Vertically aligned carbon nanotubes (CNTs) have proven to be one of the best materials for use as an efficient field emitter. To further improve their efficiency as well as long-term use in practical devices, it is necessary to reduce the quantum resistance originating from the interface between electrode and emitters and the entanglement of the CNTs in a bundle texture. Thus, the incorporation of graphene at the bottom of CNT bundles via a seamless carbonaceous interface can easily solve this bottleneck. In this work we have demonstrated for the first time, growth and field emission properties of pure seamless graphene-CNT heterostructures and pure seamless graphene-vertically patterned oriented CNTs heterostructures (SGVCNTs) on Si/SiO2 substrates in contrast to the bare CNT mats and few-layer graphene structures without using any tedious post transfer processes. It was observed that seamless SGVCNTs show better field emission performance in terms of higher current density (236 mA cm−2), lowered turn-on field (0.45 V μm−1) and threshold field (1.931 V μm−1 @100 mA cm−2), and improved field enhancement factor (β ∼ 41 315) which is improved ∼4 fold when compared to a bare CNT mat. The significant improvement of the field emission performance of SGVCNTs is mainly attributed to the low resistive seamless C–C covalent carbonaceous interface, the higher number of emitter sites and patterned vertical orientation that leads to long-term stability of the field emitter with minimal loss up to 32 h. This finding could provide an important solution for carbonaceous material based field emitters for real phase device applications.

Here we report a novel hybrid material consists of 2D graphitic carbon nitride (g-C3N4) and graphene heterostructure that exhibits piezoresistivity superior to graphene and potentially being used as a strain sensor. The g-C3N4 that contains periodically spaced triangular nanopores is used for improving the piezoresistivity of the sensor imparting change in the polarization upon application of strain. In this work, we have investigated graphene/g-C3N4 interfaced materials and quantified its piezoresistive effects through experimental analysis and density functional theory (DFT) based computational studies provide insights into the electronic structures of the hybrid interfaces. We have observed a linear response in electrical resistance for a wide range of uniaxial strains up to ∼25%. The observed increase in resistance upon application of strain corroborates with our computational finding of strain-dependent band gap opening. Further, it has been realized that band-gap opening occurs exclusively in the graphitic layer of the composite materials under strain. However, the g-C3N4 bands remain intact at the interface. The linearity and a considerably small gauge factor (1.89) make graphene/g-C3N4 a promising heterostructure material unlike conventional metal gauge sensor in wide strain pressure sensor devices.

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