Metal-Graphitic Nanocapsules for Molecular Spectroscopy-Based Chemical Analysis, Biosensing, and Targeted Diagnosis

Metal-graphitic nanocapsules are an emerging class of metal-graphitic hybrid nanomaterials, typically consisting of a metal core confined within a single- or few-layer graphitic shell. This unique core–shell architecture integrates the tunable physicochemical properties of metal nanomaterials with the chemical stability, Raman activity, fluorescence-quenching capability, and surface functionalization capacity of graphitic materials. In particular, the metal core can provide plasmonic enhancement as well as magnetic or catalytic auxiliary functions, while the chemically protective graphitic shell protects the core from harsh environments and provides intrinsic Raman bands that can serve as internal standards under well-controlled conditions. These features make metal-graphitic nanocapsules highly attractive as robust nanoprobes for molecular spectroscopy-based chemical analysis, biosensing, and targeted diagnosis. In this review, we first summarize the synthesis strategies, formation mechanisms, and key properties of representative metal-graphitic nanocapsules. We then discuss recent advances in their use across representative analytical and biomedical scenarios, with emphasis on the integration of spectroscopic readouts with targeted recognition strategies. Particular attention is given to how the metal core and graphitic shell cooperatively enhance signal generation, molecular enrichment, selective recognition, environmental stability, internal calibration, and reliable in situ diagnosis in real samples and living systems. Finally, we discuss current challenges and future perspectives for developing metal-graphitic nanocapsules as versatile platforms for molecular spectroscopy-based analysis and diagnosis.