Size-Dependent Non-FRET Photoluminescence Quenching in Nanocomposites Based on Semiconductor Quantum Dots CdSe/ZnS and Functionalized Porphyrin Ligands

Figure 6

Evaluated FRET efficiencies Φ_FRET for “QD-porphyrin” nanocomposites based on QDs with various CdSe core diameter and the same porphyrin H₂P(m-Pyr)₄ molecules (toluene, 295 K). (a) Integrated fluorescence intensity of individual H₂P(m-Pyr)₄ molecules (1) and enhanced integrated fluorescence intensity of H₂P(m-Pyr)₄ in the presence of CdSe/ZnS QDs (𝑑_CdSe=3.0, 𝑛=2) (2) at the same porphyrin concentrations and excitation conditions (𝜆_exc=465 nm) in both cases. (b) Experimental dependences of Φ_FRET efficiencies for the energy transfer QD → H₂P(m-Pyr)₄ on the molar ratio 𝑥 evaluated using data of Figure 6(a) for every nanocomposites and (1): 1—𝑑_CdSe=3.5 nm, 𝑛=0; 2—𝑑_CdSe=2.1 nm, 𝑛=2; 3—𝑑_CdSe=3.0 nm, 𝑛=2; 4—𝑑_CdSe=4.1 nm, 𝑛=2; 5—𝑑_CdSe=5.2 nm, 𝑛=2.

(a)

(b)