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Mid-ultraviolet Light-Emitting Diode Detects Dipicolinic Acid

Volume 58, Number 11 (Nov. 2004) Page 1360-1363

Li, Qingyang; Dasgupta, Purnendu K.; Temkin, Henryk; Crawford, M.H.; Fischer, A.J.; Allerman, A.A.; Bogart, K.H.A.; Lee, S.R.

Dipicolinic acid (DPA, 2,6-pyridinedicarboxylic acid) is a substance uniquely present in bacterial spores such as that from anthrax (B. anthracis). It is known that DPA can be detected by the long-lived fluorescence of its terbium chelate; the best limit of detection (LOD) reported thus far using a large benchtop gated fluorescence instrument using a pulsed Xe lamp is 2 nM. We use a novel AlGaN light-emitting diode (LED) fabricated on a sapphire substrate that has peak emission at 291 nm. Although the overlap of the emission band of this LED with the absorption band of Tb-DPA (λmax doublet: 273, 279 nm) is not ideal, we demonstrate that a compact detector based on this LED and an off-the-shelf gated photodetection module can provide an LOD of 0.4 nM, thus providing a basis for convenient early warning detectors.