Photoresponsive Nanosheets of Polyoxometalates Formed by Controlled Self‐Assembly Pathways

Anionic Keggin polyoxometalates (POMs) and ether linkage‐enriched ammonium ions spontaneously self‐assemble into rectangular ultrathin nanosheets in aqueous media. The structural flexibility of the cation is essential to form oriented nanosheets; as demonstrated by single‐crystal X‐ray diffraction measurements. The difference in initial conditions exerts significant influence on selecting for self‐assembly pathways in the energy landscape. Photoillumination of the POM sheets in pure water causes dissolution of reduced POMs, which allowed site‐specific etching of nanosheets using laser scanning microscopy. By contrast, photoetching was suppressed in aqueous AgNO₃ and site‐selective deposition of silver nanoparticles occurred as a consequence of electron transfer from the photoreduced POMs to Ag⁺ ions on the nanosheet surface.