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Two-dimensional polyaniline crystal with metallic out-of-plane conductivity

Nature volume 638, pages 411–417 (2025)Cite this article

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Abstract

Linear conducting polymers show ballistic transport, imposed by mobile carriers moving along the polymer chains1,2, whereas conductance in the extended dimension, that is, between polymer strands or layers, remains weak due to the lack of intermolecular ordering and electronic coupling3,4,5. Here we report a multilayer-stacked two-dimensional polyaniline (2DPANI) crystal, which shows metallic out-of-plane charge transport with high electrical conductivity. The material comprises columnar π arrays with an interlayer distance of 3.59 Å and periodic rhombohedral lattices formed by interwoven polyaniline chains. Electron spin resonance spectroscopy reveals significant electron delocalization in the 2DPANI lattices. First-principles calculations indicate the in-plane 2D conjugation and strong interlayer electronic coupling in 2DPANI facilitated by the Cl-bridged layer stacking. To assess the local optical conductivity, we used terahertz and infrared nanospectroscopy to unravel a Drude-type conductivity with an infrared plasma frequency and an extrapolated local d.c. conductivity of around 200 S cm−1. Conductive scanning probe microscopy showed an unusually high out-of-plane conductivity of roughly 15 S cm−1. Transport measurements through vertical and lateral micro-devices revealed comparable high out-of-plane (roughly 7 S cm−1) and in-plane conductivity (roughly 16 S cm−1). The vertical micro-devices further showed increasing conductivity with decreasing temperature, demonstrating unique out-of-plane metallic transport behaviour. By using this multilayer-stacked 2D conducting polymer design, we predict the achievement of strong electronic coupling beyond in-plane interactions, potentially reaching three-dimensional metallic conductivity6,7.

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Fig. 1: Schematic illustration of the synthesis procedure and proposed molecular structure for 2DPANI.
Fig. 2: Morphology and structural characterizations of 2DPANI crystals.
Fig. 3: Electronic properties of 2DPANI by ESR studies and DFT calculations.
Fig. 4: THz and IR nanoimaging and nanospectroscopy of 2DPANI.

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The data supporting the findings of the study are available in the paper and its Supplementary Information.

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Acknowledgements

R.D., R.H. and X.F. acknowledge the funding support from EU Graphene Flagship (GrapheneCore3, grant no. 881603), ERC starting grant (FC2DMOF, grant no. 852909), ERC Consolidator grant (no. T2DCP). R.D., X.F., T.B. and T.H. thank Deutsche Forschungsgemeinschaft within CRC 1415 (Chemistry of Synthetic Two-Dimensional Materials, grant no. 417590517), as well as the Center of Advancing Electronics Dresden (cfaed). T.Z. acknowledges the funds from the National Natural Science Foundation of China (grant no. 52322316) and the Excellent Youth Foundation of Zhejiang Province of China (grant no. RG25E030003). R.D. acknowledges the National Natural Science Foundation of China (grant nos. 22272092 and 22472085). S.C. acknowledges the funds from the National Natural Science Foundation of China (grant nos. 61988102, 6242200987 and 62301319) and the Science and Technology Commission of Shanghai Municipality (grant nos. 23010503400 and 23ZR1443500). We acknowledge P. Mack and L. Kaeselitz from Thermo Fisher Scientific (UK) for the assistance of μXPS characterization. R.H. acknowledges financial support from Grant CEX2020-001038-M funded by the Spanish MICIU/AEI/10.13039/501100011033 and Grants RTI2018-094830-B-I00 and PID2021-123949OB-I00 funded by the Spanish MICIU/AEI/10.13039/501100011033 and by ERDF/EU. P.L acknowledges the National Natural Science Foundation of China (grant no. 62075070), the Hubei Optical Fundamental Research Center, and the Innovation Fund of WNLO. T.B., T.H. and P.P.P. thank ZIH Dresden for providing computational resources. We acknowledge ELETTRA Sincrotrone Trieste for providing access to its synchrotron radiation facilities and we thank L. Barba for assistance in using beamline XRD1. The research leading to this result has been supported by the project CALIPSOplus under grant agreement no. 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020.

Author information

Author notes

  1. Shu Chen

    Present address: Terahertz Technology Innovation Research Institute, National Basic Science Center-Terahertz Science and Technology Frontier, Terahertz Precision Biomedical Discipline 111 Project, Shanghai Key Laboratory of Modern Optical System, University of Shanghai for Science and Technology, Shanghai, China

  2. Lars Mester

    Present address: attocube systems AG, Haar, Germany

  3. These authors contributed equally: Tao Zhang, Shu Chen, Petko St. Petkov, Peng Zhang, Haoyuan Qi, Nguyen Ngan Nguyen

Authors and Affiliations

  1. Faculty of Chemistry and Food Chemistry and Center for Advancing Electronics Dresden (cfaed), Technische Universität Dresden, Dresden, Germany

    Tao Zhang, Peng Zhang, Haoyuan Qi, Nguyen Ngan Nguyen, Shunqi Xu, Renhao Dong & Xinliang Feng

  2. Key Laboratory of Advanced Marine Materials, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, China

    Tao Zhang

  3. CIC nanoGUNE BRTA, Donostia-San Sebastián, Spain

    Shu Chen, Peining Li & Lars Mester

  4. University of Sofia, Faculty of Chemistry and Pharmacy, Sofia, Bulgaria

    Petko St. Petkov

  5. Central Facility of Materials Science Electron Microscopy, Universität Ulm, Ulm, Germany

    Haoyuan Qi & Ute Kaiser

  6. Max Planck Institute of Microstructure Physics, Halle (Saale), Germany

    Nguyen Ngan Nguyen, Wenjie Zhang, Jiho Yoon, Stuart S. P. Parkin & Xinliang Feng

  7. Wuhan National Laboratory for Optoelectronics and School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, China

    Peining Li

  8. Chair of Theoretical Chemistry, Technische Universität Dresden, Dresden, Germany

    Thomas Brumme & Thomas Heine

  9. Leibniz Institute for Solid State and Materials Research Dresden, Dresden, Germany

    Alexey Alfonsov, Vladislav Kataev & Bernd Büchner

  10. Fraunhofer Institute for Ceramic Technologies and Systems (IKTS), Dresden, Germany

    Zhongquan Liao

  11. Center for Advancing Electronics Dresden (cfaed) and Faculty of Electrical and Computer Engineering, Technische Universität Dresden, Dresden, Germany

    Mike Hambsch, Stefan C. B. Mannsfeld & Ehrenfried Zschech

  12. Institute for Solid State and Materials Physics and Würzburg-Dresden, Cluster of Excellence ct.qmat, Technische Universität Dresden, Dresden, Germany

    Bernd Büchner

  13. Helmholtz-Zentrum Dresden-Rossendorf, Center for Advanced Systems Understanding (CASUS), Görlitz, Germany

    Thomas Heine

  14. Department of Chemistry and IBS Center for Nanomedicine, Yonsei University eodaemun-gu, Seoul, Republic of Korea

    Thomas Heine

  15. Department of Chemistry, The University of Hong Kong, Hong Kong, China

    Renhao Dong

  16. Materials Innovation Institute for Life Sciences and Energy (MILES), HKU-SIRI, Shenzhen, China

    Renhao Dong

  17. CIC nanoGUNE BRTA and EHU/UPV, Donostia-San Sebastián, Spain

    Rainer Hillenbrand

  18. IKERBASQUE, Basque Foundation for Science, Bilbao, Spain

    Rainer Hillenbrand

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  1. Tao Zhang
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Contributions

T.Z., R.D., R.H. and X.F. conceived the idea and supervised the project. T.Z. and P.Z. performed the synthesis and basic characterization and data analysis. S.X. supported the experiment of model reaction. S.C., P.L., L.M. and R.H. carried out the terahertz and IR nanospectroscopy measurements and analysis. P.P.P., T.B. and T.H. implemented the DFT calculations. H.Q., U.K., Z.L. and E.Z. performed SAED and HRTEM characterization and analysis. N.N.N. carried out c-AFM and analysis. N.N.N., J.Y., W.Z. and S.S.P.P. carried out the study of micro-devices. A.A., V.K., and B.B. performed ESR study. M.H. and S.C.B.M. supported GIWAXS study. All authors discussed the results and assisted with manuscript composition.

Corresponding authors

Correspondence to Thomas Heine, Renhao Dong, Rainer Hillenbrand or Xinliang Feng.

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Competing interests

R.H. is a cofounder of Neaspec GmbH, which is now a part of attocube systems AG, a company producing scattering-type scanning near-field optical microscope systems, such as the ones used in this study. The remaining authors declare no competing interests.

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Zhang, T., Chen, S., Petkov, P.S. et al. Two-dimensional polyaniline crystal with metallic out-of-plane conductivity. Nature 638, 411–417 (2025). https://doi.org/10.1038/s41586-024-08387-9

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