In-situ evaluation of dye adsorption on TiO₂using QCM

Abstract

We measured the adsorption characteristics of two organic dyes; triphenylamine-cyanoacrylic acid (TPA-C) and phenoxazine (MP13), on TiO2, directly in a solution based on quartz crystal microbalance (QCM). Monitoring the adsorbed amount as a function of dye concentration and during rinsing allows determination of the equilibrium constant and distinction between chemisorbed and physisorbed dye. The measured equilibrium constants are 0.8 mM −1 for TPA-C and 2.4 mM −1 for MP13. X-ray photoelectron spectroscopy was used to compare dried chemisorbed layers of TPA-C prepared in solution with TPA-C layers prepared via vacuum sublimation; the two preparation methods render similar spectra except a small contribution of water residues (OH) on the solution prepared samples. Quantitative Nanomechanical Mapping Atomic Force Microscopy (QNM-AFM) shows that physisorbed TPA-C layers are easily removed by scanning the tip across the surface. Although not obvious in height images, adhesion images clearly demonstrate removal of the dye.

Interfacial Mass Diagnostics: Quantitative Perspective on Construction and Mechanism Understanding of Dye‐Sensitized, Perovskite and Quantum Dots Solar Cells

“…Besharat et al [39] studied the adsorption characteristics of triphenylamine cyanoacrylate (TPAÀ C) and phenoxazine (MP13) on TiO 2 . Through continuous adsorption and flushing of the flow cell and real-time monitoring of the functional relationship between adsorption capacity and dye concentration, the equilibrium constant and the difference between chemical adsorption and physical adsorption could be determined.…”

“…Besharat et al [39] . studied the adsorption characteristics of triphenylamine cyanoacrylate (TPA−C) and phenoxazine (MP13) on TiO 2 .…”