1T′ Transition Metal Telluride Atomic Layers for Plasmon-Free SERS at Femtomolar Levels

Abstract

Plasmon-free surface enhanced Raman scattering (SERS) based on the chemical mechanism (CM) is drawing great attention due to its capability for controllable molecular detection. However, in comparison to the conventional noble-metal-based SERS technique driven by plasmonic electromagnetic mechanism (EM), the low sensitivity in the CM-based SERS is the dominant barrier toward its practical applications. Herein, we demonstrate the 1T' transition metal telluride atomic layers (WTe and MoTe) as ultrasensitive platforms for CM-based SERS. The SERS sensitivities of analyte dyes on 1T'-W(Mo)Te reach EM-comparable ones and become even greater when it is integrated with a Bragg reflector. In addition, the dye fluorescence signals are efficiently quenched, making the SERS spectra more distinguishable. As a proof of concept, the SERS signals of analyte Rhodamine 6G (R6G) are detectable even with an ultralow concentration of 40 (400) fM on pristine 1T'-W(Mo)Te, and the corresponding Raman enhancement factor (EF) reaches 1.8 × 10 (1.6 × 10). The limit concentration of detection and the EF of R6G can be further enhanced into 4 (40) fM and 4.4 × 10 (6.2 × 10), respectively, when 1T'-W(Mo)Te is integrated on the Bragg reflector. The strong interaction between the analyte and 1T'-W(Mo)Te and the abundant density of states near the Fermi level of the semimetal 1T'-W(Mo)Te in combination gives rise to the promising SERS effects by promoting the charge transfer resonance in the analyte-telluride complex.

High SERS Sensitivity Enabled by Synergistically Enhanced Photoinduced Charge Transfer in Amorphous Nonstoichiometric Semiconducting Films

“…When excited by the incident photons, the narrow bandgap, the oxygen vacancy–associated energy levels, and the upshifted Fermi levels can all give rise to the high charge transition probabilities 17a. The high electronic DOS near the Fermi level also allows that the adsorbed R6G molecules well couple to this amorphous nonstoichiometric SERS substrate . Moreover, the amorphous phase metal oxide typically causes dangling bonds and band tails, which could lead the energy of the system to a metastable state, leading to much higher efficiency of surface electron escaping and transferring 19a…”

“…Creating oxygen vacancies in semiconducting oxide has been verified as an efficient approach to enhance the PICT resonance by offering additional oxygen defect levels within the bandgap and strong exciton resonance . Moreover, the semiconducting SERS materials with amorphous phase or high electronic DOS near the Fermi level could also lead to efficient PICT by offering effective routes of charge escaping and transferring as well as strong vibronic coupling of semiconducting SERS materials and analytes. Here, we realize the combination of all these factors in amorphous nonstoichiometric WO 3− x films, and speculate that the PICT process could be synergistically enhanced.…”

Alloy Engineering in Few‐Layer Manganese Phosphorus Trichalcogenides for Surface‐Enhanced Raman Scattering

“…Recent years, with the discovery of new 2D materials, multiphase TMDs, transition metal oxides (TMOs), and MXenes were fabricated as SERS‐active substrates. Among them, semimetal 1T′‐W(Mo)Te 2 could detect 10 −15 m of Rhodamine 6G (R6G) . Metallic NbS 2 could amplify the Raman signals of methylene blue with a concentration as low as 10 −14 m .…”

Recent Advances in 2D Inorganic Nanomaterials for SERS Sensing

“…In this context, other 2D materials such as hexagonal boron nitride (h‐BN), orthorhombic black phosphorus, moly‐bdenum disulfide (MoS 2 ), triclinic rhenium disulfide (ReS 2 ), gallium selenide (GaSe), tungsten diselenide (WSe 2 ), tungsten telluride (WTe 2 ), and titanium carbide (TiC) have been investigated to address the challenges. For example, the stable phase of 1T‐WTe 2 exhibited an ultralow detection (femtomolar level concentration) toward R6G with promising aging stability, demonstrating that 2D layered materials are a feasible SERS material for real‐time applications.…”