Reduction of Graphene Oxide Thin Films by Cobaltocene and Decamethylcobaltocene

Supramolecular Conductive Hydrogels for Tissue Engineering Applications

Owing to their unique attributes, including reversibility, specificity, directionality, and tunability, supramolecular biomaterials have evolved as an excellent alternative to conventional biomaterials like polymers, ceramics, and metals. Supramolecular hydrogels, in particular, have garnered significant interest because their fibrous architecture, high water content, and interconnected 3D network resemble the extracellular matrix to some extent. Consequently, supramolecular hydrogels have been used to develop biomaterials for tissue engineering. Supramolecular conductive hydrogels combine the advantages of supramolecular soft materials with the electrical properties of metals, making them highly relevant for electrogenic tissue engineering. Given the versatile applications of these hydrogels, it is essential to periodically review high-quality research in this area. In this review, we focus on recent advances in supramolecular conductive hydrogels, particularly their applications in tissue engineering. We discuss the conductive components of these hydrogels and highlight notable reports on their use in cardiac, skin, and neural tissue engineering. Additionally, we outline potential future developments in this field.

Carbon Nanomaterial-Based Hydrogels as Scaffolds in Tissue Engineering: A Comprehensive Review

Carbon-based nanomaterials (CBNs) are a category of nanomaterials with various systems based on combinations of sp2 and sp3 hybridized carbon bonds, morphologies, and functional groups. CBNs can exhibit distinguished properties such as high mechanical strength, chemical stability, high electrical conductivity, and biocompatibility. These desirable physicochemical properties have triggered their uses in many fields, including biomedical applications. In this review, we specifically focus on applying CBNs as scaffolds in tissue engineering, a therapeutic approach whereby CBNs can act for the regeneration or replacement of damaged tissue. Here, an overview of the structures and properties of different CBNs will first be provided. We will then discuss state-of-the-art advancements of CBNs and hydrogels as scaffolds for regenerating various types of human tissues. Finally, a perspective of future potentials and challenges in this field will be presented. Since this is a very rapidly growing field, we expect that this review will promote interdisciplinary efforts in developing effective tissue regeneration scaffolds for clinical applications.

l-Ascorbic Acid Treatment of Electrochemical Graphene Nanosheets: Reduction Optimization and Application for De-Icing, Water Uptake Prevention, and Corrosion Resistance

The aeronautical industry demands facile lightweight and low-cost solutions to address climate crisis challenges. Graphene can be a valid candidate to tackle these functionalities, although its upscalability remains difficult to achieve. Consequently, graphene-related materials (GRM) are gathering massive attention as top-down graphite exfoliation processes at the industrial scale are feasible and often employed. In this work, environmentally friendly produced partially oxidized graphene nanosheets (POGNs) reduced by green solvents such as l-Ascorbic Acid to rGNs are proposed to deliver functional coatings based on a glass fiber composite or coated Al2024 T3 for strategic R&D questions in the aeronautical industry, i.e., low energy production, de-icing, and water uptake. In detail, energy efficiency in rGNs production is assessed via response-surface modeling of the powder conductivity, hence proposing an optimized reduction window. De-Icing functionality is verified by measuring the stable electrothermal property of an rGNs based composite over 24 h, and water uptake is elucidated by evaluating electrochemical and corrosion properties. Moreover, a mathematical model is proposed to depict the relation between the layers' sheet resistance and applied rGNs mass per area, which extends the system to other graphene-related materials, conductive two-dimensional materials, and various substrates. To conclude, the proposed system based on rGNs and epoxy paves the way for future multifunctional coatings, able to enhance the resistance of surfaces, such as airplane wings, in a flight harsh environment.

Electrocatalytic CO2 Reduction with a Binuclear Bis-Terpyridine Pyrazole-Bridged Cobalt Complex

A pyrazole-based ligand substituted with terpyridine groups at the 3 and 5 positions has been synthesized to form the dinuclear cobalt complex 1, that electrocatalytically reduces carbon dioxide (CO₂ ) to carbon monoxide (CO) in the presence of Brønsted acids in DMF. Chemical, electrochemical and UV-vis spectro-electrochemical studies under inert atmosphere indicate pairwise reduction processes of complex 1. Infrared spectro-electrochemical studies under CO₂ and CO atmosphere are consistent with a reduced CO-containing dicobalt complex which results from the electroreduction of CO₂ . In the presence of trifluoroethanol (TFE), electrocatalytic studies revealed single-site mechanism with up to 94 % selectivity towards CO formation when 1.47 M TFE were present, at -1.35 V vs. Saturated Calomel Electrode in DMF (0.39 V overpotential). The low faradaic efficiencies obtained (<50 %) are attributed to the generation of CO-containing species formed during the electrocatalytic process, which inhibit the reduction of CO₂ .

Highly Stable Iron- and Carbon-Based Electrodes for Li-Ion Batteries: Negative Fading and Fast Charging within 12 Min

Lithium-ion batteries (LIBs) with high energy density and safety under fast-charging conditions are highly desirable for electric vehicles. However, owing to the growth of Li dendrites, increased temperature at high charging rates, and low specific capacity in commercially available anodes, they cannot meet the market demand. In this study, a facile one-pot electrochemical self-assembly approach has been developed for constructing hybrid electrodes composed of ultrafine Fe₃ O₄ particles on reduced graphene oxide (Fe₃ O₄ @rGO) as anodes for LIBs. The rationally designed Fe₃ O₄ @rGO electrode containing 36 wt % rGO exhibits an increase in specific capacity as cycling progresses, owing to improvements in the active sites, electrochemical kinetics, and catalytic behavior, leading to a high specific capacity of 833 mAh g^-1 and outstanding cycling stability over 2000 cycles with a capacity loss of only 0.127 % per cycle at 5 A g^-1 , enabling the full charging of batteries within 12 min. Furthermore, the origin of this abnormal improvement in the specific capacity (called negative fading), which exceeds the theoretical capacity, is investigated. This study opens up new possibilities for the commercial feasibility of Fe₃ O₄ @rGO anodes in fast-charging LIBs.

Copper Oxide/Functionalized Graphene Hybrid Nanostructures for Room Temperature Gas Sensing Applications

Oxide semiconductors are conventionally used as sensing materials in gas sensors, however, there are limitations on the detection of gases at room temperature (RT). In this work, a hybrid of copper oxide (CuO) with functionalized graphene (rGO) is proposed to achieve gas sensing at RT. The combination of a high surface area and the presence of many functional groups in the CuO/rGO hybrid material makes it highly sensitive for gas absorption and desorption. To prepare the hybrid material, a copper oxide suspension synthesized using a copper acetate precursor is added to a graphene oxide solution during its reduction using ascorbic acid. Material properties of the CuO/rGO hybrid and its drop-casted thin-films are investigated using Raman, FTIR, SEM, TEM, and four-point probe measurement systems. We found that the hybrid material was enriched with oxygen functional groups (OFGs) and defective sites, along with good electrical conductivity (Sheet resistance~1.5 kΩ/□). The fabricated QCM (quartz crystal microbalance) sensor with a thin layer of the CuO/rGO hybrid demonstrated a high sensing response which was twice the response of the rGO-based sensor for CO2 gas at RT. We believe that the CuO/rGO hybrid is highly suitable for existing and future gas sensors used for domestic and industrial safety.

Reversible synthesis of GO: Role of differential bond structure transformation in fine-tuning photodetector response

The controlled modification of graphene's electronic band structure poses serious challenges. In the present work, we study the effect of sp ² cluster size variation on the electronic band gap and photoconductive properties of reduced graphene oxide (RGO). This is achieved by performing reversible functionalization of RGO with oxygen species. The reversible functionalization of RGO results in its partial transformation to graphene oxide (GO) so that the size of the sp ² clusters within the sp ³ matrix varies, thereby affecting the π-π* band structure and photoconductive properties. The study reveals: (1) incremental creation/elimination of oxygenated surface bonds' related energy states within the π-π^* band; (2) customized tuning of the sp ²/sp ³ ratio; (3) the presence/absence of oxygenated states impacts the optical transition processes both from band-to-band and oxygenated states; and (4) the incremental addition/depletion of surface states in a tunable manner directly influences the carrier transport in the photoconductive device. Experiments show a two-stage transformation of RGO electronic properties with changing oxygen functionalities: oxidation (Stage I) and decomposition or erosion (Stage II). Sp ² cluster size variation induced bandgap change was analyzed by Raman and photoluminescence studies, indicating the possibility for photodetection in a specific band encompassing NIR to UV, depending on the sp ²/sp ³ ratio. Energy-dispersive x-ray spectroscopy and Fourier transform infrared studies confirm the surface oxygenation/de-oxygenation during plasma treatment, and XRD confirms partial transformation of RGO to GO and its amorphization at higher plasma exposure times. In addition, the photodetector performance is optimized in terms of carrier generation-recombination and carrier-lattice scattering. Thus, manipulating better photoconductive response is possible through suitable handling of the parameters involved in the plasma treatment process. This is the first study on the influence of the sp ²/sp ³ ratio-induced lattice structure evolution on photodetection.

Durable Antimicrobial Behaviour from Silver-Graphene Coated Medical Textile Composites

Silver nanoparticle (AgNP) and AgNP/reduced graphene oxide (rGO) nanocomposite impregnated medical grade polyviscose textile pads were formed using a facile, surface-mediated wet chemical solution-dipping process, without further annealing. Surfaces were sequentially treated in situ with a sodium borohydride (NaBH4) reducing agent, prior to formation, deposition, and fixation of Ag nanostructures and/or rGO nanosheets throughout porous non-woven (i.e., randomly interwoven) fibrous scaffolds. There was no need for stabilising agent use. The surface morphology of the treated fabrics and the reaction mechanism were characterised by Fourier transform infrared (FTIR) spectra, ultraviolet-visible (UV-Vis) absorption spectra, X-ray diffraction (XRD), Raman spectroscopy, dynamic light scattering (DLS) energy-dispersive X-ray analysis (EDS), and scanning electron microscopic (SEM). XRD and EDS confirmed the presence of pure-phase metallic silver. Variation of reducing agent concentration allowed control over characteristic plasmon absorption of AgNP while SEM imaging, EDS, and DLS confirmed the presence of and dispersion of Ag particles, with smaller agglomerates existing with concurrent rGO use, which also coincided with enhanced AgNP loading. The composites demonstrated potent antimicrobial activity against the clinically relevant gram-negative Escherichia coli (a key causative bacterial agent of healthcare-associated infections; HAIs). The best antibacterial rate achieved for treated substrates was 100% with only a slight decrease (to 90.1%) after 12 equivalent laundering cycles of standard washing. Investigation of silver ion release behaviours through inductively coupled plasmon optical emission spectroscopy (ICP-OES) and laundering durability tests showed that AgNP adhesion was aided by the presence of the rGO host matrix allowing for robust immobilisation of silver nanostructures with relatively high stability, which offered a rapid, convenient, scalable route to conformal NP-decorated and nanocomposite soft matter coatings.

Highly potent radical scavenging-anti-oxidant activity of biologically reduced graphene oxide using Nettle extract as a green bio-genic amines-based reductants source instead of hazardous hydrazine hydrate

Reduced graphene oxide (rGO) is relied upon to be the most promising candidate for high-proficiency. Hydrazine is the most conventional efficient reducing agent that has been frequently used for reduction of graphene oxide, however, it is not environmentally safe due to its toxic nature, causing unsatisfactory defects on the basal plan of GO. Therefore, employing green and efficient reducing agents from natural sources like plant extracts has become the research interest for obtaining high quality reduced graphene oxide sheets in recent years. Here a one-step, easy, cost-effective and green synthesis method based on Nettle leaves' extract has been introduced as an effective reduction method of graphene oxide compared with the toxic and harmful Hydrazine hydrate substance. In this study, GO and rGO were obtained from various methods and characterized by Raman spectroscopy, field emission scanning electron microscope, high-resolution transmission electron microscope (HR-TEM), X-ray diffraction analysis (XRD) and X-ray photon spectroscopy (XPS) analysis. Results of different analytical techniques revealed that the Nettle leaves' extract could successfully reduce GO sheets to high performance reduced graphene oxide with 79% efficiency in comparison with conventional Hydrazine hydrate. On the other side the rGO obtained by Nettle solution could scavenge the free radicals with 70% inhibition capacity at least concentration. Existence of Histamine and Serotonin and many other polyphenols as a part of Nettle leaves composition by following anti-oxidants mechanisms (H donation or electron transfer) promote the anti-oxidant functionality of Nettle leaves. So the highlighted achievement of this paper is to obtain a highly anti-oxidant green reduced graphene oxide with a wide applications i.e medical and polymer composite with UV-shielding activity.

High catalytic activity of Rh nanoparticles generated from cobaltocene and RhCl3 in aqueous solution

Cobalticinium chloride-stabilized RhNPs are very efficient catalysts for hydrolysis of H₃N-BH₃, reduction of 4-NP, hydrogenation of benzene and transfer hydrogenation.

Preparation and microwave absorption performance of a flexible Fe3O4/nanocarbon hybrid buckypaper and its application in composite materials

Graphene oxide (GO) and carbon nanotubes are promising microwave-absorbing materials. Herein, ferroferric oxide (Fe₃O₄)/multiwall carbon nanotube (MWCNT) and Fe₃O₄/GO hybrid buckypapers with excellent flexibility and manoeuvrability were coated on the surface of an epoxy substrate to fabricate microwave-absorbing composites. Fe₃O₄/GO buckypapers show a unique layered structure that differs from the complex network structure of Fe₃O₄/MWCNT buckypapers. Therefore, the Fe₃O₄/GO buckypapers exhibit lower tensile strength and toughness than the Fe₃O₄/MWCNT buckypapers, and the minimum electromagnetic reflection loss of Fe₃O₄/GO buckypapers is higher than that of Fe₃O₄/MWCNT buckypapers. Further, Fe₃O₄/GO buckypapers have a wider effective absorption-frequency band than Fe₃O₄/MWCNT buckypapers at 2.0–18.0 GHz. Although the mechanical properties of epoxy resin composites coated with Fe₃O₄/MWCNT or Fe₃O₄/GO buckypapers show a slight deterioration in comparison with those of the epoxy resin substrate, both buckypapers exhibit improved microwave-absorption performance compared with the epoxy resin substrate.

Flexible nanofilms are used as wave absorbing coatings for fiber/epoxy matrix to prepare lightweight wave-absorbing composites.