Zhongjun Wang

One-pot green synthesis of biocompatible arginine-stabilized magnetic nanoparticles

A green one-step approach has been developed for the synthesis of amino-functionalized magnetite nanoparticles. The synthesis was accomplished by simply mixing FeCl2 with arginine under ambient conditions. It was found that the Fe2+/arginine molar ratio, reaction duration and temperature greatly influence the size, morphology and composition of magnetic nanoparticles. The arginine-stabilized magnetic nanoparticles were characterized by transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, thermogravimetric analysis, and Fourier transform infrared spectroscopy techniques. The results show that the prepared nanoparticles are spherically shaped with a nearly uniform size distribution and pure magnetite phase. The presence of arginine on the magnetic nanoparticle surface has been confirmed and the amount of surface arginine varies with the Fe2+/arginine molar ratio. The surface amine densities are calculated to be 5.60 and 7.84 micromol mg(-1) for magnetic nanoparticles prepared at 1:1 and 1:2 Fe2+/arginine molar ratio, respectively. The as-synthesized nanoparticles show superparamagnetic behavior at room temperature and good solubility in water. In addition, using a similar synthesis procedure, we have been able to synthesize superparamagnetic manganese and cobalt ferrite nanoparticles.

A one-dimensional network from the self-assembly of gold nanoparticles by a necklace-like polyelectrolyte template mediated by metallic ion coordination

A new approach to one-dimensional organization of gold nanoparticles (2-4 nm) is described, using poly(4-vinylpyridine) (P4VP) molecular chain as a template with the mediation of free Cu2+ ion coordination. The assembly was conducted on freshly prepared mica surfaces and in aqueous solution, respectively. The surface assembly was characterized by tapping mode atomic force microscopy (AFM), observing the physisorbed molecules in their chain-like conformation with an average height of 0.4 nm. By the mediation of Cu2+ ions, gold nanoparticles modified by 3-mercaptopropionic acid were deposited onto the molecular chains, evidenced by a clear increase in height. Generation of the network in solution is time-dependent and pH reversible, characterized by UV-vis absorption spectra and transmission electron microscopy (TEM). No comparable network is obtained without Cu2+ ions, indicating the significance of ionic mediation. A mechanism for the self-assembly in solution is proposed, and the nature of the mediation of Cu2+ ions was identified by x-ray photoelectron spectroscopy (XPS).

Spontaneously Patterned ZnO Nanoarrays

Currently, one-dimensional nanoarrays with patterned morphologies are receiving comprehensive attention due to their potential contributions in more regulated nanodevices. Numerous techniques have been developed to fabricate patterned nanoarrays (PNs) by using catalysts, templates, or professional equipment. However, current artificial methods have several inherent drawbacks from the standpoint of nanotechnology. For instance, most templating procedures are conducted in time-consuming operations and often employ high-temperature-processing conditions. Catalyst guiding methods may have the risk of introducing undesirable residues into the products, which is incompatible with high-quality nanodevices. Some novel lithography techniques, such as X-ray and electron-beam, are limited in patterning over large areas. Overall, these tedious and expensive operations can only be justified in the case of a few high-priced nanodevices, and are unlikely to be extended significantly in the near future. PNs should not be a laboratory luxury. Key to the generalization of this material is to develop a facile and cost-effective approach to yield high-purity PNs under mild conditions. The practical benefits of the low-temperature solution-growth methods motivated us to consider a daring proposal; that is, can PNs be formed directly from its native solution-growth process? Aiming at this goal, we explored the theoretical and experimental essences of the solution growth methods, and finally, established an appropriate approach to form spontaneously patterned, vertically aligned nanoarrays on different substrates. By using ZnO nanoarrays as a model system, the present solution-growth process took place at a low temperature ( 80 8C) and neither templates nor catalysts were necessary. This simple, economic and straightforward approach holds promise for overcoming several inherent limitations of the current artificial manners. The purity, orientation, electrical, biomedical, and photocatalytic properties of the as-prepared materials allow them to be applied in various high-quality nanodevices. Our journey commenced with a modified ZnO solutiongrowth experiment. A polystyrene pellet, in place of the plane substrate, was fixed in the middle layer of the nutrient solution (Figure 1 a). As a result, the coverage of the ZnO