“…Interestingly, phase changes of the DX-DNA nanostructures from crystalline to amorphous occurred above a certain ion concentration (referred to as the optimum concentration, i.e., [M 2+ ] O,S or [Ln 3+ ] O,S , where S stands for single-ion doping), and extrema values of the physical quantities (e.g., maximum current at [M 2+ ] O,S and minimum absorbance at [Ln 3+ ] O,S ) were obtained at [M 2+ ] O,S or [Ln 3+ ] O,S . The measured [Co 2+ ] O,S , [Cu 2+ ] O,S , [Tb 3+ ] O,S , and [Eu 3+ ] O,S were 1.0, 6.0, 1.0, and 1.0 mM, respectively 22−24 (the yellow dots in Figure 2 indicate [Co 2+ ] O,S , [Cu 2+ ] O,S , [Tb 3+ ] O,S , and [Eu 3+ ] O,S ).…”