As　a　biological　thiol　closely　related　to　the　incidence　of　gastric　cancer,　homocysteine　(Hcy)　has　been　re-ported　to　be　detected　in　vivo　and　in　vitro　.　The　design　of　ratiometric　photoluminescent　probes　often　relies　on　the　unique　chemical　structure　of　the　molecular.　In　this　paper,　we　designed　and　synthesized　three　aldehyde-containing　iridium(III)　complexes　and　characterized　their　structure　and　photophysical　proper-ties.　They　showed　a　good　specificity　for　Hcy　detection.　The　color　of　the　solution　gradually　changed　from　red　to　pale　yellow.　The　photoluminescent　variation　from　red　to　green　was　observed　by　the　naked　eye　after　addition　of　Hcy　to　the　solution　of　the　Ir1　([(CHO-pba)(2)Ir(bpy-2NH(2))]PF6),　Ir2　([(CF3-pba)(2)Ir(bpy-2NH(2))]PF6)　and　Ir3　([(CH3-pba)(2)Ir(bpy-2NH(2))]PF6)　with　a　large　blue　shift　by　120,　63　and　106　nm,　respec-tively.　Based　on　the　differences　in　their　structures,　it　could　be　inferred　that　this　type　of　ratiometric　pho-toluminescent　probe　based　on　iridium(III)　complexes　with　aldehyde　was　related　to　the　strong　electron　-donating　effect　of　the　nitrogen-containing　substituents　on　the　bipyridine　ligand　in　the　structure,　and　the　introduction　of　electron-donating　groups　on　the　4-(2-pyridinyl)benzaldehyde　(pba)　ligand　can　enlarge　the　blue　shift　of　the　photoluminescent　wavelength　upon　sensing　of　Hcy.　On　the　other　hand,　iridium(III)　com-plexes　are　currently　recognized　as　a　third-generation　good　photodynamic　therapy　photosensitizer.　The　photodynamic　therapy　properties　of　the　three　iridium(III)　complexes　in　this　article　have　also　been　evalu-ated.　All　of　them　have　strong　singlet　oxygen　generation　ability　and　low　cytotoxicity　which　are　expected　to　be　used　in　photodynamic　therapy　and　Hcy　detection.　(C)　2022　Elsevier　B.V.　All　rights　reserved.