Photoinduced degradation of indigo carmine: insights from a computational investigation

Abstract

In this work, we present a computational investigation on the photoexcitation of indigo carmine (IC). Physical insights regarding IC photoexcitation and photolysis were obtained from a fundamental perspective through quantum chemistry computations. Density functional theory (DFT) was used to investigate the ground state while its time-dependent formalism (TD-DFT) was used for probing excited state properties, such as vertical excitation energies, generalized oscillator strengths (GOS), and structures. All the computations were undertaken using two different approaches: M06-2X/6-311+G(d,p) and CAM-B3LYP/6-311+G(d,p), in water. Results determined using both methods are in systematic agreement. For instance, the first singlet excited state was found at 2.28 eV (with GOS = 0.4730) and 2.19 eV (GOS = 0.4695) at the TD-DFT/CAM-B3LYP/6-311+G(d,p) and TD-DFT/M06-2X/6-311+G(d,p) levels of theory, respectively. Excellent agreement was observed between the computed and the corresponding experimental UV-Vis spectra. Moreover, results suggest IC undergoes photodecomposition through excited state chemical reaction rather than via a direct photolysis path. To the best of our knowledge, this work is the first to tackle the photoexcitation, and its potential connections to photodegradation, of IC from a fundamental chemical perspective, being presented with expectations to motivate further studies. KeywordsIndigo carmine • Dye degradation • Density functional theory (DFT) • Time-dependent density functional theory (TD-DFT) This paper belongs to Topical Collection XX-Brazilian Symposium of Theoretical Chemistry (SBQT2019)

The Biodegradation of Indigo Carmine by Bacillus safensis HL3 Spore and Toxicity Analysis of the Degradation Products

“…Terminal desulfonation from indigo carmine is considered to be faster than the internal conversion [ 40 ]. Some treatment methods for the degradation of indigo carmine, such as photocatalytic degradation [ 41 ], photodegradation [ 42 ], O 3 , non-thermal plasma [ 7 ], bicarbonate-activated peroxide [ 43 ], Fenton-like [ 41 ], and fungal laccase [ 44 ], do not desulfonate indigo carmine.…”

Probing ground and low-lying excited states for indole derived compounds of potential herbicide action

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