Noble metal (gold or silver) nanoparticles or patterned films are typically used as substrates for surface-enhanced Raman spectroscopy (SERS). Two-dimensional (2D) carbides and nitrides (MXenes) exhibit unique electronic and optical properties, including metallic conductivity and plasmon resonance in the visible or near-infrared range, making them promising candidates for a wide variety of applications. Herein, we show that 2D titanium carbide, Ti3C2Tx, enhances Raman signal from organic dyes on a substrate and in solution. As a proof of concept, MXene SERS substrates were manufactured by spray-coating and used to detect several common dyes, with calculated enhancement factors reaching ∼106. Titanium carbide MXene demonstrates SERS effect in aqueous colloidal solutions, suggesting the potential for biomedical or environmental applications, where MXene can selectively enhance positively charged molecules.

We report on one-step hybridization of silver, gold and palladium nanoparticles from solution onto exfoliated two-dimensional (2D) Ti3C2 titanium carbide (MXene) nanosheets. The produced hybrid materials can be used as substrates for surface-enhanced Raman spectroscopy (SERS). An approximate analytical approach is also developed for the calculation of the surface plasmon resonance (SPR) frequency of nanoparticles immersed in a medium, near the interface of two dielectric media with different dielectric constants. We obtained a good match with the experimental data for SPR wavelengths, 440 nm and 558 nm, respectively for silver and gold nanoparticles. In the case of palladium, our calculated SPR wavelength for the planar geometry was 160 nm, demonstrating that non-spherical palladium nanoparticles coupled with 2D MXene yield a broad, significanlty red-shifted SPR band with a peak at 230 nm. We propose a possible mechanism of the plasmonic hybridization of nanoparticles with MXene. The as-prepared noble metal nanoparticles on MXene show a highly sensitive SERS detection of methylene blue (MB) with calculated enhancement factors on the order of 105. These findings open a pathway for extending visible-range SERS applications of novel 2D hybrid materials in sensors, catalysis, and biomedical applications.

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The covalent functionalization of transition metal dichalcogenides (TMDs) has attracted significant interest because of their novel physicochemical properties for various applications. Herein, we report on amino acid (AA)‐induced solution‐processed simultaneous exfoliation and in situ covalent functionalization of exfoliated molybdenum disulfide (MoS2). Covalent functionalization of MoS2 with AAs was experimentally validated by various spectrochemical characterization and density functional theory calculations. We find that N terminal binding (NH2) of AAs with sulfur defects on exfoliated MoS2 is much more favorable than the C terminal binding (COOH). Notably, the MoS2 flakes have significantly improved biocompatibility with normal intestinal epithelial cell‐6. This exfoliation technique is presented here as general strategy; it is not limited to MoS2 and may apply to exfoliating other MX2 compounds of TMDs.