Investigations of structural, optical and electrical properties of Ca2+ doped CuCoO2 nanosheets
In this work, we present hydrothermal synthesis of delafossite oxide Ca-doped CuCoO2 (CCCaO) nanosheets at low temperature of 100 °C. The crystal phase, morphology and chemical composition of these CuCoO2 (CCCO) based samples were comprehensively characterized by powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The size of CCCaO nanosheets decreased with increasing the Ca dopant, an optimized CCCaO nanosheets (~490 nm in lateral size, ~15 nm in thickness) was much smaller than CCO nanocrystals (~540 nm in lateral size, 85 nm in thickness). The specific surface area of these CCO based samples was increased with increasing the Ca content, an optimized CCCaO nanosheets present a high BET surface area as 28 m2 g−1. The XPS spectra and Raman spectroscopy analysis indicate that the Ca2+ dopant substitution on Cu+ site in CCCaO nanosheets. Moreover, the effects of Ca2+ dopant on optical and electrical properties of these CCO based samples were further studied. The optical properties measured at room temperature show a high absorbability (up to 90%) in the ultraviolet-visible-near infrared (UV-VIS-NIR) region, and the indirect band gap exhibits a significant blue-shift with increasing the Ca2+ concentration. The CCO nanocrystals own a higher electrical conductivity than CCCaO nanosheets, and present a good conductivity around 12.81, 4.47 and 0.69 s•m-1 for the CCO and CCCaO samples at room temperature. The facile fabrication process, tunable crystalline size, excellent optical absorption and electrical properties of these CCO based nanomaterials are encouraging for the development of future applications in photoelectric devices.