A facile and one-step colorimetric detection of hydrazine has been developed for the first time during the formation of size-controlled amidosulfonic acid capped gold nanoparticles (AA-AuNPs). Hydrazine served not only as a target analyte but also a reductant to react with chloroauric acid (HAuCl4). In order to obtain size-controlled gold nanoparticles (AuNPs), the amidosulfonic acid (AA) was used as a stabilizer. In the presence of AA, different aggregation states of AuNPs, which exhibited distinct color changes, were obtained by varying the concentration of hydrazine. Furthermore, the changes of color resulted in different ultraviolet visible (UV-Vis) absorptions, which realized quantitative analysis of hydrazine. The detection results indicated that the proposed method exhibited good performance for hydrazine determination with a wide linear range from 1.0 × 10−7 to 2.53 × 10−4 M (r = 0.9915) and a low detection limit of 8.53 × 10−8 M. The proposed method was successfully used in detecting hydrazine in various real water samples with high selectivity, sensitivity and reliability. Even outdoors, the proposed method could also be applied in real time to determine whether the hydrazine concentration was permitted or not in water samples via the visible color change.
