Synthesis and characterization of MgAl2O4-graphene nanocomposites for study of their dielectric properties and photocatalytic activity

Abstract

Magnesium aluminate MgAl2O4 is one of the eminent members of spinel group that has registered itself as a material exhibiting a broad range of application based diverse characteristics. Nanoparticles of this spinel class are renowned for their dielectric, optical and photocatalytic activities. Composites of this material are considered to be more efficient for tuning of its physical characteristics to use in various fields. Composites of MgAl2O4 with graphene have been successfully synthesized using simple, easy, environmental friendly and cost effective Sol-gel method. Composites of MgAl2O4 with graphene were prepared by the ultra-sonication approach in which ortho-xylene was used as a dispersive medium. The composition of graphene was varied as 1%, 2%, 3%, 4% and 5%. The synthesized samples were characterized through versatile techniques such as XRD, SEM, FTIR, Dielectric analyser and UV-visible spectroscopy. XRD results verified the phase formation of MgAl2O4 nanoparticles and its composites with graphene. With increased concentration of graphene a prominent peak appeared at 26.5˚ which represents the graphitic plane (002). Crystallite size approximated by Debye‟s Scherer formula was 13 ± 2 nm. SEM images depicted the complete anchoring of MgAl2O4 nanoparticles over the graphene sheets. The particles size attained through SEM was 17 – 28 ± 2 nm. FTIR indicated the presence of bands at 695 cm-1, 526 cm-1, 1420 cm-1 and 1459 cm-1 which corresponds to MgO4, AlO6, C-O and C=C groups. Giga hertz dielectric properties were extracted for entire samples, considerable enhancement was noticed in all such properties with addition of graphene. Dielectric constant value for pristine MgAl2O4 nanoparticles was 6.1 which increased to 478 for 5% graphene based composite. In order to compute the band gap of samples uv visible spectroscopy was used. Band gap calculated for pure MgAl2O4 nanoparticles was 5.3 eV which reduced to 5.24 eV, 5.16 eV, 5.05 eV and 4.29 eV for 1%, 2%, 3%, 4% and 5% loaded graphene composites. Moreover, photocatalytic degradation performance was studied through uv visible spectrogram. The results showed that degradation efficiency increased from 75 % for pristine MgAl2O4 to 89 % when graphene was added to form the composite indicating that such composites are potential candidates for industrial waste water treatment.