Innovative Nanosheets Propel Advancements in Sensitive Surface-Enhanced Raman Spectroscopy

In a study published in the recent edition of Applied Spectroscopy, researchers from Nanjing University of Science and Technology, led by corresponding author Rui Lu, unveiled a significant advancement in the realm of surface-enhanced Raman spectroscopy (SERS). The study focuses on the development of two-dimensional amorphous titanium dioxide/silver (a-TiO₂/Ag) nanosheets, showcasing their potential as highly sensitive SERS substrates for chemical detection.

titanium metal alloy, used in the industry, titanium is a transition metal that adds value to metal alloys because it is light and resistant | Image Credit: © RHJ - stock.adobe.com

To explore the chemical enhancement of amorphous semiconductors and elevate the sensitivity of SERS substrates, the research team employed a unique approach. Titanium dioxide (TiO₂) precursors underwent calcination at different temperatures, resulting in the generation of both crystallized TiO₂ (c-TiO₂) and amorphous TiO₂ (a-TiO₂) nanosheets. Subsequently, a two-dimensional a-TiO₂/Ag nanosheet SERS substrate was successfully fabricated through electrostatic interaction between a-TiO₂ and silver (Ag) nanoparticles.

The efficacy of the a-TiO₂/Ag nanosheets in comparison to c-TiO₂ and Ag nanoparticles alone was demonstrated using the SERS probe molecules rhodamine 6G (R6G) and malachite green (MG). The results revealed that a-TiO₂/Ag nanosheets produced highly sensitive and repeatable Raman signals. Remarkably, the detectable concentration limits for R6G and MG were determined to be 10⁻¹¹ M and 10^–10 M, respectively, showcasing the exceptional sensitivity of the substrate. The system exhibited an enhancement factor (EF) of up to 1 × 10⁸, underlining its superior performance in enhancing Raman signals.

Moreover, the study found that the limit of detection for 4-mercaptobenzoic acid and alizarin red reached an impressive 1 × 10^–8. Complementing the experimental findings, a finite-difference time-domain simulation was conducted to evaluate the magnetic field strength generated by Ag nanoparticles. The simulation results suggested that the actual EF was slightly smaller than the calculated one, emphasizing the positive impact of a-TiO₂ nanosheets on the chemical enhancement of SERS.

The innovative approach presented in this study not only advances our understanding of SERS substrates but also opens avenues for highly sensitive and reliable chemical detection. The development of a-TiO₂/Ag nanosheets holds promise for diverse applications, ranging from environmental monitoring to biomedical diagnostics. As the scientific community continues to explore new frontiers in nanomaterials, this study highlights the potential of two-dimensional amorphous nanosheets in advancing the application of SERS analytical techniques for the benefit of various industries.

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Reference

(1) Zhang, L.; Wu, S.; Lu, R.et al. Two-Dimensional Amorphous Titanium Dioxide/Silver (TiO2/Ag) Nanosheets as a Surface-Enhanced Raman Spectroscopy Substrate for Highly Sensitive Detection. Appl. Spectrosc. 2023, November 9. DOI: 10.1021/acs.analchem.3c00251