Highly Sensitive Laser Scanning of Photon-Upconverting Nanoparticles on a Macroscopic Scale.

An upconversion laser scanner has been optimized to exploit the advantages of photon-upconverting nanoparticles (UCNPs) for background-free imaging on a macroscopic scale. A collimated 980 nm laser beam afforded high local excitation densities to account for the nonlinear luminescence response of UCNPs. As few as 2000 nanoparticles were detectable, and the linear dynamic range covered more than 5 orders of magnitude, which is essentially impossible by using conventional fluorescent dyes.

Surface modification and characterization of photon-upconverting nanoparticles for bioanalytical applications.

Photon-upconverting nanoparticles (UCNPs) can be excited by near-infrared light and emit visible light (anti-Stokes emission) which prevents autofluorescence and light scattering of biological samples. The potential for background-free imaging has attracted wide interest in UCNPs in recent years. Small and homogeneous lanthanide-doped UCNPs that display high upconversion efficiency have typically been synthesized in organic solvents.

Electrophoretic characterization and purification of silica-coated photon-upconverting nanoparticles and their bioconjugates.

Photon-upconverting nanoparticles (UCNPs) have attracted much interest as a new class of luminescent label for the background-free detection in bioanalytical applications. UCNPs and other nanoparticles are commonly coated with a silica shell to improve their dispersibility and chemical stability in aqueous buffer and to incorporate functional groups for subsequent bioconjugation steps. The process of silica coating, however, is difficult to control without suitable analytical and preparative methods.

Photon upconverting nanoparticles for luminescent sensing of temperature.

Photon upconverting nanoparticles convert near-infrared into visible light (anti-Stokes emission), which strongly reduces the background of autofluorescence and light scattering in biological materials. Hexagonal NaYF(4) nanocrystals doped with Yb(3+) as the sensitizer and Er(3+)/Ho(3+)/Tm(3+) as the activator display at least two emission lines that respond differently to temperature changes. The ratio of the main emission line intensities enables a self-referenced optical readout of the temperature in the physiologically relevant range from 20 to 45 °C.