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Identifier

000410930

Title

Structural and electrical properties of self-assembled graphene oxide hydrogels

Alternative Title

Δομικές και ηλεκτρικές ιδιότητες των αυτο-συναρμολογούμενων υδρογέλ του οξειδίου του γραφενίου

Author

Γκαμπριτσίτζε, Μπεκάρι

Thesis advisor

Χατζόπουλος, Ζαχαρίας

Reviewer

Δεληγεώργης, Γεώργιος
Ηλιόπουλος, Ελευθέριος

Abstract

The discovery of graphene, a two-dimensional(2D), one atom thick carbon lattice, has triggered an explosion of research interest in areas such as nanoelectronics[1], [2], sensors[3], supercapacitors[4], [5], composites[6–8], and photovoltaic devices[9]. This bloom of research interest is attributed, mainly, to graphene’s outstanding electrical, structural, mechanical, and thermal properties[7–12]. Numerous methods, have been developed for the production of graphene, such as the ‘Scotch tape’ method or mechanical exfoliation[2], [13], chemical vapor deposition(CVD) and more[14], [15], but the reduction of graphene oxide is perhaps the most appealing due to low cost, high throughput production of reduced graphene oxide (RGO), which exhibits comparable structure and properties to pristine graphene. Hydrogels, a three-dimensional (3D) hydrophilic, polymer networks, can imbibe large amount of fluids and have attracted intense research interest due to their applications in pharmaceutical[16] and biomedical areas[17]. Hydrogel as a cross-linked network of hydrophilic polymers have been known since 1960[18].Recently, though, a new type of hydrogel, one where RGO is the building block material, has been demonstrated[19], [20]. These new type of self-assembled graphene hydrogels(SGHs), do not include cross-linkers and can assemble into three-dimensional macrostructures via π-π stacking and Van der Waals forces of reduced graphene oxide sheets. They also exhibit thermal, electrical and mechanical properties superior to that of non-SGHs hydrogels[19], [20]. In this thesis, we use one-step hydrothermal reduction to produce self-assembled graphene hydrogels. We studied the effect of sonication power used in the dispersion, the precursor material and the effect of gel incubation time to structural and electrical characteristics of the resulting gels. To evaluate the resulting gel structures a series of techniques were used such as SEM, AFM on spun coated dispersed precursor GO material, freeze drying, SEM and X-Ray diffraction (XRD) on incubated gel structures and finally a bespoke device that realizes the four probe method to measure the resistance of SGHs in water. Next, the dehydration and swelling of SGHs were tested. Additionally, the chemical stability of SGHs was also tested, by immersing the SGHs in solvents for up to a week. Observation of any sign of instability was performed by visual dissolution inspection and dynamic light scattering (DLS) measurements. Finally, the mechanical properties such as Young’s modulus of SGHs were also measured.

Language

English

Subject

Graphene

Hydrogel

Self-assembly

Αυτο-συναρμολόγηση

Γραφένιο

Issue date

2017-11-22

Collection

School/Department--School of Sciences and Engineering--Department of Physics--Post-graduate theses