Scientists from five Rice University research groups, including four from Rice’s Laboratory for Nanophotonics (LANP), are embarking on new nanotechnology research programs related to green chemistry, energy sustainability and computer security, thanks to two new multimillion-dollar grants from the Department of Defense’s Multidisciplinary University Research Initiative (MURI).
Naomi Halas, director of LANP, is the principal investigator on a five-year, $7.5 million MURI from the Air Force Office of Scientific Research that aims to shed light on plasmon-based photochemical and photophysical processes. The project includes funding for Rice co-principal investigators Peter Nordlander, Stephan Link and Junrong Zheng and is the fourth MURI award for LANP since 1999.
Farinaz Koushanfar, associate professor of electrical and computer engineering and director of Rice’s Adaptive Computing and Embedded Systems (ACES) Laboratory, is co-PI on another MURI from the Air Force that will analyze and upgrade security protections for nanoscale computer hardware. The project will provide more than $1 million for Rice research over the next five years.
The MURI program supports research conducted by teams of investigators that intersect more than one traditional science and engineering discipline. More than 360 teams applied for the 24 new MURIs awarded by the Pentagon last month.
Halas, the Stanley C. Moore Professor in Electrical and Computer Engineering and a professor of biomedical engineering, chemistry, physics and astronomy at Rice, said LANP’s new MURI will follow up on two breakthrough discoveries.
“Within the past 18 months, we have found that plasmonic nanoparticles can be used two distinct ways — to induce chemical reactions through a process called photocatalysis and to convert sunlight directly into steam with extraordinary efficiency,” Halas said. “The Air Force has asked us to explore the underlying physics of each of these processes so we can better understand how to use them for specific applications.”
Plasmons are waves of electronic energy that slosh back and forth across the surface of tiny metallic nanoparticles. Plasmons are created when light strikes the nanoparticle, but only a specific wavelength of light will induce a plasmonic wave, and the plasmon-inducing wavelength varies for each particle, depending upon its shape, size and chemical composition. LANP nanoscientists specialize in creating plasmonic nanoparticles that are tuned to interact with particular wavelengths of light.
In their work on solar steam, LANP scientists have created nanoparticles that convert a wide spectrum of sunlight into heat that efficiently vaporizes water. The resulting energy-rich steam can be used for water remediation, sterilization, distillation, electric power generation and other applications.
In their photocatalysis research, LANP researchers showed that their light-harvesting nanoparticles can catalyze chemical reactions. The finding is important because a majority of commercial chemical processes use catalysts — materials whose very presence spurs useful chemical reactions that would otherwise occur very slowly or not at all.
In May 2011, Halas, Nordlander and LANP colleagues showed they could couple light-harvesting nanoparticles to semiconductors in a way that plasmonic energy could be transferred from the metal to the semiconductor. Working in collaboration with MURI co-PI Emily Carter of Princeton University, they showed in late 2012 that this electronic process could be used to drive a catalytic process that broke strong chemical bonds.
“If you can break bonds, you can induce chemical reactions,” said Nordlander, professor of physics and astronomy. “So that discovery showed the world that this is a process that can be generally exploited. Potentially, there are many uses, but we need to better understand the underlying physics and the chemistry. For example, we don’t know the ideal size for the particles and the best way to optimize them with respect to the substrate.”
Nordlander said Link, associate professor of chemistry and of electrical and computer engineering, and Zheng, assistant professor of chemistry, will work on both the photocatalysis and photothermal MURI research tracks. Link’s group will examine the charge and energy transfer that take place between plasmons and molecules, and Zheng’s group will use spectroscopy to measure the processes in real time.
Additional co-PIs include Princeton’s Carter; Louis Brus, Columbia University; Renee Frontiera, University of Minnesota; and Christoph Lienau, University of Oldenburg, Germany.
“This is a complex problem, and we’ve assembled a ‘dream team’ to study it,” Halas said. “The PIs have all worked together before in smaller groups, but this will be the first time that all of us come together to address a common problem. It’s exciting, because each principle investigator brings something unique to the team.”
Koushanfar is one of 10 investigators on a new MURI based at the University of Connecticut (UConn) that also includes co-PIs from the University of Maryland. The team hopes to develop a universal security theory for next-generation nanoscale computing devices that are based on technologies like memristors, nanowires and graphene.
The research has three aims: to predict the security properties and vulnerabilities of upcoming computer hardware, to evaluate how existing hardware security approaches might be incorporated into next-generation hardware and to create design methodologies that incorporate hardware security in the design phase.
“Security has mostly been an afterthought for building computing devices,” Koushanfar said. “In conventional integrated circuit technology, once a design is realized and deployed, integrating security is difficult. We are truly excited to have the opportunity to investigate the security properties and vulnerabilities of next-generation nanodevices. We believe this work will lead to a paradigm shift incorporating security fully into the design and development of future generations of nanoscale computing hardware.”
She said each researcher working on the MURI has unique capabilities in security analysis, nanoelectronics, counterfeit device detection, cryptography and cyberattack countermeasures.
Koushanfar’s ACES Lab will focus on the development of innovative nanoscale low-power, high-performance processors and advanced security features like “unclonable” functionality and next-generation random-number generators. Rice researchers will also conduct security system analysis and explore cyberattack countermeasures.
The Department of Defense’s MURI program began 25 years ago and has spurred advances in precision navigation and targeting, atomic and molecular self-assembly projects and the computing field known as spintronics.