Phase, current, absorbance, and photoluminescence of double and triple metal ion-doped synthetic and salmon DNA thin films.

We fabricated synthetic double-crossover (DX) DNA lattices and natural salmon DNA (SDNA) thin films, doped with 3 combinations of double divalent metal ions (M)-doped groups (Co-Ni, Cu-Co, and Cu-Ni) and single combination of a triple M-doped group (Cu-Ni-Co) at various concentrations of M ([M]). We evaluated the optimum concentration of M ([M]) (the phase of M-doped DX DNA lattices changed from crystalline (up to ([M]) to amorphous (above [M])) and measured the current, absorbance, and photoluminescent characteristics of multiple M-doped SDNA thin films. Phase transitions (visualized in phase diagrams theoretically as well as experimentally) from crystalline to amorphous for double (Co-Ni, Cu-Co, and Cu-Ni) and triple (Cu-Ni-Co) dopings occurred between 0.8 mM and 1.0 mM of Ni at a fixed 0.5 mM of Co, between 0.6 mM and 0.8 mM of Co at a fixed 3.0 mM of Cu, between 0.6 mM and 0.8 mM of Ni at a fixed 3.0 mM of Cu, and between 0.6 mM and 0.8 mM of Co at fixed 2.0 mM of Cu and 0.8 mM of Ni, respectively. The overall behavior of the current and photoluminescence showed increments as increasing [M] up to [M], then decrements with further increasing [M]. On the other hand, absorbance at 260 nm showed the opposite behavior. Multiple M-doped DNA thin films can be used in specific devices and sensors with enhanced optoelectric characteristics and tunable multi-functionalities.