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BariumPreprintChemrxiv.pdf (6.06 MB)

Barium Selective Chemosensing by Diazacrown Ether Naphthalimide Turn-on Fluorophores for Single Ion Barium Tagging

submitted on 14.06.2020 and posted on 17.06.2020 by pawan thapa, Nick Byrnes, Alena Denisenko, Frank Foss, Ben Jones, James X. Mao, Austin McDonald, Kwangho Nam, Charleston Newhouse, David Nygren, Thanh Thuy Vuong, Katherine Woodruff
Single molecule fluorescence detection of barium is investigated for enhancing the sensitivity and robustness of a neutrinoless double beta decay ($0\nu\beta\beta$) search in $^{136}$Xe, the discovery of which would alter our understanding of the nature of neutrinos and the early history of the Universe. A key developmental step is the synthesis of barium-selective chemosensors capable of incorporation into ongoing experiments in high-pressure $^{136}$Xe gas. Here we report turn-on fluorescent naphthalimide chemosensors containing monoaza- and diaza-crown ethers as agents for single Ba$^{2+}$ detection. Monoaza-18-crown-6 ether naphthalimide sensors showed sensitivity primarily to Ba$^{2+}$ and Hg$^{2+}$, whereas two diaza-18-crown-6 ether naphthalimides revealed a desirable selectivity toward Ba$^{2+}$. Solution-phase fluorescence and NMR experiments support a photoinduced electron transfer mechanism enabling turn-on fluorescence sensing in the presence of barium ions. Changes in ion-receptor interactions enable effective selectivity between competitive barium, mercury, and potassium ions, with detailed calculations correctly predicting fluorescence responses. With these molecules, dry-phase single Ba$^{2+}$ ion imaging with turn-on fluorescence is realized using oil-free microscopy techniques. This represents a significant advance toward a practical method of single Ba$^{2+}$ detection within large volumes of $^{136}$Xe, plausibly enabling a background-free technique to search for the hypothetical process of $0\nu\beta\beta$.


Department of Energy DE-SC0019054

Department of Energy DE-SC0019223


Email Address of Submitting Author


University of Texas at Arlington


United States of America

ORCID For Submitting Author


Declaration of Conflict of Interest

No conflict of interest


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