Synthesis and characterisation of highly fluorescent core–shell nanoparticles based on Alexa dyes
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Current and future developments in the emerging field of nanobiotechnology are closely linked to the rational design of novel fluorescent nanomaterials, e.g. for biosensing and imaging applications. Here, the synthesis of bright near infrared (NIR)-emissive nanoparticles based on the grafting of silica nanoparticles (SNPs) with 3-aminopropyl triethoxysilane (APTES) followed by covalent attachment of Alexa dyes and their subsequent shielding by an additional silica shell are presented. These nanoparticles were investigated by dynamic light scattering (DLS), transmission electron microscopy (TEM) and fluorescence spectroscopy. TEM studies revealed the monodispersity of the initially prepared and fluorophore-labelled silica particles and the subsequent formation of raspberry-like structures after addition of a silica precursor. Measurements of absolute fluorescence quantum yields of these scattering particle suspensions with an integrating sphere setup demonstrated the influence of dye labelling density-dependent fluorophore aggregation on the signaling behaviour of such nanoparticles.
KeywordsSilica Alexa dyes Fluorescent particles Quantum yields Nanoparticles Protective shell Nanobiotechnology
This study has been supported by the Federal Institute for Materials Research and Testing (BAM) within the framework of its ‘Innovationsoffensive’ under the Project name ‘Nanotox’ and by the Federal Ministry of Economics and Technology (BMWI-22/06). The authors also thank G. Hidde and I. Dörfel for excellent technical and analytical assistance.
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