Latent fingerprints (LFPs) at the crime scene are served as important clues to locate the trajectory of criminal behavior and portray the characteristics of the suspect. Therefore, visualizing LFPs is of considerable significance. In this work, the europium metal-organic framework (Eu-MOF) sensor was successfully constructed for sensitive detection of gallic acid (3,4,5-trihydroxybenzoic acid, GA) and visualization of the sweat LFPs. The boric-acid-modified Eu-MOF was prepared by using the simple one-pot solvothermal method using Eu as the metal ion center and 3,5-dicarboxybenzeneboronic acid (BBDC) as the organic ligand. The sensor showed desirable photoluminescent performance through the chelating of BBDC with Eu3+. The sensor exhibited the satisfactory linear relationship to GA in the range of 1 nM to 20 nM with a low detection limit of 0.34 nM under the optimized conditions. The prepared sensor with ideal selectivity to GA was successfully applied for visualizing LFPs on porous substrates with the high contrast and superior stability. Given the good performance of the sensor, all fingerprint images obtained from 1 200 samples presented clear friction ridges and met the identification criteria. Notably, the sensor had less impact on the subsequent deoxyribonucleic acid (DNA) detection, displaying a promising perspective for applications in extracting physical evidence of site investigation.

采用溶剂热合成方法, 合成了一例金属-有机框架{［Zn2(OH)(TZI)·2H2O］·6DMF}n (1)(TZI为5-四氮唑间苯二甲酸), 并利用单晶X射线衍射、元素分析、红外光谱、热重分析、粉末X射线衍射等手段对化合物进行了结构表征。单晶X射线衍射结果显示配合物1呈现出三维孔道结构, 并且孔道中存在未配位的羧基和配位的水分子。随后通过后合成法将Eu(Ⅲ)离子引入到框架中得到具有红光发射特征的Eu(Ⅲ)@1。在275 nm的激发光下, Eu(Ⅲ)@1存在两组荧光发射, 第一组在418 nm处的宽峰为配合物1的荧光发射, 荧光源于有机配体的吸收和发射; 第二组五个发射峰为Eu(Ⅲ)离子的红色特征发射峰, 其主峰为619 nm。尿液中其他成分抗干扰性实验结果表明, Eu(Ⅲ)@1荧光探针对于生物标记物1-萘酚非常敏感, 能够导致红色荧光猝灭(619 nm), 并伴有青色荧光增强(465 nm), 对1-萘酚具有高选择性。荧光滴定实验结果显示Eu(Ⅲ)@1基于465和619 nm处荧光发射峰对1-萘酚的检测限分别为6.95 μmol/L和1.75 mmol/L。

通过高温固相法制备了一系列Eu掺杂的Sr1.95+xLi1-xSi1-xAlxO4F(0≤x≤0.25)发光材料, 并详细研究了所制备Sr2LiSiO4F化合物的晶体结构及相组成。利用Al3+-Sr2+离子对取代Si4+-Li+ 离子对的晶体位点工程, 对Eu2+占据的Sr多面体位点进行调控, 实现单相Sr1.95+xLi1-xSi1-xAlxO4F(0≤x≤0.25)材料中Eu2+和Eu3+的共存, 获得了Sr1.95+xLi1-xSi1-xAlxO4F∶Eu体系从绿光到红光的发光调谐。 通过对Sr1.95+xLi1-xSi1-x-AlxO4F∶Eu材料中的Eu2+和Eu3+离子在25～300 ℃范围内温度依赖性光谱的研究发现Eu2+和Eu3+呈现不同的温度敏感特性。经计算, Sr1.95+xLi1-xSi1-xAlxO4F∶0.05Eu发光材料的温度传感绝对灵敏度和相对灵敏度可分别达到2.83%·K-1与0.66%·K-1, 进一步证实了所制备发光材料在温度传感方面的应用潜力。

采用高温固相法合成出正交相和三斜相结构的BiNbO4∶Eu3+样品，利用X 射线衍射(XRD)、拉曼光谱、吸收光谱和荧光光谱对样品的结构和光学性能进行了研究。结果表明: 900 ℃合成样品为正交相结构α-BiNbO4，而1 200 ℃得到三斜相结构β-BiNbO4。吸收光谱得到α相和β相BiNbO4的光学带隙分别为2.69 eV和2.96 eV，与第一性原理的理论结果2.640 eV和3.032 eV相吻合。Eu3+掺杂诱导二者的光学带隙蓝移至2.89 eV和3.05 eV，有效改变了其光响应范围。荧光光谱表明: Eu3+在两种结构的最强荧光峰均来自5D0→7F2电偶极跃迁，最强荧光峰分别位于615 nm和611 nm。Eu3+在β-BiNbO4中的荧光强度更高，而且其5D0→7F2和5D0→7F1的荧光强度比值更大。与Eu3+相似，Er3+在β-BiNbO4中具有更高的上转换荧光强度，其强度约是在α-BiNbO4中荧光的近40倍，说明三斜结构BiNbO4更适合做稀土离子的基质材料。