Abstract
Two-dimensional (2D) transition-metal dichalcogenides have become promising candidates for surface-enhanced Raman spectroscopy (SERS), but currently very few examples of detection of relevant molecules are available. Herein, we show the detection of the lipophilic disease marker β-sitosterol on few-layered MoTe2 films. The chemical vapor deposition (CVD)-grown films are capable of nanomolar detection, exceeding the performance of alternative noble-metal surfaces. We confirm that the enhancement occurs through the chemical enhancement (CE) mechanism via formation of a surface-analyte complex, which leads to an enhancement factor of ≈104, as confirmed by Fourier transform infrared (FTIR), UV-vis, and cyclic voltammetry (CV) analyses and density functional theory (DFT) calculations. Low values of signal deviation over a seven-layered MoTe2 film confirms the homogeneity and reproducibility of the results in comparison to noble-metal substrate analogues. Furthermore, β-sitosterol detection within cell culture media, a minimal loss of signal over 50 days, and the opportunity for sensor regeneration suggest that MoTe2 can become a promising new SERS platform for biosensing.
Highlights
Layered two-dimensional (2D) transition-metal dichalcogenides (TMDCs) have emerged as an important class of materials that could bring transformative changes to the ways we fabricate and operate future electronic devices and sensors.[1,2] Sensing applications, such as surface-enhancedRaman spectroscopy (SERS), rely on strong interactions between an analyte and a surface, making TMDCs well suited for SERS as their atomically flat surfaces facilitate homogeneous distribution of analytes.[3]
Utilizing β-sitosterol as a lipophilic molecule of interest requires a comprehensive assessment of various factors, which we carefully investigated in this study
Previous research demonstrated that modification of gold gratings with lipophilic functional groups (LFGs) allows for sitosterol sensing at millimolar concentration but overlapping of Raman peaks between LFGs and the analyte has limited gold gratings application in trace sensing.[15]
Summary
Layered two-dimensional (2D) transition-metal dichalcogenides (TMDCs) have emerged as an important class of materials that could bring transformative changes to the ways we fabricate and operate future electronic devices and sensors.[1,2] Sensing applications, such as surface-enhanced. The enhancement in these modes has been attributed to the high-scattering cross section of the metal, which contributes to the intensity of Raman bands from the surface complex.[44,45] based on ζ-potential studies (Figure S5), we hypothesize that a complex is formed due to a surface−dipole interaction In this case, the Raman enhancement would depend on the ability of the analyte molecule to polarize and to accept π-backbonding (significant stabilization of the HOMO−LUMO gaps)[44] upon contact with MoTe2. It was demonstrated that CHEM mechanism could lead to an EF in the range 10−1000 by changing the functional groups on the analyte.[44,47] The sensing of cholestane, β-sitosterol, squalene, and 4-andostene-3,17-dione at 10−6 M concentrations on 1T′-MoTe2 demonstrates the increase of Raman signal intensity (EF could not be compared due to a difference in band enhancement in all molecules) within this range of molecules. The results suggest that only the irradiation of the 780 nm laser during Raman measurements facilitates more active electron and charge transfer processes, revealing a change in the excitation energy of the surface complex formed.[48]
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