Visualizing undyed microplastic particles and fibers with plasmon-enhanced fluorescence

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2022-08, Vol.442, p.136117, Article 136117
• Main Authors: Wei, Xin-Feng, Rindzevicius, Tomas, Wu, Kaiyu, Bohlen, Martin, Hedenqvist, Mikael, Boisen, Anja, Hakonen, Aron
• Format: Article
• Language: English
• Subjects: Analysis method; Analysis methods; Biodegradable polymers; Elastomers; Electromagnetic fields; Enhanced fluorescence; Fluorescence enhancement; Fluorescence imaging; Fluorescence microscopy; Global production; Global use; Microplastic; Microplastic particles; Microplastics; NanoPillar; Plasmonic nanostructures; Substrates; Water samples
• ISSN: 1385-8947; 1873-3212; 1873-3212
• DOI: 10.1016/j.cej.2022.136117

[Display omitted] •Plasmon-enhanced fluorescence (PEF) was used for microplastics detection.•The fluorescence microscopy imaging revealed remarkable fluorescence enhancement.•The enhancement factor on the PEF substrates was estimated to 70.•Even particles too small to be imaged with common microscopy was lit up.•The limit of detection was estimated to 0.35 femtograms. Despite widespread awareness that enormous consumption of plastics is not sustainable, the global production and use of plastics continue to grow. This generates vast amounts of plastic waste and microplastics, ending up e.g., in the marine environment. There are serious challenges in detecting and measuring microplastics, especially in highly diluted natural samples. Here, a new alternative microplastic detection method based on plasmon-enhanced fluorescence (PEF) was developed and tested using fluorescence microscopy. In particular, gold nanopillar-based substrates, displaying (i) high electromagnetic field enhancement, and (ii) surface superhydrophobicity and high adhesion properties, were utilized to enhance the fluorescence emission signal from microplastics in water samples. The fluorescence microscopy imaging revealed remarkable fluorescence enhancement by the PEF substrates on the microplastic particles and fibers with different sizes of both conventional, low-density polyethylene, and biodegradable poly (butylene adipate-co-terephthalate). The limit of detection and quantification by this method was estimated to be as low as 0.35 and 1.2 femtograms, respectively. The observed fluorescence enhancement of the gold nanopillar substrates for the microplastics was ca. 70 times greater than the case of having the microplastics on a glass substrate. Additionally, 3D FEM simulations were performed to further investigate the system's electromagnetic field distribution near the nanostructures. This new method makes undyed microplastics visible in fluorescence microscopy, even particles and fibres too small to be imaged with conventional light microscopy. This can be a great tool for microplastic research, helping us to detect, study, understand microplastic dynamics in water based systems.