π-Conjugated organic semiconductors have been explored in several optoelectronic devices, yet their use in molecular detection as surface-enhanced Raman spectroscopy (SERS)-active platforms is unknown. Herein, we demonstrate that SERS-active, superhydrophobic and ivy-like nanostructured films of a molecular semiconductor, α,ω-diperfluorohexylquaterthiophene (DFH-4T), can be easily fabricated by vapour deposition. DFH-4T films without any additional plasmonic layer exhibit unprecedented Raman signal enhancements up to 3.4 × 103 for the probe molecule methylene blue. The combination of quantum mechanical computations, comparative experiments with a fluorocarbon-free α,ω-dihexylquaterthiophene (DH-4T), and thin-film microstructural analysis demonstrates the fundamental roles of the π-conjugated core fluorocarbon substitution and the unique DFH-4T film morphology governing the SERS response. Furthermore, Raman signal enhancements up to ∼1010 and sub-zeptomole (<10−21 mole) analyte detection were accomplished by coating the DFH-4T films with a thin gold layer. Our results offer important guidance for the molecular design of SERS-active organic semiconductors and easily fabricable SERS platforms for ultrasensitive trace analysis.
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This work was partially supported by Gazi University (grant no. 05/2015-19) and Polyera Corporation. G.D., H.U. and Y.D. acknowledge support from the Turkish Academy of Sciences, Distinguished Young Scientist Award (TUBA-GEBIP). A.F. thanks the Shenzhen Peacock Plan project (KQTD20140630110339343) and the BSF (AGMT-2012250///02).
The authors declare no competing financial interests.
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Yilmaz, M., Babur, E., Ozdemir, M. et al. Nanostructured organic semiconductor films for molecular detection with surface-enhanced Raman spectroscopy. Nature Mater 16, 918–924 (2017). https://doi.org/10.1038/nmat4957
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