基于机械力化学作用制备荧光纳米纤维素

采用机械力化学法，以磷钨酸-柠檬酸为复合水解剂处理竹浆纤维，再进一步加入半胱氨酸，使降解的纤维素发生接枝反应，从而在水相中一锅法制备高荧光、高量子产率荧光纳米纤维素（fluorescent cellulose nanocrystals, F-CNC）。研究考察了半胱氨酸溶液浓度、反应时间、反应温度等因素对F-CNC的得率和荧光强度的影响。采用紫外分光光度计（UV-vis）、荧光分光光度计、透射电子显微镜（TEM）、傅里叶红外光谱仪（FTIR）、核磁共振光谱仪（NMR）、X-ray光电子能谱（XPS）、X射线衍射仪（XRD）以及热分析仪（TGA）等对F-CNC的光学性质、形貌结构、化学结构、晶体结构以及热稳定性等进行了表征分析。结果表明，半胱氨酸溶液浓度为1mol/L，反应时间为8h，反应温度为140℃，F-CNC的得率为56.8%，荧光量子产率达到34.24%，荧光寿命达到3.44ns，且F-CNC的直径在20~40nm，长度为150~300nm。基于机械力化学法制备F-CNC工艺简便、绿色环保且所制备的F-CNC在水中具有良好的分散性，在防伪和生物传感器中具有潜在的应用前景。

Preparation of fluorescent cellulose nanocrystals based on mechanical force chemical effect

Fluorescent cellulose nanocrystals (F-CNC) with high fluorescence and high quantum yield were prepared via one-pot reaction under mechanochemical action. During the reaction, bamboo pulp was used as the raw material, phosphotungstic acid and citric acid as the composite catalyst to graft cysteine to the surface of the degraded cellulose. The effects of cysteine solution concentration, reaction time and reaction temperature on the yield and the fluorescence intensity of F-CNC were analyzed. The optical properties, morphology, chemical structure, crystal structure and thermal stability of F-CNC were studied by using UV-vis spectroscopy (UV-vis), fluorescence spectrometry, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), X-ray photoelectron spectroscopy (XPS), X-ray diffractometry(XRD) and thermal gravimetric analysis(TGA), respectively. The results indicated that the diameters of the obtained F-CNC ranged from 20nm to 40nm and the lengths were from 150nm to 300nm. In addition, the fluorescence intensity of F-CNC reached the highest, the yield and fluorescence quantum yield of F-CNC were 56.8% and 34.24% respectively and the fluorescence lifetime was 3.44ns, when the cysteine solution was 1mol/L, the reaction dry time was 8h, and the reaction temperature was 140℃.This work provided a simple and environmentally benign approach to prepare F-CNC, which has good dispersibility in water and a great potential in anti-counterfeiting and biosensors.