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Graphene-enhanced Raman scattering (GERS) on isotopically labelled bilayer and a single layer of pristine and partially hydrogenated graphene has been studied. The hydrogenated graphene sample showed a change in relative intensities of Raman bands of Rhodamine 6 G (R6G) with different vibrational energies deposited on a single layer and bilayer graphene. The change corresponds qualitatively to different doping of graphene in both areas. Pristine graphene sample exhibited no difference in doping nor relative intensities of R6G Raman peaks in the single layer and bilayer areas. Therefore, it was concluded that strain and strain inhomogeneities do not affect the GERS. Because of analyzing relative intensities of selected peaks of the R6G probe molecules, it is possible to obtain these results without determining the enhancement factor and without assuming homogeneous coverage of the molecules. Furthermore, we tested the approach on copper phtalocyanine molecules.

Controlling the spatial distribution of functional groups on 2D materials on a micrometer scale and below represents a fascinating opportunity to achieve anisotropic (opto)electronic properties of these materials. Periodic patterns of covalent functionalization can lead to periodic potentials in the monolayer; however, creating such superstructures is very challenging. Here, we describe an original approach to the periodic functionalization of graphene induced by substrate patterning using a pulsed laser. Laser-induced periodic surface structures (LIPSS) are produced on silicon wafers with thermally-grown oxide layers. The irradiation conditions for the formation of LIPSS confined at the SiO 2 /Si interface have been unravelled. LIPSS imprint their periodicity to the reactivity of the monolayer graphene placed on the substrate via modulation of its local doping level. This method is clean, straightforward and scalable with high spatial resolution.

The integration of 2D materials into future applications relies on advances in their quality and production. We here report a synthesis method that achieves ultrahigh optoelectronic performance at unprecedented fabrication scales. A mediator-assisted chemical vapor deposition process yields tungsten-disulfide (WS 2 ) with near-unity photoluminescence quantum yield, superior photosensitivity and improved environmental stability. This enhancement is due to the decrease in the density of lattice defects and charge traps brought about by the self-regulating nature of the growth process. This robustness in the presence of precursor variability enables the high-throughput growth in atomically confined stacks and achieves uniform synthesis of single-layer WS 2 on dozens of closely packed wafers. Our approach enhances the scientific and commercial potential of 2D materials as demonstrated in producing large-scale arrays of record-breaking optoelectronic devices.

Nanobubbles naturally formed at the interface between 2D materials and their substrate are known to act as exciton recombination centers because of the reduced bandgap due to local strain, which in turn scales with the aspect ratio of the bubbles. The common understanding suggests that the aspect ratio is a universal constant independent of the bubble size. Here, by combining scanning tunneling microscopy and molecular dynamics, we show that the universal aspect ratio breaks down in MoS 2 nanobubbles below a critical radius (≈10 nm), where the aspect ratio increases with increasing size. Accordingly, additional atomic-level analyses indicate that the strain increases from 3% to 6% in the sub-critical size range. Using scanning tunneling spectroscopy, we demonstrate that the bandgap decreases as a function of the size. Thus, tunable quantum emitters can be obtained in 2D semiconductors by controlling the radius of the nanobubbles.

Contact resistance between electrically connected parts of electronic elements can negatively affect their resulting properties and parameters. The contact resistance is influenced by the physicochemical properties of the connected elements and, in most cases, the lowest possible value is required. The issue of contact resistance is also addressed in connection with the increasingly frequently used carbon allotropes. This work aimed to determine the factors that influence contact resistance between graphene prepared by chemical vapour deposition and pre-patterned Cu and Au electrodes onto which graphene is subsequently transferred. It was found that electrode surface treatment methods affect the resistance between Cu and graphene, where contact resistance varied greatly, with an average of 1.25 ± 1.54 kΩ, whereas for the Au electrodes, the deposition techniques did not influence the resulting contact resistance, which decreased by almost two orders of magnitude compared with the Cu electrodes, to 0.03 ± 0.01 kΩ.

Low cycling stability is one of the most crucial issues in rechargeable batteries. Herein, we study the effects of a simple ultrasound treatment of graphite for the reversible (de)intercalation of a ClO4− anion from a 2.4 M Al(ClO4)3 aqueous solution. We demonstrate that the ultrasound-treated graphite offers the improved reversibility of the ClO4− anion (de)intercalation compared with the untreated samples. The ex situ and in situ Raman spectroelectrochemistry and X-ray diffraction analysis of the ultrasound-treated materials shows no change in the interlayer spacing, a mild increase in the stacking order, and a large increase in the amount of defects in the lattice accompanied by a decrease in the lateral crystallite size. The smaller flakes of the ultrasonicated natural graphite facilitate the improved reversibility of the ClO4− anion electrochemical (de)intercalation and a more stable electrochemical performance with a cycle life of over 300 cycles.

We present an approach that allows for the preparation of well-defined large arrays of graphene wrinkles with predictable geometry. Chemical vapor deposition grown graphene transferred onto hexagonal pillar arrays of SiO 2 with sufficiently small interpillar distance forms a complex network of two main types of wrinkle arrangements. The first type is composed of arrays of aligned equidistantly separated parallel wrinkles propagating over large distances, and originates from line interfaces in the graphene, such as thin, long wrinkles and graphene grain boundaries. The second type of wrinkle arrangement is composed of non-aligned short wrinkles, formed in areas without line interfaces. Besides the presented hybrid graphene topography with distinct wrinkle geometries induced by the pre-patterned substrate, the graphene layers are suspended and self-supporting, exhibiting large surface area and negligible doping effects from the substrate. All these properties make this wrinkled graphene a promising candidate for a material with enhanced chemical reactivity useful in nanoelectronic applications.

We investigated the heating abilities of magnetic nanoparticles (MNPs) in a high-frequency magnetic field (MF) as a function of surface coating and size. The cobalt ferrite MNPs were obtained by a hydrothermal method in a water–oleic acid–ethanol system, yielding MNPs with mean diameter of about 5 nm, functionalized with the oleic acid. By applying another cycle of hydrothermal synthesis, we obtained MNPs with about one nm larger diameter. In the next step, the oleic acid was exchanged for 11-maleimidoundecanoic acid or 11-(furfurylureido)undecanoic acid. For the heating experiments, all samples were dispersed in the same solvent (dichloroethane) in the same concentration and the heating performance was studied in a broad interval of MF frequencies (346–782 kHz). The obtained results enabled us to disentangle the impact of the hydrodynamic, structural, and magnetic parameters on the overall heating capabilities. We also demonstrated that the specific power absorption does not show a monotonous trend within the series in the investigated interval of temperatures, pointing to temperature-dependent competition of the Brownian and Néel contributions in heat release.

The monolayer character of two-dimensional materials predestines them for application as active layers of sensors. However, their inherent high sensitivity is always accompanied by a low selectivity. Chemical functionalization of two-dimensional materials has emerged as a promising way to overcome the selectivity issues. Here, we demonstrate efficient graphene functionalization with carbohydrate ligands—chitooligomers, which bind proteins of the lectin family with high selectivity. Successful grafting of a chitooligomer library was thoroughly characterized, and glycan binding to wheat germ agglutinin was studied by a series of methods. The results demonstrate that the protein quaternary structure remains intact after binding to the functionalized graphene, and that the lectin can be liberated from the surface by the addition of a binding competitor. The chemoenzymatic assay with a horseradish peroxidase conjugate also confirmed the intact catalytic properties of the enzyme. The present approach thus paves the way towards graphene-based sensors for carbohydrate–lectin binding.

The heterostructures of two-dimensional (2D) and three-dimensional (3D) materials represent one of the focal points of current nanotechnology research and development. From an application perspective, the possibility of a direct integration of active 2D layers with exceptional optoelectronic and mechanical properties into the existing semiconductor manufacturing processes is extremely appealing. However, for this purpose, 2D materials should ideally be grown directly on 3D substrates to avoid the transferring step, which induces damage and contamination of the 2D layer. Alternatively, when such an approach is difficult—as is the case of graphene on noncatalytic substrates such as Si—inverted structures can be created, where the 3D material is deposited onto the 2D substrate. In the present work, we investigated the possibility of using plasma-enhanced chemical vapor deposition (PECVD) to deposit amorphous hydrogenated Si (a-Si:H) onto graphene resting on a catalytic copper foil. The resulting stacks created at different Si deposition temperatures were investigated by the combination of Raman spectroscopy (to quantify the damage and to estimate the change in resistivity of graphene), temperature-dependent dark conductivity, and constant photocurrent measurements (to monitor the changes in the electronic properties of a-Si:H). The results indicate that the optimum is 100 °C deposition temperature, where the graphene still retains most of its properties and the a-Si:H layer presents high-quality, device-ready characteristics.