Novel closed-cycle reaction mode for totally green production of Cu1.8Se nanoparticles based on laser-generated Se colloidal solution

Abstract

Non-stoichiometric copper selenide (Cu2 – x Se, x = 0.18 ∼ 0.25) nanomaterials have attracted extensive attentions due to their excellent thermoelectric, optoelectronic and photocatalytic performances. However, efficient production of Cu2 – x Se nanoparticles (NPs) 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 selenium (Se) NPs in pulsed laser-generated Se colloidal solution. Consequently, we put forward firstly a closed-cycle reaction mode for totally green production of Cu1.8Se NPs 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 NPs to form SeO 3 2 − and Se2– ions and further produce Cu2 – x Se NPs, and the by-product SeO 3 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 °C, and then the stream of Cu1.8Se NPs 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 NPs in weakly acidic colloidal solution is limited between 1 nm and 50 nm. The laser irradiation duration shows negative correlation with the size of Se NPs and unobvious impact to the pH of the solution which both are essential to the high yield of Cu1.8Se NPs. 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 Cu2 – x Se nanomaterials.