Triplet
exciton formation is essential for photosensitization-based
photochemistry and photobiology. The heavy atom effect (HAE), in the
form of either external or internal mode, is a basic mechanism for
increasing the triplet exciton yield of photosensitizers. Herein,
we report a new HAE mode by noncovalent cohosting of heavy atoms and
photosensitizers in a double-stranded DNA (dsDNA) matrix. With dsDNA
bearing several thymine (T) or cytosine (C) mismatches, heavy atoms
(e.g., Hg2+ or Ag+) and dsDNA-staining dyes
(photosensitizers) were spatially adjoined in close proximity, thus
resulting in enhanced phosphorescence and 1O2 generation from the photosensitizers. The dsDNA-hosted HAE provides
highly selective recognition for the heavy atoms, which is not applicable
in either the external or the internal mode. Considering the simpleness
and efficiency of the spatially adjoined HAE, as well as the functionality
of DNA, the proposed HAE mode is appealing for various singlet oxygen-
and phosphorescence-related applications.