Plasmon-induced Triplet Energy Transfer (PITET) for Photon Upconversion

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With this award, the Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division is supporting Dr. Ming Lee Tang at the University of California Riverside (UCR) to study the energy transfer process of plasmonic systems. Plasmonics refers to light-induced oscillation of loosely bound electrons in metals. This research is important for catalysis, imaging, and energy conversion applications. Minuscule metal particles with dimensions on the order of nanometers have been treasured historically for their beauty in stained glass windows. The vivid colors in stained glass arise from the strong absorption and scattering of light due to plasmons supported by the metal nanoparticles. Dr. Tang’s team is conducting fundamental research that addresses that seeks to efficiently transfer the energy stored as plasmons in metal nanoparticles to neighboring chemical molecules. The research aims to provide mechanisms to prevent the system from unwanted energy loss through rapid scattering of light or dissipation of energy as heat. Such advances are essential for the development of metal nanoparticles for intended applications in photocatalysis and in solar cells. The team designs and synthesizes various nanomaterial architectures. Plasmons tightly confined within the nanoscale metal architectures are then characterized to tune the system to perform useful work upon light activation. This research also has broader impacts of engaging the general public in the Inland Empire program in Southern California. This outreach program includes interactive demonstrations and science activities at local elementary schools and pre-schools that are led by undergraduate and graduate students.Dr. Ming Lee Tang’s team at UCR is investigating plasmon-induced triplet energy transfer. The goal is to use light captured by metal nano-antennas for photon upconversion, a process of converting low energy photons from incoherent sources such as the sun to useful high energy photons. Novel light-absorbing nanostructures based on noble metals in this research can absorb near-infrared photons to produce violet photon emissions from neighboring anthracene- and perylene-based chromophores. Specifically, silver nanoprisms and gold nanorods with their localized surface plasmon resonance tuned between 1.5 and 1.8 eV are expected to be resonant with the lowest excited triplet states of the chromophores, so as to photosensitize the molecular triplet states across an oxide barrier. Steady-state photon upconversion measurements will be used to quantify the efficiency of plasmon-induced triplet energy transfer. Time resolved photoluminescence and transient absorption measurements provide independent measurements of the yield and rate of the triplet energy transfer.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.