Functional　photothermal　nanomaterials　have　gained　widespread　attention　in　the　field　of　precise　cancer　therapy　and　early　disease　diagnosis　due　to　their　unique　photothermal　conversion　properties.　However,　the　relatively　narrow　temperature　response　range　and　the　outputable　accuracy　of　commercial　thermometers　limit　the　accurate　detection　of　biomarkers.　Herein,　we　designed　a　liposome-embedded　Cu2-xAgxS　amplification-based　photothermal　sensor　for　the　accurate　determination　of　cardiac　troponin　I　(cTnI)　in　health　monitoring　and　point-of-care　testing　(POCT).　The　combinable　3D-printing　detecting　device　monitored　and　visualized　target　signal　changes　in　the　testing　system　under　the　excitation　of　near-infrared　(NIR)　light,　which　was　recorded　and　evaluated　for　possible　pathogenicity　by　a　smartphone.　Notably,　we　predicted　the　potentially　efficient　thermal　conversion　efficiency　of　Cu2-xAgxS　from　the　structure　and　charge　density　distribution,　calculated　by　the　first-principles　and　density　functional　theory　(DFT),　which　provided　a　theoretical　basis　for　the　construction　of　novel　photothermal　materials,　and　the　experimental　results　proved　the　correctness　of　the　theoretical　projections.　Under　optimal　conditions,　the　photothermal　immunoassay　showed　a　dynamic　linear　range　of　0.02-10　ng　mL(-1)　with　a　detection　limit　of　11.2　pg　mL(-1).　This　work　instructively　introduces　promising　theoretical　research　and　provides　new　insights　for　the　development　of　sensitive　portable　photothermal　biosensors.