Silica　nanoparticles,　with　entrapped　hydrophobic　photosensitizer　tetra-alpha-(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　100　nm),　exhibited　strong　Q-band　absorption　of　ZnPc(OAr)(4)　centered　at　701　nm.　The　aqueous　solubility　of　ZnPc(OAr)(4)　encapsulated　in　silica　nanoparticles　was　obviously　improved.　The　nanoparticles　efficiently　generated　singlet　oxygen　(O-1(2))　both　in　organic　and　aqueous　solutions　after　being　irradiated　at　suitable　wavelength.　The　resulting　O-1(2)　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　80　pmol/L,　minimized　the　nonspecific　adsorption.　Such　an　aptamer-based　biosensor　is　feasible　in　screening　biomarkers　in　complex　matrices　at　ultratrace　levels.　(C)　2013　Elsevier　B.V.　All　rights　reserved.