We employed molecular dynamics (MD) simulations coupled with umbrella sampling to explore the thermodynamics governing the exfoliation of a single graphene layer from a graphitic substrate in five different solvents such as dimethylacetamide (DMA), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), cyclohexane (CHX), and water. The substrate was modeled as a stack of three identical graphene layers with the graphene sheet undergoing exfoliation positioned on top of this stack. The initial configurations for each umbrella simulation were generated through steered MD simulations carried out along two distinct coordinates: one parallel and the other perpendicular to the graphene layers. Our analyses revealed a uniform wetting behavior for both the nanosheet and the graphitic substrate in all of the tested solvents. Consistent with experimental observations, the steered simulations confirmed that exfoliation is more favorable along the parallel direction than along the perpendicular one. All non-water solvents exhibit comparable effectiveness in the exfoliation of graphene. The calculated free energies of these solvents in parallel exfoliation consistently fell within the range of 90-100 kJ/mol/nm2. In perpendicular exfoliation, however, the corresponding energies converge to lower values. This difference is attributed to the nonequilibrium nature of the perpendicular exfoliation, primarily caused by the great steering velocity of the graphene sheet immediately after detachment from the substrate. This rapid motion of the nanosheet along the perpendicular coordinate results in an elevated system energy and heating.

Photodetectors are of great interest in several technological applications thanks to their capability to convert an optical signal into an electrical one through light-matter interactions. In particular, broadband photodetectors are used in multiple applications such as environmental monitoring, imaging, fire detection, and astronomical observations. We present a two-dimensional photodiode heterojunction based on reduced graphene oxide (rGO) deposited on an n-type Silicon substrate. We report on the electro-optical properties of the device that have been measured in dark and light conditions into a spectral range from UV to IR. The room temperature current-voltage (I-V) measurements of rGO/n-Si photodetector exhibits a reverse saturation current linearly dependent on the light power. The main figures of merit of the photodetector such as linearity and responsivity have been evaluated and compared with the recent progress obtained substituting the rGO with a graphene single layer (Gr) on the similar n-Si substrate. The photoconductive properties and analysis of the two devices are presented and discussed. Finally, the experimental results demonstrate the feasibility of the rGO/n-Si and Gr/n-Si device to detect light from UV to IR light, nominating graphene-based heterojunction as a novel candidate for the realization of new broadband photodetectors.

In the last decade, reducing the dimensionality of materials to few atomic layers thickness has allowed exploring new physical properties and functionalities otherwise absent out of the two dimensional limit. In this regime, interfaces and interlayers play a crucial role. Here, we investigate their influence on the electronic properties and structural quality of ultrathin CrO on Pt(1 1 1), in presence of a multidomain graphene intralayer. Specifically, by combining Low-Energy Electron Diffraction, X-ray Photoelectron Spectroscopy and X-ray Absorption Spectroscopy, we confirm the growth of high-quality ultrathin CrO on bare Pt, with sharp surface reconstructions, proper stoichiometry and good electronic quality. Once a multidomain graphene intralayer is included at the metal/oxide interface, the CrO maintained its correct stoichiometry and a comparable electronic quality, even at the very first monolayers, despite the partially lost of the morphological long-range order. These results show how ultrathin CrO films are slightly affected by the interfacial epitaxial quality from the electronic point of view, making them potential candidates for graphene-integrated heterostructures.

The use of a novel three-dimensional graphene structure allows circumventing the limitations of the two-dimensional nature of graphene and its application in hydrogen absorption. Here we investigate hydrogen -bonding on monolayer graphene conformally grown via the epitaxial growth method on the (0001) face of a porousified 4H-SiC wafer. Hydrogen absorption is studied via Thermal Desorption Spectroscopy (TDS), exposing the samples to either atomic (D) or molecular (D2) deuterium. The graphene growth temperature, hydrogen exposure temperature, and the morphology of the structure are investigated and related to their effect on hydrogen absorption. The three-dimensional graphene structures chemically bind atomic deuterium when exposed to D2. This is the first report of such an event in unfunctionalized graphene-based materials and implies the presence of a catalytic splitting mechanism. It is further shown that the three-dimensional dendritic structure of the porous material temporarily retains the desorbed molecules and causes delayed emission. The capability of chemisorbing atoms after a catalytic splitting of hydrogen, coupled to its large surface-to-volume ratio, make these structures a promising substrate for hydrogen storage devices.

Defects in the lattice are of primal importance to tune graphene chemical, thermal and electronic properties. Electron-beam irradiation is an easy method to induce defects in graphene following pre-designed patterns, but no systematic study of the time evolution of the resulting defects is available. In this paper, the change over time of defected sites created in graphene with low-energy (<= 20 keV) electron irradiation is studied both experimentally via micro-Raman spectroscopy for a period of 6 x 103 h and through molecular dynamics simulations. During the first 10 h, the structural defects are stable at the highest density value. Subsequently, the crystal partially reconstructs, eventually reaching a stable, less defected condition after more than one month. The simulations allow the rationalization of the processes at the atomic level and confirm that the irradiation induces composite clusters of defects of different nature rather than well-defined nanoholes as in the case of high-energy electrons. The presented results identify the timescale of the defects stability, thus establishing the operability timespan of engineerable defect-rich graphene devices with applications in nanoelectronics. Moreover, long-lasting chemical reactivity of the defective graphene is pointed out. This property can be exploited to functionalize graphene for sensing and energy storage applications.

Supercapacitors are playing a very relevant role in many applications due to their capability to supply high power density and long durability. However, there is a growing demand to increase their energy density, in gravimetric and volumetric basis. There are different strategies to increase supercapacitor performance by improving the active materials used in the electrodes, the type of electrolyte used or even the configuration employed in the cell. In this work, a combination of these strategies is presented with the use of different active materials, electrolytes and symmetric vs asymmetric configuration. The supercapacitor with asymmetric configuration using the graphene-doped carbon xerogel in the negative electrode and the manganese oxide in the positive electrode, along with the use of Na+-form Aquivion electrolyte membrane as solid electrolyte, seems to be a promising combination to obtain a substantial enhancement of both gravimetric and volumetric capacitance. Furthermore, the device presents great stability in a wide operational voltage window from 0 to 1.8 V and with a neutral pH polymer electrolyte which contributes to improve the performance, safety and long cycle life of the device.

The Coronavirus Disease 2019 (COVID-19) pandemic has led to collaboration between nanotechnology scientists, industry stakeholders, and clinicians to develop solutions for diagnostics, prevention, and treatment of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infections. Nanomaterials, including carbon-based materials (CBM) such as graphene and carbon nanotubes, have been studied for their potential in viral research. CBM unique effects on microorganisms, immune interaction, and sensitivity in diagnostics have made them a promising subject of SARS-CoV-2 research. This review discusses the interaction of CBM with SARS-CoV-2 and their applicability, including CBM physical and chemical properties, the known interactions between CBM and viral components, and the proposed prevention, treatment, and diagnostics uses.

The problem of water scarcity is already serious and risks becoming dramatic in terms of human health as well as environmental safety. Recovery of freshwater by means of eco-friendly technologies is an urgent matter. Membrane distillation (MD) is an accredited green operation for water purification, but a viable and sustainable solution to the problem needs to be concerned with every step of the process, including managed amounts of materials, membrane fabrication procedures, and cleaning practices. Once it is established that MD technology is sustainable, a good strategy would also be concerned with the choice of managing low amounts of functional materials for membrane manufacturing. These materials are to be rearranged in interfaces so as to generate nanoenvironments wherein local events, conceived to be crucial for the success and sustainability of the separation, can take place without endangering the ecosystem. In this work, discrete and random supramolecular complexes based on smart poly(N-isopropyl acrylamide) (PNIPAM) mixed hydrogels with aliquots of ZrO(OC-CH-CO) (MIL-140) and graphene have been produced on a polyvinylidene fluoride (PVDF) sublayer and have been proven to enhance the performance of PVDF membranes for MD operations. Two-dimensional materials have been adhered to the membrane surface through combined wet solvent (WS) and layer-by-layer (LbL) spray deposition without requiring further subnanometer-scale size adjustment. The creation of a dual responsive nanoenvironment has enabled the cooperative events needed for water purification. According to the MD's rules, a permanent hydrophobic state of the hydrogels together with a great ability of 2D materials to assist water vapor diffusion through the membranes has been targeted. The chance to switch the density of charge at the membrane-aqueous solution interface has further allowed for the choice of greener and more efficient self-cleaning procedures with a full recovery of the permeation properties of the engineered membranes. The experimental evidence of this work confirms the suitability of the proposed approach to obtain distinct effects on a future production of reusable water from hypersaline streams under somewhat soft working conditions and in full respect to environmental sustainability.

Intelligent composite materials and devices are attracting a great interest owing to their potential impact on various future life applications. To meet the growing demand for multifunctional materials, the development and validation of visible sensing behavior is highly desirable, but the development of a single multifunctional wearable sensing material still remains a challenge to be achieved. To reach this goal, here we present a wearable intelligent fabric with piezoresistivity and mechanoluminescence ability based on a layer-structured graphene-based conductive cotton fabric and SrAlO:Eu, Dy/polyurethane foamed coating. The presence of the foamed coating structure endows the flexible composite fabric with a controllable positive/negative piezoresistivity (gauge factor from -2.5 to 17) and a bright mechanoluminescence ability that can be used in the darkness without additional batteries. Three-dimensional chromaticity diagrams have also been developed as advanced tools to quantitatively assess the luminescence, whose lightness, during the bending cycles, is highly repeatable with value in the range from ~25 to ~55. The multifunctional layered composite sensor provides multiple output signals which can be accurately recognized and assigned to independent triggering events, opening up new opportunities in advanced wearable devices based on commercial fabrics.

Design and development of thermoregulating polymeric composite laminates occurs for application in the field of wearable prosthetics, in which the reduction of thermal discomfort is a key-issue to improve the life quality of amputee patients. They are based on an acrylic thermoset resin modified with phase change microcapsules (PCMs) and a fabric of polyamide (Perlon®) fibers coated with reduced graphene oxide (rGO). Morphological, thermal, mechanical and heat transfer properties of the resulting composite laminates are investigated. The presence of the rGO coating on the fabrics facilitates heat conduction, and increase the composite thermal diffusivity of about 70%, as compared with pristine acrylic resin and non-modified perlon fabric. The PCMs reduce about 50% the temperature increase of the composite laminate when subject to external heating. Moreover, the combination of rGO and PCMs enhances the thermal storage potential of the PCMs, contributing to further reducing the temperature fluctuations of the composite laminates. Graphical Abstract: [Figure not available: see fulltext.]

Low-temperature chemical vapor deposition (LT-CVD) of graphene using liquid aromatic hydrocarbons holds technological advantages over conventional growth from methane. However, the nature of decomposition mechanisms of such precursors and their effectiveness in a LT-CVD process is still debated. We investigate by means of density functional theory adsorption energies and decomposition first steps on Cu(111) of single-ring aromatic hydrocarbons, such as benzene and toluene. Our results confirm the stronger stability with respect to methane of aromatic adsorbates, due to exchange of London dispersion forces with Cu surface; however, toluene exhibits improved bindings with respect to benzene. The adsorption energy slightly improves if additional methyl groups are substituted in benzene, as in o-xylene and 1,2,3-trimethylbenzene. Among decomposition reactions, dehydrogenation of the methyl group in toluene is energetically more favored (1.20 eV) than that of methane (1.52 eV) or aromatic C-rings (1.67 eV and 1.72 eV for benzene and toluene), while demethylation of toluene remains negligible due to the prohibitive energy barrier (2.49 eV). Methyl dehydrogenation in toluene leads to the abundant formation of adsorbed benzyl radicals onto Cu in an almost parallel-to-surface configu-ration, as active species for graphene nucleation. Toluene (and to a lesser extent o-xylene and 1,2,3-trimethyl-benzene) should be thus preferred to benzene in LT-CVD of graphene.

Graphene quantum dots (GQDs) are biocompatible nanoparticles employed in biomedical field, thanks to their size and photophysical properties. GQDs have shown the capability to cross biological barriers, including the blood-brain barrier, which makes them promising agents for brain diseases therapy. It has been shown that surface-functionalized GQDs enhance membrane fluidity and intracellular uptake, exerting a synergistic effect with antitumor drugs at subtherapeutic doses. Here, we tested GQDs effects in combination with chemotherapeutic agents doxorubicin and temozolomide, on a complex 3D spheroid model of glioblastoma. We observed that the capability of GQDs to absorb and convert near-infrared light into heat is a key factor in membrane permeability enhancement on 3D model. This non-invasive therapeutic strategy named photothermal therapy (PTT), combined to chemotherapy at subtherapeutic doses, significantly increased the effect of antitumor drugs by reducing tumor growth and viability. Furthermore, the increase in membrane permeability due to GQDs-mediated PTT enhanced the release of reactive oxygen species with strong migration of the immune system towards irradiated cancer spheroids. Our data indicate that the increase in membrane permeability can enhance the efficacy of antitumor drugs at subtherapeutic doses against glioblastoma, reducing side effects, and directing immune response, ultimately improving quality of life for patients.

Respiratory tract infections represent the main cause of death from infectious diseases worldwide. SARS-CoV-2 infection (i.e. COVID-19) added to the existing global burden of respiratory tract infections, including tuberculosis. Among nanomaterials for fabric functionalization, graphene, in combination with hydrophobic molecules such as phytochemicals, represents a promising low-cost alternative to antibiotics. In this work, we used graphene and curcumin to create fabric coatings on cotton and polyester for the production of personal protective equipment resistant to infective agents. These coatings ensure the trapping of microorganisms via interaction with SARS-CoV-2 or mycobacteria surface and inhibit microbial infections.

We use synchrotron radiation-induced core level photoemission spectroscopy to investigate the influence of vacancies, produced by ion bombardment, on monolayer raphene/Ni(111) exposed to CO at pressures ranging from ultra-high vacuum (1010 mbar) up to near ambient (5.6 mbar) conditions. CO intercalates at a rate which is comparable to the one observed in absence of defects and reacts via the Boudouard reaction producing additional carbon atoms and CO2. While the former attach to the graphene layer and extend it over areas previously covered by carbide, the CO2 molecules bind to the graphene vacancies forming epoxy-like bonds across them, thus mending the defects. The soformed complexes give rise to a peak at 533.4 eV which persists upon evacuating the vacuum chamber at room temperature and which we assign to a covalently bonded species containing C and O.

The direct chemical vapor deposition (CVD) of graphene on industrially preferred semiconductor (like Si wafers) or dielectric substrates has been considered a valid alternative to directly incorporate graphene into electronic devices, thus preventing the common transfer process of the as-grown film which inevitably induce residual contamination and mechanical defects.1 Usually, the thermal CVD synthesis of graphene on Si substrates is realized with methane at high temperature (>900°C), although the low diffusivity of carbon species and the strong carbon solubility on Si which induce unavoidable formation of SiC buffer layers severely hamper an efficient growth.2 Though several strategies have been adopted to overcome such limitations, few studies are focused on aromatic hydrocarbons as possible carbon precursors. 3 In this work, we investigate at the molecular-level the first decomposition steps of toluene and possible recombi- nation pathways of as-formed active species onto the reconstructed Si(100)-c(4x2) surface through density functional theory (DFT) calculations with van der Waals corrections (DFT-D3). First, toluene molecules can chemisorb with sev- eral configurations onto the Si surface by addition reactions.4 We found the most stable configuration (the aromatic ring forming four sigma bonds with two adjacent Si dimers) with adsorption energy of -1.39 eV which is higher than the value reported in,4 mainly due to the inclusion of the DFT-D3 corrections in this work. Then, the minimum energy pathway (MEP) and transition state (TS) of chemical reactions (decomposition and recombination steps) were investi- gated through the climbing-image nudged elastic band (CI-NEB) method. The dehydrogenation of the methyl group of toluene were found the most likely early decomposition path with an energy barrier of 1.4 eV. However, the formation of CH3 radicals is strongly hampered by the much higher energy required for demethylation. Finally, we investigated the formation of anthracene (three connected phenyl rings) as one of the possible stable graphene nuclei for which we found a strong adsorption energy of -2.43 eV. Such carbon structure was achieved by a recombination of two C7H5 radicals and described by a two-step reaction, as shown in Fig.1. However, the cost to produce anthracene through this pathway is rather high with an energy barrier of at least 2.6 eV which is not beneficial for the low-temperature CVD synthesis of graphene on Si(100). References 1 H. Wang, G. Yu, Direct cvd graphene growth on semiconductors and dielectrics for transfer-free device fabrication, Advanced Materials 28 (25) (2016) 4956-4975. 2 A. Khan, M. R. Habib, C. Jingkun, M. Xu, D. Yang, X. Yu, New insight into the metal-catalyst-free direct chemical vapor deposition growth of graphene on silicon substrates, The Journal of Physical Chemistry C 125 (3) (2021) 1774-1783. 3 Tau O., Prete P., Lovergine N., Submitted to Carbon, 2022. 4 F. Costanzo, C. Sbraccia, P. L. Silvestrelli, F. Ancilotto, Theoretical study of toluene chemisorption on si (100), The Journal of Physical Chemistry B 107 (37) (2003) 10209-10215.

The widely used anti-inflammatory diclofenac (DCF) is one of the pharmaceutical drugs most frequently detected in the environment as it is not fully degraded by conventional water treatment plants. Carbon-based adsorbent nanomaterials are attractive for the treatment of wastewater contaminated by pharmaceuticals, due to their high affinity for organic pollutants, high loading capacity, and the efficient regeneration. To obtain insight at molecular level into factors affecting the adsorption of DCF by carbon nanomaterials, molecular dynamics simulations are carried out considering the pure (pG), hydroxyl- (G-OH) and epoxy- (G-COC) functionalized graphene. Also, a material presenting both functional groups is considered (GOX). DCF is adsorbed spontaneously by all materials, but with different types of interactions: pi-pi and CH-pi interactions are present for pG and G-COC, while also hydrogen bonds are formed in the case of G-OH and GOX. While DCF is adsorbed on pG it can translate, this is not the case for the other materials. Spontaneous aggregation leading to the formation to small clusters is observed in all cases when several DCF molecules are present in the system. Free energy calculations give Delta G(ads) which are close to experimental data and follow the order pG < G-COC similar to G-OH. While for pG adsorption is favored by a negative enthalpy, for the other materials is entropy-driven. We show that surface desolvation plays a major role in determining the thermodynamic affinity order for DCF adsorption. This study provides a theoretical basis for the design and optimization of adsorbent materials with high affinity for DCF.

We report an electrolyte-gated single layer graphene super-capacitor, embedded in a polyethylene-on-Au Salisbury mirror optical architecture, working as a THz frequency modulator. The gate-tunable single layer graphene in a quarter wave waveguide ensures 40% optical amplitude modulation depth, and saturable absorption mirror operation, with similar to 4.5 Wcm(-2) saturation intensity. By coupling the modulator with a THz quantum cascade laser frequency comb in an external cavity configuration, we also demonstrate fine-tuning of the intermode beatnote frequency, revealing a promising perspective for metrological sources requiring a tight frequency control of the intermode comb frequency

By integrating, with innovative photonic architectures, in the cavity of miniaturized quantum cascade lasers (QCLs) a multilayers graphene film, we demonstrate passive mode-locking in random THz lasers and self-starting short pulse emission in broadband QCL wire lasers in the 2.3-3.6 THz range.

In this paper, we report on an in-depth study on the growth of nickel silicides, either on a clean Ni(111) substrate or in the presence of a previously-grown epitaxial single graphene (Gr) layer, by means of Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and scanning tunneling microscopy (STM). We demonstrate that two different nickel silicides, namely Ni3Si and Ni2Si, progressively form as the annealing temperature is increased from 450 °C to 600 °C. The presence of the Gr layer does not change the nature of the two silicide phases but rather affects the morphology of the silicide overlayer. Indeed, in the presence of Gr, the deposited silicon atoms intercalate by passing through the Gr defects or domain boundaries and accumulate on specific sample areas, resulting in the formation of multilayer silicide islands. In the absence of Gr, the deposited silicon atoms react uniformly with the nickel substrate, resulting in the formation of homogeneous large scale silicide layers.

The strong interaction between graphene and elemental ferromagnetic transition metals results in considerable shifts of the graphene ? band away from the Fermi level. At the same time, a weakly-dispersing single-spin conical band feature is found in the proximity of the Fermi level at the K? point in the surface Brillouin zone of epitaxially-aligned graphene/Co(0001). Here, the robustness of this electronic state against twisting angles at the interface is experimentally and theoretically demonstrated by showing the presence of similar band features also in the case of rotated graphene domains on Co(0001). Spin-resolved reciprocal space maps show that the band feature in rotated graphene has similar Fermi velocity and spin polarization as its counterpart in epitaxially-aligned graphene. Density functional theory simulations carried out for the experimentally observed graphene orientations, reproduce the highly spin-polarized conical band feature at the graphene K? point, characterized by a hybrid ?-d orbital character. The presence of the conical features in the rotated domains is attributed to the unfolding of the superstructure K? point states exclusively to the K? point of the graphene primitive cell. The similarities found in the electronic character for different graphene orientations are crucial in understanding the magnetic properties of realistic graphene/Co interfaces, facilitating their implementation in spintronics applications.