Ingenieurwissenschaften und zugeordnete Tätigkeiten
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- Absolute fluorescence quantum yield (3) (entfernen)
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Lanthanide-doped up-converting nanoparticles (UCNPs) are promising reporters for medical diagnostics and bioimaging. Current limitations present their relative low absorption cross sections and low fluorescence efficiencies, with the latter being affected by particle size, surface chemistry, and microenvironment, particularly water.
Here, we present results from systematic studies of the excitation power density dependent upconversion luminescence spectra, intensities/intensity ratios of the individual emission bands, slope factors, and quantum yields of UCNPs of varying size, dopant concentration, and surface chemistry in different microenvironments as well as the up- and downconversion luminescence decay kinetics of the different emission bands. Moreover, first studies of the energy transfer from UCNPs to surface-bound organic dyes acting as fluorescence acceptors are shown. Based upon these measurements, fluorescence deactivation channels are identified and spectroscopic parameters for the screening of material performance are derived.
Lanthanide-doped up-converting nanoparticles (UCNPs) are promising reporters for medical diagnostics and bioimaging, which are excited in the near infrared (NIR) by multiphoton absorption processes, and show multiple narrow emission bands in the visible (vis) and NIR, long luminescence lifetimes in the μs range, and excellent photostability. Current limitations present their relative low absorption cross sections and low fluorescence efficiencies, with the latter being affected by particle size, surface chemistry, and microenvironment, particularly water.
Here, we present results from systematic studies of the excitation power density dependent upconversion luminescence spectra, intensities/intensity ratios of the individual emission bands, slope factors, and quantum yields of UCNPs of varying size, dopant concentration, and surface chemistry in different microenvironments as well as the up- and downconversion luminescence decay kinetics of the different emission bands. Moreover, first studies of the energy transfer from UCNPs to surface-bound organic dyes acting as fluorescence acceptors are shown. Based upon these measurements, fluorescence deactivation channels are identified and spectroscopic parameters for the screening of material performance are derived.
Photoluminescence techniques are amongst the most widely used tools in the life sciences, with new and exciting applications in medical diagnostics and molecular imaging continuously emerging. Advantages include their comparative ease of use, unique sensitivity, non-invasive character, and potential for multiplexing, remote sensing, and miniaturization. General drawbacks are, however, signals, that contain unwanted wavelength- and polarization contributions from instrument-dependent effects, which are also time-dependent due to aging of instrument-components, and difficulties to measure absolute fluorescence intensities. Moreover, scattering systems require special measurement geometries and the interest in new optical reporters with emission > 1000 nm strategies for reliable measurements in the second diagnostic for the comparison of material performance and the rational design of new fluorophores with improved properties.
Here, we present strategies to versatile method-adaptable liquid and solid fluorescence standards for different fluorescence parameters including traceable instrument calibration procedures and the design of integrating sphere setups for the absolute measurement of emission spectra and quantum yields in the wavelength region of 350 to 1600 nm. Examples are multi-emitter glasses, spectral fluorescence standards, and quantum yield standards for the UV/vis/NIR