Preparation, characterization, and fabrication of uniform coated Y2O2S:RE3+ up-converting phosphor particles for biological detection applications

The unique features of Up-Converting Phosphor Technology (UPTT) have been demonstrated in several particle-based biological assays in recent years. The core-shell structured up-converting phosphor reagents were developed as ultra sensitive labels for biological detection applications. Submicron yttrium oxysulfide (Y2O2S) spheres co-doped with trivalent rare earth ion pairs (RE3+), e.g. Yb3+-Er3+ and Yb3+-Tm3+, were prepared using homogenous precipitation followed by a series of fluidized bed processes. These particles are capable of emitting intense phosphorescence when excited by 950 or 980 nm infrared diode lasers, possessing anti-Stokes shifts greater than 150 nm. We encapsulated Y2O2S:RE3+ particles with uniform silica shells to passivate the surface and to enhance the dispersibility. The surface of silica-coated particles was further modified with functionalized silanes to provide desired chemical groups (amino, thiol, or carboxyl) for covalent coupling to biomolecules. The functional group densities of the phosphor reagents were characterized using spectroscopic techniques. Fabricated up-converting phosphor reagents can be attached to biomolecules using standard bioconjugation techniques.

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