UV–visible photoresponse properties of self-seeded and polymer mediated ZnO flower-like and biconical nanostructures

•Nano-sized ZnO flowers and bicones have been prepared by co-precipitation method.•Optical and structural studies have been done for as-synthesized nanostructures.•Photoconductivity of Nano-sized ZnO flowers and bicones has been investigated.•Photosensitivity in ZnO bicones is higher than that in flowers.•This study explains the role of hydrocarbons on the surface of ZnO nanostructures. Nano-sized zinc oxide (ZnO) flowers and bicones have been prepared by a co-precipitation method using ZnO-seed for flowers and polyethylene glycol (PEG) for bicones to study their photoconductivity under UV–vis illumination. As-synthesized ZnO samples were characterized by various techniques. XRD spectra show that both samples exhibit hexagonal wurtzite structure of ZnO. FESEM images show the morphology of ZnO as that of flower-shaped structures and bicone-shaped structures respectively. UV–visible absorption spectra of both samples have two absorption band edges due to bicone-like structure. ZnO bicones exhibit high photosensitivity as compared to ZnO flowers. However, vacuum is found enhancing the photosensitivity of ZnO bicones as compared to that in air.