Research and collaboration


Graphene is envisioned to be the most promising material for future applications in nanoscience. Due to its excellent and unusual electronic, optical and mechanical properties, graphene may lead to revolutionary innovations in flexible and transparent electronics, sensors, photonics, biomedical applications and so on. However, one of the main problems is that in most applications, modification of the properties of graphene is needed. We have recently discovered a novel method for patterning and tuning the electronic and optical properties of graphene via laser-induced oxidation.

In this method, we focus a laser beam of short (30 – 50 fs) pulses and with carefully controlled intensity (~1010 – 1011W/cm2) on graphene in ambient atmosphere containing oxygen which results in local oxidation of graphene. By moving the sample with respect to the laser beam we can write oxidized patterns on graphene. Electronic properties of graphene depend on the level of oxidation which allows us to control the electronic properties of oxidized areas by controlling the exposure parameters. The beauty of the method is that it allows us to write for example electronic components on graphene optically without any need for wet chemistry or lithographical methods. This we have demonstrated by patterning a field effect transistor by this method. Further modification of graphene is made possible by chemical functionalization of oxidized areas. Currently, we are studying the structure and composition of oxidized areas, functionalization and mechanism of oxidation in order to be able to control better the oxidation process which will lead to fabrication of complex functional structures.

The key method for the discovery was imaging of graphene by FWM spectroscopy. FWM produces very strong signal in graphene and there is high contrast between graphene and oxidized graphene which allows imaging of oxidized patterns with high sensitivity. We have filed a patent application on the method.

Researchers: Mika Pettersson, Andreas Johansson, Pasi Myllyperkiö, Jukka Aumanen, Juha Koivistoinen, Anna Ruokonen, Lucia Sladkova.


  1.  Patterning and tuning of electrical and optical properties of graphene by laser induced two-photon oxidation. J. Aumanen, A. Johansson, P. Myllyperkiö, J. Koivistoinen, M. Pettersson Nanoscale 7 (2015) 3319 – 3319.

Gold nanoclusters

A major question in nanoscience concerns behavior of systems when their size increases from a few atoms towards bulk. In fact, the properties of small molecules and bulk matter are reasonably well understood while nanoclusters and small particles need to be studied much more to understand their properties well. Thiolate-protected gold nanoclusters can be prepared with atomic precision in the size range of 1 – 2 nm offering a unique possibility to study the evolution of properties of clusters as a function of size.

We have used spectroscopic techniques for studying electronic and vibrational properties of gold nanoclusters. These studies have provided fundamental information on electronic energy level structure and on the properties of the ligand layer. Moreover, we are interested in conjugating gold nanoclusters in biological molecules which may open new ways to investigate and manipulate biomolecules.

Recently, we were able to reveal that molecular to metallic transition in ligand-protected gold nanoclusters occurs between 102 and 144 gold atoms. The study combined synthesis, characterization, ultrafast spectroscopy and DFT calculations of atomically precise gold nanoclusters. The key result was that Au102(pMBA)44 nanocluster shows energy relaxation dynamics characteristic of molecular systems while the Au144 cluster shows metallic behavior. This difference is due to the presence of a significant energy gap of ~0.5 eV in Au102 cluster while the Au144 cluster has no energy gap.

We are currently interested in electronic structure of clusters very close to the molecular-metallic transition. Furthermore, we are developing new methods for bioimaging based on gold nanoclusters.


  1. Molecule-like Photodynamics of Au102(pMBA)44 Nanocluster. S. Mustalahti, P. Myllyperkiö, S. Malola, T. Lahtinen, K. Salorinne, J. Koivisto, H. Häkkinen, M. Pettersson. ACS Nano 9(3) 2015 2328 – 2335.
  2. Electron microscopy of gold nanoparticles at atomic resolutionM. Azubel, J. Koivisto, S. Malola, D. Bushnell, G. L. Hura, A. L. Kohl, H. Tsunoyama, T. Tsukuda, M. Pettersson, H. Häkkinen, R. D. Kornberg, Science 345 (2014) 909 – 912.
  3. Ultrafast electronic relaxation and vibrational cooling dynamics of Au144(SC2H4Ph)60 nanocluster probed by transient mid-IR spectroscopy. S. Mustalahti, P. Myllyperkiö, T. Lahtinen, K. Salorinne, S. Malola, J. Koivisto, H. Häkkinen, M. Pettersson, J. Phys. Chem. C, 118 (2014) 18233 – 18239.
  4. Site-specific targeting of enterovirus capsid by functionalized monodisperse gold nanoclusters. V. marjomäki, T. Lahtinen, M. Martikainen, J. Koivisto, S. Malola, K. Salorinne, M. Pettersson, H. Häkkinen, Proc. Nat. Acad. Sci. 111 (2014) 1277 – 1281.
  5. Vibrational perturbations and ligand-layer coupling in a single crystal of Au144(SC2H4Ph)60 nanocluster. J. Koivisto, K. Salorinne, S. Mustalahti, T. Lahtinen, S. Malola, H. Häkkinen, M. Pettersson, J. Phys. Chem. Lett. 5 (2014) 387 – 392.
  6. Nondestructive size determination of thiol-stabilized gold nanoclusters in solution by diffusion ordered NMR spectroscopy. K. Salorinne, T. Lahtinen, J. Koivisto, E. Kalenius, M. Nissinen, M. Pettersson, H. Häkkinen, Anal. Chem. 85 (2013) 3489 – 3492.
  7. Experimental and theoretical determination of the optical gap of the Au144(SC2H4Ph)60 cluster and  the (Au/Ag)144(SC2H4Ph)60 nanoalloys. J. Koivisto, S. Malola, C. Kumara, A. dass, H. Häkkinen, M. Pettersson, J. Phys. Chem. Lett. 3 (2012) 3076 – 3080.
  8. Electronic and vibrational signatures of the Au102(p-MBA)44 cluster. E. Hulkko, O. Lopez-Acevedo, J. Koivisto, Y. Levi-Kalisman, R. D. Kornberg, M. Pettersson, H. Häkkinen. J. Am. Chem. Soc. 133 (2011) 3752 – 3755.
  9. Characterization of iron-carbonyl-protected gold clusters. O. Lopez-Acevedo, J. Rintala, S. Virtanen, C. Femoni, C. Tiozzo, H. Grönbeck, M. Pettersson, H. Häkkinen, J. Am. Chem. Soc. 131 (2009) 12573 – 12575.

Carbon nanotubes

Carbon nanotubes have remarkable properties making them good candidates for many applications varying from strengthening of materials to supercapacitors, chemical sensors and molecular electronics. However, lack of large scale synthesis of carbon nanotubes with specific structure hinders development of many applications. Specific information on carbon nanotubes can be obtained at a single nanotube level. Our approach is to study single walled carbon nanotubes (SWCNT) at an individual tube level by optical spectroscopy. To this end, we have developed methodology for producing samples where individual SWCNTs are suspended over a slit.

This provides an optimal configuration for optical studies since there is no background from substrate. Moreover, the structure of the tubes can be determined by electron diffraction which allows obtaining structure-specific information. We are interested in nonlinear spectroscopic measurements of individual SWCNTs. We are applying four wave mixing (FWM) and second harmonic generation (SHG) for studying issues such as excitonic dynamics, photo-oxidation and chirality induced SHG.


  1. Local photo-oxidation of individual single walled carbon nanotubes probed by femtosecond four wave mixing imaging. J. Aumanen, A. Johansson, O. Herranen, P. Myllyperkiö, M. Pettersson, Phys. Chem. Chem. Phys. 17 (2015) 209 – 216.
  2. Measurement of optical second-harmonic imaging from an individual single-walled carbon nanotube. M. J. Huttunen, O. Herranen, A. Johansson, H. Jiang, P. R. Mudimela, P. Myllyperkiö, G. Bautista, A. G. Nasibulin, E. I. Kauppinen, M. Ahlskog, M. Kauranen, and M. Pettersson, New J. Phys. 15 (2013) 083043.
  3. Water-soluble carbon nanotubes through sugar azide functionalization. H. Leinonen, M. Pettersson, M. Lajunen. Carbon, 49 (2011) 1299 – 1304.
  4. Femtosecond four-wave-mixing spectroscopy of suspended individual semiconducting single-walled carbon nanotubes. P. Myllyperkiö, O. Herranen, J. Rintala, H. Jiang, P. R. Mudimela, Z. Zhu, A. G. Nasibulin, A. Johansson, E. I. Kauppinen, M. Ahlskog, M. Pettersson, ACS Nano, 4 (2010) 6780 – 6786.
  5. Effect of alumina/Iron catalysts with the use of different ferrous compounds on the formation of carbon nanotubes. X. Zhang, J.-P. Nikkanen, J. Rintala, M. Pettersson, T. Kanerva, J. Laakso, E. Levänen, T. Mäntylä, J. Ceram. Sci. Tech. 01 (2010) 51 – 54.
  6. New nitrene functionalizations onto sidewalls of carbon nanotubes and their spectroscopic analysisH. Leinonen, J. Rintala, A. Siitonen, M. Lajunen, M. Pettersson, Carbon, 48 (2010) 2425 – 2434.
  7. Electronic transport measurements and Raman spectroscopy on carbon nanotube devices. O. Herranen, J. Rintala, A. Johansson, P. Queipo, A. G. Nasibulin, E. I. Kauppinen, M. Pettersson, M. Ahlskog, Phys. Stat. Solidi B, 246 (2009) 2853 – 2856.
  8. Raman spectroscopy and low temperature transport measurements of individual single walled carbon nanotubes with varying thickness. J. Rintala, O. Herranen, A. Johansson, M. Ahlskog, M. Pettersson, J. Phys. Chem. C, 113 (2009) 15398 – 15404.
  9. Temperature dependence of electronic transitions of single-wall carbon nanotubes: Observation of an abrupt blueshift in near infrared absorption. Anni Siitonen, Henrik Kunttu, and Mika Pettersson, J. Phys. Chem. C 111 (2007) 1888.

Applied spectroscopy

In this research we use spectroscopic knowledge to develop new techniques and instruments for various applications, or use spectroscopy for solving questions in various fields. The research is heavily motivated by industrial aspects and we are eager to collaborate with industry in their problems. In particular, we have found many times that we are able to solve questions which industry has presented to us. Thus, we encourage you to contact us if you have a specific problem in mind that might be suitable for our expertise.

Here are some examples of projects:


Recenart is multidisciplinary project aiming at investigations of art pieces. The project involves art historians, chemists, physicists and IT experts in a unique team that can bring into light new knowledge about the art pieces under investigation. Our group is specifically developing a nanotechnology based security marking method for original items. We are also using Raman spectroscopy for material research of art.

NinGas Gas analyser

We have developed non-invasive gas analysis technology based on Raman spectroscopy. Our unique NinGas analyser is able to measure quantitatively gases such as oxygen, nitrogen, carbon dioxide or hydrogen inside a closed volume in few seconds. Typical application areas are food industry (modified atmosphere packaging) and process industry. This technology is available for commercialization. We can also make instruments by order.