Photophysics and reductive quenching reactivity of gadusol in solution

Abstract

The photostability and photophysics of gadusol in aqueous solution has been studied. The photodecomposition quantum yields (ca. 4 × 10(-2) and 1 × 10(-4) at acidic and neutral pH, respectively) confirm the high photostability of the metabolite, independently of the presence of oxygen, under physiological conditions. The nature of the electronic transition of gadusol has been assigned as π→π* on the basis of the solvatochromic shifts of the UV absorption spectrum and the time-dependent density functional theory calculation of the vertical transition energies. The results from the photoacoustic calorimetry point to the rapid non-radiative decay as the dominant relaxation pathway of the excited species at pH 7, which is consistent with the proposed UV-sunscreening role of the molecule in the early atmosphere. Laser flash photolysis experiments probed that the ground state of the enolate form (gadusolate) undergoes electron transfer reactions with some triplet sensitizers in water or methanol solution. A rate constant of 2 × 10(8) M(-1) s(-1) has been determined for the quenching of rose bengal triplet state in water at pH 7. This reductive quenching reactivity may be considered as one of the underlying mechanisms that support the antioxidant capacity of gadusol in biological environments.

Highly luminescent, off-stoichiometric CuxInyS2/ZnS quantum dots for near-infrared fluorescence bio-imaging

“…4). 53,54 Therefore, the high PLQY of CIS/ZnS QDs was not derived from the PL quenching of rhodamine 6G, so the determined PLQY is reliable. The measured PLQYs of CIS QDs when Cu/In ¼ 1.1, 0.41, and 0.25 were 7.9, 7.3, and 9.2%, respectively (Table 1).…”

Spectral properties of rhodamine 6G in smectite dispersions: Effect of the monovalent cations

“…The emission form the molecular aggregates indicates the mixed structural character of rhodamine assemblies, which might be due to a more complicated molecular structure of the dye. Similar R6G species were identified in other systems and the spectral properties were described [17,[80][81][82][83]. It was found for R6G molecules, intercalated in cetyltrimethylammonium/montmorillonite hybrid system that R6G molecules exist as two or more distinctive fluorescence species [84].…”

“…The properties of this dye, especially in the systems with clay minerals, have been extensively studied. Therefore, the interpretation of the spectra could be based on knowledge of a large number of previously published papers [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. The processes and the main characteristics of the colloidal systems are compared with the phenomena observed for MB/alkali metal ion-exchanged smectite [35].…”

“…The formation of H-aggregates leads to the changes in the relaxation pathways of excited molecules and to the loss of fluorescence quantum yields. The rhodamine dyes are widely used for lasers, and their interaction with smectites has been extensively studied [11][12][13][14][15][16][17][18][19][20][21][22][24][25][26][27][43][44][45][46][47][48][49][50][51][52][53]. At the beginning of the reaction process, rhodamine isolated molecules (monomers) are predominantly present in smectite colloids; molecular aggregates form with reaction time [20,21].…”

“…Another group of the hybrid materials with intercalated organic dyes are based on layered inorganic matrices, such as layered phosphates [9], niobates [10], silicates (e.g. smectites) [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27], etc.…”