The hydroxyl radical is the most reactive oxygen species (ROS), presenting two problems for the construction of sensors: (a) inability to penetrate significantly into any matrix without being destroyed; (b) ability to oxidize (and photobleach) most potential reference dyes (1). Here we present the synthesis and properties of an inorganic-organic hybrid material that overcomes the above two basic problems and serves as an effective hydroxyl free radical sensor. A hydroxyl free radical sensing moiety (2) coumarin-3-carboxylic acid (3CCA), was intercalated into the layered double hydroxide (HTLC) framework using one-pot hydrothermal synthesis (3).

The obtained layered inorganic/organic hybrid material with empirical formula: [M(II)_0.65M(III)_0.35(OH)₂](X)_0.35.n H₂0], where M(II) = (Zn²⁺), M(III) = (Al³⁺ with Eu³⁺ substituting the Al³⁺ sites), and X = anionic 3CCA, along with having lanthanide (Eu³⁺) ion substitution into the layered structure, enhances the luminescence decay lifetime thus enabling easier temporal variation of the luminescence measurements (4). The ZnAlEu(3CCA) HTLC materials with M(II)/M(III) ≈ 2.0 was synthesized and further characterized by XRPD/FTIR/TGA/SEM-EDX/SS-NMR techniques along with solid-state luminescence measurements. The generation of hydroxyl free radical from the aqueous phase reaction of copper chloride and Vitamin C (Ascorbic acid) has already been well studied (5) and henceforth used as a probe for our work.

The synthesized hybrid sensor material is promising because of its observed luminescence in the visible region and high-temperature resistance as indicated by the XRPD measurements and TGA/DTG analysis moreover, the two basic problems in the development of hydroxyl free radical sensor should be overcome.

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1. Synthesis and Characterization of host-guest materials with charge transfer complexes of Coumarin:TCNQ inserted into hydrotalcite for LED applications.
2. Synthesis and characterization of (electro)luminescent materials based on charged [Eu³⁺/Organic chelate]^- complexes within layered double hydroxide (Hydrotalcite) as host matrix
3. In situ simultaneous Raman/X-ray powder diffraction study of transformations occurring at non-ambient conditions
4. Unraveling the polimorph space of the product of a 2+2 photodimerization of (E)-furylidenoxindole by an in situ Raman/X-ray powder diffraction study