Intracellular gallium nitride microrod laser

We report laser emission from gallium nitride (GaN) microrods that are introduced into mammalian cells and the application of these microrods for cell labeling. GaN microrods were grown on graphene-coated SiO₂/Si substrates by metal-organic vapor phase epitaxy. The GaN microrods are easily detached from the substrates because of the weakness of the van der Waals forces between GaN and graphene. The uptake of microrods into HeLa cells via endocytosis and viability after uptake were investigated. Normal cellular activities, including migration and division, were observed over 2 weeks in culture. Furthermore, the photoluminescence spectra of the internalized microrods exhibited sharp laser emission peaks with a low lasing threshold of 270 kW/cm².