Preparation Of Cu₂O/Noble Metal Composite And Its Application In Detection/Degradation Of Pollutants

Cuprous oxide（Cu₂O）,as a narrow band gap（2.17 e V）semiconductor,has good response to visible light.Because of its low preparation cost,abundant adjustable morphologies and large scale preparation,Cu₂O has a great practical application prospect to be applied in the field of actual catalysis.However,the low carrier mobility of Cu₂O leads to a low catalytic efficiency.In addition,when single Cu₂O semiconductor acts as a surface enhanced Raman scattering（SERS）substrate,it has insufficient SERS enhancement ability.Noble metal nanoparticles have been the first choice for SERS substrates due to their strong local surface plasmon resonance（LSPR）effect.Therefore,Cu₂O/noble metal composites can realize the integration of SERS detection and catalytic degradation of dye pollutants,which have a broad application prospect.In this paper,Cu₂O based composites was proposed and designed,and noble metal Ag and Au were introduced.The composites were applied to degradation,rapid and efficient SERS detection of dye pollutants.In addition,to achieve the purpose of recycling,Fe₃O₄nanoparticles are also introduced into the composite system.The obtained main results include:（1）Au@Cu₂O nanocomposite（NC）catalysts with controllable shell thickness of Cu₂O were prepared.Ag nanoparticles were reduced on the surface of the Au@Cu₂O with the optimal performances to obtain ternary Au@Cu₂O-Ag NCs.The degradation effect of Au@Cu₂O-Ag NCs to methyl orange（MO）was investigated.The results showed that Au@Cu₂O-Ag NCs could rapidly catalyze the degradation of MO within 4 min in the presence of sodium borohydride（Na BH₄）,and the corresponding catalytic mechanism was analyzed.It was also proved that Au@Cu₂O-Ag NCs had good reusability and high stability.Therefore,the designed Au@Cu₂O-Ag NCs have great application potential in the rapid removal of organic dye pollutants.（2）Au@Cu₂O NCs were prepared and chosen as SERS substrates,and the substrates were optimized by adjusting the content of Ag nanoparticles.Finite difference time domain（FDTD）method was used to simulate the electromagnetic field enhancement of the substrates.At the same time,combining with the assignments of SERS signal for the reporter molecule,the SERS enhancement mechanism was analyzed.The limit of detection of malachite green（MG）was as low as 10^-9 M,and the corresponding linear relationship could provide a basis for the quantitative detection of MG.After 6 self-cleaning tests,the substrates were still able to detect MG at low concentration.The SERS substrates have high sensitivity,self-cleaning ability and good signal reproducibility,which greatly promote the development of green environmental protection testing technology and provide a new idea for the development of an integrated multi-functional platform for the detection and degradation of organic dyes.（3）The flower-like Fe₃O₄ was used to support rhombic dodecahedron Cu₂O-Ag to obtain a recyclable magnetic Fe₃O₄/Cu₂O-Ag multifunctional composites.Under visible light irradiation,the catalyst showed high photocatalytic activity for methylene blue（MB）.The results showed that the degradation rate of MB was still above 92.6%after the photocatalyst was put into 6 cycles.The optical properties and charge transfer ability of the samples were studied,and the photocatalytic mechanism was analyzed in detail.In addition,Fe₃O₄/Cu₂O-Ag was used as a SERS substrate for the detection of MB,and the detection limit of MB was as low as 10^-9 M.Meanwhile,the substrate showed a high degree of uniformity.The magnetic multifunctional composite opens up a new possibility for the integration of SERS detection and photodegradation of organic dyes.