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PHYS 8990 Topic

Rare-earth-activated one-dimensional luminescent nanostructures for nano-photonics and solid-state lighting

Zhengwei Pan

One-dimensional (1-D) nanostructures (e.g., nanowires and nanobelts) have been attracting great attention in the past decade due to their novel optical and electrical properties and their potential device applications. Previous work on 1-D nanostructures was mainly focused on elemental and binary systems because of the difficulties in synthesis of multicomponent (ternary and quaternary) nanowires. The incorporation of additional components such as rare-earth ions into 1-D nanostructures will allow for creation of novel classes of functional nanomaterials. We have recently developed a unique, thermal evaporation-based synthetic technique to incorporate europium ion (Eu2+) into aluminates to form multicomponent luminescent nanobelts and whiskers. So far, we have fabricated three series with a total of ten kinds of Eu2+-activated aluminates: three ternary europium aluminates (Eu-Al-O, EAO), three quaternary strontium europium aluminates (Sr-Eu-Al-O, SEAO), and four quaternary barium europium aluminates (Ba-Eu-Al-O, BEAO). Detailed characterizations showed that most of these Eu2+-activated ternary and quaternary luminescent nanobelts exhibit new compositions, new crystal lattice parameters, and new luminescence properties and mechanisms that have not been previously observed.

The Eu2+-activated aluminates nanobelts show novel optical properties and performances. They can be effectively excited by a wide range of excitation sources (blue light, UV, deep UV, x-ray and e-beam) and emit intense, characteristic blue, green, orange (yellow), and/or red luminescence of Eu2+ ions. These luminescent nanobelts can function as a light generator and waveguide, making them ideal building blocks for nanoscale photonic circuitry. Significantly, the yellow BEAO phosphors can be efficiently excited by blue LED and the thus generated yellow light mixes with part of the blue light giving bright warm-white light, which is very promising for the fabrication of warm-white LEDs for general in-door illumination.

In this project, students will have an opportunity to learn the growth of luminescent nanomaterials using our unique synthesis techniques, to discover new and novel luminescent materials, to characterize materials using the state-of-the-art scanning electron microscope, transmission electron microscope, spectrofluorometer, X-ray diffraction, synchrotron scattering and Laue micro-diffraction, to investigate the underlying luminescent mechanisms, and to fabricate nano-photonic devices and warm-white LED devices. The students will also have the opportunity to work with scientists in the national laboratories (Oak Ridge National Laboratory and Argonne National Laboratory) for materials characterization. 

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