Graphene nanosheets are single-atom-thick sheets of carbon. Soon after the first synthesis of graphene in 2004, this novel nanomaterial was identified as a strong candidate for a range of applications. The project presents methods for fabrication of sensors and energy converters based on graphene papers, a layered material made of graphene oxide (GO) or reduced GO (RGO) nanosheets.
Graphene, a two-dimensional (2D) material with carbon atoms arrayed in a honeycomb pattern, displays a number of outstanding physicochemical properties. These include excellent conductance for both heat and electricity, and high mechanical strength. For practical applications, graphene will need to be assembled into macroscopic architectures. To this end, graphene oxide (GO) is well suited due to its notable number of oxygen-containing groups on the planar surface and at the edges. These provide possibilities for the functionality and assembly of GO nanosheets into 2D graphene paper with different macroscale shapes through various fabrication techniques. Graphene paper can be used as ideal scaffolds for the incorporation of functional materials with specific functionality.
In the project, GO was modified by nanostructured Prussian Blue (PB) in the form of nanoparticles and cubes. Several advanced techniques (e.g. XRD, XPS, TEM, SEM) were applied for characterization of the nano-composites. The results confirmed that all PB nanostructures were combined well with the graphene nanosheets. Furthermore, PB nanostructure functionalized graphene materials were fabricated into disposable paper sensors and supercapacitor electrodes. For example, Au@PBNPs hybrid GO suspension was filtered by layer-by-layer into functional GO paper, which was further converted into electrically conductive reduced GO (RGO)/Au@PB paper via hydrazine vapor reduction.
The resulting graphene papers had sufficient conductivity and flexibility, and robust mechanical strength to be cut into free-standing electrodes. With low cost and scalable production capacity, such electrodes are highly interesting as flexible, disposable, simple and low-cost sensors. In the project, their efficiency as sensors for detection of H2O2 was demonstrated.
Also, graphene paper was designed as a sacrificial template for preparation of 2D nano-porous metal oxide (MO). 2D MO structures demonstrated superior catalytic, photovoltaic and electrochemical performance due to their large surface-to-volume ratio and nanometer scale thickness. Nano-porous structured MO is therefore promising in applications such as adsorption, catalysis, energy conversion and storage, optoelectronics, and as biological sensing platforms.
In particular, a novel method for preparation of 2D nano-porous structural MO by directly annealing GO paper with metal ions was developed. Furthermore, layer-by-layer, nanoporous 2D CuO nanosheets were assembled into photocanodes for photo-electrochemical water splitting to generate hydrogen.
Finally, CuO/ZnO hybrid nanosheets and NiO nano-sheets were designed as a non-enzymatic sensor for highperformance detection of glucose and urea. 
Illustartion:
Hightlight figure of part 3