为降低魔芋葡甘聚糖(KGM)的分子质量,提升其在食品、医药、材料等领域的应用潜力,采用激光辅助过氧化氢的方法对质量浓度为0.01 g/mL的 KGM溶液进行降解,借助粘度计、流变仪初步确定较优的降解条件,再利用差示扫描量热法(DSC)、傅里叶变换红外(FT-IR)光谱仪对筛选出的KGM降解产物进行表征,并初步探究出其降解机理。结果表明:当激光功率为10 W,过氧化氢的体积分数为1.5%,处理时间为2 min时,KGM的降解效果较佳,黏度由7.2 Pa·s降至3.17 Pa·s;在该降解条件下得到的KGM降解产物的储能模量与损耗模量的交汇点后移,分子间的缠结减弱,分子质量减小;DSC热吸收峰对应的温度由301 ℃升为326 ℃,热稳定性升高;降解前后KGM的红外光谱无明显变化,特征官能团保持不变。本研究可为KGM的有效降解提供一种新思路。

The importance of methylammonium lead triiodide (CH3NH3PbI3 or MAPbI₃) organic-inorganic hybrid perovskites has shot up dramatically since their use in highly efficient thin-film perovskite solar cells (PSCs). However, the basic structural characterization of these fascinating materials remains sparse. In particular, Raman spectroscopy, which is a powerful vibrational spectroscopy characterization tool and complements other characterization methods, of MAPbI₃ under ambient conditions is plagued with difficulties. Here, a systematic ambient Raman spectroscopy characterization study of MAPbI₃ thin films is conducted under different conditions (excitation laser wavelength, integration time, filter characteristic). The results from this study help elucidate the possible sources of artifacts in the Raman spectra, and raise the awareness of the challenges in the ambient Raman spectroscopy of MAPbI₃ perovskites. Approaches to overcome these challenges are suggested.