Study On Green Synthesis Of Selenium Colloid And Nano Copper Selenide Based On Laser Irradiation In Liquid

After years of research and development,the application of nano materials has had a wide and profound impact in many fields.The research on the preparation of nano materials has attracted the attention of many scientific researchers.Among these preparation methods,laser irradiation in liquid technology plays an important role in the synthesis of nano materials because of its unique advantages such as fast and"green".Based on the technology,this research makes an in-depth study on the preparation of selenium colloid and the size regulation of selenium nanoparticles.Through the calculation of the relationship between the injected laser energy and the temperature and quantity of selenium nanoparticles,the reason for the shape and size change of selenium nanoparticles induced by laser is revealed.On this basis,the prepared selenium colloid was fully characterized and analyzed,and its application as a precursor for green and convenient synthesis of Cu_2-xSe nanoparticles was explored.Through contact with commercial copper,a series of closed-loop reactions can be carried out spontaneously,and the large-scale preparation of nano Cu_2-xSe particles was realized in a mild,efficient and environmentally friendly way.In addition,we also characterized and analyzed the photothermal and antibacterial properties of the obtained Cu_2-xSe nanoparticles,and explored its application potential as an inorganic nano bifunctional antibacterial agent.The main research contents and achievements of this paper are as follows:（Ⅰ）A uniform and stable selenium colloid was successfully obtained by laser irradiation of selenium powder dispersed in deionized water.The average particle size of selenium nanoparticles in selenium colloid can also be controlled by controlling the energy and irradiation time of incident laser and the mass concentration of selenium powder suspension.Moreover,the reasons for the shape change and size reduction of selenium nanoparticles induced by laser were explored and explained.We found that on the premise of determining the concentration of selenium colloid,the energy of incident laser and irradiation time have a direct impact on the size of selenium nanoparticles in colloid.Specifically,when the laser energy is able to affect selenium particles,the size of selenium nanoparticles will gradually decrease and finally stabilize with the extension of irradiation time.The final diameter of selenium particles is related to the incident laser energy.The higher the energy is,the smaller the final diameter is.However,there is also a threshold diameter for the reduction of particle size.This is because the heating effect of laser on selenium particles enables the instantaneous temperature of selenium particles to reach its melting/boiling point,resulting in melting remodeling and photothermal evaporation of particles.The evaporation-deposition dynamic equilibrium in colloid determines that the diameter of particles will not decrease indefinitely.（Ⅱ）Non-stoichiometric Cu_2-xSe nanomaterials have attracted extensive attentions due to their excellent thermoelectric,optoelectronic and photocatalytic performances.However,efficient production of Cu_2-xSe nanoparticles through a green and convenient way is still hindered by the inevitable non-environmentally friendly operations in common chemical synthesis.Herein,we initially reveal the coexistence of seleninic acid content and elemental Se nanoparticles in pulsed laser generated selenium colloidal solution.Consequently,we put forward firstly a closed-cycle reaction mode for totally green production of Cu_1.8Se nanoparticles to exclude traditional requirements of high temperature and toxic precursors by using Se colloidal solution.In such closed-cycle reaction,seleninic acid works as the initiator to oxidize copper sheet to release cuprous ions which can catalyze the disproportion of Se nanoparticles to form Se O₃^2-and Se^2-ions and further produce Cu_2-xSe nanoparticles,and the by-product Se O₃^2-ions promote subsequent formation of cuprous from the excessive Cu sheet.In experiments,the adequate copper（Cu）sheet was simply dipped into such Se colloidal solution at 70℃,and then the stream of Cu_2-xSe nanoparticles could be produced until the exhaustion of selenium source.The conversion rate of Se element reaches to more than 75%when the size of Se nanoparticles in weakly acidic colloidal solution is limited between 1 and 50 nm.The laser irradiation duration shows negative correlation with the size of Se nanoparticles and unobvious impact to the p H of the solution which both are essential to the high yield of Cu_2-xSe nanoparticles.Before Cu sheet is exhausted,Se colloidal solution can be successively added without influences to the product quality and the Se conversion rate.Such green methodology positively showcases a brand-new and potential strategy for mass production of Cu_2-xSe nanomaterials.