Researchers from the Department of Chemistry at Carnegie Mellon University have found a way to control the life span of quantum states of gold nanotechnology for three orders, which can lead to the improvement of solar cell technologies and photocatalysis. Their study was published in April 18 issue of the Science.
Excited quantum states occur when the light is absorbed by particles and the energy of that light is temporarily stored within the particle, making its energy higher than its ground state. Energy is rapidly decaying and can be lost as heat in a nanosecond range, or one billionth of a second. Expanding this quantum state can allow researchers more time and opportunity to use the stored energy.
Carnegie Mellon Chemistry Professor Rongchao Jin is known for developing precisely sized nanoparticles of gold. In this continuation of his work, post-doctoral researcher Meng Zhou and PhD. student Tatsuya Higaki, who is co-first author on paper, studied atomic precision gold nanoclasses containing between 30 and 38 atoms. They have changed cluster structures by rearranging atoms into exotic configurations and protecting them with a limited ligand.
The researchers measure the quantum levels of nanoclusters using femtosecond and nanoseconded temporal resonant spectroscopy to take images of nanoclastic at a time when they absorbed light energy, in this case femtosecondary laser pulse, until they release energy. Collaborators at the University of California, Riverside confirmed the results using calculations of density function theory to analyze molecular orbitals of nanoclasses.
They found that a 30 nanocluster of hexagonal narrow structures (hcp) had a quantum life span of one nanosecond. But a nanoclaster of 38 atoms, with a cubic house (central house) with a housing, had a much longer life expectancy of 4.7 microseconds. Expanding the life span of three large sizes gives enough time for researchers to extract absorbed light from the nanoclass – a discovery that has significant implications.
"The strategy of manipulating the exciting life from a very short to very long period is exciting. The extremely long quantum life span of 4.7 microseconds is comparable to that of silicon used for commercial solar cells," said Jin. "It should give us enough time to efficiently extract the energy in external circuits as an electronic current without losing too much energy to heat up."
The adjusted quantum life span can also be used to increase the efficiency of photocatalysts with visible light that is used to convert solar energy into chemicals, such as converting methanol and carbon dioxide ethanol.
This research was funded by the National Science Foundation (1808675); Office of the Air Force for Scientific Research; and the US Department of Energy (US DOE), the Office of Science, the Office of Basic Energy Sciences and Chemical Sciences, the Department of Earth Sciences and Biology. The work used the resources of the Center for Functional Nanomaterials, an American DOE Science Fund Office at the Brookhaven National Laboratory.
Materials provided by Carnegie Mellon University. Original written by Dzozlin Duffy. Note: The content can be edited for style and length.