DC electrical conductivity and rate of ammonia vapour-sensing performance of synthetic polypyrrole–zirconium(IV) phosphate cation exchange nanocomposite

Effective and reliable platform for nonenzymatic nanomolar-range quinol detection in water samples using ceria doped polypyrrole nanocomposite embedded on graphitic carbon nitride nanosheets

A glassy carbon electrode modification by a novel ternary nanocomposite of advantageously united ceria, polypyrrole, and graphitic carbon nitride (CeO₂/Ppy@g-C₃N₄) is reported here. It can be used to tailor the sensor surface for the electrochemical detection of nanomolar-level quinol (Qnl), a chemical widely used as a developing agent in photography and lithography, as a cosmetic, and as an antioxidant in rubber and food industries. The occupational exposure of Qnl may occur by inhalation or dermal contact, leading to lot of health hazards. The synthesized nanocomposite was characterized by various analytical techniques such as UV-Vis, Fourier transformed infrared (FTIR), X-ray powder diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, Raman, thermogravimetric analysis, energy-dispersive X-ray spectroscopy, selected area electron diffraction, and elemental mapping analyses. The oxidation current of Qnl is linear to its concentration in the range of 0.01-260 μM and the lowest detection and quantification limit are found to be 1.5 nM and 0.004 μM, respectively, with a sensitivity of 283.33 μA mM^-1 cm^-2. The performance of the modified electrode was compared with those of high-performance liquid chromatography, which indicates that the proposed sensor can be used as an effective and reliable platform for nano-molar detection of Qnl in various environmental and biological fluids.

A Switching-Type Positive Temperature Coefficient Behavior Exhibited by PPy/(PhSe)2 Nanocomposite Prepared by Chemical Oxidative Polymerization

In this study, we prepared a polypyrrole-diphenyl diselenide [PPy/(PhSe)₂] nanocomposite by oxidative chemical polymerization for the purpose of temperature sensing applications. Fourier transform infrared spectroscopy, X-ray diffraction and scanning transmission electron microscopy confirmed the synthesis of the above material. Thermogravimetry (TG) revealed enhanced thermal stability as compared to pristine polypyrrole (PPy). Dielectric study showed the material to have a dielectric constant of colossal value. The material has been found to exhibit correlated barrier hopping conduction (CBH) wherein hopping of charge carriers takes place over the insulating (PhSe)₂ barrier. The maximum barrier height was found to be 0.224 eV. The nanocomposite material was found to exhibit a switching-type positive temperature coefficient (PTC) behavior with a Curie temperature of 400 K. This has been explained by a CBH model wherein PPy chains expand upon heating, thereby reducing the barrier height to facilitate current flow. However, above 400 K, disruption of PPy chains allows to reflect a PTC behavior. This has been in agreement with TG data.