In-situ synthesis and optical properties of CNO-ZnO nanocomposite

• Facile one-step solution route synthesis of CNO-ZnO nanocomposite.
• To investigate structure-property relationship at the nanoscale.
• Presence of ZnO in the composite enhance the visible-light absorption.
• Covalent interaction between CNO and ZnO modifies the effective recombination of excited electron-hole process.

Carbon onions offer a good model system to study the optoelectronic properties of graphitic nanoparticles in zero dimension as they are favored over the planar graphite-like structures and energetically stable. Defect induced optical absorbance and luminescence behavior of as prepared CNOs has been investigated at room temperature considering their potential applications in optoelectronic devices. Most interestingly, these CNOs show exceptional excitation wavelength independent strong luminescence property over a range of the ultraviolet spectrum. By incorporating ZnO into CNO we observed sharp characteristic emissive peaks at 306 and 608 nm which arises due to the defect-mediated luminescence from localized metal oxide surface states by the photo-generated recombination of electron-hole pairs. The interaction between CNO and ZnO is through the functional groups on CNO which act as anchoring sites and nucleation points, leading to the bond formation between them.