Here, we report for the first time a simple thermal oxidation strategy for the large area synthesis of Ge/GeO2 nanoholes from Ge and studied the luminescence of Ge/GeO2 and hole formation mechanism through phase and luminescence mapping. Photoluminescence mapping reveals that the emission in the visible range is only from the hole region, which provokes the necessity of the nanoholes. Such materials can also be used to convert ultraviolet to visible radiation for detection by conventional phototubes and to coat blue or ultraviolet diodes to obtain white light. © 2013 The Royal Society of Chemistry.