Home > Press > 'Upconverted' light has a bright future: Rice University professor developing plasmon-powered devices for medicine, security, solar cells
A Rice University professor has introduced a new method that takes advantage of plasmonic metals' production of hot carriers to boost light to a higher frequency. An electron microscope image at bottom shows gold-capped quantum wells, each about 100 nanometers wide. (Credit: Gururaj Naik/Rice University) |
Abstract:
A Rice University professor's method to "upconvert" light could make solar cells more efficient and disease-targeting nanoparticles more effective.
Experiments led by Gururaj Naik, an assistant professor of electrical and computer engineering, combined plasmonic metals and semiconducting quantum wells to boost the frequency of light, changing its color.
In a nanoscale prototype Naik developed as a postdoctoral researcher at Stanford University, custom-designed pylons that were struck by green light produced a higher-energy blue glow. "I'm taking low-energy photons and converting them to high-energy photons," he said.
Efficient upconversion of light could let solar cells turn otherwise-wasted infrared sunlight into electricity or help light-activated nanoparticles treat diseased cells, Naik said.
The work appears in the American Chemical Society's Nano Letters.
The magic happens inside tiny pylons that measure about 100 nanometers across. When excited by a specific wavelength of light, specks of gold on the tips of the pylons convert the light energy into plasmons, waves of energy that slosh rhythmically across the gold surface like ripples on a pond. Plasmons are short-lived, and when they decay, they give up their energy in one of two ways; they either emit a photon of light or produce heat by transferring their energy to a single electron -- a "hot" electron.
Naik's work at Stanford was inspired by the groundbreaking work of professors Naomi Halas and Peter Nordlander at Rice's Laboratory for Nanophotonics, who had shown that exciting plasmonic materials also excited "hot carriers" – electrons and holes – within. (Electron holes are the vacancies created when an electron is excited into a higher state, giving its atom a positive charge.)
"Plasmonics is really great at squeezing light on the nanoscale," said Naik, who joined Rice's faculty a year ago. "But that always comes at the cost of something. Halas and Nordlander showed you can extract the optical losses in the form of electricity. My idea was to put them back to optical form."
He designed pylons using alternate layers of gallium nitride and indium gallium nitride that were topped with a thin layer of gold and surrounded by silver. Instead of letting the hot carriers slip away, Naik's strategy was to direct both hot electrons and hot holes toward the gallium nitride and indium gallium nitride bases that serve as electron-trapping quantum wells. These wells have an inherent bandgap that sequesters electrons and holes until they recombine at sufficient energy to leap the gap and release photons at a higher frequency.
Present-day upconverters used in on-chip communications, photodynamic therapy, security and data storage have efficiencies in the range of 5 to 10 percent, Naik said. Quantum theory offers a maximum 50 percent efficiency ("because we're absorbing two photons to emit one") but, he said, 25 percent is a practical goal for his method.
Naik noted his devices can be tuned by changing the size and shape of the particles and thickness of the layers. "Upconverters based on lanthanides and organic molecules emit and absorb light at set frequencies because they're fixed by atomic or molecular energy levels," he said. "We can design quantum wells and tune their bandgaps to emit photons in the frequency range we want and similarly design metal nanostructures to absorb at different frequencies. That means we can design absorption and emission almost independently, which was not possible before."
Naik built and tested a proof-of-concept prototype of the pylon array while working in the Stanford lab of Jennifer Dionne after co-authoring a theoretical paper with her that set the stage for the experiments.
"That's a solid-state device," Naik said of the prototype. "The next step is to make standalone particles by coating quantum dots with metal at just the right size and shape."
These show promise as medical contrast agents or drug-delivery vehicles, he said. "Infrared light penetrates deeper into tissues, and blue light can cause the reactions necessary for the delivery of medicine," Naik said. "People use upconverters with drugs, deliver them to the desired part of the body, and shine infrared light from the outside to deliver and activate the drug."
The particles would also make a mean invisible ink, he said. "You can write with an upconverter and nobody would know until you shine high-intensity infrared on it and it upconverts to visible light."
Co-authors of the paper are Alex Welch, Justin Briggs and Michelle Solomon, all of Stanford. Dionne is an associate professor of materials science and engineering at Stanford.
The Department of Energy Office of Basic Energy Sciences and the Department of Defense supported the research.
####
About Rice University
Located on a 300-acre forested campus in Houston, Rice University is consistently ranked among the nation’s top 20 universities by U.S. News & World Report. Rice has highly respected schools of Architecture, Business, Continuing Studies, Engineering, Humanities, Music, Natural Sciences and Social Sciences and is home to the Baker Institute for Public Policy. With 3,879 undergraduates and 2,861 graduate students, Rice’s undergraduate student-to-faculty ratio is 6-to-1. Its residential college system builds close-knit communities and lifelong friendships, just one reason why Rice is ranked No. 1 for happiest students and for lots of race/class interaction by the Princeton Review. Rice is also rated as a best value among private universities by Kiplinger’s Personal Finance. To read “What they’re saying about Rice,” go to http://tinyurl.com/RiceUniversityoverview .
Follow Rice News and Media Relations via Twitter @RiceUNews
For more information, please click here
Contacts:
David Ruth
713-348-6327
Mike Williams
713-348-6728
Copyright © Rice University
If you have a comment, please Contact us.Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Related Links |
Read the theoretical paper by Naik and Dionne on photon upconversion at:
Rice Department of Electrical and Computer Engineering:
Related News Press |
News and information
Simulating magnetization in a Heisenberg quantum spin chain April 5th, 2024
NRL charters Navy’s quantum inertial navigation path to reduce drift April 5th, 2024
Discovery points path to flash-like memory for storing qubits: Rice find could hasten development of nonvolatile quantum memory April 5th, 2024
Good as gold - improving infectious disease testing with gold nanoparticles April 5th, 2024
Cancer
New micromaterial releases nanoparticles that selectively destroy cancer cells April 5th, 2024
Super-efficient laser light-induced detection of cancer cell-derived nanoparticles: Skipping ultracentrifugation, detection time reduced from hours to minutes! October 6th, 2023
Govt.-Legislation/Regulation/Funding/Policy
NRL charters Navy’s quantum inertial navigation path to reduce drift April 5th, 2024
Discovery points path to flash-like memory for storing qubits: Rice find could hasten development of nonvolatile quantum memory April 5th, 2024
Chemical reactions can scramble quantum information as well as black holes April 5th, 2024
Possible Futures
Discovery points path to flash-like memory for storing qubits: Rice find could hasten development of nonvolatile quantum memory April 5th, 2024
With VECSELs towards the quantum internet Fraunhofer: IAF achieves record output power with VECSEL for quantum frequency converters April 5th, 2024
Nanomedicine
New micromaterial releases nanoparticles that selectively destroy cancer cells April 5th, 2024
Good as gold - improving infectious disease testing with gold nanoparticles April 5th, 2024
Researchers develop artificial building blocks of life March 8th, 2024
Discoveries
Chemical reactions can scramble quantum information as well as black holes April 5th, 2024
New micromaterial releases nanoparticles that selectively destroy cancer cells April 5th, 2024
Utilizing palladium for addressing contact issues of buried oxide thin film transistors April 5th, 2024
Announcements
NRL charters Navy’s quantum inertial navigation path to reduce drift April 5th, 2024
Discovery points path to flash-like memory for storing qubits: Rice find could hasten development of nonvolatile quantum memory April 5th, 2024
Interviews/Book Reviews/Essays/Reports/Podcasts/Journals/White papers/Posters
Simulating magnetization in a Heisenberg quantum spin chain April 5th, 2024
Discovery points path to flash-like memory for storing qubits: Rice find could hasten development of nonvolatile quantum memory April 5th, 2024
Military
NRL charters Navy’s quantum inertial navigation path to reduce drift April 5th, 2024
What heat can tell us about battery chemistry: using the Peltier effect to study lithium-ion cells March 8th, 2024
New chip opens door to AI computing at light speed February 16th, 2024
Energy
Development of zinc oxide nanopagoda array photoelectrode: photoelectrochemical water-splitting hydrogen production January 12th, 2024
Shedding light on unique conduction mechanisms in a new type of perovskite oxide November 17th, 2023
Inverted perovskite solar cell breaks 25% efficiency record: Researchers improve cell efficiency using a combination of molecules to address different November 17th, 2023
The efficient perovskite cells with a structured anti-reflective layer – another step towards commercialization on a wider scale October 6th, 2023
Photonics/Optics/Lasers
With VECSELs towards the quantum internet Fraunhofer: IAF achieves record output power with VECSEL for quantum frequency converters April 5th, 2024
Nanoscale CL thermometry with lanthanide-doped heavy-metal oxide in TEM March 8th, 2024
Optically trapped quantum droplets of light can bind together to form macroscopic complexes March 8th, 2024
HKUST researchers develop new integration technique for efficient coupling of III-V and silicon February 16th, 2024
Solar/Photovoltaic
Development of zinc oxide nanopagoda array photoelectrode: photoelectrochemical water-splitting hydrogen production January 12th, 2024
Shedding light on unique conduction mechanisms in a new type of perovskite oxide November 17th, 2023
Inverted perovskite solar cell breaks 25% efficiency record: Researchers improve cell efficiency using a combination of molecules to address different November 17th, 2023
Charged “molecular beasts” the basis for new compounds: Researchers at Leipzig University use “aggressive” fragments of molecular ions for chemical synthesis November 3rd, 2023
The latest news from around the world, FREE | ||
Premium Products | ||
Only the news you want to read!
Learn More |
||
Full-service, expert consulting
Learn More |
||