Research

Spintronics with chiral molecules Sensors – Molecular Controlled Semi-conductor Resistor (MOCSER)  Interaction of electrons with organic and bio-molecules Nanoparticles based hybird systems Chemical Surface Patterning

Nanoparticles based hybird systems

Charge and energy transfer in hybrid organic-inorganic systems

In this project, our goal is to explore, control, and direct charge or energy transfer processes in self-assembled hybrid (organic-inorganic) nano-systems. We developed a technique to adsorb self-assembled monolayers (SAM) on various substrates (quartz, silicon, GaAs, gold etc.) and on top of that, layers of nanoparticles (NPs) by using bi-functional organic linkers (as seen in the cartoon below and by SEM images).


 

 

 

 

 

 

 

 

 

We utilize contact potential difference (CPD) measurements together with conductivity and photoluminescence (PL) spectroscopy measurements to detect the charge- and energy-transfer processes and to probe the influence of the substrate, the hierarchy of NPs, the temperature, and the properties of the organic linker on these transfer processes within the nano-assemblies.

We showed that the adsorption of bifunctional dithiolated alkyl linkers on a monolayer of NPs couples them electronically and allow charge transfer processes within the layer. It was found that energy transfer between the NPs in the bilayer occurs by the Dexter mechanism and that the efficiency of this process depends on the linker properties and the temperature, as can be seen by the PL spectra below for the different assemblies at room temperature and 80K.

Finally we showed that the properties of this type of structures depend on the semiconductor substrate on which they are adsorbed. While charge transfer interactions with the GaAs substrate were found not to depend on the system’s order (i.e., how the NPs are adsorbed relative to the substrate), energy transfer processes do depend on the hierarchy of the adsorbed NPs.

• G. Gotesman, D. H. Waldeck, R. Naaman, J. Phys. Chem. A, 2009, 113, 7213.
• G. Gotesman, R. Naaman, J. Phys. Chem. Lett., 2010, 1, 594.

 

Charge transport in hybrid organic-inorganic nanoparticles-based devices

For further work on NPs assemblies, we developed a device that is based on self-assembly of NPs coupled via bifunctional organic linkers (see cartoon and SEM image below). The contacts of the device are prepared by optical lithography and Au evaporation. A layer of NPs is assembled on the device and organic linkers are adsorbed between the NPs to electronically couple them. Such device enables us to study the molecular transport properties by a macro-scale device. Furthermore, we are developing electrical and magnetic applications based on these unique properties.

 


For more details on specific projects, see the following:

  Electron spin and chiral molecules

  Sensors – Molecular Controlled Semi-conductor Resistor MOCSER
  Interaction of electrons with organic and bio-molecules
  Charge and energy transfer in hybrid organic-inorganic systems
  Chemical Surface Patterning