Abstract A magnetically separable Fe3O4@CdS type‐II core–shell nanohybrid (NH) photocatalyst, with excellent antibacterial properties and photocatalytic activity, was synthesized and characterized by means of structural, elemental, and morphological analyses. Steady‐state and time‐resolved emission and absorption spectroscopy were also exploited to realize the location of charge‐carrier wave functions in the NHs. The antibacterial activity of NHs was then evaluated against Escherichia coli (1.4×108 CFU mL−1; CFU=colony forming units) and Staphylococcus saprophyticus (1.2×108 CFU mL−1) as model strains of Gram‐negative and ‐positive microbes. Compared with CdS and Fe3O4, the as‐synthesized Fe3O4@CdS composite exhibited highly improved bactericidal activity and recyclability. Concentration values of 5.0 and 4.0 mg mL−1 were required for Fe3O4@CdS NHs to inhibit the growth of E. coli and S. saprophyticus, respectively. The contribution of OH. radicals to photocatalysis at the Fe3O4@CdS surface was also considered. Moreover, thiobarbituric acid reactive substances and protein carbonyl assay protocols have been exploited to monitor levels of oxidative damage to lipids and proteins in cells. Additionally, the photocatalytic activity of Fe3O4@CdS NHs was monitored for the degradation of xylenol orange dye. Compared with CdS and Fe3O4, as‐synthesized Fe3O4@CdS displayed superior performances in the photodegradation of xylenol orange. Possible mechanisms involved in the degradation of xylenol orange are also discussed.
