PEI-znS:Mn²⁺ Quantum Dots For Room Temperature Phosphorescent Detection Of Heparin And Synthesis Of NaYF₄:Yb³⁺/Er³⁺,Tm³⁺Nanoparticles

Recently, nanomaterial-based fluorescent probes for sensing and imaging in biochemistry and analytical chemistry have become one of the most attractive research fields, and doped nanoparticles with good luminescence properties have become a research hotpot. Aiming at avoiding the significant interference from autofluorescence and scattering light of the complicated sample matrixes, we developed the probes based on Mn-doped ZnS quantum dots (ZnS:Mn2+QDs) probe and Yb3+/Er3+, Tm3+co-doped NaYF4upconverting nanoparticles. The main contents are summarized as follows:(1) Room temperature phosphorescent (RTP) turn-on assay for heparin detection with tunable sensitivity and detection window was demonstrated based on the target induced self-assembly of polyethyleneimine capped Mn-doped ZnS (PEI-ZnS:Mn2+) QDs. The proposed method can cover the whole therapeutic dosing concentration range in post-operation and long-term therapy (0.2-1.2U/mL,1.7-10μM) and cardiovascular surgery (2-8U/mL,17-67μM) in10mM Tris-HCl (pH7.4) buffer, and can be applied for heparin determination in100-fold diluted human serum samples. The tunable sensitivity and detection window was ascribed to the tunable particle size and ligand loading amount of PEI-ZnS:Mn2+QD arising from the chain length (or molecule weight) and feed amount of PEI. The chain length of PEI exhibited significant effect on the particle size and ligand loading amount, and ultimately had important influence on both the sensitive and detection window. The feeding amount of PEI, however, greatly affected the ligand loading amount alone, and in turn affected only the detection window.(2) Using the ultrasonic wave assisted solvothermal synthesis methods, we synthesized the NaYF4:Yb3+/Er3+nanoparticles with red/green dual-color upconverting fluorescent emissions (665nm,526/545nm), NaYF4:Yb3+/Tm3+nanoparticles with monochromatic near infrared (NIR) upconverted fluorescent emission (805nm) and NaYF4:Yb3+/Er3+, Tm3+nanoparticles with dual NIR upconverted fluorescent emissions (665and805nm). The upconverting fluorescent mechanisms of these naoparticles have been discussed.