PICOSECOND DYNAMICS OF CRESYL VIOLET H-AGGREGATES ADSORBED ON SIO2 AND SNO2 NANOCRYSTALLITES

The H-aggregates of cresyl violet dye which are formed on the negative ly charged SiO2 and SnO2 nanocrystallites, exhibit relatively short-li ved excitonic singlet state with a lifetime of about 35 ps. The differ ence absorption maximum (lambda(max)=470 nm) is blue shifted compared to the corresponding singlet excited state of monomer (lambda(max)=515 nm). Time-resolved transient absorption measurements show that these dye aggregates are capable of injecting electrons from the triplet exc ited state into SnO2 nanocrystallites. The rate constant for heterogen eous electron transfer as measured from the formation of cation radica l and electron trapping in SnO2 nanocrystallites was 2.0X10(8) s(-1). (C) 1996 American Institute of Physics.