Researchers working at Penn State have developed a sensor based on Raman spectroscopy using nitrogen-doped graphene as a substrate. The sensor can detect trace amounts of molecules in a solution.
For their experiments, the researchers chose three types of fluorescent dye molecules. Fluorescent dyes are particularly hard to detect in Raman spectroscopy because the fluorescence tends to wash out the signal, the researchers report. However, when the dye is added to the graphene or N-doped graphene substrate, the fluorescence is quenched.
The researchers describe their work in a paper titled “Ultrasensitive Molecular Sensor Using N-doped Graphene through Enhanced Raman Scattering” published online July 22 in the journal Science Advances. Mauricio Terrones, professor of physics, chemistry, and materials science at Penn State, led the research. Researchers from Brazil, China, and Japan contributed to this work while visiting Terrones’ lab at Penn State.
“By controlling nitrogen doping we can shift the energy gap of the graphene, and the shift creates a resonance effect that significantly enhances the molecule’s vibrational Raman modes,” said lead author Simin Feng, a graduate student in Terrones’ group, as reported at Newswise.
“This is foundational research,” added Ana Laura Elias, a coauthor and research associate in Terrones’ lab. “It is hard to quantify the enhancement because it will be different for every material and color of light. But in some cases we are going from zero to something we can detect for the first time. You can see a lot of features and study a lot of physics then. To me the most important aspect of this work is our understanding of the phenomenon. That will lead to improvements in the technique.”
“We carried out extensive theoretical and experimental work,” Terrones added. “We came up with an explanation of why nitrogen-doped graphene works much better than regular graphene. I think it’s a breakthrough, because in our paper we explain the mechanism of detecting certain molecules.”
The team expects the technique to be effective in detecting trace amounts of organic molecules, including dangerous viruses.
Terrones is director of the Center for Two-Dimensional and Layered Materials (2DLM) at Penn State’s Materials Research Institute.
In related news, representatives of the Penn State Materials Research Institute were on hand at SEMICON West in San Francisco earlier this month to highlight several research initiatives, including the development of ultrasensitive gas sensors based on the infusion of boron atoms into graphene. The sensors were able to detect nitrogen oxides in parts per billion and ammonia in parts per million.
Other initiatives highlighted at SEMICON West included single-molecule detection of contaminants, explosives, or diseases using surface-enhanced Raman scattering (SERS); in situ transmission electron microscopy (TEM); transparent metal films for smartphone, tablet, and TV displays; and 3D printing of patterned membranes.
In addition, the National Science Foundation announced in March the award of $17.8 million over five years to Penn State to fund the Two-Dimensional Crystal Consortium (2DCC)—one of two Materials Innovation Platform national user facilities in the country. The funds will allow the 2DCC to acquire or build specialized equipment used to grow ultrathin crystalline chalcogenide materials.
“At Penn State, our focus will be on 2D materials that are only a few atoms thick, and specifically on materials called chalcogenides, which are layered compounds that contain elements such as sulfur, selenium, and tellurium,” said Joan Redwing, professor of materials science and engineering, chemical engineering, and electrical engineering at Penn State, in a press release. “By controlling the growth of these materials on an atomic scale, we will create materials with unique properties and exotic quantum states that offer the potential to revolutionize future electronic technologies.”