Any labeling with multicolor markers can be affected by the autofluorescence of biological tissue due to the UV or blue light excitation sources, or the results are affected by fluorescence resonance energy transfer. In this work, we present novel IR-to-vis upconverting nanoparticles of different rare earth metal dopants. With a single excitation source of 980 nm, four different colors of nanocrystals can be spectrally separated under multiplexing conditions. The particles were phase transferred into polar solvents by means of silica encapsulation and were characterized by transmission electron microscopy, X-ray diffraction, and photoluminescence spectroscopy.

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A novel organometallic synthesis method for the preparation of colloidal ZnS nanoparticles is presented. This method enables the synthesis of undoped ZnS nanocrystals as well as doping with Cu, Pb, or both. The particles can be covered with an undoped layer of ZnS, forming core/shell-type particles with the ZnS:Pb, ZnS:Cu, or ZnS:Cu,Pb cores. The particles were characterized via TEM, XRD, dynamic light scattering, and optical spectroscopy. We investigated the extrinsic surface defects and their coverage with an additional ZnS layer in detail by temperature-dependent luminescence and luminescence lifetime spectroscopy.

The present paper describes a new, facile and fast technique that can be used to incorporate CdSe/ZnS core/shell nanocrystals into polystyrene beads. The nanocrystals were immobilized within the polymer beads by demixing two nonmiscible solvents. The resulting beads were bright, homogeneously coded, and did not show any surface texture or photobleaching under application-relevant conditions. The beads were subsequently used on a model streptavidin-biotin binding system in order to demonstrate the applicability of the technique to enzyme-linked assays and multiplexing applications.

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The particle size dependent thermodynamic functions for the formation of electrons and holes are addressed for semiconductor CdSe nanocrystals (NCs). We recorded the temperature dependent absorbance spectra for a size series of colloidal CdSe NCs in a polymer composite material and analyzed the band-gap behavior. We report the analytical investigation of the temperature dependent band gap as a function of the particle size using two common theoretical approaches. The band gap as a function of temperature and particle size is mainly influenced by the large entropic values for the formation of electrons and holes.

This paper presents a novel optical concept for the readout of a parallel, bead-based fluorescence immunoassay conducted on a lab-on-a-disk platform. The reusable part of thc modular setup comprises a detection unit featuring a single LED as light source, two emissionfilters, and a color CCD-camera as standard components together with a spinning drive as actuation unit. The miniaturized lab-on-a-disk is devised as a disposable. In the read-out process of the parallel assay, beads are first identified by the color of incorporated quantum dots (QDs). Next, the reaction-specific fluorescence signal is quantified with FluoSpheres-labeled detection antibodies. To enable a fast and automated read-out, suitable algorithms have been implemented in this work. Based on this concept, we successfully demonstrated a Hepatitis-A assay on our disk-based lab-on-a-chip.