Exciton Energy Shifts and Tunable Dopant Emission in Manganese-Doped Two-Dimensional CdS/ZnS Core/Shell Nanoplatelets
Exciton Energy Shifts and Tunable Dopant Emission in Manganese-Doped Two-Dimensional CdS/ZnS Core/Shell Nanoplatelets
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DOI：
10.1021/acs.chemmater.9b00006
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发表时间：
2019-04-09
影响因子：
8.6
通讯作者：
Zheng, Weiwei
中科院分区：
文献类型：
--
作者：
Davis, Andrew H.;Hofman, Elan;Zheng, Weiwei
将过渡金属离子掺杂到半导体纳米晶体（NC）中的能力允许在原始本征材料中引入和利用新的非本征性质。虽然掺杂的零维量子点和一维纳米棒/纳米线的合成已被广泛报道，但过渡金属离子掺杂的二维（2D）纳米碳的研究较少。在这项研究中，我们开发了一锅法合成Mn 2+掺杂的2D CdS（即，Mn：CdS）纳米片（NPL）。通过电子顺磁共振和X射线衍射测量证实了CdS NPL晶格内成功的Mn掺杂。令人惊讶的是，在Mn：CdS NPL中仅观察到CdS光致发光（PL），而不考虑Mn掺杂浓度。为了解决热稳定性差的问题并改善2D Mn：CdS NPL的光学性质，我们使用单源脱壳前体方法合成了ZnS壳钝化的Mn：CdS/ZnS核/壳NPL，其允许在相对低的温度下对NPL进行ZnS表面钝化，同时具有热适应性以确保最小的NPL降解。一个非常大的激子红移（类似于420毫电子伏），在ZnS壳钝化，观察到由于CdS核心NPL的有效厚度增加。稳态和时间分辨的发射测量表明，主机掺杂剂的能量转移效率和Mn Mn的相互作用内的2D Mn：CdS/ZnS核/壳NPL可以通过掺杂剂浓度微调，导致在强烈的Mn PL以及可调的双带发射从主机NPL和Mn掺杂剂。磁性测量表明，在2D NPL和复杂的磁相互作用在高掺杂浓度，包括反铁磁交换掺杂剂和可能的掺杂剂表面状态的相互作用的内在自旋状态。
The ability to dope transition-metal ions into semiconductor nanocrystals (NCs) allows for the introduction and exploitation of new extrinsic properties in the original intrinsic material. Although the synthesis of doped zero-dimensional quantum dots and one-dimensional nanorods/nanowires has been widely reported, transition-metal ion-doped two-dimensional (2D) NCs have been less explored. In this study, we developed a one-pot synthesis of Mn2+-doped 2D CdS (i.e., Mn:CdS) nanoplatelets (NPLs). Successful Mn doping inside the CdS NPL lattice was confirmed by electron paramagnetic resonance and X-ray diffraction measurements. Surprisingly, only CdS photoluminescence (PL), without contribution from Mn PL, was observed in the Mn:CdS NPLs, regardless of Mn doping concentration. To address the issue of poor thermal stability and improve the optical properties of the 2D Mn:CdS NPLs, we synthesized ZnS shell-passivated Mn:CdS/ZnS core/shell NPLs using a single-source shelling precursor method, which allows for ZnS surface passivation of NPLs at relatively low temperatures, while being thermally adaptable to ensure minimal NPL degradation. An extremely large exciton red shift (similar to 420 meV), upon ZnS shell passivation, was observed because of the increased effective thickness of the CdS core NPLs. Steady-state and time-resolved emission measurements indicate that the host dopant energy-transfer efficiency and Mn Mn interactions within the 2D Mn:CdS/ZnS core/shell NPLs can be fine-tuned via the dopant concentration, resulting in an intense Mn PL as well as tunable dual-band emission from the host NPLs and Mn dopants. Magnetic measurements indicate intrinsic spin states in the 2D NPLs and complex magnetic interactions at high doping concentrations, including antiferromagnetic exchange between dopants and possible dopant surface state interaction.