Two-Dimensional Conductive and Redox-Active Nanostructures Synthesized by Crystal-Controlled Polymerization for Electrochemical Applications

Abstract

Two-dimensional nanomaterials have attracted much interest for their anisotropic structures and emergent properties. Whereas a variety of inorganic nanosheets are prepared by exfoliation, design and synthetic strategies of organic nanosheets are still developing. Here we report on crystalcontrolled synthesis of conductive and redox-active organic polymer nanosheets with tunable thickness and lateral size. Although the nanosheets consist of classical conductive polymers, such as polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT), a new crystal-controlled polymerization approach provides 2D nanomaterials with enhanced and characteristic properties. Oxidative polymerization proceeds on the crystal surface of organic oxidants, such as quinone derivatives, with diffusion of the monomer vapor at low temperature under ambient pressure. The present method affords the control of lateral size and thickness of the nanosheets. The resultant nanosheets show the characteristic and enhanced properties originating from a 2D nature, such as the high structure anisotropy with aspect ratio around 10 4 , enhanced conductivity 287 S cm −1 , and specific charge−discharge capacitance 523 F g −1 at the current density of 18 A g −1 . The organic nanosheets with conductivity and redox activity can be used as a building block for development of functional materials and devices.

Redox-active benzoquinones as challenging “non-innocent” linkers to construct 2D frameworks and nanostructures with tunable physical properties

“…In fact, the benzoquinone/hydroquinone derivatives can be used: (i) to form nanosheets and/or be deposited in situ via ALD/MLD as thin films, 139,141 (ii) as building blocks of redox active purely organic or hybrid frameworks, 142,143 (iii) as oxidant substrates and templates to grow conductive organic nanostructures. 140 Nowadays, the current research on redox active benzoquinone/hydroquinone 2D nanostructures is at a very early stage and one can foresee the potential applications in near future. Nonetheless, due to their versatility and their great electrochemical performances, such 2D nanostructures may be excellent candidates as platforms for future energy storage systems.…”

“…The oxidative process is governed by the reduction potential of the benzoquinone derivatives that increase with the presence of electron-withdrawing groups in the ring, while their use as templates afford 2D morphologies that show enhanced conductive properties raising from the 2D nature, controlling the lateral size through the benzoquinones pristine substrate. 140 Remarkably, this approach allows for an appropriate tuning of the lateral size and thickness of nanosheets and the morphology control may play a key role in enhancing properties of conventional materials or in constructing new composite materials acting as size-controlled building blocks through a layer-by-layer self-assembling process.…”

Nanoarchitectonics for conductive polymers using solid and vapor phases

“…Section 3 introduces the polymerization of heteroaromatic monomers on the surface of crystals. 21,22 For example, porous morphologies and 2D nanostructures were obtained on the surface of the oxidant crystals with diffusion of the monomer vapor. Section 4 shows the polymerization of heteroaromatic monomers inside of the oxidant crystals with continuous supply of the monomer vapor.…”

Two‐Dimensional Conducting Polymers: Synthesis and Charge Transport

“…The π‐conjugation systems in nanosheet forms are thus continuously evolving owing to a synergy of synthesis and morphology control . Especially, the preorganization of monomers on solid or liquid surfaces prior to polymerization was attempted, making great contribution to ascend conductivity at short diffusion length scale for charge carriers.…”

“…This approach certainly gets the benefits of thickness control and short reaction time . Examples include polyaniline (PANI), polypyrrole, and poly‐(3,4‐ethylenedioxythiophene) (PEDOT), which demonstrated long‐range order, high crystallinity, robust mechanical strength, and excellent conductivity …”