Chemistry of Singlet Oxygen with a Cadmium–Sulfur Cluster: Physical Quenching versus Photooxidation

Abstract

We 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.

Model peptide for anti-sigma factor domain HHCC zinc fingers: high reactivity toward 1O2 leads to domain unfolding

“…This was confirmed by the loss of 66 mass units corresponding to H 2 SO 2 upon MS/MS fragmentation. The formation of a sulfinate upon photooxidation of metal-bound thiolate has already been reported in many instances for Pt,35–37 Ni,38 Pd,38 Co39–41 and Cd42 complexes thereby supporting the formation of a sulfinate for Zn-bond cysteines in Zn·L ASD (HHCC) but the product with a 48-mass unit increase is more intriguing. As F4 does not contain any amino acid prone to oxygen incorporation upon photooxidation other than Cys34 ( i.e.…”

Fin-like CdSeS Nanoplatelets for Pesticide Sensing

“…It is postulated qualitatively that fluorescence quenching of CdSeS by dimethoate occurs as follows. Oleic acid ligands on the surface of FNPLs could participate in ligand exchange with dimethoate, 30 which is a polar pesticide. Effective fluorescence quenching occurs when primary vibrational modes or higher frequency overtones due to functional groups in a dimethoate mix with excited electronic states of CdSeS at comparable energies.…”

A Photoprotective Effect by Cation‐π‐Interaction? Quenching of Singlet Oxygen by an Indole Cation‐π Model System

“…This value can be determined by competition kinetics using singlet oxygen acceptors with known k r values. We used the well‐known singlet oxygen coacceptor, 1,5‐dihydroxynaphthalene, as described in detail in a previous paper by our laboratory (31). This involves monitoring the disappearance of 1 at 277 nm (where the 1,5‐dihydroxynaphthalene has an isosbestic point) and monitoring the increase of the oxidation product of 1,5‐dihydroxynaphthalene at 450 nm where neither the indole nor its oxidation products absorb.…”