School of Pharmacy and Biomolecular Sciences, University of Brighton, Brighton, UK; Department of Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, 22 100, Lund, Sweden.
School of Ocean and Earth Science, University of Southampton, National Oceanography Centre (Southampton), UK.
Carbohydr Polym. 2018 Jul 15;192:166-175. doi: 10.1016/j.carbpol.2018.03.038. Epub 2018 Mar 15.
3D-macroporous chitosan-based scaffolds (cryogels) were produced via growth of metal-polymer coordinated complexes and electrostatic interactions between oppositely charged groups of chitosan and metal ions under subzero temperatures. A mechanism of reduction of noble metal complexes inside the cryogel walls by glutaraldehyde is proposed, which produces discrete and dispersed noble metal nanoparticles. 3D-macroporous scaffolds prepared under different conditions were characterised using TGA, FTIR, nitrogen adsorption, SEM, EDX and TEM, and the distribution of platinum nanoparticles (PtNPs) and palladium nanoparticles (PdNPs) in the material assessed. The catalytic activity of the in situ synthesised PdNPs, at 2.6, 12.5 and 21.0 μg total mass, respectively, was studied utilising a model system of 4-nitrophenol reduction. The kinetics of the reaction under different conditions (temperature, concentration of catalyst) were examined, and a decrease of catalytic activity was not observed over 17 treatment cycles. Increasing the temperature of the catalytic reaction from 10 to 22 and 35 °C by PdNPs supported within the cryogel increased the kinetic rate by 44 and 126%, respectively. Turnover number and turnover frequency of the PdNPs catalysts at room temperature were in the range 0.20-0.53 h. The conversion degree of 4-nitrophenol at room temperature reached 98.9% (21.0 μg PdNPs). Significantly less mass of palladium nanoparticles (by 30-40 times) was needed compared to published data to obtain comparable rates of reduction of 4-nitrophenol.
通过在零下温度下生长金属-聚合物配位配合物和壳聚糖与金属离子之间相反电荷基团之间的静电相互作用，制备了 3D 大孔壳聚糖基支架（冷冻凝胶）。提出了在冷冻凝胶壁内通过戊二醛还原贵金属配合物的机制，该机制产生离散和分散的贵金属纳米粒子。使用 TGA、FTIR、氮气吸附、SEM、EDX 和 TEM 对在不同条件下制备的 3D 大孔支架进行了表征，并评估了铂纳米粒子（PtNPs）和钯纳米粒子（PdNPs）在材料中的分布。使用 4-硝基苯酚还原的模型体系研究了原位合成的 PdNPs（分别为 2.6、12.5 和 21.0μg 总质量）的催化活性。研究了不同条件（温度、催化剂浓度）下反应的动力学，在 17 次处理循环中未观察到催化活性降低。通过在冷冻凝胶内负载的 PdNPs 将催化反应的温度从 10°C 升高到 22°C 和 35°C，动力学速率分别提高了 44%和 126%。在室温下，PdNPs 催化剂的周转数和周转频率在 0.20-0.53h 之间。在室温下，4-硝基苯酚的转化率达到 98.9%（21.0μg PdNPs）。与已发表的数据相比，需要的钯纳米粒子质量显著减少（减少 30-40 倍），即可获得可比的 4-硝基苯酚还原速率。
