二氧化碳辅助壳聚糖/银凝胶小球的制备及其催化性能的研究

Preparation and Catalytic Properties of Carbon Dioxide-assisted Chitosan/Silver Hydrogel Beads

利用二氧化碳(CO_(2))对壳聚糖的改性作用,制备了负载银纳米粒子(AgNPs)的壳聚糖凝胶小球。首先测试了壳聚糖/1%醋酸溶液的电导率和黏度随CO_(2)通入时间的变化规律,证实了CO_(2)能与壳聚糖的氨基发生反应,并且当CO_(2)通入时间为30 min时,反应产生的氨基甲酸含量最高。从而利用反应产生的氨基甲酸有效增加了壳聚糖上银的配位点。通过扫描电镜(SEM),X射线衍射(XRD),X射线光电子能谱(XPS),衰减全反射傅里叶红外光谱(ATR-FTIR)对小球进行表征,结果显示Ag与壳聚糖上的N,O配位,CO_(2)改性后的壳聚糖载银能力提高了一倍。当CO_(2)通入时间为30 min时,负载的AgNPs含量最大并且尺寸最小。最后,将制备的载银壳聚糖(CS-Ag)凝胶小球用于催化活性染料亚甲基蓝的还原反应。结果表明,在相同的反应条件下,CO_(2)改性的CS-Ag小球催化还原亚甲基蓝的反应速率高于未改性的小球,且CO_(2)改性时间为30 min的小球催化速率最快。此外,CO_(2)改性的CS-Ag小球的催化反应对温度更为敏感,反应速率的差异随着反应温度的升高而增大,最高可达3倍左右。

The bioderived chitosan was modified by carbon dioxide(CO_(2))and utilized to prepare hydrogel beads loaded with silver nanoparticles(AgNPs).The reaction intermediate between CO_(2)and the amine group of chitosan,carbamic acid group,was proven effective in increasing the coordination site of chitosan for silver.The conductivity and viscosity changes of the solution confirmed the occurrence of the reaction and that the largest amount of carbamic acids was formed at 30 min.The scanning electron microscopy(SEM),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS)and attenuated total reflectance infrared resonance(ATR-FTIR)results confirmed that the silver loading capacity of chitosan after modification with CO_(2)was doubled.The silver content was the largest and the AgNPs size was the smallest when the reaction time was 30 min.The results also showed that the Ag atoms were coordinated with the N and O atoms of chitosan.The prepared silver-loaded chitosan(CS-Ag)hydrogel beads were applied to catalyze the methylene blue reduction reaction.The reaction rate catalyzed by CO_(2)-modified CS-Ag beads were greater than that catalyzed by unmodified beads under the same conditions,and the beads modified for 30 min performed the best.Also,the reactions catalyzed by CO_(2)-modified CS-Ag beads were more sensitive to temperature,and with the increase of reaction temperature,the difference of reaction rate became larger,up to about three times of the original one.