Carbon has around 500 allotropes, and most of them have excellent physical properties offering great potential for the development of electronic, optoelectronic, energy storage, and sensor applications. In the case of diamond and graphene/graphite, although the carbon atoms have different hybridization structures, their complementary characteristics and potential for direct conversion between them may open up opportunities for novel all-carbon device applications. Diamond and graphene/graphite have unique superior properties and good lattice matching between them so that the direct fabrication of high-quality graphene-on-diamond heterostructures enables the new development of a variety of ultrawide bandgap devices and chemical/bio-sensors. In this perspective, we introduce recent investigations into the formation of graphene films on diamond substrates through an in situ sp³-to-sp² conversion process to enable their application to radiation detection/photo-electronics, high-power/high-frequency electronics, and chemical/biological sensing.

This work fabricates deep-ultraviolet (DUV) photodetectors (PDs) with a metal-semiconductor-metal structure based on radio-frequency sputtered amorphous Ga₂O₃ films at room temperature. The Ga₂O₃-based PD exhibits a low dark current of 1.41 × 10⁻¹¹ A, a responsivity of 1.77 A W⁻¹ and a fast rise response time of 114 ms. A series of annealing treatments with different atmospheres have been found effective to reduce the oxygen vacancy concentration, exhibiting a trade-off effect between the responsivity and the response time. These results demonstrate a cost-effective room-temperature approach for fabricating amorphous Ga₂O₃-based PDs and developing possible post-synthetic methods for tuning the PD performance.

Graphene is an excellent modifier for the surface modification of electrochemical electrodes due to its exceptional physical properties and, for the development of graphene-based chemical and biosensors, is usually coated on glassy carbon electrodes (GCEs) via drop casting. However, the ease of aggregation and high defect content of reduced graphene oxides degrade the electrical properties. Here, we fabricated low-defect graphene electrodes by catalytically thermal treatment of HPHT diamond substrate, followed by the electrodeposition of Au nanoparticles (AuNPs) with an average size of ≈60 nm on the electrode surface using cyclic voltammetry. The Au nanoparticle-decorated graphene electrodes show a wide linear response range to vanillin from 0.2 to 40 µM with a low limit of detection of 10 nM. This work demonstrates the potential applications of graphene-based hybrid electrodes for highly sensitive chemical detection.

The development of accurate, reliable devices for glucose detection has drawn much attention from the scientific community over the past few years. Here, we report a single-step method to fabricate Ni nanoparticle-modified graphene–diamond hybrid electrodes via a catalytic thermal treatment, by which the graphene layers are directly grown on the diamond surface using Ni thin film as a catalyst, meanwhile, Ni nanoparticles are formed in situ on the graphene surface due to dewetting behavior. The good interface between the Ni nanoparticles and the graphene guarantees efficient charge transfer during electrochemical detection. The fabricated electrodes exhibit good glucose sensing performance with a low detection limit of 2 μM and a linear detection range between 2 μM–1 mM. In addition, this sensor shows great selectivity, suggesting potential applications for sensitive and accurate monitoring of glucose in human blood.