FT-IR spectra of the NPG-Silica microcapsules were measured to analyze their chemical composition. Figure 3 shows the FT-IR spectra of pure silica synthesized by the emulsion method, pure NPG, and the microcapsules comprising solid–solid PCM NPG encapsulated in a silica shell. The FT-IR spectrum of pure silica is characterized by the Si-O-Si linkage at 1070, 940, and 800 cm−1 and the broad band around 2850–3000 cm−1 due to the O-H stretch of silanol . The peaks in the spectrum of pure NPG correspond to the stretch of C-C, C-H, C-O, and O-H bonds. The spectrum of the microcapsules (i.e., curve c), has all the essential spectral characteristics of both NPG and silica, shown in curves a and b, respectively, providing evidence in support of NPG encapsulated by hydrated silica shells. The elemental composition of the as-synthesized microcapsules is further confirmed using the EDS images (see Fig. 4).