Enabling three-dimensional porous architectures via carbonyl functionalization and molecular-specific organic-SERS platforms

Abstract

Molecular engineering via functionalization has been a great tool to tune noncovalent intermolecular interactions. Herein, we demonstrate three-dimensional highly crystalline nanostructured D(C7CO)-BTBT films via carbonyl-functionalization of a fused thienoacene π-system, and strong Raman signal enhancements in Surface-Enhanced Raman Spectroscopy (SERS) are realized. The small molecule could be prepared on the gram scale with a facile synthesis-purification. In the engineered films, polar functionalization induces favorable out-of-plane crystal growth via zigzag motif of dipolar C = O···C = O interactions and hydrogen bonds, and strengthens π-interactions. A unique two-stage film growth behavior is identified with an edge-on-to-face-on molecular orientation transition driven by hydrophobicity. The analysis of the electronic structures and the ratio of the anti-Stokes/Stokes SERS signals suggests that the π-extended/stabilized LUMOs with varied crystalline face-on orientations provide the key properties in the chemical enhancement mechanism. A molecule-specific Raman signal enhancement is also demonstrated on a high-LUMO organic platform. Our results demonstrate a promising guidance towards realizing low-cost SERS-active semiconducting materials, increasing structural versatility of organic-SERS platforms, and advancing molecule-specific sensing via molecular engineering.

Structural Transition-Induced Raman Enhancement in Bioinspired Diphenylalanine Peptide Nanotubes

“…It should also be noted that the chemical enhancement mechanism for other organic semiconductor platforms has been identified as the efficient π-orbital overlap of the semiconductor and analyte molecules' LUMOs. 2,4 Further work is needed to obtain direct experimental evidence for similar effective spatial overlap in the FFNT−analyte systems studied here. 41−43 The band gap for annealed FFNTs (Figure S5) was estimated to be reduced from 4.4 eV (the value for FFNTs before annealing) to 3.86 eV.…”

“…Surface-enhanced Raman spectroscopy (SERS) is a powerful vibrational technique that allows for highly sensitive structural detection of low-concentration analyte molecules. , The SERS signal is dependent on the materials used to fabricate the substrate, and in the past few years, semiconductor-based SERS substrates have gained significant research interest as a means to eliminate the cost associated with noble metal nanoparticles and to exploit the chemical enhancement mechanism to improve the SERS signal through, for example, charge transfer-related processes. − …”

Indenofluorenes for organic optoelectronics: the dance of fused five- and six-membered rings enabling structural versatility

“…As another unique application for IF-based semiconductors, their micro-and nano-structured films could be prepared via modified physical vapor deposition methods and function as surface-enhanced Raman spectroscopy (SERS)active organic platforms. [156][157][158] In particular, IF derivatives without alkyl substituents, but fluorinated on the outer phenylene rings, could show ideal structural (large p-density) and electronic (low LUMOs of oÀ3.0 eV) properties for high Raman signal enhancement.…”

Flexible Two-Dimensional Vanadium Carbide MXene-Based Membranes with Ultra-Rapid Molecular Enrichment for Surface-Enhanced Raman Scattering

“…The SERS activity of noble-metal-free materials is mainly derived from the charge transfer (CT) between the material and the adsorbed molecule, namely the chemical mechanism (CM). , Compared with noble metal materials, noble-metal-free materials possess more plentiful physical and chemical properties, providing enormous possibilities for the optimization of SERS performances. In recent years, researchers have prepared a series of novel noble-metal-free SERS materials with excellent performances through optimizing the morphology, , stoichiometric ratio, , crystallinity, , and crystal orientation of non-noble metal materials, such as metal oxides, − transition metal dichalcogenides, , metal organic frameworks, , organic semiconductors, , etc. However, these enhancement strategies tend to focus on regulating the physical and chemical properties of noble-metal-free materials, while ignoring the improvement of SERS performances by molecular enrichment.…”