Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354, USA.
Phys Chem Chem Phys. 2019 Feb 27;21(9):4717-4720. doi: 10.1039/c8cp07521b.
NMR methods were utilized to monitor the in situ structural and dynamic changes of various species in highly alkaline tetramethylammonium (TMA) silicate solutions. Quantitative 29Si NMR, 1H, 2H, and 17O relaxation NMR, and 1H and 29Si diffusion NMR of silicates, TMA, H2O and D2O demonstrate that the growth of the cubic octamer Q38 is accompanied by reduced water mobility and increasing TMA coordination number per Q38, which reaches an equilibrium value of 4.5 at 15 °C. Temperature-dependent measurements further reveal that the increased control over speciation by TMA at lower temperatures results from the more stable ion associations via slower solvent motions.
NMR 方法被用于监测在高碱性四甲基铵（TMA）硅酸盐溶液中各种物种的原位结构和动态变化。定量 29Si NMR、1H、2H 和 17O 弛豫 NMR 以及硅酸盐、TMA、H2O 和 D2O 的 1H 和 29Si 扩散 NMR 表明，立方八聚体 Q38 的生长伴随着水流动性的降低和每个 Q38 的 TMA 配位数的增加，在 15°C 时达到 4.5 的平衡值。温度依赖性测量进一步表明，在较低温度下 TMA 对形态控制的增加是由于通过较慢的溶剂运动形成更稳定的离子缔合物。
