Pearl Jam’s hit, “The Light Years,” declares “We were but stones, light made us stars.” Bringing light to the transmission electron microscope (TEM) promises to transform our understanding of materials, enabling both direct observation of light-mediated processes and detection of optical emission with atomic scale resolution. To help achieve this goal, my lab is developing capabilities for concurrent optical and electron microscopy within an environmental TEM. This presentation will describe our efforts to visualize a variety of photochemical processes in situ with nanometer-to-atomic scale resolution. We focus in particular on i) observing photocatalytic phase transitions in nanoparticles; ii) detecting quantum light emission from two-dimensional materials; and iii) designing electron-stable fluorescent tags. First, under controlled hydrogen pressures, temperatures, and optical illumination conditions, we study the study the hydrogenation and dehydrogenation of Pd with sub-2-nm spatial resolution and millisecond time resolution. Particles of different sizes, shapes, and crystallinities exhibit distinct thermodynamic and kinetic properties, highlighting several important design principles for next-generation photocatalysts and energy-storage devices. Secondly, we use scanning transmission electron microscopy and cathodoluminescence spectroscopy to investigate color centers in two-dimensional hexagonal boron nitride, a wide bandgap material capable of room-temperature, high-brightness visible quantum emission. We find that sharp, single-photon emission peaks are usually associated with regions of high strain and grain boundaries, facilitating design of next-generation two-dimensional materials and devices. Finally, we describe the design and characterization of nanoparticles that serve as bright emitters within an electron microscope for concurrent optical and electron spectroscopy. In biological specimens, these nanoparticles could enable identification of molecules or proteins with sub-10nm resolution, while simultaneously revealing the ultrastructure of the cell.

Light years: Combined optical and environmental electron microscopy to visualize photonic processes with atomic-scale resolution

2019 Spring National Meeting

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