Graphene Nanostructures Research Articles

Dimensional effect of graphene nanostructures on cytoskeleton-coupled anti-tumor metastasis.

Interactions between inorganic materials and living systems can be strongly influenced by the dimensional property of the materials, which can in turn impact biological activities. Although the role of biomaterials at the molecular and cellular scales has been studied, research investigating the effects of biomaterials across multiple dimensional scales is relatively scarce. Herein, comparing the effectiveness of two-dimensional graphene oxide nanosheets (GOs) and three-dimensional graphene oxide quantum dots (GOQDs) (though not zero-dimensional because of their significant surface area) in cancer therapies, we have discovered that GOs, with the same mass concentration, exhibit stronger anti-cancer and anti-tumor metastasis properties than GOQDs. Our research, which employed liquid-phase atomic force microscopy, revealed that lower-dimensional GOs create a more extensive nano-bio interface that impedes actin protein polymerization into the cytoskeleton, leading to the prevention of tumor metastasis. These results help to better understand the underlying mechanisms and offer a dimensional perspective on the potential of optimizing the properties of graphene-based materials for clinical applications, e.g., cancer therapy.

Nasschemische Bottom‐up Synthese von Graphen‐Nanostreifen mit atompräzisen Nanoporen

AbstractDie Inkorporation von Nanoporen in Graphen‐Nanostrukturen wurde als effiziente Methode zur Anpassung der Bandlücke und elektronischen Struktur dieser Materialien demonstriert. Allerdings ist die atomgenaue Einbettung uniformer Nanoporen in Graphen‐Nanostreifen (GNS, engl. GNR) auf atomarer Ebene durch Mangel an effizienten Synthesestrategien bislang unterentwickelt. Wir berichten hier vom ersten lösungschemisch dargestellten, vollständig durch Scholl‐Reaktion konjugierten porösen GNS (pGNS), welchen wir durch das atomgenau dargestellte Polyphenylen P1 mit vorinstallierten hexagonalen Makrozyklen zugänglich machen konnten. pGNS enthält periodische Poren im sub‐Nanometerbereich (0.6 nm) mit einem Abstand von 1.7 nm zueinander. Um unsere Synthesestrategie zu untermauern, wurden zwei poröse Modellverbindungen (1 a, 1 b) mit einer zu pGNS identischen Pore erfolgreich dargestellt. Die chemische Struktur und photophysikalischen Eigenschaften von pGNS wurden durch verschiedene spektroskopische Methoden untersucht. Die eingebetteten periodischen Nanoporen vermindern die π‐Konjugation und damit die Interaktion zwischen den Nanostreifen, verglichen mit nicht porösen GNS von ähnlicher Breite. pGNS zeigt demzufolge eine erhöhte Bandlücke und eine verbesserte nasschemische Prozessierbarkeit.

Bottom-up Solution Synthesis of Graphene Nanoribbons with Precisely Engineered Nanopores.

The incorporation of nanopores into graphene nanostructures has been demonstrated as an efficient tool in tuning their band gaps and electronic structures. However, precisely embedding the uniform nanopores into graphene nanoribbons (GNRs) at the atomic level remains underdeveloped especially for in-solution synthesis due to the lack of efficient synthetic strategies. Herein we report the first case of solution-synthesized porous GNR (pGNR) with a fully conjugated backbone via the efficient Scholl reaction of tailor-made polyphenylene precursor (P1) bearing pre-installed hexagonal nanopores. The resultant pGNR features periodic subnanometer pores with a uniform diameter of 0.6 nm and an adjacent-pores-distance of 1.7 nm. To solidify our design strategy, two porous model compounds (1 a, 1 b) containing the same pore size as the shortcuts of pGNR, are successfully synthesized. The chemical structure and photophysical properties of pGNR are investigated by various spectroscopic analyses. Notably, the embedded periodic nanopores largely reduce the π-conjugation degree and alleviate the inter-ribbon π-π interactions, compared to the nonporous GNRs with similar widths, affording pGNR with a notably enlarged band gap and enhanced liquid-phase processability.

On Counting Polynomials of Supercoronenes and Triangle-Shaped Discotic Graphene

Polynomials with an exponential equivalent to the extent of a characteristic partition and coefficients proportional to the multiplicity/occurrence of the accompanying partition are termed as counting polynomials. These polynomials are a well-known method for describing a chemical graph’s molecular invariants as polynomials. It is possible to deduce several key topological invariants from polynomials by either directly taking their value at a certain point or by calculating derivatives or integrals of the polynomial. A topological invariants is a real number correlated with a network that predicts the physico-chemical properties. Chemical modeling, drug design, and structural activity relations use invariants. This paper aims to find the counting polynomials such as Sadhana, omega, PI and theta polynomial of certain graphene nanostructures. In furthermore, topological invariants of specific graphene nanostructures that are related to these counting polynomials are investigated.

Dynamical controllable optical device designed by tunable graphene nanostructures in a PIT structure

Plasmonically induced transparency (PIT) is the classical counterpart of the Electromagnetically induced transparency (EIT) as a quantum nonlinear phenomenon that is achievable in metamaterial structures. In recent years, considerable research has been dedicated to metamaterials for the realization of PIT. Graphene metamaterials have drawn significant attention as a research area due to their unique characteristics, such as surface conductivity tunability by gate electrical biasing. Unlike the EIT effect, the PIT phenomenon is usually achieved between two resonators via near-field coupling without applying any pump. The distance between the two resonators is a vital parameter in PIT. The variation in the coupling strength requires physical parameter reformation of the PIT structure or material change. Here, two bright and dark resonators are utilized. By engineering the electrical field pattern of the bright resonance mode, the coupling strength dynamically changes. For this purpose, three graphene nanostrips as an adjustable quantum structure are used to form a bright resonator, and the quantum confinement of the carriers controls the coupling strength. In addition, the PIT quality factor is engineered from 33.87 for the quantum barrier case to 69.9 for the quantum-well case. Therefore, the coupling strength between the bright and dark resonators can be managed without any geometrical or material changes.

Stages of self-arrangement in growth of nanostructured graphene films related to the flow of ionized species during plasma-enhanced chemical vapor deposition

The ability to directly deposit graphene layers on diverse substrates (including the ones with existing functioning electronic devices) is a very attractive method for integrating two-dimensional materials into electronic systems based on typical semiconductors. However, the task is highly challenging due to the high temperatures required for synthesis of the graphene structures. Plasma-enhanced chemical vapor deposition is an option that can be used to produce large-area graphene layers at sufficiently low temperatures. A lack of deep understanding of the plasma-associated processes limits the ability to directly control graphene growth. In this study, we experimentally investigated how the density of the ionized species flow influences the growth of the nanostructured graphene layers using a custom process chamber layout. The relationship between the growth of the nanostructured carbon-based films and the flow of the ionized species of the working gas mixture was quantitatively characterized for a set of specific parameters. We also analyzed the influence of deposition time and substrate temperature on the growth of the films and discuss the driving mechanisms. Three unique stages were identified in the self-arrangement of the layer. The activation energy of the process was ∼0.31 eV.

The computational study of initial temperature/pressure and atomic doping effects on the growth of crack in graphene nanostructure: Molecular dynamics approach

Graphene is a two-dimensional material with excellent mechanical, electrical, and thermal properties made up of single layers of carbon atoms. Despite the fact that graphene is an emerging material, nowadays graphene has become the leader of the nano field, and with the discovery of its various properties, a tremendous transformation is taking place in nano science. In this study, the molecular dynamics method was used to examine the mechanical characteristics of graphene nanosheets. To achieve this, zig-zag and armchair-shaped graphene nanosheet samples were first simulated. In the second step of this research, by adding boron and nitrogen impurities inside the nanosheet structure, the growth of cracks in these structures was studied, and the effect of factors, such as temperature, pressure, and adding impurity atoms, such as nitrogen and boron were evaluated. In graphene nanosheets with zig-zag and armchair structures, the results demonstrate that the greatest fracture lengths were 28.91 Å and 23.6 Å, respectively. The crack length increased from 23.60 Å to 30.68 Å by increasing the temperature from 300 to 400 K. From 0 bar to 1 bar of pressure, the crack length went from 23.60 Å to 29.01 Å. The type of plates affected the mechanical properties in nanosheets, and nanosheets with armchair edges had better mechanical properties. Finally, the effect of impurities on graphene nanosheets was investigated. The simulations showed improved mechanical properties and resistance to crack growth in the presence of boron, nitrogen, or a combination of these atoms.

Anomalously enhanced subcooled flow boiling in superhydrophobic graphene-nanoplatelets-coated microchannels

In boiling heat transfer, superhydrophobic surface is deemed to reduce the critical heat flux (CHF) due to the immediate formation of an insulating vapor film that inhibits effective heat transfer despite its smaller energy barrier for bubble nucleation than that of a superhydrophilic surface. Here, a subcooled flow boiling investigation is carried out in a microchannel heat sink at a low mass flux condition using the superhydrophilic and superhydrophobic graphene nanoplatelets (GNPs) composite coatings. Interestingly, the flow boiling performance of the superhydrophobic GNPs-coated microchannel significantly transcends that of its superhydrophilic counterpart. By benchmarking with the performance of an uncoated microchannel, the CHF and heat transfer coefficient of the superhydrophobic GNPs-coated microchannel are enhanced up to 134% and 135%, respectively. This anomaly is ascribed to the Cassie Baxter-to-Wenzel transition on the superhydrophobic GNPs-coated surface, which is infiltrated with liquid, restricting the nucleating bubbles from expanding into a vapor film and sustaining an efficient boiling. The initial Wenzel state of the superhydrophobic GNPs surface is primarily ascribed to the rapid intercalation of water molecules via the unique graphene nanostructure. This study sheds new light on the unique wetting behavior of graphene-nanostructured surfaces in the context of microscale flow boiling heat transfer.

Transport studies of two-step synthesized Cu2Se-Graphene nanocomposites

Copper Selenide (Cu2Se), in recent times, rated among the most potential thermoelectric materials, backing its excellent intrinsic thermoelectric (TE) performance arising from the unique nature of Cu + ions behaving like a liquid. Here we present experimental findings of Cu2Se-carbon nanostructure (graphene) composited in which Cu2Se has been synthesized using a cost-effective chemical reduction method, and graphene was incorporated in the Cu2Se matrix by simple mechanical grinding. The TE characteristics of graphene distributed at various weight percentages (0.5, 1, 2, 4, and 5 wt%) in the Cu2Se matrix are presented. The electrical conductivity and power factor of the sample at 450 °C temperature were dramatically improved by adding 1 wt% graphene to the Cu2Se matrix. All samples have been analyzed extensively by Field Emission Scanning Electron Microscopy, X-ray diffraction, High-Resolution Transmission Electron Microscopy, Raman, TE properties measurements, etc. Graphene was discovered to be densely and uniformly spread within the Cu2Se matrix material, resulting in a secondary phase of graphene/Cu2Se interfaces. Although there are minimal changes in the Seebeck coefficient, the power factor improved significantly because of the enhancement in electrical conductivity by the incorporation of graphene. The power factor in 1 wt% graphene incorporated Cu2Se enhanced to 1250 μW/mK2 at 450 °C compared to the power factor of 585 μW/mK2 for the bare Cu2Se sample. The purpose of this study is to determine the optimum graphene percentage that gives better performance.

Properties and tribological evaluation of graphene and fullerene nanoparticles as additives in oil lubrication

In this study, SAE-0W20 engine oil was mixed with graphene and fullerene nanoparticles. The goal of this study was to evaluate and compare the effects of different carbon nanoparticles on the thermal, rheological, and tribological properties of engine oil, such as thermal degradation, viscosity, friction, and wear. Using a two-step process, graphene and fullerene nanostructures were dispersed in low-viscosity SAE-0W20 engine oil at a concentration of 0.05 wt.%. The friction and wear characteristics were evaluated in a customized cylindrical block-on-ring tribology test according to the ASTM G77 standard. Graphene and fullerene nanoparticles protect contact surfaces by forming a very thin protective film between moving mechanical parts thus resulting in wear and friction reduction. The results showed graphene nanoparticles have improved significantly the tribological performance of SAE-0W20 engine oil.

Role of graphene nanoparticles on the electrophysical processes in PVP and PVP:ZnTiO3 polymer layers at Schottky diode (SD)

In this paper, a polyvinyl pyrrolidine (PVP) polymer layer is inserted between the metal–semiconductor (MS) structure to manufacture a metal–polymer–semiconductor (MPS) structure or Schottky diode (SD). The zinc titanate and graphene nanostructures were doped into the PVP layer individually and together to improve the electrical performance of the MPS-type SD. The crystalline size, surface morphology, and band gap energy of the ZnTiO3 nanostructures are examined by the x-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and ultraviolet–visible (UV–Vis) spectroscopy, respectively. It is common to measure the current–voltage (I–V) features (at ±3 V) of these five structures for calculating the reverse saturation current (I 0), barrier height, ideality factor (n), series (R s), and shunt (R sh) resistances as the main electrical parameters utilizing the thermionic emission, Norde, and Cheung models. Also, the forwarded-bias energy-dependent surface states density (N ss) and the forward/reverse biased current conduction mechanisms are studied and discussed. The rectifying ratio (RR) of Al/PVP:Gr-ZnTiO3/p-Si SD has the highest increase among these five SDs while the lowest I 0 and highest R sh are related to the Al/PVP:Gr/p-Si (MPS2) and Al/PVP:ZnTiO3/p-Si (MPS3) SDs, respectively. Therefore, doping Gr into the PVP interlayer increases the electrical conduction in the SDs although PVP:Gr-ZnTiO3 polymer layer improves the RR of SDs.

Optical Conveyor Belt With Electrically Tunable Graphene Plasmonic Nanorings

In this paper, we propose a plasmonic conveyor belt based on a periodically arranged graphene nanorings (GNRs) with different size, on which the hot spots could be continuously lighted up by electrically tuning the Fermi level of graphene and could be used for the trapping and transporting of nanoparticles even under a uniform Mid-infrared or terahertz light excitation. Graphene nano-structure supports surface plasmon resonance, and its resonance condition is not only related with its size, but also could be adjusted by its Fermi level, as well as the applied gate voltage. In this way, a periodically arranged GNRs with different size can be excited in turn, thus realizing the function of transporting nanoparticles without reconfiguring the light excitation. In light of the rotational symmetry of GNRs, our polarization-independent design approach obviously has more advantages than the ones consisting of the graphene strips. In addition, the feasibility of the particle-separation is demonstrated. As confirmed by the numerical analysis, our design offers an optimized scheme for polarization-independent and electrically tunable plasmonic conveyor belt, which could be used in many on-chip optofluidic applications.

Graphene as Nanocarrier for Gold(I)-Monocarbene Complexes: Strength and Nature of Physisorption.

Gold(I) metal complexes are finding increasing applications as therapeutic agents against a variety of diseases. As their potential use as effective metallodrugs is continuously confirmed, the issue of their administration, distribution and delivery to desired biological targets emerges. Graphene and its derivatives possess attractive properties in terms of high affinity and low toxicity, suggesting that they can efficaciously be used as drug nanocarriers. In the present study, we computationally address the adsorption of a gold(I) N-heterocyclic monocarbene, namely, IMeAuCl (where IMe = 1,3-dimethylimidazol-2-ylidene), on graphene. The Au(I) N-heterocyclic carbene family has indeed shown promising anticancer activity and the N-heterocyclic ring could easily interact with planar graphene nanostructures. By means of high-level electronic structure approaches, we investigated the strength and nature of the involved interaction using small graphene prototypes, which allow us to benchmark the best-performing DFT functionals as well as assess the role of the different contributions to total interaction energies. Moreover, realistic adsorption enthalpies and free energy values are obtained by exploiting the optimal DFT method to describe the drug adsorption on larger graphene models. Such values (ΔHads = -18.4 kcal/mol and ΔGads= -7.20 kcal/mol for the largest C150H30 model) indicate a very favorable adsorption, mainly arising from the dispersion component of the interaction, with the electrostatic attraction also playing a non-negligible role.

Electrochemical H2O2 sensor based on a Au nanoflower-graphene composite for anticancer drug evaluation

Reliable H2O2 sensors for in situ cellular monitoring under drug stimulation can be developed as a powerful and versatile tool for drug evaluation. Herein, a novel electrochemical biosensor capable of detecting and quantifying H2O2 was fabricated by graphene and shape-controlled gold nanostructures. With the help of polyelectrolytes, gold exhibited hierarchical flower-like nanostructures. This kind of nanozyme material exhibited a prominent electrochemical response for H2O2. Electrocatalytic activity for H2O2 reduction with high sensitivity (5.07◊10−4 mA μmol L−1 cm−2) and good detection capability (the lowest detection limit is 4.5 μmol L−1 (S/N = 3)) were achieved. This electrochemical biosensor was successfully used to measure the concentration of H2O2 released from HepG2 hepatoma cells. Ascorbic acid (AA) and Camellia nitidissima Chi saponins (CNCS) were selected as model drugs, and their anticancer activities were compared by in situ monitoring of H2O2. Interestingly, the electrochemical sensor showed remarkable sensitivity, accuracy, and rapidity compared with the traditional enzymatic detection kit. In brief, the as-synthesized nanostructured H2O2 sensors can be applied to assess the antitumor properties of candidate drugs and inspire developments for personalized health care monitoring and cancer treatment.

Reconfigurable Nonlinear Photonics Devices Based on Nanostructured Graphene. A Review

Reconfigurable Nonlinear Photonics Devices Based on Nanostructured Graphene. A Review

Mathematical Models of Magnetic and Graphene Nanostructures Based on Autonomous Blocks with Floquet Channels in Microwave and THz Nanotechnologies

Mathematical Models of Magnetic and Graphene Nanostructures Based on Autonomous Blocks with Floquet Channels in Microwave and THz Nanotechnologies

Quantum studies of the interaction of nanostructured graphene with polymethyl methacrylate for dental applications

Quantum studies of the interaction of nanostructured graphene with polymethyl methacrylate for dental applications

Theoretical studies on optical properties of Beltrami-shaped curved graphene

We compute the optical conductivity and polarization for an out-of-plane deformation in graphene nanostructure using a theoretical approach based on Dirac equation solutions on curved dimensional space-time, where the space part is considered to correspond to the Beltrami pseudosphere which belongs to the family of surfaces with negative constant Gaussian curvature. We found that different parameters of deformation along one direction translate into an enhancement of the optical conductivity peaks and polarization magnitude in the far-infrared frequencies. This allows for a very high degree of polarization with a single layer graphene and opens up a potential prospect of employing graphene layer as efficient polarizers. Therefore the experimental predictions related to the electronic configuration of the corresponding graphene-like sample may be explicitly worked out.

Remote-Triggered Domino-like Cyclodehydrogenation in Second-Layer Topological Graphene Nanoribbons

Cyclodehydrogenation reactions in the on-surface synthesis of graphene nanoribbons (GNRs) usually involve a series of Csp2-Csp2 and/or Csp2-Csp3 couplings and just happen on uncovered metal or metal oxide surfaces. It is still a big challenge to extend the growth of second-layer GNRs in the absence of necessary catalytic sites. Here, we demonstrate the direct growth of topologically nontrivial GNRs via multistep Csp2-Csp2 and Csp2-Csp3 couplings in the second layer by annealing designed bowtie-shaped precursor molecules over one monolayer on the Au(111) surface. After annealing at 700 K, most of the polymerized chains that appear in the second layer covalently link to the first-layer GNRs that have partially undergone graphitization. Following annealing at 780 K, the second-layer GNRs are formed and linked to the first-layer GNRs. Benefiting from the minimized local steric hindrance of the precursors, we suggest that the second-layer GNRs undergo domino-like cyclodehydrogenation reactions that are remotely triggered at the link. We confirm the quasi-freestanding behaviors in the second-layer GNRs by measuring the quasiparticle energy gap of topological bands and the tunable Kondo resonance from topological end spins using scanning tunneling microscopy/spectroscopy combined with first-principles calculations. Our findings pave the avenue to diverse multilayer graphene nanostructures with designer quantum spins and topological states for quantum information science.

Superlubricity of Titanium Alloy Enabled by MoS2 Flakes and a-C:H Film

Titanium alloys are often used in engineering fields including aerospace, cryogenic technologies, and weaponry due to their remarkable qualities. However, several issues including a high coefficient of friction, weak wear resistance, and low hardness hinder their widespread usage. Despite several efforts to enhance their tribology, achieving ultra-low friction on titanium alloy surfaces remains a challenging problem in materials science. Here, we report on the superlubricity of a MoS2 + a-C:H (Mo-a films) composite film, prepared by magnetron sputtering and spraying to lubricate titanium alloy surfaces. Robust superlubricity was achieved by the Mo-a composite films with a coefficient of friction (COF) below 0.007 in a helium environment. Compared to the reference titanium alloy substrates, the introduction of Mo-a composite film reduced the friction coefficient to roughly 1%, and the a-C:H film reduced wear by three orders of magnitude. High-resolution characterizations indicate that this enhanced tribology can be attributed to the formation of transfer film, which is enriched with nanostructured graphene sheets and MoS2 nanoscrolls, and is formed due to shear stress-induced structural transformation of a-C:H films and MoS2 nanosheets. This transfer film transitioned the initial high-resistance steel-to-a-C:H contact to super low-resistance steel-to-transfer film contact, thus achieving superlubricity and a remarkable wear reduction. This work outlines a pathway to solving the poor wear resistance and high friction coefficient problem of titanium alloy surfaces, which can be an important guideline for applications of titanium alloys in mechanical engineering.