Silica　nanoparticles,　with　entrapped　hydrophobic　photosensitizer　tetra-α-(2,　4-di-tert-butylphenoxy)-phthalocyaninato　zinc　(ZnPc(OAr)4),　were　synthesized　by　hydrolyzing　triethoxyvinylsilane　(TEVS)　and　3-amino　propyl　triethoxysilane　(APTES).　The　as-prepared　nanoparticles,　which　were　highly　monodispersed　spheres　(about　100nm),　exhibited　strong　Q-band　absorption　of　ZnPc(OAr)4　centered　at　701nm.　The　aqueous　solubility　of　ZnPc(OAr)4　encapsulated　in　silica　nanoparticles　was　obviously　improved.　The　nanoparticles　efficiently　generated　singlet　oxygen　(1O2)　both　in　organic　and　aqueous　solutions　after　being　irradiated　at　suitable　wavelength.　The　resulting　1O2　then　initiated　chemiluminescence　(CL)　by　reacting　with　a　methyl　cypridina　luciferin　analog　(MCLA).　Based　on　the　photoinduced　CL,　a　sensitive　aptamer-based　sandwich-type　sensor　was　presented　to　detect　human　thrombin.　Thrombin　was　first　attached　to　Pc@SiO2　via　secondary　aptamer,　and　then　they　were　collected,　for　CL　determination,　by　beads　with　primary　aptamer.　The　proposed　approach,　which　was　highly　selective　with　a　low　detection　limit　of　80pmol/L,　minimized　the　nonspecific　adsorption.　Such　an　aptamer-based　biosensor　is　feasible　in　screening　biomarkers　in　complex　matrices　at　ultratrace　levels.　©　2013　Elsevier　B.V.