Finally, Figure shows the UV-Vis absortion spectra of TCNE and melamine dissolved in a mixture of THF and water (the precursor solutions for the doped melamine crystals). They exhibit the UV absorption edge of melamine at about 250 nm and a weak absorption at about 470 nm, in addition to the same peaks as for the pure TCNE in a mixture of THF and water. As the absorption at 470 nm is not observed for pure melamine or TCNE in aqueous THF as in panel b, it should originate from some interaction between TCNE and melamine, or a change in the state of TCNE due to the presence of melamine acting as a weak base in the solution.