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本文以三个不同粒径(1#:2.3 nm, 2#:2.8 nm和3#:3.5 nm)的巯基乙酸包覆的CdTe量子点(thioglycolic acid capped CdTe quantum dots, TGA-CdTe QDs)样品为研究对象, 其时间相关单光子计数(time-correlated single photon counting, TCSPC)实验得到的时间分辨光谱显示, 三个量子点的荧光平均寿命依次是～6 ns, ～10 ns和～12 ns, 其动力学过程包括慢过程和快过程两部分. 随其粒径尺寸的增加, 其慢过程延长, 快过程在变短. 然后, 通过瞬态吸收和荧光上转换两种基于飞秒的时间分辨光谱技术, 对TGA-CdTe量子点的带间弛豫过程做了探究. 实验结果显示, 三个TGA-CdTe量子点样品, 随其粒径增大, 最高激发态和最低激发态填充速率减慢, 其中, 最高激发态从0.33 ps增加至0.79 ps; 最低激发态从0.53 ps增至～1 ps. 另外, 由瞬态吸收和荧光上转换两种时间分辨手段相结合, 可得到CdTe量子点带间弛豫的完整图像, 结果显示了TGA-CdTe 量子点的一个本征特征:即在基态漂白恢复过程中的初始上升阶段, 荧光上转换信号要慢于瞬态吸收信号. 这可以为量子点在光电转换应用上提供帮助.
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关键词:
- TGA-CdTe量子点 /
- 飞秒时间分辨光谱 /
- 激子动力学
In the present paper, we study the average fluorescence lifetimes, detected by using the time-correlated single-photon-counting (TCSPC) technique, of three thioglycolic acid-capped CdTe quantum dots (TGA-CdTe QDs), which are ～6 ns, ～9 ns and ～11 ns; and the fluorescence kinetic process includes two parts:the slow process and the fast process. With the increase of the particle size, the slow process becomes longer, but the fast process becomes shorter. Afterwards, by using both femtosecond transient absorption and fluorescence up-conversion time-resolved spectrum techniques, we have investigated the interband relaxation process of three TGA-CdTe QD samples, with the nanoparticle diameters of 2.3, 2.8 and 3.5 nm. Investigation indicates that for the three QD samples, exciton filling rate becomes slower in the highest excited state and the lowest excited state, among them, the time of exciton filling increases from 0.33 to 0.79 ps for the highest excited state, while the time of exciton filling increases from 0.53 ps to 1 ps for the lowest excited state. Moreover, the two kinds of experiment provide complementary information and obtain the full image of interband relaxation process. Result shows that the bleach recovery of the 1 S transition shows an initial rise, but the fluorescence up-conversion signal for the 1 S transition is slower in rise time, which can provide help in the application of optoelectronic devices.-
Keywords:
- TGA-CdTe quantum dots /
- time-resolved spectroscopy /
- exciton dynamics
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[14] Wang H Y, Celso de Mello Donega, Andries Meijerink, Max Glasbeek 2006 J. Phys. Chem. B 110 733
[15] Kaniyankandy S, Rawalekar S, Verma S, Palit D K, Ghosh H N 2010 Phys. Chem. Chem. Phys. 12 4210
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[17] Dooley C J, Dimitrov S D, Fiebig T 2008 J. Phys. Chem. C 112 12074
[18] Pan L Y, Pan G C, Zhang Y L, Gao B R, Dai Z W 2012 J. Nanosci. Nanotechnol. 2 1
[19] Pan L Y, Zhang Y L, Wang H Y, Liu H, Luo J S, Xia H, Zhao L, Chen Q D, Xu S P, Gao B R, Fu L M, Sun H B 2011 Nanoscale 3 2882
[20] Zhang H, Wang L, Xiong H 2003 Adv. Mater. 15 1712
[21] Yu W W, Peng X G 2002 Angew. Chem. Int. Ed. 41 2368
[22] Kubo R, Kawabata A, Kobayashi S 1984 Annu. Rev. Mater. Sci. 14 49
[23] Pan L Y, Pan G C, Che X L, Wang L, Tamai N, Dai Z W 2011 Appl. Opt. 31 G31
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[1] Tomczak N, Jańczewski D, Han M 2009 Prog. Polym. Sci. 34 393
[2] Wu W Z, Zheng Z R, Liu W L, Yang Y Q, Su W H, Zhang J P, Yan Y X, Jin Q H, 2007 Chin. Phys. Soc. 56 2926
[3] Axt V M, Kuhn T 2004 Rep. Prog. Phys. 67 433
[4] Klimov V I, Mikhailovsky A A, Xu S, Hollingsworth J A, Leatherdale C A, Eisler H J, Bawendi M G 2000 Science 290 314
[5] Aiping Liu, Shuo Peng, Jian Chow Soo, Min Kuang, Peng Chen, Hongwei Duan 2011 Anal. Chem. 83 1124
[6] Lianzhe Hu, Xiaoqing Liu, Alessandro Cecconello, Itamar Willner 2014 Nano Lett. 14 6030
[7] Kajii Y, Nakagawa T, Suzuki S 1991 Chem. Phys. Lett. 181 100
[8] Peon J, Zewail A H 2001 Chem. Phys. Lett. 348 255
[9] Pohl D W, Denk W, Lanz M 1984 Appl. Phys. Lett. 44 651
[10] Masayuki Yoshizawa, Makoto Kurosawa 1999 Phys. Rev. A 61 01380801
[11] Klimov V I, McBranch D W 1998 Phys. Rev. Lett. 80 4028
[12] Gao B R, Wang H Y, Wang H, Yang Z Y, Wang L, Jiang Y, Hao Y W, Chen Q D, Sun H B 2012 IEEE Journal of Quantum Electronics 48 425
[13] Xu S, Mikhailovsky A A, Hollingsworth J A, Klimov V I 2002 Phys. Rev. B 65 045319
[14] Wang H Y, Celso de Mello Donega, Andries Meijerink, Max Glasbeek 2006 J. Phys. Chem. B 110 733
[15] Kaniyankandy S, Rawalekar S, Verma S, Palit D K, Ghosh H N 2010 Phys. Chem. Chem. Phys. 12 4210
[16] Peng P, Milliron D J, Hughes S M, Johnson J C, Alivisatos A P, Saykally R J 2005 Nano Lett. 5 1809
[17] Dooley C J, Dimitrov S D, Fiebig T 2008 J. Phys. Chem. C 112 12074
[18] Pan L Y, Pan G C, Zhang Y L, Gao B R, Dai Z W 2012 J. Nanosci. Nanotechnol. 2 1
[19] Pan L Y, Zhang Y L, Wang H Y, Liu H, Luo J S, Xia H, Zhao L, Chen Q D, Xu S P, Gao B R, Fu L M, Sun H B 2011 Nanoscale 3 2882
[20] Zhang H, Wang L, Xiong H 2003 Adv. Mater. 15 1712
[21] Yu W W, Peng X G 2002 Angew. Chem. Int. Ed. 41 2368
[22] Kubo R, Kawabata A, Kobayashi S 1984 Annu. Rev. Mater. Sci. 14 49
[23] Pan L Y, Pan G C, Che X L, Wang L, Tamai N, Dai Z W 2011 Appl. Opt. 31 G31
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