Highly-fluorescent extracts from Pterocarpus wood for Fe3+ ion detection.

At present, excessive Fe3+ in daily water has become a threat to human health. Among the conventional detection methods for Fe3+, fluorescent probes have been applied on a large scale due to their simplicity and efficiency. However, the currently available fluorescent probes are difficult to synthesize, costly and environmentally unfriendly, limiting their applications. In this work, a fluorescent extract of Pterocarpus wood was successfully obtained, and the structure of some coumarin-based molecules in this extract was determined by 2D-NMR. Subsequently, the intensity of this fluorescence was optimized using response surface methodology (RSM), resulting in a high-intensity fluorescent probe. The probe was sensitive to the concentrations of Fe3+ and MnO4-, and could efficiently detects Fe3+ in the range of 2.7 µM-8.0 µM, with LOD and LOQ reaching 1.06 µM and 3.20 µM, respectively. Moreover, based on the strong complexation property of EDTA on Fe3+, this work designed the "switch-on" fluorescent probes. The experiment shows that both static and dynamic quenching exist in this system. The mechanism of complexation and oxidation of fluorescent molecules by the quencher is interpreted in the quenching reaction. In addition, the fluorescent probe has a high yield and low cost, it also performs well in actual water sample tests. This method is expected to be developed as a new way on Fe3+ detection.

Induced Wood-Inorganic Composites in Standing Trees via Slow-Release Drip.

It is a novel idea to fabricate wood-inorganic composites by utilizing the transpiration of bionic trees to realize the self-assembly of inorganic precursors in wood formation. We selected a 10-year-old poplar and diffused the solvent or sol containing SiO2 precursor into the xylem via the slow-release drip method. In combination with the moisture in xylem, reactions such as hydrolysis, polycondensation and self-assembly were induced in order to form wood inorganic composites. It was found, through microscopic observation, that such inorganic substances were yellowish brown and widely existed in vessels, wood fibers and ray cells. For the new grown wood, the fiber-tissue ratio and cell wall thickness underwent an increase, while the vessel diameter and tissue ratio experienced a decline. Moreover, such change was related to the concentration of precursors. EDS analysis proved that the elemental composition of sediments in wood cells was C, O, Si, K and Ca. XPS confirmed that the newly formed wood contained silicon oxide, illustrating that the standing tree slow-release drip technology could induce wood to fabricate inorganic composites.