Researchers have crafted molecular wires featuring regular twists. By adjusting the lengths of sections between these twists, they are able to boost the electrical conductivity of individual polymer chains. This breakthrough has the potential to pave the way for innovative organic electronics or even single-molecule wires.
From the high-voltage cables transporting electricity over lengthy distances to the tungsten filaments in incandescent bulbs, we tend to associate electrical conductors with metal. However, for many years, scientists have been exploring advanced materials based on carbon-based oligomer chains capable of conducting electricity as well. These materials are used in organic light-emitting devices found in some contemporary smartphones and computers.
In the realm of quantum mechanics, electrons aren’t simply pinpoint particles with specific locations; they can become ‘delocalized’ across a space. A molecule featuring a long sequence of alternating single and double bonds possesses pi-conjugation, enabling conductive polymers to allow delocalized electrons to leap between pi-conjugated sections—much like a frog hopping from one puddle to another. However, variations in energy levels between adjacent regions limit the efficacy of this process. Creating oligomers and polymers that maintain more uniform energy levels could enhance electrical conductivity, which is crucial for advancing new practical organic electronics or even single-molecule wires.
Recently, a study published in The Journal of the American Chemical Society by researchers from SANKEN (The Institute of Scientific and Industrial Research) at Osaka University revealed the creation of a number of nanometer-scale molecular wires with consistent twists. Unlike earlier efforts that utilized a single long chain able to rotate in various ways, these oligomers were made up of rigid fused regions divided by evenly spaced twists. The researchers demonstrated that their samples achieved higher conductance compared to non-fused oligothiophenes. “By meticulously controlling the dimensions of these pi-conjugated areas, we attained high single-molecule conductance in these oligomers using rigid molecular designs,” explains Ryo Asakawa, the lead author.
These researchers see potential in applying this technique to create new organic electronic devices, which could be produced more affordably as thin chemical films on flexible substrates, unlike traditional silicon-based processes that often necessitate specialized clean rooms and lithography techniques for production. “We anticipate that this research will foster improvements in single-molecule electronics and organic thin-film devices,” notes senior author Yutaka Ie. There’s even a possibility that individual molecular wires could serve as biocompatible sensors within living cells.
