Aqueous germanate ion solution promoted synthesis of worm-like crystallized Genanostructures under ambient conditions

Abstract

This work demonstrates that it is possible to synthesize crystallized Ge nanostructuresdirectly in an aqueous medium under ambient conditions by using widely availableGeO2 (in the form of germanate ions) as a precursor. The reaction of germanate ions withNaBH4 in an aqueous medium resulted in highly hydrogenated Ge that couldbe transformed into crystallized Ge after an air-drying treatment. TheNaBH4/GeO2 molar ratio, reaction time and drying temperature were optimized for the synthesis ofcrystallized Ge products. Furthermore, the reaction time has an influence onthe size and shape of the final crystallized Ge products. A reaction time of 12 hcould result in crystallized Ge powder samples that contain ultra-small (5–20 nm)particles and larger (50–100 nm) particles. By controlling the reaction time to 24 h, aGe powder product consisting of worm-like crystallized Ge nanostructures withdiameters of 10–80 nm and lengths up to 1000 nm was obtained. The possiblereaction and growth mechanisms involved in this method were investigated. Thisnew synthetic route may be a good candidate for synthesizing a wide variety ofcrystallized Ge nanomaterials and devices due to its low cost, low safety risk,facileness, high yield (above 70% and in gram scale) and convenience for adding otherchemicals (i.e. dopants or morphology modifying agents) into the reaction system.