A　simple　method　is　developed　for　the　direct　synthesis　of　aggregated　silver　nanoparticles　(a-AgNPs),　which　show　strong　and　wavelength-tunable　localized　surface　plasmon　resonance　(LSPR).　Three　a-AgNPs　(532-a-AgNPs,　633-a-AgNPs　and　787-a-AgNPs)　exhibiting　the　maximum　LSPR　wavelength　coinciding　well　with　those　of　lasers　commonly　used　in　SERS　detection　(532,　633　and　785　nm)　are　obtained.　Thus,　the　three　a-AgNPs　possess　abundant　plasmonic　hotspots　under　the　irradiation　of　corresponding　laser.　Moreover,　the　three　a-AgNPs　show　robust　stability　in　water,　and　can　be　developed　into　liquid　substrates　directly　for　SERS　determination.　All　the　three　substrates　(532-sub,　633-sub,　and　787-sub)　show　excellent　SERS　activity　to　4-mercaptobenzoic　acid　(4-MBA)　due　to　the　synergistic　effect　of　strong　electromagnetic　enhancement　(EM)　and　chemical　enhancement　(CM)　effects.　The　obtained　787-sub　is　further　applied　for　the　determination　of　thiram　in　juices.　The　low　detection　limit　of　10　ppb　and　outstanding　recoveries　of　91.75–109.92　%　suggest　substantially　the　reliability　and　practicality　of　the　developed　SERS　substrates　in　food　safety　detection.　©　2025　Elsevier　B.V.