Formation of Hexabranched GeO2 Nanoparticles via a Reverse Micelle System

Abstract

We report the first synthesis of GeO2 nanoparticles with six symmetrically arranged branches running along the long axis of each particle. The nanoparticles have a shape resembling that of a star fruit. A reverse micelle system with Triton X-100 serving as the capping surfactant for the aqueous phase and n-hexanol as the cosurfactant was adopted. Ge(OEt)4 was selected as the germanium source. Using the optimal synthesis procedure by reacting the mixture at room temperature for 3 h, hexabranched GeO2 particles with an average length of 185 nm were produced. The products have been examined by FE-SEM, TEM, X-ray diffraction, and FT-IR techniques. GeO2 nanoparticles with structually well-developed branches were gnereated only with solution pH values in the range of 0.9−1.1. At a low [H2O]/[Ge(OEt)4] molar ratio of 45, particles having a hexagonal bipyramidal shape but without branch formation were observed. Increasing this ratio to 90, branches begin to appear from the six side edges of the particles. By simp...