Silicon Nanocrystals Coated By Porphyrins As Light-Harvesting Antennae
The synthesis of luminescent colloidal nanocrystals of silicon is still a difficult task in terms of reliability and reproducibility. We report the thermal decomposition of hydrogen silsequioxane, followed by etching and hydrosilylation . This method isolated SiNCs with good yields, high surface coverage and exceptional control over the dimensions and optical properties of the materials.
In the present work, the H-terminated nanocrystals were used as a platform for co-passivation with dodecene and different organic chromophores  by thermal hydrosilylation. For example, we functionalised two families of SiNC of average diameter of 2.5 and 5 nm with porphyrin chromophores: porphyrin excitation results in an efficient energy transfer to the nanocrystal core. To the best of our knowledge this is the first time in which highly efficient light harvesting from photoactive units to the silicon core have been demonstrated. This approach enabled us to circumvent the drawback of the low molar absorption coefficient of SiNCs. The investigated hybrid material exhibits high quantum yield also in the NIR spectral region with lifetime in the µs range.
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