All Publications

  • Photoabsorption Imaging at Nanometer Scales Using Secondary Electron Analysis. Nano letters Zhang, Z., Martis, J., Xu, X., Li, H., Xie, C., Takasuka, B., Lee, J., Roy, A. K., Majumdar, A. 2021


    Optical imaging with nanometer resolution offers fundamental insights into light-matter interactions. Traditional optical techniques are diffraction limited with a spatial resolution >100 nm. Optical super-resolution and cathodoluminescence techniques have higher spatial resolutions, but these approaches require the sample to fluoresce, which many materials lack. Here, we introduce photoabsorption microscopy using electron analysis, which involves spectrally specific photoabsorption that is locally probed using a scanning electron microscope, whereby a photoabsorption-induced surface photovoltage modulates the secondary electron emission. We demonstrate spectrally specific photoabsorption imaging with sub-20 nm spatial resolution using silicon, germanium, and gold nanoparticles. Theoretical analysis and Monte Carlo simulations are used to explain the basic trends of the photoabsorption-induced secondary electron signal. Based on our current experiments and this analysis, we expect that the spatial resolution can be further improved to a few nanometers, thereby offering a general approach for nanometer-scale optical spectroscopic imaging and material characterization.

    View details for DOI 10.1021/acs.nanolett.0c03993

    View details for PubMedID 33635654

  • A safe and non-flammable sodium metal battery based on an ionic liquid electrolyte. Nature communications Sun, H., Zhu, G., Xu, X., Liao, M., Li, Y., Angell, M., Gu, M., Zhu, Y., Hung, W. H., Li, J., Kuang, Y., Meng, Y., Lin, M., Peng, H., Dai, H. 2019; 10 (1): 3302


    Rechargeable sodium metal batteries with high energy density could be important to a wide range of energy applications in modern society. The pursuit of higher energy density should ideally come with high safety, a goal difficult for electrolytes based on organic solvents. Here we report a chloroaluminate ionic liquid electrolyte comprised of aluminium chloride/1-methyl-3-ethylimidazolium chloride/sodium chloride ionic liquid spiked with two important additives, ethylaluminum dichloride and 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide. This leads to the first chloroaluminate based ionic liquid electrolyte for rechargeable sodium metal battery. The obtained batteries reached voltages up to ~4V, high Coulombic efficiency up to 99.9%, and high energy and power density of ~420Whkg-1 and ~1766 W kg-1, respectively. The batteries retained over 90% of the original capacity after 700 cycles, suggesting an effective approach to sodium metal batteries with high energy/high power density, long cycle life and high safety.

    View details for DOI 10.1038/s41467-019-11102-2

    View details for PubMedID 31341162