Suppressing the Agglomeration of ZnO Nanoparticles in Air by Doping with Lower Electronegativity Metallic Ions: Implications for Ag/ZnO Electrical Contact Composites

Due to the strong surface energy and polarity, ZnO nanoparticles are prone to adsorbing the OH groups dissociated from water in the air, leading to easy agglomeration and hence deteriorating the dispersion of ZnO in composites. In this work, it has been theoretically and experimentally demonstrated that doping with lower electronegativity metallic ions is an effective strategy to suppress the agglomeration of ZnO nanoparticles. By calculating the adsorption energies and electronic structures of OH/M-doped ZnO configurations (M = Li+, Cu2+, Al3+), it was found that metallic ion doping with a lower electronegativity (in comparison to that of the host Zn2+) can efficiently reduce the adsorption of OH groups on the ZnO surface due to the lower effective bond order of M–O bonds. Guided by the theoretical results, various M-doped ZnO nanoparticles (M = Li+, Cu2+, Al3+) were prepared and characterized by X-ray photoelectron spectroscopy and a laser particle sizer, which confirmed that the lower the electronegativity of dopants, the lower the OH groups’ adsorbed amounts and aggregate sizes of M-doped ZnO nanoparticles. This work provides a general avenue to design the composition of M-doped ZnO nanoparticles for suppressing agglomeration and enhance the dispersion of ZnO in composites.