In this paper, an optimized memristor emulator circuit is designed, by using nine MOSFET transistors and a ground capacitor. Our area- and power-optimized emulator circuit can be used for basic data storage and processing at the monitoring edge, in real-time applications. The memristor shows a nonlinear voltage–current relationship, but no multiplier circuit provides the memristor’s nonlinear characteristics. As a result, the proposed memristor emulator has a very low chip area. The memristor circuit is designed in LTSpice, using 16 nm and 45 nm CMOS technology parameters, and the operating voltage is ±0.9 V. In this research, the theoretical derivations are validated using the simulated results of the memristor emulator circuit using different frequencies, capacitors, and input voltages in SPICE simulations.

Inorganic nitrate (NO ₃ ⁻ ) is ubiquitous in the environment and has become a center of attention in industrial and agricultural sectors, but it is regarded as a major contaminant in water and soil. In this letter, we present a flexible, cost-effective amperometric sensor that is screen-printed on a biodegradable cellulose substrate. The sensor's working electrode was functionalized with Cu nanoclusters, followed by the application of a solid-state ion-selective membrane (ISM), enabling continuous monitoring of nitrate levels in the water. The optimized electrodeposition of Cu nanoclusters served as a metal catalyst to reduce nitrate ions, whereas the optimized ISM cocktail selectively detected nitrate ions. The sensor showed a wide linear detection range from 1 (16 μ M) to 100 ppm (1.6 mM) with a high sensitivity of 684 nA/ppm. Selectivity tests conducted with common interfering substances (Na ⁺ , Cl ⁻ , SO ₄ ⁻ , HCO ₃ ⁻ , and NO ₂ ⁻ ) showed minimal impact on nitrate sensing. The sensors also showed reproducible and stable responses up to the first 3 days. The mechanical durability of the sensor was also assessed using a customizable bending setup. In addition, Fourier transform infrared spectroscopy (FTIR) results demonstrated the gradual degradation of the cellulose substrate into the soil, highlighting the attainment of sustainable and circular sensing capabilities.

Excessive fertilizer application leads to inefficient resource utilization, increased costs, and environmental pollution, while reduced fertilizer application can lower crop yield and productivity. Yet, farmers lack real-time soil nitrate monitoring tools, as existing field detection methods compromise sensitivity, stability, deployment simplicity, or real-time data transmission, hindering sustainable nutrient management. This study presents a comprehensive solution that tackles these challenges by integrating an in situ potentiometric nitrate sensor with a dual-band wireless data link for communication from underground to aboveground. The potentiometric nitrate sensor, featuring a poly(3-octyl-thiophene) and molybdenum disulfide nanocomposite transducer layer, demonstrates high sensitivity of −82.2 mV/dec, a detection limit of 6.34 ppm, and stable operation at soil depths of 5 cm, 10 cm, and 30 cm for a continuous 10 days. Its resilience to even low soil moisture levels (10%, 20%, and 30%) ensures reliable performance across diverse field conditions. To facilitate efficient underground-to-aboveground data transmission, a custom dual-band antenna operates at 850 MHz and 2.45 GHz, achieving realized gains of 2.03 dBi and 2.38 dBi, respectively. The lower frequency band ensures robust signal penetration, while the higher band provides faster data transmission for real-time monitoring. Experimental results validate reliable wireless data transfer with less than 1% error at distances of 2 m and 4 m. This system integrates advanced sensing and communication technologies, offering scalable, energy-efficient solutions to enhance agricultural productivity and resource sustainability.