Chair for Multicomponent Materials

Plasmonic and photoswitchable nanocomposites

Plasmonic devices have been a very hot topic during the last decade due to hosts of potential appications. Such devices are usually fabricated by elaborate lithography techniques which prevent upscaling to large areas. In our group we develop disordered plasmonic nanocomposites which are prepared by vapor phase co-deposition where the nanostructure forms via self-organization.

The nanocomposites consist of metallic nanoparticles in a dielectric matrix that are small compared to the wavelength of light. Therefore, scattering is avoided, and the composites are transparent even at high metal filling factors. Thus the index of refraction can be tuned over a wide range. Furthermore, nanoparticles of metals exhibiting free electron behavior such as noble metals show a strong absorption maximum due to collective resonant oscillations of the conduction electrons, i.e. a localized particle surface plasmon resonance, which occurs generally in the visible region or the near infrared region of the optical spectrum. This gives rise to characteristic absorption peaks and a huge amplification of the electromagnetic field which can be further enhanced in highly filled nanocomposites.

The particle plasmon resonance frequency depends on many factors including size, shape, and filling factor of the metallic nanoparticles, as well as dielectric properties of the matrix. The plasmon resonance frequency can also be tuned by choosing alloy nanoparticles and adjusting the alloy composition. This is shown in the figure below for Au-Ag alloy particles in a Teflon AF matrix prepared by vapor phase co-deposition of the constituents from three independent sources simultaneously.


Tuning of the plasmon resonance in Ag-Au particles


Our recent work in close cooperation with the group of Prof. Mady Elbahri, who is now professor at Aalto University, has been focused on new plasmonic properties of highly filled particulate nanocomposites which are based on a coupling of localized particle surface plasmons of neighboring particles resulting in novel collective phenomena. Moreover, novel effects based on coupling of localized particle surface plasmons and propagating surface plasmons of metallic films have been explored.  Demonstrated applications range from transparent conductors showing a superior conductivity compared to ITO at comparable transparency to perfect absorbers in the visible and UV range.

Photoswitchable plasmonic nanocomposites are investigated in our joint work with Prof. Mady Elbahri within the Collaborative Research Center SFB 677 "Function by Switching". Here, the nanocomposites are combined with photoswitchable molecules. These chromophores change their properties reversibly upon irradiation with light of two different wavelengths. Very interesting new electro-optical properties arise through interactions between chromophores and localized particle surface plasmons as well as propagating surface plasmons. Moreover, we have developed new concepts of light-induced conductance switching without using chromophores whose intrinsic conductance is photoswitchable.

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Selected publications

Plasmon enhanced photocatalysis: see photocatalysis

Transparent metallic conductor

An Omnidirectional Transparent Conducting-Metal-Based Plasmonic Nanocomposite, Mady Elbahri, Mehdi Keshavarz Hedayati, Venkata Sai Kiran Chakravadhanula, Mohammad Jamali, Thomas Strunkus, Vladimir Zaporojtchenko and F. Faupel, Advanced Materials, Volume: 23, Issue: 17, Pages: 1993-1997.

Perfect absorbers

Keshavarz Hedayati, M.; Faupel, F.; Elbahri, M.: Review of Plasmonic Nanocomposite Metamaterial Absorber, Materials, Featured paper 7 (2014) 1221-1248.

Etrich, C.; Fahr, S.; Keshavarz Hedayati, M.; Faupel, F.; Elbahri, M.; Rockstuhl, C.: Effective Optical Properties of Plasmonic Nanocomposites, Materials 7 (2014) 727-741.

Hedayati, M.K.; Zillohu, A.U.; Strunskus, T.; Faupel, F.; Elbahri, M.: Plasmonic tunable metamaterial absorber as ultraviolet protection film, Applied Physics Letters 104 (2014) 041103.

Hedayati, M.K.; Faupel, F.; Elbahri, M.: Tunable broadband plasmonic perfect absorber at visible frequencies, Applied Physics A Online (2012) DOI 10.1007/s00339-012-7344-1.

Keshavarz Hedayati, M.; Javaherirahim, M.; Mozooni, B.; Abdelaziz, R.; Tavassolizadeh, A.; Chakravadhanula, V.S.K.; Zaporojtchenko, V.; Strunskus, T.; Faupel, F.; Elbahri, M.: Design of a perfect black absorber at visible frequencies using plasmonic materials, Advanced Materials Vol. 23 (2011) 5410-5414.

Photoswitchable plasmonic nanocomposites

Großmann, M.; Klick, A.; Lemke, C.; Falke, J.; Black, M.; Fiutowski, J.; Goszczak, A.J.; Sobolewska, E.; Zillohu, A.U.; Keshavarz Hedayati, M.; Rubahn, H.-G.; Faupel, F.; Elbahri, M.; Bauer, M.; Light-Triggered Control of Plasmonic Refraction and Group Delay by Photochromic Molecular Switches, ACS Photonics 2 (2015) 1327-1332.

Keshavarz Hedayati, M.; Javaheri, M.; Zillohu, A.U.; El-Khozondar, H.J.; Bawa'aneh, M.S.; Lavrinenko, A.; Faupel, F.; Elbahri, M.: Photo-driven Super Absorber as an Active Metamaterial with a Tunable Molecular-Plasmonic Coupling, Adv. Optical Mater 2 (2014) 705-710 ; Research Highlight, Nature Photonics 8, 499 (2014).

Keshavarz Hedayati, M.; Fahr, S.; Etrich, C.; Faupel, F.; Rockstuhl, C.; Elbahri, M.: The hybrid concept for realization of an ultra-thin plasmonic metamaterial antireflection coating and plasmonic rainbow, Nanoscale (2014) .

Light-induced conductance switching

Basuki, S.W.; Schneider, V; Strunkus, T.; Elbahri, M.; Faupel, F.; Light-Controlled Conductance Switching in Azobenzene-Containing MWCNT–Polymer Nanocomposites, ACS Appl. Mater. Interfaces 7(21) (2015) 11257-11262.

Schneider, V; Strunkus, T.; Elbahri, M.; Faupel, F.; Light-induced conductance switching in azobenzene based near-percolated single wall carbon nanotube/polymer composites, Carbon 90 (2015) 94-101.

Zaporojtchenko, V.; Pakula, C.; Basuki, S.W.; Strunskus, T.; Zargarani, D.; Herges, R.; Faupel, F.: Reversible light-induced capacitance switching of azobenzene ether/PMMA blends, Applied Physics A Vol. 102(2) (2011) 421.

Pakula, C.; Zaporojtchenko, V.; Strunskus, T.; Zargarani, D.; Herges, R.; Faupel, F.: Reversible light-controlled conductance switching of azobenzene based metal/polymer nanocomposites, Nanotechnology Vol. 21(46) (2010) 465201.

Harms, S.; Rätzke, K.; Pakula, C.; Zaporojtchenko, V.; Strunskus, T.; Egger, W.; Sperr, P.; Faupel, F.: Free volume changes on optical switching in azobenzene-PMMA blends studied by a pulsed low-energy positron beam, Journal Polymer Science, Part B: Polymer Physics Vol. 49(2) (2011) 404.


Earlier work on plasmonic nanocomposites

Beyene, H. T.; Chakravadhanula, V.S.K.; Hanisch, C.; Strunskus, T.; Zaporojtchenko, V.; Elbahri, M.; Faupel, F.: Vapour phase deposition, structure, and plasmonic properties of polymer-based composites containing Ag-Cu bimetallic nanoparticles, Plasmonics Vol. 7 Issue 1 (2011) 107-114.

Faupel, F.; Zaporojtchenko, V.; Strunskus, T.; Elbahri, M.: Metal-Polymer Nanocomposites for Functional Applications,Advanced Engineering Materials Vol. 12, Issue 12 (2010) 1177-1190.

Beyene, H. T.; Chakravadhanula, V.S.K.; Hanisch, C.; Elbahri, M.; Strunskus, T.; Zaporojtchenko, V.; Kienle, L.; Faupel, F.; Preparation and plasmonic properties of polymer based composites containing Ag-Au alloy nanoparticles produced by vapor phase co-deposition, Journal of Material Science Volume 45 Issue 21 (2010) 5865.

Chakravadhanula, V.S.K.; Elbahri, M.; Schürmann, U.; Greve, H.; Takele, H.; Zaporojtchenko, V.; Faupel, F.: Equal intensity double plasmon resonance of bimetallic quasi-nanocomposites based on sandwich geometry, Nanotechnology19(22) (2008) 225302/1-225302/5.

Vladimir Kochergin, Vladimir Zaporojtchenko, Haile Takele, Franz Faupel and Helmut Föll, J. Appl. Phys., 101, 024302 (2007).

H. Takele, U. Schürmann, H. Greve, D. Paretkar, V. Zaporojtchenko, and F. Faupel, Eur. Phys. J. Appl. Phys. (EPJAP), 33, 83 (2006).

U. Schürmann, H. Takele, V. Zaporojtchenko, and F. Faupel, Thin Solid Films, 515, 2, 801, 2 (2006).

U. Schürmann, W.A. Hartung, H. Takele, V. Zaporojtchenko, and F. Faupel, Nanotechnology, 16, 1078 (2005).

Biswas, O. C. Aktas, U. Schürmann, U. Saeed, V. Zaporojtchenko, T. Strunskus and F. Faupel, Appl. Phys. Lett., 84, 2655 (2004).