High performance UV photodetectors using Nd ³⁺ and Er ³⁺ single- and co-doped DNA thin films

Even though lanthanide ion (Ln ³⁺ )-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 Nd ³⁺ or Er ³⁺ and co-doping of Nd ³⁺ /Er ³⁺ 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 Ln ³⁺ ([Ln ³⁺ ] _O ). No topological disturbance in DNA DX lattices were observed up to [Ln ³⁺ ] _O , and significant enhancement in the physical properties was obtained at [Ln ³⁺ ] _O . The interactions between Ln ³⁺ and SDNA were examined using spectroscopic methods of UV–visible, Raman, and X-ray photoelectron spectroscopy (XPS). Current and photovoltage measurements for Ln ³⁺ -doped SDNA thin films under UV illumination with varying power intensities were conducted. Under UV illumination, the photocurrent and photovoltage of Ln ³⁺ -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 Nd ³⁺ , 10-fold for Er ³⁺ , and 13-fold for Nd ³⁺ / Er ³⁺ , compared to the pristine SDNA due to the additional charge carriers generated in Ln ³⁺ -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 Ln ³⁺ -doped SDNA thin films.