“…Many sensing methods have been investigated for DA detection, such as enzyme-linked immunosorbent assay, , chromatographic separation, , fluorescence sensing, , and electrochemical analysis tools. , However, the application of these methods is commonly limited by the requirements of expertise in operation, high cost, and expensive instrumentation. − Recently, plasmonic nanosensor systems have attracted the attention of many researchers owing to their simplicity, rapid detection, and high sensitivity. − In particular, noble metallic nanoparticles (NMPs), especially gold and silver nanoparticles, have been widely investigated in colorimetric and surface-enhanced Raman scattering (SERS) detection methods due to their unique optical and plasmonic properties, which strongly depend on their size, configuration, and interparticle distance. − Gold nanoparticles (AuNPs) possess attractive features such as chemical stability and simple synthetic methods to give high morphological uniformity. Silver nanoparticles (AgNPs) also exhibit practically useful properties to be used as a sensing probe, and they show a higher plasmonic efficiency than AuNPs. − Therefore, we reasoned that Au–Ag core–shell NPs could provide an excellent platform to develop colorimetric sensing systems. ,, …”