu2−xS nanoparticles (CuS and Cu1.8S NPs) with localized surface plasmon resonance (LSPR) absorbance in the near infrared (NIR) region and applied a silica layer on the surface of Cu2−xS nanoparticles (NPs) to achieve high photo-stability and dispersion stability. These plasmonic Cu2−xS NPs have been much utilized as thermal shielding materials of energy-saving windows, due to shielding the ultraviolet (UV) and NIR regions, and transmitting the visible (Vis) region. However, this application is limited because Cu2−xS NPs show photocatalyst properties that lead to the decomposition of organic matter, and dispersing these NPs into polymer films is difficult. Herein, silica coating successfully suppressed the generation of hydroxyl radicals on the surface of CuS NPs, which caused the photo-degradation of a polydimethylsiloxane (PDMS) polymer. Furthermore, a silica layer with the structure similar to that of PDMS provided the dispersion stability of CuS NPs. The achievement of good photo-stability and dispersion stability in the Cu2−xS NPs was demonstrated by the thermal shielding effect using a simulated experiment. The temperature change of a box shielded with a CuS/SiO2–PDMS film (ΔT = 6.8 °C) was smaller than that when the box was shielded with common glass (ΔT = 12.7 °C) or a CuS–PDMS film (ΔT = 9.2 °C). This research introduces a new and reliable thermal shielding material.