Enhanced catalytic and supercapacitor activities of DNA encapsulated β-MnO₂ nanomaterials

A new approach is developed for the aqueous phase formation of flake-like and wire-like β-MnO₂ nanomaterials on a DNA scaffold at room temperature (RT) within a shorter time scale. The β-MnO₂ nanomaterials having a band gap energy ∼3.54 eV are synthesized by the reaction of Mn(ii) salt with NaOH in the presence of DNA under continuous stirring. The eventual diameter of the MnO₂ particles in the wire-like and flake-like morphology and their nominal length can be tuned by changing the DNA to Mn(ii) salt molar ratio and by controlling other reaction parameters. The synthesized β-MnO₂ nanomaterials exhibit pronounced catalytic activity in organic catalysis reaction for the spontaneous polymerization of aniline hydrochloride to emeraldine salt (polyaniline) at RT and act as a suitable electrode material in electrochemical supercapacitor applications. From the electrochemical experiment, it was observed that the β-MnO₂ nanomaterials showed different specific capacitance (C_s) values for the flake-like and wire-like structures. The C_s value of 112 F g^-1 at 5 mV s^-1 was observed for the flake-like structure, which is higher compared to that of the wire-like structure. The flake-like MnO₂ nanostructure exhibited an excellent long-term stability, retaining 81% of initial capacitance even after 4000 cycles, whereas for the wire-like MnO₂ nanostructure, capacitance decreased and the retention value was only 70% over 4000 cycles. In the future, the present approach can be extended for the formation of other oxide-based materials using DNA as a promising scaffold for different applications such as homogeneous and heterogeneous organic catalysis reactions, Li-ion battery materials or for the fabrication of other high performance energy storage devices.