(a) The PL of 7-AGNRs on quartz (peak at ~1.8 eV) brightens when the sample is exposed to blue light (440 nm). (b) The PL is partially polarized along the GNR axis demonstrating its origin in the GNR. Here the spectra for polarizer and analyzer both parallel to the ribbon axis (red solid line) and both perpendicular to the ribbon axis (blue solid line) are shown. The emission peaks are at a significantly lower photon energy (marked with D) than the excitons E11 and E22. (c) Scanning a 440 nm laser focus allows the writing of luminescent patterns on GNR monolayers. Here the letters "UoC" have been rendered bright. The four panels correspond to the four possible orientations of polarizer and analyzer with respect to the GNR axis and are indicated by arrows. The first (second) arrow denotes the polarization of the exciting (analyzed) light. The vertical direction corresponds to light polarization along the GNR axis according to the sketch of a GNR in the inset to b.
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