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12 pages, 6549 KiB

Open AccessArticle

Graphene Aerogel Growth on Functionalized Carbon Fibers

by Katerina Vrettos, Konstantinos Spyrou and Vasilios Georgakilas

Molecules 2020, 25(6), 1295; https://doi.org/10.3390/molecules25061295 - 12 Mar 2020

Cited by 7 | Viewed by 4367

Graphene aerogel (GA) is a lightweight, porous, environmentally friendly, 3D structured material with interesting properties, such as electrical conductivity, a high surface area, and chemical stability, which make it a powerful tool in energy storage, sensing, catalyst support, or environmental applications. However, the [...] Read more.

Graphene aerogel (GA) is a lightweight, porous, environmentally friendly, 3D structured material with interesting properties, such as electrical conductivity, a high surface area, and chemical stability, which make it a powerful tool in energy storage, sensing, catalyst support, or environmental applications. However, the poor mechanical stability that often characterizes graphene aerogels is a serious obstacle for their use in such applications. Therefore, we report here the successful mechanical reinforcement of GA with carbon fibers (CFs) by combining reduced graphene oxide (rGO) and CFs in a composite material. The surfaces of the CFs were first successfully desized and enriched with epoxy groups using epichloridrine. Epoxy-functionalized CFs (epoxy-CFs) were further covered by reduced graphene oxide (rGO) nanosheets, using triethylene tetramine (TETA) as a linker. The rGO-covered CFs were finally incorporated into the GA, affording a stiff monolithic aerogel composite. The as-prepared epoxy-CF-reinforced GA was characterized by spectroscopic and microscopic techniques and showed enhanced electrical conductivity and compressive strength. The improved electrical and mechanical properties of the GA-CFs composite could be used, among other things, as electrode material or strain sensor applications. Full article

(This article belongs to the Special Issue Materials Chemistry of Fullerenes, Graphenes and Carbon Nanotubes)

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14 pages, 4004 KiB

Open AccessFeature PaperArticle

Systematic Investigations of Annealing and Functionalization of Carbon Nanotube Yarns

by Maik Scholz, Yasuhiko Hayashi, Victoria Eckert, Vyacheslav Khavrus, Albrecht Leonhardt, Bernd Büchner, Michael Mertig and Silke Hampel

Molecules 2020, 25(5), 1144; https://doi.org/10.3390/molecules25051144 - 04 Mar 2020

Cited by 10 | Viewed by 3669

Abstract

Carbon nanotube yarns (CNY) are a novel carbonaceous material and have received a great deal of interest since the beginning of the 21st century. CNY are of particular interest due to their useful heat conducting, electrical conducting, and mechanical properties. The electrical conductivity [...] Read more.

Carbon nanotube yarns (CNY) are a novel carbonaceous material and have received a great deal of interest since the beginning of the 21st century. CNY are of particular interest due to their useful heat conducting, electrical conducting, and mechanical properties. The electrical conductivity of carbon nanotube yarns can also be influenced by functionalization and annealing. A systematical study of this post synthetic treatment will assist in understanding what factors influences the conductivity of these materials. In this investigation, it is shown that the electrical conductivity can be increased by a factor of 2 and 5.5 through functionalization with acids and high temperature annealing respectively. The scale of the enhancement is dependent on the reducing of intertube space in case of functionalization. For annealing, not only is the highly graphitic structure of the carbon nanotubes (CNT) important, but it is also shown to influence the residual amorphous carbon in the structure. The promising results of this study can help to utilize CNY as a replacement for common materials in the field of electrical wiring. Full article

(This article belongs to the Special Issue Materials Chemistry of Fullerenes, Graphenes and Carbon Nanotubes)

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17 pages, 3291 KiB

Open AccessArticle

Synthesis and Intramolecular Energy- and Electron-Transfer of 3D-Conformeric Tris(fluorenyl-[60]fullerenylfluorene) Derivatives

by He Yin, Min Wang, Loon-Seng Tan and Long Y. Chiang

Molecules 2019, 24(18), 3337; https://doi.org/10.3390/molecules24183337 - 13 Sep 2019

Cited by 4 | Viewed by 2434

Abstract

New 3D conformers were synthesized to show a nanomolecular configuration with geometrically branched 2-diphenylaminofluorene (DPAF-C_2M) chromophores using a symmetrical 1,3,5-triaminobenzene ring as the center core for the connection of three fused DPAF-C_2M moieties. The design led to a class of [...] Read more.

New 3D conformers were synthesized to show a nanomolecular configuration with geometrically branched 2-diphenylaminofluorene (DPAF-C_2M) chromophores using a symmetrical 1,3,5-triaminobenzene ring as the center core for the connection of three fused DPAF-C_2M moieties. The design led to a class of cis-cup-tris[(DPAF-C_2M)-C₆₀(>DPAF-C₉)] 3D conformers with three bisadduct-analogous <C₆₀> cages per nanomolecule facing at the same side of the geometrical molecular cis-cup-shape structure. A sequential synthetic route was described to afford this 3D configurated conformer in a high yield with various spectroscopic characterizations. In principle, a nanostructure with a non-coplanar 3D configuration in design should minimize the direct contact or π-stacking of fluorene rings with each other during molecular packing to the formation of fullerosome array. It may also prevent the self-quenching effect of its photoexcited states in solids. Photophysical properties of this cis-cup-conformer were also investigated. Full article

(This article belongs to the Special Issue Materials Chemistry of Fullerenes, Graphenes and Carbon Nanotubes)

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12 pages, 2352 KiB

Open AccessArticle

Graphene Oxide Tablets for Sample Preparation of Drugs in Biological Fluids: Determination of Omeprazole in Human Saliva for Liquid Chromatography Tandem Mass Spectrometry

by Zeynab Zohdi, Mahdi Hashemi, Abdusalam Uheida, Mohammad Mahdi Moein and Mohamed Abdel-Rehim

Molecules 2019, 24(7), 1191; https://doi.org/10.3390/molecules24071191 - 27 Mar 2019

Cited by 10 | Viewed by 3746

Abstract

In this study, a novel sort of sample preparation sorbent was developed, by preparing thin layer graphene oxide tablets (GO-Tabs) utilizing a mixture of graphene oxide and polyethylene glycol on a polyethylene substrate. The GO-Tabs were used for extraction and concentration of omeprazole [...] Read more.

In this study, a novel sort of sample preparation sorbent was developed, by preparing thin layer graphene oxide tablets (GO-Tabs) utilizing a mixture of graphene oxide and polyethylene glycol on a polyethylene substrate. The GO-Tabs were used for extraction and concentration of omeprazole (OME) in human saliva samples. The determination of OME was carried out using liquid chromatography-tandem mass spectrometry (LC–MS/MS) under gradient LC conditions and in the positive ion mode (ESI+) with mass transitions of m/z 346.3→198.0 for OME and m/z 369.98→252.0 for the internal standard. Standard calibration for the saliva samples was in the range of 2.0–2000 nmol L⁻¹. Limits of detection and quantification were 0.05 and 2.0 nmol L⁻¹, respectively. Method validation showed good method accuracy and precision; the inter-day precision values ranged from 5.7 to 8.3 (%RSD), and the accuracy of determinations varied from −11.8% to 13.3% (% deviation from nominal values). The extraction recovery was 60%, and GO-Tabs could be re-used for more than ten extractions without deterioration in recovery. In this study, the determination of OME in real human saliva samples using GO-Tab extraction was validated. Full article

(This article belongs to the Special Issue Materials Chemistry of Fullerenes, Graphenes and Carbon Nanotubes)

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10 pages, 3310 KiB

Open AccessArticle

Thermal Conductivity of Defective Graphene Oxide: A Molecular Dynamic Study

by Yi Yang, Jing Cao, Ning Wei, Donghui Meng, Lina Wang, Guohua Ren, Rongxin Yan and Ning Zhang

Molecules 2019, 24(6), 1103; https://doi.org/10.3390/molecules24061103 - 20 Mar 2019

Cited by 64 | Viewed by 7501

Abstract

In this paper, the thermal properties of graphene oxide (GO) with vacancy defects were studied using a non-equilibrium molecular dynamics method. The results showed that the thermal conductivity of GO increases with the model length. A linear relationship of the inverse length and [...] Read more.

In this paper, the thermal properties of graphene oxide (GO) with vacancy defects were studied using a non-equilibrium molecular dynamics method. The results showed that the thermal conductivity of GO increases with the model length. A linear relationship of the inverse length and inverse thermal conductivity was observed. The thermal conductivity of GO decreased monotonically with an increase in the degree of oxidation. When the degree of oxidation was 10%, the thermal conductivity of GO decreased by ~90% and this was almost independent of chiral direction. The effect of vacancy defect on the thermal conductivity of GO was also considered. The size effect of thermal conductivity gradually decreases with increasing defect concentration. When the vacancy defect ratio was beyond 2%, the thermal conductivity did not show significant change with the degree of oxidation. The effect of vacancy defect on thermal conductivity is greater than that of oxide group concentration. Our results can provide effective guidance for the designed GO microstructures in thermal management and thermoelectric applications. Full article

(This article belongs to the Special Issue Materials Chemistry of Fullerenes, Graphenes and Carbon Nanotubes)

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Review

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31 pages, 1850 KiB

Open AccessFeature PaperReview

Functionalized Carbon Nanostructures Versus Drug Resistance: Promising Scenarios in Cancer Treatment

by Manuela Curcio, Annafranca Farfalla, Federica Saletta, Emanuele Valli, Elvira Pantuso, Fiore Pasquale Nicoletta, Francesca Iemma, Orazio Vittorio and Giuseppe Cirillo

Molecules 2020, 25(9), 2102; https://doi.org/10.3390/molecules25092102 - 30 Apr 2020

Cited by 14 | Viewed by 3342

Abstract

Carbon nanostructures (CN) are emerging valuable materials for the assembly of highly engineered multifunctional nanovehicles for cancer therapy, in particular for counteracting the insurgence of multi-drug resistance (MDR). In this regard, carbon nanotubes (CNT), graphene oxide (GO), and fullerenes (F) have been proposed [...] Read more.

Carbon nanostructures (CN) are emerging valuable materials for the assembly of highly engineered multifunctional nanovehicles for cancer therapy, in particular for counteracting the insurgence of multi-drug resistance (MDR). In this regard, carbon nanotubes (CNT), graphene oxide (GO), and fullerenes (F) have been proposed as promising materials due to their superior physical, chemical, and biological features. The possibility to easily modify their surface, conferring tailored properties, allows different CN derivatives to be synthesized. Although many studies have explored this topic, a comprehensive review evaluating the beneficial use of functionalized CNT vs G or F is still missing. Within this paper, the most relevant examples of CN-based nanosystems proposed for MDR reversal are reviewed, taking into consideration the functionalization routes, as well as the biological mechanisms involved and the possible toxicity concerns. The main aim is to understand which functional CN represents the most promising strategy to be further investigated for overcoming MDR in cancer. Full article

(This article belongs to the Special Issue Materials Chemistry of Fullerenes, Graphenes and Carbon Nanotubes)

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20 pages, 6875 KiB

Open AccessReview

Filled Carbon Nanotubes as Anode Materials for Lithium-Ion Batteries

by Elisa Thauer, Alexander Ottmann, Philip Schneider, Lucas Möller, Lukas Deeg, Rouven Zeus, Florian Wilhelmi, Lucas Schlestein, Christoph Neef, Rasha Ghunaim, Markus Gellesch, Christian Nowka, Maik Scholz, Marcel Haft, Sabine Wurmehl, Karolina Wenelska, Ewa Mijowska, Aakanksha Kapoor, Ashna Bajpai, Silke Hampel and Rüdiger Klingeler Show full author list Hide full author list

Molecules 2020, 25(5), 1064; https://doi.org/10.3390/molecules25051064 - 27 Feb 2020

Cited by 16 | Viewed by 5157

Abstract

Downsizing well-established materials to the nanoscale is a key route to novel functionalities, in particular if different functionalities are merged in hybrid nanomaterials. Hybrid carbon-based hierarchical nanostructures are particularly promising for electrochemical energy storage since they combine benefits of nanosize effects, enhanced electrical [...] Read more.

Downsizing well-established materials to the nanoscale is a key route to novel functionalities, in particular if different functionalities are merged in hybrid nanomaterials. Hybrid carbon-based hierarchical nanostructures are particularly promising for electrochemical energy storage since they combine benefits of nanosize effects, enhanced electrical conductivity and integrity of bulk materials. We show that endohedral multiwalled carbon nanotubes (CNT) encapsulating high-capacity (here: conversion and alloying) electrode materials have a high potential for use in anode materials for lithium-ion batteries (LIB). There are two essential characteristics of filled CNT relevant for application in electrochemical energy storage: (1) rigid hollow cavities of the CNT provide upper limits for nanoparticles in their inner cavities which are both separated from the fillings of other CNT and protected against degradation. In particular, the CNT shells resist strong volume changes of encapsulates in response to electrochemical cycling, which in conventional conversion and alloying materials hinders application in energy storage devices. (2) Carbon mantles ensure electrical contact to the active material as they are unaffected by potential cracks of the encapsulate and form a stable conductive network in the electrode compound. Our studies confirm that encapsulates are electrochemically active and can achieve full theoretical reversible capacity. The results imply that encapsulating nanostructures inside CNT can provide a route to new high-performance nanocomposite anode materials for LIB. Full article

(This article belongs to the Special Issue Materials Chemistry of Fullerenes, Graphenes and Carbon Nanotubes)

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15 pages, 7817 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Engineering 3D Graphene-Based Materials: State of the Art and Perspectives

by Luca Bellucci and Valentina Tozzini

Molecules 2020, 25(2), 339; https://doi.org/10.3390/molecules25020339 - 14 Jan 2020

Cited by 15 | Viewed by 5182

Abstract

Graphene is the prototype of two-dimensional (2D) materials, whose main feature is the extremely large surface-to-mass ratio. This property is interesting for a series of applications that involve interactions between particles and surfaces, such as, for instance, gas, fluid or charge storage, catalysis, [...] Read more.

Graphene is the prototype of two-dimensional (2D) materials, whose main feature is the extremely large surface-to-mass ratio. This property is interesting for a series of applications that involve interactions between particles and surfaces, such as, for instance, gas, fluid or charge storage, catalysis, and filtering. However, for most of these, a volumetric extension is needed, while preserving the large exposed surface. This proved to be rather a hard task, especially when specific structural features are also required (e.g., porosity or density given). Here we review the recent experimental realizations and theoretical/simulation studies of 3D materials based on graphene. Two main synthesis routes area available, both of which currently use (reduced) graphene oxide flakes as precursors. The first involves mixing and interlacing the flakes through various treatments (suspension, dehydration, reduction, activation, and others), leading to disordered nanoporous materials whose structure can be characterized a posteriori, but is difficult to control. With the aim of achieving a better control, a second path involves the functionalization of the flakes with pillars molecules, bringing a new class of materials with structure partially controlled by the size, shape, and chemical-physical properties of the pillars. We finally outline the first steps on a possible third road, which involves the construction of pillared multi-layers using epitaxial regularly nano-patterned graphene as precursor. While presenting a number of further difficulties, in principle this strategy would allow a complete control on the structural characteristics of the final 3D architecture. Full article

(This article belongs to the Special Issue Materials Chemistry of Fullerenes, Graphenes and Carbon Nanotubes)

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