Junhua Chen,Manjia Chen,Hui Tong,Fei Wu,Yizhang Liu,Chengshuai Liu
A fluorescence biosensor was developed for the ultrasensitive detection of the available lead in soil samples by coupling with DNAzyme and hairpin DNA cyclic assembly. The biorecognition between lead and 8-17 DNAzyme will cleave the substrate strands (DNA2) and release the trigger DNA (T), which can be used to initiate the DNA assembly reactions among the hairpins (H1, H2, and H3). The formed Y-shaped sensing scaffold (H1-H2-H3) contains active Mg 2+ -DNAyzmes at three directions. In the presence of Mg 2+ , the BHQ and FAM modified H4 will be cleaved by the Mg 2+ -DNAyzme to generate a high fluorescence signal for lead monitoring. The linear range of the fluorescence biosensor is from 1 pM to 100 nM and the detection limit is 0.2 pM. The biosensor also exhibited high selectivity and the nontarget competing heavy metals did not interfere with the detection results. Compare with the traditional method (DTPA+ICP-MS) for the available lead detection, the relative error (Re) is in the range from −8.3 % to 9.5 %. The results indicated that our constructed fluorescence biosensor is robust, accurate, and reliable, and can be applied directly to the detection of the available lead in soil samples without complex extraction steps.
Dan Jiang,Huan Zhou,Shan Wan,Guang-Yi Cai,Ze-Hua Dong
A superhydrophobic composite coating was fabricated on AZ91 magnesium alloy by combining micro-arc oxidation (MAO) and cyclic assembly in phytic acid and Ce(NO 3 ) 3 solution. The influences of assembling cycles on surface morphology and wettability were characterized by scanning electron microscopy and atomic force microscopy . It showed that a micro-nano hierarchical structure was constructed after three cycles of assembly, resulting in a superhydrophobic surface with a contact angle of 159°. Compared with the direct cyclic assembly on bare Mg alloy, the prior MAO treatment could notably reduce the cracks caused by hydrogen evolution during assembling process, and the following assembling process could in return repair the porous defects of MAO layer. Electrochemical tests indicated that the superhydrophobic composite coating increased the corrosion resistance of Mg alloy by three orders of magnitude in 3.5 wt% NaCl solution. Furthermore, 72 h of electrochemical tests revealed that the composite coating could provide long-term corrosion protection for Mg alloy. It indicates that the combination of prior MAO and latter cyclic assembly will be a promising strategy to construct corrosion-resistant composite coating on Mg alloy substrate.
危险品化学品经营许可证（带存储）