Buffalo: From airport security detecting explosives
to art historians authenticating paintings, society’s thirst
for powerful sensors is growing. Given that, few sensing techniques can match the buzz created by
surface-enhanced Raman spectroscopy (SERS). Discovered in the 1970s, SERS is a sensing technique prized for
its ability to identify chemical and biological molecules in a wide
range of fields. It has been commercialized, but not widely,
because the materials required to perform the sensing are consumed
upon use, relatively expensive and complicated to fabricate. That may soon change.
An international research team led by University at Buffalo
engineers has developed nanotechnology that promises to make SERS
simpler and more affordable.
Described in a research
paper published today in the journal Advanced Materials
Interfaces, the photonics advancement aims to improve our ability
to detect trace amounts of molecules in diseases, chemical warfare
agents, fraudulent paintings, environmental contaminants and
more.
“The technology we’re developing – a universal
substrate for SERS – is a unique and, potentially,
revolutionary feature. It allows us to rapidly identify and measure
chemical and biological molecules using a broadband nanostructure
that traps wide range of light,” said Qiaoqiang Gan, UB
assistant professor of electrical engineering and the study’s
lead author.
Additional authors of the study are: UB PhD candidates in
electrical engineering Nan Zhang, Kai Liu, Haomin Song, Xie Zeng,
Dengxin Ji and Alec Cheney; and Suhua Jiang, associate professor of
materials science, and Zhejun Liu, PhD candidate, both at Fudan
University in China.
When a powerful laser interacts chemical and biological
molecules, the process can excite vibrational modes of these
molecules and produce inelastic scattering, also called Raman
scattering, of light. As the beam hits these molecules, it can
produce photons that have a different frequency from the laser
light. While rich in details, the signal from scattering is weak
and difficult to read without a very powerful laser.
SERS addresses the problem by utilizing a nanopatterned
substrate that significantly enhances the light field at the
surface and, therefore, the Raman scattering intensity.
Unfortunately, traditional substrates are typically designed for
only a very narrow range of wavelengths. This is problematic
because different substrates are needed if scientists want to use a
different laser to test the same molecules. In turn, this requires
more chemical molecules and substrates, increasing costs and time
to perform the test.
The universal substrate solves the problem because it can trap a
wide range of wavelengths and squeeze them into very small gaps to
create a strongly enhanced light field.
The technology consists of a thin film of silver or aluminum
that acts as a mirror, and a dielectric layer of silica or alumina.
The dielectric separates the mirror with tiny metal nanoparticles
randomly spaced at the top of the substrate.
“It acts similar to a skeleton key. Instead of needing all
these different substrates to measure Raman signals excited by
different wavelengths, you’ll eventually need just one. Just
like a skeleton key that opens many doors,” Zhang said.
“The applications of such a device are
far-reaching,” said Kai Liu. “The ability to detect
even smaller amounts of chemical and biological molecules could be
helpful with biosensors that are used to detect cancer, Malaria,
HIV and other illnesses.”
It could be useful identifying chemicals used in certain types
of paint. This could be helpful detecting forged pieces of art as
well as restoring aging pieces of art. Also, the technology could
improve scientists’ ability to detect trace amounts of toxins
in the air, water or other spaces that are causes for health
concerns. And it could aid in the detection of chemical
weapons.
The National Science Foundation supported the research in a
grant to develop a real-time in-vivo biosensing system. Gan shares
the grant with Josep M. Jornet and Zhi Sun, both assistant
professors of electrical engineering at UB.
Gan is a member of UB’s electrical engineering optics and
photonics research group, which includes professors Edward Furlani,
Natalia Litchinitser and Pao-Lo Liu; and assistant professor Liang
Feng.
The group carries out research in nanophotonics, biophotonics,
hybrid inorganic/organic materials and devices, nonlinear and fiber
optics, metamaterials, nanoplasmonics, optofluidics,
microelectromechanical systems (MEMS), biomedical
microelectromechanical systems (BioMEMs), biosensing and quantum
information processing.
- See more at: http://www.buffalo.edu/news/releases/2015/05/050.html#sthash.wnWC55us.dpuf