ИСТИНА

Two decades have passed since the first observation of long-term fluorescence intensity fluctuations (blinking) of single colloidal CdSe quantum dots (QDs) with a ZnS shell. Despite the enormous efforts (see for example [1]), the molecular mechanism of these fluctuations, showing a wide spectrum of characteristic timescales from hundreds of microseconds to hours, remains a mystery. While a number of models have been proposed to explain the phenomenon, all of these are rooted in two fundamental microscopic mechanisms, namely Efros/Rosen charging mechanism [2] and alternative mechanism of Frantsuzov and Marcus [3]. In order to distinguish the effects of the charging, Dan Oron's group conducted a series of experiments on designed colloidal quantum dots, incorporating a highly emissive CdSe core, which can be linked (or not linked) by a tunneling barrier to an engineered hole trap composed of PbS [4]. The experiments show the coexistence of two principally different types of fluorescence intensity fluctuations. We present a new physical model of the phenomenon combining two molecular mechanisms. In the absence of the inorganic trap fluorescence intensity fluctuations are caused by variations of the electron-phonon interaction value. When the hole trap is attached to the quantum dot the second type of fluctuations, based on the charging/neutralization mechanism, appears. The model quantitatively reproduces the properties of the single quantum dot long-correlated fluorescence intensity fluctuations including the intensity distribution and power spectral density. The study was supported by the Russian Foundation for Basic Research, project 16-02-00713. 1. P. Frantsuzov, M. Kuno, B. Janko and R. A. Marcus, Nature Physics 4 (2008) 519. 2. A.L. Efros and M. Rosen, Phys. Rev. Lett. 78 (1997) 1110. 3. P.A. Frantsuzov and R.A. Marcus, Phys. Rev. B 72 (2005) 155321. 4. R. Tenne, A. Teitelboim, P. Rukenstein, M. Dyshel, T. Mokari and D. Oron ACS Nano 7 (2013) 5084.