Sb³⁺-doped CaS Luminescent Nanoprobes: Controlled Synthesis,Pptical Properties And Bioapplication

Inorganic luminescent nanocrystals(NCs)doped with main-group ns²-metal ions have evoked tremendous interest in many technological fields owing to their superior optical properties.Unlike the d-and f-electron dopants(e.g.,Mn²⁺,Cr³⁺,and rare-earth ions)that usually suffer from a low absorption efficiency due to the parity-forbidden d?d and f?f transitions,the main-group s-electron dopants possess a large absorption coefficient originating from the allowed s²?sp transition.Therefore,the s-electron dopants can act as both sensitizers and activators for tailoring the optical absorption and emission properties of a variety of luminescent materials.Herein,we report a new class of luminescent nanoprobes based on 5s²-metal Sb³⁺-doped CaS NCs that are excitable by using a near ultraviolet light-emitting diode.The optical properties and excited-state dynamics of Sb³⁺in CaS NCs are comprehensively surveyed through temperature-dependent steady-state and transient photoluminescence(PL)spectroscopies,and the applications of CaS:Sb³⁺NCs in fluorescent biological imaging have been demonstrated.The main research contents are as follows:1.High-quality CaS:Sb³⁺NCs are synthesized through a high-temperature co?precipitation method.Powder XRD patterns show that all diffraction peaks of the NCs can be well indexed into cubic CaS without any additional impurities.TEM results show that the synthesized CaS:Sb³⁺NCs have regular morphology,uniform size and good monodispersity with an average particle size of about 15.0 nm.2.The optical characteristic of CaS:Sb³⁺NCs have been systematically studied by means of PL spectroscopies,PL decay curves and temperature-dependent PL emission spectra.The energy transfer between the host CaS and dopant Sb³⁺and the excited-state dynamics of Sb³⁺in nanocrystals are discussed.We also optimized the doping concentration of Sb³⁺,and determined that the optimal doping concentration of Sb³⁺was 0.01 mol%,and the corresponding quantum yield was as high as 17.3%.It is revealed that the Sb³⁺in the excited state undergo a dynamic Jahn-Taller distortion,which accounts for the broadband(470 me V)and large Stokes shift(169 nm)of the 5s²-metal Sb³⁺green emission.The luminescence mechanism model of Sb³⁺is proposed.3.For the sake of biological applications,we coated the hydrophobic CaS:Sb³⁺NCs with a layer of amphiphilic Lipo(DSPE-PEG-biotin)through ligand adsorption.By taking advantage of the intense PL of Sb³⁺,we demonstrated in proof-of-concept experiments the application of biotinylated CaS:Sb³⁺NCs for targeted cancer cell imaging and zebrafish imaging.These results reveal the application prospect of CaS:Sb³⁺nanoprobes in fluorescent biological imaging,and lay a foundation for the design of novel multifunctional luminescent nanoprobes using principal group ns²-metal doping in the future.