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

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 H-1 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. H-1 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.