Synthesis, Formation Mechanism And Optical Properies Investigation Of Pb_xM_yTe_z(M=Cu,Sb) Nanocrystals

Lead telluride(PbTe), due to its narrow band gaps(~0.32eV) and face-centered cubic crystal structure, has been applied widely in a number of field such as photovoltaics, IR photoelecrics and thermoelectrics. Recently, the researching for PbTe-based nanomaterials has been attracted more and more attention while study for based bulk materials have gained great achievement. Compared with corresponding bulk compound, nanomaterials with special sizes and structures performs greater phonics, thermotics, optics and electrics characters so that researchers over the world focus on them.Doping foreign metal ions into cubic host matrix to synthesis ternary Pb Te based materials becomes robust route way to enhance the characters of PbTe based material. However, there have not been many success in the multinary PbTe-based nanocrystals due to the ―self-purification‖ mechanism. Therefore, finding an effective method to prepare uniform multinary solid soulution nanocrystals with different shapes and new nanoscale phases has been a huge challenge. Generally, the characters of nanocrystals were mostly determined by their morphology, due to their unique structure. Therefore, controlling synthesis for nanocrystals becomes the key to gained target products. Self-sacrifice Template synthesis could be the best choice to the controlling synthesis of nanocrystal for its stable skeleton.Herein, we first synthesized the new stable phase of ternary PbxMyTez(M=Sb, Cu) one-dimensional(1D) nanorods with rough surface, using Te as a self-sacrificial template. The introducing of EDTA can avoid ―self-purification‖ causing a decrease of solubility of dopant impurities in nanocrytals and even phase separation due to the smaller distance impurity travel to reach the surface or higher formation energy for nanocrystal than the bulk materials. X-ray diffraction technique(XRD), field emission scanning electron microscope(FE-SEM) and energy-dispersive spectroscopy(EDS), X-ray photoelectron spectroscopy(XPS) analysis have been used to characterize and determine the structure and composition of the product. By carefully adjusting the experimental conditions, it was found that reaction factors, including distinct solvent, the amount of alkali, reaction temperature, the ratio of reactants and growth time, play critical roles in the crystallization process of PbxMyTez(M=Sb, Cu) one-dimensional(1D) nanorods. Furthermore, the optical band gaps(Eg) of PbxMyTez(M=Sb, Cu) one-dimensional(1D) nanorods were investigated as well. The bamboo-like nanocrystals can be gained only synthesized in ethylene glycol(EG) at 180℃ for 5.5 h in two-step method. The Eg of PbxMyTez(M=Sb, Cu) tend to increase as the amount of doping agent increasing, in which 0.316 eV, 0.341 eV 0.375 eV were for PbmSb2 n Tem+3n nanocrystals and 0.298 and 0.305 eV were for PbmCunTem+n nanorods.Reaction with excess Pb produces PbxMyTez(M=Sb, Cu) one-dimensional(1D) nanorods having sizes variations, whereas the initial morphology of Te nanorod template with rough surface was preserved in the present of M source. The Pb2+/Mn+ synergistic effect was attributed to the difference of their reaction reactivity. In this study, besides PbxMyTez(M=Sb, Cu) one-dimensional(1D) nanorods experimental, template synthesis, parameters influenced and ionic synergistic effect involved into such route can support wider field for the controlling synthesis of another nanocrystal.