Au-Seeded Ag-Nanorod Networks for Electrocatalytic Sensing

Spherical gold nanoseed (∼5–6 nm)-induced (but not seed-mediated) silver nanorods (Hy-Au@AgNRs) of variable lengths have been synthesized by a new methodology that shows enhancement in catalytic activity as a function of nanorod length. Detailed characterization by atomic-scale resolution spectroscopy, precision scattering measurements, high-resolution microscopy, and theoretical modeling through the density functional theory (DFT) quantifies the presence of an enhanced number of multiple coaxial twin boundaries for longer Hy-Au@AgNRs, which ultimately results in an increased mechanical strain. By considering greater mechanical strain within Hy-Au@AgNRs, the density of states (DOS) calculation shows a prominent shift in electron density toward the Fermi level to assist in the tremendous catalytic activity of the longest nanorod (NR) (Hy-Au@AgNR840). Further assembling of these inherently active Hy-Au@AgNR840s by thiol click chemistry not only efficiently creates multiple low-coordinated crystal sites to improve their catalytic activity but also the resultant uniform two-dimensional (2D) platform shows better adsorptivity and easy moldability on the electrode surface for increased shelf life, a uniform porous structure to trap a large extent of redox systems, enhanced stability in a broad pH and solvent range to increase the applicability, and long-term stability under ambient conditions for safe storing, making this material a unique nonenzymatic scalable universal electrocatalytic platform. The ability of this material to act as a nonenzymatic universal catalytic platform has been verified by applying it for highly specific and ultrasensitive detection of a series of human metabolites, which include different important vitamins, potent endogenous antioxidants, essential amino acids for the biosynthesis of proteins, simple monosaccharides, and essential trace-metal ions. Our study for the first time mechanistically explores the combined role of anisometric seeding to create an intermetallic twin boundary along with its size to control the strain-induced catalytic activity to offer us a universal 2D electrocatalytic sensing platform by a combined approach of experiment and theory.