Oxygen vacancies induced variations in structural, optical and dielectric properties of SnO_2/graphite nanocomposite

摘要

Oxygen vacancies (O.Vs) play vital role in tailoring structural, optical and dielectric properties of nanostructures. Here we prepared SnO_2/graphite (SG) nanocomposite by growing SnO_2 nanoparticles on graphite sheets via hydrothermal method. Enhanced dielectric behavior due to increase in the oxygen vacancies (O.Vs) has been observed in SnO_2/graphite (SG) nanocomposite synthesized. To reveal the underlying origin here, we investigated the structural, morphological, optical, electrochemical and dielectric properties. The growth of SnO_2 NPs on graphite sheets resulted in small-sized NPs (Average size 10.89 ± 0.24 nm) inducing stresses in the structure causing large defect density (O.Vs). The formation of SG nanocomposite has been validated via SEM, TEM, EDX and FTIR. EDX, XPS and Photoluminescence (PL) spectra of SG nanocomposite manifest the presence of large oxygen vacancies (O.Vs). It is revealed that the bandgap of the host material SnO_2 (from ultra violet to the visible window) can be engineered by controlling the assimilation of SnO_2 NPs on GNs. SG nanocomposite exhibits reversible redox process with high anodic and cathodic currents, low internal (0.47 Q) and charge transfer (4.08 Q) resistances, correspondingly, low voltage drop (IR) 0.56 V and high capacitance 54.8 F/g. Variations in dielectric constant (ε), dielectric loss (ε") and conductivity (σ_(ac)) are attributed to the increased concentration of O.Vs and introduction of conductive carbon (graphite). The variations in dielectric properties are attributable to Maxewell-Wagner interfacial polarization and hopping process.