Single-layer　carbon　dots　(CDs)　are　used　as　capping　agents　to　synthesize　silver　nanoparticles　(AgNPs).　The　obtained　nanohybrids　(AgNPs/CDs)　can　be　self-assembled　into　nanostructures　like　nanochains　(1D-AgNPs/CDs),　nanoflats　(2D-AgNPs/CDs)　or　nanobodys　(3D-AgNPs/CDs)　by　simply　tuning　the　amount　of　added　CDs.　It　is　found　that　CDs　play　a　key　role　in　controlling　the　aggregation　AgNPs/CDs.　The　formation　mechanisms　of　the　AgNPs/CDs　aggregates　have　been　discussed.　On　the　basis,　the　effects　of　aggregation　dimension　on　the　surface　plasmon　absorption　and　surface　enhanced　Raman　spectroscopy　(SERS)　activity　of　AgNPs/CDs　are　investigated　and　discussed.　It　is　found　that　the　aggregation　of　AgNPs/CDs　creates　strong　localized　surface　plasmon　resonance.　Furthermore,　the　aggregated　AgNPs/CDs　of　different　dimension　have　similar　absorption　intensity　in　the　range　from　500　to　800　nm,　which　is　most　commonly　used　in　the　surface　enhanced　Raman　spectroscopy　(SERS)　measurement.　The　outstanding　local　electromagnetic　field　of　the　aggregated　AgNPs　and　the　enrichment　effect　of　the　CDs　towards　the　analytes　make　all　the　obtained　materials　to　be　SERS　substrates.　In　particular,　2D-AgNPs/CDs　exhibit　an　ultrahigh　enhancement　factor　of　4.02　×　1014　and　a　good　reproducibility　during　the　SERS　test,　using　crystal　violet　as　the　model　target　molecule.　The　applicability　of　2D-AgNPs/CDs　in　SERS　detection　is　further　confirmed　by　the　measurement　of　trace　thiram　residual　in　apple.　©　2021　Elsevier　Ltd