Encapsulation of PCM in hollow nanoparticles with one or multiple holes in the wall. (A) Schematic illustration showing the encapsulation and release of PCM, anticancer drug (DOX) and NIR dye (ICG) in silica hollow nanoparticles with one hole in the wall. (B, C) TEM images of silica nanoparticles (B) before and (C) after loading with PCM and payloads. The success of loading PCM into the nanoparticles is manifested by the changes in contrast. (D) UV-vis spectrum of the resultant nanoparticles, confirming the successful loading of both DOX and ICG. (E, F) TEM images of AuNCs (E) before and (F) after loading with PCM and payloads. (G) UV-vis spectra of the resultant AuNCs, confirming the successful loading of R6G or MB. (A-D) Reproduced with permission.[54] Copyright 2019, Wiley-VCH. (E-G) Adapted with permission.[10] Copyright 2011, American Chemical Society.