Synthesis of fluorescent hollow and porous Cu2O nanopolyhedras in the presence of poly(vinyl pyrrolidone)

Single-crystalline hollow and porous cuprous oxide (Cu2O) nanopolyhedras were synthesized using the wet-chemical reduction route method by the reduction of copper-tartrate complex with anhydrous dextrose. Poly(vinyl pyrrolidone) (PVP) was used as a capping agent, which controls the overall morphology and hollowing process. The mechanism responsible for the formation of hollow crystals has been studied in the present analysis. Structural investigations reveal that Cu2O nanopolyhedras can have well-defined hollow interior with porous structure depending on the concentration of PVP. The high-resolution transmission electron microscopy (HRTEM) observations demonstrated that the nanoparticles are composed of small grains coherently growing along certain preferred orientations. Chemical compositions of all the samples have been checked by EDX observation. None of the impurity signal was observed in the present investigation. X-ray photoelectron spectroscopic (XPS) studies indicate the presence of Cu2+ on the surface of the Cu2O polyhedras. UV-visible absorption spectrum has been used to resolve the excitonic or interband transitions of the hollow Cu2O nanopolyhedras. The observed optical band gap of products show blue shift effect compared to the bulk Cu2O [Eg  =  2.17 eV]. In addition, a photoluminescence measurement reveals a strong luminescence peak at 493 nm, arising due to the band edge emission from Γ1+ to the new sub-levels.