Dec 15, 2017
graphene
UCLA researchers have developed a novel method for creating graphene nanoribbons which can be used to make better electronics.
 
In a study published in October, researchers led by chemistry professors Yves Rubin, Richard Kaner, and Ken Houk developed a two-step synthesis to make graphene nanoribbons (GNRs). Graphene nanoribbons have unique electrical properties that allow them to be used as semiconductors in electronics.
 
Professors Yves Rubin, Richard Kaner, and Ken Houk
 
The research is the lead article on UCLA Newsroom’s Science and Technology website and it has been featured by several science news websites including Phys.org, ScienceDaily, and Nanowerk News.
 
Graphene is a form of carbon with favorable electrical properties, but the most common form of graphene lacks a band gap. A band gap is the energy barrier that allows a semiconductor to conduct electricity only when the energy barrier is met. Without a band gap, a material cannot be used in modern electronics as it will always conduct electricity: it’s always “on” and can’t be turned on or off. 
 
In order to make graphene a useful material for electronics, UCLA researchers devised a way to create a form of graphene with a band gap. The researchers created graphene nanoribbons, strips of graphene, which naturally possess a band gap. 
 
The new process for creating GNRs takes two steps. In the first step, researchers took building blocks for making GNRs and formed them into white crystals. The researchers then exposed these white crystals to UV light to assemble them into long polymer chains, chains that took on a deep purple or black color. 
 
In the second step, the researchers heated the polymers up to 600 degrees Celsius for one hour. The heat caused the polymers to react to form the backbone of the GNRs and trimmed away chemical impurities, forming pristine GNRs.
Visualizing the GNRs by electron microscopy, the researchers found that the GNRs were 1.2 nm wide (DNA is about twice as wide) and were bundled together. According to the study, incorporating different atoms into the GNRs, which might change physical or chemical properties of GNRs, might be possible by simply choosing different building blocks at the start of the process.
 
The paper titled “Synthesis of N = 8 Armchair Graphene Nanoribbons from Four Distinct Polydiacetylenes” was published in the October 30, 2017 issue of the Journal of the American Chemical Society. Alumnus Dr. Robert Jordan (Ph.D. ’16 chemistry – Rubin) was the lead author on the paper. Co-authors were graduate students Yolanda Li (Rubin), Cheng-Wei Lin (Kaner), alum Ryan McCurdy (B.S. ’16 chemistry - Rubin), graduate students Janice Lin (Houk), Jonathan Brosmer (Zink), Kristofer Marsh (Kaner), crystallographer Dr. Saeed Khan (UCLA’s Molecular Instrumentation Center), Profs. Ken Houk, Richard Kaner, and Yves Rubin.
 
Many thanks to Joseph Ong for writing this article.