Enhancing the electrical, optical, and magnetic characteristics of DNA thin films through Mn²⁺ fortification

DNA is one of the most propitious biomaterials for use in nanoscience and nanotechnology because of its exceptional characteristics, i.e. self-assembly and sequence-programmability. In this study, we fabricate sequence-designed double-crossover (DX) DNA lattices and naturally available salmon DNA (SDNA) thin films modified with the transition metal ion Mn²⁺. Phase transition of DX DNA lattices from crystalline to amorphous form controlled by varying the concentration of Mn²⁺ is discussed and a critical transition concentration ([Mn²⁺]_C) is estimated. In addition, the electrical, optical, and magnetic properties of Mn²⁺-modified SDNA thin films including current, absorbance, photoluminescence, the X-ray photoelectron spectrum, and magnetization are studied to understand their conductivity, binding modes, energy transfer characteristics, chemical composition, and magnetism. Interestingly, the physical values such as the maximum current and photoluminescence, and the minimum absorbance, occur at around [Mn²⁺]_C =4 mM, which may be due to the optimal incorporation of Mn²⁺ into the SDNA. The magnetization and susceptibility of SDNA thin films with Mn²⁺, served as magnetic dipoles, are studied under different temperature and magnetic field. The magnetization of SDNA thin films with [Mn²⁺]_C shows an S-shaped curve, indicating ferromagnetism.