Detection of microplastics through an optical sensor array using nano-graphene oxide and fluorophore conjugates

Microplastics (MPs) are degraded plastic products that significantly contribute to global aquatic pollution due to the widespread use of synthetic plastic materials. These tiny, degraded plastics are now commonly found in drinking water, food, and soil and even inside aquatic and non-aquatic organisms. This highlights the urgent need for effective methods to detect and classify these micropollutants in everyday samples. Herein, we have employed a highly stable and cost-effective 2D-nanomaterial, nano-graphene oxide (nGO), as a receptor element to discriminate various types of MPs. In a two-step signal output strategy, at first, MPs are treated with different organic fluorophores to generate varied fluorescence responses. Subsequently, nGO is added to further modulate these output signals. By utilizing the optimized sensor array, six different types of MPs, collected through thermal and mechanical treatments, were well discriminated at a concentration corresponding to an absorbance of A_{260 nm} = 0.025. The sensor's applicability was also evaluated in river, lake, and tap water and in the presence of environmental interferents. The system also detected the presence of MP leachates in water stored in different plastic containers at room temperature. Packaged bottled water, with varying manufacturing dates, also showed significant responses to the sensor array at a very low concentration. This indicates that the designed sensor array can effectively verify water quality by sensing microplastic contamination.