Surface Plasmons Control the Dynamics of Excited Triplet States in the Presence of Gold Nanoparticles

摘要

A molecule irradiated in the proximity of a metal nanoparticlencan be viewed as undergoing transmitter/receiver antenna interac-ntions;n1,2nthe process has also been described as analogous to a lightningnrod effect.n3nIn our case, methylene blue (MB) interacts with aqueousngold nanoparticles (AuNPs). Laser excitation produces the readilyndetectable MB triplet state,n3nMB*, in both the presence and absencenof AuNPs, but the 3nMB* yield and dynamics change significantly asna result of the MB AuNP interactions in both the ground and excitednstates. A molecule in its excited state located near an optical antennancan be viewed as a transmitter; similarly, a molecule (e.g., MB) in itsnground state and being excited by the localized plasmon field in thenvicinity of the AuNP antenna acts as a receiver.n2nThe antenna can benused to enhance molecular fluorescence; enhanced fluorescence isnsimply the reflection of an increased excited state concentration nearnthe nanoparticle, and similar effects should be anticipated in the casenof triplet states produced via intersystem crossing (ISC) from thenexcited singlet state.