Design and development of symmetric aromatic bischalcogenide-based photocatalysts for water treatment application: a concise study of diphenyl diselenide polypyrrole nanocatalysis.

Dopant engineering can be a very selective approach in designing hybrid materials. Incorporating the required functionality in a dopant effectively modulates its properties towards aimed applications. Consequently, this work through a comparative study envisaged the incorporation of chalcogenides (S, Se, and Te) in a biphenyl motif based on the analysis of major photocatalytic descriptors. Bischalcogenides as tuned dopants have been impressive in enhancing the surface area, increasing crystallinity and facilitating band gap shifts towards better light harvesting. In addition, the chalcogen effect was observed to induce preferential ion migration, leading to effective charge separation and attenuated recombination rates. Photocatalytic descriptors evaluated from electrochemical impedance spectroscopy and photoluminescence data corroborated the chalcogen effect in the observed trend (Ph)2 < (PhS)2 < (PhSe)2 < (PhTe)2. The diphenyl diselenide polypyrrole nanocomposite emerged to be better among the studied systems. (PhSe)2/PPY was characterized and comprehensively evaluated for its photocatalytic activity towards varied dye classes and the colorless isoniazid antibiotic under environmentally viable conditions. Its calculated band potential values and scavenger experiments indicate OH˙ and O2 ˙- as dominant species in its photocatalytic activity. Control experiments confirmed photocatalytic degradation over photolysis as the dye decolouration mechanism. Taken together, (PhSe)2/PPY emerges as a good propensity photocatalyst worthy of real time customization for wastewater treatment on a pilot scale.

Adsorptive avidity of Prussian blue polypyrrole nanocomposite for elimination of water contaminants: a case study of malachite green and isoniazid.

Persistent water contaminants include a variety of substances that evade natural cleaning processes posing severe risks to ecosystems. Their adsorptive elimination is a key approach to safer attenuation. Herein we present the design and development of Prussian blue incorporated polypyrrole (PPY/PB) hybrid nanocomposite as a high-performance adsorbent for the elimination of malachite green (M.G.), isoniazid (INH) and 4-nitrophenol (4-NP) water contaminants. The nanocomposite synthesis was favored by strong dopant-polymer interactions, leading to a PPY/PB material with enhanced electro-active surface area compared to pristine PPY. The structure-activity response of the nanocomposite for the adsorption of target contaminants was unveiled by evaluating its maximum adsorption capacities under environmentally viable conditions. In-depth analysis and optimization of adsorption influencing factors (pH, temperature, and adsorbent dose) were performed. Using equilibrium studies, kinetic model fitting, aided with FTIR analysis, a multi-step mechanism for the adsorption of target contaminants on the nanocomposite was proposed. Furthermore, the PPY/PB nanocomposite also acts as a catalyst, enabling contaminant elimination following a synergistic scheme that was demonstrated using 4-NP contaminant. The synergetic adsorption and catalytic degradation of 4-NP using PPY/PB as adsorbent and catalyst was demonstrated in the presence of NaBH4 as a reducing agent in absence of light. In summary, this work highlights the targeted design of adsorbent, its optimization for adsorptive avidity, and the synergistic role of adsorption trapping in the catalytic degradation of persistent contaminants.

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.