High performance UV photodetectors using Nd³⁺ and Er³⁺ single- and co-doped DNA thin films

Even though lanthanide ion (Ln³⁺)-doped DNA nanostructures have been utilized in various applications, they are rarely employed for photovoltage generating devices because of difficulties in designing DNA-based devices that generate voltages under light illumination. Here, we constructed DNA lattices made of synthetic strands and DNA thin films extracted from salmon (SDNA) with single-doping of Nd³⁺ or Er³⁺ and co-doping of Nd³⁺/Er³⁺ for high performance UV detection. The topological change of the DNA double-crossover (DX) lattices during the course of annealing was estimated from atomic force microscope (AFM) images to find the optimum concentration of Ln³⁺ ([Ln³⁺]_O). No topological disturbance in DNA DX lattices were observed up to [Ln³⁺]_O, and significant enhancement in the physical properties was obtained at [Ln³⁺]_O. The interactions between Ln³⁺ and SDNA were examined using spectroscopic methods of UV-visible, Raman, and X-ray photoelectron spectroscopy (XPS). Current and photovoltage measurements for Ln³⁺-doped SDNA thin films under UV illumination with varying power intensities were conducted. Under UV illumination, the photocurrent and photovoltage of Ln³⁺-doped SDNA thin films increased with increasing applied external voltages and input power intensities, respectively. In addition, we observed considerable increases in photovoltage responses, i.e., 5-fold increase for Nd³⁺, 10-fold for Er³⁺, and 13-fold for Nd³⁺/ Er³⁺, compared to the pristine SDNA due to the additional charge carriers generated in Ln³⁺-doped SDNA thin films. Device performance was measured in terms of photovoltage responsivity and retention characteristics. These phenomena indicate the high stability and substantial endurance characteristics of Ln³⁺-doped SDNA thin films.