The hand sprayer-based procedure starts with spraying Solution A to cover the entire surface of screen protectors, followed by another spraying of Solution B in the same manner. After a 15-min aging under ambient conditions without any heating step, the mixed solutions can be cleaned by water rinse washing or paper wiping until completely dry. Then, a highly transparent and almost invisible coating has been deposited on the substrates, as demonstrated in Figure . The transparency of the hand sprayer-coated screen protectors is almost identical to the uncoated ones (Figure ). The optical transmission spectra collected (Figure ) from the five different locations show nearly the same transmittance values, suggesting a highly uniform coverage over the entire top surface. The statistical values of transmittance at 550 nm are 99.74 ± 0.17%, just slightly lower than the uncoated ones. Moreover, all the metals incorporated are present on the coated surface, as analyzed via X-ray photoelectron spectroscopy (XPS, see Supporting Information, Figure ).