n-Type Fullerene-Carbon Dots: Synthesis and Electrochemical and Photophysical Properties

The covalent incorporation of C₆₀ and C₇₀ derivatives of the well-known n-type organic semiconductor PCBM ([6,6]-phenyl-C61-butyric acid methyl ester) onto carbon dots (CD) is described. Morphological and structural characterization reveal combined features of both pristine starting materials (CD and PCBM). Electrochemical investigations evidenced the existence of additional reduction processes to that of CD or PCBM precursors, showing rich electron-acceptor capabilities, with multistep processes in an affordable and narrow electrochemical window (ca. 1.5 V). Electronic communication in the obtained nanoconjugated species were derived from steady-state absorption and emission spectroscopies, which showed bathochromically shifted absorptions and emissions well entering the red region. Finally, the lower fluorescence quantum yield of CD-PCBM nanoconjugates, compared with CD, and the fast decay of the observed emission of CD, support the existence of an electronic communication between both CD and PCBM units in the excited state.