Figure 5.

Top: ignition of the coffee-Na₂O₂ mixture generates enough thermal radiation and light to turn on a miniature silicon photovoltaic device. Bottom: the ignitable mixture served as a heat source for the in-situ thermal transformation of ferric acetate (orange powder at far-left) into magnetic iron oxide (black solid at far-right). For this purpose, a small quartz tube was charged with the precursor and then merely dipped into the ignition mixture. Notice the release of smoke from the top rim of the tube due to thermal decomposition of ferric acetate.