Research / 2021 / Article / Fig 4

Research Article

Simple Vanilla Derivatives for Long-Lived Room-Temperature Polymer Phosphorescence as Invisible Security Inks

Figure 4

1H NMR spectral studies. 1H NMR spectra of (a) M1, (b) M1-acid, (c) M2 and M2-acid, and (d) M3 and M3-acid-doped PVA films with different doping concentrations. On the left: vanilla structures with indicated protons and PVA structure with E proton. On the right: 1H NMR spectra showing the changes of proton peaks.