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2D materials (2DMs) have now been established as unique and attractive alternatives to replace current technological materials in a number of applications. Chemical Vapour Deposition (CVD), is undoubtedly the most...

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Herein, the physicochemical properties and enhanced adsorption capacity of highly porous thin-layer graphitic carbon nitride (g-C3N4) nanosheets (CNNs) in relation to the separation of dyes are investigated. Cationic and anionic dyes with similar sizes are adopted to study the adsorption and separation properties of graphitic carbon nitride. Highly porous g-C3N4 nanosheets were synthesized via the direct thermal polycondensation of melamine followed by a thermal exfoliation. A comparative study of bulk g-C3N4 and porous thin-film g-C3N4 nanosheets was carried out. The results revealed the formation of highly porous g-C3N4 nanosheets with a well-oriented structure and adequate chemical stability. Porous thin-layer g-C3N4 nanosheets possess a high surface area of 212 m2/g as compared to 10 m2/g of the bulk material. Interestingly, adsorption experiments employing both cationic (methylene blue, rhodamine 6G, and rhodamine B) and anionic (methyl orange, eosin Y) dyes, as well as their mixtures, revealed that g-C3N4 nanosheets exhibited excellent selective adsorption capacity toward cationic dyes, which is followed by very short equilibrium times (e.g., 100% adsorption of MB within 10 min). The present findings can be well interpreted in terms of improved textural and structural properties of CNNs in conjunction to the dispersion and electrostatic interactions between the different dyes and the surface of CNNs. The experimental findings are further corroborated by means of periodic self-consistent charge density functional tight binding theoretical calculations.

Graphene and other two-dimensional materials (2DMs) have been shown to be promising candidates for the development of flexible and highly-sensitive strain sensors. However, the successful implementation of 2DMs in practical applications is slowed down by complex processing and still low sensitivity. Here, we report on a novel development of strain sensors based on Marangoni self-assemblies of graphene and of its hybrids with other 2DMs that can both withstand very large deformation and exhibit highly sensitive piezoresistive behaviour. By exploiting the Marangoni effect, reference films of self-assembled reduced graphene oxide (RGO) are previously optimized, the electromechanical behaviour being assessed after deposition onto different elastomers demonstrating the potential of producing strain sensors suitable for different fields of application. Hybrid networks are prepared by adding hexagonal boron nitride (hBN) and fluorinated graphene (FGr) to the RGO dispersion. The hybrid integration of 2D materials is demonstrated to become a potential solution to increase substantially the sensitivity of the produced resistive strain without compromising the mechanical integrity of the film. In fact, for quasi-static deformations up to 40%, a range of record GF values were obtained reaching up to 2000, while for cyclic deformations a stable performance is observed.

The combination of two-dimensional materials (2D) into heterostructures enables their integration in tunable ultrathin devices. For applications in electronics and optoelectronics, direct growth of wafer-scale and vertically stacked graphene/hexagonal boron nitride (h-BN) heterostructures is vital. The fundamental problem, however, is the catalytically inert nature of h-BN substrates, which typically provide a low rate of carbon precursor breakdown and consequently a poor rate of graphene synthesis. Furthermore, out-of-plane deformations such as wrinkles are commonly seen in 2D materials grown by Chemical Vapor Deposition (CVD). Herein, a wrinkle-facilitated route is developed for the fast growth of graphene/h-BN vertical heterostructures on Cu foils. The key advantage of this synthetic pathway is the exploitation of the increased reactivity from inevitable line defects arising from the CVD process, which can act as active sites for graphene nucleation. The resulted heterostructures are found to exhibit superlubric properties with increased bending stiffness, as well as directional electronic properties, as revealed from Atomic Force Microscopy (AFM) measurements. This work offers a brand-new route for the fast growth of Gr/h-BN heterostructures with practical scalability, thus propelling applications in electronics and nanomechanical systems.

Ultrathin carbon nanomembranes (CNMs) are two−dimensional materials (2DM) of a few nm thickness with sub−nm intrinsic pores that mimic the biofiltration membranes found in nature. They enable highly selective, permeable, and energy−efficient water separation and can be produced at large scales on porous substrates with tuned properties. The present work reports the mechanical performance of such CNMs produced by p−nitrobiphenyl phosphonic acid (NBPS) or polyvinylbiphenyl (PVBP) and their composite membranes of microporous supporting substrates, which constitute indispensable information for ensuring their mechanical stability during operation. Measuring the nanomechanical properties of the ultrathin material was achieved by atomic force microscopy (AFM) on membranes both supported on flat substrates and suspended on patterned substrates (“composite membrane”). The AFM analysis showed that the CNMs presented Young’s modulus in the range of 2.5–8 GPa. The composite membranes’ responses were investigated by tensile testing in a micro−tensile stage as a function of substrate thickness and substrate pore density and diameter, which were found to affect the mechanical properties. Thermogravimetric analysis was used to investigate the thermal stability of composite membranes at high temperatures. The results revealed the structural integrity of CNMs, while critical parameters governing their mechanical response were identified and discussed.