Elaborate chemical synthesis methods allow the production of various types of inorganic nanocrystals (NCs) with uniform shape and size distributions. Then, how can we synthesize NCs with thermodynamically metastable phases or very complex structures? The transformation of already-synthesized NCs via elemental substitutions, such as ion exchange reactions for ionic NCs [1,2] and galvanic replacement reactions for metal NCs [3], can overcome the difficulties facing conventional one-step syntheses. In particular, NC ion exchange reactions have been studied with numerous combinations of foreign ions and ionic NCs with various shapes. The functionality of the resulting ionic NCs, including semiconducting and plasmonic properties, can be easily tuned in a wide range, from the visible to near-infrared. Here we focus on the full and partial ion exchange reactions involving ionic NCs, highlighting important aspects such as the preservation of appearance and dimensions [4,5]. Finally, visible-to-near infrared light energy conversion systems using partially exchanged ionic NCs are provided [6,7].

[1] Saruyama, M.; Sato, R.; Teranishi, T. Acc. Chem. Res. 2021, 54, 765.

[2] Saruyama, M.; Teranishi, T. et al., J. Am. Chem. Soc. 2011, 133, 17598.

[3] Sato, R.; Teranishi, T. et al., to be submitted.

[4] Wu, H.-L.; Teranishi, T. et al., Science 2016, 351, 1306.

[5] Li, Z.; Saruyama, M.; Asaka, T.; Tatetsu, Y.; Teranishi, T. Science 2021, 373, 332.

[6] Lian, Z.; Teranishi, T. et al., Nat. Commun. 2018, 9, 2314.

[7] Lian, Z.; Teranishi, T. et al., J. Am. Chem. Soc. 2019, 141, 2446.