Template free synthesis of mesoporous CuO nano architects for field emission applications.

Cupric oxide mesospheres composed of its nanoparticles have been synthesized by a simple template free chemical route at different temperatures. Thermal aging followed by higher temperature (350 degrees C, 6 hours) annealing on these architects transformed them into hollow mesospheres consisting of sharp needle like structures with high aspect ratio (- 10(3)). A detailed analysis of field emission scanning electron microscopy confirmed a uniform registry of the prepared nanostructures. High resolution transmission electron microscopy showed that the as-grown mesospheres have hollow inner cavity with a thin outer shell. X-ray photoelectron spectroscopic analysis showed no obvious changes in the chemical composition of the nanostructures after annealing, confirming that the elements in the final products were in the proper oxidation states. Electron emission under electric field was investigated from these interesting structures. It was found that both of these nanostructures showed electron emission, but emission performance of the hollow mesospheres consisting of nanoneedles exhibited excellent performance with turn-on field as low as 2.8 V/microm and high enhancement factor (beta) - 5537.