Fabrication of Transparent Thin Film of Octahedral Molybdenum Metal Clusters by Electrophoretic Deposition

Abstract

Thin films of octahedral molybdenum metal clusters (Mo6) were fabricated on indium tin oxide (ITO) glass slides by the electrophoretic deposition (EPD) technique. The solubility of the Cs2Mo6Br14 cluster compounds, which are composed of [Mo6Bri8Bra6]2− units associated with two cesium cations, in different solvents was investigated in order to achieve a well-dispersed colloidal solution of the Mo6 cluster units that was stable during the following EPD process. Distilled water, ethanol, 1-propanol, acetone, methyl-ethyl ketone (MEK) and acetyl acetone were selected as the dispersing media of the Cs2Mo6Br14 cluster compounds. Homogeneous, transparent Mo6 cluster films with prominent luminescent properties were obtained by the EPD when dissolving Cs2Mo6Br14 into the MEK and acetyl acetone solutions. The obtained Mo6 cluster films were examined by investigating the thickness (color 3D laser spectroscopy), the morphology (FE-SEM), the Br/Mo ratio (XRF), and the crystallographic parameters variation (XRD). The optical emission properties were characterized by UV-Vis spectroscopy, FL spectroscopy and micro PL spectroscopy. The thickness of the Mo6 cluster films changed depending on the kind of the solvents. The atomic ratio of the Mo and Br elements in the Mo6 cluster-based unit were relatively maintained during the dispersion and deposition in the MEK solution. The UV-Vis absorption spectra exhibited a high transparency in the visible light range (500 – 850 nm) accompanied by many peaks due to light interference in the wavelength range from 400 nm to 2000 nm. The emission intensity of the Mo6 cluster film deposited in MEK slightly decreased during continuous irradiation of 325 nm laser light for 600s.