Studying on the steady-state and time-resolved fluorescence characteristics of melamine

Electronic emission spectral characteristics of melamine solution have been investigated by processing its steady-state emission spectrum with the second derivative method. It was found that the emission spectrum can be fitted into three separated Gaussian curves. The decay-associated emission spectra of lifetime tau(1) can be fitted to be one Gaussian curve, and that of lifetime tau(2) can be fitted into the other two Gaussian curves. These three Gaussian curves correspond to the steady-state emission spectral, showing that melamine has two fluorescent structures. The density functional theory (DFT) method was used to optimize the structures of the weak interaction clusters C(3)H(6)N(6)-(H(2)O)(n) (n=1-6). The structures of those clusters were obtained, and the energies of HOMO and LUMO were analyzed. It is found that the theoretical model C(3)H(6)N(6)-(H(2)O)(4) matches well with the experiment when the bonding number n is 4.