Atomically Thin TaSe₂ Film as a High‐Performance Substrate for Surface‐Enhanced Raman Scattering

Abstract

An atomically thin TaSe2 sample, approximately containing two to three layers of TaSe2 nanosheets with a diameter of 2.5 cm is prepared here for the first time and applied on the detection of various Raman‐active molecules. It achieves a limit of detection of 10−10 m for rhodamine 6G molecules. The excellent surface‐enhanced Raman scattering (SERS) performance and underlying mechanism of TaSe2 are revealed using spectrum analysis and density functional theory. The large adsorption energy and the abundance of filled electrons close to the Fermi level are found to play important roles in the chemical enhancement mechanism. Moreover, the TaSe2 film enables highly sensitive detection of bilirubin in serum and urine samples, highlighting the potential of using 2D SERS substrates for applications in clinical diagnosis, for example, in the diagnosis of jaundice caused by excess bilirubin in newborn children.

Grain-Boundary-Induced Ultrasensitive Molecular Detection of Graphene Film

“…In order to illustrate the PICT process, the band structure analysis was further conducted. The HOMO and LUMO levels for the R6G molecules are −5.7 and −3.4 eV, respectively . According to the Kelvin probe force microscopy (KPFM) measurement results (Figure S11), the work function of Gr and NG-2.35 at% GBs is 4.99 and 5.16 eV, respectively.…”

“…As shown in Figure 3e, two PICT transitions between the molecules and substrate occur including the transition from the HOMO of R6G to the Fermi level of Gr or NG (μ i-CT ), and the transition from the Fermi level of Gr or NG to the LUMO of R6G (μ k-CT ). 35 However, the former transition contributed little to the GERS performance due to the much lower energy (0.71 and 0.54 eV) than the 532 nm laser energy (2.33 eV). 34 In contrast, the energy of PICT from the Fermi level of NG to the LUMO of In order to further verify the CM effect, equal amounts of R6G molecules with a thickness of 4 Å were deposited onto the surface of graphene films with different P GB 's by thermal evaporation and Raman signals of R6G molecules on graphene films were recorded.…”

“…In view of the variation of the matrix element H kl ′ , which originates from the local symmetry-related perturbation induced by the interface dipole interaction, H kl ′ can be considered as an invariant when graphene materials act as SERS substrate. Hence, the electron transition probability is proportional to the DOS near the Fermi level. − To investigate the influence of GBs on electron transition probability, we calculated the DOS of pristine Gr and four kinds of representative GBs (Figures b,c and S10). As shown in Figure d, all of four kinds of representative GBs exhibit more electronic states near the Fermi level than pristine Gr.…”

“…According to the Kelvin probe force microscopy (KPFM) measurement results (Figure S11), the work function of Gr and NG-2.35 at% GBs is 4.99 and 5.16 eV, respectively. As shown in Figure e, two PICT transitions between the molecules and substrate occur including the transition from the HOMO of R6G to the Fermi level of Gr or NG (μ i‑CT ), and the transition from the Fermi level of Gr or NG to the LUMO of R6G (μ k‑CT ) . However, the former transition contributed little to the GERS performance due to the much lower energy (0.71 and 0.54 eV) than the 532 nm laser energy (2.33 eV) .…”

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.…”