The unique optical, magnetic, and electronic properties of metal nanoparticles (NPs) give rise to photothermal, therapeutic, and electronic device applications, correspondingly. On the other hand, the limited range of the properties of simple spherical metal NPs has complicated their ability to function in many of these applications. Therefore, this chapter starts by reviewing a specific type of NP that can be classified into three main groups: silica coated with metal (silica@metal) NPs, metal coated with silica (metal@silica) NPs, and other similar forms of core@shell structures. The objective of this review is to introduce the concept of multi-responsive core@shell nanoparticles. More specifically, this chapter highlights "smart" core@shell composite NPs having multiple response mechanisms (e.g., temperature, light, and/or an applied magnetic field) due to the ability of these systems to perform a task by remotely responding to stimuli. Additionally, hydrogel-coated metal@silica NPs, with the ability to store drugs in a mesoporous silica (m-silica) interlayer, are examined because these nano-materials potentially provide substantial advantages for carrying cargos to targeted sites. To demonstrate this capability, we examine recent research that provided initial tests of composite NPs with a pH- and temperature-responsive hydrogel coating, including the application of an underlying m-silica interlayer to improve the capacity of these NPs to load and release small molecules.
Part of the book: Nanoparticles Technology