Role of Core-Shell Formation in Exciton Confinement Relaxation in Dithiocarbamate-Capped CdSe QDs.
Role of Core-Shell Formation in Exciton Confinement Relaxation in Dithiocarbamate-Capped CdSe QDs.
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DOI：
10.1021/acs.jpclett.7b01259
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发表时间：
2017-07
期刊：
影响因子：
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通讯作者：
S. Kaniyankandy;S. Verma
中科院分区：
文献类型：
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作者：
S. Kaniyankandy;S. Verma
研究了烷基二硫代氨基甲酸酯（ATC）封端的CdSe中激子离域的可能性，并与苯基二硫代氨基甲酸酯（PTC）进行了比较。我们发现一个红移ATC的PTC所获得的类似。我们的计算研究表明，在PTC和ATC的HOMO-LUMO间隙减少，虽然具有较低的位移。然而，TDDFT研究表明，与PTC覆盖的CdSe中的部分离域HOMO相比，ATC覆盖的CdSe更像是局域HOMO态，这暗示了两种结合基团之间电子相互作用的差异。我们假设硫层的形成作为观察到的红移的可能原因，通过S2-配体交换样品的吸收光谱的验证。CdS壳层的形成导致了大量的电子离域，因为CdSeCB与CdS处于紧密的共振，这与文献中先前得出的结论完全相反。
The possibility of exciton delocalization in alkyldithiocarbamate (ATC)-capped CdSe has been investigated for several alkyl groups and compared with phenyldithiocarbamates (PTCs). We find a bathochromic shift for ATC similar to the one obtained for PTC. Our computational studies show reduction in HOMO-LUMO gaps in both PTC and ATC, albeit with a lower shift. However, TDDFT studies revealed that ATC-capped CdSe is more of a localized HOMO state as compared with partly delocalized HOMO in PTC-capped CdSe, hinting at a difference in electronic interaction between the two binding groups. We hypothesized the formation of sulfide layer over the CdSe QDs as the possible reason for the observed bathochromic shift, as verified by absorption spectra of S2- ligand exchange samples. The formation of CdS shell leads to substantial electron delocalization because CdSe CB is in close resonance with CdS, which is exactly the opposite of what was previously concluded in the literature.