Preparation And SERS Performance Of Cu₂O Nanoparticles

urface-enhanced Raman Scattering?SERS?spectroscopy is a molecular detectiontechnique with advantages of low detection limit,lossless,high efficiency,and repeatability.The preparation of a good SERS substrate is the key to the development of SERS spectroscopy.A large number of studies have shown that using precious metals as SERS substrates can achieve ideal detection results.However,due to the high cost and poor biocompatibility of precious metal substrates,there is currently no general promotion and application.Therefore,in recent years,research hotspots for SERS substrates have gradually shifted from precious metals to cheaper,more biocompatible semiconductor materials.Cu₂O is a typical semiconductor material that can be excited by visible light and is widely used in photocatalysis,optoelectronics and other fields.At present,the SERS performance of Cu₂O has been studied and found that it can be used as a SERS substrate,and the morphology of Cu₂O will affect the SERS performance.In this paper,Cu₂O nanospheres with rough surface were synthesized by liquid-phase reduction method and used as SERS substrates to study its SERS performance.The details are as follows:Using CuCl₂ as a copper source and hydrazine hydrate as a reducing agent,Cu₂O nanoparticles was prepared without addition of surfactant.The test results show that the reaction product is pure Cu₂O,which shows a spherical structure formed by the aggregation of small particles.The average diameter of the sphere is?155±14.63?nm and the melting point is about 550 °C.According to the experimental results,the effects of different experimental parameters such as reaction time,mole ratio of hydrazine hydrate and CuCl₂,and concentration of CuCl₂ on the morphology of Cu₂O nanoparticles were studied.It is found that when the reaction time is 20 minutes,the molar ratio of hydrazine hydrate to CuCl₂ is 20 to 1,the concentration of CuCl₂ is 6 mmol/L,the reaction temperature is 20 °C,and the p H of CuCl₂ solution is 5,the Cu₂O nanospheres formed are relatively regular.The small particles that make up the sphere are small and uniform in size.In addition,when Na OH was added to adjust the p H of the CuCl₂ solution to 7 and 9,nano Cu₂O changed from spherical to octahedral.According to the experimental phenomena,the morphology of Cu₂O nanoparticles was explored.The growth mode of the Cu₂O nanospheres is the accumulation growth mode,and the nitrogen generated during the reaction promotes the formation of the sparse structure.The formation of octahedral Cu₂O is due to the increased alkalinity of the reaction solution afterthe addition of Na OH,which increases the reduction capacity of hydrazine hydrate,resulting in a higher degree of Cu+ supersaturation and the crystals tend to grow along the non-polar face,thus forming eight The faces are?111?octahedrons.Finally,rhodamine 6G?R6G?was selected as a probe molecule to test the SERS performance of Cu₂O nanospheres.After calculation,the Cu₂O nanoparticles substrate has an enhancement factor of approximately 3.6×103,exhibiting good SERS performance.The analysis shows that the SERS effect of Cu₂O nanoparticles substrate may be due to the adsorption of R6 G on the substrate and the resulting charge transfer.In addition,the porous globular structure of Cu₂O nanospheres provide more active sites,making the signal of R6 G molecules adsorbed on these active sites enhanced.