ИСТИНА

Light absorption properties of metallophthalocyanines (MPcs) are characterized by intensive Q-bands in far red region and rather low absorption of other visible light wavelengths. Photoactivation of MPcs by wider range of wavelengths may be achieved by increasing the effective absorption cross section of MPcs through energy transfer from additional light-absorbing structures. Semiconductor nanocrystals, or so-called quantum dots (QDs), absorb light in a broad optical range from ultraviolet to near infrared. The fluorescence spectrum of QDs is rather narrow, and the position of their fluorescence emission maximum can be precisely adjusted by the diameter of the nanocrystal particles. Coating of QDs provides water solubility and electrostatic interaction with other structures due to polar groups bound to the surface. It allows creating artificial light-harvesting complexes, which can serve as highly effective energy donors. Creation of hybrid structures in solution is due to electrostatic interactions, without the use of additional reagents for the formation of covalent bonds, opens up a number of promising new areas of research and corresponding applications. We have investigated the hybrid structures based on ZnPcs, bearing 8 anionic or cationic substituents, and differently charged QDs with an emission maximum at 600 nm, one with a core of CdSeCdTe/ZnS with positively charged polymer shell "poly T-APS" (QD600p) and another with a core of CdTe with negatively charged carboxyl groups (QD600n). It was shown that in a mixtures of ZnPcs and QDs, stable hybrid complexes can be formed due to electrostatic interactions. In pair of QD600p and ZnPc8- the efficiency of energy migration from QD to ZnPc exceeded 0.9, corresponding to ~ 30 Å distance between the donor and the acceptor. After injection QD600p we observed fast almost 140% increase of fluorescence intensity of ZnPc8-, compared to the initial level of fluorescence. The fluorescence spectrum of the ZnPc8- after addition of the QD600p shifted to the red by approximately 5 nanometers, the fluorescence lifetimes increased by 7%. In other pairs of QDs and ZnPcs the increase of the acceptor fluorescence was insignificant. Thus, QDs can greatly expand the action spectrum of the ZnPcs that is of great interest for biological and medical MPcs applications.