In-situ Synthesis and Enhanced Photothermal Conversion Properties of g-C3N4@Cu for Sensitizing Energetic Nitrocellulose Microspheres

Although graphitic carbon nitride (g-C 3 N 4 ) is a promising two-dimensional material with good thermal conductivity, its wide bandgap and rapid charge recombination limit its direct application in photothermal conversion. In this study, an in-situ doping strategy was employed to introduce copper into the intrinsic vacancies of g-C 3 N 4 , fabricating a surface-porous 2D Cu-doped material (g-C 3 N 4 @Cu). Microstructural and spectroscopic analyses reveal that atomically dispersed Cu via Cu-N bonds significantly broadens the visible-light absorption band via the ligand-to-metal charge transfer (LMCT) effect. This mechanism enables highly efficient absorption and photothermal conversion under blue light (450   nm). This novel photothermal sensitizer was then uniformly immobilized onto nitrocellulose (NC) via a solution-based approach, forming g-C 3 N 4 @Cu/NC energetic microspheres. This integrated design not only enhances interfacial adhesion but also curtails the thermal diffusion path from the photosensitizer to the NC matrix, establishing a synergistic photothermal-thermocatalytic mechanism. Consequently, the composite g-C 3 N 4 @Cu/NC achieves a photothermal conversion efficiency of over 37%. Furthermore, its laser ignition delay time is significantly reduced by approximately 30 times compared to the blank control group, demonstrating an extremely low ignition threshold. Ultimately, this study provides fundamental insights into metal-doped g-C 3 N 4 systems and offers an effective material-design approach for integrating photosensitive and energetic materials for highly controllable optical-to-thermal responses.