Surface-enhanced Raman scattering (SERS) has been widely used for the detection of molecules with ultra-low concentrations, in which the weak Raman signals can be significantly boosted. The noble metal substrate and the semiconductor material-based SERS-active substrate both have disadvantages in realizing a substantial SERS effect.

Adopting semiconductor materials with light-trapping architectures as the surface-enhanced Raman spectroscopy (SERS)-active substrate has drawn increasing attention. However, the fabrication of the semiconductor SERS-active substrate is complicated. The methods normally result in non-uniform and isolated particles/flakes, which have fundamental difficulties to meet the practical needs in high performance and reliable SERS substrate.  

A research team led by Dr. CHEN Ming from the Shenzhen Institutes of Advanced Technology (SIAT) of the Chinese Academy of Sciences reported a high performance semiconductor-based SERS substrate based on self-assembled SnSe₂ nanoplate arrays. The researchers demonstrated that SnSe₂ nanoplate arrays (NPAs) via self-assembled growth could serve as a uniform, high performance and reliable SERS substrate.

The cavity of SnSe₂ NPAs could trap light efficiently (~96%) and thus improve the enhancement factor. Benefiting from the synergy effect of charge-transfer process and enhanced light trapping, the resulting SERS substrate based on pure SnSe₂ NPAs showed an ultralow detection limit (1×10-12 M), high enhancement factor (1.33 ×106) and good uniformity (relative standard deviations down to 7.7%), demonstrating one of the highest sensitivities amongst the reported semiconductor SERS substrates.

Furthermore, the researchers systematically investigated the effect of different SnSe₂ structural configurations (planar vs. cavity), the height and tilt angle of SnSe₂ NPAs on the performance of SERS detection. They discovered that the SERS performance was strongly dependent on both the light-trapping ability and absorption loss.

They believe the results not only provide an effective strategy to obtain tunable, uniform and high performance SERS substrate, but also lead to further understanding of designing 3D light trapping architectures. 

The study titled "Tunable 3D light trapping architectures based on self-assembled SnSe2 nanoplate arrays for ultrasensitive SERS detection" was published in Journal of Materials Chemistry C. The paper was also selected as 2019 Journal of Materials Chemistry C HOT Papers.

Figure 1. The tunable light trapping structure based on self-assembled SnSe₂ nanoplate arrays (up to ~96%) (Image by CHEN Ming)