Controlling pH-Dependent Nanozyme Activity by Metal Identity in Histidine-Based Nanoarchitectures.

In this paper, we report a metal-driven structural tuning strategy with the L-histidine (His) ligand to modulate peroxidase-like nanozyme performance. Although the His coordinates with gold(III) ions to form an extended helical coordination polymer, its interaction with Cu(II) ions results in quantum-confined, ultrasmall nanoclusters. Based on the optical, structural, and surface analysis, the blue-emitting cores are stabilized by His ligands through imidazole nitrogen coordination, consistent with a Cu-centered coordination environment involved in the observed catalytic activity. According to the catalytic measurements, the His-Cu clusters outperformed the His-Au coordination polymer reference system. Steady-state kinetic modeling and 3D profiling revealed a pronounced shift in the pH optimum: low-valent Cu-containing His-Cu NCs enable efficient peroxide-dependent catalysis under nearly neutral conditions (pH 7.4), whereas His-Au CP exhibits its maximum activity under acidic conditions. Based on these findings, this work highlights nanoscale engineering for tailor-made biomimetic applications.