Triplet Excited State Enhancement Induced by PDDA Polymer Assembled Gold Nanoparticles

Gold nanoparticles (AuNPs) have unique optical properties because of their characteristic localized surface plasmon resonances (LSPRs). Upon the excitation of LSPR, AuNPs can affect the adjacent organic molecules strongly in both the ground state and the excited state. Previously, only 2–3 fold of the plasmon enhancement effect on triplet state formation was displayed because of the random and uncontrollable formation of AuNP aggregates. Here, we utilize polymer PDDA to assemble AuNPs forming aggregates with strong plasmonic resonance. By means of transient UV–visible absorption spectroscopy, the triplet state of rose bengal enhanced by PDDA–AuNPs is directly monitored and the maximum enhancement is found to be ∼10 fold. The large enhancement should be mainly resulted from the plasmon effect of AuNP aggregates. Additionally, it is found that the triplet state enhancement effect of PDDA-assembled AuNPs is sensitive to concentration of the polymer and the size of AuNPs. These findings shed light on the appl...