Functionalized carbon microfibers (biomass-derived) ornamented by Bi2S3 nanoparticles: an investigation on their microwave, magnetic, and optical characteristics

Microporous Cobalt Ferrite with Bio-Carbon Loosely Decorated to Construct Multi-Functional Composite for Dye Adsorption, Anti-Bacteria and Electromagnetic Protection

Currently, facing electromagnetic protection requirement under complex aqueous environments, the bacterial reproduction and organic dye corrosion may affect the composition and micro-structures of absorbers to weaken their electromagnetic properties. To address such problems, herein, a series of CoFe2O4@BCNPs (cobalt ferrite @ bio-carbon nanoparticles) composites are synthesized via co-hydrothermal and calcining process. The coupling of magnetic cobalt ferrite and dielectric bio-carbon derived from Apium can endow the composite multiple absorption mechanisms and matched impedance for effective microwave absorption, attaining a bandwidth of 8.12 GHz at 2.36 mm and an intensity of -49.85 dB at 3.0 mm. Due to the ROS (reactive oxygen species) stimulation ability and heavy metal ions of cobalt ferrite, the composite realizes an excellent antibacterial efficiency of 99% against Gram negative bacteria of Escherichia coli. Moreover, the loose porous layer of surface stacked bio-carbon can promote the adsorption of methylene blue for subsequent eliminating, a high removal rate of 90.37% for organic dye can be also achieved. This paper offers a new insight for rational design of composite's component and micro-structure to construct multi-functional microwave absorber for satisfying the electromagnetic protection demand in complicated environments.

Plasma-assisted doping of pyrolyzed corn husk strengthened by MoS2/polyethersulfone for fascinating microwave absorbing/shielding and energy saving properties

To address the ever-increasing electromagnetic pollution, numerous efforts have been made. In this case, biomass-derived materials as green, affordable, lightweight, capable, and sustainable microwave-absorbing materials have become a research hotspot; meanwhile, transition metal-based microwave absorbers and sulfide structures as polarizable electromagnetic absorbers have intrigued researchers. Alternatively, plasma treatment as a novel strategy has been applied in different fields, and doping strategies are in the spotlight to modify the microwave-absorbing features of materials. Thus, herein, corn husk biomass was pyrolyzed and doped with N via plasma treatment, followed by coating with MoS2 nanoflowers to promote its microwave-absorbing characteristics. More interestingly, the influence of absorbing media was carefully evaluated using polyethersulfone (PES) and polyethylene (PE) as polymeric matrices. The as-developed MoS2/N-doped pyrolyzed corn husk (PCH) demonstrated outstanding electromagnetic interference shielding effectiveness (EMISE) based on its absorption covering the entire K-band frequency with ≈100% shielding, a fascinating reflection loss (RL) of -95.32 dB at 21.28 GHz, and outstanding efficient bandwidth (EBW) of 7.61 GHz (RL ≤ -10) with a thickness of only 0.45 mm. It is noteworthy that the energy-saving features of the final composites were precisely investigated using an infrared (IR) absorption approach.

Plasma Engineering toward Improving the Microwave-Absorbing/Shielding Feature of a Biomass-Derived Material

During the past decade, ever-increasing electromagnetic pollution has excited a global concern. A sustainable resource, facile experimental scenario, fascinating reflection loss (RL), and broad efficient bandwidth are the substantial factors that intrigue researchers. This research led to the achievement of a brilliant microwave-absorbing material by treating pampas as biomass. The carbon-based microfibers attained by biowaste were treated by plasma under diverse environments to amplify their microwave-absorbing features. Moreover, a pyrolysis scenario was performed to compare the results. The reductive processes were performed by H2 plasma and carbonization. However, the CO2 plasma was performed to regulate the heteroatoms and defects. Interestingly, polystyrene (PS) was applied as a microwave-absorbing matrix. The aromatic rings existing in the absorbing medium establish electrostatic interactions, elevating interfacial polarization, and physical characteristics of PS augment the practical applications of the final product. The manipulated biomasses were characterized by Raman, X-ray diffraction, energy-dispersive spectroscopy, field emission scanning electron microscopy, and diffuse reflection spectroscopy analyses. Eventually, the microwave-absorbing features were estimated by a vector network analyzer. The plasma-treated pampas under H2/Ar blended with PS gained a maximum RL of -90.65 dB at 8.79 GHz and an efficient bandwidth (RL ≤ -10 dB) of 4.24 GHz with a thickness of 3.20 mm; meanwhile, plasma treatment under CO2 led to a maximum RL of 97.99 dB at 14.92 GHz and an efficient bandwidth of 7.74 GHz with a 2.05 mm thickness. Particularly, the biomass plasmolyzed under Ar covered the entire X and Ku bands with a thickness of 2.10 mm. Notably, total shielding efficiencies of the treated bioinspired materials were up to ≈99%, desirable for practical applications.

Microwave absorbing characteristics of porphyrin derivates: a loop of conjugated structure

Microwave absorbing architectures have gained a great deal of attention due to their widespread application in diverse fields, especially in refining electromagnetic pollution. The aim of this study is to investigate the metamaterial characteristics of porphyrin derivatives as conjugated rings in the microwave region and evaluate the influence of electron-withdrawing and donating groups on microwave attenuating performance. Initially, an innovative microwave curing procedure was applied to synthesize the derivates; following that, the phenyl, aniline, and nitrophenyl-coupled structures were identified by XRD, FTIR, FESEM, and DRS analyses. The optical features illustrated that the characteristic band gap of the conjugated loops is obtained and that the optical performance can be manipulated by coupling the functional groups. Eventually, the achieved results demonstrated that the best microwave absorbing performance is related to aniline-coupled porphyrin with a maximum reflection loss (RL) value of -104.93 dB at 10.09 GHz with 2.80 mm in thickness attaining an efficient bandwidth (EB) (RL ≤ 10 dB) higher than the X-band. Noticeably, polyethylene (PE) was applied as an absorbing matrix presenting a meaningful idea for the development of practical microwave absorbers as a new generation of electromagnetic refining and stealth materials. The presented research provides precious inspiration to tailor novel microwave absorbing materials with metamaterial capability to promote their microwave absorbing performance.

Biomass-Derived Carbon Materials in Heterogeneous Catalysis: A Step towards Sustainable Future

Biomass-derived carbons are emerging materials with a wide range of catalytic properties, such as large surface area and porosity, which make them ideal candidates to be used as heterogeneous catalysts and catalytic supports. Their unique physical and chemical properties, such as their tunable surface, chemical inertness, and hydrophobicity, along with being environmentally friendly and cost effective, give them an edge over other catalysts. The biomass-derived carbon materials are compatible with a wide range of reactions including organic transformations, electrocatalytic reactions, and photocatalytic reactions. This review discusses the uses of materials produced from biomass in the realm of heterogeneous catalysis, highlighting the different types of carbon materials derived from biomass that are potential catalysts, and the importance and unique properties of heterogeneous catalysts with different preparation methods are summarized. Furthermore, this review article presents the relevant work carried out in recent years where unique biomass-derived materials are used as heterogeneous catalysts and their contribution to the field of catalysis. The challenges and potential prospects of heterogeneous catalysis are also discussed.

Preparation of self-healing hydrogel toward improving electromagnetic interference shielding and energy efficiency

In this study, a self-healing hydrogel was prepared that is transparent to visible (Vis) light while absorbing ultraviolet (UV), infrared (IR), and microwave. The optothermal features of the hydrogel were explored by monitoring temperature using an IR thermometer under an IR source. The hydrogel was synthesized using sodium tetraborate decahydrate (borax) and polyvinyl alcohol (PVA) as raw materials based on a facile thermal route. More significantly, graphene oxide (GO) and graphite-like carbon nitride (g-C3N4) nanostructures as well as carbon microsphere (CMS) were applied as guests to more dissect their influence on the microwave and optical characteristics. The morphology of the fillers was evaluated using field emission scanning electron microscopy (FE-SEM). Fourier transform infrared (FTIR) attested that the chemical functional groups of the hydrogel have been formed and the result of diffuse reflection spectroscopy (DRS) confirmed that the hydrogel absorbs UV while is transparent in Vis light. The achieved result implied that the hydrogel acts as an essential IR absorber due to its functional groups desirable for energy efficiency and harvesting. Interestingly, the achieved results have testified that the self-healing hydrogels had the proper self-healing efficiency and self-healing time. Eventually, microwave absorbing properties and shielding efficiency of the hydrogel, hydrogel/GO, g-C3N4, or CMS were investigated, demonstrating the salient microwave characteristics, originated from the established ionic conductive networks and dipole polarizations. The efficient bandwidth of the hydrogel was as wide as 3.5 GHz with a thickness of 0.65 mm meanwhile its maximum reflection loss was 75.10 dB at 14.50 GHz with 4.55 mm in thickness. Particularly, the hydrogel illustrated total shielding efficiency (SET) > 10 dB from 1.19 to 18 and > 20 dB from 4.37 to 18 GHz with 10.00 mm in thickness. The results open new windows toward improving the shielding and energy efficiency using practical ways.

Functionalized carbonized monarch butterfly wing scales (FCBW) ornamented by β-Co(OH)2 nanoparticles: an investigation on its microwave, magnetic, and optical characteristics

In this research, a bioinspired carbon structure was applied as a novel, unique, green, affordable, light weight, thin, and broadband microwave absorbing material. Briefly, the monarch butterfly wing scales were pyrolyzed and then CBWs were functionalized using oxidative treatments, following that they were ornamented by hexagonal β-Co(OH)₂ nanoparticles to improve their microwave absorbing features based on an innovative complementary method by combining sonochemistry and hydrothermal routes. Noticeably, the polyacrylonitrile (PAN) was used as a practical medium to fabricate the microwave absorbers developing an integrated structure and augmenting the relaxation loss mechanism. Various analyses were applied to identify the prepared samples including x-ray powder diffraction, diffuse reflection spectroscopy, Fourier transform infrared, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), vibrating sample magnetometer, and vector network analyzer. The net-like morphology of FCBWs were fully coated by the hierarchical hexagonal β-Co(OH)₂ nanoparticles. FCBW illustrated a saturation magnetization of 0.06 emu g^-1 originated from its defects, distortions, dislocations, unique morphology, as well as folding, developing localized magnetic moments. Noticeably, inserting FCBWs narrow the energy bandgap of β-Co(OH)₂ nanoparticles, amplifying their light absorption and polarizability, desirable for the microwave attenuation. As revealed, FCBW/β-Co(OH)₂/PAN nanocomposite gained strong reflection loss (RL) of 68.41 at 9.08 GHz, while FCBW/PAN achieved broadband efficient bandwidth as wide as 7.97 GHz (RL > 10 dB) with a thickness of 2.00 mm. More significantly, β-Co(OH)₂/PAN nanocomposites demonstrated salient efficient bandwidth of 3.62 GHz (RL > 20 dB) with only 2.50 mm in thickness. Noteworthy, the eye-catching microwave absorptions were obtained by only filler loading of 10 Wt%. The remarkable microwave absorbing properties of the samples were generated from their microwave absorbing mechanisms which were scrupulously dissected. More significantly, the negative imaginary parts were obtained, originated from the produced secondary fields.