▎ 摘　　要

NOVELTY - Preparing three-dimensional flower-type nano composite nickel(II) oxide/poly(diallyldimethylammonium chloride-reduced graphene oxide (NiO/PDDA-RGO) comprises e.g. (1) dissolving 15-50 mg graphene oxide in 15-25 ml de-ionized water and sonicating for 0.5-3 hours to obtain a dispersion of graphene oxide, placing in container, taking concentration of 1-2 mg/ml graphene oxide dispersion 5-10 ml in reaction bottle, adding 8-12 wt.% PDDA, 50-60 mu l and mixing, adjusting pH with concentrated ammonia 9-10, adding 40-55 mu l 80% hydrazine hydrate, stirring, placing reaction flask in 50-80 degrees C, water bath and heating for 3-4 hours, cooling, washing and drying synthesized material to obtain PDDA-RGO, (2) adding 0.06-0.07g ammonium fluoride, 0.2-0.3 g nickel(II) nitrate hexahydrate, 0.3-0.5 g urea to mixed solution of 20 ml distilled water and 0.635 ml ethylene glycol, stirring solution for 0.5-1 hours, and transferring solution to 50 ml reaction kettle and reacting at 130-150 degrees C for 8-10 hours. USE - The preparing three-dimensional flower-type nano composite nickel(II) oxide/poly(diallyldimethylammonium chloride-reduced graphene oxide is useful in detection of nitrite (claimed). ADVANTAGE - The method: has high sensitive, good application prospects in environmental and food analysis fields, and achieves selective detection of nitrite in complex environments. DETAILED DESCRIPTION - Preparing three-dimensional flower-type nano composite nickel(II) oxide/poly(diallyldimethylammonium chloride-reduced graphene oxide (NiO/PDDA-RGO) comprises (1) dissolving 15-50 mg graphene oxide in 15-25 ml de-ionized water and sonicating for 0.5-3 hours to obtain a dispersion of graphene oxide, placing in container, taking concentration of 1-2 mg/ml graphene oxide dispersion 5-10 ml in reaction bottle, adding 8-12 wt.% PDDA, 50-60 mu l and mixing, adjusting pH with concentrated ammonia 9-10, adding 40-55 mu l 80% hydrazine hydrate, stirring, placing reaction flask in 50-80 degrees C, water bath and heating for 3-4 hours, cooling, washing and drying synthesized material to obtain PDDA-RGO, (2) adding 0.06-0.07g ammonium fluoride, 0.2-0.3 g nickel(II) nitrate hexahydrate, 0.3-0.5 g urea to mixed solution of 20 ml distilled water and 0.635 ml ethylene glycol, stirring solution for 0.5-1 hours, and transferring solution to 50 ml reaction kettle and reacting at 130-150 degrees C for 8-10 hours, centrifugally washing and drying obtained light blue liquid at end of the reaction at 80 degrees C for 2 hours to obtain a light blue powder, three-dimensional flower-shaped nickel(II) oxide is obtaining by heating crucible with powder in a muffle furnace at a heating rate of 5-1 degrees C/minutes, and heating at 380-400 degrees C for 2-3 hours, and (3) ultrasonicating synthesized 10-30 mg PDDA-RGO in 10-30 ml distilled water for 0.5-1 hours, after dispersing completely and homogenizing, adding 1.25-20 mg synthesized three-dimensional flower-shaped nickel(II) oxide and sonicating at room temperature for 2-3 hours to obtain a three-dimensional flower-shaped nano composite NiO/PDDA-RGO. INDEPENDENT CLAIMS are also included for: (1) three-dimensional flower-type nano composite nickel(II) oxide/poly(diallyldimethylammonium chloride-reduced graphene oxide; (2) preparing NiO/PDDA-RGO modified electrode comprising polishing bare glassy carbon electrode surface with 0.05 mu m alumina particles, and rinsing with ultrapure water and ethanol until a mirror surface is obtained and drying, pipette 6-8 mu l NiO/PDDA-RGO onto surface of the glassy carbon electrode (GCE), and drying under an infrared lamp, i.e., to obtain NiO/PDDA-RGO modified electrode; and (3) detecting nitrite comprises preparing series of standard solutions of sodium nitrite with different concentrations, using NiO/PDDA-RGO modified electrode prepared as working electrode, and the platinum wire electrode as counter electrode, the silver-silver chloride electrode is the reference electrode, placing three electrodes in solution using 0.1 M phosphate buffer (pH = 5) as electrolyte, using current-time method to record peaks corresponding to different concentrations of sodium nitrite, currently according to peak current value and concentration of sodium nitrite in the corresponding standard solution, and drawing standard curve of current versus concentration.