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Photophysical properties of diethylhexyl 2,6-naphthalate (Corapan TQ), a photostabilizer for sunscreens

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Abstract

Diethylhexyl 2,6-naphthalate (DEHN, tradename Corapan TQ) is used as a photostabilizer for a widely-used UV-A absorber, butylmethoxydibenzoylmethane (BMDBM). The photophysical properties of DEHN have been studied through measurements of the transient absorption, fluorescence, phosphorescence and EPR spectra in ethanol. The energy level of the lowest excited singlet state of DEHN is higher than that of BMDBM (enol form). The singlet–singlet energy transfer from BMDBM to DEHN is energetically unfavourable. The energy level of the lowest excited triplet (T1) state of DEHN is lower than that of BMDBM. It is probable that the mechanism of photostabilization of BMDBM by DEHN is the triplet–triplet energy transfer from BMDBM to DEHN. The observed phosphorescence spectrum, T1 lifetime and zero-field splitting parameters indicate that the T1 state of DEHN can be regarded mainly as a locally excited 3ππ* state within naphthalene. The sum of the quantum yields of fluorescence of DEHN (0.59 ± 0.09) and singlet oxygen generation by DEHN (0.44 ± 0.04) is almost unity in ethanol. About 60% of the UV energy absorbed by DEHN is released as fluorescence, while about 40% is used to produce the excited triplet state. The photoexcited states of 2-naphthoic acid have been studied for comparison.

Graphical abstract: Photophysical properties of diethylhexyl 2,6-naphthalate (Corapan TQ), a photostabilizer for sunscreens

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Publication details

The article was received on 16 May 2018, accepted on 19 Jul 2018 and first published on 20 Jul 2018


Article type: Paper
DOI: 10.1039/C8PP00204E
Citation: Photochem. Photobiol. Sci., 2018, Advance Article
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    Photophysical properties of diethylhexyl 2,6-naphthalate (Corapan TQ), a photostabilizer for sunscreens

    R. Shimizu, M. Yagi, N. Oguchi-Fujiyama, K. Miyazawa and A. Kikuchi, Photochem. Photobiol. Sci., 2018, Advance Article , DOI: 10.1039/C8PP00204E

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