Solovieva Anna B, Kopylov Alexander S, Savko Marina A, Zarkhina Tatiana S, Lovskaya Darya D, Lebedev Artyom E, Menshutina Natalia V, Krivandin Alexey V, Shershnev Ilya V, Kotova Svetlana L, Timashev Peter S
N.N.Semenov Institute of Chemical Physics, Department of Polymers and Composites, 4 Kosygin St., 119991, Moscow, Russia.
D.Mendeleev University of Chemical Technology of Russia, 9 Miusskaya Sq., 125047, Moscow, Russia.
Sci Rep. 2017 Oct 3;7(1):12640. doi: 10.1038/s41598-017-12945-9.
We have prepared photocatalytic systems based on tetraphenylporphyrins (TPP) immobilized on calcium alginate solid gels in the conditions of thermal drying on air (xerogel), freeze drying in vacuum (cryogel) and supercritical drying in the supercritical carbon dioxide (scCO) medium (aerogel). As a test reaction to measure the prepared systems' efficiency, we studied tryptophan photooxidation in the aqueous medium. We have demonstrated that the systems with aerogel as a carrier exhibited the highest photocatalytic efficiency. In that case, the rate constant for the test substrate (tryptophan) oxidation exceeds the corresponding rate constants of similar systems based on xerogel and cryogel by more than 5 times. Moreover, the aerogel-based photocatalytic systems demonstrated enhanced functional stability and a possibility of multiple use of such a catalyst in tryptophan oxidation. Based on the data of small-angle X-ray scattering and thermooxidative destruction, we have made a conclusion about the relationship between the high photocatalytic activity of aerogel-immobilized TPP and formation of a developed porous aerogel structure in the conditions of drying in the scCO medium, which is stabilized due to formation of additional complex bonds of calcium ions with fragments of glycoside rings.
我们制备了基于固定在海藻酸钙固体凝胶上的四苯基卟啉（TPP）的光催化体系，制备条件分别为在空气中热干燥（干凝胶）、在真空中冷冻干燥（冷冻凝胶）以及在超临界二氧化碳（scCO₂）介质中进行超临界干燥（气凝胶）。作为衡量所制备体系效率的测试反应，我们研究了水性介质中色氨酸的光氧化反应。我们已证明，以气凝胶为载体的体系表现出最高的光催化效率。在这种情况下，测试底物（色氨酸）氧化的速率常数比基于干凝胶和冷冻凝胶的类似体系的相应速率常数高出5倍以上。此外，基于气凝胶的光催化体系表现出增强的功能稳定性，并且这种催化剂在色氨酸氧化反应中具有多次使用的可能性。基于小角X射线散射和热氧化破坏的数据，我们得出结论：在scCO₂介质中干燥条件下，气凝胶固定的TPP的高光催化活性与发达的多孔气凝胶结构的形成之间存在关联，该结构由于钙离子与糖苷环片段形成额外的络合键而得以稳定。
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