Phonon properties of nanosized MnWO4 with different size and morphology

Highly hierarchical barlike and flowerlike MnWO4 microcrystals have been synthesized for the first time by a hydrothermal method, where ethanolamine (EA) and cetyltrimethylamonnium bromide (CTAB) play important roles in directing growth and self-assembly of these structures. The possible formation process has been proposed. In addition, platelike nanosized MnWO4 was also synthesized by annealing of a precursor obtained by coprecipitation method. The obtained samples were characterized by XRD, SEM, TEM, Raman and IR methods. Raman spectra showed relatively weak dependence on particle size and morphology of the particles. In contrast to this behavior, IR-active bands showed pronounced shifts and changes in relative intensities on particle size and the morphology. Origin of this behavior is discussed. - Graphical Abstract: SEM images of MnWO4 particles prepared by hydrothermal process at 150 deg. C (left panel) and 200 deg. C (right panel). Highlights: → Hydrothermal synthesis with ethanolamine enables growth of hierarchical nanosized MnWO4 particles. → Annealing of a precursor obtained by coprecipitation method enables growth of platelike MnWO4 nanoparticles. → Raman and IR spectra of MnWO4 nanoparticles depend on both size and morphology of the nanoparticles. → We discuss origin of this behavior.