Researchers Unveil Novel Findings in Surface-Enhanced Photoluminescence Spectroscopy

Surface-enhanced photoluminescence spectroscopy can help elucidate further insight into how optical nanoantennas and their properties change across different configurations, according to a recent study published in Nanotechnology (1).

Optical nanoantennas have long been recognized for the ability to enhance and confine the optical field at the nanoscale, a feature that is critical for a variety of applications (1,2). The study, conducted by researchers at Yanshan University in Qinhuangdao, China, investigates the specifics of this enhancement, utilizing the finite element method to quantitatively analyze the properties of the plasmonic field, quantum yield, Raman scattering, and fluorescence within the Au bowtie nanoantenna (1).

Medical concept in the field of nanotechnology. Genetic engineering and the use of nanorobots to replace part of the DNA molecule. 3D rendering. | Image Credit: © k_e_n - stock.adobe.com

This study, led by Weifeng Peng and Yong Wei, employed the finite element method (FEM) to conduct their theoretical investigation. FEM is a computational and mathematical technique that allows for precise modeling of complex structures by breaking complex structures down into smaller pieces (3). This method can provide a detailed understanding of how the optical enhancement properties change across different configurations of the nanoantenna, particularly in the visible to near-infrared (NIR) spectral regions (1).

One of the key components to this study was the review of the nonlocal dielectric response. The nonlocal dielectric response is a phenomenon that affects how the electromagnetic field interacts with the material on a very small scale, particularly when the gap distance is less than 3 nm (1). The researchers were able to show in their study that this response significantly reduces the quantum yield and fluorescence intensity (1). However, the study also shows that a substantial excitation field can mitigate this fluorescence quenching, thereby enhancing the overall fluorescence intensity (1).

By altering the configuration of the Au bowtie nanoantenna, the researchers were able to achieve remarkable enhancements in both Raman and fluorescence spectroscopy. The study reported that the maximum enhancement of surface-enhanced Raman spectroscopy (SERS) can be increased by 9 to 10 magnitude orders in the visible and NIR regions, respectively (1). Similarly, fluorescence enhancement can be improved by 3–4 magnitude orders (1).

The ability to achieve maximum spatial resolutions of 0.8 nm for Raman spectroscopy and 1.5 nm for fluorescence opens new advancement opportunities in the fields of photodetection, environmental science, and biosensing. For photodetection, the ability to obtain maximum spatial resolutions means more sensitive and accurate sensors (1). In environmental science, this innovation could lead to better detection of pollutants at the nanoscale (1). In biosensing, the applications range from more precise diagnostic tools to enhanced imaging techniques (1). Nonlinear optics could also benefit from these advancements, potentially leading to new developments in optical computing and communications.

This study offers new insight into the mechanisms behind fluorescence enhancement in nanoantennas. Through the results, the research team also suggested practical guidelines for designing new nanoantennas with optimized configurations (1). The research represents a step forward in the application of SERS and fluorescence technologies, extending their usefulness from the visible to the NIR spectrum.

References

(1) Pei, H.; Peng, W.; Zhang, J.; et al. Surface-enhanced Photoluminescence and Raman Spectroscopy of Single Molecule Confined in Coupled Au Bowtie Nanoantenna. Nanotechnol. 2024, 35 (15), 155201. DOI: 10.1088/1361-6528/ad1afd

(2) Duarte, F.; Torres, J. P. N.; Baptista, A.; Lameirinhas, R. A. M. Optical Nanoantennas for Photovoltaic Applications. Nanomaterials (Basel) 2021, 11 (2), 422. DOI: 10.3390/nano11020422

(3) Ansys, What is Finite Element Analysis (FEA)? Ansys.com. Available at: https://www.ansys.com/simulation-topics/what-is-finite-element-analysis#:~:text=FEM%20uses%20math%20to%20break,divide%2C%20then%20conquer%20engineering%20problems. (accessed 2024-08-07).