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.

Templated assembly of photoswitches significantly increases the energy-storage capacity of solar thermal fuels


Large-scale utilization of solar-energy resources will require considerable advances in energy-storage technologies to meet ever-increasing global energy demands. Other than liquid fuels, existing energy-storage materials do not provide the requisite combination of high energy density, high stability, easy handling, transportability and low cost. New hybrid solar thermal fuels, composed of photoswitchable molecules on rigid, low-mass nanostructures, transcend the physical limitations of molecular solar thermal fuels by introducing local sterically constrained environments in which interactions between chromophores can be tuned. We demonstrate this principle of a hybrid solar thermal fuel using azobenzene-functionalized carbon nanotubes. We show that, on composite bundling, the amount of energy stored per azobenzene more than doubles from 58 to 120 kJ mol–1, and the material also maintains robust cyclability and stability. Our results demonstrate that solar thermal fuels composed of molecule–nanostructure hybrids can exhibit significantly enhanced energy-storage capabilities through the generation of template-enforced steric strain.

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

Relevant articles

Open Access articles citing this article.

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: Synthesis and characterization of azobenzene-functionalized SWCNTs.
Figure 2: Photochemical charging and thermal energy release.
Figure 3: Photochemical and thermal cycling.
Figure 4: Effect of packing photochemical switches in the solid state.
Figure 5: Energy storage as a function of template-packing parameters.


  1. Cook, T. R. et al. Solar energy supply and storage for the legacy and nonlegacy worlds. Chem. Rev. 110, 6474–6502 (2010).

    Article  CAS  Google Scholar 

  2. Aricò, A. S., Bruce, P., Scrosati, B., Tarascon, J-M. & van Schalkwijk, W. Nanostructured materials for advanced energy conversion and storage devices. Nature Mater. 4, 366–377 (2005).

    Article  Google Scholar 

  3. Dunn, B., Kamath, H. & Tarascon, J-M. Electrical energy storage for the grid: a battery of choices. Science 334, 928–935 (2011).

    Article  CAS  Google Scholar 

  4. Reece, S. Y. et al. Wireless solar water splitting using silicon-based semiconductors and earth-abundant catalysts. Science 334, 645–648 (2011).

    Article  CAS  Google Scholar 

  5. Nocera, D. G. The artificial leaf. Acc. Chem. Res. 45, 767–776 (2012).

    Article  CAS  Google Scholar 

  6. Benson, E. E., Kubiak, C. P., Sathrum, A. J. & Smieja, J. M. Electrocatalytic and homogeneous approaches to conversion of CO2 to liquid fuels. Chem. Soc. Rev. 38, 89–99 (2008).

    Article  Google Scholar 

  7. Matthews, H. D. & Solomon, S. Irreversible does not mean unavoidable. Science 340, 438–439 (2013).

    Article  CAS  Google Scholar 

  8. Gur, I., Sawyer, K. & Prasher, R. Searching for a better thermal battery. Science 335, 1454–1455 (2012).

    Article  Google Scholar 

  9. Kucharski, T. J., Tian, Y., Akbulatov, S. & Boulatov, R. Chemical solutions for the closed-cycle storage of solar energy. Energy Environ. Sci. 4, 4449–4472 (2011).

    Article  CAS  Google Scholar 

  10. Bren’, V. A., Dubonosov, A. D., Minkin, V. I. & Chernoivanov, V. A. Norbornadiene–quadricyclane—an effective molecular system for the storage of solar energy. Russ. Chem. Rev. 60, 451–469 (1991).

    Article  Google Scholar 

  11. Zen-ichi, Y. New molecular energy storage systems. J. Photochem. 29, 27–40 (1985).

    Article  Google Scholar 

  12. Scharf, H-D. et al. Criteria for the efficiency, stability, and capacity of abiotic photochemical solar energy storage systems. Angew. Chem. Int. Ed. Engl. 18, 652–662 (1979).

    Article  Google Scholar 

  13. Jones G. II, Chiang, S-H. & Xuan, P. T. Energy storage in organic photoisomers. J. Photochem. 10, 1–18 (1979).

    Article  CAS  Google Scholar 

  14. Dubonosov, A. D., Bren, V. A. & Chernoivanov, V. A. Norbornadiene–quadricyclane as an abiotic system for the storage of solar energy. Russ. Chem. Rev. 71, 917–927 (2002).

    Article  CAS  Google Scholar 

  15. Boese, R. et al. Photochemistry of (fulvalene)tetracarbonyldiruthenium and its derivatives: efficient light energy storage devices. J. Am. Chem. Soc. 119, 6757–6773 (1997).

    Article  CAS  Google Scholar 

  16. Kanai, Y., Srinivasan, V., Meier, S. K., Vollhardt, K. P. C. & Grossman, J. C. Mechanism of thermal reversal of the (fulvalene)tetracarbonyldiruthenium photoisomerization: toward molecular solar–thermal energy storage. Angew. Chem. Int. Ed. 49, 8926–8929 (2010).

    Article  CAS  Google Scholar 

  17. Moth-Poulsen, K. et al. Molecular solar thermal (MOST) energy storage and release system. Energy Environ. Sci. 5, 8534–8537 (2012).

    Article  CAS  Google Scholar 

  18. Hou, Z. et al. Switching from Ru to Fe: picosecond IR spectroscopic investigation of the potential of the (fulvalene)tetracarbonyldiiron frame for molecular solar-thermal storage. Phys. Chem. Chem. Phys. 15, 7466–7469 (2013).

    Article  CAS  Google Scholar 

  19. Kolpak, A. M. & Grossman, J. C. Azobenzene-functionalized carbon nanotubes as high-energy density solar thermal fuels. Nano Lett. 11, 3156–3162 (2011).

    Article  CAS  Google Scholar 

  20. Kolpak, A. M. & Grossman, J. C. Hybrid chromophore/template nanostructures: a customizable platform material for solar energy storage and conversion. J. Chem. Phys. 138, 034303 (2013).

    Article  Google Scholar 

  21. Dyke, C. A. & Tour, J. M. Covalent functionalization of single-walled carbon nanotubes for materials applications. J. Phys. Chem. A 108, 11151–11159 (2004).

    Article  CAS  Google Scholar 

  22. Tasis, D., Tagmatarchis, N., Bianco, A. & Prato, M. Chemistry of carbon nanotubes. Chem. Rev. 106, 1105–1136 (2006).

    Article  CAS  Google Scholar 

  23. Feng, W., Luo, W. & Feng, Y. Photo-responsive carbon nanomaterials functionalized by azobenzene moieties: structures, properties and application. Nanoscale 4, 6118–6134 (2012).

    Article  CAS  Google Scholar 

  24. Ying, Y., Saini, R. K., Liang, F., Sadana, A. K. & Billups, W. E. Functionalization of carbon nanotubes by free radicals. Org. Lett. 5, 1471–1473 (2003).

    Article  CAS  Google Scholar 

  25. Fujino, T., Arzhantsev, S. Y. & Tahara, T. Femtosecond time-resolved fluorescence study of photoisomerization of trans-azobenzene. J. Phys. Chem. A 105, 8123–8129 (2001).

    Article  CAS  Google Scholar 

  26. Han, M. & Hara, M. Intense fluorescence from light-driven self-assembled aggregates of nonionic azobenzene derivative. J. Am. Chem. Soc. 127, 10951–10955 (2005).

    Article  CAS  Google Scholar 

  27. Han, M. R. & Hara, M. Chain length-dependent photoinduced formation of azobenzene aggregates. New J. Chem. 30, 223–227 (2006).

    Article  CAS  Google Scholar 

  28. Han, M., Ishikawa, D., Muto, E. & Hara, M. Isomerization and fluorescence characteristics of sterically hindered azobenzene derivatives. J. Lumin. 129, 1163–1168 (2009).

    Article  CAS  Google Scholar 

  29. Kuhn, H. J., Braslavsky, S. E. & Schmidt, R. Chemical actinometry (IUPAC technical report). Pure Appl. Chem. 76, 2105–2146 (2004).

    Article  CAS  Google Scholar 

Download references


The authors acknowledge financial support from BP for a BP-MIT Postdoctoral Research Associateship (T.J.K.) and research funds awarded through the MIT Energy Initiative, which supported the synthesis of functionalized SWCNTs, and the Advanced Research Projects Agency-Energy (ARPA-E), US Department of Energy, under Award Number DE-AR0000180, which supported all other work. Calculations were performed at the National Energy Research Scientific Computing Center, supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Author information

Authors and Affiliations



T.J.K. synthesized the materials and performed experiments, N.F. performed solid-state fluorescence and spectroscopy measurements, A.M.K. performed DFT calculations and J.O.Z. performed experiments. All authors contributed to the experimental design, analysed the data and wrote the paper.

Corresponding authors

Correspondence to Timothy J. Kucharski, Daniel G. Nocera or Jeffrey C. Grossman.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Supplementary information

Supplementary information

Supplementary information (PDF 1827 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Kucharski, T., Ferralis, N., Kolpak, A. et al. Templated assembly of photoswitches significantly increases the energy-storage capacity of solar thermal fuels. Nature Chem 6, 441–447 (2014).

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