Two-dimensional polyaniline (C ₃ N) from carbonized organic single crystals in solid state

Abstract

The formation of 2D polyaniline (PANI) has attracted considerable interest due to its expected electronic and optoelectronic properties. Although PANI was discovered over 150 y ago, obtaining an atomically well-defined 2D PANI framework has been a longstanding challenge. Here, we describe the synthesis of 2D PANI via the direct pyrolysis of hexaaminobenzene trihydrochloride single crystals in solid state. The 2D PANI consists of three phenyl rings sharing six nitrogen atoms, and its structural unit has the empirical formula of C 3 N. The topological and electronic structures of the 2D PANI were revealed by scanning tunneling microscopy and scanning tunneling spectroscopy combined with a first-principle density functional theory calculation. The electronic properties of pristine 2D PANI films (undoped) showed ambipolar behaviors with a Dirac point of -37 V and an average conductivity of 0.72 S/cm. After doping with hydrochloric acid, the conductivity jumped to 1.41 × 10 3 S/cm, which is the highest value for doped PANI reported to date. Although the structure of 2D PANI is analogous to graphene, it contains uniformly distributed nitrogen atoms for multifunctionality; hence, we anticipate that 2D PANI has strong potential, from wet chemistry to device applications, beyond linear PANI and other 2D materials.was discovered in 1834 (1), the word PANI was first coined in 1947 (2), and PANI garnered immense attention from the scientific community due to its intrinsically conducting nature (3). During the last three decades, PANI has been one of the most extensively studied conducting polymers because of its simple synthesis, low cost, high conductivity, environmental stability, and doping chemistry (4, 5). Linear PANI has found broad applicability in rechargeable batteries (6), electromagnetic shielding (7), nonlinear optics (8), light-emitting devices (9), sensors (10), field effect transistors (11), erasable optical information storage (12), membranes (13), digital memory devices (14) (27)], cyclic, spiral, and complex nanostructures have also been reported (28). However, due to the mechanistic complexity of aniline polymerization, the atomic-scale control of PANI structure has not yet been realized (28). Together with the recent discovery of all-carbon-based 2D graphene and its promising potentials (29), 2D network polymers are galvanizing a new wave of research in the scientific community (30). Here, we, for the first time to our knowledge, report the synthesis of real 2D PANI framework from direct pyrolysis of organic single crystals, hexaaminobenzene trihydrochloride (HAB), at 500°C. This synthetic methodology could serve as a straightforward way for the design and synthesis of other new 2D layered materials with many potential applications, from wet chemistry to devices. Results and DiscussionThe key building block, HAB, as a monomer with six functional groups (M6), was synthesized in a pure crystalline form (Fig. 1A and SI Appendix, Fig. S1) (31). It was observed that the HAB single crystals pyrolyze before mel...

Ultra high stiffness and thermal conductivity of graphene like C3N

“…The DFT calculations however suggested that the single-layer C 3 N is a metallic conductor 27 . It is quite well-known that the DFT method based on the PBE functional underestimates the band-gap.…”

“…Based on the experimental results, C 3 N nanomembranes present semiconducting electronic character, with a band gap of around 2.7 eV 27 . The DFT calculations however suggested that the single-layer C 3 N is a metallic conductor 27 .…”

“…As expected and likely to triazine-based graphitic carbon nitride, nitrogenated holey graphene also yields band-gaps of approximately 1.70 eV and 1.96 eV 26 . The interest toward the fabrication of 2D materials made only from carbon and nitrogen atoms seems to be highly attractive, and such that an exciting experimental advance has just taken place with respect to the synthesis of 2D 3 polyaniline crystals with C 3 N stoichiometry 27 . 2D polyaniline lattice is analogous to that of the defect-free graphene, which contains uniformly distributed nitrogen atoms with an ordered pattern.…”

Tuning the Intrinsic Properties of Carbon Nitride for High Quantum Yield Photocatalytic Hydrogen Production

“…Varying the C/N ratio, two eminent derivatives of carbon nitride, namely, C 2 N28 and C 3 N29 have been reported, which might also possibly be used as a photocatalyst. The C 2 N contains many irregular holes in its crystalline structure while C 3 N consists of a hole‐free 2D honeycomb lattice.…”

Clar Rules the Electronic Properties of 2D π‐Conjugated Frameworks: Mind the Gap

“…[11][12][13][14] In contrast, chemically based bottom-up approaches have been able to reach considerably smaller pores. [15][16][17][18][19] Holey graphenes present aw ide range of potential technological applicationsr anging from sensing and nanoelectronics to energy andg as storage. [12,16,[20][21][22][23] The materials studied here, structurally converge with the latticeso fc onjugated microporous polymers and conjugated covalent organic frameworks.…”