Photophysical insights on effect of gold nanoparticles over fullerene–porphyrin interaction in solution

• Fullerene–porphyrin (1) complexation is examined in presence of AuNp in toluene.
• AuNp causes effective reduction in the value of binding constant for C70–1 system.
• Fluorescence studies elicit quenching of 1 in presence of fullerene-AuNp mixture.
• DLS study reveals increase in the particle size of C70–1–AuNp nanocomposite.
• Energy transfer phenomenon takes place.

The present article reports the role of gold nanoparticles, i.e., AuNp (having diameter ∼2–4 nm), in non-covalent interaction between fullerenes (C60 and C70) and a monoporphyrin (1) in toluene. Both UV–vis and fluorescence measurements reveal considerable reduction in the average value of binding constant (Kav) for the C70–1 system (KC70–1(av) = 19,300 dm3 mol−1) in presence of AuNp, i.e., KC70–1–AuNp(av) = 13,515 dm3 mol−1 although no such phenomenon is observed in case of C60–1 system, viz., KC60–1(av) = 1445 dm3 mol−1 and KC60–1–AuNp(av) = 1210 dm3 mol−1. DLS study reveals sizeable amount of increase in the particle size of C70–1–AuNp nanocomposite, i.e., ∼105 nm, compared to C60–1–AgNp system, e.g., ∼5.5 nm which gives very good support in favor of decrease in the value of Kav for the former system. SEM study reveals that nanoparticles are dispersed in larger extent in case of C70–1–AuNp system. Time-resolved fluorescence study envisages that deactivation of the excited singlet state of 1 by C70 takes place at a faster rate in comparison to C60 in presence of gold nanoparticles.

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