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    A DFT analysis for synthesizing vitamin A
    (American Chemical Society, 2024-11-25)
    Vitamin A deficiency (VAD) is a major nutritional concern in lower-income countries. It is responsible for thousands of deaths in those countries every year. Thus, finding the optimal route for vitamin A synthesis is essential, especially for the countries that are influenced by VAD. Three mechanisms of synthesizing Vitamin A have been evaluated by Density Functional Theory (DFT) calculations. This experiment investigated the BASF C15 + C5 Wittig approach, the Rhône-Poulenc C15 + C5 Julia approach, and the Kuraray C10 + C10 approach. The electronic energy, highest occupied molecular orbital energy, and dipole moments were calculated using the B3LYP functional and the 3-21g basis set. The energy profiles of these synthesis routes were compared to determine the most energetically favorable method. The Julia approach has the lowest energy change, indicating its higher efficiency in terms of energy compared to the Wittig and Kuraray methods. It is shown that other factors such as scalability and raw material availability should also be considered in industrial applications.
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    Cu-Doped SnO₂ Nanocrystals: Tunable Magnetism, Critical Incorporation Limit, and Defect Configuration Analysis by EPR and Ab Initio DFT
    (American Chemical Society, 2025-11-05)
    Copper in oxide semiconductors exhibits distinct electronic and magnetic behavior depending on its oxidation state, with Cu¹⁺ acting as a nonmagnetic impurity and Cu²⁺ contributing to the magnetic moment. In SnO₂, Cu incorporation represents a heterovalent substitution for Sn⁴⁺, which inherently promotes formation of compensating defects, particularly oxygen vacancies, that can strongly influence electronic and magnetic properties. To elucidate these effects, we investigated Cu-doped SnO₂ nanocrystals through combined experimental and theoretical approaches. Electron paramagnetic resonance (EPR) revealed that Cu incorporation of up to 3% enhances resonance intensity, consistent with isolated Cu²⁺ ions in the SnO₂ matrix. Beyond 3%, the EPR signal intensity decreases, and hyperfine parameters stabilize due to Cu²⁺ clustering and spin–spin interaction. Magnetization measurements revealed a paramagnetic phase (reflecting the presence of isolated Cu²⁺) that coexists with a ferromagnetic phase attributed to bound magnetic polarons and magnetic clustering. Complementary first-principles calculations showed that Cu substitution modifies the electronic structure by introducing localized density of states variations and altering the spin–charge density distribution, particularly near oxygen vacancies. Deeper in-plane defects were found to stabilize magnetization, whereas surface defects promoted competing ferromagnetic and antiferromagnetic interactions. Structural characterization by X-ray diffraction and morphological analysis using high-resolution transmission electron microscopy further confirmed lattice compression and particle size reduction with increasing Cu-content. The calculated and experimental findings provide a comprehensive and interconnected understanding, not yet emphasized in the literature, of the interplay among defects, doping, and magnetism in Cu-doped SnO₂.
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