Study of Optical and Magnetic Properties of Graphene-Wrapped ZnO Nanoparticle Hybrids

Abstract

In this work, we report a one-step method for the preparation of graphene-wrapped zinc oxide (ZnO) nanoparticle (NP) (ZnO@G) hybrids. These hybrids are characterized by transmission electron microscopy, X-ray diffraction, Raman spectroscopy, optical absorption measurements, photoluminescence (PL) emission spectroscopy, and M-H hysteresis measurements. All results reveal that the ZnO NPs are entirely covered with graphene sheets. In the PL spectra, the quenching of the band gap emission and the enhanced green emission serve as evidence of the electron transfer from the ZnO NPs to the graphene layer. The increase of the room-temperature magnetization of the hybrid, compared to pure ZnO NPs, is due to the increasing defect concentration. We suggest a band diagram model that accounts for these observations. We present the simple wet-chemical synthesis procedure to open a new way for the synthesis of NP-graphene hybrid systems having magnetic properties giving the large manifold potential application.

Microwave‐Assisted Synthesis of ZnO–rGO Core–Shell Nanorod Hybrids with Photo‐ and Electro‐Catalytic Activity

“…Comparing the room temperature M – H response of the two samples, ZnO NRs exhibit a coercive field (H c ) of 10.62 mT, a remnant magnetisation of 2.93×10 −10 A m 2 Kg −1 and a saturation magnetisation of 4.34×10 −9 A m 2 Kg −1 at 300 K. By contrast, the ZnO–rGO NRs have a lower coercivity ( H c =4.34 mT) and remanence ( M r =2.29×10 −10 A m 2 Kg −1 ), but the saturation magnetisation for the ZnO–rGO hybrid (5.47×10 −9 A m 2 Kg −1 ) is almost twice that of the bare ZnO NRs. In previous work on ZnO NPs enwrapped in graphene, an increase in the value of M S was observed as the number of defect states in the materials increases . The presence of either oxygen vacancies or zinc vacancies has been documented to be responsible for the ferromagnetism observed in undoped ZnO .…”

“…The peak at 1417 cm −1 is due to sp 2 hybridized C=C in‐plane stretching vibrations. The 877 cm −1 peak can be assigned to the A 1U out‐of‐plane stretching mode from the interlayer sp 2 bonds of graphene . In addition to the expected rGO peaks, a peak is present at 449 cm −1 that likely originates from Zn−O stretching vibrations …”

Graphene Based Functional Hybrids: Design and Technological Applications

“…In addition, electron's movement from ZnO to the layer of graphene is the manifestation to the alleviation of defect emission. On the contrary, movement of charge from graphene to defect state of the given semiconductor causes an enhancement of defect levels contribution [19].…”

“…This synergistic combination has been undergone comprehensive investigation, as it proves to be an excellent candidate of future devices, because of the enhancement in most of the properties like chemical stability, electrical etc. [19].…”

“…Yet, another notable activity is the alleviation, for recombination process of these electrons. In general, activity of the photocatalytic process rises, thereby imparting a constructive role in these properties [19].…”