An Experimental Introduction to Colloidal Nanocrystals through InP and InP/ZnS Quantum Dots

Quantum dots are colloidal semiconductor nanocrystals that display size-dependent electronic and optical properties. These materials are a visual demonstration of a quantum-mechanical effect. Here we present a laboratory exercise for undergraduate/Bachelor students as an introduction to colloidal nanocrystals and quantum dots. The students synthesize three sizes of indium phosphide (InP) nanocrystals and perform one core/shell synthesis of indium phosphide cores shelled with zinc sulfide (InP/ZnS). The obtained quantum dots are characterized by quantitative UV–vis, photoluminescence, and 1H NMR spectroscopy. Students are acquainted with several concepts: nanocrystal synthesis, colloids, Beer–Lambert law, quantum confinement, photoluminescence, and surface chemistry. For each concept, background information is provided, rendering this report a comprehensive introduction for students and teachers. Indium phosphide is a safer material to handle in the undergraduate lab compared to cadmium selenide (CdSe), cesium lead bromide (CsPbBr3), or lead sulfide (PbS) nanocrystals.