Heterogeneous Scattering Solvatochromism in Single\nPrussian Blue Nanoparticles

Abstract

Solvatochromism\nprovides many opportunities for various applications,\nranging from chemical imaging to chemical sensing. However, a solvatochromic\nstudy is restricted to observe the change in the absorption or fluorescence\nspectroscopy on the basis of ensemble analysis. Herein, we image the\ninteraction between single Prussian blue nanoparticles (PBNPs) and\nsolvents with dark-field microscopy. Surprisingly, the scattering\ncolor and spectra of PBNPs are found to be sensitive to solvent polarity,\nshowing the first scattering solvatochromism phenomenon. The scattering\nsolvatochromic property of PBNPs is found to be highly recyclable\nand size-dependent. Single-nanoparticle imaging reveals a heterogeneous\nscattering solvatochromism among individual PBNPs. Additionally, we\npropose an explanation for this scattering solvatochromism, in which\nthe energy of the excited state is not changed, while the ground-state\nenergy successively decreases with the increase in the solvent polarity\ndue to the coordination interaction between PBNPs and solvents. The\nenergy difference between the ground state and the excited state rises,\nleading to the blue shift of the scattering peak. These findings offer\ninsights into fundamental photochemistry of nanoparticles, paving\nthe way to design and prepare scattering solvatochromic nanoprobes.