▎ 摘　　要

NOVELTY - Manufacture of nanohydrogel involves mixing 100-300 mg iron chloride with 150-350 mg graphene oxide dispersion, ultrasonically processing the mixed solution for 5-15 minutes, adding a nitrogen source such as ammonium hydroxide until the suspension of the mixed solution turns brown, subjecting the suspended liquid to a hydrothermal reaction in an autoclave at 180-220° C for 20-28 hours, washing the obtained product with deionized water to obtain γ -iron oxide-nitrogen-reduced graphene oxide, in which reduced graphene oxide is doped with γ -iron oxide-nitrogen. USE - Manufacture of nanohydrogel used for electrode for sensor for detecting toxic aromatic nitrogen compound (claimed) used as raw materials in production of fertilizers, dyes, and pigments. ADVANTAGE - The method enables eco-friendly manufacture of the nanohydrogel in a single vessel, with high conversion efficiency and rapid catalytic reduction activity, electrochemical detection ability of 4-aminophenol under neutral pH conditions. The nanohydrogel electrochemical sensor has wide detection range (1 μ M-1 mM) of aromatic nitrogen compound with excellent sensitivity, repeatability and high selectivity. Various sensing parameters such as concentration of nanohydrogel, electrolyte pH and scan rate can be optimized. The nanohydrogel catalyst can continuously efficiently catalytically reduce to 4-aminophenol. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for method for detecting toxic aromatic nitrogen compounds, which involves mixing 100-300 mg iron chloride with 150-350 mg graphene oxide dispersion, ultrasonically processing the mixed solution for 5-15 minutes, adding a nitrogen source until the suspension of the sonicated mixed solution, storing the suspended liquid for 20-28 hours at 180-220° C in an autoclave, carrying out a thermal reaction, washing the obtained product with deionized water, reducing 4-nitrophenol to 4-aminophenol using the nanohydrogel and adding sodium hydrobromide until the solution of nanohydrogel mixed with 4-nitrophenol changes from yellow to colorless.