Low Temperature Ferromagnetic Behavior of Graphene Oxide (GO) and Molybdenum Disulphide (MoS2) Hybrid Nanocomposite.

GO:MoS2 nanoparticle (NP) hybrid nanocomposite is prepared and studied structural, electronic and magnetic properties using X-ray diffraction, field emission scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and superconducting quantum-interface-device measurements. MoS2-NP exhibited diamagnetic characteristic but GO:MoS2-NP hybrid nanocomposite exhibited low temperature ferromagnetic characteristics. Field cooling and Zero field cooling characteristic exhibited divergence below ~280 K with increasing magnetic field. The saturation magnetic moment and coercivity of GO:MoS2-NP hybrid nanocomposite is higher than GO that could be useful for low temperature magneticities and energy storage device application.

Electronic, Electrical, and Magnetic Behavioral Change of SiO2-NP-Decorated MWCNTs.

Silicon-oxide-nanoparticle (SiO2-NP) heteroatoms were decorated/deposited onto multiwall carbon nanotube (MWCNT) surface to tune the properties of MWCNTs for electronic and magnetic applications. To achieve this objective, SiO2-NPs and MWCNTs were prepared and suspended together into toluene and heated at <100 °C for the formation of MWCNTs/SiO2-NP nanocomposites. A change in the microstructure, electronic, electrical, and magnetic behaviors of MWCNT nanocomposites decorated/deposited with silicon content was investigated using different techniques, viz., scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and X-ray photoelectron spectroscopy for structural, compositional, and electronic structure, while current-voltage was used for electrical properties and field-dependent magnetization and electron spin resonance techniques were used for magnetic properties. The results indicated that SiO2-NPs adhered onto MWCNTs, resulting in variation in the material conductivity with the Si-NP content. The coercivity of MWCNT nanocomposites adhered with 1.5 atom % Si-NPs (H C@40 K = 689 Oe) is higher than that of those adhered with 5.75 atom % Si-NPs (H C@40 K = 357 Oe). In general, the results provide information about the possibilities of tuning the electronic, electrical, and magnetic properties of MWCNTs by adherence of SiO2-NPs onto them. This tuning of material properties could be useful for different electronic and magnetic device applications.

Electronic structure and magnetic behaviors of exfoliated MoS2 nanosheets.

The correlation of electronic structure and magnetic behaviors of layered molybdenum disulfide (MoS2) nanosheets, mechanically exfoliated from pristine hexagonal crystal (2H-MoS2) have been studied. Raman spectra show the energy difference (ΔE) between two Raman peaks A 1g and [Formula: see text] was about 20.2 cm-1, indicating the formation of mono-/bi-layered MoS 2 nanosheets as obtained after mechanical exfoliation from pristine 2H-MoS 2 . The absence of the reflection peak (0 0 2) in x-ray diffraction patterns confirms the formation of few-layered and mono-/bi-layered MoS 2 nanosheets with reduced thickness. Mo 3d and S 2p  XPS core level peaks shifted to higher energy with the reduction of the number of layers in exfoliated MoS2. As the number of layers decreased, valence band maximum position increased from 1.11 eV (pristine MoS2) to 1.57 eV (mono-/bi-layered MoS 2 nanosheets), whereas the surface work function (Ф) reduced from 4.85 eV (pristine MoS2) to 4.47 eV (mono-/bi-layered MoS2 nanosheets), as observed from UPS (He-I) measurements. UPS (He-II) spectra, as well as VB-PES spectra of mono-/bi-layered MoS 2 nanosheets, exhibits an enhanced valence band density of states (DOS) of S 3p -derived states near Fermi level (E f). Mo L II-edge and S K-edge x-ray absorption near edge structure spectra of mono-/bi-layered MoS 2 nanosheets show the splitting of different peaks that cause a noticeable change in their band structure. Magnetic M-H hysteresis loops measurement clearly demonstrates the increase of room temperature ferromagnetism from pristine to mono-/bi-layer MoS2, due to the existence of defects ('S'-vacancies or defects at the grain boundaries region) and the increase of DOS.

Conduction Mechanisms in Polyvinyl Alcohol: CdS/CdS:Cu Nanoparticle Hybrid Nanocomposites.

The electrical conduction mechanisms were investigated for the CdS and Cu-doped CdS (CdS:Cu) nanoparticles embedded in polyvinyl alcohol (PVA) (PVA/CdS and PVA/CdS:Cu) nanocomposites; synthesized by the chemical Sol Gel method on indium tin-oxide (ITO) substrate. X-ray diffraction pattern results show that the PVA/CdS nanocomposite is hawleyite-sturcture and PVA/CdS:Cu nanocomposites show greenockite-hawelyite mixed structure. The sizes of CdS and CdS:Cu nanoparticles were estimated from transmission electron microscopy (TEM) images and are ≈4 nm and ≈10 nm respectively; which were formed inside the PVA polymer layer. The devices were fabricated with Ag and ITO as electrodes with PVA/CdS and PVA/CdS:Cu nanocomposites as an active layers. The current-voltage (I-V ) relationships measurements shows the nature is extended memrisitve features for both PVA/CdS and PVA/CdS:Cu nanocomposites. The ION/IOFF ratios are enhanced and become more prominent in case of PVA/CdS:Cu nanocomposites device. The resistive switching characteristic show Schottky, Trapped-charge limited current (TCLC) and Space charge limited conduction (SCLC) mechanisms in Ag/PVA/CdS/ITO device; whereas Schottky, Ohmic, TCLC and SCLC were observed in Ag/PVA/CdS:Cu/ITO device.