Material could be used to make better filters, more efficient sensors, and faster catalysts
For the first time, scientists have created a material with a gradient of gold nanoparticles on a silica covered silicon surface using a molecular template. The material, which was developed at North Carolina State University (NCSU) and tested at theNational Synchrotron Light Source(NSLS) at the U.S. Department of Energy’s Brookhaven National Laboratory, provides the first evidence that nanoparticles — each about one thousand times smaller than the diameter of a human hair — can form a gradient of decreasing concentration along a surface. A description of the material appears as the cover story in the July 23 issue of Langmuir.
“This material promises to be the first in a series with many applications in electronics, chemistry, and the life sciences,” said Rajendra Bhat, a Ph.D. student from North Carolina State University (NCSU) and the lead author of the study. Bhat worked with Jan Genzer, a chemical engineering professor at NCSU, and Daniel Fischer, a physicist from the U.S. Department of Commerce’s National Institute of Standards and Technology (NIST).
"Top: Images of gold nanoparticles attached to the silica surface at different distances from the most populated end of the substrate. As the distance increases, the number of particles decreases, revealing a particle gradient. Bottom: Simplified representation of the material showing particles in decreasing concentration along the surface. "
To build the material, the scientists first prepared a very thin layer of organosilanes, sticky molecules with a head and a tail, on a rectangular surface of silica. The head glues to the surface, while the tail sticks out, acting like a hook waiting for a gold nanoparticle to attach to it, explained Genzer, leader of the NCSU team. The molecules, emitted vertically in the form of a vapor by a source close to one side of the surface, slowly fell on it with decreasing concentration as the distance from the source increased, thus creating a gradient to serve as a molecular template.
The next step was to dip the material in a solution containing the gold nanoparticles, each of which was coated with a negatively charged chemical. In the solution, the tails of the organosilane molecules took on a positive charge, so the negatively charged gold particles attached to the oppositely charged tails underneath.
To visualize the gradient of gold particles, Bhat and his colleagues used an atomic force microscope, in which a tiny needle moves along the surface, following its bumps and valleys to reveal its topography. To look at the gradient of the organosilane molecules, the scientists used a technique called near-edge x-ray absorption fine structure (NEXAFS). In NEXAFS, extremely intense x-ray light is sent toward the material, and the electrons emitted by the material and collected with a sensitive detector provide information about the concentration of the organosilane molecules on the surface.
“The distinguishing feature of our approach is that the particles follow a pre-designed chemical template provided by the organosilane sticky groups,” said Genzer. “The ability to manipulate the underlying template allows us to prepare gradient structures of nanoparticles with varying characteristics.”
The main advantage of the gradient structure is that large numbers of structures can be combined on a single substrate and used for high-throughput processing. It might, for example, save time for chemists testing clusters of nanoparticles used as catalysts — chemicals actively sought by the chemical industry to create new, less polluting sources of energy. “Clusters made of different numbers of nanoparticles could be put on a single surface, and scientists could test this surface only once in a chemical reaction, instead of having to run each cluster separately through the reaction,” Fischer said. The material could also be used as a sensor to detect species that have specific affinities for nanoparticles, or as a filter to select particles of given sizes.
Bhat and his colleagues are now exploring the properties of similar materials, with different “sticky” substances and nanoparticles. “This research is so new that we are still thinking of potential applications for these materials,” he said.
This research was funded by the U.S. Department of Energy, which supports basic research in a variety of scientific fields, the National Science Foundation, and the Department of Commerce.
The U.S. Department of Energy’s Brookhaven National Laboratory conducts research in the physical, biomedical, and environmental sciences, as well as in energy technologies. Brookhaven also builds and operates major facilities available to university, industrial, and government scientists. The Laboratory is managed by Brookhaven Science Associates, a limited liability company founded by Stony Brook University and Battelle, a nonprofit applied science and technology organization.
Patrice Pages | NewsRelease
The Internet of Things: TU Graz researchers increase the dependability of smart systems
18.02.2019 | Technische Universität Graz
Stanford researchers create a wireless, battery-free, biodegradable blood flow sensor
09.01.2019 | Stanford University
DESY and MPSD scientists create high-order harmonics from solids with controlled polarization states, taking advantage of both crystal symmetry and attosecond electronic dynamics. The newly demonstrated technique might find intriguing applications in petahertz electronics and for spectroscopic studies of novel quantum materials.
The nonlinear process of high-order harmonic generation (HHG) in gases is one of the cornerstones of attosecond science (an attosecond is a billionth of a...
Nano- and microtechnology are promising candidates not only for medical applications such as drug delivery but also for the creation of little robots or flexible integrated sensors. Scientists from the Max Planck Institute for Polymer Research (MPI-P) have created magnetic microparticles, with a newly developed method, that could pave the way for building micro-motors or guiding drugs in the human body to a target, like a tumor. The preparation of such structures as well as their remote-control can be regulated using magnetic fields and therefore can find application in an array of domains.
The magnetic properties of a material control how this material responds to the presence of a magnetic field. Iron oxide is the main component of rust but also...
Due to the special arrangement of its molecules, a new coating made of corn starch is able to repair small scratches by itself through heat: The cross-linking via ring-shaped molecules makes the material mobile, so that it compensates for the scratches and these disappear again.
Superficial micro-scratches on the car body or on other high-gloss surfaces are harmless, but annoying. Especially in the luxury segment such surfaces are...
The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.
A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...
Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.
"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...
11.03.2019 | Event News
01.03.2019 | Event News
28.02.2019 | Event News
25.03.2019 | Life Sciences
25.03.2019 | Life Sciences
25.03.2019 | Life Sciences