Synthesis of Hot-Spot-Rich Silver Nanogap Networks within Flat Nanoframes and a Strategy for Targeted Protein Positioning near Plasmonic Hot Spots

We propose a surface-enhanced Raman spectroscopy (SERS) detection strategy that assembles Ag nanogap-integrated triangular nanoframes (NITNs) on Ni substrates. The Ag NITNs were synthesized via a one-pot tandem reaction followed by Ag coating. By tuning the void area fraction of the Ag NITNs, we engineered narrow intraparticle nanogaps (∼4 nm), which significantly concentrate the electromagnetic near-field. Then, we employed Ag NITNs for liquid-phase, SERS-based protein screening─a task hindered by the inherently weak Raman signals of proteins and their low affinity for plasmonic nanoparticle surfaces. The Ag NITNs were assembled into densely packed monolayer films on Ni substrates, thereby positioning His-tagged proteins in close proximity to the plasmonic hot spots through coordination bonding with the Ni surface. The platform exhibited outstanding stability and performance in rapid protein screening, achieving 100% sensitivity and selectivity in distinguishing His-tagged human serum albumin and protein G from their native (nontagged) counterparts within 1 min.