Collaborative Research: From Synthesis, Local and Electronic Structures, to Optical and Scintillating Properties of Lanthanoid Hafnate Nanoparticles

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Many chemical substances have the property of emitting radiation, called luminescence, which is useful in light-emitting applications. Lanthanide luminescence plays a vital role in our daily life due to the unique optical properties of these ions with respect to light generation and amplification. Extending from laser physics, other familiar applications in our regular life include lighting, displays, optical telecommunications, night vision, security inks, counterfeiting tags, luminescent coatings, medical imaging, medical diagnostics, and airport security checks. New and more effective luminescent materials are desirable from both a technological and an economic necessity in order to make cheap, widely available, and long-lasting light emitting, or photonic, devices. Dr. Yuanbing Mao of the University of Texas Rio Grande Valley and Dr. James Dorman of Louisiana State University are making metal oxide nanoparticles with increased luminescence by developing new preparation methods. Using various techniques and in collaboration with scientists at Oak Ridge National Laboratory, the research team is figuring out how their reliable synthesis methods make these nanoparticles ultra-small and uniformly shaped and sized, at more than 1000 times smaller than the diameter of a human hair. The team also studies the relationship between the size, shape, structure, composition, and luminescence performance of these nanoparticles. The fundamental understanding gained in this project helps the future design of new luminescent nanomaterials, photonic devices, and nanoparticle synthesis methods. Dr. Mao's and Dr. Dormans's research is attractive to students at many levels, emphasizing the involvement of underrepresented students as research assistants. The research team has introduced a university-wide seminar series and several new course modules. Through these activities, Drs. Mao and. Dorman directly raise awareness and advocacy for nanoscience and optoelectronic materials among varied demographic groups as a way to improve the community, the national economy, and the environment. The partnership focuses on building a strong pipeline for underrepresented students and enabling fruitful student-faculty exchange programs between the two universities.In this research program, Dr. Yuanbing Mao of the University of Texas Rio Grande Valley (UTRGV) and Dr. James Dorman of Louisiana State University (LSU) are supported by the Macromolecular, Supramolecular and Nanochemistry (MSN) Program to develop a reliable synthetic process, understandthe growth mechanism, investigate the size effects, and correlate the crystal, local and electronic structures with the optical and scintillating properties of these lanthanoid hafnate nanophosphors. Ex situ and in situ techniques are used to elucidate the synthetic parameters which determine the particle size and structural parameters for these Ln2Hf2O7 nanoparticles. Based on the obtained results, growth mechanisms of these nanoparticles are developed for directed design of luminescent nanoparticles based on application specifications. Next, the relationship between the crystal, local, and electronic structures of these nanoparticles and their luminescent properties is probed via complementary techniques, such as Raman spectroscopy, synchrotron X-ray and neutron diffractions, X-ray absorption, emission and photoelectron spectroscopies, photoluminescence, and radioluminescence. In addition, this study provides general guidance for proper selection of Ln2Hf2O7 compounds for suitable applications in a wide variety of devices, such as solid electrolytes in high temperature solid oxide fuel cells, thermal barrier coatings, and nuclear waste storage. Dr. Mao involves high school, undergraduate, and graduate students, with an emphasis on underrepresented students, in his research, and has introduced a university-wide seminar series and new course modules which highlight the topics of his team?'research. He and Dr. James Dorman of the Louisiana State University (LSU) communicate science to students at all age levels, directly raising awareness and advocacy for nanoscience and optoelectronic materials among varied demographic groups as a way to improve the community, the national economy, and the environment. The activities also build a strong pipeline for underrepresented students and enable fruitful student-faculty exchange programs between UTRGV and LSU.