A sustainable approach towards utilization of plastic waste for an efficient electrode in microbial fuel cell applications.

Microbial fuel cells (MFC) are a novel technique for power generation from wastewater. A number of approaches for the modification of physical as well as chemical properties of the electrodes can be employed to attain the maximum output power density and high power electricity. The use of an active organic linker, extracted from waste residue (plastic), for the synthesis of porous nanostructured materials would be beneficial in the fabrication of electrodes for MFC. Herein, terephthalic acid monomer (t) derived from plastic waste was successfully applied as an electrochemically active linking unit to form an iron-based metal-organic framework (Fe-t-MOF: MIL-53(Fe)). The synthesized Fe-t-MOF was further modified with conducting polymer (polyaniline (PANI)). The produced nanocomposite (Fe-t-MOF/PANI) was coated on stainless steel (SS) disk (as a current collector) for use as an electrode component of the MFC system. The power density, open circuit potential (OCP), and a limiting current density of the MFC are 680 mW/m2, 0.67 V, and 3500mA/m2, respectively. The technique opted here should help search a novel, efficient, sustainable, and cost-effective route for the modification of the plastic waste into an MFC electrode to achieve bioenergy production through wastewater treatment.

PANI/PbS QD nanocomposite structure for visible light driven photocatalytic degradation of rhodamine 6G.

Among conducting polymers, polyaniline (PANI) is one of the most widely used materials due to its unique properties (e.g., high electrical conductivity, outstanding electrochemical properties, easy polymerization, high stability, and low-cost synthesis). In this study, we report the synthesis of a composite of polyaniline with lead sulfide quantum dots (PbS QDs), which was subsequently employed for photocatalysis of a dye, rhodamine 6G (Rh-6G). This PANI/PbS composite was prepared by employing the chemical oxidative polymerization of aniline monomer in the presence of PbS QDs. The composite has been characterized by X-ray powder diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and ultraviolet-visible spectroscopy. The composite formation turned out to be beneficial not only for the dispersion of PbS QDs but also for increasing the conductivity of the whole catalyst. They exhibited ~87% degradation of the dye content for 50 min. The kinetic rate for its destruction is 5.03 mmol g-1 h-1 with the quantum efficiency (QE) of 7.98E-06 molec/photon. Due to enhanced charge transfer characteristics, the PANI/PbS photocatalyst was capable of efficiently degrading the dye molecules across varying concentrations. The electron-hole pair generated after the visible light irradiation on the PANI/PbS composite led to an efficient oxidative degradation of Rh 6G.

Synthesis and spectroscopic studies of functionalized graphene quantum dots with diverse fluorescence characteristics.

In this research, we report a facile method for synthesizing a series of carboxyl functionalized graphene quantum dots (GQDs) using graphite flakes (300 meshes) as raw material. These highly luminescent GQDs emitted blue, light blue, green, yellow, and red light (400-700 nm intensity peaks) under ultraviolet irradiation conditions, while exhibiting quantum yields in the range of 50-70%. The products were comprehensively characterized using ultraviolet-visible, photoluminescence, infrared, Raman, and dynamic light scattering spectroscopies. The GQDs were found to remain highly stable against photobleaching when stored over a prolonged period of more than three months. The proposed method for the synthesis of high quality, multicolor GQDs can be utilized to extend the application of these nanoparticles to molecular biotechnology and bioengineering; for example, the immobilization of cancer markers on their surface. As such, carboxylic acid groups present on the surface of these GQDs help create complexes for in vivo sensing applications.

Graphene modified screen printed immunosensor for highly sensitive detection of parathion.

Due to indiscriminate use of pesticides, there is a growing need to develop sensors that can sensitively detect the trace amount of pesticides in food and water samples. Parathion, identified as an acetylcholinesterase inhibitor, had been one of the most widely used pesticides throughout the world. Symptoms of its poisoning are found to be diverse enough to include nausea, vomiting, diarrhea, muscle cramping/twitching, and shortness of breath. In this work, a graphene based impedimetric immunosensor has been fabricated and employed for highly sensitive and specific detection of parathion. The fabrication proceeded through the modification of the screen-printed carbon electrodes (SPE) with graphene sheets, followed by their functionalization with 2-aminobenzyl amine (2-ABA) via an electrochemical reaction. These amine functionalized graphene electrodes were then bio-interfaced with the anti-parathion antibodies. In the impedimetric mode, this biosensor detected parathion in a broad linear range, i.e. 0.1-1000ng/L with a very low limit of detection (52pg/L). It also showed high selectivity towards parathion in the presence of malathion, paraoxon, and fenitrothion. The viability of this biosensor was demonstrated by detecting parathion in real samples (e.g., tomato and carrot) and through cross-calibration against HPLC.