Synthesis of low-temperature-processable and highly conductive Ag ink by a simple ligand modification: the role of adsorption energy

Abstract

Acetic acid (AA) has been employed to reduce the surface capping ligands of Ag nanoparticles (NPs) for the fabrication of low-temperature-processable and highly conductive Ag ink. The ligand reduction of the Ag NPs was achieved using a one-step method, in which oleylamine (OA)-capped Ag NPs were immersed in AA for different durations (1, 2, 3, 5 and 10 h). The weight of the total capping ligand was reduced from 12.1 wt% to 2.3 wt% by 10 h AA immersion. According to in situ transmission electron microscopy (TEM) and electrical resistivity, the ligand-reduced Ag NPs were cured at a much lower temperature (approximately 100 degrees C) and showed better electrical performance than OA-capped NPs under the same conditions. To investigate the reason for this enhancement of the electrical properties, we characterized the surface chemistry of the Ag NPs by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS), which revealed that the surface capping ligand was exchanged from the OA to the acetate ion. In addition, the adsorption energy of the ligand was increased by the ligand exchange, which was studied using density functional theory (DFT) calculations. DFT was effective in explaining the adsorption of each ligand on Ag NPs and indicated that the ligand can be exchanged by AA immersion.