The LAL technique, which is a ¡®¡®top-down¡¯¡¯ method,can be used to produce a well-dispersed colloidal semiconductor ofGe NPs without using any protective organic agents. The quantum-size and clean surface of LAL-induced Ge NPs are beneficial forexploring intrinsic physicochemical properties of semiconductorGe NPs. For the first time, it is reported that an interesting spontaneousgrowth process of the metastable Ge NPs and associated structuralevolution from an initial amorphous state to a final cubic structure,with a tetragonal structure as an intermediate phase. The initial Ge NPs in amorphous structure showed spontaneous growth behavior byaging Ge colloids in deionized water under ambient temperature, which gradually evolved into a metastabletetragonal structure as an intermediate phase and then transformed into the stable cubic structure, beingconsistent with the Ostwald¡¯s rule of stages for the growth in a metastable system. The LAL-derived Ge NPs significantly exhibit excellent chemical reductiveability similar to that of zero-valent iron NPs. Various organic molecules, such as 2,5-dichlorophenol, MO, can be quickly degraded andmetal Cr(VI) ions can be reduced, particularly by using fresh andsmall Ge NPs. The LAL-induced Ge NPs with clean surface may findspecial applications in the biomedical field, as well as in catalysis andin battery, while due to the instability of the colloidal system it may benecessary to introduce further surface functionalization with additional molecules or by being composited with other structures.
Jun Liu, Changhao Liang*, Zhenfei Tian, Shuyuan Zhang, Guosheng Shao, ¡°Spontaneous growth and chemical reduction ability of Ge nanoparticles¡±, Scientific Report, 2013, 3, 1741.
Figure 1.The characterization for the spontaneous growth and phase transition behaviors of Ge nanoparticles.
Figure 2. Dechlorination mechanisms for fresh amorphous Ge NPs react with 2,5-dichlorophenol.