Synthesis of Copper(I) Oxide Particles with Variable Color: Demonstrating Size-Dependent Optical Properties for High School Students

We suggest the use of a simple and cheap synthesis of micro- and nanosized copper(I) oxide particles with variable color as a demonstration of size-dependent optical properties of semiconductors for high school students. The synthesis of Cu2O particles is performed by reducing alkaline copper(II)-citrate complex (Benedict's reagent) with glucose. Significant color and size changes of Cu2O particles at various reaction conditions are observed and discussed. Proposed demonstration is very useful for introducing students (including undergraduate students) to size-dependent optical properties of semiconductors and principles of synthesis of nanosized objects.