), while the emission wavelength is unchanged. These vertical shifts can be understood as results of resonance energy transfer processes through which some portion of photo-excited excitons relax to the lowest bound state responsible for the S 2 emission. S2 peak can be attributed to the photoluminescence from the DCTC -. The excitation energy for the S 2 peak corresponds well to the UV-Vis absorption peak of DCTC -(see Fig. ). Hence, the S2 peak can be attributed to the photoluminescence from the DCTC -. λ ex ∼ 390 nm for the downshifted S RET the S 1 peak intensifies (see panels c and d in Fig. ). This indicates that the S 1 emission originates from a decomposed product of DCTC -. Mass spectrometry: Sample solutions of the doped melamine for the HPLC-CMS were prepared in deionised water. Acetonitrile-water mixture of various volumn ratios (see Table ) was used as mobile phase to run the HPLC-CMS experiments. Integrated mass spectrometer (Advion expression CMS) with HPLC was used to record the mass spectra for both positive and negative ions generated by electrospray ionization (ESI). The HPLC-CMS data of the mobile phase (m.p.) were also recorded to ascertain the preliminary peaks already present before loading the samples solutions.