Reporter-Embedded SERS Tags from Gold Nanorod Seeds: Selective Immobilization of Reporter Molecules at the Tip of Nanorods

Reporter-embedded (RE) tags are a generation of sensitive, stable surface: enhanced Raman scattering (SERB), tags with Raman reporters embedded between gold nano article(NP) core and gold (or silver), shells. Most of the reported RE tags have b-een designed using: Au nanospheres as a seed material. Herein, we investigated the: synthesis and SERS properties of AuNR/reporter/Ag tags by using gold nanorod (AuNR) seeds witk,ariisotropic physical and optical features. Several highlighted points discovered, including the following: (1) The cetyltrimethyl ammonium bromide (CTAB) layer induced the coexistence of chemically and physically adsorbed RaMan reporters on AuNR Conventional washing of the Atil TR-reporter complek with water results in the formation of an internal external mixed tag. To obtain a pure RE structure, an additional extraction step involving a CTAB solution was essential. (2) The anisotropic distribution of CTAB on AuNR resulted in the preference of the Raman reporters to adsorb to the hotspot at the AuNR tip, which made it a perfect match for improving the SERS signal of the tag. (3) An.anisotropic silver coating occurred with the shell thickness on the AuNThside-growing much faster than the shellthianess at the tip. This feature ensured that the tag grew to a suitable size with enough silVer for SERS enhancement without shadowing the effective Raman reporters at the tip too much. (4) RE tags showed better in vitro and in vivo signal stabilities compared with their external labeling counterparts. Moreover, a novel pH-sensitive SERS peak test was proposed by using 4-mercaptobenzoic acid as the Raman reporter to verify thin coverage by a silver layer. We believe this tag can be broadly applied for molecular detection and bioimaging, and the proposed preparation and structure verification methods can provide universal guidance in the design of novel RE tags.