Ultrathin Colloidal PbS/CdS Core/Shell Nanosheets
- PDF / 1,053,587 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 4 Downloads / 240 Views
Ultrathin Colloidal PbS/CdS Core/Shell Nanosheets Simeen Khan,1 Zhoufeng Jiang,1,2 Shashini M Premathilka, 1,2 Jianjun Hu,3 Andrey Voevodin,3 Paul J. Roland,4 Randy J. Ellingson,4 Liangfeng Sun1,2 1 Department of Physics and Astronomy, Bowling Green State University, Bowling Green, OH 43403,USA 2 Center of Photochemical Sciences, Bowling Green State University, Bowling Green, OH 43403,USA 3 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433, USA 4 Department of Physics and Astronomy, Wright Center for Photovoltaics Innovation and Commercialization, School of Solar and Advanced Renewable Energy, University of Toledo, Toledo, Ohio 43606, USA ABSTRACT Emissive PbS/CdS core/shell nanosheets are synthesized using a cation-exchange method. A significant blue-shift of the photoluminescence is observed, indicating a stronger quantum confinement in the PbS core as its thickness is reduced to eight atomic layers. High resolution transmission-electron-microscopy images of the cross-sections of the core/shell nanosheets show atomically sharp interfaces between PbS and CdS. Accurate analysis of the thickness of each layer reveals the relationship between the energy-gap and the thickness in the extremely one-dimensionally confined nanostructure. INTRODUCTION Quantum confinement is the origin of the novel properties of quantum dots. However, three-dimensional confinement also hinders the charge transfer among the quantum dots, which limits the performance of the quantum-dot-based electronic devices. In a two-dimensional (2D) structure, the charges within the 2D plane have high charge mobilities1, 2 while the onedimensional quantum confinement is retained in the thickness direction. Consequently, the tunable optical properties and the high charge mobility are unified in a single structure. Fabrication of these 2D materials using epitaxial methods is challenging due to the lack of lattice matching substrates.3, 4 A wet-chemistry synthesis of colloidal nanosheets1, 5-11 provides an alternative solution. The synthesized colloidal nanosheets are counterparts of the epitaxial quantum wells,12 but are free-standing and low-cost (since no high-vacuum or high-temperature is needed for the synthesis).13 We report a facile synthesis of emissive PbS/CdS core/shell nanosheets using cation-exchange methods. Significant blue-shift of the photoluminescence peak is observed, indicating stronger quantum confinement in the PbS core with reduced thickness. High resolution transmission electron microscopy (HRTEM) images of the cross-section of the nanosheets show clear crystal interfaces between PbS and CdS.
Downloaded from https:/www.cambridge.org/core. Cornell University Library, on 10 May 2017 at 08:02:06, subject to the Cambridge Core terms of use, available at https:/www.cambridge.org/core/terms. https://doi.org/10.1557/adv.2017.327
Figure 1. (a) Scheme showing the process of cation exchange for PbS/CdS structure. The overall dimension of the sheet remains the same while the out-la
Data Loading...
