cm500260z_si_001.pdf (575.28 kB)
Generation of Singlet Oxygen by Photoexcited Au25(SR)18 Clusters
journal contribution
posted on 2014-05-13, 00:00 authored by Hideya Kawasaki, Santosh Kumar, Gao Li, Chenjie Zeng, Douglas
R. Kauffman, Junya Yoshimoto, Yasuhiko Iwasaki, Rongchao JinThe generation of highly reactive
singlet oxygen (1O2) is of major importance
for a variety of applications such
as photodynamic therapy (PDT) for cancer treatment, water treatment,
catalytic oxidation, and others. Herein, we demonstrate that 1O2 can be efficiently produced through the direct
photosensitization by Au25(SR)18– clusters (H−SR = phenylethanethiol or captopril) without
using conventional organic photosensitizers under visible/near-IR
(532, 650, and 808 nm) irradiation. 1O2 was
successfully detected by direct observation of the characteristic 1O2 emission around 1276 nm as well as three different 1O2-selective probes. Water-soluble Au25(captopril)18– clusters were explored
for cytocompatibility and photodynamic activity toward cancer cells.
In addition, selective catalytic oxidation of organic sulfide to sulfoxide
by 1O2 was demonstrated on the photoexcited
Au25(SC2H4Ph)18– clusters. It is suggested that the optical gap of Au25(SR)18 clusters (∼1.3 eV) being larger than the
energy of 1O2 (0.97 eV) allows for the efficient
energy transfer to 3O2. In addition, the long
lifetime of the electronic excited states of Au25(SR)18 and the well-defined O2 adsorption sites are
the key factors that promote energy transfer from Au25(SR)18– to molecular oxygen, thus facilitating
the formation of 1O2. Finally, neutral Au25(SR)180 can also produce 1O2 as efficiently as does the anionic Au25(SR)18−.