Unusual Raman Enhancement Effect of Ultrathin Copper Sulfide
Gwangwoo Kim1,2, Du Won Jeong3,4, Geonhee Lee3
1Department of Energy Engineering, Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan, 44919, Republic of Korea.
Small (Weinheim an Der Bergstrasse, Germany)
|December 28, 2023
Summary
Ultrathin covellite copper sulfide (CuS) offers a cost-effective surface-enhanced Raman spectroscopy (SERS) substrate with a high enhancement factor. This novel CuS material demonstrates selective dye detection and potential for large-scale SERS applications.
Area of Science:
- Materials Science
- Spectroscopy
- Nanotechnology
Background:
- Two-dimensional (2D) materials are investigated for surface-enhanced Raman spectroscopy (SERS) due to stability and reproducibility.
- However, 2D materials typically show lower enhancement factors (EFs) than noble metal substrates.
- Noble metal-based SERS substrates present limitations in cost and scalability.
Purpose of the Study:
- To demonstrate ultrathin covellite copper sulfide (CuS) as a high-performance, cost-effective SERS substrate.
- To investigate the enhancement mechanisms responsible for SERS activity in CuS.
- To evaluate the potential for large-scale production and application of CuS SERS substrates.
Main Methods:
- Synthesis of ultrathin CuS by sulfurizing a copper thin film at room temperature.
- Characterization of CuS SERS substrate performance, including enhancement factor (EF) measurement.
- Computational simulations using density functional theory (DFT) and time-resolved photoluminescence (TRPL) measurements to elucidate enhancement mechanisms.
- Selective detection of dye molecules (rhodamine 6G, methylene blue, safranine O) and assessment of substrate uniformity.
Main Results:
- Achieved a high EF of 7.2 × 10⁴ for the CuS SERS substrate.
- Demonstrated SERS enhancement comparable to gold substrates of similar thickness.
- DFT and TRPL results indicate charge transfer enhancement due to polar covalent bonds (Cu─S) and strong interlayer interactions.
- Successfully achieved selective detection of various dye molecules.
- Exhibited high spatial uniformity with <5% signal variation on a 4-inch wafer, suitable for large-scale production.
Conclusions:
- Ultrathin CuS is a promising, cost-effective alternative to noble metals for SERS applications.
- The charge transfer mechanism significantly contributes to the enhanced SERS signals in CuS.
- The facile synthesis and high uniformity of CuS support its scalability for practical SERS sensing.
