Nitrate concentration Measurement in Cress Plant Using a Colorimetric Sensor based on Gold nanoparticles

Due to the necessity of regular and rapid evaluation of nitrate, the development of methods with the ability to detect this compound accuratly and simple is important. Nowadays, colorimetric methods have received much attention due to their ability to detect simple and visual. In this study, which was carried out in 2022 with cooperation of Tehran university and the Agricultural Biotechnology Research Institute, a colorimetric method based on etching of gold nanorods for qualitative and quantitative detection of nitrate was presented. the measurement of nitrate ions (after reduction of nitrate to nitrite by zinc powder) at room temperature is possible by changing the size of the plasmonic nanoparticles and subsequently generating measurable signals, including spectral and color changes. Under optimal conditions, a good linear relationship between nitrate concentration and colorimetric response in the range of 0.5 to 3.0 mM (R2=0.995) with a detection limit of 173.3 μM was found. Also, considering that vegetables, especially leafy vegetables, have a high potential in nitrate absorption, in this research cress plant was used as an indicator plant to investigate the efficiency of the sensor in determining the nitrate of leafy plants. Recovery values for nutrient solution and cress tissue samples was in the range of  94.4 to 101.9 and 93.4 to 98.5%, respectively, and relative standard deviation (RSD) for all samples was calculated below 2.1%. As a result, the presented method in this study provides the possibility of monitoring the actual level of nitrate in cress plant samples.