Preparation of hierarchical MOF-5 films using morphology controlled ZnO coatings for temperature dependent optical sensors application

Abstract

Morphology and well-organized hierarchical structures are so effective on the properties of materials and their device applications. Herein, the metal organic framework (MOF-5) has been prepared by solvothermal transformation of nanostructured zinc oxides (ZnO) with different morphologies including nanorods (NRs), hollow spheres (HSs) and porous spheres (PSs). The SEM image indicates growth of MOF-5 sheets around the ZnO NRs with straight hexagonal arrangement. X-ray diffraction (XRD) illustrates the good crystal structure of MOF-5 grown around the ZnO NRs with a dominant crystal orientation (220). Moreover, the morphology and crystalline properties of the ZnO NRs remained intact after the deposition of MOF-5 structures. The photoluminescence (PL) properties of the MOF-5/ZnO film show a slight improvement compared to both the ZnO and MOF-5 components, which must originate from the improved transfer of charge carriers between the MOF-5 and ZnO NRs. The sensitivity and detectivity 5.6 and 1.2 times increased by decreasing temperature from 300 K to 285 K. Finally, a metal-semiconductor-metal (MSM) photodetector based on MOF-5/ZnO NRs was prepared. The optoelectrical behavior of the device is determined through current-voltage (I–V) and time-volage (t-V) curves under UV illumination at different temperatures. The MOF-5/ZnO MSM photodetectors are a temperature-dependent photodetector with excellent UV photosensitivity at lower temperatures. The voltage responsivity was 43.64 and 70.73 kV W−1 at 300 K and 285 K, respectively. NEP and detectivity was measured 15.53 pW Hz−1/2 and 2.03 × 108 Hz−1/2w−1 at 285K respectively.