Intersheet Distance Research Articles

Interplay of adsorptive properties and dielectric reactivity of graphenes upon edge functionalization

Graphenes have unique physicochemical properties that can be engineered for pollutant adsorption and their dielectric properties can facilitate subsequent microwave regeneration. First, graphenes have the potential for high-level control of oxygen content at the edges of the material without compromising the conjugated electronic structure of the basal plane. Because the basal plane contains lightly functionalized sp2-hybridized carbon atoms while sp3-hybridized ones are on the periphery of the sheets. Edges of graphenes can be oxidized while the basal plane can still be electronically stable with conjugated π-electrons perpendicular to the graphene lattice. For this, graphenes can be oxidized to attain controlled dispersion in water without disrupting the conjugated electron network on the basal plane, which is critical for pollutant adsorption. Graphenes have sheet-like surfaces that form dynamic, porous aggregates in water and can facilitate synthetic organic compound adsorption by the complex interplay of ‘pore’ accessibility and favorable intermolecular interactions. Thus, studying the role of oxidation of graphenes can help unravel the interplay between inter-sheet distance and the adsorption of synthetic organic compounds. Second, the sp2 hybridized basal planes of graphenes have mobile π-electrons that are expedient for rapid dielectric heating, which can be harvested for rapid and efficient microwave regeneration. Fundamental research on graphene chemistry can lead to a paradigm shift in the water treatment industry towards the safe and sustainable deployment of regenerable nano-scale adsorbents. This article presents a perspective on how to approach edge functionalization of graphene with an aspiration to advance their safe and sustainable use in water treatment.

Generation of highly anisotropic physical properties in ferromagnetic thin films controlled by their differently oriented nano-sheets

We fabricated ferromagnetic nano-crystalline thin films of Co, Fe, Co–Fe and Co-rich and Fe-rich, Co–MT and Fe–MT (MT = transition metal), constituted by nano-sheets with a controlled slant. Visualization of these nano-sheets by Scanning Tunneling Microscopy and High-Resolution Transmission Electron Microscopy (HRTEM) showed typically tilt angles ≈56° with respect to the substrate plane, and nano-sheets ≈3.0–4.0 nm thick, ≈30–100 nm wide, and ≈200–300 nm long, with an inter-sheet distance of ≈0.9–1.2 nm, depending on their constitutive elements. Induced by this nano-morphology, these films exhibited large uniaxial magnetic anisotropy in the plane, the easy direction of magnetization being parallel to the longitudinal direction of the nano-sheets. In the as-grown films, typical values of the anisotropy field were between Hk ≈ 48 and 110 kA/m depending on composition. The changes in the nano-morphology caused by thermal treatments, and hence in the anisotropic properties, were also visualized by HRTEM, including chemical analysis at the nano-scale. Some films retained their nano-sheet morphology and increased their anisotropies by up to three times after being heated to at least 500 °C: for example, the thermal treatments produced crystallization processes and the growth of CoV and CoFe magnetic phases, maintaining the nano-sheet morphology. In contrast, other annealed films, Co, Fe, CoZn, CoCu… lost their nano-sheet morphology and hence their anisotropies. This work opens a path of study for these new magnetically anisotropic materials, particularly with respect to the nano-morphological and structural changes related to the increase in magnetic anisotropy.

Structural modification of whey protein nanofibrils by a multiround induction pathway for enhancing the stability of Pickering emulsions

In this study, a new fibrillation method, i.e., a multiround induction pathway, was proposed to modify the highly rigid structure of conventional whey protein nanofibrils and enhance the stability of Pickering emulsions. In contrast to the conventional self-assembly pathway, in which nanofibrils are formed by aggregation of polypeptides or monomers, the multiround induction pathway involves the use of multiple rounds of homologous seeds to induce whey protein nanofibril formation. The structure of nanofibrils formed by multiround induction was considerably different from that of conventionally self-assembled nanofibrils, with a greater or equal number of nanofibrils formed. Over 6 rounds of induction, the intersheet distance within the cross-β-sheet motifs of the nanofibrils increased (from 10.01 Å to 10.70 Å), and the intersheet stacking structure gradually became looser, consequently displaying a thicker morphology with greater height and periodicity. Compared to conventionally self-assembled nanofibrils, nanofibrils with this characteristic structure exhibited 4.04 times higher interfacial adsorption, an 83.24% lower flocculation index, and 61.29% higher emulsion stability. Differences in the emulsification properties of nanofibrils were attributed to multiround induction, which changed the nanofibril structure compared to conventional self-assembly. Some hydrophobic peptides at the β-sheet and α-helix positions were not involved in the construction of cross-β-sheet motifs, which made the nanofibrils more flexible and hydrophobic. These findings suggested that nanofibrils prepared via the multiround induction pathway had unique properties that might be significant for the fabrication of food-grade Pickering emulsions with excellent stability.

Nanomechanical properties of SSTSAA microcrystals are dominated by the inter-sheet packing.

Amyloid fibrils have been associated with human disease for many decades, but it has also become apparent that they play a functional, non-disease-related role in e.g. bacteria and mammals. Moreover, they have been shown to possess interesting mechanical properties that can be harnessed for future man-made applications. Here, the mechanical behaviour of SSTSAA microcrystals has been investigated. The SSTSAA peptide organization in these microcrystals has been related to that in the corresponding amyloid fibrils. Using high-pressure X-ray diffraction experiments, the bulk modulus K, which is the reciprocal of the compressibility β, has been calculated to be 2.48 GPa. This indicates that the fibrils are tightly packed, although the packing of most native globular proteins is even better. It is shown that the value of the bulk modulus is mainly determined by the compression along the c-axis, that relates to the inter-sheet distance in the fibrils. These findings corroborate earlier data obtained by AFM and molecular dynamics simulations that showed that mechanical resistance varies according to the direction of the applied strain, which can be related to packing and hydrogen bond contributions. Pressure experiments provide complementary information to these techniques and help to acquire a full mechanical characterization of biomolecular assemblies. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 2)'.

A conversion strategy to disaggregate asphaltenes via mild hydrotreatment: Theoretical and experimental investigation

Asphaltenes aggregation is a challenging issue for fully upgrading heavy oils, making the development of efficient liquid-phase disaggregation technologies a high priority. We put forward a feasible strategy to disaggregate asphaltenes via mild hydrotreatment (mild HDT). Mild HDT takes place at low temperature and low hydrogen pressure, differing from traditional hydrotreatment. Quantum chemical calculations suggest that the disaggregation mechanism of the agminated asphaltenes was controlled by the hydrogenation degree, and there is an association between the stability of asphaltene dimers and the hydrogenation extent. Furthermore, a mild HDT experiment at 150 °C and 2 MPa shows that the interchain distance and intersheet distance of hydrogenated asphaltenes increase, and the average number of sheets per crystallite decreases to 3.70 from 6.33. Additionally, both molecular dynamics simulations and aggregation tests show that hydrogenated asphaltene molecules are not prone to reaggregation. This research helps to address the issues derived from asphaltene aggregation.

Using Al3+ to Tailor Graphene Oxide Nanochannels: Impact on Membrane Stability and Permeability.

Graphene oxide (GO) membranes, which form from the lamination of GO sheets, attract much attention due to their unique nanochannels. There is much interest in controlling the nanochannel structures and improving the aqueous stability of GO membranes so they can be effectively used in separation and filtration applications. This study employed a simple yet effective method of introducing trivalent aluminum cations to a GO sheet solution through the oxidation of aluminum foil, which modifies the nanochannels in the self-assembled GO membrane by increasing the inter-sheet distance while decreasing intra-sheet spacing. The Al3+ modification resulted in an increase in membrane stability in water, methanol, ethanol, and propanol, yet decreased membrane permeability to water and propanol. These changes were attributed to strong interactions between Al3+ and the membrane oxygenated functional groups, which resulted in an increase in membrane hydrophobicity and a decrease in the intra-sheet spacing as supported by surface tension, contact angle, atomic force microscopy, and X-ray photoelectron spectroscopy measurements. Our approach for forming Al3+ modified GO membranes provides a method for improving the aqueous stability and tailoring the permeation selectivity of GO membranes, which have the potential to be implemented in vapor separation and fuel purification applications.

Vanadium trapped by oblique nano-sheets to preserve the anisotropy in Co–V thin films at high temperature

In this study, oriented nano-sheets generated during the growth of cobalt-rich Co–V and Co–Zn thin films induced a large anisotropy in the magnetic and transport properties. The regular nano-sheets were tilted 52–54 deg. with respect to the substrate plane, ≈ 3.0–4.0 nm thick, ≈ 30–100 nm wide, and ≈ 200–300 nm long, with an inter-sheet distance of ≈ 0.9–1.2 nm. In spite of the different microstructures of the two kinds of samples where the Co–V films were amorphous, whereas the Co–Zn films showed a growth of Zn nanocrystals, the oblique nano-sheet morphology conferred noticeable shape anisotropy to both specimens. This anisotropy resulted in an in-plane uniaxial magnetic anisotropy. The changes in the nano-morphology caused by thermal treatments, and hence in their anisotropic properties, were studied. While the Co–V samples retained or increased their magnetic and transport anisotropies, this anisotropic behavior vanished for the annealed Co–Zn films. High resolution transmission electron microscopy, HRTEM, including chemical analysis at the nano-scale, and the dependence of the anisotropic resistance on temperature allowed to establish the nature and the activation energy spectra of the atomic relaxation processes during heating. These processes displayed a single peak at 1.63 eV for the Co–V and two peaks at 1.67 and 2.0 eV for the Co–Zn. These spectra and their singularities were associated to the changes induced in the nano-morphology of the films by thermal treatments. The Co–V films retained their nano-sheet morphology almost up to 500 ºC; the Co–Zn films lost their nano-sheets at 290 ºC. The thermal stability exhibited by the Co–V films makes them useful for applications in ultra high frequency, optical, magnetostrictive and magneto-electric devices.

Cellulose nanocrystals to modulate the self-assembly of graphene oxide in suspension

Controlling the self-assembly(SA) of cellulose nanocrystals(CNC) and graphene-oxide(GO) sheets at nanoscale is crucial for exploiting properties of both CNC and GO. The SA mechanism of GO, CNC and CNC/GO in suspension is evaluated at different concentrations and mixing ratios. SAXS determine the interparticle distance, interaction and distribution of CNC and GO to resolve the self-assembling mechanism. At lower concentrations, the GO sheets are distributed randomly and separated by a large inter-sheet distance of 83 nm with poor inter-sheet interaction. As increases the GO concentration, the inter-sheet repulsion results in a nematic arrangement with the inter-sheet distance decreasing from 83 to 52 nm. Mixing isotropic and nematic phase of CNC with GO at different CNC/GO ratio from 2 to 50 shows transitions from isotropic, to biphasic and nematic state. In isotropic state, at low CNC/GO ratio, the GO sheets are randomly distributed between the CNC rods which increases the CNC inter-rod distance from 22 to 51 nm. However, at higher CNC/GO ratios, steric repulsion from the large amount of CNC forces the GO sheets to align following the direction of CNC nematic assembly. Understanding SA mechanisms of nanostructures in CNC-GO hybrid will enable to engineer applications for sensor, electronics and diagnostics.

In Situ Crumpling of Gold Nanosheets into Spherical Three-Dimensional Architecture: Probing the Aggregation-Induced Enhancement in Photothermal Properties.

Assembling two-dimensional noble metal nanocrystals into a three-dimensional mesoporous structure is of great value to solve the re-stacking issue for the practical application, which still remains a challenging technique. Herein, we report the one-pot fabrication of gold (Au) nanostructures with a crumpled paper ball-like morphology (Au NCPBs). The success of current work relies on the use of glutathione to crumple the branched Au nanosheets formed during the early stage, into spherical three-dimensional architecture, where the nanosheets are assembled with a mesoporous structure without intimate contact. When working as the agent toward photothermal conversion, the Au NCPBs exhibit enhanced photothermal conversion efficiency (η = 19.9%), as compared to that of flat and wrinkled Au nanosheets. Such an enhancement should be owing to the aggregation-induced effect, where the shortened inter-sheet distance contributes to an increased coupling between the plasmon oscillations/fields of the interacting Au nanosheets. The present study offers a feasible strategy to create spherical architecture of crumpled Au nanosheets and validates their structural advantage in photothermal applications, which could be potentially extended to other metals or alloys.

Insight into the mechanism of asphaltene disaggregation by alkylated treatment: An experimental and theoretical investigation

Mechanism of asphaltene disaggregation by alkylated treatment was revealed experimentally and theoretically. Significant increases both in inter-sheet distance and critical aggregation concentration were clearly observed after alkylation reaction of asphaltenes, indicating that alkylated treatment could well disaggregate asphaltenes and retard them reaggregating, further confirmed by molecular dynamics (MD) simulations. MD results indicate that grafting side-chains with moderate chain lengths, introducing isoalkyl side-chains with larger steric hindrance, or increasing the number of grafted side-chains, is more readily to achieve better disaggregation effect on asphaltene aggregate. Furthermore, a series of non-covalent interactions (NCIs) analyses was performed to elucidate diverse driving forces for disaggregating asphaltenes. Especially via the van der Waals potential analysis, newly developed in recent years, it was found that aside from enhancing exchange-repulsion, the introduction of side-chains brings additional dispersion attraction orthogonal to π-π stacking, thus disrupting the regularity of accumulation of asphaltenes; moreover, through averaged reduced density gradient (aRDG) analysis and adjuvant MD simulations, the role of solvents in affecting the disaggregation behavior was elucidated. This research provides an effective method to disaggregate asphaltenes and contributes to solving the problems caused by asphaltenes aggregation.

High‐Performance Hybrid Photocatalysts: Molecular‐Level Control of the Intersheet Distance and Electronic Coupling between 2D Semiconducting and Metallic Nanosheets: Establishing Design Rules for High‐Performance Hybrid Photocatalysts (Adv. Sci. 7/2021)

In article number 2004530, Seong-Ju Hwang and co-workers investigate the molecular-level control intersheet distance and electronic coupling between 2D graphene/inorganic nanosheets by restacking of a colloidal nanosheet mixture with variable-sized intercalants. The optimal conditions for the efficacy of the conductive nanosheet as a photosensitizer, electron reservoir, charge transport pathway, cocatalyst, and stabilizer can be established with restacked organic-semiconductor–conductor nanohybrids, providing a novel rational design strategy for high-performance hybrid photocatalysts.

Molecular-Level Control of the Intersheet Distance and Electronic Coupling between 2D Semiconducting and Metallic Nanosheets: Establishing Design Rules for High-Performance Hybrid Photocatalysts.

Hybridization with conductive nanospecies has attracted intense research interest as a general effective means to improve the photocatalytic functionalities of nanostructured materials. To establish universal design rules for high‐performance hybrid photocatalysts, correlations between versatile roles of conductive species and interfacial interaction between hybridized species are systematically investigated through fine‐control of intersheet distance between photocatalytically active TiO2 and metallic reduced graphene oxide (rGO)/RuO2 nanosheets. Molecular‐level tailoring of intersheet distance and electronic coupling between 2D nanosheets can be successfully achieved by restacking of colloidal nanosheet mixture with variable‐sized organic intercalants. While the shortest intersheet distance between restacked TiO2 and rGO nanosheets leads to the highest visible‐light‐driven photocatalytic activity, the best UV–vis photocatalyst performance occurs for moderate intersheet spacing. These results highlight the greater sensitivity of photoinduced electronic excitation to the intersheet distance than that of interfacial charge transfer. The rGO nanosheet can function as effective charge transport pathway and cocatalyst within ≈1.7 nm distance from the semiconducting nanosheet, and as efficient stabilizer for hybridized photocatalyst within ≈1.8 nm. The present study underscores that the intercalative restacking of colloidal nanosheet mixture with intercalants enables molecular‐level control of distance between 2D inorganic/graphene nanosheets, which provides a rational design strategy for high‐performance hybrid photocatalysts.

Glutathione Self-Assembles into a Shell of Hydrogen-Bonded Intermolecular Aggregates on "Naked" Silver Nanoparticles.

A detailed understanding of the molecular structure in nanoparticle ligand capping layers is crucial for their efficient incorporation into modern scientific and technological applications. Peptide ligands render the nanoparticles as biocompatible materials. Glutathione, a γ-ECG tripeptide, self-assembles into aggregates on the surface of ligand-free silver nanoparticles through intermolecular hydrogen bonding and forms a few nanometer-thick shells. Two-dimensional nonlinear infrared (2DIR) spectroscopy suggests that aggregates adopt a conformation resembling the β-sheet secondary structure. The shell thickness was evaluated with localized surface plasmon resonance spectroscopy and X-ray photoelectron spectroscopy. The amount of glutathione on the surface was obtained with spectrophotometry of a thiol-reactive probe. Our results suggest that the shell consists of ∼15 stacked molecular layers. These values correspond to the inter-sheet distances, which are significantly shorter than those in amyloid fibrils with relatively bulky side chains, but are comparable to glycine-rich silk fibrils, where the side chains are compact. The tight packing of the glutathione layers can be facilitated by hydrogen-bonded carboxylic acid dimers of glycine and the intermolecular salt bridges between the zwitterionic γ-glutamyl groups. The structure of the glutathione aggregates was studied by 2DIR spectroscopy of the amide-I vibrational modes using 13C isotope labeling of the cysteine carbonyl. Isotope dilution experiments revealed the coupling of modes forming vibrational excitons along the cysteine chain. The coupling along the γ-glutamyl exciton chain was estimated from these values. The obtained coupling strengths are slightly lower than those of native β-sheets, yet they appear large enough to point onto an ordered conformation of the peptides within the aggregate. Analysis of the excitons' anharmonicities and the strength of the transition dipole moments generally is in agreement with these observations.

Anisotropic mechanical response of layered disordered fibrous materials.

Mechanically bonded fabrics account for a significant portion of nonwoven products, and serve many niche areas of nonwoven manufacturing. Such fabrics are characterized by layers of disordered fibrous webs, but we lack an understanding of how such microstructures determine bulk material response. Here we numerically determine the linear shear response of needle-punched fabrics modeled as cross-linked sheets of two-dimensional (2D) Mikado networks. We systematically vary the intra-sheet fiber density, inter-sheet separation distance, and direction of shear, and quantify the macroscopic shear modulus alongside the degree of affinity and energy partition. For shear parallel to the sheets, the response is dominated by intrasheet fibers and follows known trends for 2D Mikado networks. By contrast, shears perpendicular to the sheets induce a softer response dominated by either intrasheet or intersheet fibers depending on a quadratic relation between sheet separation and fiber density. These basic trends are reproduced and elucidated by a simple scaling argument that we provide. We discuss the implications of our findings in the context of real nonwoven fabrics.

Synergistic effects of crystal structure and surface chemistry of stacked graphene-oxide membranes on the water-permeation mechanism

Stacked graphene-oxide (GO) membranes have been reported to have promising potential for desalination. One key issue in the development of such membranes is understanding the atomistic water-permeation mechanism determined by the highly variable nature of GO (including membrane morphology, surface chemistry, osmotic pressure, and surface area). To clearly understand this variability, not only individual but also synergistic effects, i.e., the nonlinear cumulative effects of membrane properties, should be investigated. Hence, this paper explores how lateral and vertical permeation mechanisms differ with changes in the morphology and surface chemistry, either discretely or simultaneously, using both experiments and simulations. Experiments reveal that the GO water-permeation performance is dominated by the heterogeneous structural and chemical nature of GO. To investigate individual and synergistic effects on water dynamics, we performed molecular-dynamics simulations. The synergistic effects were more marked on the lateral permeation mechanisms than on the vertical mechanism in GO membranes. When the membrane nanochannels had a narrow intersheet distance or no gap overlap, the lateral permeation mechanism was found to be completely different owing to the interplay between these properties.

Brunauer–Emmett–Teller (BET) specific surface area analysis of different graphene materials: A comparison to their structural regularity and electrical properties

Graphene has obtained a great interest both in research and industries due to its potential and promising physical, electrical and mechanical properties. While it has been widely researched for advanced applications, its fundamental properties are still being explored and have to be well understood. The physical properties such as specific surface area (SSA), inter-sheet distance (d-spacing) and Raman spectroscopy data for graphene derivatives are closely related to each other, and this work focused on establishing the correlation between these critical factors with respect to their electrical conductivities. Different graphitic materials f(graphene oxide (GO), reduced graphene oxides (rGO), functionalised graphene oxide (frGO) and graphene nanoplatelets (GNP)) were taken in to account to elaborate the underlying mechanisms between extrinsic SSA and other physical parameters, such as intrinsic electrical conductivity. It has been analytically observed that SSA has a direct relationship with d-spacing and defect density of the graphene materials and thus their electrical conductivity highly depends on how large their SSA is the largest the SSA, the highest the electrical conductivity. Materials that poorly reduced were identified to be having low SSA and a higher level of discrepancies. Among different reducing agents used, hydroiodic reduced graphene oxide found to be having larger SSA as 670.98 m2 g−1 and higher electrical conductivity up to 103.3 S cm−1.

How Flexibility of the Nanoscale Solvophobic Confining Material Promotes Capillary Evaporation of Ionic Liquids

Capillary evaporation of ionic liquids in nanoscale confinement is an important process relevant to self-assembly and energy storage applications. Most studies focus on understanding ionic liquids confined by rigid materials, but the flexibility of the materials can also impact the thermodynamics of confinement. In this work, we investigate the effects of flexibility of confining surfaces on the structure and free energy underlying capillary evaporation of the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]) in nanoscale solvophobic confinements. We employ indirect umbrella sampling to estimate the free energy profiles for [EMIM][BF4] between both rigid and flexible square confining surfaces at several intersheet separations. The analysis of these free energy profiles shows that capillary evaporation of [EMIM][BF4] is enhanced by the introduction of flexibility to the confining sheets. We examine the number density profiles for the ionic species in the confinement, which show distinct structural layering for different separations. By additionally characterizing the orientational ordering of cations in confinement, we quantify significant structural changes that occur as the intersheet distance is reduced and as capillary evaporation occurs at fixed confinement. We find that flexibility of the confining material also impacts the structural changes that occur as the ionic liquid evaporates from the intersheet region.

Controlling inter-sheet-distance in reduced graphene oxide electrodes for highly sensitive electrochemical impedimetric sensing of myoglobin

In order to improve the sensitivity of electrochemical impedance spectroscopy (EIS)-based biosensors, a number of structuring strategies to promote enlarging the electroactive surface area have been recently proposed. However, these approaches have not been applicable to graphene-based electrodes especially due to their ultrathin film thickness (usually <10 nm) and incompatibility with top-down based structuring methods. To challenge this limitation, in this work, we presented a novel means to increase the electroactive surface area and the sensitivity of graphene electrode-based EIS biosensors with obviation of any extrinsic structuring method, such as patterning or pore generation. Instead, graphene oxide (GO) nanosheets functionalized with octadecylamine (ODA) groups to alter the inter-sheet spacing were synthesized and assembled to stacked films. Then, GO films were thermally reduced to form the roughened surface to maximize the electroactive surface area and sensing sensitivity. As a proof of concept demonstration, the sensing performances of rGO electrodes with differential inter-sheet distance were assessed via EIS measurements for the detection of myoglobin (Mb), a representative biomarker of acute myocardial infarction. Taken together, the deliberate control of the extent of interlayer alkylation of stacked GO nanosheets proved to be an effective strategy to produce rGO electrodes with significantly enhanced and/or controlled surface area, giving rise to a remarkably high sensing performance with the detection limit of 2.37 pM concentration of Mb. The presented strategy is simple yet powerful and widely applicable to various types of target molecules, it is therefore expected to provide general platform for biomedical and environmental sensors.

Graphene-Based Assemblies As Electrode Materials for Supercapacitors

Reduced graphene oxide (RGO) based electrochemical double-layer capacitors (EDLC), have been extensively studied as good power capability can be achieved but they suffer from low capacitances (~100-150 F/g), as the reduced graphene sheets partially restack through π- π interactions limiting the resulting adsorption active surface area.[1] To avoid this restacking different paths have been followed in the literature: using graphene aerogels or expanded graphene structures.[2] In this latter case, an intercalate or pillar is used to space out the graphene layers and recover active surface area. Different nature of pillars or intercalates such as carbon nanotubes, carbon blacks, diamine, aromatic, metallic ions or big macrocyles have been described.[2,3] The results, that will be presented, depict the researches devoted to the development and study of graphene based expanded assemblies designed to be tested as electrode materials for supercapacitors. The material development involves the bridging of graphene oxide derived sheets using alkyl diamine as linkers (Fig. 1a).[3] The production of graphene galleries of height matching that of different alkyl chain length pillars was evidenced, notably with XRD (Fig. 1b). The purpose of this design was to enhance the specific capacitance by limiting graphene sheet restacking and optimizing the inter-sheet distance (d-spacing) or pore size with respect to the ion size, as was previously evidenced with other carbon materials.[4] These materials (named RPs) have been tested electrochemically with various tetraalkylammonium tetrafluoroborate salts in acetonitrile. This approach resulted in adsorption active surface area tuning, yielding clear evidence of the electrolytic ions entering the inter-layer galleries. Indeed only ions with diameter smaller than the d-spacing access the inter-layer galleries.[5a] Ex-situ solid-state NMR analysis were performed to further demonstrate the ionic species adsorption at the material surface. Further optimization dealing with pillar amount or nature and material density tuning showed the high interest of this re-aggregation limitation method, as gravimetric and volumetric capacitances 4 times higher than that of RGO (230 F/g and 210 F/cm3 respectively) have been achieved (Fig. 1c).[5b] Figure 1: a) Scheme differentiating reduced graphene oxide RGO and pillared graphene structures; b) XRD diffractograms obtained for pillared graphene prepared diamines with different chain lengths (5, 6 and 8 C atoms); c) Volumetric capacitance and power capability tests obtained on a pillared material compared to RGO.

About the Crystallization of Abiotic Coded Matter.

The crystallization of digitally encoded polyurethanes was studied by electron diffraction. A series of oligomers with different primary structures was analyzed in this work. They all form hydrogen-bonding-directed lamellar single crystals with a base-centered orthorhombic unit cell. Although crystal morphology was the same in all cases, the digital coding of the oligomers has a small influence on the intersheet distance in the crystals. The crystal lattices allow calculation of the volume occupied by one basic information unit, which is in the range 148-188 Å3. Interestingly, this volume is about 3× smaller than that occupied by a coded nucleotide in a DNA double helix. Furthermore, crystallization of blends of oligourethanes with different coded primary structures was investigated. Oligomers with drastically different monomer compositions form structures that are not cocrystals but more probably segregated crystals containing distinct domains of different composition.