Defect Tailored NiO Quantum Dots via Energy-Efficient Synthesis: Electronic Transport and Selective Cytotoxicity

Developing a cost-effective synthesis route for NiO at room temperature with a low calcination temperature (∼200 °C) remains a significant challenge. This study presents a novel, eco-friendly approach for synthesizing zero-dimensional NiO quantum dots (QDs) via a simple coprecipitation method using minimal reagents and energy-efficient processing. The resulting NiO QDs are obtained in powder form, enabling easy handling, storage, and integration into various applications. X-ray photoelectron spectroscopy, photoluminescence, and Raman spectra confirm the presence of interstitial oxygen (Oi) and nickel vacancies (VNi), indicative of intrinsic defects. Temperature-dependent conductivity analysis reveals two distinct regions separated by half the Debye temperature (θD), suggesting the formation of small-polaron-like bound Zhang–Rice states. Furthermore, cytotoxicity studies conducted on A549 and HeLa cancer cell lines and L132 normal cells demonstrate selective toxicity toward cancer cells. These findings highlight the potential of defect-engineered NiO QDs for multifunctional applications, including optoelectronics and biomedicine.