Novel method for in situ investigation into graphene quantum dots effects on the adsorption of nitrated polycyclic aromatic hydrocarbons by crop leaf surfaces

• Published in: Ecotoxicology and environmental safety Vol. 162; pp. 10 - 16
• Main Authors: Sun, Haifeng, Nan, Yanli, Feng, Ruijie, Ma, Ruiyao
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 30.10.2018
• Subjects: Adsorption; Anthracenes - analysis; Crop leaf surfaces; Crops, Agricultural - chemistry; Fluorenes - analysis; Fluorescent Dyes; Fluorometry - methods; Glycine max - chemistry; Glycine max - growth & development; Graphene quantum dots; Graphite; in situ; Nitrated polycyclic aromatic hydrocarbons; Plant Leaves - chemistry; Polycyclic Aromatic Hydrocarbons - analysis; Quantum Dots; Seedlings - chemistry; Zea mays - chemistry; Zea mays - growth & development; Crop leaf surfaces; Adsorption; Nitrated polycyclic aromatic hydrocarbons; in situ; Graphene quantum dots
• ISSN: 0147-6513; 1090-2414
• DOI: 10.1016/j.ecoenv.2018.06.059

Nitrated polycyclic aromatic hydrocarbons (NPAHs) are PAH derivatives with more toxic effects to ecosystem, and the partitioning of NPAHs in crop system constitutes the potential exposure to human health through the dietary pathway. In the present study, a novel method for in situ detection of 9-nitroanthracene (9-NAnt) and 3-nitrofluoranthene (3-NFla) adsorbed onto the leaf surfaces of living soybean and maize seedlings was established based on the fiber-optic fluorimetry combined with graphene quantum dots (GQDs) as a fluorescent probe. The detection limits for the in situ quantification of the two adsorbed NPAHs ranged from 0.8 to 1.6 ng/spot (spot represents determination unit, 0.28 cm2 per spot). Using the novel method, the effects of GQDs on the adsorption of individual 9-NAnt and 3-NFla by the living soybean and maize leaf surfaces were in situ investigated. The presence of GQDs altered the adsorption mechanism from the sole film diffusion to the combination of film diffusion and intra-particle diffusion, and shortened the time required to achieving adsorption equilibrium by 15.8–21.7%. Significant inter-species and inter-chemical variability existed in terms of the equilibrated adsorption capacity (qe) with the sequence of soybean > maize and 3-NFla > 9-NAnt. The occurrence of GQDs enlarged the qe values of 9-NAnt and 3-NFla by 22.8% versus 28.7% for soybean, and 16.2% versus 20.3% for maize, respectively, which was largely attributed to GQDs-induced expansion to the surface area for adsorbing NPHAs and the stronger electrostatic interaction between the -NO2 of NPAH molecules and the functional groups (e.g., -COOH, -OH) of GQDs outer surfaces. And, the varied enhancement degrees in the order of 3-NFla > 9-NAnt might be explained by the steric effects that resulted in the easier accessibility of -NO2 of 3-NFla to the outer surface of GQDs. Summarily, the GQDs increased the retention of NPAHs on crop leaf surfaces, potentially threatening the crop security. [Display omitted] •GQDs were used as fluorescent probe for in situ detection of NPAHs on leaf surfaces.•GQDs altered the mechanism for adsorption kinetics of NPAHs by crop leaf surfaces.•The time required to achieving equilibrium was shortened due to the presence of GQDs.•GQDs promoted the adsorption rates and equilibrated adsorption capacity of NPAHs.