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Chemistry of Singlet Oxygen with a Cadmium–Sulfur Cluster: Physical Quenching versus Photooxidation
journal contribution
posted on 2018-12-21, 00:00 authored by David
A. Cagan, Arman C. Garcia, Kin Li, David Ashen-Garry, Abegail C. Tadle, Dong Zhang, Katherine J. Nelms, Yangyang Liu, Jeffrey R. Shallenberger, Joshua J. Stapleton, Matthias SelkeWe
investigated the chemistry of singlet oxygen with a cadmium–sulfur
cluster, (Me4N)2[Cd4(SPh)10]. This cluster was used as a model for cadmium–sulfur nanoparticles.
Such nanoparticles are often used in conjunction with photosensitizers
(for singlet oxygen generation or dye-sensitized solar cells), and
hence, it is important to determine if cadmium–sulfur moieties
physically quench and/or chemically react with singlet oxygen. We
found that (Me4N)2[Cd4(SPh)10] is indeed a very strong quencher of singlet oxygen with total rate
constants for 1O2 removal of (5.8 ± 1.3)
× 108 M–1 s–1 in
acetonitrile and (1.2 ± 0.5) × 108 M–1 s–1 in CD3OD. Physical quenching predominates,
but chemical reaction leading to decomposition of the cluster and
formation of sulfinate is also significant, with a rate constant of
(4.1 ± 0.6) × 106 M–1 s–1 in methanol. Commercially available cadmium–sulfur
quantum dots (“lumidots”) show similar singlet oxygen
quenching rate constants, based on the molar concentration of the
quantum dots.