Molecular engineering of organic semiconductors enables noble metal-comparable SERS enhancement and sensitivity

• Published in: Nature communications Vol. 10; no. 1; pp. 5502 - 9
• Main Authors: Demirel, Gokhan, Gieseking, Rebecca L. M., Ozdemir, Resul, Kahmann, Simon, Loi, Maria A., Schatz, George C., Facchetti, Antonio, Usta, Hakan
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 03.12.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 119/118; 140/133; 639/638/11; 639/638/403; Charge transfer; Computer applications; Electronics industry; Energy charge; Humanities and Social Sciences; Metals; Methylene blue; Molecular interactions; multidisciplinary; Nanostructure; Noble metals; Organic semiconductors; Photoluminescence; Photons; Platforms; Raman spectroscopy; Science; Science (multidisciplinary); Sensitivity enhancement; Spectroscopy; Spectrum analysis
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-13505-7

Nanostructured molecular semiconductor films are promising Surface-Enhanced Raman Spectroscopy (SERS) platforms for both fundamental and technological research. Here, we report that a nanostructured film of the small molecule DFP - 4T , consisting of a fully π-conjugated diperfluorophenyl-substituted quaterthiophene structure, demonstrates a very large Raman enhancement factor (>10 5 ) and a low limit of detection (10 −9  M) for the methylene blue probe molecule. This data is comparable to those reported for the best inorganic semiconductor- and even intrinsic plasmonic metal-based SERS platforms. Photoluminescence spectroscopy and computational analysis suggest that both charge-transfer energy and effective molecular interactions, leading to a small but non-zero oscillator strength in the charge-transfer state between the organic semiconductor film and the analyte molecule, are required to achieve large SERS enhancement factors and high molecular sensitivities in these systems. Our results provide not only a considerable experimental advancement in organic SERS figure-of-merits but also a guidance for the molecular design of more sensitive SERS systems. Organic semiconductors are considered promising Surface Enhanced Raman Spectroscopy platforms. Here the authors demonstrate that metal-free films based on a π-conjugated molecule containing a fully π-conjugated backbone provides an enhancement factor of 10 5 and detection limit of 10 −9 M for methylene blue.