JEOS RP ISSN03 | Page 291

J. Eur. Opt. Society-Rapid Publ. 2026, 22, 28 Ó The Author( s), published by EDP Sciences, 2026 https:// doi. org / 10.1051 / jeos / 2026022 Available online at: https:// jeos. edpsciences. org

EOSAM 2025 Guest editors: Omar El Gawhary, Stefan Witte, Ignacio Moreno

Journal of the European Optical Society-Rapid Publications

RESEARCH ARTICLE

Enhancing the fluorescence of low quantum yield fluorophores using plasmonic metasurfaces

National Institute for Research and Development in Microtechnology – IMT Bucharest, 126A, Erou Iancu Nicolae Street, 077190, Voluntari, Ilfov, Romania

Received 30 January 2026 / Accepted 4 March 2026

Abstract. Metasurfaces represent an innovative category of optical surfaces that can be engineered to exhibit distinctive properties that are not observed in conventional materials. It has been demonstrated that these structures exhibit robust light-matter interactions at the nanoscale, which renders them a promising solution for enhancing the sensitivity of various biomedical sensing technologies. This work presents a versatile approach for enhancing the broadband spectral emission of various fluorophores. The approach involves developing largearea, lithography-free plasmonic platforms without tailoring the geometry of the metasurface to a specific chromophore. The investigation encompasses the fluorescence behaviour of low quantum yields fluorophores such as Crystal Violet, Nile Red, and Rose Bengal, dispersed in ethanol solutions and coated onto the metallic arrays with random configuration. The results indicate that metallic nanostructures efficiently support plasmonmediated fluorescence enhancement, and the degree of this enhancement depends strongly on both the fluorophore type and the metal layer thickness. The highest fluorescent enhancement factor was obtained for Crystal Violet on silver metasurfaces.

Keywords: Plasmonic metasurface, Lithography-free platforms, Fluorescence enhancement, Nanophononics, Low quantum yield fluorophore.

1 Introduction

Recent advances and technological innovations in the field of plasmonics have led to a variety of exciting applications that address important sensing challenges. In this context, extensive studies are conducted on fluorescence for biosensing purposes. The fluorescence analysis method is known for properties like easiness, high sensitivity and selectivity, and short response time [ 1, 2 ]. A particularly important topic in this research area is the enhancement of fluorescence for low-quantum-yield fluorophores which have applications in biomedical imaging [ 3 ], sensing [ 4 ], and optoelectronics [ 5 ]. These materials exhibit strong absorption, environmental sensitivity, or useful photochemistry; however, their practical use is frequently limited by weak emission and rapid photodegradation under high excitation irradiance. Therefore, various methods have emerged to amplify fluorescence signals for increasing detection [ 6 – 8 ]. Plasmonic metamaterials have been shown to be a promising solution that utilizes the intense interaction between light and matter at the nanoscale to increase the sensitivity of various

* Corresponding author: roxana. tomescu @ imt. ro biomedical spectral sensing technologies. Moreover, metalenhanced fluorescence( MEF) is a method of enhancing fluorescence signals. Specifically, when a chromophore molecule is in close proximity to metal nanostructures, its fluorescence is enhanced due to the intensification of the localized electromagnetic field specific to plasmonic metasurfaces [ 9, 10 ]. However, this method has an important disadvantage: the fluorescence signal is quenched if the fluorophore is in direct contact with the metallic nanostructure. To overcome this problem, an ultra-thin film is required to act as a spacer.

Current research emphasizes the development of metasurface arrays that are thin, easy to fabricate, and capable of manipulating wave propagation both at the interface and in free space. These properties demonstrate a significant potential for enhancing fluorescence detection, making them invaluable tools in biosensing applications [ 11, 12 ]. Although, the devices tailored for specific resonance achieve sharp field maxima [ 13 ], the technological processes required for their fabrication are complex and expensive. Meanwhile, the random morphology metasurfaces offer a wide range emission due to disordered dispersers supporting various localized plasmon modes that overlap. This improves

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