The synthesis of monodisperse (uniform-sized) nanoparticles is quite important because the properties of these nanoparticles depend on their dimensions. Although the synthesis of monodisperse nanoparticles had been reported by several groups, the amount of the products is in the sub-gram scale, which is too small for many applications.

Our paper describes a new, simple, inexpensive, and environmentally-friendly route used to synthesize large amounts of monodisperse (uniform-sized) nanoparticles. This synthetic method can be applied to the large-scale synthesis of uniform-sized nanoparticles and these monodisperse nanoparticles will have many important applications. These applications include terabit magnetic data storage media, biochemical labeling reagents, drug delivery systems and targeting, and contrast-enhancing materials in magnetic resonance imaging.

Nanoparticles, whose particle diameters are between 1 nm (1 nm = 10^-9 m) and 50 nm, are base-core materials for implementing many nanotechnology initiatives. In many applications, the production of uniform-sized nanoparticles is essential because the physical (electrical, optical, and magnetic) properties of these nanoparticles are directly dependent on the particle size. For example, the color sharpness of semiconductor nanoparticle-based display is strongly dependent on the uniformity of the nanoparticles.

However, producing uniform-sized nanoparticles was quite challenging because generally, mixtures of different-sized nanoparticles are produced and the subsequent size-sorting process is very difficult, whereby uniform-sized nanoparticles containing a very small quantity of less-than-a-gram are usually produced.

The current paper describes a new, simple, inexpensive, and environmentally-friendly (non-toxic) method to produce uniform-sized nanoparticles in as much as 40 grams in laboratory scale—compared to the 100 mg amount produced using conventional methods. This new method has made it possible for uniform-sized nanoparticles to be used in many industrial-scale applications.

The synthesis of monodisperse nanoparticles had been intensively pursued by many researchers since the synthesis of monodisperse CdSe nanoparticles was discovered by Moungi Bawendi’s group at MIT in 1993 (J. Am. Chem. Soc. 115: 8706-8715, 1993). We began working on this research in 1999, which is two years after Prof. Hyeon became a faculty member at the Seoul National University. We published a paper in the Journal Of The American Chemical Society (J. Am. Chem. Soc. 123: 12798-12801, 2001), titled, "Synthesis of highly crystalline and monodisperse maghemite nanocrystallites without a size-selection process," and the paper has been cited nearly 200 times during the past four years. Since then, our research group has published an additional 25 papers in prominent international journals on the subject of the synthesis of uniform-sized nanoparticles.

Uniform-sized nanoparticles of metals and metal oxides have attracted considerable attention because of their broad applications, which include magnetic storage media, ferrofluids, magnetic resonance imaging (MRI), magnetically guided drug delivery, medical diagnosis, and alternating-current (AC) magnetic-field-assisted cancer therapy. In realizing these potential applications, the large-scale synthesis of nanoparticles is essential, and this process allows the large-scale synthesis of monodisperse nanocrystals to take place via the utilization of a simple, inexpensive, and environmentally-friendly procedure.