Molecular
dynamics simulation was used to examine the growth of
methane hydrate in the presence of natural product pectin at different
concentrations, including the mass fractions 2.46% and 3.62%. Snapshots
of the system configurations with time, radial distribution functions
of the carbon atoms, and the total energy of the system were employed
to characterize the effect of pectin on methane hydrate growth. Results
indicated that pectin is a good inhibitor of methane hydrate. The
higher the concentration of pectin is, the better the effect of inhibition
is. The double-bonded oxygen atoms of pectin combine with hydrogen
atoms of water, and the hydrogen atoms of hydroxyl in pectin combine
with oxygen atoms of water through hydrogen bonds, which disturbed
the further growth of the methane hydrate. The role of the pectin’s
active groups in hydrogen bonds with water both as proton donor and
as electron acceptor makes pectin have a better inhibitory effect
on the growth of methane hydrate.
The coupling effect between nitrogen-vacancies (VN) and aluminum-interstitial sites (Ali) is investigated theoretically and experimentally in AlN helices. First-principles calculations predict a photoluminescence emission peak at approximately 600 nm in AlN doped with complex-defect (VNAli). A typical long afterglow (persistent luminescence) was observed in unintentionally doped AlN helices by introducing the complex-defect of (VNAli). An analysis of the luminescent characteristics indicated that the mechanism behind this afterglow is the complex-defect level and complex-defect density. These findings may further enrich the thoughts of defects in the wide band gap semiconductor of AlN.
A photo-responsive macroscopic switch was fabricated using a chiral azo-calix[4]arene derivative (FC4AD) functionalized silicon surface and exhibited selective and reversible recognition of (1R,2S)-1-amino-2-indanol through the variation of wettability. This photo-responsive device may have wide applications in controlled release of chiral drugs and in biosensors.
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