Graphene/Polyelectrolyte Layer-by-Layer Coatings for Electromagnetic Interference Shielding

Abstract

Electromagnetic interference (EMI) shielding coating materials with thicknesses in the microscale are required in many sectors, including communications, medical, aerospace and electronics, to isolate the electromagnetic radiation emitted from electronic equipment. We report a spray, layer-by-layer (LbL) coating approach to fabricate micron thick, highly-ordered and electrically-conductive coatings with exceptional EMI shielding effectiveness (EMI SE ≥4830 dB/mm), through the alternating self-assembly of negatively-charged reduced graphene oxide (RGO) and a positively-charged polyelectrolyte (PEI). The microstructure and resulting electrical properties of the (PEI/RGO) n LbL structures are studied as function of increasing mass of graphene deposited per cycle (keeping the PEI content constant), number of deposited layers (n), flake diameter and type of RGO. A strong effect of the lateral flake dimensions on the electrical properties is observed, which also influences the EMI SE. A maximum EMI SE of 29 dB is obtained for a 6 μm thick (PEI/RGO) 10 coating with 19 vol.% loading of reduced electrochemically-exfoliated graphene oxide flakes with diameters ~3µm. This SE performance exceeds those previously reported for thicker graphene papers and bulk graphene/polymer composite films with higher RGO or graphene nanoplatelets contents, which represents an important step towards the fabrication of thin and light-weight high-performance EMI shielding structures.performance. 6, 7, 9,12,13 Carbon-based materials have been investigated as conductive fillers to fabricate composite materials for EMI shielding because they offer a combination of high electrical conductivity, excellent mechanical properties, light weight, flexibility and large aspect ratios. [6][7][8][9][10][11][12][13][14][15][16][17] In particular, graphene emerges as highly promising for EMI shielding applications due to its excellent in-plane electrical conductivity (∼4.5 × 10 4 S/cm) 14, 18-20 and easy processability. 21 Graphene-based polymer composites, foam structures, aerogels, thin films and papers have already been investigated as light-weight EMI shielding materials. 2, 22-30 An EMI SE ~500 dB·cm 3 /g was reported for a graphene foam composite with a density ~0.06 g/cm 3 , 2 and ~33780 dB·cm 2 /g for ultralight cellulose fiber/thermally reduced GO hybrid aerogels, with a density as low as 2.83 mg/cm 3 . 22 More recently, EMI SE of 21.8 dB have been reported for thermoplastic polyurethane/reduced graphene oxide composite foams with only 3.17 vol.% of RGO 27 , whereas EMI SE of 48.56 dB has been found for 3D-interconnected graphene aerogels decorated with cobalt ferrite nanoparticles and ZnO nanorods 28 . Graphene papers with thicknesses between 12.5 and 470 µm 23, 24 and ~30-60 µm thick graphene/polymer composites 25,26 were also investigated as EMI shielding materials. Wan et al. reported EMI SE of up to ~52.2 dB for iodine doped and ~47 dB for 12.5 µm thick undoped reduced GO papers 23 , whereas EMI SE ~55.2 dB was reported for 0.47 mm thick multila...

Graphene–Polyurethane Coatings for Deformable Conductors and Electromagnetic Interference Shielding

“…These frequencies are used in smartphones, televisions, and microwaves. [ 68–70 ] The EMI shielding effectiveness (SE) represents the losses in the incoming electromagnetic wave due to screening and is usually calculated using where T is the transmittance and represents the ratio between the transmitted and the incident electromagnetic power and is a function of the frequency of the incoming EM wave. [ 71 ] In Figure 3, the transmittance is plotted as a function of the frequency of the incident EM waves.…”

Layer-by-Layer Assembly of Two-Dimensional Materials: Meticulous Control on the Nanoscale

“…This material reached an EMI shielding efficiency of 29 dB for 6-mm-thick films (Table 1). 80 Ti 3 C 2 T x MXene is well known for having record-setting performance as an EMI shielding material due to excellent electrical conductivity. 9 Ti 3 C 2 T x films with layered structure and optimized interlayer spacing has been achieved using polymer composites with sodium alginate and alternating vacuum-assisted filtration of Ti 3 C 2 T x and carbon nanofibers.…”

Dynamic Control of High-Range Photoresponsivity in a Graphene Nanoribbon Photodetector

“…Graphene, a two-dimensional (2D) layered material, plays an important role in many fields including electrodialysis [1], batteries [2], nanofiltration [3], catalysis [4], electromagnetic interference [5], and optoelectronics. Significantly, graphene has attracted much attention owing to its novel optoelectronic properties [6][7][8][9], such as high carrier mobility [10,11], zero-bandgap [12][13][14], and tunable Fermi level [15].…”