(432d) Synthesis of Hollow and Porous Zinc Sulfide Spheres | AIChE

(432d) Synthesis of Hollow and Porous Zinc Sulfide Spheres

Authors 

Liu, S. - Presenter, The University at Buffalo (SUNY)
Kaus, M. - Presenter, The University at Buffalo (SUNY)
Swihart, M. T. - Presenter, University at Buffalo (SUNY)


Nanostructured zinc sulfide can provide unique photonic, electronic, and catalytic properties that are of interest for applications ranging from bioimaging to photocatalysis. In the work presented here, we have prepared hollow or porous ZnS nanospheres by spray pyrolysis of inexpensive, water-soluble precursors with polymeric additives used to template specific morphologies. Zinc acetate and thiourea are used as the precursors for ZnS synthesis. These compounds can react to form bis-thiourea zinc acetate (BTZA) at around 50°C and then precipitate from aqueous solution at higher temperature. ZnS is produced from the decomposition of BTZA. Addition of poly ethylene glycol methyl ether (PEG) into the aqueous precursor solution leads to formation of hollow nanospheres. In this case, evaporation of water and precipitation of PEG and BTZA leads to a core/shell structure, followed by pyrolysis of the PEG core upon further heating. Addition of polyvinylpyrrolidone (PVP) to the ZnS precursors produces porous particles. The pyrrolidone groups of PVP can coordinate to ZnS to form PVP-ZnS nanocomposites, with PVP distributed throughout the spheres. Further heating leads to pyrolysis of PVP, leaving behind porous ZnS nanospheres. In both cases, the size distribution of the nanospheres, from TEM imaging, ranges from 20 nm to 200 nm. The particles have blue photoluminescence, characteristic of ZnS. Systematic variation of reaction temperature and ratios of ZnS precursors to polymer has been used to elucidate the mechanisms of the formation of ?hollow and porous? geometry. As a demonstration of encapsulation within the hollow or porous nanostructures, gold nanoparticles were also to the precursor solution. HRTEM imaging showed that these are encapsulated into the center of the hollow nanospheres, and are distributed throughout the porous nanospheres.