Photodegradation of orange II dye using p-n junction NiO/TiO₂ composite, and assessment of its biological activities

The chemical reduction method was used to synthesize nickel oxide particles (NiO) and NiO supported on titanium dioxide (NiO/TiO₂ nanocomposite). The composites were characterized through scanning electron microscopy (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The morphological investigation showed that pseudocubic NiO are present in dispersed as well as agglomerated forms. Whereas NiO particles (<200 nm) are evenly deposited over the surface of TiO₂ in NiO/TiO₂ composite. The formation of NiO and NiO/TiO₂ was also verified by XRD analysis. The synthesized NiO and NiO/TiO₂ were used as photocatalysts for the degradation of Orange II (OII) dye. According to the degradation investigation, both NiO and NiO/TiO₂ composite degraded OII dye more efficiently when exposed to UV light. The results indicated that NiO degraded 93% and NiO/TiO₂ composites degraded approximately 96% of OII dye within 30 min. Both photocatalysts are highly sustainable and have significant OII dye degradation recyclability. Moreover, NiO and NiO/TiO₂ exhibited promising bioactivities (antioxidant activity of 80%) against the pathogenic bacteria Citrobacter and Providencia, which is comparable with the standard ascorbic acid (88%).