Defect tailored NiO quantum dots via energy-efficient synthesis: Electronic transport and selective cytotoxicity

Abstract

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 (¿D), 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.

■ ACKNOWLEDGMENTS We would like to acknowledge DST-STIC, Sophisticated Test and Instrumentation Centre, CUSAT, Kochi, Kerala, for their support in conducting TEM analysis. Our gratitude also goes to the Advanced Materials Research Centre (AMRC) at the Indian Institute of Technology (IIT), Mandi, Himachal Pradesh, for their assistance with XPS measurements. We extend our sincere appreciation to the Central Sophisticated Instrumental Facility (CSIF), BITS Goa, for their invaluable support in conducting EDAX, PL, and Raman measurements. Special thanks to the Department of Chemical Engineering, BITS Goa, for their assistance with FTIR analysis. The authors would like to acknowledge the Department of Science and Technology (DST, Government of India) for financial support under the DST-FIST scheme (FIST No. SR/FST/PS-I/2017/21). J.Llorca is a Serra Hunter Fellow and is grateful to the ICREA Academia program and project 2021 SGR 0.061.

Postprint (published version)