Surface energy-driven growth of crystalline PbS octahedra and dendrites in the presence of cyclodextrin-surfactant supramolecular complexes

Abstract

PbS crystals of cubic, octahedral, and dendritic shapes are synthesized in an aqueous solution that contains supramolecular complexes of beta-cyclodextrin (CD) and hexadecyltrimethylammonium bromide (CTAB). The morphology of the PbS crystals depends on the concentration of CD or CTAB in the reaction solution; for example, the branched dendritic structures evolve with an appropriate molar ratio of CD/CTAB supramolecular complexes and reaction time. Regardless of the CD/CTAB molar ratios, octahedral PbS crystals are observed at all compositions of CD/CTAB for the reaction times of 1-5 h, while self-assembled branched/dendritic structures are obtained only for CD/CTAB molar ratios of 0.5, 1, and 2 after a prolonged reaction, e.g., for 24-48 h. Systematic investigation reveals that both reaction time and CD/CTAB molar ratio are responsible for self-assembled branched/dendritic structures of octahedral crystals.