Photoinduced Photoluminescence Variations of CdSe Quantum Dots in Polymer Solutions

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• 作者：Vasudevanpillai Biju ; Ryodai Kanemoto ; Yuusuke Matsumoto ; Sayaka Ishii ; Shunsuke Nakanishi ; Tamitake Itoh ; Yoshinobu Baba ; Mitsuru Ishikawa
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：June 7, 2007
• 年：2007
• 卷：111
• 期：22
• 页码：7924 - 7932
• 全文大小：372K
• 年卷期：v.111,no.22(June 7, 2007)
• ISSN：1932-7455

文摘

Photoluminescence (PL) quantum efficiencies and lifetimes of CdSe quantum dots (QDs) were investigatedunder photoactivation in different chemical environments including polymer solutions and solvent systems.We observed considerable enhancement of the PL quantum efficiency of the QDs when photoactivated abovethe band gap in the presence of polymers such as poly(dimethyl siloxane) (PDMS), poly(vinyl pyrrolidone)(PVP), and poly(butadiene) (PBD). Furthermore, the PL spectra and the enhanced PL quantum efficienciesof the QDs were considerably stabilized under continuous photoactivation in the presence of dissolved polymers.Under photoactivation, the PL quantum efficiency was increased from 8% to 26-37% depending on thepolymer environment. An increase of the PL quantum efficiency was also observed in solvents such as CHCl₃and n-butanol. However, photoactivation of the QDs in solvents with small dipole moments such as n-hexaneand toluene resulted in substantial decreases of the PL quantum efficiency (from 8% to <1%). Thephotoactivated PL intensity of the QDs was stable in the presence of polymers as a result of static passivationof QDs' surface. In general, the increase of the PL quantum efficiency of the QDs under photoactivation wasassociated with an increase of the average PL lifetime values (from ~7 to ~12 ns). On the other hand, theincrease of the PL quantum efficiency (from 8% to 37%) of QDs in the presence of PVP was associated witha decrease of the average PL lifetime value (from 7.16 to 3.51 ns). From the PL variations of the CdSe QDsunder continuous photoactivation in the presence of different polymers and solvents, we determined thatstatic passivation of the surface defects by molecules in the environment plays an important role in the surface-related emission and stability of the photophysical properties of the QDs. The variations of the PL lifetimesand quantum efficiencies under different chemical environments were helpful not only in understanding theinvolvement of surface states in the deactivation processes of photoexcited QDs but also in identifying idealpolymers and solvents for photoinduced surface passivation of QDs.