Tuning pencil lead light absorption/ reflective frequencies using plasma, for cheaper, eco-friendly optical materials

https://phys.org/news/2024-08-repurposing-pencil-optical-material-plasma.html

"various structural colors/ invisible characters only seen using IR camera... thin-layer interference between clay and graphite, the components of pencil lead... irradiating pencil lead with plasma, an electrically charged gaseous state, for extended periods of time resulted in optics causing interference in near/ mid-IR due to larger thickness of clay layer exposed by plasma etching... eco-friendly, cheaper: sensing, OLED displays, telecommunications, cancer treatment, new/ sustainable printing technologies"