Applications of Graphene

Transition metal dichalcogenides (TMDs) exhibit unique properties and potential applications when reduced to one-dimensional (1D) nanoribbons (NRs), owing to quantum confinement and high edge densities. However, effective growth methods for self-aligned TMD NRs are still lacking. We demonstrate a versatile approach for lattice-guided growth of dense, aligned MoS2 NR arrays via chemical vapor deposition (CVD) on anisotropic sapphire substrates, without tailored surface steps. This method enables the synthesis of NRs with widths below 10 nanometers and longitudinal axis parallel to the zigzag direction, being also extensible to the growth of WS2 NRs and MoS2-WS2 heteronanoribbons. Growth is influenced by both substrate and CVD temperature, indicating the role of anisotropic precursor diffusion and substrate interaction. The 1D nature of the NRs was asserted by the observation of Coulomb blockade at low temperatures. Pronounced catalytic activity was observed at the edges of the NRs, indicating their promise for efficient catalysis.

The performance gain oriented nano-structurisation has opened a new pathway for tuning mechanical features of solid matter vital for application and maintained performance. Simultaneously, the mechanical evaluation has been pushed down to dimensions way below one micrometre. To date, the most standard technique to study the mechanical properties of suspended 2D materials is based on nanoindentation experiments. In this work, by means of micro-Brillouin light scattering we determine the mechanical properties, i.e. Young modulus and residual stress, of polycrystalline few nanometres thick MoS 2 membranes in a simple, contact-less, non-destructive manner. The results show huge elastic softening compared to bulk MoS 2 , which is correlated with the sample morphology and the residual stress.

Two-dimensional (2D) WO 3 nanosheets exhibit a range of novel properties and functionalities that render them attractive for advanced nanotechnologies. However, at the ultimate 2D limit of single-layer thickness the structural properties of WO are unclear. Here we fabricated, using MBE techniques, a crystalline 2D WO 3 overlayer on a Ag(100) surface and unveil its geometric, electronic and vibrational structure via a combination of state-of-the-art experimental (microscopic and spectroscopic) and computational techniques. The 2D WO 3 phase forms a bilayer with staggered arrangement of WO 6 octahedra, linked together by corner and edge sharing, which is significantly different from the cubic and monoclinic WO 3 bulk structures, but resembles a bilayer of the -MoO 3 layered bulk lattice. Such 2D WO 3 bilayer on Ag(100) is a robust non-polar structure, which is incommensurate in various rotational orientations, weakly coupled to the metal substrate, and according to the density functional theory (DFT) calculations should survive as a stable free-standing layer, i.e. as a nanosheet.

Two-dimensional (2D) WO 3 nanosheets exhibit a range of novel properties and functionalities that render them attractive for advanced nanotechnologies. However, at the ultimate 2D limit of single-layer thickness the structural properties of WO are unclear. Here we fabricated, using MBE techniques, a crystalline 2D WO 3 overlayer on a Ag(100) surface and unveil its geometric, electronic and vibrational structure via a combination of state-of-the-art experimental (microscopic and spectroscopic) and computational techniques. The 2D WO 3 phase forms a bilayer with staggered arrangement of WO 6 octahedra, linked together by corner and edge sharing, which is significantly different from the cubic and monoclinic WO 3 bulk structures, but resembles a bilayer of the -MoO 3 layered bulk lattice. Such 2D WO 3 bilayer on Ag(100) is a robust non-polar structure, which is incommensurate in various rotational orientations, weakly coupled to the metal substrate, and according to the density functional theory (DFT) calculations should survive as a stable free-standing layer, i.e. as a nanosheet.

Metal-supported graphene nanocomposites with single atoms or small clusters are of interest for various catalytic processes, including applications in batteries, fuel cells, water electrolysis, and chemical synthesis. Typically, graphene oxide is reduced in the presence of metal salts to produce metal-graphene nanocomposites. However, graphene itself has reductive properties and can react with metal ions in higher oxidation states in a suitable solvent. While direct reactions (dip and coat or wet coating) with metal salts have been described several times, less is known about the kinetics.

We have performed a Density Functional study of the CO adsorption in B-doped, N-doped and BN-co-doped graphene considering a coronene based model in order to estimate the applications of this systems as CO-sensor. Different monosubstituted, disubstituted and trisubstituted alternatives of combining these two heteroatoms in a substitutional chemical doping and the influence of the relative positions of the heteroatoms are analyzed. In this study, the stability selectivity for CO adsorption and the change in the electric properties for the presence of this molecule, have been evaluated through the calculation of binding energy, CO-adsorption's energy and the gap HOMO-LUMO change due to CO adsorption. The results indicated that, even though all the configurations were stables and was confirmed a CO physical adsorption in all of them, the relative positions of Nitrogen and Boron gave different stabilities and different responses to the CO adsorption. Since monosubstituted Boron-coronene was the second in stability respect to pristine coronene, showed the highest CO adsorption energy and was also the second highest Δ(Δ HOMO-LUMO) value, this structure could be potentially a good CO-sensor.

Penelitian ini bertujuan untuk mengetahui besarnya band gap dan konduktivitas bahan semikonduktor lapisan tipis Sn(S0,8Te0,2) dan Sn(S0,6Te0,4) hasil preparasi dengan teknik evaporasi termal. Penelitian ini dimulai dari pembuatan lapisan tipis Sn(S0,8Te0,2) dan Sn(S0,6Te0,4) menggunakan metode evaporasi termal pada tekanan 2x10-5 mbar. Hasil preparasi lapisan tipis Sn(S0,8Te0,2) dan Sn(S0,6Te0,4) kemudian di uji karakteristiknya. Karakteristik sifat listrik diamati menggunakan FPP (Four Point Probe) dan karakteristik sifat optik diamati menggunakan UV-Vis Spectroscopy. Dari uji FPP didapat nilai resistansi, restisivitas, tebal dan tipe konduksi lapisan tipis yang terbentuk data digunakan untuk menentukan besar konduktivitas. Dari uji Spektrofotometer UV-Vis berupa nilai absorbansi transmisi, reflektansi sebagai fungsi panjang gelombang untuk menentukan besar band gap Hasil uji UV-Vis yang diolah menggunakan metode taue plot dengan bantuan software Ms. Origin 50 diperoleh band gap la...

In this paper, we report the effect of MnS nanoparticles on the electrochemical performance of 1D-MnO2
stable nanorods for supercapacitor electrodes. The MnS-incorporated 1D-MnO2 (MnO2/MnS) nanorods
were produced using a facile two-step hydrothermal method. Morphological investigation reveals that
the incorporation of MnS nanoparticles distorts the lattice fringes and extends the interlayer spacing of
the MnO2 nanorods. The structural study showed that MnS modified the structural parameters of the
nanocomposite. XPS analysis revealed defects in the nanocomposite due to the generation of oxygen
vacancies. The MnO2/MnS nanocomposite improves capacitive performance and has the highest specific
capacitance of 305 F g−1
, at a current density of 1 A g−1 with an energy density of 5.7 W h kg−1 and
a power density of 449 W kg−1
. The MnO2/MnS nanocomposite electrodes exhibit exceptional cyclic
stability after 5000 charging and discharging cycles. With enhanced specific capacitance and excellent
cyclic stability, the MnO2/MnS nanocomposite paves a new way to produce supercapacitor electrodes

This make possible to verify if it is necessary to be considered as a toxicological co-factor Various published evidence finded graphene impurity in vial some or in vaccinated blood. But It is relevant to deeply investigate this phenomena using only scientifc evidence. Crucial also to verify the subpopulation distribution of pathological event in vaccinated like pericarditys or central nervous system thrombosys as well as the use of some technological tool like smartphone in the various age classes. This method make possible to generate hypotesys to be better veriefied. In this work is used a neutral approch without pre-concept.

Aim of this work is to search and analyze scientific literature involved in the effect played by wireless comunication radiation in the S.A.R.S-COV-2 spike protein derivates pathological process. This make possible to verify if it is necessary to be considered as a toxicological co-factor Various published evidence finded graphene impurity in vial some COVID-19 vaccine (P. Campra) or in vaccinated blood. But It is relevant to deeply investigate this phenomena using only scientifc evidence. Crucial also to verify the subpopulation distribution of pathological event in vaccinated like pericarditys or central nervous system thrombosys as well as the use of some technological tool like smartphone in the various age classes. This method make possible to generate hypotesys to be better veriefied. In this work is used a neutral approch without pre-concept.

Graphite electrodes so obtained from waste zinc-carbon batteries were washed several times with water to remove impurities and made into powder and then treated with mixture of HCl and HNO3(3:1)followed by drying at 600C to get pure graphite powder that was used as a starting material to synthesizegraphene oxide(GO) by improved Hammer’s method.The graphene oxide(GO) again treated with
Azadirachta indica leaf extract and converted to reduced graphene oxide(RGO).The rGO so obtained wascharacterized by UV-VIS Spectrophotometer, Fourier Transform Infrared Spectrophotometer, X-ray
Diffractometer and Scanning Electron Microscope. The characterization data gave clear evidence on effective formation of reduced graphene oxide.

Few layer graphene (FLG) was synthesized by-wave assisted exfoliation of expanded graphite in toluene with an overall yield from c.a. 7% to 20%. A significant difference in the absorption of-waves by the expanded graphite and toluene allowed a rapid heating of the medium. The number of FLG sheets varies from 3 to 12, while the lateral size of the sheets exceeds few ms. The obtained FLG exhibits very low resistance with average value of 1.6 k (500 minimum) which is comparable to that of high quality graphenes synthesized by CVD methods, and lower than numbers of exfoliated graphenes.

Graphene and reduced graphene oxide are promising materials that are increasingly used in the field of polymer materials. In this study, reduced graphene oxide was prepared by chemical exfoliation of graphite, and subsequently, used in different amounts of 0.05, 0.2 and 2.0 wt.% in poly(ethylene-co-vinyl acetate)-EVA nanocomposites and foams. The approach used to prepare the reduced graphene oxide showed good efficiency with nanometer-scale particles and an average number of eight layers. Reduced graphene oxide in water suspension was introduced into the EVA by thermofusion using a closed mixer. Subsequently, sheets and foams were prepared by thermocompression molding using chemical expansion and crosslinking agents. The leading results suggest that the presence of reduced graphene oxide could change the cell morphology of the foam by increasing the cell density and decreasing its size. The sample containing 2 phr of reduced graphene oxide exhibited lower density and higher resistance to compression compared to pure EVA.

Aim of this work is to search and analyze scientific literature involved in the effect played by wireless comunication radiation in the S.A.R.S-COV-2 spike protein derivates pathological process. This make possible to verify if it is necessary to be considered as a toxicological co-factor Various published evidence finded graphene impurity in vial some COVID-19 vaccine (P. Campra) or in vaccinated blood. But It is relevant to deeply investigate this phenomena using only scientifc evidence. Crucial also to verify the subpopulation distribution of pathological event in vaccinated like pericarditys or central nervous system thrombosys as well as the use of some technological tool like smartphone in the various age classes. This method make possible to generate hypotesys to be better veriefied. In this work is used a neutral approch without pre-concept.

Luisetto M, Almukhtar N, Edbey K, Cipelli Benzi R, Tarro G, Ansovini R, Mashori Gulam Rasool, Fiazza C, Cabianca L and Latyshev O. Yurevich. S.A.R.S Cov-2 Spike Protein Derivates – Graphene And Wireless Comunications Radiation: Epidemiological-Chemico Physical And Toxicological Aspects -Scientific Evidence. Trends Gen Med. 2023; 1(1): 1-11.

Aim of this work is to search and analyze scientific literature involved in the effect played by wireless comunication radiation in the S.A.R.S-COV-2 spike protein derivates pathological process. This make possible to verify if it is necessary to be considered as a toxicological co-factor Various published evidence finded graphene impurity in vial some COVID-19 vaccine (P. Campra) or in vaccinated blood. But It is relevant to deeply investigate this phenomena using only scientifc evidence. Crucial also to verify the subpopulation distribution of pathological event in vaccinated like pericarditys or central nervous system thrombosys as well as the use of some technological tool like smartphone in the various age classes. This method make possible to generate hypotesys to be better veriefied. In this work is used a neutral approch without pre-concept.

Based on the fact that if present graphene in vials of nanolipids of
biopharmaceutical the aspects must to be coloured the reported findings by some
independet researcher of graphene like particle in viasl of m Rna covid-19 vaccine
seem to suggest that this impurity can be present only inside the nanolipids. The
production fo this encapulated biotecnological product imply the mixing of an acqueos
phases (mRna ) with an lipidic phases (nanolipids). The graphene finded as reported,
probably due by purification steps, because idrofilic it must to be encapsulated. The
Raman spectra of registrated m RNA C19 vaccine not revealed graphene particle ,
but in literature it is reported that the direct tecchnique is no the best way to to detect
well the nanolipids payload : so a negative results not imply this it not present inside
the nanoparticle. Aim of this work is to investigate the manifacturing process of this
biotechnological products submitting to the reseacrher an hypotesys of work than can
explain all this pheneomena: the possible segregation of graphene inside the
nanolipids. Great enphasys is given to the size , the chemico physical property like
idrophilicity of the graphene particle versus the nanolipids used in some m RNA C19
vaccine, and the property of inside /outside this particles.
Keywords: material science, graphene, size, idrophilic, manifacturing, nanolipids,
segregation, chemico physical property, Purification, impurity, raman spectra, peaks,
interference, nanolipids, payload.

Exploring the synthesis of an n-type
flexible hybrid organic/inorganic composite sheet,
this study enhances PVDF with Ni and Cu
nanoparticles (NP) to improve its electrical
conductivity and thermoelectric properties for
various room temperature applications. Ni and Cu
NP, synthesized through a chemical reduction
method, were smoothly incorporated into a PVDF
matrix. The optimal NP to PVDF ratio was
determined to be 2:3 (wt), as further addition of
particles led to the formation of cracks and weakened
the flexibility of the sheet. The synthesized materials'
elemental composition, including Ni and Ni-Cu
composites in various ratios, was analyzed using
XRF, aligning closely with expected ratios and
highlighting synthesis precision. FTIR spectroscopy
specifies molecular structures and phases in PVDF-
based nanocomposites. XRD patterns confirmed Ni
and Cu NP presence and revealed trends in PVDF
behavior with decreasing particle size. SEM imaging
depicted well-defined particles and surface coverage
in PVDF/Ni sheets, with additional Cu resulting in
reduced particle density on the polymer surface,
indicating compositional correlation The highest
power factor, 4.964 µW m-1 K
-2 and figure of merit,
0.003, were achieved at 298 K for the composite with
the weight ratio of PVDF/Ni (2:3). The four-probe
method demonstrated an impressive conductivity of
25.64 S cm-1 at 298 K. Furthermore, Seebeck
coefficient showed a - 44 µV K-1
indicating n-type
behavior, and thermal conductivity was 0.5 W m-1 K
-
1
, which is consistent with the low thermal
conductance required for effective thermoelectric
materials. Excessive addition of Cu nanoparticles to
the PVDF/Ni composite disrupts optimal Ni-PVDF
interaction, impeding continuous conductive
pathways and diminishing electrical conductivity
and thermoelectric properties, highlighting the need
for precise composite formulation. Tensile strength
and elastic modulus measurements were conducted,
highlighting the flexibility of the developed
thermoelectric material. This study lays the
foundation for the successful creation of a low-cost,
n-type flexible thermoelectric material using Ni
nanoparticles and PVDF.

Indexed Terms- PVDF, Ni nanoparticles, Flexible,
n-type, Thermoelectric, Power factor

The thermal properties of acrylonitrile butadiene styrene (ABS) composites with talc and calcium carbonate (CaCO3) at 10%, 20%, 30%, and 40% loading were characterized using thermal methods like differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and heat deflection temperature (HDT). The study was carried out to investigate the effect of fillers with different shape on the properties like decomposition temperature, HDT of ABS. CaCO3 particles are spherical and have an aspect ratio of 1, whereas talc is long, platy in nature and has a higher aspect ratio of typically about 20:1. Titanate coupling agent was added to improve the interfacial adhesion between the filler and the ABS matrix. Thermal properties showed no significant change with respect to the HDT, glass transition temperature by DSC as well as decomposition temperature by TGA methods.

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In this research work, Bi2O3, Bi2O3/GO and Bi2O3/CuO/GO nanocomposites have been synthesized via an eco-friendly green synthesis technique, solgel route and co-precipitation method respectively for the assessment of antibacterial activity as well as in vivo toxicity. The XRD patterns confirm the formation of Bi2O3, Bi2O3/GO and Bi2O3/CuO/GO nanocomposites showing monoclinic structures. Crystallite size and lattice strain are calculated by Scherrer equation, Scherrer plot and Willimson Hall plot methods. Average crystallite size measured for Bi2O3, Bi2O3/GO and Bi2O3/CuO/GO nanocomposites by Scherrer equation, Scherrer plot and WH-plot methods are (5.1, 13.9, 11.5)nm, (5.4, 14.2, 11.3)nm and (5.2, 13.5, 12.0)nm respectively. Optical properties such as absorption peaks and band-gap energies are studied by UV–vis spectroscopy. The FTIR peaks at 513 cm−1, 553 cm−1and 855 cm−1confirms the successful synthesis of Bi2O3, Bi2O3/GO and Bi2O3/CuO/GO nanocomposites. The antibacterial activity ...

In this paper, electronic modeling and electromagnetic modeling of graphene nanoribbons (GNRs) are rigorously investigated. From the electronic point of view, a GNR is modeled through its linear band diagram; in this regard, the GNR is doped electrostatically in a waveguide configuration. Then, the capacitance of this waveguide is computed according to the associated band diagram. From the electromagnetic point of view, the GNR is considered as a conducting sheet, which is characterized by an effective conductivity. Then, a waveguide switch comprised of three GNRs is designed, which supports TM-polarized surface plasmon polariton propagation modes at 30 THz. To reach a miniaturized structure, the group velocity of plasmons is decreased to be comparable with Fermi velocity in graphene; consequently, an effective conductivity model is required to accurately predict propagation of slow waves in the GNRs. Finally, this conductivity model is verified by proposing a nonlocal circuit model.

In this study graphene oxide (GO) synthesized by modified Hummer's method. Surface of GO was modified with biopolymer chitosan (CS) and then grafted with the ZnO nanoparticles. GO/ZnO/CS was investigated as adsorbent for the elimination of Pb (II) and Cr (VI) ions from aqueous solutions. The Box-Behnken Design (BBD) within the framework of response surface methodology (RSM) was employed to optimize different parameters, which including pH of the metal solution, initial metal ions concentration and contact time. The quadratic model was best fitted for characterizing the influence of adsorption parameters on adsorption capacity (q e) and percent removal (% R), exhibiting strong statistical support with R 2 values and p-values. To explore the interactions between these parameters and determine the ideal conditions for removing Pb (II) and Cr (VI) ions, we employed second-order polynomial equations, performed analysis of variance (ANOVA), and generated three-dimensional surface plots. The optimum parameters for Pb (II) ions were pH 5, initial concentration 60 mg/L and 120 min contact time, with 110.88 mg/g adsorption capacity and 92.4 % removal efficiency. For Cr (VI) ions 84.5 mg/g adsorption capacity and 70.5 % removal was achieved at pH 2, 60 mg/L metal concentration at 112 min contact time.

Due to the strong in-plane but weak out-of-plane bonding, it is relatively easy to separate nanosheets of two-dimensional (2D) materials from their respective bulk crystals. This exfoliation of 2D materials can yield large 2D nanosheets, hundreds of micrometers wide, that can be as thin as one or a few atomic layers thick. However, the underlying physical mechanisms unique to each exfoliation technique can produce a wide distribution of defects, yields, functionalization, lateral sizes, and thicknesses, which can be appropriate for specific end applications. The five most commonly used exfoliation techniques include micromechanical cleavage, ultrasonication, shear exfoliation, ball milling, and electrochemical exfoliation. In this review, we present an overview of the field of 2D material exfoliation and the underlying physical mechanisms with emphasis on progress over the last decade. The beneficial characteristics and shortcomings of each exfoliation process are discussed in the context of their functional properties to guide the selection of the best technique for a given application. Furthermore, an analysis of standard applications of exfoliated 2D nanosheets is presented including their use in energy storage, electronics, lubrication, composite, and structural applications. By providing detailed insight into the underlying exfoliation mechanisms along with the advantages and disadvantages of each technique, this review intends to guide the reader toward the appropriate batch-scale exfoliation techniques for a wide variety of industrial applications.

Development of strong and tough biopolymer materials with favorable conductive properties is highly desirable and remains a great challenge in current scientific research. In this study, a novel strategy is designed to prepare a conductive plant protein-based films through the integration of functional graphene oxide (GO) into a hyperbranched network. The process was based on the Fe(III) ion-triggered simultaneous polymerization of dopamine and pyrrole. The incorporation of conductive GO nanosheets with the in situ formed polypyrrole nanoparticles could uniquely act as cross-linking sites to make the nanocomposites highly conductive. As a result, strong sacrificial metal-ligand bonds and covalent bonds would be confined within the network. The toughness and strength of the nanocomposite film increased by 428.5% and 324.1%, respectively. In addition, this hybrid film showed significant improvement in electrical and thermal conductivities owing to the contribution of the highly conductive hyperbranched structures in the polymer matrix. Furthermore, this renewable and biodegradable film had superior water resistance and ultraviolet-barrier performance, which are of great importance to the practical applications.

In this work, we have developed a general methodology for constructing an activatable biosensor utilizing a thermo-responsive polymer and two-dimensional nano-sheet. We have demonstrated the detection of four different types of biological compounds using the smart PEGMA (poly(ethylene glycol) methyl ether methacrylate), oligonucleotides and graphene oxide nanoassembly. The activity of the functional nano-device is controlled with a thermo-switch at 39 °C. In this design, the nano-sized graphene oxide serves as a template for fluorophore labeled probe oligonucleotides while quenching the fluorescence intensities dramatically. On the other hand, the PEGMA polymer serves as an activatable protecting layer covering the graphene oxide and entrapping the probe oligonucleotides on the surface. The PEGMA polymers are hydrophobic above their lower critical solution temperature (LCST) and therefore interact strongly with the hydrophobic surface of graphene oxide, creating a closed configuration (OFF state) of the nanodevice. However, once the temperature decreases below the LCST, the polymer undergoes conformational change and becomes hydrophilic. This opens up the surface of the graphene oxide (open configuration, ON state), freeing the encapsulated payload on the surface. We have tuned the activity of the nano-device for the detection of a sequence specific DNA, miR-10b, thrombin and adenosine. The activity of our functional system can be decreased by ~80% with a thermo-switch at 39 °C. Our approach can be extended to other anti-sense oligonucleotide, aptamer or DNAzyme based sensing strategies.

Oxygen vacancies (O.Vs) play vital role in tailoring structural, optical and dielectric properties of nanostructures. Here we prepared SnO 2 /graphite (SG) nanocomposite by growing SnO 2 nanoparticles on graphite sheets via hydrothermal method. Enhanced dielectric behavior due to increase in the oxygen vacancies (O.Vs) has been observed in SnO 2 /graphite (SG) nanocomposite synthesized. To reveal the underlying origin here, we investigated the structural, morphological, optical, electrochemical and dielectric properties. The growth of SnO 2 NPs on graphite sheets resulted in small-sized NPs (Average size 10.89 ± 0.24 nm) inducing stresses in the structure causing large defect density (O.Vs). The formation of SG nanocomposite has been validated via SEM, TEM, EDX and FTIR. EDX, XPS and Photoluminescence (PL) spectra of SG nanocomposite manifest the presence of large oxygen vacancies (O.Vs). It is revealed that the bandgap of the host material SnO 2 (from ultra violet to the visible window) can be engineered by controlling the assimilation of SnO 2 NPs on GNs. SG nanocomposite exhibits reversible redox process with high anodic and cathodic currents, low internal (0.47 X) and charge transfer (4.08 X) resistances, correspondingly, low voltage drop (IR) 0.56 V and high capacitance 54.8 F/g. Variations in dielectric constant (e), dielectric loss (e 00) and conductivity (r ac) are attributed to the increased concentration of O.Vs and introduction of conductive carbon (graphite). The variations in dielectric properties are attributable to Maxewell-Wagner interfacial polarization and hopping process.

Recent reports of upconversion and white light emission from graphitic particles warrant an explanation of the physics behind the process. We offer a model, wherein the upconversion is facilitated by photo-induced electronic structure modification allowing for multi-photon processes. As per the prediction of the model, we experimentally show that graphite upconverts infrared light centered around 1.31 μm to broadband white light centered around 0.85 μm. Our results suggest that upconversion from shortwave infrared (∼3 μm) to visible region may be possible. Our experiments show that the population dynamics of the electronic states involved in this upconversion process occur in the timescale of milliseconds.

Low-density nanostructured foams are often limited in applications due to their low mechanical and thermal stabilities. Here we report an approach of building the structural units of three-dimensional (3D) foams using hybrid two-dimensional (2D) atomic layers made of stacked graphene oxide layers reinforced with conformal hexagonal boron nitride (h-BN) platelets. The ultra-low density (1/400 times density of graphite) 3D porous structures are scalably synthesized using solution processing method. A layered 3D foam structure forms due to presence of h-BN and significant improvements in the mechanical properties are observed for the hybrid foam structures, over a range of temperatures, compared with pristine graphene oxide or reduced graphene oxide foams. It is found that domains of h-BN layers on the graphene oxide framework help to reinforce the 2D structural units, providing the observed improvement in mechanical integrity of the 3D foam structure.

There is a need to classify and standardize graphene-related materials giving the growing use of this materials industrially. One of the most used and more difficult to classify is graphene oxide (GO). Inconsistent definitions of GO, closely relating it to graphene, are found in the literature and industrial brochures. Hence, although they have very different physicochemical properties and industrial applications, commonly used classifications of graphene and GO definitions are not substantial. Consequently, the lack of regulation and standardization create trust issues among sellers and buyers that impede industrial development and progress. With that in mind, this study offers a critical assessment of 34 commercially available GOs, characterized using a systematic and reliable protocol for accessing their quality. We establish correlations between GO physicochemical properties and its applications leading to rationale for its classification.

There is a need to classify and standardize graphene-related materials giving the growing use of this materials industrially. One of the most used and more difficult to classify is graphene oxide (GO). Inconsistent definitions of GO, closely relating it to graphene, are found in the literature and industrial brochures. Hence, although they have very different physicochemical properties and industrial applications, commonly used classifications of graphene and GO definitions are not substantial. Consequently, the lack of regulation and standardization create trust issues among sellers and buyers that impede industrial development and progress. With that in mind, this study offers a critical assessment of 34 commercially available GOs, characterized using a systematic and reliable protocol for accessing their quality. We establish correlations between GO physicochemical properties and its applications leading to rationale for its classification. Graphene oxide (GO) is a member of a family of two-dimensional (2D) materials, derived from the oxidation of 2D graphitic structures (sp 2 to sp 3 carbon conversion). As any other 2D material, in powder form GO presents a statistical nature in terms of its thickness and lateral size distribution. However, GO is an amorphous and nonstoichiometric 2D material, bearing a blend of different functional oxygen groups 1. In fact, there is no consensus on how to represent the structural model for GO. Hence, important structural details are often neglected, including metallic impurities, functional groups of other heteroatoms, carbon vacancies and radicals, and C-H bonds, which directly depend on the oxidation method used 2. There is a plethora of methods available to obtain GO, including the chemical, electrochemical and microbial oxidation of a variety of carbon-based materials 3-6. The most common results found in the literature involve GO obtained via chemical oxidation of graphite or, most recently, the direct fast oxidation of graphene 7. However, when considering commercially available GO, it narrows down to the almost exclusive use of chemically oxidized graphite. Graphite oxidation dates back to 1859 when Benjamin Brodie developed the so-called graphic acid 8. Later many different approaches were developed aiming to improve Brodie's method 2,9. These modifications always involve the addition of a new reactant that leaves its physical footprint in terms of residues and defects that consequently affects GO's applicability 10. For instance, the methods developed by Staudenmaier 11 and Hofmann 12 methods optimize Brodie's approach with the use of potassium chlorate (KClO 3) and nitric acid (HNO 3). On the other hand, the vastly used Hummers method 13 applies a mixture of sulfuric acid, sodium nitrate, and potassium permanganate (KMnO 4) to graphite, yielding materials with very different electrochemical properties than the ones obtained by the other aforementioned methods 14. This issue is further aggravated by the fact that graphene and GO, in low dose, are not toxic per se, but their cytotoxicity emerges from defects and contaminants 15. In this article we survey the overall reliability and consistency of commercially available GO from producers around the world. The closest standardized characterization protocol available for GO is the ISO/TS 21356-1:2021 16 that was developed for graphene and, with few exceptions 17-19 , no adaptation was tried for GO. Moreover, most of the literature focuses on identifying specific phenomena for small sets of samples. Therefore, we propose a guideline for sample preparation and characterization, including a flowchart that combines up-to-date laboratory common practices for GO characterization (Supplementary Information, SI, Figure S1). Detailed experimental

The effect of air exposure on 2H-WSe 2 /HOPG is determined via scanning tunneling microscopy (STM). WSe 2 was grown by molecular beam epitaxy on highly oriented pyrolytic graphite (HOPG), and afterward, a Se adlayer was deposited in situ on WSe 2 /HOPG to prevent unintentional oxidation during transferring from the growth chamber to the STM chamber. After annealing at 773 K to remove the Se adlayer, STM images show that WSe 2 layers nucleate at both step edges and terraces of the HOPG. Exposure to air for 1 week and 9 weeks caused air-induced adsorbates to be deposited on the WSe 2 surface; however, the band gap of the terraces remained unaffected and nearly identical to those on decapped WSe 2. The air-induced adsorbates can be removed by annealing at 523 K. In contrast to WSe 2 terraces, air exposure caused the edges of the WSe 2 to oxidize and form protrusions, resulting in a larger band gap in the scanning tunneling spectra compared to the terraces of air-exposed WSe 2 monolayers. The preferential oxidation at the WSe 2 edges compared to the terraces is likely the result of dangling edge bonds. In the absence of air exposure, the dangling edge bonds had a smaller band gap compared to the terraces and a shift of about 0.73 eV in the Fermi level toward the valence band. However, after air exposure, the band gap of the oxidized WSe 2 edges became about 1.08 eV larger than that of the WSe 2 terraces, resulting in the electronic passivation of the WSe 2 .

The present paper describes a new approach to synthesize and apply reduced graphene oxide/tin oxide (rGO/SnO2) nanocomposite as an electro-conductive and ultraviolet (UV) blocking structure on the surface of polyethylene terephthalate (PET) fabric through in-situ consecutive reactions. In this research, SnCl2 was used as reducing agent to reduce GO and also precursor to synthesize SnO2 nanoparticles. XRD and FTIR patterns and FESEM images showed good activities of SnCl2 to reduce GO and also synthesize SnO2 nanoparticles on the surface of rGO nanosheets. The electrical resistivity decreased from an insulator to an 2 electro-conductive fabric (PET/rGO/SnO2= 480 Ω.cm) in low content of nanocomposite, 0.2 wt%. The ultraviolet protection factor (UPF) and transmittance values indicated an excellent ultraviolet blocking behavior after 10 washes. The UPF values increased from 33.5 for PET to 216.9 for PET/rGO/SnO2 fabric. Highlights: 1-A new method to low temperature synthesis of rGO/SnO2nanocomposite on the surface of PET fabric based on in-situ consecutive reactions 2-Production of electro-conductive (480 Ω.cm) and UV blocking (216.9) textile in low amount of GO (0.2% w/w) 3-Application of SnCl2 as a reducing agent to reduce GO and precursor to synthesize SnO2 nanostructures at the same time 4-Production of a durable nanostructure (rGO/SnO2) on the surface of PETfabric

We demonstrate a bottom-up synthesis of structures similar to graphene oxide via a two dimensional polymerization. Experimental evidence and discussion are conveyed as well as a general framework for this two dimensional polymerization. The proposed morphologies and lattice structures of these graphene oxides are derived from aldol condensation of alternating three nucleophilic and three electrophilic centers of benzenetriol.

Electrochemically exfoliated graphene is functionalized graphene with potential application in biomedicine. Two most relevant biological features of this material are its electrical conductivity and excellent water dispersibility. In this study we have tried to establish the correlation between graphene structure and its antibacterial properties. The exfoliation process was performed in a two electrode-highly oriented pyrolytic graphite electrochemical cell. Solution of ammonium persulfate was used as an electrolyte. Exfoliated graphene sheets were dispersed in aqueous media and characterized by atomic force microscopy, scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, X photoelectron spectroscopy, X-ray diffraction, electron paramagnetic resonance, zeta potential, contact angle measurements and surface energy. Antibacterial assays have shown lack of the significant antibacterial activity. Major effect on bacteria was slight change of bacteri...

The paper reported the Ni-Co oxide/electrochemically exfoliated graphene nanocomposites with 3D porous nano-architectures (NC-EEG) using a simple low temperature solution Highlights  A simple low temperature solution method was used for preparing NC-EEG.  Graphene sheets were obtained by electrochemically exfoliation process.  A high capacity of NC-EEG in a three-electrode system, as high as 649 C g-1 , was recorded.  Asymmetric supercapacitor based on NC-EEG exhibited excellent energy density and power density.

This book chapter concentrates on energy storage applications of thin film containing electrochemical capacitors (supercapacitors) with specifically high-temperature polymers (fluorinated polymers, polyimides, polyarylenes, polyvinyl pyrollidone, etc.) for their good thermal and hydrolytic stability, excellent mechanical and chemical stability, low cost, flexibility and commercial availability. It consists of three main parts as given in the table of contents related to the 1) fluorinated high-performance polymers (FHPP) 2) nonfluorinated high-performance polymers (NFHPP) and 3) fluorinated and nonfluorinated high-performance polymers (FNFHPP) with their composites. A total of 141 literature reviewed references are cited.

Tujuan penelitian ini adalah menganalisa kerusakan struktur pada lapisan tipis graphene oxide setelah direduksi pada temperatur reduksi yang bervariasi. Lapisan tipis graphene oxide yang disintesis menggunakan metode Hummers direduksi secara termal pada variasi temperatur 350 0 C dan 850 0 C selama 2 jam dalam pemanas vakum (~10-3 Torr). Kuantitas defect sampel dikarakterisasi menggunakan Raman Spectroscopy sedangkan mikrostrukturnya dikarakterisasi menggunakan SEM (Scanning Electron Microscope). Persentase (kuantitas) defect pada graphene oxide dinyatakan dengan ID/IG. Nilai ID/IG graphene oxide, graphene oxide tereduksi pada temperatur 350 0 C dan 850 0 C secara berurutan adalah 0.958, 0.823 dan 1.102. Nilai ID/IG tersebut menunjukkan bahwa kuantitas defect graphene oxide berkurang setelah direduksi pada suhu 350 0 C tetapi bertambah saat direduksi pada suhu 850 0 C. Hasil gambar SEM menunjukkan bahwa lapisan tipis graphene oxide menkerut setalah direduksi pada temperatur 350 0 C dan berubah menjadi material seperti graphite berpori (porous stacked-layer graphite) setelah direduksi pada temperatur 850 0 C. Kata-kata kunci: graphene oxide tereduksi, reduksi termal, kerusakan struktur.

In this study graphene oxide (GO) synthesized by modified Hummer's method. Surface of GO was modified with biopolymer chitosan (CS) and then grafted with the ZnO nanoparticles. GO/ZnO/CS was investigated as adsorbent for the elimination of Pb (II) and Cr (VI) ions from aqueous solutions. The Box-Behnken Design (BBD) within the framework of response surface methodology (RSM) was employed to optimize different parameters, which including pH of the metal solution, initial metal ions concentration and contact time. The quadratic model was best fitted for characterizing the influence of adsorption parameters on adsorption capacity (q e) and percent removal (% R), exhibiting strong statistical support with R 2 values and p-values. To explore the interactions between these parameters and determine the ideal conditions for removing Pb (II) and Cr (VI) ions, we employed second-order polynomial equations, performed analysis of variance (ANOVA), and generated three-dimensional surface plots. The optimum parameters for Pb (II) ions were pH 5, initial concentration 60 mg/L and 120 min contact time, with 110.88 mg/g adsorption capacity and 92.4 % removal efficiency. For Cr (VI) ions 84.5 mg/g adsorption capacity and 70.5 % removal was achieved at pH 2, 60 mg/L metal concentration at 112 min contact time.

Modeling is a crucial step in database modeling, as it helps define the model, which serves as a guide for good implementation. The quality of the model determines the outcome. Hence, normalization is applied for that purpose to validate the model. In addition, in the database modeling and management process, the organization, case study, provides rules of management that give a global view, allowing analysts to obtain a model, that is not always the optimal one. As a result, validation must be performed to optimize the model and efficiently respond to the users' needs. Moreover, in the Democratic Republic of Congo, two schools of thought among scholars exist in which one supports conceptual validation, while the other supports logical validation. This article aims to compare these trends and suggest best practices after scientific reflection. Findings show that logical validation has limitations in obtaining a coherent and implementable model compared to conceptual validation in some cases of study while conceptual validation responds in almost all problems implying validation for the database design.

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The continuous tuning of the emission spectrum of a single light-emitting diode (LED) by an external electrical bias is of great technological significance as a crucial property in high-quality displays, yet this capability has not been demonstrated in existing LEDs. Graphene, a tunable optical platform, is a promising medium to achieve this goal. Here we demonstrate a bright spectrally tunable electroluminescence from blue (∼450 nm) to red (∼750 nm) at the graphene oxide/reduced-graphene oxide interface. We explain the electroluminescence results from the recombination of Poole-Frenkel emission ionized electrons at the localized energy levels arising from semi-reduced graphene oxide, and holes from the top of the π band. Tuning of the emission wavelength is achieved by gate modulation of the participating localized energy levels. Our demonstration of current-driven tunable LEDs not only represents a method for emission wavelength tuning but also may find applications in high-qualit...