Ultra-low cost, smart sensor based on pyrite FeS <sub>2</sub> on cellulose paper for the determination of vital plant hormone methyl jasmonate
Rinky Sha, Anand Kadu, Kazuki Matsumoto, Shigeyasu Uno, Sushmee Badhulika
Abstract
Abstract Methyl jasmonate (MeJa), a vital phytohormone plays a crucial role in plant growth and defense mechanisms to protect plants against biotic as well as abiotic stresses. Therefore, easy and accurate detection of MeJa in a user-friendly, comprehensive manner by farmers is of utmost significance in agriculture. This work reports a first of its kind ultra-low-cost pyrite FeS 2 based smart sensor on flexible paper substrate for determination of MeJa with a detection limit of 0.2 mM, excellent selectivity, reproducibility, and high sensitivity. Firstly, the electrochemical sensor based on pyrite FeS 2 exhibited a sensitivity of 412.2 μ A.mM −1 .cm −2 (R 2 = 0.971) in the physiologically relevant range of 0.25–1.5 mM and 230.4 μ A.mM −1 .cm −2 (R 2 = 0.990) in the region of 1.5–4.5 mM of MeJa. This significant enhancement in the analytical performances of the FeS 2 sensor can be ascribed to the high conductivity of the pyrite FeS 2 , large surface area resulting from its microspheres like morphology comprising of interwoven vertically grown nano-sheets and the presence of defects in FeS 2 structure. Further, wireless monitoring of MeJa was achieved by direct growth of pyrite FeS 2 on cellulose paper by hydrothermal method and its integration with the microcontroller, from where the data collected was transported to a smartphone via Bluetooth, thus facilitating remote sensing. The pyrite FeS 2 based disposable, chemi-resistive sensor displayed limit of detection of 0.68 mM and excellent sensitivity of 12.24 ± 1.4% mM −1 (R 2 = 0.96) in the range of 1–2.5 mM of MeJa. The development of such low-cost nano-material based disposable sensor is a huge step ahead in the fabrication of affordable, next-generation lab-on-chip devices for analytical applications.