Yusuke Hiejima

Phase behavior of Xe confined in porous vycor glass probed by 129Xe NMR chemical shift

129 Xe NMR spectroscopy is applied for direct observation of Xe confined in the porous Vycor glass. The chemical shifts of bulk and confined Xe are obtained simultaneously in a wide range of density from the gas phase to the liquid phase, including the supercritical region. The temperature and pressure dependences of the chemical shift of confined Xe are different from those of bulk Xe, which are approximately expressed by a linear function of bulk density. The phase transition of confined Xe is detected by the chemical shift, of which the pressure dependence along isotherms shows hysteresis loops.

Hydrothermal Synthesis of Photoluminescent Nanocarbon from Hydroxylic Acids and Amines

Carbon dots (CDs) were synthesized from various pairs of hydroxylic acids and amines under hydrothermal conditions. Citric acid (CA) was paired with ethylenediamine (EDA) and the methylated analogues, and malic acid (MA), tartaric acid (TA) and mucic acid (MuA) were coupled with EDA. While the CDs from CA with EDA show strong photoluminescence, CA paired with the methyl-capped EDA derivatives gives less photoluminescent nanocarbons with a similar size of ~2xa0nm. The CDs from MA and TA with EDA show emission at shorter wavelengths than those from CA and MuA. The quantum yields of the CDs from CA and MA with EDA increase with the reaction time, which may be explained by modifications of the chemical structures of the CDs.Graphical Abstract