The top-rated international Journal of Physical Chemistry C published a paper from the Laboratory of Nano-Bioengineering reporting basic research in photoinduced phenomena in quantum dots

The authors of the published study (Krivenkov, V., Samokhvalov, P., Zvaigzne, M., Martynov, I., Chistyakov, A., Nabiev, I. Ligand-mediated photobrightening and photodarkening of CdSe/ZnS quantum dot ensembles) have experimentally investigated the phenomenon of irreversible changes in fluorescence parameters resulting from radiation-induced charge transfer.

This is a major concern in quantum dots applications to the fields where their optical characteristics should remain stable for a long time, including bio-imaging, single-photon sources, molecular tracking, and lasing. Irradiation may either weaken the fluorescence (photodarkening) or enhance it (photobrightening).

The authors have discovered the mechanisms of these phenomena and developed a model of them. They have found that a change in the quantum yield and, hence, brightness of luminescence is related to transfer of charge carriers (electrons or holes, depending on the quantum dot type) from the core to the organic surface ligands, followed by the ligand desorption. These are single-photon processes; i.e., they only depend on the energy (wavelength) and total dose of the radiation, but not its intensity, as well as on the thickness and composition of the quantum dot's semiconductor shell. It has also been found that these processes can be largely suppressed by incorporating the quantum dots into a polymer matrix.

The model of photodarkening and photobrightening developed by the authors has not only theoretical, but also important practical implications, because it allows the optimal type of the quantum dot shell and optimal operational conditions to be selected for ensuring long-term stability of the fluorescent signal.

The Journal of Physical Chemistry C is a top-rated journal (with an impact factor of 4.5) published by the American Chemical Society. It publishes papers on a wide range of subjects, including nanomaterials and hybrid materials, an essential criterion for acceptance being that an article should provide new physical insight rather than merely report new data or applications.


Victor A. Krivenkov, junior researcher (

Maria G. Korenkova, director of external relations (

Laboratory of Nano-Bioengineering, Moscow Engineering Physics Institute
31 Kashirskoe shosse, 115409 Moscow, Russian Federation

© 2012 Laboratory of Nano-BioEngineering