In the recent past, graphene has been discovered and studied as one of the most promising materials after silicon and carbon nanotube. Its atomically thin structure, pristine dangling bonds free surface and interface, ultra-fast charge transport capability, semi-metallic behavior, ultra-strong mechanical ruggedness, promising photonic properties and bio-compatibility makes it a material to explore from all different perspectives to identify potential application areas which can augment the quality of our life. Therefore, in this doctoral work the following critical studies have been carried out meticulously with key findings are listed below: (1) A simplistic and sustainable growth process of double or multi-layer graphene (up to 4” substrate coverage with uniformity) using low-cost atmospheric chemical vapor deposition (APCVD) technique. [presented in MRS Fall Meeting 2012 and in IEEE SIECPC 2012) (2) A buried metallic layer based contact engineering process to overcome the sustained challenge of contact engineering associated with low-dimensional atomically thin material. (presented in IEEE Nano 2013 and archieved in conference proceedings) (3) Demonstration of a fin type graphene transistor (inspired by multi-gate architecture) with a mobility of 11,000 cm2/V.s at room temperature with an applied drive-in voltage of ±1 volt to demonstrate for the first time a pragmatic approach for graphene transistor for mobile applications which can maintain its ultra-fast charge transport behavior with ultra-low power consumption. [Published in ACS Nano 2013] (4) Further a meticulous study has been done to understand the harsh environment compatibility of graphene for its potential use in underwater and space applications. [Published as Cover Article in physica solidi status – Rapid Research Letters, 2014] (5) Due to its highly conductive nature and low surface-to-volume ratio it has been used to replace conventional gold based anodic material in microbial fuel cells (used for water purification in self-sustained mode) to demonstrate its effectiveness as a sustainable low-cost mechanically robust transparent material. [Published in ACS Nano 2013, in Energy Technology 2014 as a Cover Article and in Nature Publishing Group Asia Materials 2014] (6) Extensive study to stabilize graphene surface and to use the phenomena for development of a sensor which can monitor the quality of water. [presented in MRS Fall Meeting 2013 and in MRS Fall Meeting 2014] (7) By using graphene as an expose transistor architecture with ultra-scale high-k dielectric, to develop a series of sensor for glucose monitoring. Sensitivity, selectivity, response rate and refresh time has been studied and optimized. [pending review in Nature Scientific Reports 2015] (8) From the lessons learnt during the development of glucose monitoring sensor cell, a sophisticated low-cost ultra-low power mobile graphene based non-invasive sensor has been assembled and clinically trialed in collaboration with King Faisal Hospitals in Jeddah and in Makkah. [pending review in Science 2015] As a future direction, this thesis also discusses potential of graphene growth on electrochemically deposited metallic seed layers and consequential usage in stretchable and transparent graphene antenna development for fully flexible only graphene based integrated electronic system integration.

This thesis focused on the synthesis and characterization of novel functional materials based on cellulose and graphene derivatives. Cellulose/GO hydrogels were produced as the starting material by dissolving cellulose and dispersing GO in NaOH/urea solution. This method is considered as an efficient, simple, environmentally friendly, and low-cost method. Novel functionalities, such as sensing, catalytic and EMI shielding properties have been “built-in” to cellulose/GO hydrogels. Cellulose/rGO composite films and aerogels were successfully fabricated by dissolving cellulose and dispersing GO in NaOH/urea solution, followed by the chemical reduction with vitamin C as the reducing agent. The cellulose/rGO films and aerogels with various rGO contents were prepared by air-drying and freeze-drying of the prepared cellulose/rGO composite hydrogels. The resultant cellulose/rGO composites prepared by this efficient and simple method show high resistance sensitivity to environmental stimuli like temperature, humidity, liquids, vapours, and strain stress. Thus, the cellulose/rGO films can be applied in detecting human motions and human breath cycles. Liquid temperature, liquid type, and ion concentration also be determined by our cellulose/rGO films. Moreover, the composite aerogels are fast responding and extremely sensitive sensors for vapour detection and testing with good repeatability. It was also revealed that discriminating and quantitative responses can be obtained when analyzing various vapours and different vapour concentrations. For methanol vapour, the aerogel shows linear response to the vapour concentration. Thus cellulose/rGO composite aerogel can be used to quantify methanol vapour concentrations. The efficient, scalable, and environmentally friendly preparation of novel and high-performance of vapour sensing materials with well reproducibility is promising to achieve practical vapour sensing applications. We have successfully presented an effective, facial, simple, and scalable method to form Fe3O4 nanoparticles onto cellulose/GO hydrogels. XRD, FTIR, XPS and TEM indicated that Fe3O4 nanoparticles with good dispersion and uniform size are successfully coated on cellulose matrix and GO sheets. This material was tested as catalyst for the cleaning of dye-contaminated water by oxidation with H2O2.The optimized experiment conditions for AO7 degradation are: [AO7] = 0.1 mM, T = 298 K, [H2O2] = 22 mM, and pH = 3. Under these conditions, the resulting hydrogels display 97 % AO7 removal within 120 min and retained strong degradation performance after twenty consecutive cycles of reuse. Especially, the detailed XPS analysis of cellulose/GO/Fe3O4 and cellulose/Fe3O4 composites indicated that the cellulose/GO/Fe3O4 hydrogel retain its high degradation activity by keeping the ratio of Fe3+/Fe2+ at 2 during the 20 heterogeneous Fenton-like reaction cycles. Therefore, the cellulose/GO/Fe3O4 hydrogel is recommended to test the treatment of other dye-contaminated wastewaters. Cellulose/rGO/Fe3O4 films and aerogels were successfully fabricated by the in-situ grown of Fe3O4 nanoparticles within a cellulose matrix containing rGO sheets. Cellulose/rGO (8 wt.%)/Fe3O4 aerogels with the thickness of 0.5 mm exhibited high EMI shielding performance with the EMI SE value at 32.4-40.1 dB in the 8.2-12.4 GHz frequency range. High loading of rGO and large thickness of the composites are beneficial for the excellent EMI shielding performance of our aerogels. The lightweight aerogel is suitable for the practical application as EMI shielding materials such as spacecraft, aircraft, energy conversion application, and energy storage.

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