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Synthesis and bandgap variation of molecular-size CdSe clusters via electroporation of vesicles

机译：囊泡电穿孔法合成分子尺寸CdSe簇及其带隙变化

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摘要

Molecular-size uncapped CdSe clusters are synthesized via the electroporation of synthetic dioleoylphosphatidylcholine vesicles of diameter 178 nm. Cd2+ ions, originally entrapped in the vesicles, are ejected through the transient pores of the vesicle membrane into the bulk where they can react with SeSO32-3 ions in basic condition to form CdSe clusters at room temperature. Growth and self-aggregation of CdSe clusters is slowed down to timescales of days by their adsorption at the exterior surface of the vesicle, which permits spectral monitoring of the continuous growth process over a long period of time. Growth in the molecular size regime is found to entail novel blue-shifts of the characteristic absorption band. The blue-shift of the transition energy is in agreement with an analogous oscillation of the HOMO-LUMO gap calculated by the use of density functional theory for (CdSe)(n) clusters. The reason for the blue-shift absorption spectra of molecular-size CdSe clusters is interpreted as the higher stability and bigger gaps of magic number. On the basis of the similarity between the experimental and theoretical trends, the characteristic absorption peaks of 256 nm, 215 nm can be assigned to the monomer or dimer, trimer clusters of CdSe, respectively. Any further growth beyond trimers is associated with the customary monotonic red-shift of the absorption band, due to quantum size effects.
机译：分子大小的无盖CdSe簇是通过电穿孔合成直径178 nm的合成的油酰磷脂酰胆碱囊泡而合成的。最初被困在囊泡中的Cd2 +离子通过囊泡膜的瞬态孔喷入本体中，在室温下它们可以与SeSO32-3离子反应形成CdSe簇。由于CdSe团簇在囊泡外表面的吸附，其生长和自聚集作用被减慢到几天的时间尺度，从而可以长时间连续监测光谱。发现分子大小范围的增长需要特征吸收带发生新的蓝移。跃迁能量的蓝移与通过使用（CdSe）（n）团簇的密度泛函理论计算出的HOMO-LUMO间隙的类似振荡一致。分子大小的CdSe团簇的蓝移吸收光谱的原因被解释为更高的稳定性和更大的幻数间隙。根据实验趋势和理论趋势之间的相似性，可以分别将256 nm，215 nm的特征吸收峰分配给CdSe的单体或二聚体，三聚体簇。由于量子尺寸效应，超出三聚体的任何进一步的增长都与吸收带的惯常单调红移有关。

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