Cooperation of Three Chromophores Generates the Water-Resistant Nitrate Nonlinear Optical Material Bi3TeO6OH(NO3)2.

Nitrates have long been ignored for practical uses as nonlinear optical (NLO) materials because they are usually very easy to dissolve in water; despite this, the π-conjugated [NO₃]⁻ is among the most desirable NLO-active structural units. The cooperation of three structural chromophores, namely, Bi₃O₆OH short chains with 6s² lone pair electrons, distorted TeO₆ octahedra with d¹⁰ electrons, and π-conjugated [NO₃]⁻ triangles, generates a new nitrate NLO material, Bi₃TeO₆OH(NO₃)₂, which exhibits an enhanced phase-matchable NLO response of three times that of KH₂PO₄ (3×KH₂PO₄), exceeding those of most nitrate NLO materials. Remarkably, the new material did not show obvious weight loss and degeneration of NLO response after being dipped in de-ionized water for 24 h, indicating that it is highly resistant to water. Theoretical calculations reveal that foreign water molecules cannot stably stay in the crystal lattice of Bi₃TeO₆OH(NO₃)₂. These findings highlight the introduction of diverse chromophores into the nitrate systems as an effective approach for developing practical nitrate NLO materials that are of high water-resistance and good optical performance. [ABSTRACT FROM AUTHOR]