Theoretical Studies on the Water-Assisted Hydrolysis of N,N-Dimethyl-N′-(2′,3′-dideoxy-3′-thiacytidine) Formamidine with Three Water Molecules

Stepwise mechanism and H2O-assisted hydrolysis in atomic layer deposition of SiO2 without a catalyst

Atomic layer deposition (ALD) is a powerful deposition technique for constructing uniform, conformal, and ultrathin films in microelectronics, photovoltaics, catalysis, energy storage, and conversion. The possible pathways for silicon dioxide (SiO2) ALD using silicon tetrachloride (SiCl4) and water (H2O) without a catalyst have been investigated by means of density functional theory calculations. The results show that the SiCl4 half-reaction is a rate-determining step of SiO2 ALD. It may proceed through a stepwise pathway, first forming a Si-O bond and then breaking Si-Cl/O-H bonds and forming a H-Cl bond. The H2O half-reaction may undergo hydrolysis and condensation processes, which are similar to conventional SiO2 chemical vapor deposition (CVD). In the H2O half-reaction, there are massive H2O molecules adsorbed on the surface, which can result in H2O-assisted hydrolysis of the Cl-terminated surface and accelerate the H2O half-reaction. These findings may be used to improve methods for the preparation of SiO2 ALD and H2O-based ALD of other oxides, such as Al2O3, TiO2, ZrO2, and HfO2.

Ligand-exchange mechanism: new insight into solid-phase extraction of uranium based on a combined experimental and theoretical study

The extraction mechanism is an exchange process between the ligands on Urea-GO and the coordinated water molecules of uranyl.