Extraction and Application of Natural Rutin From Sophora japonica to Prepare the Novel Fluorescent Sensor for Detection of Copper Ions

Rutin (R), a representative flavonoid found in various biomasses, can be used to prepare different fluorescent sensors for environmental, biological and medical fields. In this work, the natural R in Sophora japonica was extracted and purified to prepare fluorescent-responding sensor systems intended to recognize copper ions with both strong selectivity as well as appropriate sensitivity. Results showed that neat R had no obvious fluorescent emission peak in PBS buffer solution. However, when R and (2-hydroxypropyl)-β-cyclodextrin (CD) were introduced within buffer solution, fluorescent emission intensity was significantly increased due to the resultant R-CD inclusion complex. In addition, the formed R-CD inclusion complex was shown to behave as the aforementioned fluorescent sensor for copper ions through a mechanism of quenched fluorescent emission intensity when R-CD became bound with copper ions. The binding constant value for R-CD with copper ions was 1.33 × 106, allowing for quantification of copper ions between the concentration range of 1.0 × 10–7–4.2 × 10–6mol⋅L–1. Furthermore, the minimum detection limit was found to be 3.5 × 10–8mol⋅L–1. This work showed the prepared R-CD inclusion complex was both highly selective and strongly sensitive toward copper ions, indicating that this system could be applied into various fields where copper ions are of concern.

The presence of mixed-valent silver in the uranyl phenylenediphosphonate framework

A 2-D silver uranyl phosphonate presents both Ag+ and Ag0 atoms in the free space between the adjacent layers and the incorporation of the mixed-valent silver sites results in the quenching of the fluorescent emission.