Heterogeneous Scattering Solvatochromism in Single Prussian Blue Nanoparticles

Abstract

Solvatochromism provides many opportunities for various applications, ranging from chemical imaging to chemical sensing. However, a solvatochromic study is restricted to observe the change in the absorption or fluorescence spectroscopy on the basis of ensemble analysis. Herein, we image the interaction between single Prussian blue nanoparticles (PBNPs) and solvents with dark-field microscopy. Surprisingly, the scattering color and spectra of PBNPs are found to be sensitive to solvent polarity, showing the first scattering solvatochromism phenomenon. The scattering solvatochromic property of PBNPs is found to be highly recyclable and size-dependent. Single-nanoparticle imaging reveals a heterogeneous scattering solvatochromism among individual PBNPs. Additionally, we propose an explanation for this scattering solvatochromism, in which the energy of the excited state is not changed, while the ground-state energy successively decreases with the increase in the solvent polarity due to the coordination interaction between PBNPs and solvents. The energy difference between the ground state and the excited state rises, leading to the blue shift of the scattering peak. These findings offer insights into fundamental photochemistry of nanoparticles, paving the way to design and prepare scattering solvatochromic nanoprobes.