2023
9.
Koutsioukis, Apostolos; Vrettos, Katerina; Belessi, Vassiliki; Georgakilas, Vasilios
Conductivity Enhancement of Graphene and Graphene Derivatives by Silver Nanoparticles Journal Article
In: Applied Sciences, vol. 13, no. 13, 2023, ISSN: 2076-3417.
Abstract | Links | BibTeX | Tags: Conductive inks, graphene hybrid, gravure printing, silver nanoparticles
@article{app13137600,
title = {Conductivity Enhancement of Graphene and Graphene Derivatives by Silver Nanoparticles},
author = {Apostolos Koutsioukis and Katerina Vrettos and Vassiliki Belessi and Vasilios Georgakilas},
url = {https://www.mdpi.com/2076-3417/13/13/7600},
doi = {10.3390/app13137600},
issn = {2076-3417},
year = {2023},
date = {2023-01-01},
urldate = {2023-01-01},
journal = {Applied Sciences},
volume = {13},
number = {13},
abstract = {In this article, a facile way for the doping of graphene and graphene derivatives with silver nanoparticles at different Ag ratios is described. Ag nanoparticles were formed directly on the surface of two different graphene substrates dispersed in dimethylformamide by the reduction of Ag cations with NaBH4. A few layered graphene nanosheets (FLG) produced from graphite and reduced graphene oxide functionalized with amino arylsulfonates (f-rGO) were used as substrates. The final graphene/Ag nanoparticle hybrid in the form of solid, dense spots showed enhanced electrical conductivity, which can be attributed to the formation of conductive interconnections between the 2D nanosheets. Importantly, electrical conductivities of 20 and 167 103 S m−1 were measured for the hybrids of f-rGO and FLG, respectively, with the higher Ag percentage without an annealing process. A representative hybrid f-rGO with Ag nanoparticles was used for the development of a highly conductive water-based gravure ink with excellent printing properties.},
keywords = {Conductive inks, graphene hybrid, gravure printing, silver nanoparticles},
pubstate = {published},
tppubtype = {article}
}
In this article, a facile way for the doping of graphene and graphene derivatives with silver nanoparticles at different Ag ratios is described. Ag nanoparticles were formed directly on the surface of two different graphene substrates dispersed in dimethylformamide by the reduction of Ag cations with NaBH4. A few layered graphene nanosheets (FLG) produced from graphite and reduced graphene oxide functionalized with amino arylsulfonates (f-rGO) were used as substrates. The final graphene/Ag nanoparticle hybrid in the form of solid, dense spots showed enhanced electrical conductivity, which can be attributed to the formation of conductive interconnections between the 2D nanosheets. Importantly, electrical conductivities of 20 and 167 103 S m−1 were measured for the hybrids of f-rGO and FLG, respectively, with the higher Ag percentage without an annealing process. A representative hybrid f-rGO with Ag nanoparticles was used for the development of a highly conductive water-based gravure ink with excellent printing properties.
2022
8.
Giasafaki, D.; Mitzithra, C.; Belessi, V.; Filippakopoulou, T.; Koutsioukis, A.; Georgakilas, V.; Charalambopoulou, G.; Steriotis, T.
Graphene-Based Composites with Silver Nanowires for Electronic Applications Journal Article
In: Nanomaterials, vol. 12, iss. 19, no. 3443, 2022.
Abstract | Links | BibTeX | Tags: Conductive inks, few-layered graphene, functionalized multiwalled carbon nanotubes, functionalized reduced graphene oxide, Gravure, Printed electronics, silver nanowires
@article{Giasafaki2022,
title = {Graphene-Based Composites with Silver Nanowires for Electronic Applications},
author = {D. Giasafaki and C. Mitzithra and V. Belessi and T. Filippakopoulou and A. Koutsioukis and V. Georgakilas and G. Charalambopoulou and T. Steriotis },
doi = {https://doi.org/10.3390/nano12193443 },
year = {2022},
date = {2022-10-01},
urldate = {2022-10-01},
journal = {Nanomaterials},
volume = {12},
number = {3443},
issue = {19},
abstract = {Graphene/metal nanocomposites have shown a strong potential for use in electronic applications. In particular, the combination of silver nanowires (AgNWs) with graphene derivatives leads to the formation of an efficient conductive network, thus improving the electrical properties of a composite. This work focused on developing highly conductive hydrophilic hybrids of simultaneously functionalized and reduced graphene oxide (f-rGO) and AgNWs in different weight ratios by following two different synthetic routes: (a) the physical mixture of f-rGO and AgNWs, and (b) the in situ reduction of GO in the presence of AgNWs. In addition, the role of AgNWs in improving the electrical properties of graphene derivatives was further examined by mixing AgNWs with a hybrid of few-layered graphene with functionalized multiwalled carbon nanotubes (FLG/MWNT-f-OH). The studied materials showed a remarkable improvement in the overall electrical conductivity due to the synergistic effect of their components, which was proportional to the percentage of Ag and dependent on the procedure of the hybrid formation. One of the f-rGO/AgNWs composites was also selected for the preparation of gravure printing inks that were tested to determine their rheological and printing properties. All of the f-rGO/AgNWs composites were shown to be very promising materials for use as conductive inks for flexible electronics.},
keywords = {Conductive inks, few-layered graphene, functionalized multiwalled carbon nanotubes, functionalized reduced graphene oxide, Gravure, Printed electronics, silver nanowires},
pubstate = {published},
tppubtype = {article}
}
Graphene/metal nanocomposites have shown a strong potential for use in electronic applications. In particular, the combination of silver nanowires (AgNWs) with graphene derivatives leads to the formation of an efficient conductive network, thus improving the electrical properties of a composite. This work focused on developing highly conductive hydrophilic hybrids of simultaneously functionalized and reduced graphene oxide (f-rGO) and AgNWs in different weight ratios by following two different synthetic routes: (a) the physical mixture of f-rGO and AgNWs, and (b) the in situ reduction of GO in the presence of AgNWs. In addition, the role of AgNWs in improving the electrical properties of graphene derivatives was further examined by mixing AgNWs with a hybrid of few-layered graphene with functionalized multiwalled carbon nanotubes (FLG/MWNT-f-OH). The studied materials showed a remarkable improvement in the overall electrical conductivity due to the synergistic effect of their components, which was proportional to the percentage of Ag and dependent on the procedure of the hybrid formation. One of the f-rGO/AgNWs composites was also selected for the preparation of gravure printing inks that were tested to determine their rheological and printing properties. All of the f-rGO/AgNWs composites were shown to be very promising materials for use as conductive inks for flexible electronics.
7.
Koutsioukis, A.; Florakis, G.; Sakellis, E.; and V. Georgakilas,
In: ACS Sustainable Chemistry & Engineering , vol. 10, iss. 38, pp. 12552-12558 , 2022.
Abstract | Links | BibTeX | Tags: 2D materials, Anode materials, Carbon, Colloids, Curcuma, graphene, hydrophobic interactions, Hydrophobicity, liquid exfoliation, Two dimensional materials
@article{Koutsioukis2022,
title = {Stable Dispersion of Graphene in Water, Promoted by High-Yield, Scalable Exfoliation of Graphite in Natural Aqueous Extracts: The Role of Hydrophobic Organic Molecules},
author = {A. Koutsioukis and G. Florakis and E. Sakellis and and V. Georgakilas},
doi = {10.1021/acssuschemeng.2c02326 },
year = {2022},
date = {2022-09-12},
urldate = {2022-09-12},
journal = {ACS Sustainable Chemistry & Engineering },
volume = {10},
issue = {38},
pages = {12552-12558 },
abstract = {The van der Waals interactions between graphene nanosheets and hydrophobic molecules derived from natural aqueous extracts are indicated as the driving force for high-yield exfoliation of graphite and effective dispersion of graphene produced in pure water. Although it seems paradoxical, the absorption of small hydrophobic organic molecules on large graphene surfaces decreases the hydrophobic character of graphene nanosheets, resulting in significant improvement of graphene dispersibility in water. This fact reveals a totally novel mechanism to produce high-quality graphene nanosheets by liquid exfoliation of graphite in natural aqueous extracts and their dispersion in water at relatively high concentrations. This method is easily scalable, environmentally friendly, and low cost and showed remarkable yields. More importantly, the role of van der Waals interactions in preventing the hydrophobic effect is an unexplored area that could open new pathways for the development of two-dimensional materials or the stabilization of colloidal systems such as polymers, proteins, or other biomolecules.},
keywords = {2D materials, Anode materials, Carbon, Colloids, Curcuma, graphene, hydrophobic interactions, Hydrophobicity, liquid exfoliation, Two dimensional materials},
pubstate = {published},
tppubtype = {article}
}
The van der Waals interactions between graphene nanosheets and hydrophobic molecules derived from natural aqueous extracts are indicated as the driving force for high-yield exfoliation of graphite and effective dispersion of graphene produced in pure water. Although it seems paradoxical, the absorption of small hydrophobic organic molecules on large graphene surfaces decreases the hydrophobic character of graphene nanosheets, resulting in significant improvement of graphene dispersibility in water. This fact reveals a totally novel mechanism to produce high-quality graphene nanosheets by liquid exfoliation of graphite in natural aqueous extracts and their dispersion in water at relatively high concentrations. This method is easily scalable, environmentally friendly, and low cost and showed remarkable yields. More importantly, the role of van der Waals interactions in preventing the hydrophobic effect is an unexplored area that could open new pathways for the development of two-dimensional materials or the stabilization of colloidal systems such as polymers, proteins, or other biomolecules.
6.
Barmpakos, D.; Belessi, V.; Xanthopoulos, N.; Krontiras, C. A.; Kaltsas, G.
Flexible Inkjet-Printed Heaters Utilizing Graphene-Based Inks Journal Article
In: Sensors, vol. 22, iss. 3, no. 1173, 2022.
Links | BibTeX | Tags: flexible electronics, flexible heater, functionalized reduced graphene oxide, graphene electronics, printed heater
@article{Barmpakos2022,
title = {Flexible Inkjet-Printed Heaters Utilizing Graphene-Based Inks},
author = {D. Barmpakos and V. Belessi and N. Xanthopoulos and C.A. Krontiras and G. Kaltsas },
doi = {https://doi.org/10.3390/s22031173 },
year = {2022},
date = {2022-02-03},
urldate = {2022-02-03},
journal = {Sensors},
volume = {22},
number = {1173},
issue = {3},
keywords = {flexible electronics, flexible heater, functionalized reduced graphene oxide, graphene electronics, printed heater},
pubstate = {published},
tppubtype = {article}
}
2021
5.
Georgitsopoulou, S.; Stola, N. D.; Bakandritsos, A.; V. Georgakilas,
Advancing the boundaries of the covalent functionalization of graphene oxide Journal Article
In: Surfaces and Interfaces, vol. 26, iss. 101320, 2021, ISSN: 2468-0230.
Abstract | Links | BibTeX | Tags: 1, 3 dipolar cycloaddition, Camptothecin, Doxorubicin, Drug loading, Extended functionalization, Functionalized graphene oxide
@article{Georgitsopoulou2021,
title = {Advancing the boundaries of the covalent functionalization of graphene oxide},
author = {S. Georgitsopoulou and N. D. Stola and A. Bakandritsos and V. Georgakilas,},
doi = {https://doi.org/10.1016/j.surfin.2021.101320},
issn = {2468-0230},
year = {2021},
date = {2021-10-21},
journal = {Surfaces and Interfaces},
volume = {26},
issue = {101320},
abstract = {The synthesis of a derivatized graphene oxide with a particularly high degree of functionalization is achieved through a facile wet‑chemistry procedure. Graphene oxide is a highly reactive graphene derivative, especially with nucleophiles or dipolarophiles. However the reductive action of nucleophiles, as well as of other reactants or solvents usually prevails over functionalization. Therefore, the reactions of graphene oxide lead almost exclusively into reduced graphene derivatives with low functionalization degree. Here we report that tuning the reaction conditions during functionalization can alter the competition outcome of the two simultaneous reactions in a 1,3 dipolar cycloaddition on graphene oxide. Under these conditions, the cycloaddition pathway was dramatically favoured against the unspecific reduction/oxygen elimination side reactions, affording a selectively and densely functionalized graphene oxide. This property can be exploited for enhancing the interactions with target molecules (very effective immobilization of pharmaceutic compounds, as demonstrated here), as well as in other applications such as in preparing catalysts with high content of active sites by coordinating metal nanoparticles or atoms.},
keywords = {1, 3 dipolar cycloaddition, Camptothecin, Doxorubicin, Drug loading, Extended functionalization, Functionalized graphene oxide},
pubstate = {published},
tppubtype = {article}
}
The synthesis of a derivatized graphene oxide with a particularly high degree of functionalization is achieved through a facile wet‑chemistry procedure. Graphene oxide is a highly reactive graphene derivative, especially with nucleophiles or dipolarophiles. However the reductive action of nucleophiles, as well as of other reactants or solvents usually prevails over functionalization. Therefore, the reactions of graphene oxide lead almost exclusively into reduced graphene derivatives with low functionalization degree. Here we report that tuning the reaction conditions during functionalization can alter the competition outcome of the two simultaneous reactions in a 1,3 dipolar cycloaddition on graphene oxide. Under these conditions, the cycloaddition pathway was dramatically favoured against the unspecific reduction/oxygen elimination side reactions, affording a selectively and densely functionalized graphene oxide. This property can be exploited for enhancing the interactions with target molecules (very effective immobilization of pharmaceutic compounds, as demonstrated here), as well as in other applications such as in preparing catalysts with high content of active sites by coordinating metal nanoparticles or atoms.
4.
Koutsioukis, A.; Belessi, V.; Georgakilas, V.
Solid phase functionalization of MWNTs: an eco-friendly approach for carbon-based conductive inks Journal Article
In: Green Chemistry, vol. 23, pp. 5442-5448 , 2021.
Abstract | Links | BibTeX | Tags:
@article{Koutsioukis2021,
title = {Solid phase functionalization of MWNTs: an eco-friendly approach for carbon-based conductive inks},
author = {A. Koutsioukis and V. Belessi and V. Georgakilas},
doi = {https://doi.org/10.1039/D1GC01043C},
year = {2021},
date = {2021-06-23},
urldate = {2021-06-23},
journal = {Green Chemistry},
volume = {23},
pages = {5442-5448 },
abstract = {A green approach for the functionalization of multiwalled carbon nanotubes (MWNTs) with hydrophilic groups and their use for the development of an ecofriendly conductive ink are described here. A known organic functionalization of MWNTs, 1,3 dipolar cycloaddition of catechol substituted azomethine ylide, is performed here for the first time, in the solid phase. The functionalized MWNTs were then mixed with graphene nanosheets in ethanol to produce a hydrophilic and highly conductive all-carbon hybrid. The end product was finally mixed with resin to produce a water based conductive ink. In the total procedure, a solid state reaction and non-toxic and eco-friendly solvents like water or alcohols have been used to produce a totally green conductive ink for industrial printing techniques like flexography or gravure printing.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A green approach for the functionalization of multiwalled carbon nanotubes (MWNTs) with hydrophilic groups and their use for the development of an ecofriendly conductive ink are described here. A known organic functionalization of MWNTs, 1,3 dipolar cycloaddition of catechol substituted azomethine ylide, is performed here for the first time, in the solid phase. The functionalized MWNTs were then mixed with graphene nanosheets in ethanol to produce a hydrophilic and highly conductive all-carbon hybrid. The end product was finally mixed with resin to produce a water based conductive ink. In the total procedure, a solid state reaction and non-toxic and eco-friendly solvents like water or alcohols have been used to produce a totally green conductive ink for industrial printing techniques like flexography or gravure printing.
3.
Barmpakos, D.; Belessi, V.; Schelwald, R.; Kaltsas, G.
In: Nanomaterials, vol. 11, iss. 2025, 2021.
Abstract | Links | BibTeX | Tags: flexible temperature sensors, graphene, inkjet-printed sensors, printed temperature sensors, Reduced graphene oxide
@article{Barmpakos2021,
title = {Evaluation of Inkjet-Printed Reduced and Functionalized Water-Dispersible Graphene Oxide and Graphene on Polymer Substrate—Application to Printed Temperature Sensors},
author = {D. Barmpakos and V. Belessi and R. Schelwald and G. Kaltsas },
doi = {https://doi.org/10.3390/nano11082025 },
year = {2021},
date = {2021-01-06},
urldate = {2021-01-06},
journal = {Nanomaterials},
volume = {11},
issue = {2025},
abstract = {The present work reports on the detailed electro-thermal evaluation of a highly water dispersible, functionalized reduced graphene oxide (f-rGO) using inkjet printing technology. Aiming in the development of printed electronic devices, a flexible polyimide substrate was used for the structures’ formation. A direct comparison between the f-rGO ink dispersion and a commercial graphene inkjet ink is also presented. Extensive droplet formation analysis was performed in order to evaluate the repeatable and reliable jetting from an inkjet printer under study. Electrical characterization was conducted and the electrical characteristics were assessed under different temperatures, showing that the water dispersion of the f-rGO is an excellent candidate for application in printed thermal sensors and microheaters. It was observed that the proposed f-rGO ink presents a tenfold increased temperature coefficient of resistance compared to the commercial graphene ink (G). A successful direct interconnection implementation of both materials with commercial Ag-nanoparticle ink lines was also demonstrated, thus allowing the efficient electrical interfacing of the printed structures. The investigated ink can be complementary utilized for developing fully printed devices with various characteristics, all on flexible substrates with cost-effective, few-step processes.},
keywords = {flexible temperature sensors, graphene, inkjet-printed sensors, printed temperature sensors, Reduced graphene oxide},
pubstate = {published},
tppubtype = {article}
}
The present work reports on the detailed electro-thermal evaluation of a highly water dispersible, functionalized reduced graphene oxide (f-rGO) using inkjet printing technology. Aiming in the development of printed electronic devices, a flexible polyimide substrate was used for the structures’ formation. A direct comparison between the f-rGO ink dispersion and a commercial graphene inkjet ink is also presented. Extensive droplet formation analysis was performed in order to evaluate the repeatable and reliable jetting from an inkjet printer under study. Electrical characterization was conducted and the electrical characteristics were assessed under different temperatures, showing that the water dispersion of the f-rGO is an excellent candidate for application in printed thermal sensors and microheaters. It was observed that the proposed f-rGO ink presents a tenfold increased temperature coefficient of resistance compared to the commercial graphene ink (G). A successful direct interconnection implementation of both materials with commercial Ag-nanoparticle ink lines was also demonstrated, thus allowing the efficient electrical interfacing of the printed structures. The investigated ink can be complementary utilized for developing fully printed devices with various characteristics, all on flexible substrates with cost-effective, few-step processes.
2019
2.
Georgitsopoulou, S.; Petrai, O.; Georgakilas, V.
Highly conductive functionalized reduced graphene oxide Journal Article
In: Surfaces and Interfaces, vol. 16, pp. 152-156, 2019, ISSN: 2468-0230.
Abstract | Links | BibTeX | Tags: 1, 3 dipolar cycloaddition, Carbon nanostructures, Conductive inks, Graphene oxide, Reduced graphene oxide
@article{Georgitsopoulou2019,
title = {Highly conductive functionalized reduced graphene oxide},
author = {S. Georgitsopoulou and O. Petrai and V. Georgakilas },
doi = {https://doi.org/10.1016/j.surfin.2019.05.010},
issn = {2468-0230},
year = {2019},
date = {2019-09-01},
urldate = {2019-09-01},
journal = {Surfaces and Interfaces},
volume = {16},
pages = {152-156},
abstract = {Graphene oxide (GO) is a derivative of graphene that is formed by the exfoliation of graphite oxide; product of graphite treatment with strong oxidants [1], [2], [3], [4]. GO nanosheets are decorated by epoxy and hydroxyl groups at the bulk and carboxylates mainly at the edges, while small isolated aromatic areas complete the surface [4], [5], [6]. The hydrophilic character of GO, due to the oxygen groups, induces high dispersibility in water or other polar solvents such as ethanol or dimethylformamide (DMF) [6], [7]. On the other hand, due to the very low aromatic character, GO is practically non conductive. 1,3 dipolar cycloaddition of azomethine ylide on GO in DMF was followed by a simultaneous reduction of GO. The as prepared functionalized reduced graphene oxide showed excellent stability in water and high electrical conductivity.},
keywords = {1, 3 dipolar cycloaddition, Carbon nanostructures, Conductive inks, Graphene oxide, Reduced graphene oxide},
pubstate = {published},
tppubtype = {article}
}
Graphene oxide (GO) is a derivative of graphene that is formed by the exfoliation of graphite oxide; product of graphite treatment with strong oxidants [1], [2], [3], [4]. GO nanosheets are decorated by epoxy and hydroxyl groups at the bulk and carboxylates mainly at the edges, while small isolated aromatic areas complete the surface [4], [5], [6]. The hydrophilic character of GO, due to the oxygen groups, induces high dispersibility in water or other polar solvents such as ethanol or dimethylformamide (DMF) [6], [7]. On the other hand, due to the very low aromatic character, GO is practically non conductive. 1,3 dipolar cycloaddition of azomethine ylide on GO in DMF was followed by a simultaneous reduction of GO. The as prepared functionalized reduced graphene oxide showed excellent stability in water and high electrical conductivity.
2018
1.
Belessi, V.; Petridis, D.; Steriotis, T.; Spyrou, K.; Manolis, G. K.; Psycharis, V.; Georgakilas, V.
Simultaneous reduction and surface functionalization of graphene oxide for highly conductive and water dispersible graphene derivatives Journal Article
In: SN Applied Sciences, vol. 1, iss. 77, 2018.
Abstract | Links | BibTeX | Tags: Conductive inks, Gravure, Printed electronics, Reduced graphene oxide, Surface functionalization
@article{Belessi2018,
title = {Simultaneous reduction and surface functionalization of graphene oxide for highly conductive and water dispersible graphene derivatives},
author = {V. Belessi and D. Petridis and T. Steriotis and K. Spyrou and G. K. Manolis and V. Psycharis and V. Georgakilas },
doi = {https://doi.org/10.1007/s42452-018-0077-9},
year = {2018},
date = {2018-12-03},
urldate = {2018-12-03},
journal = {SN Applied Sciences},
volume = {1},
issue = {77},
abstract = {A simple and effective preparation method for the simultaneous reduction and functionalization of graphene oxide (rGO) by 2,4-diamino benzene sulfonic acid has been developed. The derivatives exhibit excellent conductivity and high dispersibility in various solvents. The successful preparation of rGO and the presence of the sulfonated aromatic diamine on rGO surface has been confirmed by infrared and X-ray photoelectron spectroscopy, while, the analysis by micro-Raman spectroscopy indicated that the reduction/functionalization alters the lattice structure of GO by the increment the defect density when the 2,4-diamino benzene sulfonic acid is used. Moreover, the study of the dried products by X-ray diffraction spectroscopy suggested the turbostratic restacking of the exfoliated rGO into graphite-like nanostructures. The obtained derivative of simultaneous reduction and functionalization of GO was used for the preparation of highly conductive water-based gravure ink, which in turn, was successfully applied in printing on various flexible substrates, demonstrating its great potentiality in graphene-based flexible and printed electronics applications.},
keywords = {Conductive inks, Gravure, Printed electronics, Reduced graphene oxide, Surface functionalization},
pubstate = {published},
tppubtype = {article}
}
A simple and effective preparation method for the simultaneous reduction and functionalization of graphene oxide (rGO) by 2,4-diamino benzene sulfonic acid has been developed. The derivatives exhibit excellent conductivity and high dispersibility in various solvents. The successful preparation of rGO and the presence of the sulfonated aromatic diamine on rGO surface has been confirmed by infrared and X-ray photoelectron spectroscopy, while, the analysis by micro-Raman spectroscopy indicated that the reduction/functionalization alters the lattice structure of GO by the increment the defect density when the 2,4-diamino benzene sulfonic acid is used. Moreover, the study of the dried products by X-ray diffraction spectroscopy suggested the turbostratic restacking of the exfoliated rGO into graphite-like nanostructures. The obtained derivative of simultaneous reduction and functionalization of GO was used for the preparation of highly conductive water-based gravure ink, which in turn, was successfully applied in printing on various flexible substrates, demonstrating its great potentiality in graphene-based flexible and printed electronics applications.