Search results for "graphe"
showing 10 items of 563 documents
O-Doped Nanographenes: A Pyrano/Pyrylium Route Towards Semiconducting Cationic Mixed-Valence Complexes
2020
Herein we report an efficient synthesis to prepare O‐doped nanographenes, which derive from the longitudinally and latitudinally p‐extension of pyrene. The derivatives are highly fluorescent and feature low‐oxidation potentials. Exploiting electrooxidation, crystals of cationic mixed valence (MV) complexes were grown in which the organic salts organize into face‐to‐face p‐ p stacks, a favorable solid‐state arrangement for organic electronics. Variable‐temperature EPR measurements and relaxation studies suggest a strong electron delocalization along the longitudinal axis of the columnar p‐stacking architectures. Electric measurements of single crystals of the MV salts exhibited a semiconduct…
Nanographenes: Ultrastable, Switchable, and Bright Probes for Super-Resolution Microscopy.
2019
Abstract Super‐resolution fluorescence microscopy has enabled important breakthroughs in biology and materials science. Implementations such as single‐molecule localization microscopy (SMLM) and minimal emission fluxes (MINFLUX) microscopy in the localization mode exploit fluorophores that blink, i.e., switch on and off, stochastically. Here, we introduce nanographenes, namely large polycyclic aromatic hydrocarbons that can also be regarded as atomically precise graphene quantum dots, as a new class of fluorophores for super‐resolution fluorescence microscopy. Nanographenes exhibit outstanding photophysical properties: intrinsic blinking even in air, excellent fluorescence recovery, and sta…
Dependence of the Optical Constant Parameters of p-Toluene Sulfonic Acid-Doped Polyaniline and Its Composites on Dispersion Solvents
2020
The optical constants of Para-Toluene sulfonic acid-doped polyaniline (PANI), PANIchitosan composites, PANI-reduced graphene-oxide composites and a ternary composite comprising of PANI, chitosan and reduced graphene-oxide dispersed in diluted p-toluene sulfonic acid (PTSA) solution and N-Methyl-2-Pyrrolidone (NMP) solvent have been evaluated and compared. The optical constant values were extracted from the absorbance spectra of thin layers of the respective samples. The potential utilization of the materials as the active sensing materials of surface plasmon resonance biosensors has also been assessed in terms of the estimated value of the penetration depth through a dielectric medium. The …
From Seeds to Islands: Growth of Oxidized Graphene by Two-Photon Oxidation
2016
The mechanism of two-photon induced oxidation of single-layer graphene on Si/SiO2 substrates is studied by atomic force microscopy (AFM) and Raman microspectroscopy and imaging. AFM imaging of areas oxidized by using a tightly focused femtosecond laser beam shows that oxidation is not homogeneous but oxidized and nonoxidized graphene segregate into separate domains over the whole irradiated area. The oxidation process starts from point-like “seeds” which grow into islands finally coalescing together. The size of islands before coalescence is 30–40 nm, and the density of the islands is on the order of 1011 cm–2. Raman spectroscopy reveals growth of the D/G band ratio along the oxidation. Sha…
H2 Transformations on Graphene Supported Palladium Cluster: DFT-MD Simulations and NEB Calculations
2020
Molecular dynamics simulations based on density functional theory were employed to investigate the fate of a hydrogen molecule shot with different kinetic energy toward a hydrogenated palladium cluster anchored on the vacant site of a defective graphene sheet. Hits resulting in H2 adsorption occur until the cluster is fully saturated. The influence of H content over Pd with respect to atomic hydrogen spillover onto graphene was investigated. Calculated energy barriers of ca. 1.6 eV for H-spillover suggest that the investigated Pd/graphene system is a good candidate for hydrogen storage.
Limits of stability in supported graphene nanoribbons subject to bending
2016
Graphene nanoribbons are prone to in-plane bending even when supported on flat substrates. However, the amount of bending that ribbons can stably withstand remains poorly known. Here, by using molecular dynamics simulations, we study the stability limits of 0.5-1.9 nm wide armchair and zigzag graphene nanoribbons subject to bending. We observe that the limits for maximum stable curvatures are below ~10 deg/nm, in case the bending is externally forced and the limit is caused by buckling instability. Furthermore, it turns out that the limits for maximum stable curvatures are also below ~10 deg/nm, in case the bending is not forced and the limit arises only from the corrugated potential energy…
Microwave photoassisted dissipation and supercurrent of a phase-biased graphene-superconductor ring
2021
Irradiating normal-superconducting junctions with microwave photons produce spectacular effects, such as Shapiro steps and photoinduced modifications of the dc supercurrent. Moreover, microwave irradiation can also have other, hitherto unexplored consequences, such as a photoassisted dissipation which is phase dependent. Here we present a finite-frequency measurement of both the dissipation and the supercurrent of a phase-biased graphene-superconductor junction in response to microwave photons. We find that, while the supercurrent response is well described by existing theory, the dissipation exhibits unexpected effects which need new theoretical elucidation. Especially with high frequency …
Optical and electronic properties of graphene nanoribbons upon adsorption of ligand-protected aluminum clusters
2014
We have carried out first-principles calculations to investigate how the electronic and optical features of graphene nanoribbons are affected by the presence of atomic clusters. Aluminum clusters of different sizes and stabilized by organic ligands were deposited on graphene nanoribbons from which the energetic features of the adsorption plus electronic structure were treated within density-functional theory. Our results point out that, depending on their size and structure shape, the clusters perturb distinctively the electronic properties of the ribbons. We suggest that such selective response can be measured through optical means revealing that graphene nanoribbons can work as an efficie…
Electrochemical Quantification of H2O2 Released by Airway Cells Growing in Different Culture Media
2022
Quantification of oxidative stress is a challenging task that can help in monitoring chronic inflammatory respiratory airway diseases. Different studies can be found in the literature regarding the development of electrochemical sensors for H2O2 in cell culture medium to quantify oxidative stress. However, there are very limited data regarding the impact of the cell culture medium on the electrochemical quantification of H2O2. In this work, we studied the effect of different media (RPMI, MEM, DMEM, Ham’s F12 and BEGM/DMEM) on the electrochemical quantification of H2O2. The used electrode is based on reduced graphene oxide (rGO) and gold nanoparticles (AuNPs) and was obtained by co-electrode…
Interfacial disorder of graphene grown at high temperatures on 4H-SiC(000-1)
2016
This paper presents an investigation of the morphological and structural properties of graphene (Gr) grown on SiC(000-1) by thermal treatments at high temperatures (from 1850 to 1950 ºC) in Ar at atmospheric pressure. Atomic force microscopy and micro-Raman spectroscopy showed that the grown Gr films are laterally inhomogeneous in the number of layers, and that regions with different stacking-type (coupled or decoupled Gr films) can coexist in the same sample. Scanning transmission electron microscopy and electron energy loss spectroscopy showed that a nm-thick C-Si-O amorphous layer is present at the interface between Gr and SiC. Basing on these structural results, the mechanisms of Gr gro…