Optoelectric and photocatalytic characteristics of DNA thin films embedded with transition metal ion-doped ZnO nanorods

While the importance of ZnO nanorods (NR) and DNA molecules has been comprehensively addressed, the characteristics of composite samples comprised of ZnO NRs and DNA have rarely been discussed. Here, we introduced efficient methods to construct ZnO NR powders doped with Ni⁺² and Mn⁺² via a thermal plasma process and Ni⁺²- and Mn⁺²-doped ZnO NR-embedded DNA thin films (labelled Ni–ZnO-DNA-TF and Mn–ZnO-DNA-TF) via drop-casting. The main focus was on investigating the composites’ physical characteristics with varying concentrations of NRs. Based on X-ray diffraction measurement, we observed the crystalline structure of the synthesised ZnO NRs in terms of a Wurtzite hexagonal structure. X-ray photoelectron spectroscopy (XPS) and ultraviolet (UV)–visible spectroscopy were also performed, with the current–voltage properties investigated. The XPS spectra indicated the presence of Zn, Ni and Mn elements in the NRs, as well as core elements in the DNA, while the absorbance and current of the DNA samples with Ni (Mn)–ZnO NRs exhibited a wide absorption range in the UV region and an enhancement of the conductivity. Finally, photocatalytic measurement of specific organic dyes such as methylene blue (MB) and methyl orange (MO) under UV irradiation was carried out to better understand the photocatalytic effect. A notable difference in the degradation of the MB and MO with the ZnO NRs (acting as the photocatalyst) and DNA (acting as an inhibitor of photocatalytic activity) was determined using the degradation rate, which provided relevant information regarding the dye degradation speed under UV light.