Advanced functionalization strategies of diamond and diamond-like carbon for emerging applications in sensing, electronics, and energy conversion

• Functionalization enhances diamond/DLC utility in energy, sensing, and quantum tech • Review links synthesis methods to performance across key application sectors • Highlights role of doping, 2D hybridization, and defect engineering strategies • Identifies challenges in scalability, surface stability, and green synthesis • Proposes AI-driven design and integration with on-chip and biocompatible systems This comprehensive review aims to rigorously assess how sophisticated functionalization methodologies enhance the structural, electronic, and interfacial properties of diamond and diamond-like carbon (DLC) materials, thereby facilitating their integration into high-performance sensors, electronic devices, and energy conversion systems. In particular, we investigate heteroatom doping, covalent grafting, nanostructuring, and hybridization with two-dimensional (2D) materials, thereby establishing explicit correlations between processing techniques and performance metrics. Notable findings documented in the literature indicate that boron doping reduces the resistivity of diamond to approximately 10⁻²Ω·cm while preserving electrochemical stability, nitrogen-vacancy (NV) centers permit nanotesla-level quantum magnetometry with coherence durations surpassing 100µs, nanostructuring amplifies the electroactive surface area by as much as tenfold and diminishes the oxygen evolution overpotential by approximately 100mV, and diamond/DLC–graphene composites achieve specific capacitance values exceeding 250F g⁻¹ with sheet resistances below 50Ω sq⁻¹. These advancements have led to significant improvements in electrochemical biosensors, high-frequency field-effect transistors, flexible supercapacitors, and robust fuel cell electrodes. Furthermore, the review delineates ongoing challenges associated with lattice distortions, surface instability, and scalable manufacturing, while proposing future directions focused on Artificial Intelligence (AI)-assisted material design, eco-friendly synthesis routes, and standardized benchmarking protocols to expedite industrial implementation.