Graphene Oxide Papers Simultaneously Doped with Mg²⁺ and Cl^– for Exceptional Mechanical, Electrical, and Dielectric Properties

Abstract

This paper reports simultaneous modification of graphene oxide (GO) papers by functionalization with MgCl2. The Mg(2+) ions enhance both the interlayer cross-links and lateral bridging between the edges of adjacent GO sheets by forming Mg-O bonds. The improved load transfer between the GO sheets gives rise to a maximum of 200 and 400% increases in Young's modulus and tensile strength of GO papers. The intercalation of chlorine between the GO layers alters the properties of GO papers in two ways by forming ionic Cl(-) and covalent C-Cl bonds. The p-doping effect arising from Cl contributes to large enhancements in electrical conductivities of GO papers, with a remarkable 2500-fold surge in the through-thickness direction. The layered structure and the anisotropic electrical conductivities of reduced GO papers naturally create numerous nanocapacitors that lead to charge accumulation based on the Maxwell-Wagner (MW) polarization. The combined effect of much promoted dipolar polarizations due to Mg-O, C-Cl, and Cl(-) species results in an exceptionally high dielectric constant greater than 60 000 and a dielectric loss of 3 at 1 kHz by doping with 2 mM MgCl2. The excellent mechanical and electrical properties along with unique dielectric performance shown by the modified GO and rGO papers open new avenues for niche applications, such as electromagnetic interference shielding materials.

Coordination‐Driven Hierarchical Assembly of Hybrid Nanostructures Based on 2D Materials

“…Subsequently, various cations were used to modify the GO paper, including divalent and trivalent metal ions, and complex cations (e.g., ZrO 2+ and TiO 2+ ) . Due to the strong coordination interaction between GO nanosheets, the cation‐coordinated GO (GO‐M x + ) papers showed not only significantly reinforced mechanical properties (Figure b), but also impressively enhanced properties in thermal transfer, electrical conductivity, and stability (Figure c) . Similar results were also witnessed in cation‐coordinated rGO (rGO‐M x + ) papers, which were usually realized by reducing the GO‐M x + papers by thermal or chemical reduction .…”

“…Generally, it is believed that counter anions will not influence the structure and properties of cation‐coordinated hybrid nanostructures. However, some studies pointed out that the anions (e.g., Cl − ) could substitute the oxygen‐containing functional groups of GO, forming covalent CCl bonds . Such substitution resulted in a p‐doping effect, thereby improving the electrical conductivities of M 2+ ‐GO papers.…”

Ternary Synergistic Strengthening and Toughening of Bio-Inspired TEMPO-Oxidized Cellulose Nanofibers/Borax/Polyvinyl Alcohol Composite Film with High Transparency

“…The interfacial strengthening mechanisms for biologic composites include hydrogen bonds, , ionic bonds, , and covalent bonds. ,, Compared to hydrogen and ionic bonds, covalent bonds present a high bonding energy and interfacial strength, which can more efficiently improve the strength of composites. Also, it is the most common method to combine covalent, ionic, and hydrogen bonds together to achieve synergistic effects. , …”

Enhanced Dielectric and Mechanical Properties of Ternary Composites via Plasticizer-Induced Dense Interfaces

“…Apart from ferroelectric ceramics, conductive and semi-conductive materials with lower band gaps have been added into polymers to construct high-k composites as well [ 22 , 23 , 24 , 25 ], based on interface polarization [ 26 , 27 , 28 , 29 , 30 , 31 ] and electric percolation threshold [ 32 , 33 , 34 , 35 , 36 ]. Under an applied electric field, movable charges would gather in interface zones between two materials with different intrinsic dielectric constants or conducting properties.…”