Ligand‐Defined Interfacial Chemistry Enables Instant and Sequence‐General DNA Chemisorption on Gold Nanoparticles Toward Label‐Free SERS With Single‐Base Resolution

ABSTRACT A coherent mechanistic framework for DNA adsorption on gold nanoparticles (AuNPs) remains elusive, hindering the rational construction of spherical nucleic acids (SNAs). Here, we show that ligand‐defined interfacial charge regulation, achieved using weakly ionized ascorbic acid (AA) ligands, markedly lowers the kinetic barrier for DNA chemisorption on AuNPs. Under near‐neutral conditions, this interface enables rapid, sequence‐general functionalization of AuNPs with both thiolated and non‐thiolated oligonucleotides through simple vortex mixing, even for DNA containing only a single terminal adenine. The AA‐regulated interface also overcomes the long‐standing incompatibility between ‐butanol dehydration and non‐thiolated DNA, enabling sequence‐general SNA formation under dehydration conditions across multiple nanoparticle systems. Mechanistic studies indicate that AA reduces interfacial electrostatic repulsion while promoting hydrogen‐bond‐assisted surface interactions, and base‐substitution experiments identify the adenine N6‐amino group as a critical site for chemisorption. The resulting ordered DNA corona generates uniform plasmonic nanogaps, enabling reproducible, label‐free SERS with single‐base resolution for nucleotide discrimination and cytosine methylation analysis. This work establishes a general interfacial design strategy for constructing uniform plasmonically active nucleic acid nanostructures under mild conditions.