中文摘要：

在微波辅助条件下,合成了具有蓝色荧光特性的甲醛功能化的聚乙烯亚胺（FPEI）.在硫酸介质中,FPEI表面质子化的氨基通过静电作用吸附Cr（Ⅵ）,致使FPEI 480 nm处的荧光强度逐渐降低.同时,罗丹明B酰肼（RBH）被Cr（Ⅵ）氧化生成强荧光发射的罗丹明B,体系的吸光度在250～600 nm范围显著增强,覆盖了FPEI的激发和发射光谱,由此产生的内滤效应导致FPEI的荧光进一步降低.罗丹明B 580 nm处荧光强度和FPEI 480 nm处荧光强度的比值（F_（580）/F_（480））与Cr（VI）的浓度呈良好的线性关系,在紫外灯照射下体系的荧光由蓝色逐渐变为橙黄色,由此建立了一种新型的比率及可视化荧光测定六价铬的新方法.在最优条件下,比率荧光测定的线性范围为0.1～3.6μmol/L,检出限（3σ）为12 nmol/L,可视化荧光检测的线性范围为0.4～2.8μmol/L.该方法简单、快速,灵敏度及选择性好,用于实际样品测定的回收率为90%～109%.

英文摘要：

Formaldehyde functionalized fluorescent polyethyleneimine（ FPEI） were prepared via microwaveassisted synthesis. In H_2SO_4 media,the amine groups on the FPEI surface would be protonated and adsorb Cr（ Ⅵ） via electrostatic attraction,and the fluorescence intensity of the FPEI at 480 nm decreased accordingly. At the same time,potassium dichromate can oxidize rhodamine B hydrazide（ RBH） to rhodamine B in acidic aqueous conditions,resulting in recovery of rhodamine B fluorescence and absorbance,the absorption bands of which ranged from 250 nm to 600 nm,fully covering the emission and excitation bands of FPEI.Thus,the inner filter effect occurring in FPEI/RBH system led to further decrease of the fluorescence intensity of the FPEI. The fluorescence change ratio（ F580/F480） between the fluorescence intensity of rhodamine B at580 nm and that of FPEI at 480 nm has a good linear correlation with the concentration of Cr（ Ⅵ）,and a noticeable blue to orange color change was detected under an ultraviolet lamp if Cr（ Ⅵ） solution was mixed with the FPEI/RBH. Based on the phenomena,a novel rapid ratiometric and visual fluorescence method for determination of Cr（ Ⅵ） was developed. Under optimal conditions,the ratio fluorescence intensity F580/F480 increased linearly with the concentration of Cr（ Ⅵ） ranging from 0. 1 μmol/L to 3. 6 μmol/L with a detection limit of 12 nmol/L. In addition,the change of fluorescence color was related to the concentration of Cr（ Ⅵ） in the range of 0. 4—2. 8 μmol/L. The proposed method,being highly selective,simple and rapid,could be applied to determine the concentration of Cr（ Ⅵ） samples with recovery of 90%—109%.