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This study demonstrates an all-graphene, additive-free, aqueous-based ink for direct ink writing (DIW) to 3D-print functional aerogels for applications in electronics and electromagnetic interference (EMI) shields. We employ a two-step electrochemical method with a specially designed intercalation step that controls the surface functionality of graphene nanosheets. Comprehensive characterization reveals the significant impact of the physicochemical properties of graphene nanosheets on homogeneity, rheology, electrical conductivity, and EMI shielding effectiveness (SE). A critical observation is that rheology alone is insufficient to predict the printability of two-dimensional particulate systems, while ink homogeneity, dictated by inter-sheet interactions, plays a vital role. By focusing on optimizing intercalation conditions, we find that phosphoric acid treatment is most effective in enhancing both printability and conductivity, achieving an electrical conductivity of 158 S cm−1 and an EMI SE of 50 dB (at 50 μm thickness) without requiring any post-processing reduction. Systematic experiments with varying durations of phosphoric acid intercalation establish that a 10-minutes treatment produces inks with superior 3D printing fidelity. This innovative approach to graphene ink production enables rapid, continuous, and large-scale manufacturing of lightweight, porous materials, avoiding the need for environmentally harmful reductant chemistries or high-temperature processing. Furthermore, eliminating the reduction step in the fabrication process aligns with industrial demands for energy-efficient production processes and high output rates, marking a significant advancement in the field of materials science and offering promising prospects for applying graphene-based inks in advanced manufacturing technologies. [ABSTRACT FROM AUTHOR]

Tailoring the oil/water (O/W) interface is a prerequisite for structuring these two immiscible liquids into prescribed architectures, i.e., liquid‐in‐liquid printing, which is an emerging area in material science. Here, assemblies of graphene oxide (GO) at O/W and air/W interfaces are characterized using a wide range of interfacial rheological techniques. It is shown that the GO nanosheets assemble at the interface, even at extremely low concentrations as low as 0.04 vol%, significantly increasing the elasticity at O/W or air/W interfaces. This is attributed to the combined hydrophobic and hydrophilic nature of GO. Interfacial elastic modulus of ≈1800 mN m−1 is achieved, making GO assemblies exceptional candidates for applications where stabilization of the O/W interface is indispensable. Herein, the super elastic character of the O/W interface with GO assemblies is capitalized for all‐liquid 2D printing in a low viscous oil, underscoring the utility of these all‐liquid systems for electronics, fluidic devices, and controlled release systems. [ABSTRACT FROM AUTHOR]

Electrochemically exfoliated graphene (EEG) with different levels of doping, electrical conductivity, and sheet size was synthesized with a one-step method and the resulting EEGs were incorporated in a poly-(vinyl alcohol) (PVA) matrix via a simple solution-casting approach to prepare high-performance dielectrics. To maximize the EEG potential for making the nanocapacitor structure and minimizing the dielectric loss, we developed an aligned nanofiller structure. The aligned codoped EEG (as nanoelectrodes in the nanocapacitor structure, at 4.0 wt %) in the PVA matrix (as nanodielectric in the nanocapacitor structure) led to a high dielectric constant (203) and low dielectric loss (0.2) in X-band frequency. The chemical and structural characteristics of the nanocomposite account for the enhanced dielectric properties: (i) good dispersion of codoped EEG (nitrogen and sulfur doped) in the polymer matrix resulting in more effective nanocapacitors formation; (ii) enhanced polarization centers in the graphene due to nitrogen/sulfur doping, leading to a higher dielectric constant; (iii) aligned codoped EEG sheets, increasing the effective surface area of the nanocapacitor structure, enhancing the dielectric permittivity of the nanocomposite, and decreasing the dielectric loss; and (iv) functional groups at the surface of EEG acting as conduction barriers and decreasing the possibility of direct contacts of graphene sheets, reducing the dielectric loss. [ABSTRACT FROM AUTHOR]

A new, highly-exfoliated nitrogen-doped graphene is electrochemically synthesized, which enhances the catalytic activity of poly(anilineboronic acid) nanocomposite electrodes for dopamine detection in the presence of excess ascorbic acid. The sensing approach is made up of poly(anilineboronic acid) nanocomposites electrodeposited on the surface of a glassy carbon electrode via in-situ electrochemical polymerization of anilineboronic acid monomers using cyclic voltammetry. A thin layer of DNA-functionalized carbon nanotubes, and nitrogen-doped graphene is coated on the electrode surface prior to electro-polymerization. During the electro-polymerization the π-π stacking and electrostatic interactions between DNA-coated carbon nanostructures and monomers anchors anilineboronic acid monomers on the electrode surface. This molecular anchoring increases electrodeposition of the respective nanocomposites on electrode; thus, greatly enhances the density of boronic acid receptors for dopamine binding. The coordinate covalent bonds between nitrogen atoms of graphene and boron atoms of anilineboronic acid monomers further increase the density of boronic acid groups for target analyte detection. The developed highly-sensitive and highly-selective biosensor is capable of dopamine detection in a wide linear range from 0.02-1μM, along with a detection limit of 14nM, which is a very significant step forward for dopamine detection and paves the way for molecular diagnosis of neurological illnesses such as Parkinson's disease. [ABSTRACT FROM AUTHOR]

A carbon-neutral fuel is desired when it comes to solving the issues associated with climate change. A smart approach would be to develop new materials to produce such fuels, which could be integrated with renewables to improve the efficiency (e.g., solid oxide fuel cells (SOFCs) in smart grid and concentrated solar fuel technologies). In this study, we report the utilization of nonstoichiometric perovskite oxides, Ba2Ca0.66Nb1.34−xFexO6−δ (BCNF) (0 ≤x≤ 1), to split CO2 into carbon, carbon monoxide, and oxygen at elevated temperatures. Powder X-ray diffraction shows the chemical stability of double perovskite-type BCNF after being exposed to 2000 ppm CO2 in Ar at 700 °C. Furthermore, all x≤ 0.66 BCNF members exhibit high chemical stability even under pure CO2 at 700 °C. Scanning electron microscopy coupled with energy dispersive X-ray, Raman spectroscopy, temperature programmed oxidation (TPO) and mass spectroscopy (MS), and DFT analyses confirm the formation of solid carbon upon CO2 exposure, which increases with increasing Fe in BCNF. Mössbauer spectroscopy of the as-prepared BCNF shows the presence of Fe3+, Fe4+ and Fe5+. Upon Ar exposure, the higher valent Fe component is reduced to Fe3+ and subsequent oxidation of Fe3+ seems to promote the CO2 reduction. Overall, these promising results of BCNFs, displaying redox activity at significantly lower temperatures compared to state-of-the-art ceria for CO2 reduction, show great potential for their use in renewable-driven fuel technologies. [ABSTRACT FROM AUTHOR]

Electrochemical regeneration suffers from low regeneration efficiency due to side reactions like oxygen evolution, as well as oxidation of the adsorbent. In this study, electrically conducting nanocomposites, including graphene/SnO2 (G/SnO2) and graphene/Sb-SnO2 (G/Sb-SnO2) were successfully synthesized and characterized using nitrogen adsorption, scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. Thereafter, the adsorption and electrochemical regeneration performance of the nanocomposites were tested using methylene blue as a model contaminant. Compared to bare graphene, the adsorption capacity of the new composites was ≥40% higher, with similar isotherm behavior. The adsorption capacity of G/SnO2 and G/Sb-SnO2 were effectively regenerated in both NaCl and Na2SO4 electrolytes, requiring as little charge as 21 C mg−1 of adsorbate for complete regeneration, compared to >35 C mg−1 for bare graphene. Consecutive loading and anodic electrochemical regeneration cycles of the nanocomposites were carried out in both NaCl and Na2SO4 electrolytes without loss of the nanocomposite, attaining high regeneration efficiencies (ca. 100%). [ABSTRACT FROM AUTHOR]

Nanocomposites of poly(methyl methacrylate)/reduced graphene oxide (PMMA/rGO) without and with decorated magnetite nanoparticles with a segregated structure were prepared using emulsifier-free emulsion polymerization. Various characterization techniques were employed to validate the presence of the nanofillers and the formation of the segregated structure within the nanocomposites. The percolation threshold of the nanocomposites was found to be 0.3 vol %, while a maximum electrical conductivity of 91.2 S·m -1 and electromagnetic interference shielding effectiveness (EMI SE) of 63.2 dB (2.9 mm thickness) were achieved for the PMMA/rGO nanocomposites at a loading of 2.6 vol % rGO. It was also observed that decorating rGO with magnetite nanoparticles (hybrid nanocomposites) led to a tremendous increase in EMI SE. For instance, 1.1 vol % PMMA/rGO nanocomposites indicated an EMI SE of 20.7 dB, while adding 0.5 vol % magnetite nanoparticles enhanced EMI SE to 29.3 dB. The excellent electrical properties obtained for these nanocomposites were ascribed to both superiorities of the segregated conductive structure and magnetic properties of the magnetite nanoparticles.