Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Controlled insulator-to-metal transformation in printable polymer composites with nanometal clusters


Although organic semiconductors have received the most attention, the development of compatible passive elements, such as interconnects and electrodes, is also central to plastic electronics. For this, ligand-protected metal-cluster films have been shown to anneal at low temperatures below 250C to highly conductive metal films, but they suffer from cracking and inadequate substrate adhesion. Here, we report printable metal-cluster–polymer nanocomposites that anneal to a controlled-percolation nanostructure without complete sintering of the metal clusters. This overcomes the previous challenges while still retaining the desired low transformation temperatures. Highly water- and alcohol-soluble gold clusters (75 mg ml−1) were synthesized and homogeneously dispersed into poly(3,4-ethylenedioxythiophene) to give a material with annealed d.c. conductivity tuneable between 10−4 and 105 S cm−1. These composites can inject holes efficiently into all-printed polymer organic transistors. The insulator–metal transformation can also be electrically induced at 1 MV cm−1, suggesting possible memory applications.

This is a preview of subscription content, access via your institution

Access options

Rent or buy this article

Get just this article for as long as you need it


Prices may be subject to local taxes which are calculated during checkout

Figure 1: Highly water- and alcohol-soluble nanogold dispersions.
Figure 2: Film d.c. conductivity as a function of anneal temperature (hotplate: ramp rate 2C min−1) in nitrogen.
Figure 3: Surface morphology of nanogold films with and without the polymer matrix.
Figure 4: Thermally induced insulator-to-metal transformation.
Figure 5: All-printed polymer FET.
Figure 6: Electrically induced insulator-to-metal transformation.


  1. Crone, B. et al. Large-scale complementary integrated circuits based on organic transistors. Nature 403, 521–523 (2000).

    Article  CAS  Google Scholar 

  2. Sirringhaus, H. et al. High-resolution inkjet printing of all-polymer transistor circuits. Science 290, 2123–2126 (2000).

    Article  CAS  Google Scholar 

  3. Huitema, H. E. A. et al. Plastic transistors in active matrix displays. Nature 414, 599 (2001).

    Article  CAS  Google Scholar 

  4. Kawase, T., Sirringhaus, H., Friend, R. H. & Shimoda, T. Inkjet printed via-hole interconnections and resistors for all-polymer transistor circuits. Adv. Mater. 13, 1601–1605 (2001).

    Article  CAS  Google Scholar 

  5. Buffat, P. & Borel, J. P. Size effect on the melting point of gold nanoparticles. Phys. Rev. A 13, 2287–2298 (1976).

    Article  CAS  Google Scholar 

  6. Daniel, M. & Astruc, D. Gold nanoparticles: assembly, supramolecular chemistry, quantum-size-related properties, and applications toward biology, catalysis, and nanotechnology. Chem. Rev. 104, 293–346 (2004).

    Article  CAS  Google Scholar 

  7. Mayya, K. S. & Sastry, M. A new technique for spontaneous growth of colloidal nanoparticle superlattices. Langmuir 15, 1902–1904 (1999).

    Article  CAS  Google Scholar 

  8. Musick, M. D. et al. Metal films prepared by stepwise assembly. 2. Construction and characterization of colloidal Au and Ag multilayers. Chem. Mater. 12, 2869–2881 (2000).

    Article  CAS  Google Scholar 

  9. Fuller, S. B., Wilhelm, E. J. & Jacobson, J. M. Ink-jet printed nanoparticle microelectromechanical systems. J. Microelectromech. Syst. 11, 54–60 (2002).

    Article  Google Scholar 

  10. Huang, D., Liao, F., Molesa, S., Redinger, D. & Subramanian, V. Plastic-compatible low resistance printable gold nanoparticle conductors for flexible electronics. J. Electrochem. Soc. 150, 412–417 (2003).

    Article  Google Scholar 

  11. Brust, M., Walker, M., Bethell, D., Schiffrin, D. & Whyman, R. Synthesis of thiol derivatised gold nanoparticles in a two phase liquid-liquid system. J. Chem. Soc., Chem. Commun. 801–802 (1994).

  12. Mayya, K. S., Patil, V. & Sastry, M. On the stability of carboxylic acid derivatized gold colloidal particles: the role of colloidal solution pH studied by optical absorption spectroscopy. Langmuir 13, 3944–3947 (1997).

    Article  CAS  Google Scholar 

  13. Johnson, S. R., Evans, S. D. & Brydson, R. Influence of a terminal functionality on the physical properties of surfactant-stabilized gold nanoparticles. Langmuir 14, 6639–6647 (1998).

    Article  CAS  Google Scholar 

  14. Chen, S. & Kimura, K. Synthesis and characterization of carboxylate-modified gold nanoparticle powders dispersible in water. Langmuir 15, 1075–1082 (1999).

    Article  CAS  Google Scholar 

  15. Templeton, A. C., Chen, S., Gross, S. M. & Murray, R. W. Water-soluble, isolable gold clusters protected by tiopronin and coenzyme A monolayers. Langmuir 15, 66–76 (1999).

    Article  CAS  Google Scholar 

  16. Cliffel, D. E., Zamborini, F. P., Gross, S. M. & Murray, R. W. Mercaptoammonium-monolayer- protected, water-soluble gold, silver, and palladium clusters. Langmuir 16, 9699–9702 (2000).

    Article  CAS  Google Scholar 

  17. Gittins, D. I. & Caruso, F. Spontaneous phase transfer of nanoparticulate metals from organic to aqueous media. Angew. Chem. Int. Edn 40, 3001–3004 (2001).

    Article  CAS  Google Scholar 

  18. Kanaras, A. G., Kamounah, F. S., Schaumburg, K., Kiely, C. J. & Brust, M. Thioalkylated tetraethylene glycol: A new ligand for water soluble monolayer protected gold clusters. Chem. Commun. 2294–2295 (2002).

  19. Hong, R., Emrick, T. & Rotello, V. M. Monolayer-controlled substrate selectivity using noncovalent enzyme-nanoparticle conjugates. J. Am. Chem. Soc. 126, 13572–13573 (2004).

    Article  CAS  Google Scholar 

  20. Musick, M. D., Keating, C. D., Keefe, M. H. & Natan, M. J. Stepwise construction of conductive Au colloid multilayers from solution. Chem. Mater. 9, 1499–1501 (1997).

    Article  CAS  Google Scholar 

  21. Brust, M., Kiely, C. J., Schiifrin, D. & Bethell, D. Self-assembled gold nanoparticle thin films with nonmetallic optical and electronic properties. Langmuir 14, 5425–5429 (1998).

    Article  CAS  Google Scholar 

  22. Abeles, B., Sheng, P., Coutts, M. D. & Arif, Y. Structural and electrical properties of granular metal films. Adv. Phys. 24, 406–461 (1975).

    Article  Google Scholar 

  23. Pike, G. E. & Seager, C. H. Percolation and conductivity: a computer study I. Phys. Rev. B 10, 1421–1434 (1974).

    Article  Google Scholar 

  24. Quinten, M. & Kreibig, U. Optical properties of aggregates of small metal particles. Surf. Sci. 172, 557–577 (1986).

    Article  CAS  Google Scholar 

  25. El-Sayed, M. A. & Link, S. Size and temperature dependence of the plasmon absorption of colloidal gold nanoparticles. J. Phys. Chem. B 103, 4212–4217 (1999).

    Article  Google Scholar 

  26. Van de Hulst, H. C. Light Scattering by Small Particles (Wiley, New York, 1957).

    Book  Google Scholar 

  27. Granqvist, C. G. & Hunderi, O. Optical properties of ultrafine gold particles. Phys. Rev. B 16, 3513–3534 (1977).

    Article  CAS  Google Scholar 

  28. Scaffardi, L. B., Pellegri, N., de Sanctis, O. & Tocho, J. O. Sizing gold nanoparticles by optical extinction spectroscopy. Nanotechnology 16, 158–163 (2005).

    Article  CAS  Google Scholar 

  29. Aspnes, D. E. Optical properties of thin films. Thin Solid Films 89, 249–262 (1982).

    Article  CAS  Google Scholar 

  30. Born, M. & Wolf, E. Principles of Optics: Electromagnetic Theory of Propagation, Interference and Diffraction of Light (Cambridge Univ. Press, Cambridge, 1999).

    Book  Google Scholar 

  31. Chua, L. L., Ho, P. K. H., Sirringhaus, H. & Friend, R. H. High stability ultrathin spin-on benzocyclobutene gate dielectric for polymer field-effect transistors. Appl. Phys. Lett. 84, 3400–3402 (2004).

    Article  CAS  Google Scholar 

  32. Carchano, H., Lacoste, R. & Segui, Y. Bistable electrical switching in polymer thin films. Appl. Phys. Lett. 19, 414–415 (1971).

    Article  CAS  Google Scholar 

  33. Ouyang, J. Y., Chu, C. W., Szmanda, C. R., Ma, L. P. & Yang, Y. Programmable polymer thin film and non-volatile memory device. Nature Mater. 3, 918–922 (2004).

    Article  CAS  Google Scholar 

  34. Naber, R. C. G., de Boer, B., Blom, P. W. M. & de Leeuw, D. M. Low-voltage polymer field-effect transistors for nonvolatile memories. Appl. Phys. Lett. 87, 203509 (2005).

    Article  Google Scholar 

Download references


We thank NUS (Project 144-000-131-112) and A*STAR (Project 052-117-0030) for funding.

Author information

Authors and Affiliations


Corresponding authors

Correspondence to Lay-Lay Chua or Peter K.-H. Ho.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary Information

Supplementary information I, II and II; figures S1 and S2; tables S1 and S2 (PDF 581 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Sivaramakrishnan, S., Chia, PJ., Yeo, YC. et al. Controlled insulator-to-metal transformation in printable polymer composites with nanometal clusters. Nature Mater 6, 149–155 (2007).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing