Raman spectra of all samples are recorded by a confocal Raman microscope setup (inVia, Renishaw) consisting of a 532 nm laser as excitation source, notch filter, a turnable grating (1800 lines mm -1 ), a CCD camera and a light microscope (Leica, DMI2500). The microscope is equipped with a x100 objective (Leica) to focus the laser spot (ca. 1 µm) on the sample as well as to collect the scattered Raman light. Before the measurements, the instrument is calibrated to a band at 520.4 cm -1 of a polycrystalline silicon disk. All samples are prepared onto a glass slide and several single spectra are recorded between 100-2000 cm -1 . In all cases, the laser power is adjusted to 0.1 mW and each sample spot illuminated for 10 s. Several spectra are recorded at various positions at the samples to ensure homogeneity. are in agreement with previously reported ones. Another difference in the Raman spectra presented in Fig. symmetric and antisymmetric S-S stretching are nearly absent. As the chain length increases to six sulfur atoms in DIB-S 6 -DIB, the Raman peak corresponding to the antisymmetric vibration appears, whereas that attributed to the symmetric stretching remains unnoticeable.