PANI/f-rGO/CuxZn1-xFe2O4 composite on flexible PVDF mat for trace-level detection of ammonia and thermoelectric characterization at room temperature

Abstract

This article demonstrates a thin film-based portable, reliable, highly sensitive and flexible ammonia sensor prepared by depositing a ternary nanocomposite thin film on an electrospun polyvinylidene difluoride (PVDF) mat. Owing to achieve optimum porosity and uniformity in the mat, electrospun time is varied from 0.5 h to 3 h. The nanocomposite is made out of polyaniline (PANI), functionalised reduced graphene oxide (f-rGO) and copper-zinc ferrite (CuxZn1-xFe2O4), and it has been named as PRC composite. Six variants of the nanocomposite have been prepared. Among those, the first two are developed with rGO (PRC1) and f-rGO (PRC2) remaining PANI and CuxZn1-xFe2O4 (x = 0) constant, the other four (PRC3-PRC6) are produced through stoichiometric variation (0.25≤x≤1) between copper (Cu) and zinc (Zn) in CuxZn1-xFe2O4 while PANI and f-rGO remain persistent. All the samples are rigorously characterised with FESEM, HRTEM, XRD, FTIR, RAMAN and UV-VIS. The microstructural analysis performed with FESEM explicitly shows that 1 h grown PVDF mat owns optimum porosity. The analysis also reveals the flaky nature of rGO, particulate form of ferrite, and granulated yet rod-shaped structure of PANI. Another microscopical inspection, carried out with HRTEM, measures the diameters of PANI, rGO and ferrite particles as 15–60 nm, 20–30 nm and 12.48 nm respectively. Out of six samples, the PRC4 unambiguously exhibits outstanding responsivity (47% @ 200 ppb and 1833% @ 80 ppm), superb reliability (deviation only 4.4% @ 200 ppb and 1.9% @ 80 ppm), faster response/recovery (tres/trec = 6.5 s/139.3 s and 2.1 s/50.7 s @ 200 ppb and 80 ppm respectively), incomparably high amount of selectivity towards NH3 at room temperature (25 °C) and magnificently obeys power law equation against ppm variation (Power factor, P∼0.54). The thermoelectric property of the composite materials was also explored. Finally, a plausible explanation has been given to understand the sensing phenomena.