Research

9 pages, 3471 KiB

Open AccessArticle

Antibacterial Electroconductive Composite Coating of Cotton Fabric

by Tomasz Makowski, Mariia Svyntkivska, Ewa Piorkowska, Urszula Mizerska, Witold Fortuniak, Dorota Kowalczyk, Stefan Brzezinski and Dorota Kregiel

Materials 2022, 15(3), 1072; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15031072 - 29 Jan 2022

Cited by 14 | Viewed by 3289

Abstract

Graphene oxide (GO) was deposited on a cotton fabric and then thermally reduced to reduced graphene oxide (rGO) with the assistance of L-ascorbic acid. The GO reduction imparted electrical conductivity to the fabric and allowed for electrochemical deposition of Ag° particles using cyclic [...] Read more.

Graphene oxide (GO) was deposited on a cotton fabric and then thermally reduced to reduced graphene oxide (rGO) with the assistance of L-ascorbic acid. The GO reduction imparted electrical conductivity to the fabric and allowed for electrochemical deposition of Ag° particles using cyclic voltammetry. Only the Ag°/rGO composite coating imparted antibacterial properties to the fabric against Escherichia coli and Staphylococcus aureus. Ag°/rGO-modified fibers were free of bacterial film, and bacterial growth inhibition zones around the material specimens were found. Moreover, Ag°/rGO-modified fabric became superhydrophobic with WCA of 161°. Full article

(This article belongs to the Special Issue Nanocarbon Based Composites)

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17 pages, 1562 KiB

Open AccessArticle

Through-Plane and In-Plane Thermal Diffusivity Determination of Graphene Nanoplatelets by Photothermal Beam Deflection Spectrometry

by Humberto Cabrera, Dorota Korte, Hanna Budasheva, Behnaz Abbasgholi N. Asbaghi and Stefano Bellucci

Materials 2021, 14(23), 7273; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14237273 - 28 Nov 2021

Cited by 12 | Viewed by 2025

Abstract

In this work, in-plane and through-plane thermal diffusivities and conductivities of a freestanding sheet of graphene nanoplatelets are determined using photothermal beam deflection spectrometry. Two experimental methods were employed in order to observe the effect of load pressures on the thermal diffusivity and [...] Read more.

In this work, in-plane and through-plane thermal diffusivities and conductivities of a freestanding sheet of graphene nanoplatelets are determined using photothermal beam deflection spectrometry. Two experimental methods were employed in order to observe the effect of load pressures on the thermal diffusivity and conductivity of the materials. The in-plane thermal diffusivity was determined by the use of a slope method supported by a new theoretical model, whereas the through-plane thermal diffusivity was determined by a frequency scan method in which the obtained data were processed with a specifically developed least-squares data processing algorithm. On the basis of the determined values, the in-plane and through-plane thermal conductivities and their dependences on the values of thermal diffusivity were found. The results show a significant difference in the character of thermal parameter dependence between the two methods. In the case of the in-plane configuration of the experimental setup, the thermal conductivity decreases with the increase in thermal diffusivity, whereas with the through-plane variant, the thermal conductivity increases with an increase in thermal diffusivity for the whole range of the loading pressure used. This behavior is due to the dependence of heat propagation on changes introduced in the graphene nano-platelets structure by compression. Full article

(This article belongs to the Special Issue Nanocarbon Based Composites)

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13 pages, 2554 KiB

Open AccessArticle

Behavior of the Energy Spectrum and Electric Conduction of Doped Graphene

by Stefano Bellucci, Sergei Kruchinin, Stanislav P. Repetsky, Iryna G. Vyshyvana and Ruslan Melnyk

Materials 2020, 13(7), 1718; https://0-doi-org.brum.beds.ac.uk/10.3390/ma13071718 - 06 Apr 2020

Cited by 7 | Viewed by 2041

Abstract

We consider the effect of atomic impurities on the energy spectrum and electrical conductance of graphene. As is known, the ordering of atomic impurities at the nodes of a crystal lattice modifies the graphene spectrum of energy, yielding a gap in it. Assuming [...] Read more.

We consider the effect of atomic impurities on the energy spectrum and electrical conductance of graphene. As is known, the ordering of atomic impurities at the nodes of a crystal lattice modifies the graphene spectrum of energy, yielding a gap in it. Assuming a Fermi level within the gap domain, the electrical conductance diverges at the ordering of graphene. Hence, we can conclude about the presence of a metal–dielectric transition. On the other hand, for a Fermi level occurring outside of the gap, we see an increase in the electrical conductance as a function of the order parameter. The analytic formulas obtained in the Lifshitz one-electron strong-coupling model, describing the one-electron states of graphene doped with substitutional impurity atoms in the limiting case of weak scattering, are compared to the results of numerical calculations. To determine the dependence of the energy spectrum and electrical conductance on the order parameter, we consider both the limiting case of weak scattering and the case of finite scattering potential. The contributions of the scattering of electrons on a vapor of atoms to the density of states and the electrical conductance of graphene with an admixture of interstitial atoms are studied within numerical methods. It is shown that an increase in the electrical conductance with the order parameter is a result of both the growth of the density of states at the Fermi level and the time of relaxation of electron states. We have demonstrated the presence of a domain of localized extrinsic states on the edges of the energy gap arising at the ordering of atoms of the admixture. If the Fermi level falls in the indicated spectral regions, the electrical conductance of graphene is significantly affected by the scattering of electrons on clusters of two or more atoms, and the approximation of coherent potential fails in this case. Full article

(This article belongs to the Special Issue Nanocarbon Based Composites)

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9 pages, 3263 KiB

Open AccessArticle

Modulating Band Gap of Boron Doping in Amorphous Carbon Nano-Film

by Rui Zhu, Qiang Tao, Min Lian, Xiaokang Feng, Jiayu Liu, Meiyan Ye, Xin Wang, Shushan Dong, Tian Cui and Pinwen Zhu

Materials 2019, 12(11), 1780; https://0-doi-org.brum.beds.ac.uk/10.3390/ma12111780 - 31 May 2019

Cited by 8 | Viewed by 2645

Abstract

Amorphous carbon (a-C) films are attracting considerable attention to due their large optical band gap (E_opt) range of 1–4 eV. But the hopping conducting mechanism of boron doping a-C (a-C:B) is still mysterious. To exploring the intrinsic reasons behind the semiconductor [...] Read more.

Amorphous carbon (a-C) films are attracting considerable attention to due their large optical band gap (E_opt) range of 1–4 eV. But the hopping conducting mechanism of boron doping a-C (a-C:B) is still mysterious. To exploring the intrinsic reasons behind the semiconductor properties of a-C:B, in this work, the boron doping a-C (a-C:B) nano-film was prepared, and the growth rate and E_opt changing were analyzed by controlling the different experimental conditions of magnetron sputtering. A rapid deposition rate of 10.55 nm/min was obtained. The E_opt is reduced from 3.19 eV to 2.78 eV by improving the substrate temperature and sputtering power. The proportion of sp²/sp³ increasing was uncovered with narrowing the E_opt. The shrinking E_opt can be attributed to the fact that boron atoms act as a fluxing agent to promote carbon atoms to form sp² hybridization at low energy. Furthermore, boron atoms can impede the formation of σ bonds in carbon atom sp³ hybridization by forming B–C bonds with high energy, and induce the sp³ hybridization transfer to sp² hybridization. This work is significant to further study of amorphous semiconductor films. Full article

(This article belongs to the Special Issue Nanocarbon Based Composites)

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12 pages, 5427 KiB

Open AccessArticle

Designing Carbon Nanotube-Based Oil Absorbing Membranes from Gamma Irradiated and Electrospun Polystyrene Nanocomposites

by Hemalatha Parangusan, Deepalekshmi Ponnamma, Mohammad K. Hassan, Samer Adham and Mariam Al Ali Al-Maadeed

Materials 2019, 12(5), 709; https://0-doi-org.brum.beds.ac.uk/10.3390/ma12050709 - 28 Feb 2019

Cited by 35 | Viewed by 3758

Abstract

Carbon-based materials are outstanding candidates for oil spill clean-ups due to their superhydrophobicity, high surface area, chemical inertness, low density, recyclability, and selectivity. The current work deals with the fabrication of membrane oil absorbents based on carbon nanotube (CNT) reinforced polystyrene (PS) nanocomposites [...] Read more.

Carbon-based materials are outstanding candidates for oil spill clean-ups due to their superhydrophobicity, high surface area, chemical inertness, low density, recyclability, and selectivity. The current work deals with the fabrication of membrane oil absorbents based on carbon nanotube (CNT) reinforced polystyrene (PS) nanocomposites by electrospinning technique. The spun membranes are also irradiated with the gamma radiation to induce enough crosslinks and thus good polymer-filler interactions. The structural, morphological, and surface properties in addition to the oil/water separation efficiency were investigated by varying the concentration of CNT and the dose of γ-irradiation. Fabricated nanofiber membranes show superior hydrophobicity and selective oil absorption at 0.5 wt.% of CNT concentration. The best mechanical properties are also obtained at this particular concentration and at 15 KGy optimum γ-irradiation dosage. The gamma irradiated PS/0.5 wt.% CNT membrane also exhibits good antibacterial effects against the bacteria, Escherichia coli, in the form of bacterial inhibition rings around the membranes. The present study thus shows the environmental applicability of the fabricated PS/CNT membranes in treating oil-contaminated water. Full article

(This article belongs to the Special Issue Nanocarbon Based Composites)

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11 pages, 6190 KiB

Open AccessArticle

Plasma Exfoliated Graphene: Preparation via Rapid, Mild Thermal Reduction of Graphene Oxide and Application in Lithium Batteries

by Zuyun Luo, Yuanyuan Li, Fangfang Wang and Ruoyu Hong

Materials 2019, 12(5), 707; https://0-doi-org.brum.beds.ac.uk/10.3390/ma12050707 - 28 Feb 2019

Cited by 8 | Viewed by 3086

Abstract

A simple, novel approach is proposed for the preparation of plasma-exfoliated graphene (PEGN) by reducing graphene oxide (GO) through a dielectric-barrier discharge (DBD) plasma treatment in a H₂ atmosphere. The surface chemistry, microstructures, and crystallinity of the prepared samples were characterized via [...] Read more.

A simple, novel approach is proposed for the preparation of plasma-exfoliated graphene (PEGN) by reducing graphene oxide (GO) through a dielectric-barrier discharge (DBD) plasma treatment in a H₂ atmosphere. The surface chemistry, microstructures, and crystallinity of the prepared samples were characterized via X-ray photoelectron spectroscopy, transmission electron microscopy, and Raman spectrometry to determine the formation mechanism of the PEGN. The results demonstrated that the prepared PEGN had only a few layers in its structure and that most of the functional groups containing oxygen on the GO surface were removed. The PEGN exhibited a considerably higher capacity, better cycling stability, and favorable electron transfer rate for use as a cathode material for lithium-ion batteries. This proposed approach is fast, convenient, and inexpensive, constituting a novel means of producing graphene. Full article

(This article belongs to the Special Issue Nanocarbon Based Composites)

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17 pages, 4318 KiB

Open AccessArticle

Transmittance and Reflectance Effects during Thermal Diffusivity Measurements of GNP Samples with the Flash Method

by Stefano Bellucci, Gianluigi Bovesecchi, Antonino Cataldo, Paolo Coppa, Sandra Corasaniti and Michele Potenza

Materials 2019, 12(5), 696; https://0-doi-org.brum.beds.ac.uk/10.3390/ma12050696 - 27 Feb 2019

Cited by 24 | Viewed by 3107

Abstract

Thermal diffusivity of GNPs (graphene nano-platelets) is an important thermo-physical property as it is useful to predict the material behavior in many heat transfer applications. GNP samples were pressed at different loads to obtain different densities, and then thermal diffusivity was measured with [...] Read more.

Thermal diffusivity of GNPs (graphene nano-platelets) is an important thermo-physical property as it is useful to predict the material behavior in many heat transfer applications. GNP samples were pressed at different loads to obtain different densities, and then thermal diffusivity was measured with the flash method. All samples were coated with a thin layer (~1 µm) of colloidal graphite (Aquadag^®) on both sides to reduce reflectance of their surfaces and consequently increase the emissivity. Carrying out measurements on both samples with and without coating, a difference between the two series of measurements was found: This is attributed to a non-negligible transmittance of the uncoated samples due to the porosity of GNPs. Furthermore, assuming a spatial distribution of the light within the samples according to the Lambert-Bougert-Beer law, the extinction coefficient of GNP at different densities has been evaluated processing experimental data with a nonlinear least square regression, (NL-LSF, nonlinear least square fitting), whose model contains the extinction coefficient as unknown. The proposed method represents a further improvement of thermal diffusivity data processing, crucial to calculate the extinction coefficient when data with and without coating are available; or to correct biased thermal diffusivity data when the extinction coefficient is already known. Moreover, reflectance effects have been highlighted comparing asymptotic temperature reached during the tests on coated and uncoated samples at different densities. In fact, the decrease of asymptotic temperature of the uncoated samples gives the percentage of the light reflected and consequently an estimate of the reflectance of the GNP surface. Full article

(This article belongs to the Special Issue Nanocarbon Based Composites)

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32 pages, 784 KiB

Open AccessArticle

Electron Transport in Carbon Nanotubes with Adsorbed Chromium Impurities

by Stanislav Repetsky, Iryna Vyshyvana, Yasuhiro Nakazawa, Sergei Kruchinin and Stefano Bellucci

Materials 2019, 12(3), 524; https://0-doi-org.brum.beds.ac.uk/10.3390/ma12030524 - 10 Feb 2019

Cited by 23 | Viewed by 3153

Abstract

We employ Green’s function method for describing multiband models with magnetic impurities and apply the formalism to the problem of chromium impurities adsorbed onto a carbon nanotube. Density functional theory is used to determine the bandstructure, which is then fit to a tight-binding [...] Read more.

We employ Green’s function method for describing multiband models with magnetic impurities and apply the formalism to the problem of chromium impurities adsorbed onto a carbon nanotube. Density functional theory is used to determine the bandstructure, which is then fit to a tight-binding model to allow for the subsequent Green’s function description. Electron–electron interactions, electron–phonon coupling, and disorder scattering are all taken into account (perturbatively) with a theory that involves a cluster extension of the coherent potential approximation. We show how increasing the cluster size produces more accurate results and how the final calculations converge as a function of the cluster size. We examine the spin-polarized electrical current on the nanotube generated by the magnetic impurities adsorbed onto the nanotube surface. The spin polarization increases with both increasing concentration of chromium impurities and with increasing magnetic field. Its origin arises from the strong electron correlations generated by the Cr impurities. Full article

(This article belongs to the Special Issue Nanocarbon Based Composites)

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11 pages, 3513 KiB

Open AccessArticle

Electrical Permittivity and Conductivity of a Graphene Nanoplatelet Contact in the Microwave Range

by Stefano Bellucci, Antonio Maffucci, Sergey Maksimenko, Federico Micciulla, Marco D. Migliore, Alesia Paddubskaya, Daniele Pinchera and Fulvio Schettino

Materials 2018, 11(12), 2519; https://0-doi-org.brum.beds.ac.uk/10.3390/ma11122519 - 11 Dec 2018

Cited by 22 | Viewed by 4631

Abstract

This paper investigates the electrical properties in the microwave range of a contact made by graphene nanoplatelets. The final goal is that of estimating the range of values for the equivalent electrical complex permittivity of a contact obtained by integrating low-cost graphene in [...] Read more.

This paper investigates the electrical properties in the microwave range of a contact made by graphene nanoplatelets. The final goal is that of estimating the range of values for the equivalent electrical complex permittivity of a contact obtained by integrating low-cost graphene in the form of nanoplatelets (GNPs) into a high-frequency electrical circuit. To this end, a microstrip-like circuit is designed and realized, where the graphene nanoplatelets are self-assembled into a gap between two copper electrodes. An experimental characterization is carried out, both to study the structural properties of the nanomaterials and of the realized devices, and to measure the electromagnetic scattering parameters in the microwave range by means of a microstrip technique. A full-wave electromagnetic model is also derived and used to investigate the relationship between the measured quantities and the physical and geometrical parameters. The combined use of the experimental and simulation results allows for retrieving the values of the equivalent complex permittivity. The equivalent electrical conductivity values are found to be well below the values expected for isolated graphene nanoplatelets. The real part of the electrical relative permittivity attains values comparable to those obtained with GNP nanocomposites. Full article

(This article belongs to the Special Issue Nanocarbon Based Composites)

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