Luminescent AlN Semiconductor Nanocrystals

Aluminum nitride III-V semiconductor nanoparticles are prepared in the liquid phase via a two-step synthesis. In a first step, a mixed amide-imide intermediate is prepared in liquid ammonia. In a second step, the ammonolysis is completed by microwave heating at 300 °C in [BMIm][NTf₂] as an ionic liquid to obtain crystalline β-AlN, which is usually known as a high-pressure phase. The nanoparticles have a size of 3.7 ± 0.7 nm. Particle size and chemical composition are examined by transmission electron microscopy, energy-dispersive X-ray spectroscopy, infrared spectroscopy, and X-ray powder diffraction. According to UV–vis spectroscopy and a Tauc plot, a bandgap of 5.2 eV is determined. The AlN nanoparticles show photoluminescence with bluish white emission and a quantum yield of 15%, which is a typical value for core-type semiconductor nanoparticles without a protecting shell. A liquid-phase synthesis of crystalline AlN nanoparticles (<10 nm) showing visible emission at room temperature is reported for the first time.