Organic semiconductors have been discovered to exhibit impressive surface-enhanced Raman scattering (SERS) activity recently. However, owing to the underdeveloped candidate materials and relatively low SERS sensitivity, practical application of SERS detection based on organic materials is still a challenge. Herein, we explored ways to further enhance the SERS sensitivity of π-conjugated fluorinated 7,7,8,8-tetracyanoquinodimethane derivatives (F n TCNQ, n = 2, 4) by utilizing the charge-localization effect induced by two-dimensional (2D) MoS 2 flakes. A strong Raman signal enhancement in SERS has been realized via an organic/2D heterostructure constructed by F n TCNQ nanostructures grown on a 2D MoS 2 flake. Moreover, F 2 TCNQ and F 4 TCNQ show different SESR sensitivities due to different numbers of cyano groups leading to different charge transfer (CT) directions. The SERS enhancement factor (EF) of methylene blue (MB) molecules on the optimal F 4 TCNQ/MoS 2 nanocomposite substrate can reach as high as 2.531 × 10 6 , and the concentration of the limit of detection (LOD) is as low as 10 −10 M. The SERS results for MB, rhodamine 6G (R6G), and 4aminothiophenol (4-ATP) molecules demonstrate that high versatility, low cost, good stability, and easy preparation will make the F n TCNQ/MoS 2 SERS platform promising for the detection of trace molecules. The studies on the complex microscopic interaction of organic/2D composite nanomaterials will provide some novel insights into improved SERS performance and mechanisms.
Topological nanomaterials generally exhibit different defect structures, high specific surface areas, and varying bandgaps. These special geometries, energy-level structures, and interfacial interaction properties provide possibilities to explore interesting properties in the surface-enhanced Raman scattering (SERS). Such properties offer unexplored possibilities for exploring interesting physics and materials science in the field of SERS physical property research and further enhancing substrate materials’ SERS activity. In this paper, the ZnSe topological nanowire crystallite structure was grown using the chemical vapor deposition method, twin defects were introduced, and a topological branched structure that caused the corresponding changes in SERS activity was systematically investigated. On topological ZnSe nanowires, rhodamine 6G (R6G), methylene blue (MB), and crystalline violet (CV) molecules were detected using Raman spectroscopy. The Raman signal enhancement of MB on topological branched nanowires was about 1.9 times that of the trunk nanowires. Finally, the national standard measurement of malachite green (MG) content in water bodies were realized. The results suggest that semiconductor ZnSe topographical nanowires are an emerging class of SERS substrates, and a thorough investigation into the relationship between material structure and SERS performance in specific topological regions will provide new evidence for the principle of chemical enhancement of SERS, as well as recommendations for developing precisely functionalized SERS substrate nanomaterials.
Interface modification is an important way to get better performance from organic solar cells (OSCs). A natural biomolecular material methionine was successfully applied as the electron transport layer (ETL) to the inverted OSCs in this work. A series of optical, morphological, and electrical characterizations of thin films and devices were used to analyze the surface modification effects of methionine on zinc oxide (ZnO). The analysis results show that the surface modification of ZnO with methionine can cause significantly reduced surface defects for ZnO, optimized surface morphology of ZnO, improved compatibility between ETL and the active layer, better-matched energy levels between ETL and the acceptor, reduced interface resistance, reduced charge recombination, and enhanced charge transport and collection. The power conversion efficiency (PCE) of OSCs based on PM6:BTP-ec9 was improved to 15.34% from 14.25% by modifying ZnO with methionine. This work shows the great application potential of natural biomolecule methionine in OSCs.
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