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Photocatalysed decolouration of indigo in solution via in situ generation of an organic hydroperoxide

Lookup NU author(s): Sulafa Nassar, Dr Dumitru Sirbu, Emeritus Professor Anthony Harriman



This is the authors' accepted manuscript of an article that has been published in its final definitive form by Nature, 2019.

For re-use rights please refer to the publisher's terms and conditions.


Indigo, an emblematic violet dye used for thousands of years to colour fabric, is resistant to fading on exposure to sunlight. Prior work has indicated that indigo is reactive towards both hydroperoxyl radicals and superoxide anions in solution. In order to promote photobleaching of indigo, we have utilised a BOPHY-based (BOPHY = aryl fused symmetrical pyrrole-BF2 complex) chromophore known to form both superoxide ions and a stable alkyl hydroperoxide under illumination in aerated solution. Selective irradiation of the photocatalyst causes relatively fast fading of indigo, with the rate increasing gently with increasing concentration of indigo. Molecular oxygen and light are essential for effective bleaching. One molecule of photocatalyst can bleach more than 40 molecules of indigo. An active component of the photocatalyst is a butylated hydroxytoluene (BHT) residue which itself quenches the triplet excited state of indigo. This provides an ancillary mechanism for effecting photofading of indigo but, because the triplet is formed in very low yield, this route is less practical.

Publication metadata

Author(s): Nassar SJM, Sirbu D, Harriman A

Publication type: Article

Publication status: Published

Journal: Photochemical & Photobiological Sciences

Year: 2019

Volume: 18

Issue: 12

Pages: 2875-2883

Online publication date: 07/11/2019

Acceptance date: 06/11/2019

Date deposited: 21/01/2020

ISSN (print): 1474-905X

ISSN (electronic): 1474-9092

Publisher: Nature


DOI: 10.1039/c9pp00355j

PubMed id: 31720669


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