Thermally Hypsochromic or Bathochromic Emissions? The Silver Nuclei Does Matter

Structural modulation of core-shell silver nanoclusters from the inside is a huge challenge but of great importance in their syntheses. Herein, two silver nanoclusters [Ag3S9@Ag-42] (SD/Ag45b) and [Ag9S9@Ag-42] (SD/Ag51a) are isolated in the presence of different kinds of sulfonic acids. Uniquely, SD/Ag45b and SD/Ag51a show typical core-shell structures with the similar Ag-42 shell but different cores. The outer shell of 42 silver atoms comprises two Ag-3 trigons at two poles encircled by three equatorial distorted square cupolas (J(4), Ag-12). The core in SD/Ag45b is a silver trigon ligated by nine S2- ions (Ag3S9), while a tricapped triangular prismatic Ag-9 also ligated by the same amount of S2- ions (Ag9S9) is observed in the inner core of SD/Ag51a. The electrospray ionization mass spectrometry (ESI-MS) indicates that the introduction of p-toluenesulfonic acid can realize the transformation from SD/Ag45b to Ag-51. SD/Ag45b and SD/Ag51a show inverse luminescence thermochromic behaviors in the near-infrared (NIR) region, mainly dictated by the inner silver cores. This work not only realizes the synthesis of new silver nanoclusters by core modulation but also provides a prototype to get molecular-level insight into the correlation between structure and luminescence thermochromism.

Automated summary

This study successfully isolated two silver nanoclusters with core-shell structures under the presence of different sulfonic acids, showing different cores while sharing a similar outer shell. The nanoclusters exhibited inverse luminescence thermochromic behaviors in the near-infrared region, mainly controlled by the inner silver cores. This work not only achieved the synthesis of new silver nanoclusters through core modulation but also provided a prototype for understanding the correlation between structure and luminescence thermochromism at the molecular level.