Colloidal synthesis of germanium nanocrystals

In this study, colloidal germanium nanocrystals were synthesized by a simple and novel method, and their optical properties were also studied. Polyvinyl alcohol (PVA) as a surface modifier was used to control the optical properties of colloidal Ge nanocrystals. Fourier transform infrared spectroscopy (FTIR) analysis was performed to identify the various functional groups present in the sample. TEM was used to confirm the formation of nanocrystals and observe the morphology and size of particles. To investigate the optical properties of the prepared nanocrystals, UV-Vis absorption and emission spectroscopy were also employed. Experimental results showed that the synthesized Ge nanocrystals have a spherical shape with the average particle size about 7 nm. FTIR spectrum indicates that Ge nanocrystals are well passivated with minimal surface oxidation. They exhibited luminous blue appearances of light. The emission peak is located at 455 nm wavelength. Also, the direct optical band gap of Ge colloidal nanocrystals was evaluated by Tauc’s theory. The crystallinity of Ge nanocrystals was also evaluated by X-ray diffraction pattern analysis. The X-ray diffraction peaks confirmed that Ge nanocrystals have been crystallized in the diamond cubic crystallization.