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Structural, reactivity and spectroscopic properties of vitamin A in its retinoid forms are examined. Time-Dependent DFT approach is used to study the first three electronically excited states of retinol, retinyl ester, retinol acetate and retinal. Singlet-singlet type vertical electronic transitions are considered. Computational simulations are carried out in the gas phase and in solution, within the polarizable continuum model. Once vitamin A is a natural fluorophore in milk, our findings contribute to understand its behavior in different environments, either to differentiate types of milk or to assess the quality of dairy products.

In this paper, thermally stable lead-bismuth-borate glasses were doped with 0.5 mol% of Pr3+ ions at several concentration levels of Yb3+ ions. Structural characterizations were performed via Raman, differential scanning calorimetry, optical absorption and fluorescence spectra. The Judd–Ofelt intensity parameter, $${\Omega }_2$$ Ω 2 , of Pr3+ doped glass was comparatively higher than those from reported ones, which reflects the increase of co-valency and asymmetry of chemical bonds in the local environment of Pr3+. Near-infrared emission in 900–2200 nm wavelength range was recorded through 443 nm blue laser pumping. Visible to near-IR quantum cutting and concentration quenching mechanisms were discussed to understand the luminescent behaviour. Intense IR emission ($$\sim 1.0\,\upmu {\text {m}})$$ ∼ 1.0 μ m ) features generated by absorbing one visible photon leads to quantum efficiencies close to 128% in Pr3+/Yb3+ co-doped samples which may improve the solar spectrum absorption and accordingly, increase the efficiency of c-Si solar cells. Emission cross-section, lifetime, figure of merit and gain bandwidth corresponding to Pr3+: $$^3F_2 \rightarrow ^3H_4$$ 3 F 2 → 3 H 4 ($$\sim 2.0\,\upmu$$ ∼ 2.0 μ m) were comparatively reported suggesting that the glass with molar composition 0.5Pr3+/0.1Yb3+ might be a potential candidate for $$\sim 2.0\,\upmu$$ ∼ 2.0 μ m laser operation with low pump threshold.

In this paper, thermally stable lead-bismuth-borate glasses were doped with 0.5 mol% of Pr

We discuss here the role of environment in the structural and spectroscopic properties of vitamin A in its retinoid forms: retinol and retinal. The analyzed compounds show three singlet excited states exhibiting wavelengths between 472 and 273 nm according to the medium. The transitions involve HOMO, LUMO, HOMO-1, LUMO and HOMO, LUMO+1 orbitals.