Bismuth ferrite (BFO) is a unique member of the multiferroic family exhibiting piezoelectric, ferroelectric, and antiferromagnetic behavior simultaneously at room temperature. BFO is a p-type semiconductor with ABO3 perovskite structure and an optical band gap ranging from 1.9-2.7 eV, depending on the stoichiometry and the defects created during synthesis. It is widely reported as a promising material for multiferroic applications such as magnetoelectricity, spintronics, ferroelectric random-access memory, to name a few. Recent studies have also discussed the use of BFO as a sensor for sulphur dioxide, ammonia, and acetone detection, thus showing the material's promise towards gas sensing applications. BFO possesses good chemical and thermal stability, optical bandgap in the visible light range, and its unique room temperature multiferroic nature enabling efficient charge separation, all the traits desired in a practical gas sensing material.

Nitrogen dioxide (NO2) is a major pollutant causing acid rain, photochemical smog, and respiratory damage. The annual safe limit is 50 parts per billion (ppb), while concentrations exceeding 1 parts per million (ppm) can result in respiratory ailments. Conventionally, n-type metal oxide semiconductors (MOS) operating at elevated temperatures have been utilized for NO2 detection. Recently, p-type semiconductors with their hole accumulation layer, rapid recovery post gas exposure, and good humidity tolerance are being investigated as potential NO2 sensors, once again working at elevated temperatures. In my thesis, a room temperature NO2 sensor is demonstrated by using a nanocomposite based on p-type bismuth ferrite (BFO) nanoparticles and silver nanowires (Ag NWs). The development of a nanocomposite, combining an active sensing element (BFO) and a charge transport element (Ag NWs) opens a multitude of other application areas. BFO-Ag NW printed composites fabricated by direct writing were also studied for transparent flexible photodetectors applications, which can be combined with gas sensing to achieve frugal, flexible, and low/self-powered integrated sensing platforms.