Synthesis And Optical Properties Of Core/Shell Structures Of X（x=Cu₂O,Ag）@Y（Y=Cu₂O,Cu） Nanoparticles

In resent years, much attention has been paid to structure controllablenanoparticles (NPs) for morphologies of NPs have important effect on both physicaland chemical properties, which will have new potential applications. Among variousmorphologies, core-shell NPs are very significant because of their unique architecture,various properties and enhanced activity. Core-shell hybrid NPs represent animportant class of multicomponent heterostructured nanosystems that may exhibit notonly a combination of properties from individual components but also, moreinterestingly, further enhanced tunability and even new synergistic properties thatarise from the nanoscale interactions between the disparate core and shellcomponents.Because of presence of localized surface plasmon resonance(LSPR) in noblemetal Ag, Ag is often used as core in metal-semiconductor core-shell NPs. The localelectromagnetic field of the LSPR can penetrate the shell, which can be used to tunethe center wavelength of the LSPR by changing the shell thickness on the nanometerscale.Cu and its oxides are low cost and multifunction materials, which have attractedgreat interest due to their excellent performance in the field of electronics,photovoltaics, catalysis, superconductivity, magnetic storage, electrochemistry andsensing.In this paper, chemical synthesis method in liquid phase was dopted to synthesisAg and Cu2O nanoparticles (NPs). Ascorbic acid was as reducing agent andpolyvinylpyrrolidone (PVP) as coating agent. Mophology controllable spherical Agnanoparticles were synthesized. The influence about PH value of the reactant systemand amount of coating agent on the size, morphology and dispersity of Ag NPs wasprobed. The preparation conditions of cube Cu2O NPs was investigated and theformation mechanism of cubic Cu2O NPs was explained. In alkaline condition, spherical Ag and cube Cu2O NPs were as nuclear NPsrespectively, Ag@Cu2O and Cu2O@Cu2O core-shell NPs were fabricated. Theinfluence factors to the core-shell NPs were investigated. By controling thethicknesses of the shells, the optical property of Ag@Cu2O NPs is tunable.In the fabrication process of Ag@Cu2O and Cu2O@Cu2O NPs, when thereductant is excessive, Cu2O shells were found to transfer into Cu shells, Ag@Cu2Oand Cu2O@Cu2O NPs can be easily converted to Ag@Cu and Cu2O@Cu NPs inair at room temperature with the help of surfactant and reducing agent, which is aunique phenomenon. A qualitative explaination was proposed for this conversion. Bycontroling the thicknesses of the shells, the optical property of Ag@Cu2O and Cu2O@Cu NPs is tunable.The properties of the NPs synthesized above were characterized by transmissionelectron microscope (TEM), X-ray diffraction (XRD) and ultraviolet absorptionspectroscopy (UV-VIS).The fabrication methods about NPs in this paper are benefit to other NPs andcore-shell. The Ag@Cu2O and Cu2O@Cu NPs show significant surface plasmonresontant effects, which will be promising to be used in photocatalytic, optical devicesand biomedicine or sensors.