The present work reports fabrication of trilaminar core–shell composites of Fe3O4@C@PANI as efficient lightweight electromagnetic wave absorber by facile hydrothermal method and subsequent high-temperature calcination followed by its encapsulation through oxidative polymerization of aniline. The prepared composite structure was characterized by FTIR, XRD, XPS, TEM, HRTEM, and SQUID. The measurement of reflection loss, complex permittivity, complex permeability, and total shielding efficiency of the composites has been carried out in the frequency range of 2–8 GHz. Our findings showed lowest reflection loss (∼33 dB) in composite comprised of Fe3O4@C:aniline (1:9 wt/wt) corresponding to shielding efficiency predominantly due to absorption (∼47 dB) than reflection (∼15 dB). Such high value of shielding efficiency could be ascribed to the presence of dual interfaces and dielectric–magnetic integration in Fe3O4@C@PANI. In all probability, higher dielectric loss through interface polarization and relaxation effects in Fe3O4@C@PANI could also contribute toward superior microwave absorption ability of Fe3O4@C@PANI compared to Fe3O4@C and Fe3O4/PANI binary composites. This is likely to enhance the interfacial polarization, natural resonance, dielectric polarization, trapping of EM waves by internal reflection, and effective anisotropy energy in Fe3O4@C@PANI.

polyaniline hollow microsphere (pnHM)/fe 3 o 4 magnetic nanocomposites have been synthesized by a novel strategy and characterized. Subsequently, PNHM/Fe 3 o 4-40 (Fe 3 o 4 content: 40 wt.%) was used as an adsorbent for the removal of arsenic (As) from the contaminated water. Our investigations showed 98-99% removal of As(III) and As(V) in the presence of PNHM/Fe 3 o 4-40 following pseudo-second-order kinetics (R 2 > 0.97) and equilibrium isotherm data fitting well with Freundlich isotherm (R 2 > 0.98). The maximum adsorption capacity of As(III) and As(V) correspond to 28.27 and 83.08 mg g −1 , respectively. A probable adsorption mechanism based on X-ray photoelectron spectroscopy analysis was also proposed involving monodentate-mononuclear/bidentate-binuclear As-Fe complex formation via legend exchange. In contrast to NO 3 − and SO 4 2− ions, the presence of PO 4 3− and CO 3 2− co-ions in contaminated water showed decrease in the adsorption capacity of As(III) due to the competitive adsorption. The regeneration and reusability studies of spent PNHM/Fe 3 o 4-40 adsorbent showed ~83% of As(III) removal in the third adsorption cycle. PNHM/Fe 3 o 4-40 was also found to be very effective in the removal of arsenic (<10 μg L −1) from naturally arsenic-contaminated groundwater sample. Arsenic (As) remains one of the major sources of toxic pollutant in groundwater, affecting millions of people throughout the world. It associated into groundwater from several sources of natural and anthropogenic origins. The chronic exposure of arsenic contaminants in water beyond the World Health Organization (WHO) permissible limit (10 µg L −1) results in a serious toxicological and carcinogenic effect on human health 1. It is also widely established that the presence of arsenite [As(III)] in water is more toxic and soluble compared to arsenate [As(V)] 2,3. As a result, several technologies namely, co-precipitation, coagulation, oxidation, ion exchange, adsorption, membrane separation, etc. have been adopted for the treatment of such contaminated water 4,5. However, many conventional and other approaches are not cost-effective and environmental friendly towards arsenic removal selectivity. For example, the precipitation of iron coagulation is cost-effective; however, it generates huge amounts of sludge, leading to secondary pollution problems 6. Similarly, membrane separation exhibits high efficiency but involves high operational cost 6. In this regard, the removal of toxic pollutants from water through adsorption has been receiving considerable attention due to its sludge-free operation, cost-effectiveness, high efficiency/selectivity, ease of use, and reusability facilities 7. Several nanoparticles, such as activated carbon, carbon nanotubes, graphene, manganese oxide, zinc oxide, titanium oxide, and ferric oxides emerged as effective nanoadsorbents give better performance compared to other conventional adsorbents in removal of arsenic, phosphate, selenium and nitrite anions, and other heavy metals from drinking water 8-13. In this co...

The electromagnetic shielding materials effectively shield the interference of electromagnetic waves and reduce its various harmful effects on wildlife and human beings. Therefore, electromagnetic shielding has attracted much attention to...

According to the available literature, hydrophobic nature of graphene restricts the fabrication of its polymer nanocomposites in aqueous medium without its modification or through in situ synthesis from graphite oxide. In view of this, present work reports on fabrication of nanocomposites of poly(vinyl alcohol) filled with selectively reduced graphite oxide (SRGO) in aqueous medium. FTIR study establishes the formation of nanocomposites through enhanced intermolecular hydrogen bonded network between −OH (PVA) and surplus −OH functionalities of graphene sheet in SRGO in comparison to that derived from PVA/ graphite oxide (GO). PVA/SRGO-0.2 nanocomposite showed maximum improvements in tensile strength (127%), elongation at break (25%) and thermal stability (45 °C) compared to neat PVA. This is ascribed to better dispersion and presence of extensive intermolecular hydrogen bonding between PVA and SRGO. All PVA/SRGO nanocompopsites exhibited relatively higher glass transition temperature (T g ), melting temperature (T m ), and crystallization temperature (T c ). The formation of conducting network also accounts for good electromagnetic shielding efficiency (EMI SE) of PVA/SRGO nanocomposites in 2−8 GHz frequency range with respect to PVA. It is anticipated, this novel approach could be further extended in synthesizing many other SRGO-filled polar polymer nanocomposites in aqueous medium for their diverse applications.

Tuning of the defect is critical for specific application of a material worth exploring and researching. In view of this, additional defects have been incorporated in single-walled carbon nanotubes (SWCNTs) by subjecting them to camphor-mediated combustion and characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and electron paramagnetic resonance. Subsequently, we compared electromagnetic interference (EMI) shielding performance of SWCNTs vis-à-vis multiwalled carbon nanotube (MWCNT)-filled polystyrene (PS) nanocomposites. Interestingly, induced defects in SWCNT played a contrasting role with respect to MWCNT in their performance as EMI shielding materials. These findings have been correlated with the aspect ratio and percolation threshold of CNTs as well as dc conductivity of PS/CNT nanocomposites in the light of electromagnetic theory.

Additional defects inclusion in the form of rehybridization, twisted kinks, and fragmentation has been achieved in MWCNTs fabricated through a unique camphor mediated combustion and sublimation approach. The significant defects induced in MWCNTs through combustion of camphor are unambiguously evidenced by their superior fluorescence quenching efficiency.

The widespread usage of miniaturized electronic gadgets today faces stiff reliability obstacles from factors like stray electromagnetic signals. The challenge is to design lightweight shielding materials that combine small volume...

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