δ-MnO₂ Nanoflowers and Their Reduced Graphene Oxide Nanocomposites for Electromagnetic Interference Shielding

Abstract

The present work is focused on room-temperature reduction by subjecting reduction of an aqueous KMnO4 and KMnO4/graphene oxide (GO) dispersion by Fehling solution B in one step to form δ-MnO2, exhibiting hierarchical nanoflowers and their nanocomposites (δ-MnO2/reduced graphene oxide). This was followed by their characterization by X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), surface area measurements, and DC conductivity. The effect of the concentration of a reducing agent on the morphological evolution of δ-MnO2 has also been proposed. Further, these materials were also investigated for their performance in electromagnetic interference (EMI) shielding efficiency (SE) in the frequency range of 2–8 GHz. These findings showed the highest total shielding efficiency (∼39 dB) of the δ-MnO2/reduced graphene oxide (RGO)-1.0 nanocomposite consisting of 5.5 wt % RGO following reflection as a dominant mechanism. Such excellent performance was attributed to the poor impedance matching between MnO2/RGO, the formation of an interconnected conducting network, and interfacial polarization. It is anticipated that δ-MnO2/RGO nanocomposites synthesized by a simple room-temperature reaction in one step could be promising candidates as lightweight and high-performance EMI shielding materials for multifaceted applications.

Room-Temperature One-Step Synthesis of Silver/Reduced Graphene Oxide Nanocomposites as an Excellent Microwave Absorber

“…The FTIR spectra of Ag show stretching/bending vibrations of O–H (∼3615 cm –1 ), C–H (∼2964 cm –1 ), CO (∼1730 cm –1 ), CC (∼1650 and 1595 cm –1 ), C–O–C (∼1535 and 1455 cm –1 ), C–OH (∼1255, 1121, and 1035 cm –1 ), and C–C/C–O (∼775, 700, and 570 cm –1 ), respectively. , The appearance of these functional groups demonstrated the formation of Ag and its hydrophilic surface (hydroxyl and carboxylic groups) originating from the capping agent used during the synthesis. , It is also noted that the FTIR spectra of Ag/RGO composites showed shifting (3615 → 3625, 1595 → 1570, 1455 → 1435, and 1035 → 1040 cm –1 ), disappearance (2964, 1650, and 1535 cm –1 ), and appearance of new peaks (3740 and 1805 cm –1 : −COOAg group; 1310, 1220, and 960 cm –1 : C–O–Ag group) compared to Ag. These studies also confirmed the reduction of GO and Ag + to RGO , and Ag(0) , as well as Ag/RGO composite , formation, and supported our earlier inference based on XRD.…”

“…The total EMI shielding (SE T ) of a material is attributed to the degree of attenuation of propagating electromagnetic radiation. SE T can be described as a ratio of power (intensity) of transmitted radiation ( P T ) to incident radiation ( P I ). , …”

“…Synthesis of GO was carried out according to the modified Hummer method , and used to synthesis RGO following our earlier work …”

“…Depending on the EMI-shielding mechanism, a shielding material can be fabricated exhibiting moderate conductivity and/or electric or magnetic permeability . In addition, the performance of these nanocomposite materials depends on their particle size, morphology, conductivity, crystallinity, and so forth. − In view of this, nanocomposite-based microwave-absorbing materials have been receiving considerable attention. , …”

Developing a Superhydrophobic Absorption-Dominated Electromagnetic Shielding Material by Building Clustered Fe3O4 Nanoparticles on the Copper-Coated Cellulose Paper

“…The development and prosperity of science and technology have promoted the progress of communication technology, , which has provided convenience in our lives, but the accompanying electromagnetic wave pollution endangers human health and also affects the stable operation of precision instruments. , To reduce the harm caused by electromagnetic wave pollution, various electromagnetic interference (EMI) shielding materials have been developed. − Traditional electromagnetic shielding materials include metal-based materials, conductive filler-filled polymer materials, and composite foam materials. The high conductivity of metal-based materials endows them with excellent electromagnetic shielding performance, but poor processability, high density, and easy corrosivity limit their applications.…”