Voltammetric Detection of Singlet Oxygen Enabled by Nanogap Scanning Electrochemical Microscopy.

Despite the significance of singlet oxygen ( 1 O 2 ) in several biological, chemical, and energy storage systems, its voltammetric reduction at an electrode remains unreported. We address this issue using nanogap scanning electrochemical microscopy (SECM) in substrate-generation/tip-collection mode. Our investigation reveals a reductive process on the SECM tip at -1.0 V (vs Fc + /Fc) during the breakdown of the Li 2 CO 3 substrate in deuterated acetonitrile. Notably, this value is approximately 0.9 V more positive than the reduction potential of triplet oxygen ( 3 O 2 ), consistent with thermodynamic estimates for the energy of the formation of 1 O 2 . This finding holds significant implications for understanding the reaction mechanisms involving 1 O 2 in nonaqueous media.