Nanomaterials

Editorial

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3 pages, 206 KiB

Open AccessEditorial

Editorial for “Properties and Applications of Graphene and Its Derivatives”

by Jose M. González-Domínguez

Nanomaterials 2022, 12(4), 602; https://doi.org/10.3390/nano12040602 - 11 Feb 2022

Viewed by 1458

Abstract

Since the very first landmark report by Geim and Novoselov in 2004 on graphene [...] Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

Research

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19 pages, 24862 KiB

Open AccessArticle

Cationic Pollutant Removal from Aqueous Solution Using Reduced Graphene Oxide

by Talia Tene, Stefano Bellucci, Marco Guevara, Edwin Viteri, Malvin Arias Polanco, Orlando Salguero, Eder Vera-Guzmán, Sebastián Valladares, Andrea Scarcello, Francesca Alessandro, Lorenzo S. Caputi and Cristian Vacacela Gomez

Nanomaterials 2022, 12(3), 309; https://doi.org/10.3390/nano12030309 - 18 Jan 2022

Cited by 17 | Viewed by 3533

Abstract

Reduced graphene oxide (rGO) is one of the most well-known graphene derivatives, which, due to its outstanding physical and chemical properties as well as its oxygen content, has been used for wastewater treatment technologies. Particularly, extra functionalized rGO is widely preferred for treating [...] Read more.

Reduced graphene oxide (rGO) is one of the most well-known graphene derivatives, which, due to its outstanding physical and chemical properties as well as its oxygen content, has been used for wastewater treatment technologies. Particularly, extra functionalized rGO is widely preferred for treating wastewater containing dyes or heavy metals. Nevertheless, the use of non-extra functionalized (pristine) rGO for the removal of cationic pollutants is not explored in detail or is ambiguous. Herein, pristine rGO—prepared by an eco-friendly protocol—is used for the removal of cationic pollutants from water, i.e., methylene blue (MB) and mercury-(II) (Hg-(II)). This work includes the eco-friendly synthesis process and related spectroscopical and morphological characterization. Most importantly, the investigated rGO shows an adsorption capacity of 121.95 mg g⁻¹ for MB and 109.49 mg g⁻¹ for Hg (II) at 298 K. A record adsorption time of 30 min was found for MB and 20 min for Hg (II) with an efficiency of about 89% and 73%, respectively. The capture of tested cationic pollutants on rGO exhibits a mixed physisorption–chemisorption process. The present work, therefore, presents new findings for cationic pollutant adsorbent materials based on oxidized graphenes, providing a new perspective for removing MB molecules and Hg(II) ions. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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18 pages, 6189 KiB

Open AccessArticle

Waterborne Graphene- and Nanocellulose-Based Inks for Functional Conductive Films and 3D Structures

by Jose M. González-Domínguez, Alejandro Baigorri, Miguel Á. Álvarez-Sánchez, Eduardo Colom, Belén Villacampa, Alejandro Ansón-Casaos, Enrique García-Bordejé, Ana M. Benito and Wolfgang K. Maser

Nanomaterials 2021, 11(6), 1435; https://doi.org/10.3390/nano11061435 - 29 May 2021

Cited by 15 | Viewed by 3530

Abstract

In the vast field of conductive inks, graphene-based nanomaterials, including chemical derivatives such as graphene oxide as well as carbon nanotubes, offer important advantages as per their excellent physical properties. However, inks filled with carbon nanostructures are usually based on toxic and contaminating [...] Read more.

In the vast field of conductive inks, graphene-based nanomaterials, including chemical derivatives such as graphene oxide as well as carbon nanotubes, offer important advantages as per their excellent physical properties. However, inks filled with carbon nanostructures are usually based on toxic and contaminating organic solvents or surfactants, posing serious health and environmental risks. Water is the most desirable medium for any envisioned application, thus, in this context, nanocellulose, an emerging nanomaterial, enables the dispersion of carbon nanomaterials in aqueous media within a sustainable and environmentally friendly scenario. In this work, we present the development of water-based inks made of a ternary system (graphene oxide, carbon nanotubes and nanocellulose) employing an autoclave method. Upon controlling the experimental variables, low-viscosity inks, high-viscosity pastes or self-standing hydrogels can be obtained in a tailored way. The resulting inks and pastes are further processed by spray- or rod-coating technologies into conductive films, and the hydrogels can be turned into aerogels by freeze-drying. The film properties, with respect to electrical surface resistance, surface morphology and robustness, present favorable opportunities as metal-free conductive layers in liquid-phase processed electronic device structures. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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14 pages, 4857 KiB

Open AccessCommunication

Drying-Time Study in Graphene Oxide

by Talia Tene, Marco Guevara, Andrea Valarezo, Orlando Salguero, Fabian Arias Arias, Melvin Arias, Andrea Scarcello, Lorenzo S. Caputi and Cristian Vacacela Gomez

Nanomaterials 2021, 11(4), 1035; https://doi.org/10.3390/nano11041035 - 19 Apr 2021

Cited by 25 | Viewed by 3424

Abstract

Graphene oxide (GO) exhibits different properties from those found in free-standing graphene, which mainly depend on the type of defects induced by the preparation method and post-processing. Although defects in graphene oxide are widely studied, we report the effect of drying time in [...] Read more.

Graphene oxide (GO) exhibits different properties from those found in free-standing graphene, which mainly depend on the type of defects induced by the preparation method and post-processing. Although defects in graphene oxide are widely studied, we report the effect of drying time in GO and how this modifies the presence or absence of edge-, basal-, and sp³-type defects. The effect of drying time is evaluated by Raman spectroscopy, UV-visible spectroscopy, and transmission electron microscopy (TEM). The traditional D, G, and 2D peaks are observed together with other less intense peaks called the D’, D*, D**, D+G, and G+D. Remarkably, the D* peak is activated/deactivated as a direct consequence of drying time. Furthermore, the broad region of the 2D peak is discussed as a function of its deconvoluted 2D_1A, 2D_2A, and D+G bands. The main peak in UV-visible absorption spectra undergoes a redshift as drying time increases. Finally, TEM measurements demonstrate the stacking of exfoliated GO sheets as the intercalated (water) molecules are removed. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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15 pages, 2093 KiB

Open AccessArticle

Reduced Graphene Oxide Inserted into PEDOT:PSS Layer to Enhance the Electrical Behaviour of Light-Emitting Diodes

by Fernando Rodríguez-Mas, Juan Carlos Ferrer, José Luis Alonso, Susana Fernández de Ávila and David Valiente

Nanomaterials 2021, 11(3), 645; https://doi.org/10.3390/nano11030645 - 5 Mar 2021

Cited by 8 | Viewed by 2350

Abstract

In this study, poly(9-vinylcarbazole) (PVK)-based LEDs doped with reduced graphene oxide (rGO) and cadmium sulphide (CdS) nanocrystals were fabricated by spin-coating. The hybrid LED structure was a layer sequence of glass/indium tin oxide (ITO)/PEDOT:PSS|rGO/PVK/Al. rGO was included in the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) layer due [...] Read more.

In this study, poly(9-vinylcarbazole) (PVK)-based LEDs doped with reduced graphene oxide (rGO) and cadmium sulphide (CdS) nanocrystals were fabricated by spin-coating. The hybrid LED structure was a layer sequence of glass/indium tin oxide (ITO)/PEDOT:PSS|rGO/PVK/Al. rGO was included in the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) layer due to its energy bands being close to PEDOT:PSS bands, and the possibility of using water for dispersing both polymer and flakes. Optical properties such as photoluminescence and UV-Vis absorption were not affected by the addition of rGO to the PEDOT:PSS solution. However, PVK-based LEDs with rGO showed increased current density compared to those without rGO in the hole transporting layer. Higher electroluminescence intensities were observed for rGO-enriched LEDs, although the shape of the spectrum was not modified. LEDs including CdS nanocrystals in the poly(9-vinylcarbazole) emissive layer did not show such dependence on the rGO presence. Though the addition of rGO to PEDOT:PSS still produces a slightly higher current density in CdS doped LEDs, this growth is no longer proportional to the rGO load. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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16 pages, 4104 KiB

Open AccessFeature PaperArticle

Highly Multifunctional GNP/Epoxy Nanocomposites: From Strain-Sensing to Joule Heating Applications

by Xoan F. Sánchez-Romate, Alejandro Sans, Alberto Jiménez-Suárez, Mónica Campo, Alejandro Ureña and Silvia G. Prolongo

Nanomaterials 2020, 10(12), 2431; https://doi.org/10.3390/nano10122431 - 5 Dec 2020

Cited by 25 | Viewed by 2636

Abstract

A performance mapping of GNP/epoxy composites was developed according to their electromechanical and electrothermal properties for applications as strain sensors and Joule heaters. To achieve this purpose, a deep theoretical and experimental study of the thermal and electrical conductivity of nanocomposites has been [...] Read more.

A performance mapping of GNP/epoxy composites was developed according to their electromechanical and electrothermal properties for applications as strain sensors and Joule heaters. To achieve this purpose, a deep theoretical and experimental study of the thermal and electrical conductivity of nanocomposites has been carried out, determining the influence of both nanofiller content and sonication time. Concerning dispersion procedure, at lower contents, higher sonication times induce a decrease of thermal and electrical conductivity due to a more prevalent GNP breakage effect. However, at higher GNP contents, sonication time implies an enhancement of both electrical and thermal properties due to a prevalence of exfoliating mechanisms. Strain monitoring tests indicate that electrical sensitivity increases in an opposite way than electrical conductivity, due to a higher prevalence of tunneling mechanisms, with the 5 wt.% specimens being those with the best results. Moreover, Joule heating tests showed the dominant role of electrical mechanisms on the effectiveness of resistive heating, with the 8 wt.% GNP samples being those with the best capabilities. By taking the different functionalities into account, it can be concluded that 5 wt.% samples with 1 h sonication time are the most balanced for electrothermal applications, as shown in a radar chart. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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16 pages, 8106 KiB

Open AccessEditor’s ChoiceArticle

Reduced Graphene Oxide Sheets as Inhibitors of the Photochemical Reactions of α-Lipoic Acid in the Presence of Ag and Au Nanoparticles

by N’ghaya Toulbe, Malvina S. Stroe, Monica Daescu, Radu Cercel, Alin Mogos, Daniela Dragoman, Marcela Socol, Ionel Mercioniu and Mihaela Baibarac

Nanomaterials 2020, 10(11), 2238; https://doi.org/10.3390/nano10112238 - 11 Nov 2020

Cited by 5 | Viewed by 3136

Abstract

The influence of Ag and Au nanoparticles and reduced graphene oxide (RGO) sheets on the photodegradation of α-lipoic acid (ALA) was determined by UV-VIS spectroscopy. The ALA photodegradation was explained by considering the affinity of thiol groups for the metallic nanoparticles synthesized in [...] Read more.

The influence of Ag and Au nanoparticles and reduced graphene oxide (RGO) sheets on the photodegradation of α-lipoic acid (ALA) was determined by UV-VIS spectroscopy. The ALA photodegradation was explained by considering the affinity of thiol groups for the metallic nanoparticles synthesized in the presence of trisodium citrate. The presence of excipients did not induce further changes when ALA interacts with Ag and Au nanoparticles with sizes of 5 and 10 nm by exposure to UV light. Compared to the Raman spectrum of ALA powder, changes in Raman lines’ position and relative intensities when ALA has interacted with films obtained from Au nanoparticles with sizes between 5 and 50 nm were significant. These changes were explained by considering the chemical mechanism of surface-enhanced Raman scattering (SERS) spectroscopy. The photodegradation of ALA that had interacted with metallic nanoparticles was inhibited in the presence of RGO sheets. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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11 pages, 3141 KiB

Open AccessArticle

Improved Field Emission Properties of Carbon Nanostructures by Laser Surface Engineering

by Minh Nhat Dang, Minh Dang Nguyen, Nguyen Khac Hiep, Phan Ngoc Hong, In Hyung Baek and Nguyen Tuan Hong

Nanomaterials 2020, 10(10), 1931; https://doi.org/10.3390/nano10101931 - 27 Sep 2020

Cited by 8 | Viewed by 2965

Abstract

We herein present an alternative geometry of nanostructured carbon cathode capable of obtaining a low turn-on field, and both stable and high current densities. This cathode geometry consisted of a micro-hollow array on planar carbon nanostructures engineered by femtosecond laser. The micro-hollow geometry [...] Read more.

We herein present an alternative geometry of nanostructured carbon cathode capable of obtaining a low turn-on field, and both stable and high current densities. This cathode geometry consisted of a micro-hollow array on planar carbon nanostructures engineered by femtosecond laser. The micro-hollow geometry provides a larger edge area for achieving a lower turn-on field of 0.70 V/µm, a sustainable current of approximately 2 mA (about 112 mA/cm²) at an applied field of less than 2 V/µm. The electric field in the vicinity of the hollow array (rim edge) is enhanced due to the edge effect, that is key to improving field emission performance. The edge effect of the micro-hollow cathode is confirmed by numerical calculation. This new type of nanostructured carbon cathode geometry can be promisingly applied for high intensity and compact electron sources. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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20 pages, 13846 KiB

Open AccessArticle

Graphene Oxide-Based Silico-Phosphate Composite Films for Optical Limiting of Ultrashort Near-Infrared Laser Pulses

by Adrian Petris, Ileana Cristina Vasiliu, Petronela Gheorghe, Ana Maria Iordache, Laura Ionel, Laurentiu Rusen, Stefan Iordache, Mihai Elisa, Roxana Trusca, Dumitru Ulieru, Samaneh Etemadi, Rune Wendelbo, Juan Yang and Knut Thorshaug

Nanomaterials 2020, 10(9), 1638; https://doi.org/10.3390/nano10091638 - 20 Aug 2020

Cited by 11 | Viewed by 3648

Abstract

The development of graphene-based materials for optical limiting functionality is an active field of research. Optical limiting for femtosecond laser pulses in the infrared-B (IR-B) (1.4–3 μm) spectral domain has been investigated to a lesser extent than that for nanosecond, picosecond and femtosecond [...] Read more.

The development of graphene-based materials for optical limiting functionality is an active field of research. Optical limiting for femtosecond laser pulses in the infrared-B (IR-B) (1.4–3 μm) spectral domain has been investigated to a lesser extent than that for nanosecond, picosecond and femtosecond laser pulses at wavelengths up to 1.1 μm. Novel nonlinear optical materials, glassy graphene oxide (GO)-based silico-phosphate composites, were prepared, for the first time to our knowledge, by a convenient and low cost sol-gel method, as described in the paper, using tetraethyl orthosilicate (TEOS), H₃PO₄ and GO/reduced GO (rGO) as precursors. The characterisation of the GO/rGO silico-phosphate composite films was performed by spectroscopy (Fourier-transform infrared (FTIR), Ultraviolet–Visible-Near Infrared (UV-VIS-NIR) and Raman) and microscopy (atomic force microscopy (AFM) and scanning electron microscopy (SEM)) techniques. H₃PO₄ was found to reduce the rGO dispersed in the precursor’s solution with the formation of vertically agglomerated rGO sheets, uniformly distributed on the substrate surface. The capability of these novel graphene oxide-based materials for the optical limiting of femtosecond laser pulses at 1550 nm wavelength was demonstrated by intensity-scan experiments. The GO or rGO presence in the film, their concentrations, the composite films glassy matrix, and the film substrate influence the optical limiting performance of these novel materials and are discussed accordingly. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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15 pages, 3490 KiB

Open AccessArticle

Effect of Varying Amine Functionalities on CO₂ Capture of Carboxylated Graphene Oxide-Based Cryogels

by Alina I. Pruna, Arturo Barjola, Alfonso C. Cárcel, Beatriz Alonso and Enrique Giménez

Nanomaterials 2020, 10(8), 1446; https://doi.org/10.3390/nano10081446 - 24 Jul 2020

Cited by 28 | Viewed by 3654

Abstract

Graphene cryogels synthesis is reported by amine modification of carboxylated graphene oxide via aqueous carbodiimide chemistry. The effect of the amine type on the formation of the cryogels and their properties is presented. In this respect, ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), were [...] Read more.

Graphene cryogels synthesis is reported by amine modification of carboxylated graphene oxide via aqueous carbodiimide chemistry. The effect of the amine type on the formation of the cryogels and their properties is presented. In this respect, ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), were selected. The obtained cryogels were characterized by Fourier Transformed Infrared spectroscopy, thermogravimetric analysis, X-ray spectroscopy, and Scanning electron microscopy. The CO₂ adsorption performance was evaluated as a function of amine modification. The results showed the best CO₂ adsorption performance was exhibited by ethylenediamine modified aerogel, reaching 2 mmol g⁻¹ at 1 bar and 298 K. While the total N content of the cryogels increased with increasing amine groups, the nitrogen configuration and contributions were determined to have more important influence on the adsorption properties. It is also revealed that the residual oxygen functionalities in the obtained cryogels represent another paramount factor to take into account for improving the CO₂ capture properties of amine-modified graphene oxide (GO)-based cryogels. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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17 pages, 7860 KiB

Open AccessArticle

Capacitance Enhancement of Hydrothermally Reduced Graphene Oxide Nanofibers

by Daniel Torres, Sara Pérez-Rodríguez, David Sebastián, José Luis Pinilla, María Jesús Lázaro and Isabel Suelves

Nanomaterials 2020, 10(6), 1056; https://doi.org/10.3390/nano10061056 - 30 May 2020

Cited by 13 | Viewed by 3036

Abstract

Nanocarbon materials present sp²-carbon domains skilled for electrochemical energy conversion or storage applications. In this work, we investigate graphene oxide nanofibers (GONFs) as a recent interesting carbon material class. This material combines the filamentous morphology of the starting carbon nanofibers (CNFs) [...] Read more.

Nanocarbon materials present sp²-carbon domains skilled for electrochemical energy conversion or storage applications. In this work, we investigate graphene oxide nanofibers (GONFs) as a recent interesting carbon material class. This material combines the filamentous morphology of the starting carbon nanofibers (CNFs) and the interlayer spacing of graphene oxide, and exhibits a domain arrangement accessible for fast transport of electrons and ions. Reduced GONFs (RGONFs) present the partial removal of basal functional groups, resulting in higher mesoporosity, turbostratic stacking, and surface chemistry less restrictive for transport phenomena. Besides, the filament morphology minimizes the severe layer restacking shown in the reduction of conventional graphene oxide sheets. The influence of the reduction temperature (140–220 °C) on the electrochemical behaviour in aqueous 0.5 M H₂SO₄ of RGONFs is reported. RGONFs present an improved capacitance up to 16 times higher than GONFs, ascribed to the unique structure of RGONFs containing accessible turbostratic domains and restored electronic conductivity. Hydrothermal reduction at 140 °C results in the highest capacitance as evidenced by cyclic voltammetry and electrochemical impedance spectroscopy measurements (up to 137 F·g⁻¹). Higher temperatures lead to the removal of sulphur groups and slightly thicker graphite domains, and consequently a decrease of the capacitance. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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12 pages, 2683 KiB

Open AccessArticle

Scalable Fabrication of Modified Graphene Nanoplatelets as an Effective Additive for Engine Lubricant Oil

by Duong Duc La, Tuan Ngoc Truong, Thuan Q. Pham, Hoang Tung Vo, Nam The Tran, Tuan Anh Nguyen, Ashok Kumar Nadda, Thanh Tung Nguyen, S. Woong Chang, W. Jin Chung and D. Duc Nguyen

Nanomaterials 2020, 10(5), 877; https://doi.org/10.3390/nano10050877 - 1 May 2020

Cited by 30 | Viewed by 4588

Abstract

The use of nano-additives is widely recognized as a cheap and effective pathway to improve the performance of lubrication by minimizing the energy loss from friction and wear, especially in diesel engines. In this work, a simple and scalable protocol was proposed to [...] Read more.

The use of nano-additives is widely recognized as a cheap and effective pathway to improve the performance of lubrication by minimizing the energy loss from friction and wear, especially in diesel engines. In this work, a simple and scalable protocol was proposed to fabricate a graphene additive to improve the engine lubricant oil. Graphene nanoplates (GNPs) were obtained by a one-step chemical exfoliation of natural graphite and were successfully modified with a surfactant and an organic compound to obtain a modified GNP additive, that can be facilely dispersed in lubricant oil. The GNPs and modified GNP additive were characterized using scanning electron microscopy, X-ray diffraction, atomic force microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. The prepared GNPs had wrinkled and crumpled structures with a diameter of 10–30 µm and a thickness of less than 15 nm. After modification, the GNP surfaces were uniformly covered with the organic compound. The addition of the modified GNP additive to the engine lubricant oil significantly enhanced the friction and antiwear performance. The highest reduction of 35% was determined for the wear scar diameter with a GNP additive concentration of approximately 0.05%. The mechanism for lubrication enhancement by graphene additives was also briefly discussed. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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9 pages, 2842 KiB

Open AccessArticle

Superior Electrocatalytic Activity of MoS₂-Graphene as Superlattice

by Alejandra Rendón-Patiño, Antonio Domenech-Carbó, Ana Primo and Hermenegildo García

Nanomaterials 2020, 10(5), 839; https://doi.org/10.3390/nano10050839 - 27 Apr 2020

Cited by 11 | Viewed by 3368

Abstract

Evidence by selected area diffraction patterns shows the successful preparation of large area (cm × cm) MoS₂/graphene heterojunctions in coincidence of the MoS₂ and graphene hexagons (superlattice). The electrodes of MoS₂/graphene in superlattice configuration show improved catalytic activity [...] Read more.

Evidence by selected area diffraction patterns shows the successful preparation of large area (cm × cm) MoS₂/graphene heterojunctions in coincidence of the MoS₂ and graphene hexagons (superlattice). The electrodes of MoS₂/graphene in superlattice configuration show improved catalytic activity for H₂ and O₂ evolution with smaller overpotential of +0.34 V for the overall water splitting when compared with analogous MoS₂/graphene heterojunction with random stacking. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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11 pages, 2716 KiB

Open AccessArticle

Scalable Preparation of Low-Defect Graphene by Urea-Assisted Liquid-Phase Shear Exfoliation of Graphite and Its Application in Doxorubicin Analysis

by Chang-Seuk Lee, Su Jin Shim and Tae Hyun Kim

Nanomaterials 2020, 10(2), 267; https://doi.org/10.3390/nano10020267 - 5 Feb 2020

Cited by 21 | Viewed by 4326

Abstract

The mass production of graphene is of great interest for commercialization and industrial applications. Here, we demonstrate that high-quality graphene nanosheets can be produced in large quantities by liquid-phase shear exfoliation under ambient conditions in organic solvents, such as 1-methyl-2-pyrrolidinone (NMP), with the [...] Read more.

The mass production of graphene is of great interest for commercialization and industrial applications. Here, we demonstrate that high-quality graphene nanosheets can be produced in large quantities by liquid-phase shear exfoliation under ambient conditions in organic solvents, such as 1-methyl-2-pyrrolidinone (NMP), with the assistance of urea as a stabilizer. We can achieve low-defect graphene (LDG) using this approach, which is relatively simple and easily available, thereby rendering it to be an efficient route for the mass production of graphene. We also demonstrate the electrochemical sensing of an LDG-modified electrode for the determination of doxorubicin (DOX). The sensor shows an enhanced electrocatalytic property towards DOX, leading to a high sensitivity (7.23 × 10⁻¹ μM/μA) with a detection limit of 39.3 nM (S/N = 3). Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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18 pages, 3822 KiB

Open AccessArticle

Tailorable Synthesis of Highly Oxidized Graphene Oxides via an Environmentally-Friendly Electrochemical Process

by Ana María Díez-Pascual, Carlos Sainz-Urruela, Cristina Vallés, Soledad Vera-López and María Paz San Andrés

Nanomaterials 2020, 10(2), 239; https://doi.org/10.3390/nano10020239 - 29 Jan 2020

Cited by 34 | Viewed by 3144

Abstract

Graphene oxide (GO) is an attractive alternative to graphene for many applications due to its captivating optical, chemical, and electrical characteristics. In this work, GO powders with a different amount of surface groups were synthesized from graphite via an electrochemical two-stage process. Many [...] Read more.

Graphene oxide (GO) is an attractive alternative to graphene for many applications due to its captivating optical, chemical, and electrical characteristics. In this work, GO powders with a different amount of surface groups were synthesized from graphite via an electrochemical two-stage process. Many synthesis conditions were tried to maximize the oxidation level, and comprehensive characterization of the resulting samples was carried out via elemental analysis, microscopies (TEM, SEM, AFM), X-ray diffraction, FT-IR and Raman spectroscopies as well as electrical resistance measurements. SEM and TEM images corroborate that the electrochemical process used herein preserves the integrity of the graphene flakes, enabling to obtain large, uniform and well exfoliated GO sheets. The GOs display a wide range of C/O ratios, determined by the voltage and time of each stage as well as the electrolyte concentration, and an unprecedented minimum C/O value was obtained for the optimal conditions. FT-IR evidences strong intermolecular interactions between neighbouring oxygenated groups. The intensity ratio of D/G bands in the Raman spectra is high for samples prepared using concentrated H₂SO₄ as an electrolyte, indicative of many defects. Furthermore, these GOs exhibit smaller interlayer spacing than that expected according to their oxygen content, which suggests predominant oxidation on the flake edges. Results point out that the electrical resistance is conditioned mostly by the interlayer distance and not simply by the C/O ratio. The tuning of the oxidation level is useful for the design of GOs with tailorable structural, electrical, optical, mechanical, and thermal properties. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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Review

Jump to: Editorial, Research

39 pages, 12881 KiB

Open AccessReview

Developments in Synthesis and Potential Electronic and Magnetic Applications of Pristine and Doped Graphynes

by Gisya Abdi, Abdolhamid Alizadeh, Wojciech Grochala and Andrzej Szczurek

Nanomaterials 2021, 11(9), 2268; https://doi.org/10.3390/nano11092268 - 31 Aug 2021

Cited by 16 | Viewed by 3188

Abstract

Doping and its consequences on the electronic features, optoelectronic features, and magnetism of graphynes (GYs) are reviewed in this work. First, synthetic strategies that consider numerous chemically and dimensionally different structures are discussed. Simultaneous or subsequent doping with heteroatoms, controlling dimensions, applying strain, [...] Read more.

Doping and its consequences on the electronic features, optoelectronic features, and magnetism of graphynes (GYs) are reviewed in this work. First, synthetic strategies that consider numerous chemically and dimensionally different structures are discussed. Simultaneous or subsequent doping with heteroatoms, controlling dimensions, applying strain, and applying external electric fields can serve as effective ways to modulate the band structure of these new sp²/sp allotropes of carbon. The fundamental band gap is crucially dependent on morphology, with low dimensional GYs displaying a broader band gap than their bulk counterparts. Accurately chosen precursors and synthesis conditions ensure complete control of the morphological, electronic, and physicochemical properties of resulting GY sheets as well as the distribution of dopants deposited on GY surfaces. The uniform and quantitative inclusion of non-metallic (B, Cl, N, O, or P) and metallic (Fe, Co, or Ni) elements into graphyne derivatives were theoretically and experimentally studied, which improved their electronic and magnetic properties as row systems or in heterojunction. The effect of heteroatoms associated with metallic impurities on the magnetic properties of GYs was investigated. Finally, the flexibility of doped GYs’ electronic and magnetic features recommends them for new electronic and optoelectronic applications. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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41 pages, 4634 KiB

Open AccessReview

Graphene-Based Scaffolds for Regenerative Medicine

by Pietro Bellet, Matteo Gasparotto, Samuel Pressi, Anna Fortunato, Giorgia Scapin, Miriam Mba, Enzo Menna and Francesco Filippini

Nanomaterials 2021, 11(2), 404; https://doi.org/10.3390/nano11020404 - 5 Feb 2021

Cited by 52 | Viewed by 6279

Abstract

Leading-edge regenerative medicine can take advantage of improved knowledge of key roles played, both in stem cell fate determination and in cell growth/differentiation, by mechano-transduction and other physicochemical stimuli from the tissue environment. This prompted advanced nanomaterials research to provide tissue engineers with [...] Read more.

Leading-edge regenerative medicine can take advantage of improved knowledge of key roles played, both in stem cell fate determination and in cell growth/differentiation, by mechano-transduction and other physicochemical stimuli from the tissue environment. This prompted advanced nanomaterials research to provide tissue engineers with next-generation scaffolds consisting of smart nanocomposites and/or hydrogels with nanofillers, where balanced combinations of specific matrices and nanomaterials can mediate and finely tune such stimuli and cues. In this review, we focus on graphene-based nanomaterials as, in addition to modulating nanotopography, elastic modulus and viscoelastic features of the scaffold, they can also regulate its conductivity. This feature is crucial to the determination and differentiation of some cell lineages and is of special interest to neural regenerative medicine. Hereafter we depict relevant properties of such nanofillers, illustrate how problems related to their eventual cytotoxicity are solved via enhanced synthesis, purification and derivatization protocols, and finally provide examples of successful applications in regenerative medicine on a number of tissues. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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42 pages, 11817 KiB

Open AccessReview

A Review of Microscale, Rheological, Mechanical, Thermoelectrical and Piezoresistive Properties of Graphene Based Cement Composite

by Sardar Kashif Ur Rehman, Sabina Kumarova, Shazim Ali Memon, Muhammad Faisal Javed and Mohammed Jameel

Nanomaterials 2020, 10(10), 2076; https://doi.org/10.3390/nano10102076 - 21 Oct 2020

Cited by 48 | Viewed by 5110

Abstract

Extensive research on functionalized graphene, graphene oxide, and carbon nanotube based cement composites has been carried out to strengthen and overcome the shortcomings of construction materials. However, less literature is available on the pure graphene based cement composite. In this review paper, an [...] Read more.

Extensive research on functionalized graphene, graphene oxide, and carbon nanotube based cement composites has been carried out to strengthen and overcome the shortcomings of construction materials. However, less literature is available on the pure graphene based cement composite. In this review paper, an in-depth study on a graphene-based cement composite was performed. Various structural forms of graphene and classifications of graphene-based nanomaterial have been presented. The dispersion mechanism and techniques, which are important for effective utilization in the construction industry, are reviewed critically. Micro-scale characterization of carbon-based cement composite using thermogravimetric analysis (TGA), infrared (IR) spectroscopic analysis, x-ray diffractometric (XRD) analysis, and morphological analysis has also been reviewed. As per the authors’ knowledge, for the first time, a review of flow, energy harvesting, thermoelectrical, and self-sensing properties of graphene and its derivatives as the bases of cement composite are presented. The self-sensing properties of the composite material are reported by exploring physical applications by reinforcing graphene nanoplatelets (GNPs) into concrete beams. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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25 pages, 3936 KiB

Open AccessReview

Recent Advances of Graphene-Derived Nanocomposites in Water-Based Drilling Fluids

by Rabia Ikram, Badrul Mohamed Jan, Jana Vejpravova, M. Iqbal Choudhary and Zaira Zaman Chowdhury

Nanomaterials 2020, 10(10), 2004; https://doi.org/10.3390/nano10102004 - 11 Oct 2020

Cited by 22 | Viewed by 4762

Abstract

Nanocomposite materials have distinctive potential for various types of captivating usage in drilling fluids as a well-designed solution for the petroleum industry. Owing to the improvement of drilling fluids, it is of great importance to fabricate unique nanocomposites and advance their functionalities for [...] Read more.

Nanocomposite materials have distinctive potential for various types of captivating usage in drilling fluids as a well-designed solution for the petroleum industry. Owing to the improvement of drilling fluids, it is of great importance to fabricate unique nanocomposites and advance their functionalities for amplification in base fluids. There is a rising interest in assembling nanocomposites for the progress of rheological and filtration properties. A series of drilling fluid formulations have been reported for graphene-derived nanocomposites as additives. Over the years, the emergence of these graphene-derived nanocomposites has been employed as a paradigm to formulate water-based drilling fluids (WBDF). Herein, we provide an overview of nanocomposites evolution as engineered materials for enhanced rheological attributes in drilling operations. We also demonstrate the state-of-the-art potential graphene-derived nanocomposites for enriched rheology and other significant properties in WBDF. This review could conceivably deliver the inspiration and pathways to produce novel fabrication of nanocomposites and the production of other graphenaceous materials grafted nanocomposites for the variety of drilling fluids. Full article

(This article belongs to the Special Issue Properties and Applications of Graphene and Its Derivatives)

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