Exploring the Ultralow Limit of Detection for Aromatic/Hydrophobic Nanoplastics with Ultrasmall Size Enables an LSPR Optical Microfiber

The pervasive invasion of small-sized environmental nanoplastics into organisms can cause long-term toxicity to cells and tissues. Operando monitoring of these contaminants is therefore critical for early environmental warning. Although current state-of-the-art techniques can be applied to detect small-sized nanoplastics, their limits of detection (LOD) cannot meet the requirements of sensing applications in real-world samples. Herein, we propose an optical multimode microfiber coupled with an excited localized surface plasmon resonance (LSPR) enhancement effect, which can realize the ultrasensitive detection of 30 nm polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET) nanoplastics with LOD results of 3.26 × 10^-12 mg/mL, 7.71 × 10^-12 mg/mL, and 7.34 × 10^-14 mg/mL, respectively. The results are 1∼3 orders of magnitude lower than those of existing state-of-the-art methods. The optical fiber sensor can also detect three aromatic/hydrophobic nanoplastics well in real, complicated environmental water samples. Thus, this work establishes a novel framework for detecting a class of aromatic/hydrophobic nanoplastics with ultrasmall sizes.