Preparation of nanoparticles

We have studied preparation and applications of several kinds of nanoparticles. Certain nanoparticles of semiconductor materials exhibit a strong luminescence with a broad excitation and very narrow emission spectrum. These nanoparticles, often called quantum dots (QD), have unique properties when compared with standard fluorophores. Besides the very narrow emission an important advantage of using QDs instead of standard fluorescent molecules is their stability towards photobleaching (important for extended imaging times). This may allow luminescence wavelength coded multiplexing for parallel manipulation/detection of many different particles and their imaging based sorting (Image 1). We have already mastered preparation and a variety of chemistries for covalent attachment of QDs to small organic molecules, proteins and antibodies and their electrophoretic separation. The laboratory is furnished with four laboratory-constructed systems for capillary electrophoresis with LIF detection (Image 2). The laser-induced fluorescence detectors have been constructed for Ar ion, HeNe and diode lasers, photomultipliers and intensified CCD camera furnished with ns gating for spectral acquisition. Two laser-induced fluorescence systems, intended for the detection in microfluidic separation devices, are integrated with an epifluorescence microscope.

The instrumentation for surface enhanced Raman spectrometry has already been developed at IACH (Image 3). Strong signal enhancement was achieved using silver nanoparticles immobilized by laser beam on the wall of fused silica capillary.