b2815 Tissue Engineering and Nanotheranostics “9.61x6.69”
108 Tissue Engineering and Nanotheranostics
2.2. Types of Magnetic Nanohybrids
2.2.1. Core–Shell Magnetic Nanohybrids
The past decades, researchers examined single nanoparticles and their
properties because such micro/nanoparticles show much better per-
formance than the bulk materials. Afterwards, in the late 1980s, mate-
rial investigators found that composite or sandwich colloidal particles
demonstrate excellent efficiency compared to their corresponding
single particles. Thin layers on the surface of nanoparticles produced
significant change in their properties and functionalities such as ther-
mal stability, catalytic activity, magnetic–optical–electronic properties
and chemical reactivity to develop more layers. In certain prospects,
they even exhibit some new characteristics. In recent years, especially
during the early 1990s, researchers have put in develop their efforts
to synthesized concentric multilayer nanostructured materials with
improved properties. Subsequently the terminology, multilayer nano-
structure, was recognized by “core/shell” structures and has been
receiving attention due to the demand of emerging technologies.
Generally, the inner material is called core and outer layered material
is refeved to as the shell. These types of architecture can be con-
structed with inorganic/inorganic and inorganic/organic interac-
tions.21–25 They may be spherical, eccentric, star-like, centric, or
tubular in shape and some are shown in Fig. 3.
The bottom-up approach has been applied more effectively than
the top-down approach in the synthesis of core/shell nanoparticles.
Moreover, several methods, such as sol–gel, hydrolysis, Stober
method, control hydrolysis and microemulsion, have been used to
synthesize numerous core–shell materials like Au/SiO 2 ,26,27 Ag/
SiO 2 ,^28 ZnO/SiO 2 ,^29 Au/TiO 2 ,^30 CdSe/ZnS^31 and also many polymers,
for example, PEG, PVP, dextran, chitosan and PVA. However, as we
are concerned only with magnetic core–shell nanohybrids in this
chapter, the following part will show some recent important examples
of complex core–shell nanohybrid structures.
A team from the Department of Chemistry at Massachusetts
Institute of Technology synthesized silica magneto-fluorescent nanopar-
ticles complex core–shell hybrid structure.^32 Initially, they prepared
