Using neutron diffraction, we have tracked the temperature dependence of structural properties for heavy water confined in the nanoporous silica matrix MCM-41-S. By observing the correlation peak corresponding to the pore-pore distance, which is determined by the scattering contrast between the silica and the water, we monitored the density of the confined water. Concurrently, we studied the prominent first diffraction peak of D(2)O at ≈ 1.8 Å(-1), which furnishes information on the microscopic arrangement of the water molecules. The data show the presence of a density maximum at ≈ 275 K (± 10 K), a property similar to bulk water, and the occurrence of a density minimum at ≈ 180 K (± 10 K). The prominent diffraction peak of D(2)O is found to shift and sharpen over a wide T range from 200 to 270 K, reflecting structural changes that are strongly correlated with the changes in density. We also observe the continuous formation of external ice, arising from water expelled from the pores while expansion takes place within the pores. An efficient method for monitoring the density of the confined D(2)O using a triple-axis spectrometer is demonstrated.
In microwave (MW) thermotherapy, it is challenging to regulate the temporal and spatial distribution of the temperature at the nanoscale. Herein, we report a nanothermometer for simultaneous MW heating and temperature distribution measurement. The nanothermometer was prepared by free radical polymerization with vinylbenzyl trimethylammonium chloride (VBTMACl) as the MW thermosensitizer and isopropylacrylamide (NIPAM) as the thermoresponsive unit, followed by anion exchange with fluorophore sodium 3-(4-(1,2,2-triphenylvinyl)phenoxy)propane-1-sulfonate (TPESONa).
Rate coefficients for the reaction of CH with CHO were measured for the first time over the temperature range of 37-603 K, with the CH radicals produced by pulsed laser photolysis and detected by CH radical chemiluminescence following their reaction with O. The low temperature measurements (≤93 K) relevant to the interstellar medium were made within a Laval nozzle gas expansion, while higher temperature measurements (≥308 K) were made within a temperature controlled reaction cell. The rate coefficients display a negative temperature dependence below 300 K, reaching (1.
Intrinsically disordered proteins (IDPs) show structural changes stimulated by changes in external conditions. This study aims to reveal the temperature dependence of the structure and dynamics of the intrinsically disordered region of Hef, one of the typical IDPs, using an integrative approach. Small-angle X-ray scattering (SAXS) and circular dichroism (CD) studies revealed that the radius of gyration and ellipticity at 222 nm remained constant up to 313-323 K, followed by a decline above this temperature range.
