Surfactant-Assisted Nickel Ferrite (NiFe₂O₄) Nanostructured Sensor With Dual Functionality for Gas and Acceleration Sensing in Underground Mining and Sewage Systems

Dual-functional sensors for gas and acceleration detection are vital for ensuring safety in mining and sewage systems, enabling hazardous gas detection (CO and CH<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub>) and structural monitoring. This study compares two Nickel Ferrite (NiFe<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub>O<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub>) sensor configurations: (NF-without surfactant), and NF-S (with oleic acid as a surfactant) to evaluate their enhanced sensing performance. Oleic acid was used to control particle morphology, reduce agglomeration, and increase surface area, thereby improving gas adsorption and charge transport. Gas detection was assessed at low concentrations (2-10 ppm) under room temperature conditions, where NF exhibited sensitivities of 30.33% (CO) and 28.62 % (CH<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub>), whereas NF-S demonstrated enhanced sensitivities of 32.25 % and 30.17%, confirming the surfactant’s beneficial effect. Additionally, acceleration sensing was conducted across a frequency range of 1-20 Hz with input accelerations from 0.1 to 1g. At 18 Hz, the maximum output voltages recorded were 0.86 V (NF) and 0.61 V (NF-S), with corresponding sensitivities of 0.93 V/g and 1.55 V/g, respectively, demonstrating an improved mechanical response in the surfactant- assisted sensor. These findings highlight the significant enhancement in dual- sensing performance achieved with NF-S, making it a promising candidate for safety-critical applications.