CAREER: Integrated Research & Education on Controlling the Size and Composition of Diamond Nanocrystals via Molecular Synthesis

University Of Washington, Seattle WA

Investigators

Abstract

Non-Technical Abstract Diamond nanocrystals are being considered for a range of applications including optical bioimaging, quantum-information-processing, photocatalysis, the optical detection of electric and magnetic fields, spatially localized magnetic resonance imaging, and also for seeding the growth of diamond thin films. In nature diamond nanocrystals are formed through non-equilibrium events including stellar supernovae or the impact of meteors on Earth. More recently, diamond nanocrystals have been synthesized directly within laboratories through the detonation of high explosives (i.e., TNT), pulsed laser irradiation of carbon nanoparticles, or through direct growth within non-equilibrium atmospheric-pressure plasma reactors. Size is a crucial parameter for diamond nanocrystals in that it impacts how quickly these materials are cleared from the body through filtration in the kidneys. Furthermore, composition is critically important for diamond nanocrystals in that it determines the optical and electronic properties. Currently there are no synthetic protocols that enable control over both the 1) size and 2) defect composition of diamond nanocrystals. This research will generate valuable fundamental knowledge for controlling both of these crucial parameters. Additionally, there currently is no known shallow n-type donor in diamond materials. This research will also pursue the experimental demonstration of n-type conductivity within diamond nanocrystals that would be valuable to society at large by enabling beneficial high-frequency, high-power optoelectronic devices for information processing, UV water-purification, and extreme environment coatings. The educational outreach efforts proposed here will build a learning pathway for senior undergraduate students to develop skills with advanced numerical methods through the development of a numerical computing module integrated within the existing engineering curriculum at the University of Washington. These skills will prepare students for careers within the optoelectronic materials industry, or for continuing their education in graduate school. Outreach efforts to Native Alaskan elementary students, undergraduates in the Alaska Native Science & Engineering Program at the University of Alaska, and Indigenous Alliance outreach at UW will help inspire & retain the next generation of underrepresented materials scientists. Technical Abstract Currently there are no options in the scientific literature for rationally synthesizing nanodiamonds with precise 1) sizes and 2) compositions. The intellectual merit of this proposal rests on generating new knowledge for how to use high-pressure/high-temperature diffusion-doping to generate precise 1) sizes and 2) optoelectronic point-defects in nanodiamond. With support from the Solid State and Materials Chemistry program, four primary research milestones will be pursued over 5 years: 1) Test the hypothesis that reducing the grain-size of amorphous-carbon nanoparticles will reduce the thermodynamic conditions necessary to produce nanoscale diamond grains through high-pressure/high-temperature techniques. The chemical-potential for carbon atoms at the surface of amorphous-carbon is size-dependent (stemming from the Gibbs-Thomson effect) which may lower the minimum temperature and pressure of the amorphous-carbon / diamond phase-transition. 2) A predictive numerical model will be employed for photothermal heating of highly-absorbing amorphous-carbon materials in the laser-heated diamond anvil cell based on an analytical eigenfunction expansion solution for the energy partial differential equation using spherical coordinates. 3) Molecular doping strategies will be used to control the concentration of model point-defects using either silicon- or nickel- heteroatoms within the diamond lattice. 4) Prior results for synthesizing doped diamond nanocrystals from amorphous-carbon will inform high-risk / high-reward experimental efforts to observe a theoretically-proposed, polyatomic n-type defect center in diamond. The experimental & theoretical approaches will provide an integrated understanding of how the size and composition of amorphous-carbon grains determine final nanodiamond properties