Preparation And Properties Of Nano-Bi, Sn And Bi-Sn Alloys

Nanomaterials have been widely studied by researchers because of their excellent performance in biomedicine,new energy,photocatalysis,etc.Among metal nanomaterials,binary alloys have been improved due to their synergistic effect and the characteristic performance of two metal elements,which greatly expands the application range of nanoalloy materials.In this paper,nano-Bi,Sn and their alloy particles were prepared by reducing bismuth nitrate（Bi（NO₃）₃）and tin isooctanoate(C₁₆H₃₀O₄Sn₂)with sodium borohydride under the action of polyvinylpyrrolidone stabilizer.After that,the outer layer of the nanoparticles was coated with SiO₂ by wet chemical methods,their microstructure was characterized by X-ray diffraction（XRD）and transmission electron microscopy（TEM）,and the phase transition temperature of the nanoparticles was determined by differential scanning calorimetry（DSC）.Then,based on thermodynamic simulation and literature data,the surface tension,surface energy and surface segregation of Bi-Sn nanoalloys were calculated.Finally,based on the specific response of Bi to trace Cd²⁺and Pb²⁺,BiSn nanoalloy loading on carbon nanotubes was successfully used to detect the concentration of trace Cd²⁺and Pb²⁺in water,and very good results were achieved.The main research contents of this paper are as follows:（1）Based on chemical reduction method,nano-Bi,Sn and their alloy particles were prepared with Bi（NO₃）₃ and C₁₆H₃₀O₄Sn₂ as precursors,Na BH₄ as reducing agent,and polyvinylpyrrolidone as surface stabilizer.Combined with the St（?）ber method to coat SiO₂on the surface of nanoparticles by hydrolysis of tetraethyl orthosilicate to form nanoparticles with core-shell structure,the coating situation was characterized by XRD and TEA,and the phase transition temperature of nanoparticles was characterized by DSC,and the results showed that the liquid phase transition temperatures of nano Bi@SiO₂ and Sn@SiO₂appeared at 202.4°C,270.3°C,196.4°C and 231.3°C,respectively,corresponding to the melting points of the nanoparticles and blocks,respectively.The results show that the size of the nanoparticles is positively correlated with the melting point.（2）Based on the existing thermodynamic models and the thermodynamic data of literature research,the relationship between surface tension,surface energy and temperature and particle size of pure elements Bi and Sn nanoparticles,as well as the relationship between melting temperature and size of nanoparticles,were calculated.Based on the existing data,combined with the Liquid-drop model and Butler equation,the surface properties of the Bi-Sn binary alloy system were calculated,and the relationship between surface segregation,surface tension and surface energy with the change of alloy composition,temperature and size was obtained,and the calculation results showed that the surface energy of Bi was lower than that of Sn and therefore Bi had a tendency to be segregated on the surface.（3）BiSn nanoparticles were prepared by chemical reduction and loaded on carbon nanotubes（CNTs）for efficient detection of trace Cd²⁺and Pd²⁺sensors.The microstructure and electrochemical performance of BiSn nanoparticles were tested with XRD,TEM,cyclic voltammetry（CV）and electrochemical impedance spectroscopy（EIS）.Then,the performance of Cd²⁺and Pb²⁺was simultaneously detected by BiSn@CNTs and Nafion modified screen-printed electrodes（SPE）by square wave anode dissolution voltammetry SWASV.The results show that the Bi-Sn nanoparticles are well loaded on carbon nanotubes,and the BiSn@CNTs and Nafion modified screen-printed electrodes have good performance in detecting Cd²⁺and Pb²⁺in water at the same time,as well as excellent stability and reproducibility,which is attributed to the increase of the specific surface area of the electrode due to the modified nanomaterial.The sensitivities of the prepared sensors are 0.88 and 0.49μA/（μg/L）,and the detection limits are 0.37 and 0.11μg/L,respectively.And successfully used the sensor for the detection of water samples in real environments.