Li Lijia, Zhang Meng, Rowell Nelson, Kreouzis Theo, Fan Hongsong, Yu Qiyu, Huang Wen, Chen Xiaoqin, Yu Kui
Engineering Research Center in Biomaterials , Sichuan University , Chengdu , Sichuan 610065 , People's Republic of China.
Institute of Atomic and Molecular Physics , Sichuan University , Chengdu , Sichuan 610065 , People's Republic of China.
J Phys Chem Lett. 2019 Oct 17;10(20):6399-6408. doi: 10.1021/acs.jpclett.9b02439. Epub 2019 Oct 8.
It is well-known that optical absorption and photoluminescence (PL) provide information that is sensitive to the size and size distribution of colloidal binary semiconductor quantum dots (QDs). To explore the nature of reaction products, clusters, and/or small-size QDs, we show that it is important to perform as well photoluminescence excitation (PLE) spectroscopy. For two non-hot-injection reactions of cadmium oleate (Cd(OA)) and selenium (Se) in 1-octadecene (ODE), we show that sequentially extracted products displayed a similar apparent red shift in both absorption and PL with a full width at half-maximum (fwhm) of ∼30 nm. We demonstrate that one reaction (with the presence of diphenyl phosphine (HPPh)) produced multiple types of clusters (with slightly different optical properties) in one ensemble, while the other reaction (without HPPh) yielded primarily small-size QDs. Our findings provide evidence for the probable existence of clusters within small-size CdSe QD products, the existence of which complicates the size determination of small-size CdSe QDs.
