Fig. 2: Freezing, lyophilization, and heating tests.

Photographs and UV–Vis spectra of AuNPs₁₅/No PEG (black), AuNPs₁₅/HO–PEG_3k–OH (blue), AuNPs₁₅/MeO–PEG_3k–OMe (green), AuNPs₁₅/HS–PEG_3k–OMe (orange), and AuNPs₁₅/c-PEG_3k (red). a Freezing test using a household refrigerator. From top to bottom, photographs before freezing, after freezing, after melting, and a UV–Vis spectrum after melting. b Lyophilization test using liquid N₂. From top to bottom, photographs before freezing, after lyophilization, after redispersion, and a UV–Vis spectrum after redispersion. The UV–Vis spectra before freezing and lyophilization are shown in Supplementary Fig. 6. c Heating test at 85 °C for 4 h. From top to bottom, photographs before and after heating and UV–Vis spectra before and after heating.