A simple, cost‐effective, and novel chemical sensor for ammonia (NH3) gas detection was developed from polyaniline (PANI)/quail eggshell (QES) composites. QES is a natural waste enriched in calcium carbonate. In this work, pure PANI was synthesized from chemical oxidation method and PANI/QES composites were prepared from physical mixing of QES with the synthesized PANI at different mass ratio. A series of complementary techniques including Fourier transform infrared and ultraviolet‐visible spectrometers, scanning electron microscope with energy dispersive detection coupled with mapping, thermogravimetric analysis, and X‐ray diffractometer were used to characterize the physicochemical and textural properties of the biocomposites. From the results, PANI/QES composite with a mass ratio of 1 exhibited the lowest NH3 detection limit of 5.24 ppm with a linear correlation coefficient (R2) of close to unity (0.9932) between the signal and NH3 gas concentration. As a whole, the PANI/QES biocomposites synthesized from this work exhibited excellent selectivity toward NH3 gas even in the presence of other gas impurities, such as acetone, ethanol, and hexane. For the sensor reusability, the PANI/QES biocomposites can be reused in the application of NH3 gas detection for at least 4 cycles.

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The present study highlights the sunlight-assisted photodegradation of methylene blue (MB) using tungsten disulphide/polypyrrole (WS2/PPy) composite as a photocatalyst. WS2/PPy was prepared via oxidative polymerization using ferric chloride (FeCl3) as an oxidant. Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and Field Emission Scanning Electron Microscope (FESEM) measurement were used to ensure the physicochemical properties of WS2/PPy. The photocatalytic efficiencies of the photocatalysts were examined by degrading methylene blue (MB) under sunlight irradiation. The results showed that the degradation efficiency of WS2/PPy was higher than the pristine PPy Several optimizations such as effect of the concentration, contact time, photocatalyst dosage and initial concentration were investigated. The results revealed that, under optimum condition of pH 3, 100 mg photocatalyst dosage, 10 ppm MB initial concentration within 180 minutes contact time, were the most effective parameters, that produced 96.15% of sunlight-assisted photodegradation in aqueous solution of MB.