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Robinson’s work spans the making of nanoscale building blocks and altering their capabilities to assembling nanoparticles into practical devices like batteries and printed electronics. Robinson’s work spans the making of nanoscale building blocks and altering their capabilities to assembling nanoparticles into practical devices.
Jesse Winter
Jesse Winter

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“It’s my passion to be able to really understand the physics and chemistry of my nanomaterials,” says Robinson. “It’s my passion to be able to really understand the physics and chemistry of my nanomaterials,” says Robinson.
Jesse Winter
Jesse Winter

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“Once we understand more about how to use chemical transformations to make new materials, we can synthesize materials and transform them to have exactly what we want.” “Once we understand more about chemical transformations in nanoparticles, we will be able to take our synthesized nanomaterials and manipulate the atoms, tailoring them into exactly what we want."
Jesse Winter
Jesse Winter

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The Richardson lab investigates how to scale synthesis procedures for nanoparticles, other than traditional hot injection. The Robinson lab investigates how heat behaves at the nanoscale by using their home-built nanoscale phonon spectrometer.
Jesse Winter
Jesse Winter

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Members of Robinson’s lab Members of Robinson's lab
Jesse Winter
Jesse Winter

The Making of Nanomaterials

by Alexandra Chang

When Richard Robinson, Materials Science and Engineering, was a master's student in engineering, he took a class called Solid State Physics. In the course, the professor described heat as particles, “phonons,” and heat transfer as a lattice vibration, meaning that heat is transferred through a material just through vibrations. Learning this clicked with Robinson.

“I realized that the answers I had been looking for cut a little deeper than what I had been learning in traditional engineering,” he says. “I wanted to go further upstream and learn about the physics and chemistry of materials, to really understand on the fundamental level, the kinds of things I wanted to make.”

Robinson switched focus and pursued a PhD in Applied Physics, followed by a postdoctoral fellowship in chemistry.

Today, Cornell’s Materials Science and Engineering department is a perfect home for Robinson, whose research interests lie in the studying and engineering of nanoscale materials. His work spans from making the nanoscale basic building blocks and altering their capabilities, to assembling nanoparticles into functional devices for various energy applications, like batteries, supercapacitors, printed electronics, fuel cells, and solar cells. Robinson and his lab also test the devices to better understand how they work, the relationship between a nanomaterial’s structure and processing, and the resulting properties.

Scaling Up Nanomanufacturing

One goal of Robinson’s research is scalable nanomanufacturing: to meet the future demands for nanoparticles in energy and technology applications, he studies how to scale the synthesis procedures for nanoparticles. For more than two decades, nanoparticle synthesis has been based on a solution-phase chemistry in which researchers quickly inject a precursor into a hot matrix of an organic solution. The injection event initiates the nanoparticle’s nucleation and growth.

To scale up this process, a method of synthesis other than traditional hot injection is required. Robinson and Tobias Hanrath, Chemical and Biomolecular Engineering, are researching methods that don’t require an injection event. They were recently awarded a $1.5 million National Science Foundation center grant to work on scaling this process for nanoparticle use in devices such as batteries, solar cells, and lighting.

The Robinson and Hanrath team has so far developed a modified synthesis that makes 100 times more nanoparticles than previously possible. The main challenge is in making consistent, perfectly sized nanoparticles. Once the researchers achieve this, the use of nanoparticles will expand to a broad range of applications. Robinson says that they are specifically looking into quantum dots for light-emitting diode (LED) lighting, which would increase efficiency across the industry.

Nanoparticle Synthesis—Creating Circuits, Creating a Revolution

Colloidal nanoparticle synthesis also has an impact in the world of printable electronics. Solution-phase chemistry is 10 to 100 times cheaper than having to go to a clean room to make nanoparticles. It’s also far simpler.

“We could create a new revolution in circuit building,” says Robinson. “People could print new circuits from their home printers.”

Though this revolution hasn’t quite hit yet, Robinson’s lab has developed a process for taking copper sulfide nanoparticles and putting them onto a substrate to get high electrical conductivity and mobility without having to use high-temperature processing, which is the norm for the field. The next step is to direct these nanoparticles to create circuits.

Atomic Diffusion at CHESS

Robinson says Cornell’s facilities—including the Cornell High Energy Synchrotron Source (CHESS) and the Cornell NanoScale Science and Technology Facility (CNF)—have been crucial to his research, especially when it comes to testing and measuring various aspects of nanomaterials.

Material properties change dramatically at the nanoscale, and people have not figured out how to quantify all of the properties. Robinson and his group are particularly interested in atomic diffusion—the speed at which atoms diffuse in a material—and heat transfer.

The researchers have pioneered a method to measure atomic diffusion, in conjunction with CHESS staff. Atomic diffusion is important during chemical transformation of a nanomaterial from one form to another. Using x-ray absorption spectroscopy, the researchers take pictures of the structural and compositional changes at an atomistic level. They then use advanced analysis to decipher the atomistic structural changes.

Results from their work will enable the researchers to understand how and why transformations are different in nanoscale materials and will enable the team to tailor the nanoscale building blocks to have specific properties and higher functionality.

“Every time we analyze these experiments we’ve seen some new nanoscale mechanism we haven’t seen before,” says Robinson. “But because these findings are completely new to the field, the results also lack explanation, so we’re trying to explain them. Once we understand more about chemical transformations in nanoparticles, we will be able to take our synthesized nanomaterials and manipulate the atoms, tailoring them into exactly what we want."

A First, Nanoscale Phonon Spectrometer

Robinson also credits the CNF as the reason he and his lab were able to develop a nanoscale phonon spectrometer—a first of its kind. The tool measures heat transfer at the nanoscale level at unprecedented resolutions. It does so by emitting and capturing phonons through superconducting tunnel junctions, devices that work only at extremely low temperatures.

In his experiment, the device sends controlled frequencies of phonons through nanosheets, and the transmission is then collected. The phonons scatter off the surface of the nanosheets, and the rate they scatter influences how heat flows through a material. Using 100-nanometer wide silicon nanosheets, the researchers discovered that the five-decades-old theory of phonon scattering, called the Casimir-Ziman theory, is invalid when it comes to nanomaterial heat transfer.

“We could create a new revolution in circuit building,” says Robinson. “People could print new circuits from their home printers.”

“We found that the prediction is way off, about four times off, from what people previously thought,” says Robinson. “The challenge now is to come up with a new theory on how phonons bounce off rough surfaces at the nanoscale, and how that will ultimately affect thermal transport.” A new theory could then lead to other advances, such as the ability to control the heat properties of materials at the nanoscale for use in applications like thermoelectrics.

Robinson’s nanoscale phonon spectrometer research completes the cycle for Robinson, who was attracted to higher education by his fascination with the physics of heat transfer. He says, “now we have the ability to measure phonon transport through nanostructures with a precision that hadn’t previously been available. It should be interesting to see what new phenomena we find.”

A Collaborative Endeavor

Robinson’s lab reflects the interdisciplinary nature of his and the department’s interests, with graduate students and postdoctoral fellows from Physics, Electrical Engineering, Chemistry, Applied Physics, Chemical Engineering, and of course, Materials Science and Engineering.

“It’s my passion to be able to really understand the physics and chemistry of my nanomaterials,” says Robinson. “And I also want to believe that we’re going to make a difference in this world, so I want to be able to create new devices from these nanoscale components.”