Detection of Nanoplastics in Ocean Water using Plasmonic Effects

Plastics production surpasses all other synthetic materials globally, with 5-13 million tons of them entering the oceans every year, posing serious environmental challenges. Plastics in the environment can be fragmented by UV irradiation and mechanical means into micro- or even nano-particles. Although nanoplastics have been detected in ocean water using techniques like mass spectrometry, they have never been visually seen and thus their morphological features are unknown, which are critical to their toxicity. Here we report the direct observation of nanoplastics in ocean water around the world leveraging a unique shrinking surface bubble deposition (SSBD) technique. SSBD concentrates suspended nanoplastic particles onto a surface, allowing direct visualization using electron microscopy. With the plasmonic nanoparticles co-deposited in the SSBD process, surface-enhanced Raman spectroscopy effect is enabled for chemical identification of trace amount of nanoplastics deposited on the surface. From the water samples collected from locations on the coastlines of China, South Korea, and the United States, and deep (>300 m) in the Gulf of Mexico, we observed nanoplastics with a variety of compositions, including polycaprolactam (Nylon), polystyrene (PS), and polyethylene terephthalate (PET) – all commonly used in daily consumables (e.g., textiles, coffee cup lids and water bottles). The plastic particles we found possessed diverse morphologies, such as nanofibers, nanoflakes, and ball-stick nanostructures. These diverse nanoplastics may have profound impacts on marine organisms, and our results can provide important information for appropriately designing their toxicity studies.