Tunable Interparticle Connectivity in Gold Nanosphere Assemblies for Efficient Photoacoustic Conversion

Abstract Manipulating matter at the nanometer scale to create desired plasmonic nanostructures holds great promise in the field of biomedical photoacoustic (PA) imaging. This study demonstrates a strategy for regulating PA signal generation from anisotropic nanosized assemblies of gold nanospheres (Au NSs) by adjusting the interparticle connectivity between neighboring Au NSs. The interparticle connectivity is controlled by modulating the diameter and interparticle spacing of Au NSs in the nanoassemblies. The results indicate that nanoassemblies with semi‐connectivity, i.e., assemblies with a finite interparticle spacing shorter than the theoretical limit of repulsion between nearby Au NSs, exhibit 3.4‐fold and 2.4‐fold higher PA signals compared to nanoassemblies with no connectivity and full connectivity, respectively. Furthermore, due to the reduced diffusion of Au atoms, the semi‐connectivity Au nanoassemblies demonstrates a high photodamage threshold and, therefore, excellent photostability at fluences above the current American National Standards Institute limits. The exceptional photostability of the semi‐connectivity nanoassemblies highlights their potential to surpass conventional plasmonic contrast agents for continuing PA imaging. Collectively, the findings indicate that semi‐connected nanostructures are a promising option for reliable, high‐contrast PA imaging applications over multiple imaging sessions due to their strong PA signals and enhanced photostability.