Red‐Shifted Absorption of C‐Dots for Utilization in Hybrid Nano‐Optoelectronics by Application of Systematically Synthesized Precursor Molecules

In this work, a facile, easy and scalable synthetic protocol is modified at the precursor level to shift absorption of the resulting carbon nanodots (C-dots) to larger wavelengths. Using the knowledge about possible intermediates during the solvothermal pyrolysis for predictions of the final absorption of the products, several types of precursor variations from the original mixture of citric acid (CA) and polyethylenimine (PEI) are being tested. Syntheses over distinct steps of refined aromatic amine compounds with different size and number of functional groups are performed and the structures transferred into the pyrolysis protocol. UV-VIS measurements prove the success of the red-shifted absorption of the resulting products and show limitations of the precursor-vise tunability. Photoluminescence measurements are conducted with the most promising example of each optimization category to prove a correlation between absorption and luminescence behavior. H-1 DOSY NMR experiments are used for size comparison between the particles in solution to check for an impact between particle size and absorption. Optimized, tailor-made C-dots are tested as light-harvesters for application in hybrid nanodevices in combination with ZnO nanowire arrays. The photoconductivity can be increased tremendously in wavelengths above the semiconductor band gap using the tuned C-dots as photosensitizers.