Synergistic conductivity increase in polypyrrole/molybdenum disulfide composite

Polypyrrole Aerogels: Efficient Adsorbents of Cr(VI) Ions from Aqueous Solutions

Three-dimensional and porous polypyrrole (PPy) aerogels were prepared using a facile two-step procedure in which cryogels were synthesized via the cryopolymerization of pyrrole with iron (III) chloride in the presence of supporting water-soluble polymers (poly(N-vinylpyrrolidone), poly(vinyl alcohol), gelatin, methylcellulose or hydroxypropylcellulose), followed by freeze-drying to obtain aerogels. The choice of supporting polymers was found to affect the morphology, porosity, electrical conductivity, and mechanical properties of PPy aerogels. PPy aerogels were successfully used as adsorbents to remove toxic Cr(VI) ions from aqueous solutions.

Core-shell structured Co3O4@PPy composite for electrochemical determination of terbutylhydroquinone

TBHQ is a significant synthetic antioxidant, but excessive use of TBHQ is harmful to human health. Therefore, the preparation of a high-efficiency TBHQ electrochemical sensor is of great significance. In this work, a core-shell structured Co3O4@PPy composite is synthesized for TBHQ determination and exhibits remarkable electrochemical properties. The core-shell structure of Co3O4@PPy composite shows the synergistic effects of fast charge transfer, rich active surface area and more active sites. Under optimal conditions, the linear range of the developed sensor is 0.2-600 μM, and the detection limit is 0.05 μM (S/N = 3). In addition, it also has good stability and reproducibility due to the stable protective role of the PPy shell. The proposed sensor can also be applied to practical sample detection.

In-situ fabrication of polypyrrole composite with MoO3: An effective interfacial charge transfers and electrode materials for degradation and determination of acetaminophen

Pharmaceutical wastes, acetaminophen (AP) widely used in medical fields, is often discharged into water, causing harm to human health. Hence, there is an urgent need to effectively remove AP from wastewater systems. In this paper, polypyrrole (PPy) composite with MoO₃ has been synthesized via an in-situ polymerization method. The as-prepared materials were thoroughly characterized by XRD, FT-IR, UV-DRS, SEM, TEM and mapping techniques. The as-prepared MoO₃@PPy composite was utilized to removal of AP via photocatalytic degradation and electrochemical determination. Under optimized composite, MoO₃@PPy (2) showed an excellent photocatalytic degradation and electrochemical determination of AP compared to pure MoO₃ and all other composites. The higher catalytic activity was ascribed to the effective interfacial charges transfer, reduce the recombination and enhance the active surface area of electrode via a synergistic effect. The photocatalytic degradation mechanism, rate and kinetic of the reaction were investigated and discussed. The major active degradation species and an effective charge transfer properties were confirmed by trapping experiments and photocurrent spectra. In addition, the MoO₃@PPy (2) modified GCE exhibit the AP determination activity by DPV with a linear range of 0.05-546 μM. The limit of detection and sensitivity of electrode were 0.0007 μM and 0.242 μM^-1 cm^-2 respectively. Moreover, the proposed electrode showed good selectivity, stability and reproducibility. This method was useful for the determination of AP in real samples.

A Self-Standing Binder-Free Biomimetic Cathode Based on LMO/CNT Enhanced with Graphene and PANI for Aqueous Rechargeable Batteries

The electrochemical parameters of a novel binder-free self-standing biomimetic cathode based on lithium manganese oxide (LMO) and carbon nanotubes (CNT) for rechargeable Lithium-ion aqueous batteries (ReLIAB) are improved using polyaniline (PANI) core-shell in situ polymerization and graphene (Gr). The fabricated cathode material exhibits the so-called “tectonic plate island bridge” biomimetic structure. This constitution is created by combining three components as shown by a SEM and a TEM analysis: the Gr substrates support an entangled matrix of conductive CNT which connect island of non-conductive inorganic material composed of LMO. The typical spinel structure of the LMO remains unchanged after modifying the basic structure with Gr and PANI due to a simplified hydrothermal method used for synthesis. The Gr and PANI core-shell coating improves the electric conductivity from 0.0025 S/cm up to 1 S/cm. The electrochemical performances of the LMO/CNT-Gr/PANI composite electrode are optimized up to 136 mA h g⁻¹ compared to 111 mA h g⁻¹ of the LMO/CNT. Besides that, the new electrode shows good cycling stability after 200 galvanostatic charging/discharging cycles, making this structure a future candidate for cathode materials for ReLIAB.

MoS2/PPy Nanocomposite as a Transducer for Electrochemical Aptasensor of Ampicillin in River Water

We report the design of an electrochemical aptasensor for ampicillin detection, which is an antibiotic widely used in agriculture and considered to be a water contaminant. We studied the transducing potential of nanostructure composed of MoS2 nanosheets and conductive polypyrrole nanoparticles (PPyNPs) cast on a screen-printed electrode. Fine chemistry is developed to build the biosensors entirely based on robust covalent immobilizations of naphthoquinone as a redox marker and the aptamer. The structural and morphological properties of the nanocomposite were studied by SEM, AFM, and FT-IR. High-resolution XPS measurements demonstrated the formation of a binding between the two nanomaterials and energy transfer affording the formation of heterostructure. Cyclic voltammetry and electrochemical impedance spectroscopy were used to analyze their electrocatalytic properties. We demonstrated that the nanocomposite formed with PPyNPs and MoS2 nanosheets has electro-catalytic properties and conductivity leading to a synergetic effect on the electrochemical redox process of the redox marker. Thus, a highly sensitive redox process was obtained that could follow the recognition process between the apatamer and the target. An amperometric variation of the naphthoquinone response was obtained regarding the ampicillin concentration with a limit of detection (LOD) of 10 pg/L (0.28 pM). A high selectivity towards other contaminants was demonstrated with this biosensor and the analysis of real river water samples without any treatment showed good recovery results thanks to the antifouling properties. This biosensor can be considered a promising device for the detection of antibiotics in the environment as a point-of-use system.

Frozen-State Polymerization as a Tool in Conductivity Enhancement of Polypyrrole

Polypyrrole (PPy) is oxidatively polymerized in the frozen state at -24 °C in the presence of various organic dyes as morphology guiding agents in order to form homogeneous 1D PPy nanoforms. The freezing polymerization of pyrrole has a significant influence on the electrical conductivity and thermal stability but negligible influence on the yield compared to widely used room temperature polymerization.

Resonance Raman Spectroscopy of Conducting Polypyrrole Nanotubes: Disordered Surface versus Ordered Body

Polypyrrole nanotubes rank among the most conducting forms of organic semiconductors. They are prepared by the oxidation of pyrrole in the presence of methyl orange. Other organic dyes, viz. ethyl orange, Acid Blue 25, and Acid Blue 129, have been used in the present study to prepare globules or nanofibers. The resulting polypyrroles were studied in detail by Raman spectroscopy. The apparent paradox when a dye contribution to spectra is absent with 785 nm excitation line and present with shorter wavelengths is explained by the resonance character of the Raman scattering, which allows the separation of the contributions from the polypyrrole surface and from the bulk. These differ depending on the laser excitation wavelength and the position of absorption maximum of the individual dyes in ultraviolet-visible spectra and affect both the laser-penetration depth and observation of the resonance effect. The spectra are discussed in terms of different ordering of polymer chains in individual morphologies. The correlation between conductivity, surface areas, and the proportions of ordered and disordered polypyrrole phases at the surface and in the interior of nanostructures is proposed and established using resonance Raman spectroscopy.