Synthesis And SERS Properties Investigation Of Nano-micro Structure Of Cu₂O/Ag

The lack of notable metal Surface-enhanced Raman scattering (SERS) substratelimits the breadth of practical applications. In this work, we had a study about Cu2Osemiconductor, Ag nanoparticle and Ag-Cu2O composite composite structure SERSsubstrate, which has an important and significance. The study enrichs the kinds ofthe SERS substrates, and also widen the application of SERS technique. The mainresearch works are listed as following:1. We reported a simple solution-phase route for synthesis of Cu2O crystals withdifferent morphologies at temperature of80℃. In our system, the morphologicalevolution of Cu2O crystals has been investigated by using different amounts ofsodium citrate and sodium carbonate mixed solution, and then Cu2O nanoframes areobtained in relatively shorter time by stirring the resulting solution in air for about12hours at room temperature. The condition/theory for synthesis of Cu2O nanoframesand nanocages in our previous work is supplemented. Finally, the morphologicalevolution and the growth mechanism are also explored.2. Uniform silver hollow nanoparticles assembled by nanosheets have beensynthesized by using Cu2O as chemical template at room temperature. It was foundthat the concentrations of acid were critical to the formation of perfect nanosheetassembled hollow silver nanoparticles. In the reaction system, the Ag+ions werereduced by Cu+ions released from Cu2O template. When the concentration of acidincreased to2mM, the Cu2O template dissolved completely, and perfect nanosheetassembled hollow silver nanoparticles were generated. The hollow silvernanoparticles show the optimum SERS properties with an enhancement factor of3.3×104. The relative standard deviation (RSD) of Raman intensity is lower than9.6%, which are important for practical assays. The reasons for the enhancement of theSERS performance are investigated in detail.3. Ag-Cu2O composite microstructures (Ag-Cu2O CMSs) and hollow Cu2O/Agcomposite nanoframes (Cu2O/Ag CNFs) with tunable silver content have beensynthesized by directly deposited Ag onto Cu2O truncated octahedra/Cu2Onanoframes. Ag contents on the surface of Cu2O can be tuned through the variation ofthe concentration of AgNO3. When0.40mM AgNO3is used, Ag are uniformly andcompactly coated on Cu2O, and the effective coverage area of Ag on Cu2O isenhanced significantly.4. When0.40mM AgNO3is used, the prepared Ag-Cu2O CMSs and Cu2O/AgCNFs show significantly improved SERS properties. Ag-Cu2O CMSs with anenhancement factor is7.8×104, the value of RSD for the sample is lower than9.3%;Cu2O/Ag CNFs with an enhancement factor is1.8×105, the value of RSD for thesample is lower than2.88%. Cu2O/Ag CNFs exhibit higher SERS signals thanAg-Cu2O CMSs, and then pure Ag.5. The Cu2O/Ag (2) CNFs exhibits the highest SERS performance, this may bedue to (1) more Raman hot spots are introduced not only due to the Ag hot spots butalso the hot spots formed at the interface between Ag NPs and the Cu2O.(2) Underthe irradiation of a suitable laser, Cu2O/Ag CNFs cause charge transfer from Ag NPsto Cu2O nanoframes, which induce a larger electromagnetic field, except that A largeelectromagnetic field caused by localized surface plasmon resonance (LSPR) inducedby metal Ag. The adsorbed RB molecules are located in two part of enhancedelectromagnetic field and consequently exhibit a stronger Raman signal.