New hydroxyl free radical sensor based on coumarin 3 carboxylic acid intercalated into layered double hydroxide hydrotalcite

Sumeet Kumar ,  Geo Paul ,  Leonardo Marchese ,  Luca Palin ,  Gianluca Croce ,  Enrico Boccaleri ,  Marco Milanesio 

Universita degli Studi del Piemonte Orientale, DISTA, Viale T. Michel 11., Alessandria 15121, Italy


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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Presentation: Oral at E-MRS Fall Meeting 2009, Symposium F, by Sumeet Kumar
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-11 11:41
Revised:   2009-06-30 20:19
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