Localised strain and doping of 2D materials.

There is a growing interest in 2D materials-based devices as the replacement for established materials, such as silicon and metal oxides in microelectronics and sensing, respectively. However, the atomically thin nature of 2D materials makes them susceptible to slight variations caused by their immediate environment, inducing doping and strain, which can vary between, and even microscopically within, devices. One of the misapprehensions for using 2D materials is the consideration of unanimous intrinsic properties over different support surfaces. The interfacial interaction, intrinsic structural disorder and external strain modulate the properties of 2D materials and govern the device performance. The understanding, measurement and control of these factors are thus one of the significant challenges for the adoption of 2D materials in industrial electronics, sensing, and polymer composites. This topical review provides a comprehensive overview of the effect of strain-induced lattice deformation and its relationship with physical and electronic properties. Using the example of graphene and MoS2 (as the prototypical 2D semiconductor), we rationalise the importance of scanning probe techniques and Raman spectroscopy to elucidate strain and doping in 2D materials. These effects can be directly and accurately characterised through Raman shifts in a non-destructive manner. A generalised model has been presented that deconvolutes the intertwined relationship between strain and doping in graphene and MoS2 that could apply to other members of the 2D materials family. The emerging field of straintronics is presented, where the controlled application of strain over 2D materials induces tuneable physical and electronic properties. These perspectives highlight practical considerations for strain engineering and related microelectromechanical applications.

Two Sprayer CVD Synthesis of Nitrogen-doped Carbon Sponge-type Nanomaterials.

Nitrogen-doped carbon sponge-type nanostructures (N-CSTNs) containing coaxial multiwalled carbon nanotubes are synthesized at 1020 °C by using a modified chemical vapor deposition (CVD) arrangement. Here, the CVD reactor is supplied by two flows coming from two independent sprayers (called sprayer A and sprayer B). The nebulized material in each sprayer is transported by two different gases with different flow velocities. The synthesis of carbon N-CSTNs is performed using different precursors: sprayer A contains a solution composed of ethanol, thiophene and ferrocene, whereas sprayer B contains a solution of benzylamine, thiophene and ferrocene. Samples are classified according to the position inside the reactor and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and thermogravimetric analysis (TGA). Samples collected at the beginning of the reactor contain curly structures with diameters of 10-100 nm. At the end of the reactor, the sample is mainly formed by one type of structure. A spongy-type material is mainly formed in the hottest zone of the tubular furnace. The N-CSTNs are highly hydrophobic with oil sorption properties, which could be used for adsorption of oil spills.