Well-designed shape anisotropical bi-metallic nanoparticles for optical bioanalytics

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Addressing pressing problems of modern medicine, biotechnology and environmental science, such as mastering of new and multiresistant pathogens, personalized medicine, or the development of sustainable biotechnological processes requires a diagnostic at the single cell level. Therefore novel and powerful sensoric approaches are needed, which combine a selective recognition with a general applicable transducing principle and a high transduction rate, and which are also applicable for small molecular ensembles or even single molecules. Optical sensing based on nanoscale transducer (LSPR localized surface plasmon resonance) shows a high potential for a broad application in bioanalytics with significant advantages (like simpler detection, miniaturization, parallelization) compared to the established SPR (propagating surface plasmon resonance). In order to utilize this potential, the proposed project develops novel, more sensitive plasmonic nanoparticles based on a combination of two sensitivity boosting effects, namely anisotropy (using silver prisms) and bi-metal composition. Anisotropic particles show an enhancement of the electromagnetic field in certain locations (like corners) leading to a higher sensitivity for refractive index changes by analytes binding there. This effect will be, for the first time, combined with the recently observed sensitivity enhancement due to thin secondary metal layer on plasmonic nanostructures [1].In order to utilize the advantages of such particles fully, a narrow distribution in size (and thereby in the resulting spectroscopic properties) is required, what will be realized by the development of a microfluidic synthesis of the particles. Beside more homogenous chemical and thermal seed formation conditions in small liquid compartments, this process is strongly influenced by the self-assembly of primary metal clusters into growing particle during the seed phase of the synthesis. Beyond increased primary seed formation, this microfludic synthetic approach enables to influence cluster arrangement independently from seed formation, what will allow the formation of novel bi-metallic particles with significantly improved biosensoric properties. Using form-anisotrope plasmonic nanoparticles, the proposed project will demonstrate how micro reaction technology can be applied for a systematic assembly of novel functional nanomaterials.