Research interests

The group studies nanoelectronics and -plasmonics/-photonics, concentrating on phenomena related to molecules. The group has a long experience on self-assembled DNA structures, like DNA origami, and their modifications and utilization in nanofabrication of electrical and optical/plasmonic nanodevices. For example, The group has developed a highly parallel DNA origami based fabrication method (DALI: DNA assisted lithography) for arbitrary shaped metallic nanostructures for plasmonics and metamaterial fabrication, as well as fabricated a DNA-assembled single electron transistor operating at room temperature. 

Another main interest of the group is a coupling between surface plasmons or cavity photons and molecules, especially in a strong coupling limit. This limit brings about hybrid plasmon-molecule -states possessing new fundamental properties. For example, it enables totally new ways for controlling chemistry. In collaboration with group of Prof. Gerrit Groenhof we are developing and a new theory and experiments proving it, for a field of polariton chemistry.  

Other topics studied are molecular level mechanisms and properties of fluorescent proteins, enhancing their fluorescence for bioimaging by plasmonics, and utilization of plasmonics for solar energy, as well as plasmonic/optical properties of graphene and conducting polymers.

Selected publications

Optical monitoring of DNA conformation controlled by electric field

In collaboration with University of Tampere and BioNavis Ltd, we have developed a novel nanoactuator system, where conformation of biomolecule can be tuned by electric field while simultaneously probed using optical properties of gold nanoparticle. In the current study, we demonstrated that AuNPs anchored via hairpin-DNA molecule experienced additional discretization in their motion due to opening and closing of the hairpin-loop compared to the plain, single stranded DNA.

K. Tapio, D. Shaoa, S. Auer, J. Tuppurainen, M. Ahlskog, V.P. Hytönen, J.J. Toppari, 
Nanoscale, in press

Plasmonic nanostructures through DNA-assisted lithography

We report on a new fabrication technique combining programmable DNA origami shapes and conventional lithography methods to create metallic nanoantennas and chiral shapes for diverse applications. This new highly parallel technique called DALI (DNA-assisted lithography) enables to fabricate precise metallic nanostructures with designed plasmonic properties by means of different self-assembled DNA origami shapes.

B. Shen, V. Linko, K. Tapio, S. Pikker, T. Lemma, A. Gopinath, K.V. Gothelf, M.A. Kostiainen, J.J. Toppari
Science Advances. 4, eaap8978 (2018). 

Dynamics of strongly coupled modes between surface plasmon polaritons and photoactive molecules: the effect of the Stokes shift

S. Baieva, O. Hakamaa, G. Groenhof, T.T. Heikkilä, J.J. Toppari
ACS Photonics, 4, 28 (2017).

Toward Single Electron Nanoelectronics Using Self-Assembled DNA Structure 

K. Tapio, J. Leppiniemi, B. Shen, V.P. Hytönen, W. Fritzsche, J.J. Toppari
Nano Letters, 16, 6780 (2016).