Electrochemical Deposition Of Co/CdSe Multilayer Heterojunction Nanowires And Their Properties

Multilayer heterojunction nanowires exhibit excellent performance and are gaining increasing attention in applications such as magnetic,catalytic,biomedical,and electronic devices.In this paper,we used the method of AAO template assisted electrochemical deposition.After the CdSe deposition mechanism was explored by cyclic voltammetry,in the mixed solution of 0.2 mol/L CdSO4,1 mmol/L SeO2,0.25 mol/L dilute sulfuric acid and 0.25 mol/L Na2SO4,We deposited at-0.65 V,and the stoichiometric ratio of Cd and Se in the nanowires was close to 1: 1.In the solution of 1 mol/L CoSO4 and 40 g/L boric acid,We deposited at-1.1 V and obtained Co nanowires.Finally,we used a double-slot method to obtain a series of Co/CdSe multilayered heterojunction nanowires with different section length by controlling the deposition time in different solutions.The nanowires were characterized by SEM,EDS,XRD,UV-Vis,Raman and PL,respectively.We analyzed the morphology and structure of single-component CdSe,Co and Co / CdSe multilayered heterojunction nanowires.The SEM characterization showed that the nanowires were arranged in an orderly parallel,and the diameter of the nanowires is the same as the diameter of the template channel,abaut 200 nm,and multilayer nanowires showed alternating light and dark growth.The XRD characterization show that the single-component CdSe nanowires are cubic sphalerite structure,and the structure of CdSe in the multilayer nanowires is unchanged,but the structure of Co in the multilayer nanowires was changed from the the hexagonal structure to the face-centered cubic structure.,compared with the single-component Co nanowires.We also analyzed the optical properties of single-component CdSe,Co and Co/CdSe multilayered heterojunction nanowires.The UV-Vis characterization showed that the absorption peak of single-component Cdse was about 650 nm,Eg was 1.81 eV,and the Eg had a slight increase compared with the absorption band of the bulk CdSe.When the Co fragment is 25 nm and the CdSe fragment is above 65 nm,the resonance absorption peak appeared at about 650 nm,and the coupling effect appeared in the absorption spectrum,which is similar to the one-component CdSe peak shape.It shows that the CdSe fragment induces the free electrons of the Co fragment under the stimulation of light,actively involved in the optical coupling with the CdSe fragment seamless bridge;.When the CdSe fragment was 30 nm and the Co fragment was 50 nm,the optical coupling was also observed.When the Co fragment was above 150 nm,no resonance absorption peak was found,indicating that the presence of the Co fragment disturbed the optical coupling.Raman analysis found that 201.37 cm-1 is the first-order longitudinal optical(LO)phonon mode of CdSe,405.07 cm-1 is the second-order longitudinal optical(2LO)phonon mode of CdSe.due to the size effect and strain of the nanomaterials The frequency of the phonon of CdSe is decreased compared with the bulk CdSe and slight red shift compared with the one-component CdSe Raman spectrum.The emission of single-component CdSe nanowires and multilayered nanowires occurred blue shift resulted from the generation of internal stresses during deposition and the generation of tension during the PL test,as well as the banding effect and the quantum confinement effect.And in the Co/CdSe multilayered heterojunction nanowires,the blue shift was more obvious with the shortening of CdSe fragment length,and also with the increase of Co length,the luminescence intensity decreased and the half width became wider.