The hydrophobic coating has been a promising technology for improving surface performance. The surface performance of magnesium alloy has been limited in application. Furthermore, the hydrophobic of magnesium alloy is rarely investigated because magnesium alloy is an active metal alloy. In this paper, inspired by microstructure character of typical plant leaf surface such as lotus, the biomimetic hydrophobic coatings on AZ91D magnesium alloy surface were prepared by means of wet-chemical combining electroless. The samples were immersed into AgNO3 solution in wet-chemical method firstly. Then, biomimetic hydrophobic coatings were prepared by electroless after wet-method pretreatment. The microstructure was observed by SEM and the contact angles were measured by contact angle tester. The results indicated that the biomimetic hydrophobic coatings with uniform crystalline and dense structure could be obtained on AZ91D magnesium alloy surface. The results of contact angle revealed that the biomimetic nano-composite coatings were hydrophobic. The wet-chemical method treatment on the AZ91D magnesium alloy substrate provided a rough microstructure, thus improving adhesion of the coating and the substrate.
To further understand the adsorption characteristics of different-type leaf surfaces adsorbing pesticide droplets and reveal the adsorption mechanism of pesticide droplets on non-smooth leaves,non-smooth leaves of 12 kinds of typical target plants were investigated in this study.The parameters of surface morphological characteristics were measured,which include contact angle between leaves and water droplets,water holding capacity surface tension,polar component,dispersion component and other quantitative range of indicators and variation by modern means.The relationships between the indicators and water holding capacity were investigated respectively.The experimental results show that the number of trichomes,epidermal wax,morphology and distribution characteristics have influences on adsorption characteristics of the water droplets.There is a negative correlation between free energy of obverse side and the water holding capacity(R=−0.447)while the free energy of reverse side and the water holding capacity show a positive correlation(R=0.212).Also,there is a negative correlation between polar component of obverse side and the water holding capacity(R=−0.357)while the polar component of reverse side and the water holding capacity in plant leaves show a positive correlation(R=0.149).The research can provide a scientific theory for reasonable spraying of pesticide in the agricultural production,and can be a reference for the development of pesticide adjuvants and bionic pesticides.
Wang ShujieWang HujunLi ChunZhong XiangmeiHuang HuiZhou Yajun
Plant leaf is a natural composite biomaterial, and its strength is closely related to the microstructure. In this paper, themechanical characteristics of eight species of plant leaves were investigated and analyzed. The ultimate strength of leaves andthe hardness of leaf surfaces were measured by using universal testing machine and nanoindenter tester, respectively. The tensilestrength of the parallel microstructure was investigated based on its cross-sectional mechanical model. The results of tensiontests indicate that the ultimate strength of a leaf is related to the material composition and structure. The coriaceous leavesusually exhibit higher tensile strength. For example, the Phyllostachys pubescens leaf can achieve the maximum ultimatestrength of 5.9091 N·mm-2. It is concluded from the results of hardness tests that material components of leaf surface caninfluence the surface hardness evidently. The leaf surface composed of more lignin and cellulose materials shows a highersurface hardness than that composed of more carbohydrates materials.
Shujie Wang, Luquan Ren, Yan Liu, Zhiwu Han, Yue Yang The Key Laboratory of Bionic Engineering (Ministry of Education, China), Jilin University, Changchun 130022, P. R. China
In the present work,we report a label-free fluorescence turn-on approach for the sensitive and selective sensing of Pb2?.Pyrene with one positive charge was used as the fluorescent probe,and thrombin aptamer(TBA),which was a G-rich oligonucleotide,was employed to form G-quadruplex with lead(II).When TBA and Pb2?were mixed with lead(II)in an aqueous solution,it was folded into a stable G-quadruplex.Subsequently,a single-stranded nucleic acid-specific nuclease S1 was added.The G-quadruplex stabilized by Pb2?lead(II)had markedly a significant resistant ability to nuclease S1 digestion.However,in the absence of Pb2?lead(II),no quadruplex or less stable quadruplex was formed and TBA was digested by nuclease S1 in 3 min under the optimized experimental conditions.Finally,pyrene probe was mixed with oligonucleotide in Pb2?lead(II).Electrostatic interactions between oligonucleotide(a polyanion)and the probe induced the aggregation of the probe,which in turn produced strong emission of the strong pyrene excimer emission.The intensity of the induced excimer emission was directly proportional to the amount of Pb2?added.Our approach shows good selectivity and sensitivity for the detection of Pb2?with a limit of detection limit as low as 800 nmol/L.
