Fabrication of Prussian Blue Nanoparticles

PBNPs were prepared as previously described [42 (link)]. Typically, 3.0 g polyvinyl pyrrolidone (PVP, Sigma, USA) was dissolved in 0.1 M HCl with a total volume of 40 ml, followed by the addition of 110 mg potassium hexacyanoferrate (III) (K₃[Fe(CN)₆], Sigma, USA) with agitation for 1 h. The mixed solution was then placed in a water bath (80 °C) for 20 h. Finally, PBNPs were harvested via centrifugation and repeated wash by MilliQ and ethanol. TEM (JEM-1400, Japan) was conducted to characterize the size and morphology of PBNPs. A dynamic light scattering (DLS) particle size analyzer (Malvern-2000, USA) was utilized to determine the hydrophilic diameter and zeta potential of PBNPs. The UV-vis spectra of PBNPs were acquired with a Hitachi U-3010 spectrometer.