Browsing by Subject "Graphene oxide"

Now showing 1 - 5 of 5

Open Access
Application of conjugated cucurbit[8]uril porphyrin supramolecular assembly in electrochemical hydrogen generation
(2020-08) Aoudi, Bouthaina
The ever-increasing demands for energy have encouraged an enormous consumption of fossil fuels worldwide. This has presented major concerns due to their limited resources and serious environmental issues. Therefore, the search for an alternative clean energy fuel has been intensively under study. In the past decade, hydrogen has attracted great attention as a promising fuel for the future. Hydrogen is an eco-friendly fuel that is readily abundant, highly efficient and clean since water is its only combustion product. Herein, this thesis highlights the synthesis and characterization of a novel supramolecular assembly based on cucurbit [8] uril -porphyrin functionalized on electrochemically reduced graphene oxide sheets for application in electrochemical hydrogen evolution. The study conveys optimization procedures for choosing the best catalytic system. Electrochemical analysis including potentiometry, cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were used to evaluate activity and stability. Characterization techniques were also performed to analyze the morphology and chemical structures of composites. Electrochemical studies demonstrated that ERGO: Ni-P composite (which comprises of a layer of graphene oxide drop-casted on FTO followed by a layer of nickel CB[8]-porphyrin) can serve as an excellent electrocatalyst for hydrogen evolution in alkaline medium. The composite exhibited high activity (onset potentialv -20 mV, 56.9 mmol h−1g −1 hydrogen, faradaic efficiency of 93% ), remarkable rate of charge transfer (Rct v 210 Ω), large electrochemical surface area (Cdl v1.67 mFcm−2 ) and significant stability without requiring additional noble metals.
Open Access
Novel materials and techniques for energy conversion and sensing
(2015-12) Ekiz, Okan Öner
In the recent years, characterization of nanomaterials and using them in sensing applications gain considerable attention. Increased research on nanotechnology brings new materials and techniques that come with many unsought properties. Additionally, novel materials and concepts have created new demands for new characterization techniques. In this thesis, our main aim is to characterize novel materials and develop new techniques to use nanotechnology in sensing applications. Graphene is one of the most important material in nanotechnology found in the recent years. In this thesis, we have characterized and explain the electrochemical behavior of graphene oxide. During the experiments, novel properties of graphene oxide have been revealed. Foundings paved the way for new applications of graphene. Recent studies in plasmonic materials made SERS (Surface-Enhanced-Raman- Spectroscopy) an important characterization tool used in nanotechnology. SERS is a powerful technique for chemical speci c and label free analysis of low concentration materials. In this thesis, we have used SERS to build an arti cial nose for detection of VOCs. SERS substrates have been fabricated and used for the experiments. Experiments showed that our technique could detect many VOCs and could be used for several applications such as explosive and drug detection. There is a strong need for easy and cost e ective biosensors especially for homecare applications. Recent advances in nanotechnology help us to develop cost e ective techniques. Reducing costs could make biosensors more accessible for end user applications such. In this thesis, we have developed a biosensor platform by using SPR (Surface Plasmon Resonance) for pathogen detection. Experiments showed that our device could detect 102 pathogens without labeling. Our aim is to improve this platform for rapid food analysis and home-care applications.
Open Access
Recent advances in bioactive 1D and 2D carbon nanomaterials for biomedical applications
(Elsevier, 2018) Erol, Özlem; Uyan, İdil; Hatip, Meyem; Yılmaz, Canelif; Tekinay, Ayse B.; Güler, Mustafa O.
One-dimensional (1D) carbon nanotubes (CNTs) and the two-dimensional (2D) graphene represent the most widely studied allotropes of carbon. Due to their unique structural, electrical, mechanical and optical properties, 1D and 2D carbon nanostructures are considered to be leading candidates for numerous applications in biomedical fields, including tissue engineering, drug delivery, bioimaging and biosensors. The biocompatibility and toxicity issues associated with these nanostructures have been a critical impediment for their use in biomedical applications. In this review, we present an overview of the various materials types, properties, functionalization strategies and characterization methods of 1D and 2D carbon nanomaterials and their derivatives in terms of their biomedical applications. In addition, we discuss various factors and mechanisms affecting their toxicity and biocompatibility.
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Reversible electrical reduction and oxidation of graphene oxide
(American Chemical Society, 2011) Ekiz, O. O.; Ürel, M.; Güner, H.; Mizrak, A. K.; Dâna, A.
We demonstrate that graphene oxide can be reversibly reduced and oxidized using electrical stimulus. Controlled reduction and oxidation in two-terminal devices containing multilayer graphene oxide films are shown to result in switching between partially reduced graphene oxide and graphene, a process which modifies the electronic and optical properties. High-resolution tunneling current and electrostatic force imaging reveal that graphene oxide islands are formed on multilayer graphene, turning graphene into a self-assembled heterostructure random nanomesh. Charge storage and resistive switching behavior is observed in two-terminal devices made of multilayer graphene oxide films, correlated with electrochromic effects. Tip-induced reduction and oxidation are also demonstrated. Results are discussed in terms of thermodynamics of oxidation and reduction reactions. © 2011 American Chemical Society.
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Scanning probe microscopy for optoelectronic characterization at the nanoscale
(2010) Ürel, Mustafa
In this work, we propose methods for electrical characterization of nanostructured surfaces using electrostatic force and tunneling current measurements in scanning probe microscopy. Resolution smaller than 10 nm in electrostatic force microscopy (EFM) is attained and reasons for this attainment is explained in terms of the tip-sample capacitance and mechanical vibrations of tip design. Dynamic measurements are done in EFM using a lumped model for tip-sample electrostatic interaction instead of a simple tip-sample capacitance model. Surface photovoltage measurements are done and assured in EFM using frequency response techniques. Also, combining tunneling current measurements by EFM measurements, optoelectonic properties of graphene/graphene oxide samples are characterized.