Interfacial and Defective Construction from Diverse Cu x S y Quantum Dots toward Broadband Carbon-Based Microwave Absorber

In this study, highly monodisperse copper sulfide (Cu x S y ) quantum dots (QDs) have been successfully obtained using a ligand-chemistry strategy, and then a variety of S-deficient Cu x S y /nitrogen-doped carbon (NC) heterointerfaces are constructed by compositional fine-tuning (Cu9S5 → Cu1.96S → Cu). First-principles calculations show that the S-deficient domains of Cu x S y QDs and N-doped domains of carbon synergistically enhance the electron transfer from Cu x S y to NC. In addition, the finite element simulations demonstrate that the diverse Cu x S y QDs exhibit their intrinsic size and dielectric confinement effects to precisely manipulate the electric field distortion and improve the relaxation polarization. Consequently, Cu x S y @NC achieves excellent impedance matching and a strong loss mode dominated by dielectric polarization. Among them, Cu x S y @NC-650 has a maximum effective absorption bandwidth of 7.7 GHz at 2.5 mm, while Cu x S y @NC-700 features a minimum reflection loss of −66.7 dB at 13.7 GHz, respectively. Furthermore, the simulations of radar cross-sections have confirmed that the Cu x S y @NC series is promising in the field of radar stealth.