MXene Nanoribbon Aerogel-Based Gradient Conductivity Electromagnetic Interference Shields with Unprecedented Combination of High Green Index and Shielding Effectiveness.

The desire to reduce secondary pollution from shielded electronics devices demands electromagnetic interference (EMI) shields with high green index (GI), which is the ratio of absorbance over reflectance. Achieving high GI values simultaneously with high shielding effectiveness (SE) over 50 dB is a serious unresolved challenge. Reducing the impedance mismatch between the shield and free space is the key to reducing the reflection of incoming radiation and enabling more penetration into the body of the shield for absorption. Here a sandwich structure with gradient conductivity is introduced that achieves a combination of high GI (≈2) and SE (70 dB). The top layer deliberately uses an aerogel of low conductivity MXene nanoribbon in PEDOT:PSS polymer to boost the GI. The aerogel also reduces the permittivity of the shield, as another way to reduce the impedance mismatch for a nonmagnetic material. The bottom layer consists of a MXene nanosheet-polymer with its high metal-like conductivity to provide high SE. This successful demonstration is expected to lead to other novel ways to create conductivity gradient EMI shields.