Dual photoluminescent blue and green emission bands by the enantiopure (S)-(+)-1-(4-bromophenyl)-N-1-phenylethylmethanimine crystals

Abstract Herein, the analysis of the (S)-(+)-1-(4-bromophenyl)-N-1-phenylethylmethanimine organic material in solid state is reported, i.e., the crystal structure, molecular packing, morphological and optical analysis, as well as the correlation of these parameters are presented. The crystalline phase and spatial group were established by X-ray Diffraction (XRD) studies. The surface morphology of the crystal was recorded by Scanning Electron Microscopy (SEM) technique. SEM images showed a packing with dense plates stacked and fragmented. The UV–Vis spectral analysis was registered in the ~350–700 nm (~4.13–1.77 eV) range. The band gap energy (Eg) was determined by the Tauc model and located at Eg ~3.45 eV. Two experimental emission bands were recorded by Photoluminescence (PL) at room temperature in the Vis-region located in the ~415 nm (~2.88 eV) and ~558 nm (~2.22 eV) ranges. These emission signals were identified as blue (BE) and green (GE) emission bands, respectively. By applying the theoretical Maxwell-Boltzmann model as a proxy to considering crystalline defects as fixed particles, the optical emission bands of PL were calculated suggesting that the crystalline defects (e.g., vacancies and molecular interstices) generated the GE and BE bands. The experimental-theoretical results have values very close to each other when comparing the relative maxima, as it is presumed that this optical phenomenon is generated by the crystalline defects. A Raman spectroscopy study was also performed.