Hydrothermal Synthesis and Photoluminescence of Hierarchical Lead Tungstate Superstructures: Effects of Reaction Temperature and Surfactants

Lead tungstate (PbWO4) crystals with unique hierarchical morphologies have been successfully synthesized in the presence of a triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (EO70-PO20-EO70, P-123) under mild hydrothernial conditions. When reaction temperature is changed from 140 to 180 and 220 degrees C, the as-obtained PbWO4 samples can vary from flat tubular to rod-shaped arrays and complex slabs with porous film texture on their surface. Meanwhile, by using polyvinylpyrolidone (PVP), cetyltrimethylammonium bromide (CTAB), and hydroxycellulose with distinct functional groups as structure-directing agents, PbWO4 samples such as polyhedrons and rods with porous groove texture, as well as tube-shaped aggregate bundles, can be obtained. The optical properties of the as-made PbWO4 samples with various morphologies were examined by photoluminescence (PL) and Raman spectroscopy. Results show that PL of the rod-like arrays and microtube structures is redshifted relative to that of the complex slab sample. In general, the present synthesis route may be extended to prepare other inorganic nanomaterials with special functions.