Synthesis and photoluminescence of ultra-pure germanium nanoparticles

► Aerosol synthesis of defect and micro-strain free, ultra-pure Ge nanoparticles. ► TEM shows core–shell configuration with highly crystalline core material. ► Powder XRD verify highly pure nano-scale germanium. ► XPS demonstrates GeO x ( x ⩽ 2) shells cover the surfaces of the nanoparticles. ► PL short lived visible peak emission at 500 nm and long lived NIR peak emission at ∼1575 nm. We have used aerosol deposition to synthesize defect and micro-strain free, ultra-pure germanium nanoparticles. Transmission electron microscopy images show a core–shell configuration with highly crystalline core material. Powder X-ray diffraction measurements verify the presence of highly pure, nano-scale germanium with average crystallite size of 30 nm and micro-strain of 0.058%. X-ray photoelectron spectroscopy demonstrates that GeO x ( x ⩽ 2) shells cover the surfaces of the nanoparticles. Under optical excitation, these nanoparticles exhibit two separate emission bands at room temperature: a visible emission at 500 nm with 0.5–1 ns decay times and an intense near-infrared emission at 1575 nm with up to ∼20 μs lifetime.