ABSTRACT
Haitao Zhang,a Jun Ding,b Xianhui Chen,c Hailang Zhang,d and Xiaohe Liue a International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan b Department of Material Science & Engineering, Faculty of Engineering, National University of Singapore, 117574 Singapore c Hefei National Lab of Physical Sciences Microscale, and Department of Physics, University of Science & Technology China, Hefei 230026, Anhui, People’s Republic of China d School of Chemical & Matter Engineering, Jiangnan University, Wuxi 214122, Jiang Su, People’s Republic of China e Department of Inorganic Materials, Central South University, Changsha, 410083 Hunan, People’s Republic of China zhanght@ustc.edu, and msedingj@nus.edu.sg
controllable sizes and shapes [1-2]. Besides typically spherical nanoparticles, polyhedra, rods, ellipsoids, plates, tripdods or tetrapods, core/shell and voided core/shell particles, nanocages, and dumbbells could be obtained in large quantities with narrow size distribution up to now [3-7]. Unique properties and anomalous behaviors were found in nanoscale magnetic materials. The exotic phenomena can be assignable to size effect, shape effect, structural disorder, antiphase boundaries, or a nonmagnetic layer at the surface. The understanding of synergic properties and rational design of nanomaterials are critical and prerequisites for further applications [1-7]. Despite these tremendous progresses, nanoscience is currently in a bit precarious status and infancy. To cater to great expectations for fundamental study and commercial applications, truly innovative solutions must be advanced in nanomaterial synthetic protocols [8]. As is well known, nanoparticles made of a single component usually hold one dominant property that is determined decisively by their intrinsic crystal structures and two crucial nanoscale geometrical parameters: size and shape. In order to be widely applicable, a single particle is desirable to possess controllable multifunctionality. Two strategies have been developed to fabricate multifunctional nanomaterials: surface molecular functionalization, and integration of different nanoscale components into a single nanoentity. Researchers now are turning their focus from simple-component to multicomponent hybrid nanomaterials that exhibit synergistic functions (such as optical/magnetic properties and optical/catalytic properties) and broaden potential applications [9-12]. The liquid-phase colloidal synthetic route has been proven to be powerful for engineering nanomaterials with modulated combination fashions and tunable properties. Not only the size, shape, and composition of discrete components can be designed systemically, but also the combination fashions can be engineered expectedly [11]. As one kind of the most important nanomaterials, magnetic nanomaterials represent significantly fundamental and commercial interests with a wide range of applications, including magnetic resonance imaging (MRI) contrast enhancement, multiterabit magnetic storage devices, conducting paints, rechargeable batteries, magnetic refrigeration systems, magnetic drug delivery, hyperthermia, magnetofection, optoelectronics, and magnetic biomolecule separation [12-14]. Single-component magnetic
nanoparticles (for example, Fe, Co, Ni, Fe2O 3, and Fe3O 4) with expected size and shape have been studied extensively and systemically [3, 4, 9-14]. Conventionally, single-component nanoparticles could be regarded as “artificial atoms” and be assembled periodically into nanocrystal superlattices with different crystal structures. Interestingly, multicomponent nanomaterials referred to as “artificial molecules” are being studied drastically and can be fulfilled through controllable attachment of functional molecules or several nanoscale domains in a way of resembling the organization of atoms. One hybrid multicomponent nanoparticle can be considered as a composite coalesced orderly and tightly by several nanocrystals of different components. Therefore, it often not only exhibits intrinsic properties of these independent components but also presents some uniquely synergic phenomena introduced by the interactions and coupling that occur among these different nanocrystals [9]. Several comprehensive reviews have been presented recently on morphology control and characterizations of single-component nanoparticles [2-7]. Thereby, here we focus specifically on inorganic hybrid nanoparticles based on magnetism: magnetic/ magnetic, magnetic/fluorescent, magnetic/optical, magnetic/ catalyst, magnetic/optical/catalyst, etc. Typically colloidal chemical routes, nanomagnetism knowledge, and possible applications of multicomponent magnetic nanomaterials will be presented briefly in this chapter.
