Synergistic enhancement of chemical and electromagnetic effects in a Ti3C2Tx/AgNPs two-dimensional SERS substrate for ultra-sensitive detection

Abstract

Background

It is well established that surface-enhanced Raman scattering (SERS) is one of the most commonly used spectral analysis techniques in real-world applications, including chemical and biological sensing, analytical detection, and even forensics. It offers high sensitivity, high resistance to solvents, photobleaching, and limited spectrum bands. In general, SERS is caused by two mechanisms, the electromagnetic enhancement mechanism (EM) and the chemical enhancement mechanism (CM), although the exact mechanism is not yet known. For increased sensitivity, a SERS substrate based on EM coupled with CM is essential.

Results

Using electrostatic self-assembly, we fabricated many homogeneous hot spots for the substrate by evenly mixing positive charge Ag nanoparticles (AgNPs) with negative charge Ti₃C₂T_x. In addition, there is a clearly enhanced effect due to the high affinity between the tested molecule and Ti₃C₂T_x, which facilitates molecule-to-molecule charge transfer. After successfully preparing the Ti₃C₂T_x/AgNPs substrate, the R6G dye molecule was used to investigate its SERS activity. According to the results, the substrate can reach an enhancement factor of 3.8×10⁸. Furthermore, it has been demonstrated that the coupling effect between EM and CM is the main reason for the excellent performance of the Ti₃C₂T_x/AgNPs composite substrate. Based upon the results of detecting the two biomarkers, adenosine triphosphate and folic acid, the detection limits were determined to be 4.27×10^-9 M and 7.26×10^-13 M, respectively.

Significance and novelty

Two-dimensional metal carbide Ti₃C₂T_x material can be used to obtain CM in surface Raman scattering. It has been demonstrated that the combination of CM and EM with nano-precious metals can produce an extremely sensitive SERS substrate that is dependable and stable. Additionally, the Ti₃C₂T_x/AgNPs study offers a novel perspective for the advancement of the SERS coupling mechanism in addition to providing direction for realistic detection.