Spectroscopic and Capacitance Characteristics of DNA Thin Layers Embedded with Semiconducting ZnO and CuO Nanoparticles

Advances in semiconductor metal oxide nanoparticles (NPs), such as ZnO and CuO NPs, have allowed the construction of novel and efficient optoelectronic devices and sensors. Deoxyribonucleic acid (DNA) molecules, which are among the most versatile biomaterials, have proven to be a useful template for arranging and decorating nanomaterials, significantly enhancing their specific functionalities. In this study, we fabricated p-type ZnO and n-type CuO NP-embedded DNA thin layers via a facile drop-casting method. Additionally, cetyltrimethylammonium surfactant-modified DNA (CDNA) thin layers with semiconducting NPs were constructed to expand the usability in an organic solvent. Optical and electrical characterizations of the ZnO and CuO NP-embedded DNA and CDNA thin layers are essential. Thus, DNA and CDNA thin layers with various concentrations of ZnO and CuO NPs were characterized via X-ray diffraction (XRD) spectroscopy, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, transmittance and absorption spectroscopy, and photoluminescence spectroscopy. These measurements provided crucial information regarding the complexes, such as the chemical composition, binding modes, and energy transition. In the XRD spectra, we observed that the d-spacing of the DNA duplexes and the crystalline phase of the NPs did not change in the complex, indicating that there was no alteration of the structural characteristics of the materials. The bandgap energies—4.16 eV for pristine DNA and 3.89 eV for CuO NP-embedded DNA—were estimated according to the absorption spectra. Moreover, the current and dielectric constant of the ZnO and CuO NP-embedded DNA and CDNA thin layers were measured for investigating the basic electrical characteristics of the samples, which were explained in detail according to the energy-band diagram. The specificity of the optoelectronic characteristics of NP-embedded DNA and CDNA thin layers controlled by [NP] can be utilized in various functional optoelectronic devices and sensors.