A modified and simplified method for purification of gold nanoparticles

2 nm gold nanoparticles (AuNPs) have promising applications within drug and protein delivery, bioimaging, and biosensing. By performing ligand place-exchange reactions, AuNPs protected with alkanethiolate ligands can be functionalized to regulate their behaviors. In this reaction, a new ligand is incorporated by mixing a thiol with the AuNPs. To remove the excess new ligand as well as the displaced thiolate, dialysis has previously been the most widely used method. However, this purification method is time-consuming and fails to remove unwanted thiols completely. In this study, we describe a fast and efficient procedure to purify AuNP aqueous solution through liquid-liquid extraction using dichloromethane. • We demonstrate a facile way to purify AuNPs after ligand place-exchange reactions through liquid-liquid extraction. • Liquid-liquid extraction is a simple, inexpensive and efficient method for AuNP purification. • This protocol enables us to completely purify AuNPs in a few hours and can be used as a much quicker and more scaleable valid alternative to dialysis.