Preparation Of Nanosized γ-CuI Via Microreactor And Its Optical Properties

Recently,γ-CuI has been of particular interest due to its wide band gap Eg=3.1 eV,stable p-type conductivity at room temperature and fast ionic conductivity at high temperature.Nanosizedγ-CuI exhibits superior performance,especially as a photocatalyst.The synthesis of nanomaterials using the microchannel strategy is often employed due to its superior high mass and heat transfer efficiency,instantaneous adjustment ability,and a small scale-up effect.In general,microchannel synthesis strategy can effectively control the particle size of nanomaterials.However,the microchannel is prone to blockage by the particles produced,which hampers development and application in the nanopowder synthesis industry.Herein,KI and Cu²⁺were used as raw materials in the preparation of nanosized γ-CuI via a microchannel synthesis route.We found that selecting hydrazine hydrate as the reducing agent greatly improved the reaction efficiency by effectively controlling the pH of the system.The production of N₂ in the hydrazine hydrate reduction reaction generated a gas-liquid segmentation flow in the microchannel,which effectively alleviated the blockage issue in the microchannel.γ-CuI nanoparticles were successfully prepared in a stable and continuously high yield by microchannel synthesis route,with considerably smaller particle size compared to traditional precipitation methods.Based on the thermodynamic calculation of the γ-CuI reaction of hydrazine hydrate reduction by HSC chemistry software,the nucleation process of γ-CuI was analyzed.The mixing strength of micro-sieve microreactor was tested by Villermaux/Dushman chemical probe method.XRD,FT-IR,XPS,TEM,SEM and EDS were employed to study the preparation conditions of γ-CuI using copper salt and potassium iodide as raw materials,KOH or ammonia as the pH adjuster and hydrazine hydrate as reducing agent.The effects on the crystal phase,yield particle size and morphology of the sample were investigated.The optical properties ofγ-CuI prepared under different synthesis conditions were investigated.As the feed flow rate increases,the mixing strength of the micro-sieve microreactor gradually increases.When the feed flow rate is 20 mL/min,the microreactor mixing intensity is optimized.The optimum conditions for the continuous preparation of nanosized γ-CuI by microreaction method are:KOH addition amount 0.5,residence time 5s,reaction temperature20℃,feed flow rate 20mL/min,reactant concentration 0.5mol/L;The type of synthetic sample is cubic crystal γ-CuI with 99.86%yield,51 nm average particle diameter,and uniform particle size distribution.N₂ is produced during the reaction process using hydrazine hydrate as a reducing agent to form a gas-liquid split flow.The microreactor is continuously operated for more than 1000 min without clogging phenomenon;the conventional liquid phase precipitation method synthesizes γ-CuI average particle size is 418 nm and inhomogeneous,which is significantly larger than the γ-CuI particle size prepared by the microreaction method.Ammonia water has a complexation effect,and the morphology of γ-CuI is continuously controlled in the microreactor by the complexation of ammonia water.When ammonia water is used as pH adjuster and complexing agent,the type of copper source,reaction temperature,residence time in the tube and the amount of surfactant added have an effect on the morphology of γ-CuI.When the amount of ammonia added is 0.4,the copper source is copper acetate,the reaction temperature is 20℃,the residence time in the tube is 10 s,and the amount of surfactant CTAB added is 1%,the rod-shaped γ-CuI is continuously prepared.Under the same conditions,the γ-CuI nanorods were synthesized by microreaction method,while the γ-CuI synthesized by the traditional liquid precipitation method was mainly bulky.The morphology and particle size of γ-CuI have influence on its optical properties.The UV-vis diffuse reflectance spectrum of the nano-scale spherical γ-CuI prepared by microreaction method has higher absorption intensity in the ultraviolet wavelength range than the bulk γ-CuI prepared by the traditional liquid precipitation method,and the fluorescence intensity is smaller than that γ-CuI prepared by the traditional liquid precipitation method.The absorption value of the rod-like γ-CuI is between the spherical and bulky γ-CuI.The UV-vis diffuse reflectance spectrum of nano-scale γ-CuI has the strongest absorption value and the weakest fluorescence intensity in the ultraviolet wavelength region.As the particle size of γ-CuI decreases,the photocatalytic ability to degrade methylene blue is enhanced,and the degradation ability of nano-sized γ-CuI is the strongest.