MnFe 2 O 4 , etc.), and metal alloys based on them (e.g., CoFe, FePt, CoPt, etc.).
Among them, Fe 3 O 4 nanoparticles are commonly used since they have wonderful
magnetism-responsive properties and are easy for synthesis and modification.
Traditional Fe 3 O 4 nanoparticles could be synthesized by four methods, including
coprecipitation, thermal decomposition, microemulsion, and hydrothermal synthesis [12]. In the coprecipitation method, for example, FeCl 2 and FeCl 3 were mixed
in H 2 O, and then NaOH was added to the mixture, followed by heating treatment to
form the Fe 3 O 4 nanocrystals [13]. The obtained nanoparticles were further used for
surface modification by aminopropyltriethoxysilane (APTES) or other silanization
agents for further covalent grafting [14]. Moreover, Fe 3 O 4 nanoparticle-grafted
one-dimensional or two-dimensional nanomaterials (e.g., graphene oxide nanosheets) could also be used for construction of the magnetic supramolecular assemblies after equipped with molecular recognition units for endowing the ability of
supramolecular interaction [15].
Another type of magnetic building blocks is heterometallic complexes, which are
mainly based on coordination chemistry. The coordination interaction between metal
ions and organic ligands through the Lewis acid/base interactions may lead to
spontaneous formation of heterometallic complexes with ordered and dynamic structures [16, 17]. Among them, the magnetic heterometallic complexes, also named single
molecular magnets (SMMs), are formed by coordination between the common transition metals (e.g., Mn, Fe, Co, Ni, V) or rare-earth metals (e.g., La, Dy, Er) in oxidation
states and their corresponding organic ligands [18–20]. For example, Kou et al.
synthesized H 2 pyaox-based mixed-valent {Mn 14 } cluster SMMs, named
[Mn
IV
2 Mn
III
10 Mn
II
2 O 8 (Hpyaox) 14 (pyaox) 2 -(N 3 ) 2 ](ClO 4 ) 4 (OH) 2 Á2MeOHÁ23H 2 O,
which displays an S = 6 spin ground state and slow magnetic relaxation [21].
Ibrahim et al. prepared a kind of tetrahedral heterometallic polyoxometalate
(POM) [Dy 30 Co 8 Ge 12 W 108 O 408 (OH) 42 (OH 2 ) 30 ]
56À (Fig. 1), which shows remarkable SMM behavior [11]. These magnetic complexes could be developed as the core
for construction of high-ordered supramolecular assemblies.
20.3 Construction of Magnetic Supramolecular Assemblies
By depending on the supramolecular interactions, such as host-guest interaction,
hydrophobic interaction, and coordination, the magnetic building blocks could be
dynamically self-assembled into zero-, one-, or two-dimensional nanostructures.
These assembling processes could be induced and regulated by specific stimuli,
especially the magnetic field and light.
20.3.1 Zero-Dimensional Supramolecular Nanocomposites
As the frequently produced magnetic supramolecular nanoassemblies, zero-dimensional magnetic supramolecular nanocomposites, e.g., vesicles, micelles, and particles, were abundantly constructed and used for biomedical applications (especially
for drug delivery and imaging) [22, 23]. In these nanocomposites, chemotherapeutic
20 Construction and Biomedical Application of Magnetic Supramolecular. . .
561
Among them, Fe 3 O 4 nanoparticles are commonly used since they have wonderful
magnetism-responsive properties and are easy for synthesis and modification.
Traditional Fe 3 O 4 nanoparticles could be synthesized by four methods, including
coprecipitation, thermal decomposition, microemulsion, and hydrothermal synthesis [12]. In the coprecipitation method, for example, FeCl 2 and FeCl 3 were mixed
in H 2 O, and then NaOH was added to the mixture, followed by heating treatment to
form the Fe 3 O 4 nanocrystals [13]. The obtained nanoparticles were further used for
surface modification by aminopropyltriethoxysilane (APTES) or other silanization
agents for further covalent grafting [14]. Moreover, Fe 3 O 4 nanoparticle-grafted
one-dimensional or two-dimensional nanomaterials (e.g., graphene oxide nanosheets) could also be used for construction of the magnetic supramolecular assemblies after equipped with molecular recognition units for endowing the ability of
supramolecular interaction [15].
Another type of magnetic building blocks is heterometallic complexes, which are
mainly based on coordination chemistry. The coordination interaction between metal
ions and organic ligands through the Lewis acid/base interactions may lead to
spontaneous formation of heterometallic complexes with ordered and dynamic structures [16, 17]. Among them, the magnetic heterometallic complexes, also named single
molecular magnets (SMMs), are formed by coordination between the common transition metals (e.g., Mn, Fe, Co, Ni, V) or rare-earth metals (e.g., La, Dy, Er) in oxidation
states and their corresponding organic ligands [18–20]. For example, Kou et al.
synthesized H 2 pyaox-based mixed-valent {Mn 14 } cluster SMMs, named
[Mn
IV
2 Mn
III
10 Mn
II
2 O 8 (Hpyaox) 14 (pyaox) 2 -(N 3 ) 2 ](ClO 4 ) 4 (OH) 2 Á2MeOHÁ23H 2 O,
which displays an S = 6 spin ground state and slow magnetic relaxation [21].
Ibrahim et al. prepared a kind of tetrahedral heterometallic polyoxometalate
(POM) [Dy 30 Co 8 Ge 12 W 108 O 408 (OH) 42 (OH 2 ) 30 ]
56À (Fig. 1), which shows remarkable SMM behavior [11]. These magnetic complexes could be developed as the core
for construction of high-ordered supramolecular assemblies.
20.3 Construction of Magnetic Supramolecular Assemblies
By depending on the supramolecular interactions, such as host-guest interaction,
hydrophobic interaction, and coordination, the magnetic building blocks could be
dynamically self-assembled into zero-, one-, or two-dimensional nanostructures.
These assembling processes could be induced and regulated by specific stimuli,
especially the magnetic field and light.
20.3.1 Zero-Dimensional Supramolecular Nanocomposites
As the frequently produced magnetic supramolecular nanoassemblies, zero-dimensional magnetic supramolecular nanocomposites, e.g., vesicles, micelles, and particles, were abundantly constructed and used for biomedical applications (especially
for drug delivery and imaging) [22, 23]. In these nanocomposites, chemotherapeutic
20 Construction and Biomedical Application of Magnetic Supramolecular. . .
561