Monitoring soil pH variation using Polyaniline/SU-8 composite film based conductometric microsensor

• Published in: Sensors and actuators. B, Chemical Chemical, 2019-05, Vol.286, p.583-590
• Main Authors: Patil, Sheetal, Ghadi, Hemant, Ramgir, Niranjan, Adhikari, Arindam, Rao, V. Ramgopal
• Format: Article
• Language: English
• Subjects: Aniline; Bentonite; Buffer solutions; Calcium chloride; Conductometric sensors; Epoxy resins; Gold; Nanocomposites; Polyaniline-SU-8 composites; Polyanilines; Sensitivity; Silicon dioxide; Soil chemistry; Soil moisture; Soil pH; Soil water; Sulfonic acid
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2019.02.016

•Developed conductometric PANI/SU-8 composite microsensor for change in soil pH.•Sensitivities of 34 and 89 μS/pH-water achieved for Red and Bentonite soils.•For Red and Bentonite soils, sensitivities of 41 and 52 μS/pH-CaCl2 were achieved.•Enhanced response and recovery times of 10 and 30 s, achieved for soil samples.•Sensors showed excellent long term stability, repeatability and cost effectiveness. Development of Poly-aniline/SU-8 (an epoxy resin) nanocomposite film based conductometric microsensor platform to measure change in soil pH is reported. For this, poly-aniline doped with dodecylbenzene sulfonic acid (PANI-DBSA) was mixed with SU-8, and spun coated on Au-IDE patterned on Si/SiO2. The nanocomposite exhibited excellent response towards change in pH against three different conditions, namely standard buffer solutions with pH ranging from 2 to 10, Red and Bentonite soils, wherein the pH varied with water (soil moisture contents) and pH with different concentrations of calcium chloride (CaCl2) solution. The films exhibited the sensitivities of 455 and 290 μS/pH towards acidic (Lower pH) and alkaline solutions (Higher pH), respectively. The sensitivities of 34 and 89 μS/pH with water for Red and Bentonite soil samples, respectively were obtained. Importantly, for Red and Bentonite soils, the sensitivities of 41 and 52 μS/pH with CaCl2 concentration were achieved. Moreover, the sensor revealed faster response kinetics with response and recovery times of ˜10 and ˜30 s respectively. Overall, the sensor exhibited good sensitivity, excellent long term stability, high repeatability and low fabrication cost. Our results demonstrated that PANI/SU-8 composite films as a potential material for the determination of soil pH variation crucial for precision agriculture.