QCM Measurements. The resistive measurements were combined with gravimetric measurements of hybrid film-coated QCMs to determine the mass of sorbed water molecules. The measurements were performed using dry purified air as the ZG. The sensors were exposed to a range of r.h. from ∼0-80% using a combined saturator/humidifier system. The QCMs were contacted using wired sample holders. The baseline resonance frequency of the QCMs was recorded using an Agilent E5100A network analyzer for 100 s in a ZG atmosphere before film deposition, and after film deposition and illumination to estimate the mass of the sensing material. During the r.h. exposure, the resonance frequency of the QCM was continuously monitored using the network analyzer connected via GPIB and controlled by a python script to readout the (anti)resonance impedances and (anti)resonance frequencies.