Anchor Groups Effect on Spectroscopic and Electrochemical Properties of Quaternary Nanocrystals Cu–In–Zn–S Capped with Arylamine Derivatives

Abstract

A two-step procedure is reported enabling preparation of quaternary Cu–In–Zn–S nanocrystals with electrochemically active ligands consisting of 4-dodecylphenylaminobenzene and amine, thiol, or carboxylic anchor groups. Detailed 1H NMR and IR studies of nanocrystals dispersion as well as free ligands recovered via nanocrystals dissolution indicate that in the organic shell of initial ligands weakly (1-octadecene (ODE)) and more strongly (1-dodecanethiol (DDT) and oleylamine (OLA)) bound ligands coexist. Treating the nanocrystals with pyridine removes weakly bound ligands; however, DDT and OLA molecules remain present as coligands with pyridine. Labile pyridine ligands can then be exchanged for the target 4-dodecylphenylaminobenzene derivatives with different anchor groups. 1H NMR lines of these ligands are broadened due to their restricted rotation; this broadening is especially pronounced for the lines corresponding to the anchor group protons. Electrochemical activity of the ligands is significantly altered after their binding to the nanocrystal surface. Strongly interacting anchor groups such as −Ph–SH or −Ph–CH2NH2 lose their electrochemical activity upon coordination to nanocrystals, and weakly interacting groups (−PhNH2) retain it. Secondary amine −Ph–NH–Ph– remains electrochemically active in all nanocrystals capped with the studied ligands; however, the potential of its oxidation depends on the conjugation with the anchor group.