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Many organic contaminants in the
air and in drinking water need to be detected at very low-level concentrations.
Research published by the laboratory of Prashant V. Kamat, the John A. Zahm
Professor of Science at the University of Notre Dame, could be beneficial in
detecting those contaminants.
The Kamat laboratory uses
surface-enhanced Raman spectroscopy to make use of silver nanoparticles to
increase the sensitivity limit of chemical detection. Researchers in this study
have prepared a semiconductor-graphene-metal film that has distinct advantages:
The absorption of organic molecules on the film’s graphene surface increases
the local contaminant concentration adjacent to silver nanoparticles.
The researchers have investigated
the use of graphene-oxide films in which the semiconductor titanium dioxide and
metal nanoparticles are deposited on opposite sides of the graphene surface. “We are currently working toward the detection of environmental contaminants at
even lower levels,” Kamat says. “Careful control of metal size and loading will
be the key to optimize strips for testing water quality.”
Under ultraviolet (UV) illumination,
the electrons from titanium dioxide are captured by the graphene-oxide film and
shuttled across the film to reduce metal ions into metal nanoparticles. This
electron-hopping process across the graphene-oxide film allows the design of a
side-separated semiconductor-metal nanoparticle architecture.
Graphene is known for its
remarkable mechanical strength, very high thermal and electrical conductivity,
and broad variety of applications. While the conducting properties of graphene
sheets deposited on various substrates are well understood, the Kamat group has
demonstrated that the transport of electrons is not limited to the 2D plane.
Here, the hopping of electrons from one side of the graphene allows for the
side-selective deposition of silver nanoparticles.
“Another potential application is
in the area of photocatalytic generation of solar fuels,” Kamat says.
“For example, having semiconductor nanoparticles on one side of a graphene
sheet and a metal catalyst on the other side, one can create a hybrid assembly
that can selectively split water into oxygen and hydrogen.”
The paper research was published
in the Journal of Physical Chemistry
Letters.
Source: University of Notre Dame
