Chinwe O. Ikpo

A Fumonisins Immunosensor Based on Polyanilino-Carbon Nanotubes Doped with Palladium Telluride Quantum Dots

An impedimetric immunosensor for fumonisins was developed based on poly(2,5-dimethoxyaniline)-multi-wall carbon nanotubes doped with palladium telluride quantum dots onto a glassy carbon surface. The composite was assembled by a layer-by-layer method to form a multilayer film of quantum dots (QDs) and poly(2,5-dimethoxyaniline)-multi-wall carbon nanotubes (PDMA-MWCNT). Preparation of the electrochemical immunosensor for fumonisins involved drop-coating of fumonisins antibody onto the composite modified glassy carbon electrode. The electrochemical impedance spectroscopy response of the FB1 immunosensor (GCE/PT-PDMA-MWCNT/anti-Fms-BSA) gave a linear range of 7 to 49 ng L−1 and the corresponding sensitivity and detection limits were 0.0162 kΩ L ng−1 and 0.46 pg L−1, respectively, hence the limit of detection of the GCE/PT-PDMA-MWCNT immunosensor for fumonisins in corn certified material was calculated to be 0.014 and 0.011 ppm for FB1, and FB2 and FB3, respectively. These results are lower than those obtained by ELISA, a provisional maximum tolerable daily intake (PMTDI) for fumonisins (the sum of FB1, FB2, and FB3) established by the Joint FAO/WHO expert committee on food additives and contaminants of 2 μg kg−1 and the maximum level recommended by the U.S. Food and Drug Administration (FDA) for protection of human consumption (2–4 mg L−1).

Functionalized Benzimidazole Scaffolds: Privileged Heterocycle for Drug Design in Therapeutic Medicine

Benzimidazole derivatives are crucial structural scaffolds found in diverse libraries of biologically active compounds which are therapeutically useful agents in drug discovery and medicinal research. They are structural isosteres of naturally occurring nucleotides, which allows them to interact with the biopolymers of living systems. Hence, there is a need to couple the latest information with the earlier documentations to understand the current status of the benzimidazole nucleus in medicinal chemistry research. This present work unveils the benzimidazole core as a multifunctional nucleus that serves as a resourceful tool of information for synthetic modifications of old existing candidates in order to tackle drug resistance bottlenecks in therapeutic medicine. This manuscript deals with the recent advances in the synthesis of benzimidazole derivatives, the widespread biological activities as well as pharmacokinetic reports. These present them as a toolbox for fighting infectious diseases and also make them excellent candidates for future drug design.

Optoelectronics of Stochiometrically Controlled Palladium Telluride Quantum Dots

Water dispersed PdTe semiconducting nanocrystals were synthesized and stabilised with 3-mercaptopropionic acid (3-MPA). HRTEM studies revealed the formation of spherical nanoparticles of average size ~4 nm with good crystallinity. UV-visible spectral analysis and band gap measurements confirmed that the nanocrystals are indeed semiconductors. This semiconducting characteristic was supported by electrochemical impedance spectroscopy (EIS) data which gave Bode plots with absolute frequency and a maximum frequency phase angle values of 38.3° and 75°, respectively. Electroanalysis of the film on glassy carbon electrode (GCE) verified the retention of the ability of Pd to adsorb hydrogen on its surface as well as absorb hydrogen within its lattice.

Electrochemical Studies on Novel LiMnPO4 Coated with Magnesium Oxide-Gold Composite Thin Film in Aqueous Electrolytes

Abstract. Pristine LiMnPO4 and LiMnPO4/Mg-Au composite cathode materials were synthesized and their electrochemical properties interrogated using voltammetric, spectroscopic and microscopic techniques. The composite cathode exhibited better reversibility and kinetics than the pristine LiMnPO4. This was demonstrated in the values of the diffusion coefficient (D) and the charge and discharge capacities determined through cyclic voltammetry. For the composite cathode, D = 2.0 x 10-9 cm2/s while the pristine has a D value of 4.81 x 10-10 cm2/s. The charge and discharge capacities of LiMnPO4/Mg-Au at 10 mV/s were 259.9 mAh/g and 157.6 mAh/g, respectively. The corresponding values for pristine LiMnPO4 were 115 mAh/g and 44.75 mAh/g, respectively.. A similar trend was observed in the results obtained from electrochemical impedance spectroscopy measurements. These results indicate that LiMnPO4/Mg-Au composite has better conductivity and will facilitate faster electron transfer and better electrochemical performance than pristine LiMnPO4.

Palladium-Gold nanoalloy surface modified LiMn 2 O 4 cathode for enhanced Li-Ion battery

Au with Pd nanoparticles were synthesized and coated onto the spinel LiMn2O4 via a coprecipitation calcination method with the objective to improve the microstructure, conductivity, and electrochemical activities of pristine LiMn2O4. The novel Li[PdAu]xMn2-xO4 composite cathode had high phase purity, well crystallized particles, and more regular morphological structures with narrow size distributions. At enlarged cycling potential ranges the Li[PdAu]xMn2-xO4 sample delivered 90 mAh g-1 discharge capacity compared to LiMn2O4 (45 mAh g-1). It was concluded that even a small amount of the Pd and Au enhanced both the lithium diffusivity and electrochemical conductivity of the host sample due to the beneficial properties of their synergy.

Iron-Gold Coated-LiMn2-XO4 Nanowire High Power Cathode System Probed by Spectroscopic and Microstructural Analysis

The migration of lithium (Li) ions in electrode materials affects the rate performance of rechargeable Li ion batteries. Therefore, the application of LiMn2O4, whichis an appealing cathode material in high power systems, requires fast electron transfer kinetics which is possible through the use of nanostructured morphologies and conductive material. Nanowires offer the advantage of a large surface to volume ratio, efficient electron conducting pathways and facile strain relaxation. In this study, LiMn2O4 nanowires with cubic spinel structure were synthesized by using a α-MnO2 nanowire-template-based method. LiMn2O4 nanowires have diameters less than 10 nm and lengths of several micrometers. Fe-Au nanoparticles were synthesized and used as coating material to improve both the catalytic activities and stability of the LiMn2O4 nanowires. The Li[Fe0.02Au0.01]Mn1.97O4 nanowires with modified architecture effectively accommodates the structural transformation during Li+ ion charge and discharge. Hence, the Li[Fe0.02Au0.01]Mn1.97O4 nanowire cathode system shows outstanding stability and enhanced electrocatalytical properties. Microstructural analysis of Li[Fe0.02Au0.01]Mn1.97O4 linked its composition and processing to its properties and performance. High resolution transmission electron microscope (HR-TEM) of the nanomaterial showed good crystallinity which contributed towards good reversibility. XRD analysis revealed a pure cubic spinel structure without any impurities. Structural information provided by Raman and solid state spectroscopy further corroborated these findings. The improved rate and cycling performance is related to the conductive particles infused within the nanowires which make up the electrode.

Bimetallic Nanocomposites of Palladium (100) and Ruthenium for Electrooxidation of Ammonia

Symmmetrically oriented Pd (100) and its bimetallic Pd (100)Ru electrocatalysts were chemically synthesized and their conductive properties employed in the electrochemical oxidation of ammonia. Electrochemical data based on EIS, SWV and CV revealed that the Pt/Pd (100)Ru electrode showed a better conductivity and higher catalytic response towards the electrooxidation of ammonia compared to Pt/Pd (100) electrode. This was demonstrated by the EIS results where Pt/Pd (100)Ru gave a charge transfer resistance (Rct) of 48.64 Ω, high exchange current and lower time constant (5.2738 x 10-1A and 3.2802 x 10-7 s /rad) values while the Pt/Pd (100) had values of 173.2 Ω, 1.4811 x 10-1A and 4.8321 10-7 s /rad. The drastic drop in Rct highlights the superiority of the Pt/Pd (100)Ru over the Pt/Pd (100) and confirms that facile interfacial electron transfer processes occur on the Pt/Pd (100)Ru electrode during the electrocatalytic ammonia oxidation. Investigations through voltammetry revealed that the Pt/Pd (100)Ru had a higher peak current density and a shift in potential to more negative values at ≈ -0.2 V and ≈ -0.4 V. The EASA value of Pt/Pd (100)Ru was found to be 119.24 cm2 whereas Pt/Pd (100) had value of 75.07 cm2. The high electrochemically active surface area of Pd (100)Ru at 119.24 cm2 compared to the 75.07 cm2 for Pd (100) strengthened this observation in performance between the two catalysts for ammonia electrooxidation.

Anilino-Functionalized Graphene Oxide Intercalated with Pt Metal Nanoparticles for Application as Supercapacitor Electrode Material

Nanostructured anilino-functionalized reduced graphene oxide intercalated with Pt metal nanoparticles was successfully synthesized. Graphene oxide nanosheets were synthesized using a modified Hummers method with simultaneous in-situ functionalization with aniline and ionic Pt reduction and dispersion through sonication. The nanomaterial was characterised with FTIR, UV-visible, SEM, TEM, EDX, XRD and Raman spectroscopy to ascertain surface, chemical, elemental and crystalline properties, composite structures, size, morphology and successful entrapment of metal nanoparticles while the electro-conductivity of the nanomaterial was interrogated using CV. The graphene oxide was successfully functionalized with aniline with new peaks belonging to the N-H and C-N group being present and calculated band gaps of 5.35 eV and 4.39 eV which are attributed to functionalization of graphene oxide. The functionalized graphene oxide was successfully loaded with platinum nanoparticles as TEM revealed that the Pt particles are spread out on the graphene sheets and when magnified a uniform distribution of the nanoparticles can be observed. The material (functionalized graphene oxide loaded with platinum nanoparticles) was used in the design of an asymmetric supercapacitor cell using 6M KOH aqueous electrolyte. On testing by galvanostatic charge/discharge, a high specific capacitance value of 605 F/g with a corresponding energy and power densities of 0.021kWh/Kg and 0.372kW/Kg respectively, were obtained.

Electrokinetic and Impedimetric Dynamics of FeCo-Nanoparticles on Glassy Carbon Electrode

The electrochemical dynamics of a film of FeCo nanoparticles were studied on a glassy carbon electrode (GCE). The film was found to be electroactive in 1 M LiClO4 containing 1:1 v/v ethylene carbonate dimethyl carbonate electrolyte system. Cyclic voltammetric experiments revealed a diffusion-controlled electron transfer process on the GCE/FeCo electrode surface. Further interrogation on the electrochemical properties of the FeCo nanoelectrode in an oxygen saturated 1 M LiClO4 containing 1:1 v/v ethylene-carbonate-dimethyl carbonate revealed that the nanoelectrode showed good response towards the electro-catalytic reduction of molecular oxygen with a Tafel slope of about 120 mV which is close to the theoretical 118 mV for a single electron transfer process in the rate limiting step; and a transfer coefficient (α) of 0.49. The heterogeneous rate constant of electron transfer (ket), exchange current density (io) and time constant (τ) were calculated from data obtained from electrochemical impedance spectroscopy and found to have values of 2.3 x 10-5 cm s-1, 1.6 x 10-4 A cm-2 and 2.4 x 10-4 s rad-1, respectively.