Synthesis of Multi-Shell Nanoplates by Consecutive Epitaxial. Properties

Transcription

1 Supporting information Synthesis of Multi-Shell Nanoplates by Consecutive Epitaxial Growth of Bi 2 Se 3 and Bi 2 Te 3 Nanoplates and Enhanced Thermoelectric Properties Yuho Min, 1 Gyeongbae Park, 2 Bongsoo Kim, 1 Anupam Giri, 2 Jie Zeng, 3 Jong Wook Roh, 4 Sang Il Kim, 4 Kyu Hyoung Lee, 5 * and Unyong Jeong 2 * 1 Department of Materials Science and Engineering, Yonsei University, 134 Shinchon-dong, Seoul, Korea 2 Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), 77 Cheongam-Ro, Nam-Gu, Pohang , Korea 3 Hefei National Laboratory for Physical Sciences at the Microscale & Collaborative Innovation Center of Suzhou Nano Science and Technology, University of Science and Technology of China, Hefei, Anhui , P. R. China 4 Materials Research Center, Samsung Advanced Institute of Technology, Samsung Electronics, Suwon , Korea 5 Department of Nano Applied Engineering, Kangwon National University, Chuncheon , Korea *Corresponding author. ujeong@postech.ac.kr, khlee2014@kangwon.ac.kr S1

2 Figure S1. (A) High resolution transmission electron microscopy (HRTEM) image showing an edge area of a Bi 2 Se 3 nanoplate with a corresponding Fast Fourier Transform (FFT) pattern as an inset. (B) X-ray diffractograms of Bi 2 Se 3 seed nanoplates with vertical red lines showing the JCPDS data for rhombohedral Bi 2 Se 3 ( ). S2

3 Figure S2. Scalable synthesis of Bi 2 Se 2 Te 3 (BS@BT) core/shell nanoplates. (A) Digital photographs of the as-synthesized Bi 2 Se 2 Te 3 ([BS]:[BT] =1:4) nanoplate suspension and (B) the mass of the powders obtained from the same suspension after three cycles of centrifugation and washing with de-ionized water, ethanol, and acetone. S3

4 Figure S3. Transmission electron micrograph of the products obtained by using a precursor ratio ([BS]:[BT]) of 1:4 at 120 C. Both 1D and 2D morphologies are obtained. S4

5 Figure S4. (A) Scanning TEM image of Bi 2 Se 2 Te 3 (BS@BT) nanoplates and (B) EDS map of corresponding BS@BT nanoplates. (C-E) Individual maps of each element: (C) Bi (blue); (C) Se (red); (D) Te (green). S5

6 Figure S5. (A) Transmission electron micrograph, (B) high-angle annular dark field scanning transmission electron micrograph, and (C) the corresponding energy dispersive X-ray spectroscopy (EDS) map of Bi 2 Se 2 Te 3 (BS@BT) core/shell nanoplates synthesized at a molar ratio ([BS]:[BT]=1:9). (D) Elemental profile obtained by EDS along the arrow shown in panel (B). The scale bar in panel (B) is 200 nm. S6

7 Figure S6. (A C) Transmission electron micrographs of Bi 2 Se 2 Te 3 (BS@BT) core/shell nanoplates obtained after 24 h reaction at (A) 160 C, (B) 180 C, and (C) 200 C. The scale bar in all the images represents 100 nm. S7

8 Figure S7. (A) Width and thickness of the nanoplates as a function of the number of seed-growth steps, as measured by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The values shown for the width and thickness for each sample are averages over 100 and 20 different nanoplates, respectively. (B, C) AFM analysis of Bi 2 Se 2 Te 2 Se 3 (BS@BT@BS) double-shell nanoplates synthesized at different molar ratios of BS and BT: (B) [BS]: [BT]: [BS]=1: 4: 32, (C) [BS]: [BT]: [BS]=1: 4: 16. S8

9 Figure S8. (A) Transmission electron micrograph, (B) high-angle annular dark field scanning transmission electron micrograph, and (C) the corresponding energy dispersive X-ray spectroscopy (EDS) map of Bi 2 Se 2 Te Bi 2 Se 3 (BS@BT@BS) double-shell nanoplates synthesized at a molar ratio ([BS]: [BT]: [BS]) of 1:4:16. (D) Elemental profile obtained by EDS along the arrow shown in panel (B). The scale bar in panel (B) represents 200 nm. S9

10 Figure S9. Atomic force microscopy analysis of Bi 2 Se 2 Te 2 Se 2 Te 3 ([BS]:[BT]:[BS]: [BT] =1:4:32:48) multi-shell nanoplates. S10

11 Figure S10. X-ray dffractogram of sintered pellets prepared by using differerent nanoplates; BS (Bi 2 Se 3 ), BT8BS2 (BS@BT, [BS]:[BT]=1:4), and BT9BS1 (BS@BT, [BS]:[BT]=1:9). The vertical solid lines indicate the standard JCPDS data for rhombohedral Bi 2 Te 3 ( , red) and Bi 2 Se 3 ( , black). S11

12 Figure S11. (A) Cross-section transmission electron micrograph (TEM) of the sintered BS1BT9 nanoplates. S12