ORGANIC ELECTROCHEMICAL TRANSISTOR-BASED NITRATE MONITORING SENSOR FOR HYDROPONIC SYSTEM

Accurate monitoring of nutrient levels is essential in hydroponic systems to ensure optimal plant growth. Although conventional sensing methods provide reliable results, they often fall short in delivering real-time, cost-effective, and responsive solutions suitable for modern agricultural needs. This study presents the development and evaluation of an ion-selective organic electrochemical transistor (IS-OECT) designed for selective nitrate detection in hydroponic environments. The sensor features an organic PEDOT:PSS-based channel integrated with a nitrate-sensitive ion-selective membrane (ISM) containing PoT-MoS₂ nanocomposites to enhance ionic interaction and selectivity. Fabrication was carried out on a flexible PET substrate using screen-printed silver electrodes and spin-coated conductive polymer channel layer. The IS-OECT demonstrated a linear response across a wide nitrate concentration range (100–3000 ppm), achieving a sensitivity of 591.27 µA/dec and a correlation coefficient (R²) of 0.9953. The device also exhibited strong selectivity against common interfering ions and maintained reliable performance when applied to real hydroponic water samples. The sensor showed minimal interference from ions such as NO₂⁻, SO₄²⁻, Cl⁻, and Mg²⁺. Field validation using real hydroponic water samples and commercial meters (Laqua and Hanna photometer) confirmed strong correlation and an average accuracy of 78%. These findings support the sensor’s potential for scalable, low-cost, and real-time nitrate monitoring in smart agriculture.