Butterfield Auston G, Alameda Lucas T, Schaak Raymond E
J Am Chem Soc. 2021 Feb 3;143(4):1779-1783. doi: 10.1021/jacs.0c13072. Epub 2021 Jan 25.
Cation exchange reactions modify the composition of a nanocrystal while retaining other features, including the crystal structure and morphology. In many cases, the anion sublattice is considered to be locked in place as cations rapidly shuttle in and out. Here we provide evidence that the anion sublattice can shift significantly during nanocrystal cation exchange reactions. When the Cu cations of roxbyite CuS nanorods exchange with Zn to form ZnS nanorods, a high density of stacking faults emerges. During cation exchange, the stacking sequence of the close-packed anion sublattice shifts at many locations to generate a nanorod product containing a mixture of wurtzite, zincblende, and a wurtzite/zincblende polytype that contains an ordered arrangement of stacking faults. The reagent concentration and reaction temperature, which control the cation exchange rate, serve as synthetic levers that can tune the stacking fault density from high to low, which is important because once introduced, the stacking faults could not be modified through thermal annealing. This level of synthetic control through nanocrystal cation exchange is important for controlling properties that depend on the presence and density of stacking faults.
阳离子交换反应在保留包括晶体结构和形态等其他特征的同时，会改变纳米晶体的组成。在许多情况下，随着阳离子快速地穿梭进出，阴离子亚晶格被认为是固定不动的。在此我们提供证据表明，在纳米晶体阳离子交换反应过程中，阴离子亚晶格会发生显著位移。当硫铜锌矿CuS纳米棒中的铜阳离子与锌发生交换以形成ZnS纳米棒时，会出现高密度的堆垛层错。在阳离子交换过程中，密堆积阴离子亚晶格的堆积顺序在许多位置发生位移，从而生成一种纳米棒产物，该产物包含纤锌矿、闪锌矿以及一种含有有序堆垛层错排列的纤锌矿/闪锌矿多型体的混合物。控制阳离子交换速率的试剂浓度和反应温度，充当着可将堆垛层错密度从高调整到低的合成杠杆，这一点很重要，因为一旦引入堆垛层错，就无法通过热退火对其进行修改。通过纳米晶体阳离子交换实现的这种合成控制水平，对于控制依赖于堆垛层错的存在和密度的性质而言至关重要。
