GREAT · GRaphene supramolEculAr elecTronics: a life-long training Career development project

GRaphene supramolEculAr elecTronics: a life-long training Career development project

Tremendous developments have been taking place in the field of electronic materials with the emergence of organic electronics (OEs). The use of small conjugated molecules and polymers, and very recently graphene as semiconductors in electronic devices has already come to fruition in flat panel displays. The use of graphene as a novel material with outstanding electronic and mechanical properties constitutes a rapidly emerging new direction in the field of organic electronics and the potential for scientific breakthroughs in this area is virtually untapped. The Marie Curie IEF project GREAT was targeted at exploiting tailor-made organo-graphene based systems to study their tuneable structure and electronic properties and ultimately to assess their potential in (opto)electronic devices. For this purpose, low-cost and up-scalable processes were designed and optimised to obtain liquid-phase exfoliated graphene (LPEG) dispersions and the functionalisation of the obtained graphene with different organic molecules through supramolecular physisorption was studied. Particular attention was paid to molecules capable of interacting with the graphene surface via strong van der Waals interactions. To this end the focus was given to alkanes and molecules exposing long aliphatic chains. These approaches gave excellent results in terms of improving the yield of single layer graphene during the sonication assisted liquid-phase exfoliation of graphite. The so-obtained organo-graphene materials were analysed with a variety of techniques including: Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), High-Resolution Transmission Electron Microscopy (HR-TEM) and Scanning Tunneling Microscopy (STM), Raman and Ultraviolet-Visible (UV-VIS) spectroscopy and macroscopic Kelvin Probe (KP). Furthermore, isothermal titration calorimetry (ITC) measurements and voltammetric techniques were used to complete the characterisation. The organo-graphene dispersions were processed via wet processing methods to obtain thin (~100 nm) hybrid films. By varying the end-group functionalities of the organic molecules used in the exfoliation process, stimuli-responsive graphene-organic hybrid materials holding potential for applications in multifunctional electronics could be obtained. It was found that particularly photochromic molecules showed a great impact on the modulation of the electronic properties of the hybrid devices by acting through an external remote control, i.e. a light stimulus. The incorporation of photochromic molecules into graphene-based electronic devices could hence be used to confer them reliable and reversible opto-electronic switching properties upon controlled photo-excitation. In two-terminal device configurations the electrical properties of thin graphene-azobenzene hybrid films could be reversibly modulated by alternating ultraviolet and visible light irradiation cycles. As cost effective printing techniques such as ink-jet printing towards graphene electronics gain pace, more complex device designs and architectures can be envisaged, e.g. miniaturization of electronic circuits, multilayer devices and flexible/transparent devices can be realized which are currently under investigation. The developed organo-graphene hybrid system possesses great potential to find ways into applications such as optically controllable memory switching for light-assisted programming and high-sensitive photosensors by the choice of proper device configurations. Through GREAT a Europe-based first class training experience was provided to a very promising young researcher. GREAT gave the fellow the possibility to strengthen his background in the interdisciplinary and intersectorial field of organic electronics and to further develop his research career in Europe by performing cutting-edge science. Contact information: Prof. Paolo Samorì E-mail: samori@unistra.fr

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