“9.61x6.69” b2815 Tissue Engineering and Nanotheranostics
Magnetic Nanohybrids for Magnetic Resonance Imaging 119
optical, and surface active properties. Therefore, Janus particles offer
a versatile platform of applications ranging from material science to
biology and catalysis.
For instance, very recently, Lucia Curri et al. prepared γ–Fe 2 O 3 –
TiO 2 Janus nanoparticles using the concept of hydrophobic interac-
tion between binary nanocrystals.70,71 Seeded colloidal technique was
used to join spherical superparamagnetic iron oxide and photoactive
TiO 2 rods in the form of Janus as shown in Fig. 12(a). The size distri-
bution (inset of Fig. 12(a)) showed that the average length of TiO 2
nanorod was about 18 nm and mean diameter of γ–Fe 2 O 3 was 8 nm.
They also observed the absorption alteration between TiO 2 and Janus
γ–Fe 2 O 3 –TiO 2 , and absorption spectra shifted from UV region to vis-
ible region because of narrow band gap of maghemite (2.3 eV) as
shown in Fig. 12(b).72–74 Similar kind of Janus nanoparticles can be
seen in reported Ref. 71 Further, Wu et al. synthesized spherical-
shaped Fe 3 O 4 –TiO 2 Janus nanocomposites by solvo-hydrothermal
method.^75 Figure 12(c) demonstrated the various magnification of
TEM and HRTEM image of single hetrojunction of Fe 3 O 4 –TiO 2 that
can be seen in Fig. 12(d). The small particle corresponding to TiO 2
with d-spacing of 0.3517 nm, and big particle related to Fe 3 O 4 with
d-spacing 0.2518 nm are clearly joined in the form of Janus. The crys-
tal structure of prepared multifunctional Fe 3 O 4 –TiO 2 nanocomposites
is shown in Fig. 12(e) and plane^440 and^422 indicated that both materials
are hybrid. Moreover, superparamagnetism nature of Fe 3 O 4 nanopar-
ticles and Fe 3 O 4 –TiO 2 Janus nanostructure with saturation magnetiza-
tion 58.95 and 14.90 emu/g are shown respectively, in Fig. 12(f).
Mesoporous silica shell has obtained significant interest owing to the
unique and special properties such as uniform pore size, large pore vol-
ume, high surface area, low cytotoxicity and multifunctionality which are
very beneficial in biomedical and energy application.76,77 Therefore,
another example of Janus nanohybrid was chose-from polymeric–inor-
ganic material. Shi et al. fabricated superparamagnetic Fe 3 O 4 nanoparti-
cles coated by SiO 2 combined with polystyrene sphere to form a Janus
structure using sol–gel method.78,79 The schematic illustration is shown in
Fig. 13(a). Miniemulsion polymerization has been revealed to be a sig-
nificant synthetic route to prepare the polymeric–inorganic nanohybrid
