Hexagonal Graphite Structure Research Articles

Multipurpose biological applications of excitation-dependent fluorescent carbon nano dots emanated from biomass waste

Carbon Nanodots (CNDs) generated from biomass wastes have a wide range of biological functionalities and are used in a variety of applications. Especially, the biomedical applications shown by the CNDs derived from biomass waste materials received great attention from researchers around the globe. Herein we report the synthesis of CNDs from rice husk biomass waste using a hydrothermal method. XRD pattern demonstrates the amorphous nature of CNDs with hexagonal graphite structure. Microscopic images confirmed that as-synthesized CNDs are in spherical morphology with an average size of 25–30 nm and average interplanar spacing of 0.265 nm. XPS, Raman, and FTIR spectral analyses were performed to examine the presence of functional groups and defects in CNDs. Excitation-dependent emission properties of CNDs (ФF 9.6%) were studied by UV–Vis., Contour, and fluorescence techniques. In response to the findings of the cytotoxicity experiment and the CNDs' strong emission, we carried out several biostudies to prove its importance. The CNDs possess outstanding cell viability (98%), excellent anti-inflammatory activity of 33% of LOX, 34% of COX, 45% of NO inhibition at 100 μL, significant protein denaturation (62%; IC50 20.04 μL/mL), and bright bioimaging on Zebrafish characteristics, which accentuate the perception of waste to wealth.

A new paradigm in biosensing: MOF-carbon dot conjugates

Metal-organic frameworks (MOFs) have emerged as promising nanocarriers for targeted drug delivery, owing to their unique structural properties and tunable pore sizes. Integrating carbon dots (C-dots) into MOFs will further enhance their functionality and imaging capabilities. In this study, the synthesis and characterization of C-dots loaded MOF is detailed as a novel pH and temperature-responsive nanoplatform for the imaging and therapy of neuroblastoma. The C-dots were synthesized using a modified microwave method, and their structural and optical properties were characterized using techniques such as XRD, FTIR, and XPS. The C-dots demonstrated a hexagonal graphite structure with hydroxyl and carboxyl surface functional groups. The C-dots also exhibited green emission under excitation at 405 nm with concentration-dependent emission behaviour. The pH-dependent emission studies reveal a gradual increase in fluorescence intensity from pH 3–9, followed by a rapid decrease at higher pH values. It is observed that the fluorescence intensity decreased by ∼50% upon increasing the temperature (30–65 °C) at a step of 5 °C covering the range of physiological temperature. The photothermal studies elucidated that the C-dots exhibit good photothermal conversion properties upon NIR laser irradiation that can find applications in the areas like photothermal therapy. The drug release studies confirmed the pH-responsive drug release property of the nanocomposite. Further, the surface-modified nanocomposite was efficiently uptaken by the neuroblastoma cells suggesting the possibility of targeted therapy for cancer. Overall, this study gives new insights into the synthesis, characterisation, and functionalization of C-dots loaded with ZIF-8 NPs, revealing their potential for drug delivery applications.

EMI shielding performance of electroless coated iron nanoparticles on graphite in low-density polyethylene composite for X-band applications

In the proposed work, an investigation of shielding effectiveness (SE) for varying compositions of Graphene, Multiwall carbon nanotubes (MWCNT), and Iron nanoparticles coated on Graphite (Fe@Graphite) was conducted in X-band (8.2 GHz–12.4 GHz). All these are mixed in an LDPE matrix. The nanomaterial was subjected to chemical characterization, i.e., Scanning electron microscopy (SEM), X-ray diffraction (XRD), and vibrating sample magnetometry (VSM). The shielding observed is dominantly due to absorption. The lattice structure which facilitates the shielding due to absorption was the hexagonal graphite structure on whose surface iron nanoparticles were embedded and used as the magnetic filler. At the same time, Graphene and MWCNT act as electrically conducting fillers. The Total shielding effectiveness(SET) was maximum for LDPE, MWCNT, Graphene, and Fe@Graphite, in the ratio of 50: 5: 25: 20 by weight %, and is 49 dB at 9.65 GHz for a sample thickness of 3 mm.

In English

Carbon nanostructures (CNS) were synthesized by the electric arc plasma chemical method during the evaporation of a high-quality graphite electrode of the brand “fine-grained dense graphite” (FGDG-7) filled with a catalyst (Pt), which was evaporated in a helium environment. In the synthesis process, the following were synthesized: multi-walled (MWCNT) and single-walled carbon nanotubes (SWCNT), fullerenes, graphene packets and nanocomposites. A deposit in the form of growth on the cathode electrode was also synthesized. All synthesis products were analyzed at the micro- and nanolevels, which made it possible to analyze the influence of platinum vapors on the formation of carbon nanomaterials (CNM). The non-uniform distribution of catalyst atoms (platinum) in the products of electrochemical synthesis in a gas medium using FGDG-7 graphite was investigated. During the analysis, it was found that platinum is in the state of the face-centered cubic (FCC) lattice and is distributed in the synthesis products as follows: the core of the deposit is less than < 0.001 %, the shell of the deposit is less than < 1 %, the wall soot is more than > 1 %. The morphology and composition of the platinum deposit, which has a hexagonal graphite structure with an admixture of a rhombohedral graphite phase, was studied. In the studies, differential thermal analysis in air (TG, DTG, DTA) was carried out, which made it possible to identify the composition of the synthesis products. It is an established fact that the parts of the deposit with platinum are more heat-resistant compared to the deposit components that do not contain Pt. The resulting carbon nanotubes (CNTs) in diameter (5–25 nm) and length (1.5–2 μm) do not differ from those obtained without the participation of platinum, except for some anomalies. When studying the suitability of platinum-containing carbon nanostructures for 3D printing of CJP (ceramic printing) technology, it was found that for the use of platinum-containing carbon black, it is necessary to carry out a preliminary short-term treatment, namely, grinding in special “ball mills” or rubbing through a fine sieve with minimal effort to create uniformity product. Previous studies have shown that such platinum-containing carbon nanostructures can already be used in 3D printing of CJP technology, or to create new composites for 3D printing technologies of FDM, SLA.

Preparation of a Composite of Copper Oxide Nanoparticles with Carbon by Exploding Graphite Rod in Aqueous Suspension

In this work, the effect of preparing a composite of copper oxide nanoparticles with carbon on some of its optical properties was studied. The composite preparing process was carried out by exploding graphite electrodes in an aqueous suspension of copper oxide. The properties of the plasma which is formed during the explosion were studied using emission spectroscopy in order to determine the most important elements that are present in the media. The electron’s density and their energy, which is the main factor in the composite process, were determined. The particle properties were studied before and after the exploding process. The XRD showed an additional peak in the copper oxides pattern corresponding to the hexagonal graphite structure for the composite. The UV-visible absorbance for the composite was significantly enhanced. The direct bandgap decreased from 2.55 to 2.4 eV, and the indirect bandgap decreased from 1.1 to 1 eV, for the composite.

The utilization of waste cooking palm oil as a green carbon source for the growth of multilayer graphene

Waste cooking palm oil (WCPO) has been utilized as a green carbon source for the synthesization of graphene by double thermal chemical vapor deposition. The WCPO was placed in the first furnace (precursor furnace) whereas nickel was placed in the second furnace (deposition furnace). The deposition temperatures were varied between 850 and 1100 °C. Raman results reveal the highest 2-D peak for the sample synthesized at 1000 °C, which indicates the high-quality formation of graphene. Besides, the sample also shows good crystallinity with a sharp peak at 26.8° which represents the hexagonal graphite structure and the introduction of graphene sheet formation. On the other hand, the FESEM image displays hexagonal structures since the graphene layers were formed after the precipitation of the carbon. Meanwhile, the UV-Vis result shows the highest reflectance in the visible light region which indicates the presence of the graphene layer on Ni.

Synthesis of Carbon Nanotubes and Nanospheres from Coconut Fibre and the Role of Synthesis Temperature on Their Growth

Carbon nanotubes (CNT) and carbon nanospheres were successfully synthesized from coconut fibre-activated carbon. The biomass was first carbonized then physically activated, followed by treatment using ethanol vapor at 700°C to 1100°C at 100°C intervals. The effect of synthesis temperature on the formation of the nanomaterials was studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray spectrometry, x-ray diffraction (XRD), Fourier transform infrared microscopy (FTIR) and thermogravimetric analysis. SEM analysis revealed that nanospheres were formed at higher temperatures of 1000°C and 1100°C, while lower temperatures of 800°C and 900°C favored the growth of CNT. At 700°C, however, no tubes or spheres were formed. TEM and FTIR were used to observe spectral features, such as the peak positions, intensity and bandwidth, which are linked to some structural properties of the samples investigated. All these observations provided facts on the nanosphere and nanotube dimensions, vibrational modes and the degree of purity of the obtained samples. The TEM results show spheres of diameter in the range 50 nm to 250 nm while the tubes had diameters between 50 nm to 100 nm. XRD analysis reveals the materials synthesized are amorphous in nature with a hexagonal graphite structure.

Characterization Studies of Cyclotron CS-30 Carbon Puller Material Using Powder X-Ray Diffraction and SEM, EDX Cross Section Method

The carbon puller material of Cyclotron CS-30 has been characterized to investigate the structure and composition of the puller. Two samples of pullers have been prepared in the form of powder from locally made carbon and the original cyclotron puller. X-ray diffraction (XRD) analysis of both samples powder gives identification of the structure and phase type of carbon, meanwhile the morphology and the elemental composition of both samples can be shown by Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDX) technique. XRD samples are prepared by grinding the puller surface meanwhile the samples for SEM analysis are prepared by cross section method. XRD result shows amorphous carbon structure and a typical broad XRD profile’s peaks and the diffused nature of the XRD profile indicate the presence of disorder in the samples. The first peak of the profile corresponds to the (002) peak of the hexagonal graphite structure, while the second peak corresponds to the (100) and (101) for both samples. Results of SEM-EDX showed that the carbon material from the original default puller of the CS-30 cyclotron contains mass percentage of lead significantly by 9.15%.

Botanical Hydrocarbon Sources based MWCNTs Synthesized by Spray Pyrolysis Method for DSSC Applications

The present study aims to synthesize corrosion free counter electrodes for DSSC and evaluate their efficiency in comparison with carbon electrodes. We compare the PCE (Power Conversion Efficiency) of a MWCNT counter electrode DSSC with a carbon coated counter electrode DSSC. MWCNTs are prepared by a spray pyrolysis method and TiO2 nanoparticles are prepared by aWCT (Wet Chemical Technique). XRD analysis for TiO2 2θ = 25.3 shows the presence of anatase phase and 2θ = 25.9 shows the hexagonal graphite structure ofMWCNTs. SEM images of TiO2 nanoparticles show irregular morphology and for MWCNTs, the SEM image shows the formation of MWCNTS. The exact grain size ofMWCNTs and TiO2 nanoparticles are studied by TEM analysis. In the DSSC application, MWCNTs coated the DSSC show higher efficiency (2.5 %) than carbon coated DSSC (1.9 %).

Influence of Rhombohedral Graphite Phase on the Diamond Nucleation

The high pressure and temperature, synthesis of diamond from carbonaceous materials, is a complex process highly dependent on variables such as the catalyst/solvent, the crystalline structure of the precursor material, the processing conditions and the type of compressive chamber. The optimum susceptible precursors to be transformed into diamond are those possessing the perfect hexagonal graphite structure, which is the thermodynamically most stable form of carbon at atmospheric pressure and ambient temperature. However, the majority of both industrial and natural graphites, presents a mixture of different atomic structural arrangements that greatly influence the process of diamond synthesis. In this works the influence of rhombohedral and hexagonal phases existing in the graphite was performed by means of a software refinement of the crystal structures using the Rietveld method. The thermobaric treatment, which determine the structural parameters, was conducted in a high pressure anvil type device with a central concavity. All experiments were carried out at 1200°C and pressures varying from 4.3 to 5.0 GPa. It was determined that the degree of graphite to diamond transformation is directly associated with the content of rhombohedral phase.

Study on the giant positive magnetoresistance and Hall effect in ultrathin graphite flakes

AbstractIn this paper, we report on the electronic transport properties of mesoscopic, ultrathin graphite flakes with a thickness corresponding to a stack of 150 graphene layers. The graphite flakes show an unexpectedly strong positive magnetoresistance (PMR) already at room temperature, which scales in good approximation with the square of the magnetic field. Furthermore, we show that the resistivity is unaffected by magnetic fields oriented in plane with the graphene layers. Hall effect measurements indicate that the charge carriers are p‐type and their concentration increases with increasing temperature while the mobility is decreasing. The Hall voltage is non‐linear in higher magnetic fields. Possible origins of the observed effects are discussed.magnified image Ball and stick model of the two topmost carbon layers of the hexagonal graphite structure.

Sn–Co–artificial graphite composite as anode material for rechargeable lithium batteries

Nanosized Sn–Co prepared by ultrasonic-assisted chemical reduction is milled with artificial graphite (AG) to form Sn–Co–AG composite. The as-prepared materials are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectrometry and Brunauer–Emmett–Telle (BET) surface area measurement. XRD patterns show that Sn–Co particles are poorly crystallized and artificial graphite has a typical hexagonal graphite structure phase. The diffraction peaks of Sn–Co particles remain the same but some of AG obviously change after milling Sn–Co with AG. BET areas of AG, Sn–Co and Sn–Co–AG are 1.569, 13.187 and 6.754 m 2 g −1, respectively. SEM images display the as-prepared Sn–Co particles have a size distribution ranging from 20 to 70 nm in diameter. After milling Sn–Co with AG, Sn–Co particles keep similar morphology but there is a perceptible change in AG. Electrochemical tests show that Sn–Co–AG composite possesses much improved electrochemical performance than the state-of-the-art graphite. This composite has great potential as an alternative material for improving the energy density of a lithium ion secondary battery.

Grazing incidence X-ray diffraction study on carbon nanowalls

The growth and structure of carbon nanowalls (CNWs) on the substrate were investigated by grazing incidence X-ray diffraction. Fully-grown CNWs have a single phase of hexagonal graphite structure with relatively high degree of graphitization as the graphite powder. The preferred orientation of graphene layers is perpendicular to the substrate surface. At the initial growth state, the graphene layers are horizontally oriented. At the critical deposition time for changing the orientation, some diffraction peaks which cannot be assigned to the hexagonal graphite structure are observed. These peaks suggest the formation of a carbon allotrope which should contribute to the turning of the orientation of graphene layers.

Experimental study on the hydrogen storage and release in nano-graphite synthesized by explosive detonation

In this article, synthesis of nanographite powders using pure TNT ( trinitrotoluene )explosives is reported. X-ray Diffraction (XRD) results indicated that the detonation product has a hexagonal-graphite structure and the average size of the particles of graphite is 1.86—2.61nm. Specific surface area of nano-graphite is about 500—650m2/g measured by BET gas sorption instrument.Crystal grain size of the nano-graphite calculated is 4.41—6.85nm by its specific surface area. A hydrogen storage and release capacity of 0.33—0.37 weight at room temperature under a modestly high pressure (12MPa) for untreated nano-graphte samples synthesized under different conditions. Under the same condition, the capacity of hydrogen storage and release of untreated carbon nanofibers、multi walled carbon nanotubes and superactive carbon is 0.15wt%—0.35wt％，0.15wt%—0.20wt％，0.92wt%—0.98wt％，respectively.The specific surface area of carbon nanostructured materials is the most important factor in its hydrogen storage and release.

Nano-graphite synthesized by explosive detonation and its application in preparing diamond under high-pressure and high-temperature

In this article, preparation of nano-graphite powders in a steel chamber by using pure TNT (trinitrotoluene) explosives has been reported. X-ray diffraction results indicated that the black solid powders which were collected from the wall and the bottom of the chamber after detonation have the graphite structure and the average size of the particles of the graphite is 1.86-2.58 nm. Transmission electron microscopy confirms that the black powder is hexagonal-graphite structure with ball or ball-like shape. The grain size of the nano-graphite measured by small angle x-ray scattering lies in the range of 1-50 nm, 92.6wt% of the powder particles is smaller than 16 nm and the average diameter of the grains is 8.7 nm. Specific surface area of the nano-graphite is about 500-650 m2/g. Using nano-graphite as carbon source and choosing Fe powders as the catalyst, the ball-like and lumpy diamonds of 5-15 μm have been synthesized under high-temperature and high-pressure conditions of 1250-1330 K and 5.1 GPa. The synthesized temperature is about 300 K lower than that of bulk graphite synthetic diamond.

Laser synthesis of carbon-rich SiC nanoribbons

A nanosecond pulsed laser direct-write and doping (LDWD) technique is used for the fabrication of carbon-rich silicon carbide nanoribbons heterostructure in a single crystal 4H–SiC wafer. Characterization by high-resolution transmission electron microscope and selected area electron diffraction pattern revealed the presence of nanosize crystalline ribbons with hexagonal graphite structure in the heat-affected zone below the decomposition temperature isotherm in the SiC epilayer. The nanoribbons exist in three layers each being approximately 50–60 nm thick, containing 15–17 individual sheets. The layers are self-aligned on the (0001) plane of the SiC epilayer with their c axis at 87° to the incident laser beam. The LDWD technique permits synthesis of heterostructured nanoribbons in a single step without additional material or catalyst, and effectively eliminates the need for nanostructure handling and transferring processes.

Neutron transmission measurements of poly and pyrolytic graphite crystals

The total neutron cross-section measurements of polycrystalline graphite have been carried out in a neutron wavelength from 0.04 to 0.78 nm. This work also presents the neutron transmission measurements of pyrolytic graphite (PG) crystal in a neutron wavelength band from 0.03 to 0.50 nm, at different orientations of the PG crystal with regard to the beam direction. The measurements were performed using three time-of-flight (TOF) spectrometers installed in front of three of the ET-RR-1 reactor horizontal channels. The average value of the coherent scattering amplitude for polycrystalline graphite was calculated and found to be b coh = (6.61 ± 0.07) fm. The behaviour of neutron transmission through the PG crystal, while oriented at different angles with regard to the beam direction, shows dips at neutron wavelengths corresponding to the reflections from (hkl) planes of hexagonal graphite structure. The positions of the observed dips are found to be in good agreement with the calculated ones. It was also found that a 40 mm thick PG crystal is quite enough to reduce the second-order contamination of the neutron beam from 2.81 to 0.04, assuming that the incident neutrons have a Maxwell distribution with neutron gas temperature 330 K.

A study of the negative magnetoresistance in pyrocarbons

Abstract An exhaustive experimental investigation of a series of non-crystalline pyrocarbons has been carried out. In addition to the electrical resistivity, the Hall effect and the positive magnetoresistanoe, the negative magnetoresistance has been especially examined. This effect has been measured as a function of several parameters: temperature (300—1·5 K) magnetic field strength (0·25—60 kgauss) and sample orientation in the magnetic field. It has been shown that the negative component disappears progressively when the crystallinity of the sample increases towards the hexagonal graphite structure, that this component is anisotropic and behaves like a tensor quantity, and that there is no additivity law between the positive and the negative components. A tentative interpretation based on the existence of a pseudo energy gap between the valence and the conduction II bands has not been quantitatively successful. From an empirical analysis, a classification of the different magneto - resistance effects ha...

Etude de la cinetique de guerison des defauts crees dans un graphite par broyage

A study of conversion of rhombohedral sequences into hexagonal graphite structure was carried out in order to clarify the role of defects in the transformation G Rh → G Hex . We have shown that, the fraction of rhombohedral graphite transformed at a given temperature of anneal into hexagonal graphite depends on the residence time. It seems that under continuous grinding some rhombohedral structures are transformed into biperiodic, some of which in annealing revert to hexagonal via rhombohedral. The results give good information about the existence of rhombohedral sequences which are involved in the graphitization process.