Picosecond dynamics of cresyl violet H-aggregates adsorbed on SiO2 and SnO2 nanocrystallites

Abstract

The H‐aggregates of cresyl violet dye which are formed on the negatively charged SiO₂ and SnO₂ nanocrystallites, exhibit relatively short‐lived excitonic singlet state with a lifetime of about 35 ps. The difference absorption maximum (λ_max=470 nm) is blue shifted compared to the corresponding singlet excited state of monomer (λ_max=515 nm). Time‐resolved transient absorption measurements show that these dye aggregates are capable of injecting electrons from the triplet excited state into SnO₂ nanocrystallites. The rate constant for heterogeneous electron transfer as measured from the formation of cation radical and electron trapping in SnO₂ nanocrystallites was 2.0×10⁸ s⁻¹.