# Synthesis of copper selenide

If I react selenium powder with copper chloride powder above the melting point of selenium (221 °C), will I end up with a chunk of copper selenide, with the chlorine given off as gas, or will I lose some or all of the Se as as selenium chloride gas?

• Sounds like a bad idea to me. Chlorine certainly won't go off without a fight. – Ivan Neretin Aug 16 '19 at 19:49
• And selenium compounds can be very foul smelling. The smell also persists for a long time. – Ed V Aug 16 '19 at 20:08
• The eutectic in the Cl-Se binary system is at -52C (yeah, surprised me too). All copper-selenium phases have melting points above that of selenium, the most selenium rich are stable in contact with liquid selenium making it hard to predict what would happen. – Jon Custer Aug 16 '19 at 20:22

## 1 Answer

There are many ways to synthesize copper selenide. It generally has two forms $$\ce{Cu2Se}$$ and $$\ce{CuSe}$$ but actually it is a non-stoichiometric compound. They are grown as nanoparticles for various applications like making semiconductor, optoelectronic components, sensors etc.

1. By direct combination of copper and selenium vapour / direct displacement of cupric salts with hydrogen selenide.(1)(2)
2. Using copper(II) chloride dihydrate ($$\ce{CuCl2.2H2O}$$) and sodium selenite ($$\ce{Na2SeO3}$$) in ternary oil-in-water (o/w) emulsion system. The reducing agent, sodium borohydride ($$\ce{NaBH4}$$) used to reduce sodium selenite source at room temperature(3)
3. Using thiol ligands(4)
4. Using copper acetate dihydrate and hydrazine hydrate(5)

As for your reaction, chlorine will not get displaced that easily. It needs a counter ion for chloride to make bond. That's why instead of just selenium, hydrogen selenide is used. It can be better if any displacement is avoided and just direct combination of elemenys is done. See method 1.

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