Polyvinylpyrrolidone (PVP)-based silver nanoprisms (AgNPrs) show an initial stacking geometry because of their low zeta potential and electrostatic interaction between face-to-face energetically stable {111} surface-bound pyrrolidone groups through the Na + -ioninduced cation−π interaction. Congested interplanar space between AgNPrs allows As(III) to react differentially with silver atoms from facial {111} and peripheral {110} facets to result in smaller stackings and finally nanoseeds. Above this critical concentration of As(III), PVP leached out from nanoparticles to form nanoseed-engulfed emulsions and induced controlled aggregation. This entire morphological transition has been decoded by recording their surface plasmon and surfaceenhanced Raman scattering tuning and confirmed by the transmission electron microscopy study. Strong affinity and selectivity of As(III) toward the Ag atom (verified and estimated by the HF/3-21g* level of density functional theory calculation) coupled with low-cost colorimetry provide us a versatile assay with potential application in the environmental protection drive.

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.

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