Role of Crystal Structure and Chalcogenide Redox Properties on the Oxidative Assembly of Cadmium Chalcogenide Nanocrystals.
Role of Crystal Structure and Chalcogenide Redox Properties on the Oxidative Assembly of Cadmium Chalcogenide Nanocrystals.
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DOI：
10.1021/acs.langmuir.7b01118
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发表时间：
2017-09-19
期刊：
影响因子：
--
通讯作者：
Brock SL
中科院分区：
文献类型：
--
作者：
Davis JL;Chalifoux AM;Brock SL
金属硫属化物纳米晶体（NC）的氧化组装使得能够形成2-D（致密）和3-D多孔结构，而不存在可以调节传输性质的颗粒之间的介入配体。该路线已被证明是成功的一系列单组分结构，包括CdQ，PbQ，和ZnQ（Q = S，Se，Te）。在多组分纳米结构的可控组装过程中，使用时间分辨动态光散射（TR-DLS）评估了负责颗粒交联的Q氧化还原性质（2 Q2 − → Q22− +2 e）和单组分CdQ NC组装动力学中的天然结构（立方锌尖晶石与六方纤锌矿）的作用。对于纤锌矿CdQ，速率遵循氧化的容易程度，碲化物最快，其次是硒化物和硫化物。然而，当比较CdS纤锌矿（w）和锌纤锌矿（zb）时，立方NC表现出令人惊讶的慢动力学。NMR研究揭示了zb结构相对于w具有较低的配体覆盖率（4倍），并且游离二硫化物（配体氧化的产物）的形成缓慢。这归因于w和zb晶面的表面能的差异，与zb结构的中性晶面相比，w具有高能量的极性（0001）晶面。通过低温合成方法制备的zb-CdS NC可能遭受表面缺陷，这可能会缓和反应性。EPR研究表明，zb-CdS有顺磁性硫空位不存在于w-CdS。这些数据表明，结构中起着意想不到的大作用的动力学CdQ NC氧化组装，提供了一个有用的杠杆，以缓和活动的多组分组件。
Oxidative assembly of metal chalcogenide nanocrystals (NCs) enables the formation of 2-D (dense) and 3-D porous structures without the presence of intervening ligands between particles that can moderate transport properties. This route has been demonstrated to be successful for a range of single-component structures including CdQ, PbQ, and ZnQ (Q = S, Se, Te). En route to the controllable assembly of multicomponent nanostructures, the roles of Q redox properties (2Q2− → Q22− + 2e) responsible for particle cross-linking and the native structure (cubic zinc blende vs hexagonal wurtzite) in the kinetics of assembly in single-component CdQ NCs are evaluated using time-resolved dynamic light scattering (TR-DLS). For wurtzite CdQ, the rates follow the ease of oxidation, with telluride as the fastest, followed by selenide and sulfide. However, when comparing CdS wurtzite (w) and zinc blende (zb), the cubic NCs exhibit surprisingly slow kinetics. NMR studies reveal the zb structure to have lower ligand coverage (by a factor of 4) relative to that of w, and the formation of free disulfide (the product of ligand oxidation) is slow. This is attributed to differences in the surface energies of w and zb facets, with w having polar (0001) facets of high energy compared to the neutral facets of the zb structure. The zb-CdS NCs prepared by low-temperature synthesis methods are likely to suffer from surface defects that may moderate reactivity. EPR studies suggest that zb-CdS has paramagnetic sulfur vacancies not present in w-CdS. These data suggest that structure plays an unexpectedly large role in the kinetics of CdQ NC oxidative assembly, providing a useful lever to moderate activities in multicomponent assemblies.
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