Core–shell (CS) nanostructures and their application based on magnetic and optical properties

Abstract

Core–shell nanomaterials have been an active area of research for their tailored multifunctional properties arising as a result of the coexistence of two or more nanostructured phases of different composition with one forming the shell on the surface of the other. This review highlights the key developments and current status of these core–shell nanostructures with special emphasis on those having interesting magnetic and optical properties. We also discuss bimetallic and functionalized core–shell nanostructures along with their potential applications. With the advent of highly sophisticated techniques, it is now possible to precisely examine and control the size and shape of the core and the shell in these nanostructures. Core–shell structures designed for magnetic properties have been tuned and such materials have found potential applications as MRI contrast and drug delivery agents. For instance, core–shell nanostructures which show response towards changes in the physiological pH have been shown to deliver drugs for curing cancer. Functionalized core–shell nanostructures have also been used to sense changes in pH of the system. Exciting photonic applications can be engineered by appropriate energy band alignment of the core and shell materials. The importance of core–shell nanocrystals can be gauged from the wide range of applications in the field of biomedical technology involving photonics and biophotonics, biological labels, multimodal bio-imaging, photodynamic therapy and drug delivery. In this review article, we have tried to focus on the recent developments in the field of core–shell nanostructures with applications ranging from photonics, magnetic sensors, drug delivery agents, medical diagnostics and photocatalysis. We begin with a brief introduction and then build on the information by focusing on the developments in the past ten years especially focusing on specific applications of current and future interest.