Photoinduced Enhanced Raman Spectroscopy with Hybrid Au@WS₂ Nanosheets

Abstract

Two-dimensional (2D) layered transition-metal dichalcogenides (2DMX 2 ) are materials with unique optoelectronic properties, high surface-tovolume ratio, and high carrier mobility. The combination of noble metal nanoparticles (MNPs) with 2DMX 2 opens new avenues in conceiving more efficient plasmonic sensors, allowing one to optimize both electromagnetic and chemical signal enhancement. Photoinduced enhanced Raman spectroscopy (PIERS) exploits the electron migration from semiconductors to MNPs, upon UV light irradiation, to further boost the chemical enhancement in the surfaceenhanced Raman scattering (SERS) of molecules deposited on hybrid 2DMX 2 − MNP nanostructures. Here, we propose a new PIERS sensor architecture based on tungsten disulfide (WS 2 ) nanosheets produced by liquid-phase exfoliation (LPE) and functionalized with citrate-stabilized Au MPNs. Electron injection from WS 2 to AuNPs is observed when the Au@WS 2 is exposed to ultraviolet light, yielding an increase of the charge carriers' density ≈ 1.8%. The PIERS sensor performances are tested by detecting 4-mercaptobenzoic acid at a concentration of 10 μM. The overall PIERS signal enhancement is ∼10 6 , whereas the photoactivation of WS 2 yields a signal improvement of factor 4 with respect to SERS from Au@WS 2 before UV irradiation. Our sensor is of low cost, easy to fabricate, and has the potential to detect biomolecules and chemical molecules at trace levels.

New Mechanism for Long Photo‐Induced Enhanced Raman Spectroscopy in Au Nanoparticles Embedded in TiO2

“…Furthermore, this enhancement is stable at least for 8 days after UV irradiation. For comparison G PIERS is equal to 7.5, 9.0, 4.5, and 3.1 in, respectively, ZnO, [ 31 ] WO 3 , [ 34 ] WS 2 , [ 29 ] and TiO 2 [ 38 ] (with AuNPs drop casted on top) (for comparison with systems including AgNP a comprehensive table is available in ref. [39]).…”

“…[ 28 ] have reported on their study of PIERS on Ag NP drop casted on lithium niobate and, in 2020, Abid et al. [ 29 ] have published their results of PIERS on AuNP drop casted on a 2D material, WS 2 . In the first case, it seems that the Raman enhancement is favored by a photocatalytic effect.…”

“…In these systems, the wavelength of the LSP resonance (LSPR) is always blue-shifted after UV irradiation. Other mechanisms have been considered in very specific systems, in 2018, Al-Shammari et al [28] have reported on their study of PIERS on Ag NP drop casted on lithium niobate and, in 2020, Abid et al [29] have published their results of PIERS on AuNP drop casted on a 2D material, WS 2 . In the first case, it seems that the Raman enhancement is favored by a photocatalytic effect.…”

Fabrication optimization and application of 3D hybrid SERS substrates

“…However, our work on 3D substrates has only focused on the 3D assembly of single-morphology nanoparticles such as gold nanooctahedra (AuNO) and silver nanorod (AgNR), which is insufficient to investigate the 3D plasmonic coupling or to prepare high-performance 3D substrates. In addition, more 3D structures as needed have been designed and studied using metals 21 or metal oxides, 22 and materials like 2D materials and polymers, such as GO, 23 WS 2 , 24 cellulose 25 and fibre. 26 Among them, 3D structures prepared with nanoparticles and 2D materials have unique advantages in providing uniform signals and long-term stability.…”

Fabrication of a Novel Electrochemical Sensor Based on Carbon Cloth Matrix Functionalized with MoO3 and 2D-MoS2 Layers for Riboflavin Determination

“…It has an indirect band-gap of 1.29 eV [ 3 ] that turns to semiconductor with a direct band-gap of 1.9 eV [ 4 ] going from bulk to a monolayer, offering an important charge carrier mobility. MoS 2 nanosheets have been fabricated via liquid phase exfoliation (LPE) by our groups and used for the detection of different biomolecules [ 5 , 6 , 7 , 8 ].…”