Browsing by Author "Son, Dong"

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Exciton and its coupling with spin and lattice in strongly quantum confined 0D-2D lead halide perovskite nanocrystals
Chemistry; TAMU; https://hdl.handle.net/20.500.14641/237; National Science Foundation
The Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division supports Professor Dong H. Son and Dr. Alexey Akimov at Texas A&M University to investigate new photophysical properties of lead halide perovskite nanocrystals. Lead halide perovskites are newly emerging semiconductor materials important for various applications in photonics and photocatalysis. Understanding the photophysical properties of lead halide perovskites, particularly those found in nanosized crystal forms, is essential to developing high-performance solar cells and light emitting devices. Professor Son?s research team studies the photophysical properties under a special condition called quantum confinement. This condition of quantum confinement is achieved by making the nanocrystals? size and shape smaller than several nanometers. This condition may bring about new optical and electronic properties useful for building high performance, photonic and photocatalytic devices. New functionalities, not obtainable from the bulk form, can also emerge from the nanocrystal forms of lead halide perovskites as photon and charge emitters. Research in this area has generally been challenging due to the difficulty in realizing controllable quantum confinement in these materials. Professor Son?s team explores effective ways of accessing the useful quantum confinement-induced properties by precisely controlling the size and shape of these nanomaterials. In addition to the scientific activities and impacts, this project contributes to student training on scientific instrumentation and measurements utilizing self-learning hardware kits checked out to students for in-depth learning experience. Professor Son?s team also reaches out to K-12 students and to the local community providing lectures and hands-on science experiments through University-run open-house events and a public lecture series. With this support from the Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division, Professor Son?s research team investigates new photophysical properties of lead halide perovskite nanocrystals via controlled quantum confinement in 0 to 2 dimensions. The anticipated photophysical properties can enable these materials to be developed into a source of photons and charges with enhanced capabilities important for building high-performance photonic and photocatalytic devices. The research team leverages their recent success in preparing highly uniform and strongly quantum confined lead halide perovskite nanocrystals. These materials enhance the coupling between exciton and other degrees of freedom crucial for opening new pathways of photon and charge generation. In this project, Professor Son?s team specifically examines the stable and intense emission from very long-lived dark excitons of the strongly confined perovskite nanocrystals at low temperatures. The team also investigates enhanced sensitization in Mn-doped lead halide perovskite nanoplatelets benefitting from the giant oscillator strength exciton transition and efficient energy transfer of long-lived dark exciton to Mn. In addition, processes such as enhanced hot electron generation and hot electron photoemission in Mn-doped perovskite quantum dots via exciton-to-hot electron upconversion are elucidated. 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.
Exciton and its coupling with spin and lattice in strongly quantum confined 0D-2D lead halide perovskite nanocrystals
Chemistry; TAMU; https://hdl.handle.net/20.500.14641/237; National Science Foundation
The Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division supports Professor Dong H. Son and Dr. Alexey Akimov at Texas A&M University to investigate new photophysical properties of lead halide perovskite nanocrystals. Lead halide perovskites are newly emerging semiconductor materials important for various applications in photonics and photocatalysis. Understanding the photophysical properties of lead halide perovskites, particularly those found in nanosized crystal forms, is essential to developing high-performance solar cells and light emitting devices. Professor Son?s research team studies the photophysical properties under a special condition called quantum confinement. This condition of quantum confinement is achieved by making the nanocrystals? size and shape smaller than several nanometers. This condition may bring about new optical and electronic properties useful for building high performance, photonic and photocatalytic devices. New functionalities, not obtainable from the bulk form, can also emerge from the nanocrystal forms of lead halide perovskites as photon and charge emitters. Research in this area has generally been challenging due to the difficulty in realizing controllable quantum confinement in these materials. Professor Son?s team explores effective ways of accessing the useful quantum confinement-induced properties by precisely controlling the size and shape of these nanomaterials. In addition to the scientific activities and impacts, this project contributes to student training on scientific instrumentation and measurements utilizing self-learning hardware kits checked out to students for in-depth learning experience. Professor Son?s team also reaches out to K-12 students and to the local community providing lectures and hands-on science experiments through University-run open-house events and a public lecture series. With this support from the Macromolecular, Supramolecular, and Nanochemistry Program in the Chemistry Division, Professor Son?s research team investigates new photophysical properties of lead halide perovskite nanocrystals via controlled quantum confinement in 0 to 2 dimensions. The anticipated photophysical properties can enable these materials to be developed into a source of photons and charges with enhanced capabilities important for building high-performance photonic and photocatalytic devices. The research team leverages their recent success in preparing highly uniform and strongly quantum confined lead halide perovskite nanocrystals. These materials enhance the coupling between exciton and other degrees of freedom crucial for opening new pathways of photon and charge generation. In this project, Professor Son?s team specifically examines the stable and intense emission from very long-lived dark excitons of the strongly confined perovskite nanocrystals at low temperatures. The team also investigates enhanced sensitization in Mn-doped lead halide perovskite nanoplatelets benefitting from the giant oscillator strength exciton transition and efficient energy transfer of long-lived dark exciton to Mn. In addition, processes such as enhanced hot electron generation and hot electron photoemission in Mn-doped perovskite quantum dots via exciton-to-hot electron upconversion are elucidated. 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.
Hybrid Catalyst System Combining Hot Electron-Generating Quantum Dots and Molecular Catalyst for Efficient Photocatalytic CO2 Reduction
Chemistry; TAMU; https://hdl.handle.net/20.500.14641/237; National Science Foundation
Photocatalysis utilizes energy from the sun to achieve a sustainable route to producing high-value fuels and chemicals from low-value or environmentally harmful molecules. In this project, new combinations of photocatalysts will be investigated to upgrade carbon dioxide (CO2) to molecules that can be used to make fuels or chemicals. The new catalytic materials will help pave a path to the Nation's future energy security while decreasing the environmental impact of carbon emissions. The project also includes plans for education and outreach at all levels, ranging from training graduate and undergraduate students in energy-related technologies to promoting interest in STEM-related areas amongst K-12 students. The novelty of the proposed hybrid systems lies in the combination of specifically doped quantum dot (QD) photosensitizers with molecular, transition metal-based catalysts. The ability of doped QDs to generate hot electrons upon irradiation will allow for long-range hot electron photosensitization and efficient electron transfer to molecular CO2 reduction catalysts without the need for direct linkage between the sensitizer and catalyst. In the new hybrid systems, manganese and copper dual-doped quantum dots will produce energetic hot electrons under weak visible light, which will perform efficient long-range (e.g., 10 nm) sensitization to molecular catalysts in solution. The large increase of the sensitization volume and energetically more favorable and unidirectional hot electron transfer to the molecular catalyst are expected to enhance the overall catalytic CO2 reduction efficiency of the hybrid catalyst system, while keeping the convenience and flexibility of uncoupled hybrid catalyst system in construction and regeneration. To quantify the rates of key processes at each stage of the entire photocatalytic reduction process and to optimize their efficiency through structural variations of the sensitizer and hybrid system, several objectives will be pursued: (1) structural control of the doped quantum dot sensitizer for maximum hot electron generation efficiency, (2) quantitative measurements of hot electron sensitization efficiency to molecular rhenium- and nickel-based molecular catalysts, and (3) assessment of the overall catalytic efficiency in the reactor at varying reaction conditions. Comparative evaluation of the overall efficiency of the hybrid catalysts designed here with that of the existing hybrid architectures will lead to the identification of the optimum structure of the hot electron-sensitized hybrid catalyst system. With respect to education, new multimedia materials will be used to complement instrumental training in undergraduate laboratories and graduate classes and in workshops on instrumentation/data acquisition/processing. Outreach will involve new hands-on experiments that are related to the synthesis of plasmonic nanocrystals and simple optical experiments that can be safely performed by middle or high school classes as a part of their science curriculum. Additionally, the Texas-wide Texas Sized Crystal Contest is being organized which will allow large numbers of high school students and teachers to experience the fascinating world of crystalline solids. 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
QLC:EAGER: Precisely Configurable 2-Dimensional Array of Colloidal Perovskite Quantum Dots as a New Platform for Chemical Qubits
Chemistry; TAMU; https://hdl.handle.net/20.500.14641/237; National Science Foundation
Quantum computation is a new paradigm that can solve highly complex problems that are difficult to tackle with current computing technology. To realize a practical quantum computer, an important prerequisite is the construction of the basic hardware units for performing quantum computation, called qubits. The qubit is analogous to the bit found in modern digital computers. However, unlike a bit, which can be in one of two different states, qubits can exist in many different states. One of the challenges in quantum computation is the construction of the qubits in large scale and in a robust manner for practical and low-cost implementation of quantum computation. With support from the Macromolecular, Supramolecular, and Nanochemistry program in the Division of Chemistry, Professors Dong Son and Alexey Akimov at Texas A&M University are developing a new qubit platform based on chemically synthesized quantum dots that can be mass-produced with extremely high uniformity and assembled in a precisely controlled manner. While the fabrication and positioning of the QDs on the nanometer scale is very risky, the research may have broad implications for the development of quantum computers and quantum information systems. The project also provides training opportunities for students, in an interdisciplinary environment that combines chemistry and quantum optics. Working alongside with their students, Professors Son and Akimov are developing templating strategies to fabricate qubit structures based on finite-sized arrays of perovskite quantum dots, with each structure being replicated many times in large scale. The approach takes advantage of recent progress in chemical synthesis of structurally identical quantum dots used as the building blocks of the qubits. Understanding and controlling the behavior of the quantum mechanically coupled excitons and spins of the magnetic impurities doped in the quantum dot arrays is particularly important to verify the functionality of the new structures. For this purpose, photoluminescence optical microscopy methods are used to characterize the qubit structures and to confirm the quantum mechanical behavior needed for the scaled-up qubit platform to function as a robust quantum computer. These are necessary steps to take towards the application of quantum computation to solve real-world problems. The team, composed of a chemist and a physicist, is also actively developing the interdisciplinary and outreach programs that utilize the new frontiers of modern science to educate the next-generation scientists. 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.