Carbon Dots Intercalated MXene for Flexible Organic Hydrogel Absorbers with Synergistically Enhanced Dielectric Loss

With the rapid development of flexible electronics and wearable devices, there is an increasing demand for absorbing materials that exhibit high electromagnetic wave absorption efficiency and mechanical flexibility. In this work, we present a novel and effective strategy for fabricating flexible microwave absorbers via synergistically integrating a polymer framework with conductive fillers. Carbon dots (CDs) functionalized with catechol groups were first synthesized via a bottom-up approach using directed ultrasonication, employing tannic acid dispersed in acetone as the precursor. Owing to the abundant surface functional groups, the as-prepared CDs were uniformly anchored onto MXene nanosheets through chemical bonding, forming a well-dispersed MXene/CDs composite. Subsequently, this hybrid filler was incorporated into a polymer network composed of polyvinyl alcohol (PVA) and acrylamide, with water and glycerol as co-solvents, to fabricate a flexible MXene/CDs organic hydrogel. Notably, glycerol plays an important role in adjusting the polarity of the gel system, thereby effectively optimizing impedance matching. Meanwhile, the abundant heterogeneous interfaces between MXene and CDs significantly enhanced interfacial polarization, and the synergistic coupling of optimized impedance matching with strong dielectric loss endowed the MXene/CDs organic hydrogel with outstanding electromagnetic wave absorption performance. The absorber achieves a minimum reflection loss (RL_min) of - 47.9 dB at 9.46 GHz with a matching thickness of 3.1 mm, along with an effective absorption bandwidth of 3.5 GHz. Furthermore, the synergistic reinforcement of dual-crosslinked polymer chains and the MXene/CDs filler endowed the hydrogel with excellent mechanical robustness, making it suitable for flexible and wearable absorption applications.