Tailoring of enhanced interfacial polarization in WO3 nanorods grown over reduced graphene oxide synthesized by a one-step hydrothermal method

Abstract

In the present report, well-defined WO₃ nanorods (NRs) and a rGO–WO₃ composite were successfully synthesized using a one-pot hydrothermal method. The crystal phase, structural morphology, shape, and size of the as-synthesized samples were studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The optical properties of the synthesized samples were investigated by Raman, ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy. Raman spectroscopy and TEM results validate the formation of WO₃ (NRs) on the rGO sheet. The value of the dielectric constant (ε′) of WO₃ NRs and rGO–WO₃ composite is decreased with an increase in frequency. At low frequency (2.5 to 3.5 Hz), the value of ε′ for the rGO–WO₃ composite is greater than that of pure WO₃ NRs. This could be due to the fact that the induced charges follow the ac signal. However, at higher frequency (3.4 to 6.0), the value of ε′ for the rGO–WO₃ composite is less compared to that of the pure WO₃ NRs. The overall decrease in the value of ε′ could be due to the occurrence of a polarization process at the interface of the rGO sheet and WO₃ NRs. Enhanced interfacial polarization in the rGO–WO₃ composite is observed, which may be attributed to the presence of polar functional groups on the rGO sheet. These functional groups trap charge carriers at the interface, resulting in an enhancement of the interfacial polarization. The value of the dielectric modulus is also calculated to further confirm this enhancement. The values of the ac conductivity of the WO₃ NRs and rGO–WO₃ composite were calculated as a function of the frequency. The greater value of the ac conductivity in the rGO–WO₃ composite compared to that of the WO₃ NRs confirms the restoration of the sp² network during the in situ synthesis of the rGO–WO₃ composite, which is well supported by the results obtained by Raman spectroscopy.