Photophysical properties of CdSe quantum dot self-assemblies with zinc phthalocyanines and azaphthalocyanines

Photochemical & Photobiological Sciences Pub Date: 2012-12-17 DOI: 10.1039/C2PP25348H

Abstract

The formation of self-assemblies between CdSe quantum dots (QDs) and Zn phthalocyanines (Pc) and azaphthalocyanines (AzaPc) bearing alkylsulfanyl substituents and the photophysical properties of these assemblies were studied using both steady-state and time-resolved luminescence/absorption spectroscopy. The formation of the self-assemblies was accompanied by a blue shift of the Q band of the dyes and by a quenching of the CdSe QDs luminescence. The largest spectral shift of the Q-band was approximately 7 nm and was observed for pentan-3-ylsulfanyl-functionalised phthalocyanine (3). Assuming a 1?:?1 stoichiometry, the calculated binding constant was 4 × 104 M?1. Pc substituted with the bulky tert-butylsulfanyl groups (1) exhibited a smaller shift of the Q band. The quenching of the CdSe QDs luminescence by 1 was more effective than that observed for 3. The results indicated that the luminescence quenching may be due to a photoinduced charge transfer between 1 or 3 and the CdSe QDs. In contrast, the AzaPc (2) with the same substituents as 1 had little effect on the QDs luminescence. For all cases, we found an inefficient resonance energy transfer between the attached dyes and the CdSe QD. The formation of the self-assemblies had negligible effects on the photogeneration of the singlet oxygen, O2(1Δg), that was fully controlled only by the absorption of the light by the macrocycles.

Graphical abstract: Photophysical properties of CdSe quantum dot self-assemblies with zinc phthalocyanines and azaphthalocyanines
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