(250b) Controlled Synthesis of Krogmann's Salt Nanowires on Gold Nanoparticle Seeds for Sensor Applications

This study focuses on the fabrication of hybrid nanostructures using gold nanoparticles (AuNPs) as nucleation seeds in order to control the crystallization of partially oxidized potassium tetracyanoplatinate, also known as Krogmann’s salt. The nanocrystals of the Krogmann’s salt were synthesized using electrochemical method with the aim to have more control over the size and shape based on seed-mediated nucleation. The AuNP seeds were prepared on the highly oriented pyrolytic graphite (HOPG) substrate by electrocrystallization method. Aqueous solutions of 0.05 to 1 mM hydrogen tetrachloroaurate (HAuCl₄) with 0.1 mM potassium chloride (KCl) as the supporting electrolyte were prepared. The electrodeposition of the AuNPs was monitored by cyclic voltammetry (CV) and analyzed by Atomic Force Microscopy (AFM). The results show that the most dominant factor to control the AuNP size is the HAuCl₄ concentration. Deposition time and applied potential are the other factors controlling the electrodeposition. The smallest particle size was observed with the lowest HAuCl₄ concentration. The synthesis of the Krogmann’s salt crystals was conducted in 0.07 M of K₂Pt(CN)₄ aqueous solution with a potential pulse of 1.5 V (vs. SCE) for 0.1 s. Needle-shaped crystals with a size range of 600 nm to 5 µm in length and 100 nm  to 500 nm in width were synthesized on the bare HOPG. When the experiment was conducted with the same conditions on the AuNP-decorated HOPG, Nanorods with significantly reduced dimensions were produced. The nanoconfinement effect was contributed to the curvature of the nanoparticle seed. We electrochemically synthesized the Krogmann’s salt nanocrystals on patterned Cr/Au electrodes. The conductivity of the nanocrystals was measured in different vapors. The results show conductivity change upon vapor exposure of our Krogrmann’s salt sensor. Our sensor performance is comparable in response time and sensitivity to commercial vapor sensors. Our work contributes fundamental understanding to seed-mediated nucleation and a low-cost manufacturing method of nanosensors.