Síntese e caracterização de um sensor a base de polianilina (PANI) fototermicamente estimulado para detecção de amônia

Abstract

The field of gas and volatile compound sensing has gained prominence in the food, beverage, and fuel industries due to sensors' ability to detect and quantify substances imperceptible to humans. However, many sensors rely on metal oxides, which require high temperatures for analysis, making the search for new materials necessary. Among conductive materials, Polyaniline (PANI) stands out due to its electrical conductivity, optical properties, and broad applicability. This study proposes modifications to PANI using nanotechnology and photothermal effects to enhance its performance. The main objective was to obtain nanostructured conductive polymers and study their electrical behavior under photothermal stimulation in the presence of gases and volatile compounds. The PANI synthesis employed the surfactant Triton X-100. For photothermal characterization, a setup was assembled with an infrared LED (780 nm, 3W) to excite the samples dispersed in water, enabling the calculation of photothermal conversion efficiency. The synthesized samples were analyzed by X-ray diffraction (XRD) at UFMA’s central analytical facility. Particle morphology was examined using scanning electron microscopy (SEM), while FT-IR, UV-Vis, and XRD spectra were obtained to correlate structural and optical properties. Sensor fabrication employed spin-coating deposition onto a substrate, developed at the Colloids Laboratory (UFMA), to form thin films. Sensor tests were conducted using ammonium hydroxide (NH4OH), injected via microsyringe (0-100 µL) at varying concentrations, with injection cycles to estimate response times and signal recovery, using a vacuum system. Electrical resistance was monitored using a controlled voltage source and a 4 ½-digit multimeter. During testing, the sensor was stimulated by an infrared LED (3V) to evaluate its photothermal performance. The results demonstrated that photothermal conversion improved selectivity and response speed due to irradiation-induced heating. The study highlighted the potential of photothermally induced nanostructured polymers as sensors for volatile compounds and gases, establishing a new research direction.