Plasmon-Mediated Photoelectrochemical Hot-Hole Oxidation Coupling Reactions of Adenine on Nanostructured Silver Electrodes

Surface-enhanced Raman spectroscopy (SERS) has been widelyappliedin the identification and characterization of DNA structures withhigh efficiency. Especially, the SERS signals of the adenine grouphave exhibited high detection sensitivity in several biomolecularsystems. However, there is still no unanimous conclusion regardingthe interpretation of some special kinds of SERS signals of adenineand its derivatives on silver colloids and electrodes. This Letterpresents a new photochemical azo coupling reaction for adenyl residues,in which the adenine is selectively oxidized to (E)-1,2-di-(7H-purin-6-yl) diazene (azopurine) in thepresence of silver ions, silver colloids, and electrodes of nanostructuresunder visible light irradiation. The product, azopurine, is firstfound to be responsible for the SERS signals. This photoelectrochemicaloxidative coupling reaction of adenine and its derivatives is promotedby plasmon-mediated hot holes and is regulated by positive potentialsand pH of solutions, which opens up new avenues for studying azo couplingin the photoelectrochemistry of adenine-containing biomolecules onelectrode surfaces of plasmonic metal nanostructures.

Automated summary

Surface-enhanced Raman spectroscopy (SERS) is widely usedfor efficient identification and characterization of DNA structures. The SERS signals of the adenine group show high detection sensitivity in various biomolecular systems. However, there is still no consensus on the interpretation of certain types of SERS signals of adenine and its derivatives on silver colloids and electrodes. This study introduces a new photochemical azo coupling reaction for adenyl residues, which selectively oxidizes adenine to azopurine in the presence of silver ions, silver colloids, and nanostructured electrodes under visible light irradiation. The resulting azopurine is found to be responsible for the SERS signals. This photoelectrochemical oxidative coupling reaction is facilitated by plasmon-mediated hot holes and regulated by positive potentials and solution pH, providing new insights into the study of azo coupling in the photoelectrochemistry of adenine-containing biomolecules on plasmonic metal nanostructure electrodes.