Abstract: One embodiment of the present invention is a device and method for detecting the presence or absence of a signal nucleic acid. The device has comprising an electrode and a first nucleic acid covalently bound to the electrode. The first nucleic acid has two or more donor nucleotides capable of donating an electron. The donor nucleotides have a position in the first nucleic acid where one donor nucleotide is proximal to the electrode. The first nucleic acid has a modified nucleotide adjacent to one of the donor nucleotides. The modified nucleotide is capable of receiving an electron from said donor nucleotides upon photo-excitation and maintaining the electron for a first period of time when the first nucleic acid is unhybridized and a second period of time when the first nucleic acid is hybridized to the signal nucleic acid. The first and second periods are different. The electrode is in communication with the first nucleic acid to receive and donate electrons.