Synthesis of carbon nitride in a school lab

Does somebody remember an educative video from the Open University, in the United Kingdom, about Organic Synthesis, where a thin film of carbon nitride was synthesised from the separation surface of two not mixable liquids in a simple school-type laboratory?. Does somebody remember what those liquids were?. The thin film obtained had metalic bright, and it was told that carbon nitride is hardest than diamond. I'm talking about a very flexible material more resistent than diamond, able to be synthesised in a school lab.