Core–shell nanoparticles are a special category of materials with nanostructures that have obtained more attention in recent times owing to their fascinating properties and extensive choice of applications in catalysis, photocatalysis, materials chemistry, biology, drug delivery, sensors and other electronic device applications. By wisely modifying the cores along with the shells material and morphology, a variety of core–shell nanostructures can be created with tunable properties that can perform vital roles in several catalytic and photocatalytic developments and promise sustainable solutions to current environmental remediation problems. Recently, the development of core–shell nanoparticles with Au, Ag, Pt, Pd, Zn, Ni etc. metals as a core and ZnO, TiO₂, SiO₂, Cu₂O, Fe₂O₃ and SnO₂ etc. metal oxide semiconductors as a shell has engrossed huge research interest in catalysis, photocatalysis, solar photovoltaics and so on owing to their tunable nanoscale functionalities in the core and shell particles. This review covers the core–shell nanomaterials, mainly, metal–metal oxide core–shell nanostructures with an overview of the recent advances in their synthesis, and applications. It includes a critical review of application of these materials towards photocatalytic wastewater purification and bacterial disinfections under UV and visible light irritation. It also includes a brief discussion on mechanisms of heterogeneous and homogeneous photocatalysis and the effect of different morphologies of photocatalysts in view of photocatalysis for wastewater treatment. Finally, recycling, reuse and actual photocatalysis in a photocatalytic reactor of core–shell nanostructures have also been discussed which is very important for a sustainable wastewater treatment. The future prospects of such core–shell nanoparticles for cancer treatment by hyperthermia, drug delivery and several other interesting applications have been covered with a distinct emphasis on their structural depending properties.

Nanosystems have shown encouraging outcomes and substantial progress in the areas of drug delivery and biomedical applications.