Heteroatomic nanohoops, structures previously only made with carbon atoms, have been produced. The introduction of different atoms can be used to tune the nanostructure's photoelectronic properties.
These unique circular structures, which are capable of the efficient absorbtion and distribution of energy, could be used in organic LEDs, solar cells or as novel medical probes and sensors.
The idea behind the nanohoops came from Ramesh Jasti, who synthesized these unique molecules for the first time in 2008. Jasti created the miniature organic circular structures using carbon atoms with the aim to enhance carbon nanotubes. However, during the course of his research, he realized that his process could be used as a standalone method.
In this latest research, Jasti and five researchers from the University of Oregon demonstrated that the nanohoops, also referred to as cycloparaphenylenes, can be created from other atoms besides carbon.
The nanohoops, which hardly measure 1nm across, form a new range of structures that are sized somewhere between long-chained polymer structures and small, low-mass molecules.
These structures add to the toolbox and provide a new way to make organic electronic materials. Cyclic compounds can behave like they are hundreds of units long, like polymers, but be only six to eight units around. We show that by adding non-carbon atoms, we are able to move the optical and electronic properties around.
If you can control the band gap, then you can control the color of light that is emitted, for example in an electronic device, you also need to match the energy levels to the electrodes. In photovoltaics, the sunlight you want to capture has to match that gap to increase efficiency and enhance the ability to line up various components in optimal ways. These things all rely on the energy levels of the molecules. We found that the smaller we make nanohoops, the smaller the gap.
Ramesh Jasti - University of Oregon
Darzi synthesized many nanohoops using carbon and nitrogen atoms to study their properties as a means of testing the teams theory.
The addition of other elements like nitrogen gives us another way to manipulate the energy levels, in addition to the nanohoop size. We’ve now shown that the nanohoop properties can be easily manipulated and, therefore, these molecules represent a new class of organic semiconductors — similar to conductive polymers that won the Nobel Prize in 2000. With nanohoops, you can bind other things in the middle of the hoop, essentially doping them to change properties or perhaps sense an analyte that allows on-off switching.
Ramesh Jasti - University of Oregon
Jasti’s earlier work focused on the development of carbon-based nanohoop compounds, with the vision to make them in a variety of diameters and then integrate them into existing technologies. However, his team began to realize that they possessed unanticipated optical and electronic properties.
In 2014, Jasti moved his research from Boston University to the Department of Chemistry and Biochemistry at the University of Oregon. Jasti was the recipient of the 2013 National Science Foundation Career Award.
The main reason for his move to the University of Oregon was the solar cell research being conducted by his colleagues in the Materials Science Institute, a department he is also a member of.
We haven't gotten very far into the application of this. We're looking at that now. What we were able to see is that we can easily manipulate the energy levels of the structure, and now we know how to exchange any atom at any position along the loop. That is the key discovery, and it could be useful for all kinds of semiconductor applications.
Ramesh Jasti - University of Oregon