For the synthesis of S@Ag54, 48.6 mg (0.22 mmol) of silver trifluoroacetate (Ag(TFA)) and 10.6 mg (0.044 mmol) of copper(II) nitrate trihydrate (Cu(NO3)2•3H2O) were dissolved in 4 mL of a mixture of acetone and acetonitrile (50/50 vol%). Then, 15 µL (0.13 mmol) of tert-butanethiol ( t BuSH) was added to this solution, and the resulting mixture was transferred into a glass tube (Figure ). A cap with a small hole (Figure ) was placed on the glass tube, and the tube was left undisturbed under a fluorescent lamp for light irradiation (Figure ). Orange crude crystals of S@Ag54 were obtained after approximately one week (Figure ). The crude crystals were dissolved in chloroform, and hexane was slowly added to the upper layer. The solution was left to stand for one month, resulting in the formation of single crystals of S@Ag54 (Figure ). I@Ag54 was synthesized in the same manner as S@Ag54, except 20 mg (0.054 mmol) of tetrabutylammonium iodide (TBAI), as well as t BuSH, was added to the acetone/acetonitrile mixture of Ag(TFA)/Cu(NO3)2. Red-orange crude crystals of I@Ag54 were obtained after approximately two weeks (Figure ). The crude crystals were dissolved in chloroform, and hexane was slowly added to the upper layer. The solution was left to stand for one month, resulting in the formation of single crystals of I@Ag54 (Figure ).