Study of optical properties of GeO2 nanocrystals as synthesized by hydrothermal technique

The GeO2 nanocrystals (α-quartz type structure) with β-phase are synthesized at relatively lower temperature by hydrothermal route using autoclave. All samples are characterized by XRD, FESEM, EDS, TEM, photoluminescence (PL) and UV–vis absorption spectroscopy techniques. Synthesized nanocrystals have uniform shape and uniform size distribution for a particular synthesis condition, which is about 30–300 nm depending on synthesis conditions. The XRD results indicate that grown GeO2 crystals only shows peak related to α-quartz structure with lattice parameters a = 4.985 Å and c = 5.648 Å. UV–vis absorption spectroscopy measurements reveal the bandgap energies corresponding to the GeO2 α-quartz structure. Synthesized nanocrystals are capable to emit strong blue light around 425–435 nm under excitation of 300 nm and 325 nm and consequently the as synthesized material can be used in integrated optical devices.

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► β-Phase GeO2 nanocrystals (α-quartz structure) synthesized by hydrothermal route.
► The grains of the samples get separated apart with increasing synthesis pressure.
► Uniform size distribution of GeO2 nanocrystals for a specific synthesis condition.
► Band gap energies of the nanocrystals are in well agreement with theoretical works.
► Samples emit strong blue light under excitation at room temperature.