RESUMO
MXenes have garnered significant attention due to their atomically thin two-dimensional structure with metallic electronic properties. However, it has not yet been fully achieved to discover semiconducting MXenes to implement them into gate-tunable electronics such as field-effect transistors and phototransistors. Here, a semiconducting Ti4N3Tx MXene synthesized by using a modified oxygen-assisted molten salt etching method under ambient conditions, is reported. The oxygen-rich synthesis environment significantly enhances the etching reaction rate and selectivity of Al from a Ti4AlN3 MAX phase, resulting in well-delaminated and highly crystalline Ti4N3Tx MXene with minimal defects and high content of F and O, which led to its improved hydrophobicity and thermal stability. Notably, the synthesized Ti4N3Tx MXene exhibited p-type semiconducting characteristics, including gate-tunable electrical conductivity, with a current on-off ratio of 5 × 103 and a hole mobility of â¼0.008 cm2 V-1 s-1 at 243 K. The semiconducting property crucial for thin-film transistor applications is evidently associated with the surface terminations and the partial substitution of oxygen in the nitrogen lattice, as corroborated by density functional theory (DFT) calculations. Furthermore, the synthesized Ti4N3Tx exhibits strong light absorption characteristics and photocurrent generation. These findings highlight the delaminated Ti4N3Tx as an emerging two-dimensional semiconducting material for potential electronic and optoelectronic applications.
RESUMO
Supercritical fluid extrusion (SCFX) processing was used to develop milk protein-based orally self-disintegrating puffs enriched with fruit and dairy by-products, designed specifically to cater to the needs of elderly population having swallowing issues and lactose intolerance. Lactose hydrolyzed skim milk powder (LHSMP) was also added in the formulation to mitigate lactose intolerance while LHSMP was also exploited as a precursor for the polymerization of galactose and lactose to generate galacto-oligosaccharides (GOS) in the puffs. This study for the first time took advantage of the unique features of SCFX processing for in-process GOS formation and enrichment of puffs, achieving GOS contents up to 0.48 g/30 g serving of puffs, thereby making them nutritionally superior and functionally attractive snacks. The estimated nutritional profile revealed that SCFX puffs contained higher levels of protein (16.3 g/30 g), fiber (1.6 g/30 g), phenolics and other valuable nutrients compared to the starch-rich, disintegrating Market Baby puffs.
RESUMO
Multifunctional, flexible, and robust thin films capable of operating in demanding harsh temperature environments are crucial for various cutting-edge applications. This study presents a multifunctional Janus film integrating highly-crystalline Ti3C2Tx MXene and mechanically-robust carbon nanotube (CNT) film through strong hydrogen bonding. The hybrid film not only exhibits high electrical conductivity (4250 S cm-1), but also demonstrates robust mechanical strength and durability in both extremely low and high temperature environments, showing exceptional resistance to thermal shock. This hybrid Janus film of 15 µm thickness reveals remarkable multifunctionality, including efficient electromagnetic shielding effectiveness of 72 dB in X band frequency range, excellent infrared (IR) shielding capability with an average emissivity of 0.09 (a minimal value of 0.02), superior thermal camouflage performance over a wide temperature range (- 1 to 300 °C) achieving a notable reduction in the radiated temperature by 243 °C against a background temperature of 300 °C, and outstanding IR detection capability characterized by a 44% increase in resistance when exposed to 250 W IR radiation. This multifunctional MXene/CNT Janus film offers a feasible solution for electromagnetic shielding and IR shielding/detection under challenging conditions.
RESUMO
Molybdenum carbide MXenes have garnered considerable attention in electronics, energy storage, and catalysis. However, they are prone to oxidative degradation, but the associated mechanisms have not been systematically explored. Therefore, the oxidation mechanisms of Mo-based single-metallic/bimetallic carbide MXenes including Mo2CTx, Mo2TiC2Tx, and Mo2Ti2C3Tx in aqueous suspensions were investigated for the first time in this study. Similar to Ti3C2Tx MXene, Mo-based MXenes were found to undergo oxidative degradation in their aqueous dispersions, leading to the disruption of their crystal structure and subsequent loss of optical and electronic properties. Notably, the Mo2CTx MXene deviated from this typical oxidation behavior as it produced an amorphous product with Mo ions instead of highly crystalline Mo-oxides during oxidation. Similarly, the Mo2TiC2Tx and Mo2Ti2C3Tx MXenes did not yield crystalline Mo-oxides; instead, they produced highly crystalline anatase TiO2 and a Mo-ion-containing amorphous product simultaneously. Furthermore, high-temperature annealing of the oxidized Mo2CTx MXene powder at 800 °C transformed the amorphous Mo-containing product into highly crystalline MoO2 crystals. These findings highlight the unconventional oxidation behavior of Mo-based MXenes, which suggests that the formation of crystalline Mo-based oxides requires a higher activation energy during oxidation than that of TiO2. The unique oxidative pathway reported herein can help elucidate the oxidation mechanisms of Mo-based MXene dispersions and their products. The insights from this study can pave the way for fundamental studies in academia as well as broaden the applications of Mo-based MXenes in various industries.
RESUMO
Heterointerface engineering, which plays a pivotal role in developing advanced microwave-absorbing materials, is employed to design zeolitic imidazolate framework (ZIF)-MXene nanocomposites. The ZIF-MXene composites are prepared by electrostatic self-assembly of negatively charged titanium carbide MXene flakes and positively charged Co-containing ZIF nanomaterials. This approach effectively creates abundant Mott-Schottky heterointerfaces exhibiting a robust built-in electric field (BIEF) effect, as evidenced by experimental and theoretical analyses, leading to a notable attenuation of electromagnetic energy. Systematic manipulation of the BIEF-exhibiting heterointerface, achieved through topological modulation of the ZIF, proficiently alters charge separation, facilitates electron migration, and ultimately enhances polarization relaxation loss, resulting in exceptional electromagnetic wave absorption performance (reflection loss RLmin = -47.35 dB and effective absorption bandwidth fE = 6.32 GHz). The present study demonstrates an innovative model system for elucidating the interfacial polarization mechanisms and pioneers a novel approach to developing functional materials with electromagnetic characteristics through spatial charge engineering.
RESUMO
Wheat powdery mildew possesses a significant threat to wheat crops not only on a global scale but also in the northern region of Pakistan. Recognizing the need for effective measures, the exploration and utilization of exotic germplasm take on critical importance. To address this, a series of trials were made to investigate the response of 30 European (EU) lines, in addition to the local checks (Siran, Atta-Habib (AH) and Ghanimat-e-IBGE) against wheat powdery mildew at the Himalayan region of Pakistan. The study involved field testing from 2018 to 2022 across multiple locations, resulting in 38 different environments (location × year). In addition to field evaluations, molecular genotyping was also performed. The disease was absent on the tested lines during 2018, 2019, and 2020 whereas it ranged from 0 to 100% at Chitral location during 2021, where 100% was observed only for one EU wheat line "Matrix." The disease prevailed only at Gilgit location (0-60% for EU wheat line "F236") and at Nagar location (0-10% for EU wheat lines Substance and Nelson) during the disease season of 2022. Most of the EU wheat lines showed very low ACI values, due to an overall low disease pressure. Matrix showed the maximum ACI (1.54) followed by Ritter (1.25) and Bli_autrichion (0.87), whereas the minimum (0.1) was for Substance, JB_Asano, and KWS_Loft followed by Canon (0.19), all exhibiting partial resistance. The molecular marker-based screening revealed that Pm38 was the most prevalent and detected in 100% of wheat lines followed by Pm39 (60%) and Pm8 (30%). Six wheat lines (20%) possessed all three Pm genes (Pm8, Pm38, and Pm39) concurrently. The variability observed in this study can be utilized in future breeding efforts aimed at developing resistant wheat varieties.
Assuntos
Ascomicetos , Triticum , Triticum/genética , Resistência à Doença/genética , Paquistão , Melhoramento Vegetal , Doenças das Plantas/genéticaRESUMO
This study aimed to prepare a stirred type of fat-free yogurt from enzymatically hydrolyzed potato powder (EHPP) and skimmed milk powder (SMP) without changing its quality and consumer acceptance. The yogurt formulations prepared contained different amount of EHPP 0, 10, 25 and 50% and were stored for 28 days at 4 °C and observed that with increasing substitution ratio, acid production was increased while the viability of lactic acid bacteria was decreased after 28 days of storage at 4 °C. The antioxidant activities (2-Diphenyl-1-picryl-hydrazyl (DPPH) free radical scavenging activity and ferric reducing antioxidant power (FRAP) of the yogurt were increased with increasing EHPP over the storage period. The yogurt formulations having 25 to 50% EHPP has the highest DPPH free radical scavenging activity and FRAP values. Water holding capacity (WHC) was decreased over the storage period with 25% EHPP. The hardness, adhesiveness and gumminess were decreased while no significant change was found in springiness with EHPP addition over the storage period. The rheological analysis showed an elastic behavior of yogurt gels with EHPP supplementation. The sensory results of yogurt containing 25% EHPP have the highest values of taste and acceptance. Yogurt in combination with EHPP and SMP has the higher levels of WHC than non-supplemented yogurt and better stability was recorded during storage. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-023-05737-9.
RESUMO
Pentavalent antimonials continue to be the standard treatment for cutaneous leishmaniasis. But their use is retarded owing to highly-priced, prolonged hospitalization, noxious and poor solubility. Therefore, there is a dire need to characterize new potential compounds possessing anti-leishmanial activity. Topical therapies that are more successful are an essential alternative therapeutic option for the localized self-limiting form of this disease. We tested the herbal-based topical cream Lesh Nat B against Leishmania tropica KWH23 promastigotes and axenic amastigotes in vitro. The anti-leishmanial activity of Lesh Nat B cream was evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay against promastigotes and axenic amastigotes. The results of Lesh Nat B cream were concentration and incubation time-dependent. After 72 h of incubation, Lesh Nat B cream efficiently suppresses the promastigote form of the parasite, followed by 48 h and 24 h. At 72 h, the lowest and highest levels of activity were 37% and 90%. Amastigotes had a minimum activity of 34% and a maximum activity of 78.5%, respectively. This formulation was more cytotoxic against promastigote form than amastigotes form at 72 h incubation periods. All the experiments were carried out in triplicates. Half-maximal inhibitory concentration (IC50) values were determined to be (66 ug/ml) and (70 ug/ml) against promastigote and amastigote forms, respectively. Moreover, 1.63% hemolytic activity was observed in Lesh Nat B cream at (10 µg/ml) while 3% hemolytic activity was observed at (37 µg/ml). It can be concluded that Lesh Nat B cream demonstrated effective Leishmanicidal and less hemolytic activity and can be used as an alternative therapeutic option for the treatment of cutaneous leishmaniasis; however, more studies are expected to justify its effectiveness in treating cutaneous leishmaniasis in both humans and animals.
RESUMO
Fresh-cut Chinese water chestnut (CWC) was treated with high pressure CO2 (HPCD) to inhibit the browning reactions, and the underlying mechanism was investigated in this study. Results showed that HPCD at 2 MPa pressure significantly inhibited lipoxygenase activity and enhanced superoxide dismutase activity, leading to decreased malondialdehyde and H2O2 contents in surface tissue. Moreover, HPCD could reduce total phenols/flavonoids content of surface tissue. Compare with control, homoeriodictyol, hesperetin, and isorhamnetin contents of 2 MPa HPCD-treated samples on day 10 were reduced by 95.72%, 94.31%, and 94.02%, respectively. Furthermore, HPCD treatment enhanced antioxidant enzyme activities, and improved the O2- scavenging ability and reducing power of inner tissue. In conclusion, by regulating ROS and membrane lipid metabolism, HPCD treatment with appropriate pressure could retard the biosynthesis of flavonoids and enzymatic oxidation of phenolic compounds in surface tissue, and enhance antioxidant activity of inner tissue, thereby, delaying the quality deterioration of fresh-cut CWC.
Assuntos
Eleocharis , Espécies Reativas de Oxigênio/metabolismo , Eleocharis/metabolismo , Dióxido de Carbono/metabolismo , Metabolismo dos Lipídeos , Peróxido de Hidrogênio/metabolismo , Antioxidantes/farmacologia , Fenóis/metabolismo , Flavonoides/metabolismoRESUMO
MXenes are an emerging class of 2D materials with unique properties including metallic conductivity, mechanical flexibility, and surface tunability, which ensure their utility for diverse applications. However, the synthesis of MXenes with high crystallinity and atomic stoichiometry in a low-cost process is still challenging because of the difficulty in controlling the oxygen substitute in the precursors and final products of MXenes, which limits their academic understanding and practical applications. Here, a novel cost-effective method is reported to synthesize a highly crystalline and stoichiometric Ti3 C2 Tx MXene with minimum substitutional oxygen impurities by controlling the amount of excess carbon and time of high-energy milling in carbothermal reduction of recycled TiO2 source. The highest used content (2 wt%) of excess-carbon yields TiC with the highest carbon content and minimal oxygen substitutes, which leads to the Ti3 AlC2 MAX phase with improved crystallinity and atomic stoichiometry, and finally Ti3 C2 Tx MXene with the highest electrical conductivity (11738 S cm-1 ) and superior electromagnetic shielding effectiveness. Additionally, the effects of carbon content and substitutional oxygen on the physical properties of TiC and Ti3 AlC2 are elucidated by density-functional-theory calculations. This inexpensive TiO2 -based method of synthesizing high-quality Ti3 C2 Tx MXene can facilitate large-scale production and thus accelerate global research on MXenes.
RESUMO
The wheat yellow rust pathogen has been shown to be diverse and potentially originated in the Himalayan region. Although Himalayan populations of Pakistan, Nepal and Bhutan have been previously compared, little is known about the relative divergence and diversity in Puccinia striiformis populations in the bordering regions of Pakistan and China. To assess the relative diversity and divergence in these regions of Pakistan (Gilgit-Baltistan, Hazara and Azad Jammu Kashmir) and China (Xinjiang, Qinghai, Tibet, Sichuan, Guizhou and Yunnan), a total of 1245 samples were genotyped using 17 microsatellite SSR markers. A clear divergence was observed between the bordering regions of Pakistan and China (FST = 0.28) without any resampling of genetic groups and multilocus genotypes across two sides of the Himalayan mountains. The closest subpopulations across the two countries were Xinjiang and Gilgit-Baltistan (Nei's distance = 0.147), which were close geographically. A very high diversity and recombinant population structure was observed in both populations, though slightly higher in China (Genotypic diversity = 0.970; r¯d = 0.000) than in Pakistan (Genotypic diversity = 0.902; r¯d = 0.065). The distribution of genetic groups and resampling of MLGs revealed more gene flow across Yunnan, Guizhou and Sichuan regions in China, while between Hazara and Azad-Jammu Kashmir in Pakistan. The lack of gene flow between Pakistan and China populations is due to geographical barriers and a large patch of land without wheat. The information on the relative diversity and divergence in different geographical zones of the pathogen center of diversity and neighboring region should be considered in resistant wheat deployment while considering the invasion potential of the pathogen at regional and global contexts.
Assuntos
Basidiomycota , Fluxo Gênico , China , Triticum/genética , Paquistão , Doenças das Plantas/genética , Basidiomycota/genéticaRESUMO
The research was focused on the ability of wheat aphids Sitobion avenae, harboring bacterial secondary symbionts (BSS) Hamiltonella defensa or Regiella insecticola, to withstand exposure to fungal isolates of Beauveria bassiana and Metarhizium brunneum. In comparison to aphids lacking bacterial secondary symbionts, BSS considerably increased the lifespan of wheat aphids exposed to B. bassiana strains (Bb1022, EABb04/01-Tip) and M. brunneum strains (ART 2825 and BIPESCO 5) and also reduced the aphids' mortality. The wheat aphid clones lacking bacterial secondary symbionts were shown to be particularly vulnerable to M. brunneum strain BIPESCO 5. As opposed to wheat aphids carrying bacterial symbionts, fungal pathogens infected the wheat aphids lacking H. defensa and R. insecticola more quickly. When treated with fungal pathogens, bacterial endosymbionts had a favorable effect on the fecundity of their host aphids compared to the aphids lacking these symbionts, but there was no change in fungal sporulation on the deceased aphids. By defending their insect hosts against natural enemies, BSS increase the population of their host society and may have a significant impact on the development of their hosts.
RESUMO
Texture regulation of metal-organic frameworks (MOFs) is essential for controlling their electromagnetic wave (EMW) absorption properties. This review systematically summarizes the recent advancements in texture regulation strategies for MOFs, including etching and exchange of central ions, etching and exchange of ligands, chemically induced self-assembly, and MOF-on-MOF heterostructure design. Additionally, the EMW absorption mechanisms in approaches based on structure-function dependencies, including nano-micro topological engineering, defect engineering, interface engineering, and hybrid engineering, are comprehensively explored. Finally, current challenges and future research orientation are proposed. This review aims to provide new perspectives for designing MOF-derived EMW-absorption materials to achieve essential breakthroughs in mechanistic investigations in this promising field.
Assuntos
Estruturas Metalorgânicas , Micro-Ondas , EngenhariaRESUMO
Scarcity in mining and geo-political direction diverts attention toward critical metal recycling. Gallium (Ga), indium (In) and germanium (Ge) are among the critical metals that consume approximately 80% of world mining in the innovative production of electrical and electronic equipment. The fast obsolescing rate generates a large amount of electronic waste, which is now seen as a secondary reservoir for critical metals. These metal resources need to be dealt with with effective recycling capabilities. Based on solid-phase extraction, magnetic nano-hydrometallurgy is opening a new area of metallic contents recovery in conventional hydrometallurgy. In the present work, polyacrylonitrile (PAN) based electrospun nanofibres were synthesized and carbonized at 800 °C in an inert environment. After surface oxidation, carbon nanofibres were decorated with magnetite particles through co-precipitation. The saturation magnetization value (Ms = 23.6 emu/g) confirms high loading of magnetite particles. The selected critical metal ions are freely present in an aqueous solution at pH 1 to 3; thus, highest removal efficiency was observed at pH 2. Pseudo-second-order kinetics confirm the chemical/charge interaction between sorbent and sorbate ions. Maximum sorption capacity calculated through Langmuir isotherm was 226, 191 and 171 mg/g for Ge(IV), Ga(III) and In(III) metal ions, respectively. The RL value (0 < RL < 1) indicates favourable sorption process. The sorbed target metal ions were collectively eluted using 1 mol/L hydrochloric acid. The preconcentration factor was calculated at 1080 for Ge(IV) and In(III) while 1260 for Ga(III). The method was validated with 5 µg/mL spiked multi-element standards and applied to multiple acid-leached electronic waste samples like PCBs, waste LCD panels and solar panels. Recoveries in the range of 96.2% for Ga(III), 95.6% for In(III) and 97.4% for Ge(IV) in the presence of diverse ions indicate the suitability of the proposed method for target metal ions even in a complex matrix.
Assuntos
Resíduo Eletrônico , Gálio , Nanofibras , Resíduo Eletrônico/análise , Óxido Ferroso-Férrico , Carbono , Índio , Íons , Concentração de Íons de Hidrogênio , AdsorçãoRESUMO
The potential mechanism behind the browning inhibition in fresh-cut water chestnuts (FWC) after eugenol (EUG) treatment was investigated by comparing the difference in browning behavior between surface and inner tissues. EUG treatment was found to inactivate browning-related enzymes and reduce phenolic contents in surface tissue. Molecular docking further confirmed the hydrophobic interactions and hydrogen bonding between EUG and phenylalanine ammonia-lyase (PAL). Moreover, EUG also enhanced reactive oxygen species (ROS)-scavenging enzyme activities, ultimately decreasing the O2 - generation rates. Regarding inner tissue, EUG induced the accumulation of colorless phenolic compounds and increased the antioxidant capacity. In conclusion, 1.5 % EUG exhibited the best inhibitory effect on FWC browning, which partly attribute to the direct inhibitory effects on PAL activity. Furthermore, EUG could also enhance the enzymatic/non-enzymatic antioxidant capacity and alleviate the ROS damage to membranes, thereby, preventing the contact between oxidative enzymes and phenols and indirectly inhibiting the enzymatic browning in FWC.
RESUMO
Peppers are a rich source of bioactive compounds with several health benefits. However, most of the knowledge about these benefits has been obtained through in vitro studies, and less is known about their in vivo health-promoting and stress resistance effects. Therefore, we hypothesized that the intake of apigenin glycosides (XAp-G) from Xiaomila green pepper (Capsicum frutescens) could protect against stress factors and promote longevity of Caenorhabditis elegans. Synchronized worms were treated with XAp-G and the lifespan and stress resistance were examined. XAp-G treatment strongly enhanced the average lifespan of worms by 23.9% compared with control by reducing the reactive oxygen species (ROS) level. Ultrahigh performance liquid chromatography-electrospray ionization-quadrupole time-of-flight mass spectometry analysis showed that Xiaomila pepper (polyamide fraction) contained significant amount of flavone glycosides with m/z 563.14 (apigenin glycosides). Green fluorescent protein fluorescence and real-time polymerase chain reaction analyses showed that XAp-G-treatment could regulate the expression of anti-aging related genes, including daf-2, daf-16, sod-3, hsp-16.2, skn-1, gst-4, gcs-1, jnk-1, and sir-2.1 in C elegans, thereby promoting the translocation of DAF-16 and SKN-1 into the nucleus. However, it could not extend the lifespan of daf-16, skn-1, and sir-2.1 knocked-down mutants. XAp-G treatment significantly reduced ROS under normal and stress conditions (juglone, hydrogen peroxide), and thereby promotes longevity of C elegans via the insulin/insulin-like growth factor-1 signaling pathway.
Assuntos
Proteínas de Caenorhabditis elegans , Capsicum , Animais , Apigenina/farmacologia , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Glicosídeos/farmacologia , Longevidade , Estresse Oxidativo , Espécies Reativas de Oxigênio/metabolismoRESUMO
In this study, capsaicin-glucoside and dihydro-capsaicin-glucoside derived from fresh hot-red pepper were isolated and identified using UPLC-ESI-Q-TOF-MS/PDA. Synchronized worms were treated with capsaicinoid-glucosides (CG), and then lifespan and stress resistance were examined. The 50 µg/ml concentration of CG-intake could effectively protect the Caenorhabditis elegans (C. elegans) against stresses factors including oxidation and heat as well as reactive oxygen species (ROS), thereby enhancing the survival of CG-treated worms under stress. Enhancing stress resistance in CG-treated worms could be due to the increased expressions of stress-related genes in C. elegans such as daf-16, skn-1 and their downstream target genes (sod-3, hsp-16.2, gst-4 and gcs-1). Lifespan study of different C. elegans strains and RT-PCR showed that the CG-mediated lifespan extension was dependent on DAF-16/FOXO and SKN-1/Nrf2 transcription factors. The study is a step forward in exploring the stress resistance and anti-aging properties of this beneficial extract. Thus, this study will be useful in formulating remedies for stresses factors and age associated disorders.
Assuntos
Proteínas de Caenorhabditis elegans , Capsicum , Animais , Caenorhabditis elegans/genética , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Capsaicina/farmacologia , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Glucosídeos , Longevidade , Estresse Oxidativo , Espécies Reativas de Oxigênio/metabolismoRESUMO
In the present study, the browning degree and reducing power of browning products of catechin (CT), epicatechin (EC), caffeic acid (CA), and chlorogenic acid (CGA) in autoxidation and enzymatic oxidation were investigated. Influencing factors were considered, such as pH, substrate species and composition, and eugenol. Results show that polyphenols' autoxidation was intensified in an alkaline environment, but the reducing power was not improved. Products of enzymatic oxidation at a neutral pH have higher reducing power than autoxidation. In enzymatic oxidation, the browning degree of mixed substrates was higher than that of a single polyphenol. The reducing power of flavonoid mixed solution (CT and EC) was higher than those of phenolic acids' (CA and CGA) in autoxidation and enzymatic oxidation. Eugenol activity studies have shown that eugenol could increase autoxidation browning but inhibit enzymatic browning. Activity test and molecular docking results show that eugenol could inhibit tyrosinase.
RESUMO
Two-dimensional graphene is of great interest for electromagnetic interference (EMI) shielding owing to its inherent electrical conductivity, lightweight, and excellent mechanical flexibility even at minor thicknesses. However, the complex synthesis and quality-control difficulties limit its application. In this study, we demonstrate that electrochemically exfoliated graphene (EEG) with post-reduction treatment is a promising candidate for lightweight EMI shielding materials. A facile electrochemical exfoliation approach produces a high-quality multilayer graphene with a high electrical conductivity of â¼600 S cm-1, owing to its low degree of oxidation. The reduction of EEG by three different methods, including chemical, thermal, and microwave treatments, causes the removal of surface functional groups as well as significant changes in the microstructure of the final films. The reduced graphene films by microwaves, which are driven by the improved electrical conductivity and large volume expansion, exhibit an EMI shielding effectiveness of 108 dB at a thickness of 125 µm, one of the largest EMI shielding values ever reported for graphene at comparable thicknesses.
RESUMO
Understanding and preventing oxidative degradation of MXene suspensions is essential for fostering fundamental academic studies and facilitating widespread industrial applications. Owing to their outstanding electrical, electrochemical, optoelectronic, and mechanical properties, MXenes, an emerging class of two-dimensional (2D) nanomaterials, show promising state-of-the-art performances in various applications including electromagnetic interference (EMI) shielding, terahertz shielding, electrochemical energy storage, triboelectric nanogenerators, thermal heaters, light-emitting diodes (LEDs), optoelectronics, and sensors. However, MXene synthesis using harsh chemical etching causes many defects or vacancies on the surface of the synthesized MXene flakes. Defective sites are vulnerable to oxidative degradation reactions with water and/or oxygen, which deteriorate the intrinsic properties of MXenes. In this review, we demonstrate the nature of oxidative degradation of MXenes and highlight the recent advancements in controlling the oxidation kinetics of MXenes with several promising strategic approaches, including careful control of the quality of the parent MAX phase, chemical etching conditions, defect passivation, dispersion medium, storage conditions, and polymer composites.