Son Juhee, Choi Dongsun, Park Mihyeon, Kim Juyeong, Jeong Kwang Seob
Department of Chemistry, Korea University, Seoul 02841 Republic of Korea.
Department of Chemistry and Research Institute of Natural Sciences, Gyeongsang National University, Jinju 52828, Republic of Korea.
Nano Lett. 2020 Jul 8;20(7):4985-4992. doi: 10.1021/acs.nanolett.0c01080. Epub 2020 Jun 9.
An increase in the carrier density of semiconductor nanocrystals can gradually change the origin of the optical property from the excitonic transition to the localized surface plasmon resonances. Here, we present the evolution of the electronic transition of self-doped AgSe colloidal quantum dots, from the intraband transition to the localized surface plasmon resonances along with a splitting of the intraband transition (1P-1S). The minimum fwhm of the split intraband transition is only 23.7 meV, which is exceptionally narrow compared to that of metal oxide nanocrystals showing LSPRs, inferring that the electron-electron scattering is significantly suppressed due to the smaller carrier density. The splitting of the intraband transition mainly results from the asymmetrical crystal structure of the tetragonal AgSe CQDs and becomes distinct when the nanocrystal changes its crystal structure from the cubic to tetragonal structure. Maximizing the discrete energy levels in the quantum dot along with mixing with plasmonic characters may provide opportunities to fully harness merits of both the quantum confinement effect and localized surface plasmon resonance characters.
半导体纳米晶体载流子密度的增加会逐渐改变光学性质的起源，从激子跃迁转变为局域表面等离子体共振。在此，我们展示了自掺杂AgSe胶体量子点的电子跃迁演变，从带内跃迁到局域表面等离子体共振，同时伴随着带内跃迁（1P - 1S）的分裂。分裂后的带内跃迁的最小半高宽仅为23.7毫电子伏特，与显示局域表面等离子体共振的金属氧化物纳米晶体相比异常狭窄，这表明由于载流子密度较小，电子 - 电子散射受到显著抑制。带内跃迁的分裂主要源于四方相AgSe胶体量子点的不对称晶体结构，并且当纳米晶体从立方结构转变为四方结构时变得明显。使量子点中的离散能级最大化并与等离子体特性混合，可能为充分利用量子限制效应和局域表面等离子体共振特性的优点提供机会。
