Adsorption of hexavalent chromium using Water Hyacinth Leaf Protein Concentrate/Graphene Oxide hydrogel.

Water Hyacinth Leaf Protein Concentrate/Graphene Oxide (WHLPC/GO) hydrogel was synthesized for the removal of Cr(VI) from wastewater. About 90% of the prepared hydrogel constitutes WHLPC. The prepared material was characterized by FT-IR and XRD. The process variables such as pH, contact time, adsorbent dosage, initial Cr(VI) concentration, and temperature were optimized using a batch mode experiment. Kinetic studies were also conducted and it was observed that the chemosorptive pseudo-second-order best described the adsorption system with a correlation coefficient (R2) of 0.984. The highest adsorption capacity of 322.00 mg/g was achieved at pH 1.0, and equilibrium was achieved within 420 min. Various isotherm models were analyzed using non-linear fitting. It was found that the Sips model provides the best fit, indicating heterogeneous and uniform active site surface adsorption of Cr(VI) on the WHLPC/GO. The reuse efficiency of the synthesized material was also found to be greater than 84% for five consecutive cycles. Thermodynamic studies were conducted and results revealed that the adsorption was spontaneous and endothermic.

A Liquid Metal Microdroplets Initialized Hemicellulose Composite for 3D Printing Anode Host in Zn-Ion Battery.

Maintaining a steady affinity between gallium-based liquid metals (LM) and polymer binders, particularly under continuous mechanical deformation, such as extrusion-based 3D printing or plating/stripping of Zinc ion (Zn2+ ), is very challenging. Here, an LM-initialized polyacrylamide-hemicellulose/EGaIn microdroplets hydrogel is used as a multifunctional ink to 3D-print self-standing scaffolds and anode hosts for Zn-ion batteries. The LM microdroplets initiate acrylamide polymerization without additional initiators and cross-linkers, forming a double-covalent hydrogen-bonded network. The hydrogel acts as a framework for stress dissipation, enabling recovery from structural damage due to the cyclic plating/stripping of Zn2+ . The LM-microdroplet-initialized polymerization with hemicelluloses can facilitate the production of 3D printable inks for energy storage devices.

Cheap and sensitive polymer/bismuth film modified electrode for simultaneous determination of Pb(II) and Cd(II) ions.

Different aminonaphetalenesulphonic acid derivatives like 5-aminonaphthalene-1-sulphonic acid (5AN1SA), 2-aminonaphthalene-1-sulphonic acid (2AN1SA), 8-aminonaphthalene-2-sulphonic acid (8AN2SA) and 4-amino-3-hydroxynaphthalene-1-sulphonic acid (4A3HN1SA) were used to construct polymer/bismuth film modified electrode for simultaneous determination of Pb(II) and Cd(II) ions with the aim of developing a cheaper and sensitive electrode that could possibly replace Nafion. Among the different modified electrodes, poly (8AN2SA)/bismuth film modified electrodes showed the highest electrochemical response for both ions. These electrochemical results were also supported by density functional theory (DFT) calculations. Based on these experimental and theoretical results, poly (8AN2SA)/bismuth film glassy carbon modified electrode was further investigated to develop a simple and sensitive electrochemical method for the simultaneous determination of Pb(II) and Cd(II) ions. After optimizing the different experimental parameters, the proposed method gave a linear range of 1-40 µg/L with the detection limit of 0.38 and 0.08 µg/L for the simultaneous determination of Pb(II) and Cd(II) ions, respectively.

Electrochemical application of cobalt nanoparticles-polypyrrole composite modified electrode for the determination of phoxim.

In this study, cobalt nanoparticles (CoNPs) were synthesized and cobalt nanoparticles modified glassy carbon electrode (CoNPs/GCE) was prepared by drop coating the nanoparticles on glassy carbon electrode. After preparing polypyrrole modified glassy carbon electrode (PPy/GCE) using electropolymerization of pyrrole in LiClO4 solution, cobalt nanoparticles-polypyrrole composite modified glassy carbon electrode (CoNPs/PPy/GCE) was fabricated by drop coating the CoNPs on the PPy/GCE. Different characterization techniques such as scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, FTIR spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry were used to study the morphological structure and electrochemical behavior of the sensors. The results demonstrated that PPy chains interacted with CoNPs through donor-acceptor bonds. Among all the electrodes, CoNPs/PPy/GCE exhibited highest electroactive surface area and lowest electron transfer resistance towards phoxim. Under the optimal conditions, the sensor showed linear relationship between the reduction peak current and the concentration of phoxim in the range of 0.025 µM-12 µM with the detection limit as 4.5 nM. Besides, the composite electrode demonstrated excellent reproducibility, good stability and selectivity towards the possible interfering substances. All of these properties made CoNPs/PPy/GCE a suitable electrochemical sensor for the electrochemical determination of phoxim in water samples using square wave voltammetry.

Voltammetric determination of uric acid using multiwall carbon nanotubes coated-poly(4-amino-3-hydroxy naphthalene sulfonic acid) modified glassy carbon electrode.

In this study, an electrochemical sensor based multiwalled carbon nanotubes (MWCNTs)-poly (4-amino-3-hydroxy naphthalene sulfonic acid) modified glassy carbon electrode (MWCNTs/poly (AHNSA)/GCE) was developed for the determination of uric acid (UA). The composite electrode was prepared first by electropolymerization of the monomer (AHNSA) on GCE using cyclic voltammetry within the potential range of -0.8 V to +2.0 V vs Ag/AgCl for 15 cycles followed by drop coating of MWCNTs solution on the surface of poly (AHNSA)/GCE. Under optimal conditions, MWCNTs/poly (AHNSA)/GCE showed a linear current response with UA concentrations in the range of 1 × 10-6 to 1 × 10-4 M with R2 = 0.9972. The sensor exhibited low detection limit with a value of 0.024 µM. The sensors have been applied to successfully quantify UA in urine samples.

Roll-to-roll printed high voltage supercapattery in lead-contaminated aqueous electrolyte.

This work investigated the potential application of roll-to-roll printed PEDOT:PSS on an ITO/PET substrate using Pb2+ containing 0.1 M NaCl aqueous solution for a supercapattery. The PEDOT:PSS/ITO/PET electrode achieved 2.2 µAh cm-2 (46.5 mAh g-1) in 0.1 M NaCl and 10 µAh cm-2 (216.8 mAh g-1) in 2 mM Pb2+/0.1 M NaCl at a current density of 0.2 mA cm-2 (4.34 A g-1). The electrode also shows good cyclic performance that retains 63% of its initial capacitance after 1000 charge-discharge cycles. A device operating at a high voltage of 1.8 V was built using PEDOT:PSS/ITO/PET in aqueous electrolyte. The energy density of the symmetric PEDOT:PSS/ITO/PET device is 6.2 Wh kg-1 in 0.1 M NaCl and is improved to 11 Wh kg-1 in 3 mM Pb2+/0.1 M NaCl.

Electrocatalytic reduction of oxygen at platinum nanoparticles dispersed on electrochemically reduced graphene oxide/PEDOT:PSS composites.

Composites of commercially available graphene oxide (GO) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with solvent additive ethylene glycol (EG) were investigated as an alternative support for Pt nanoparticles towards the electrocatalytic reduction of oxygen. The surface characteristics of the materials were examined using atomic force microscopy (AFM), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDS). Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) at rotating disk electrodes (RDEs) and rotating ring-disk electrodes (RRDEs) were used to characterise the electrocatalytic activities of the composites materials. The structural and electrochemical studies reveal that the addition of EG favours the homogeneous distribution of Pt particles with reduced particle size and improves the electrocatalytic properties. A 30% and 16% increase in electrochemically active surface area (ECSA), a 1.2 and 1.1 fold increase in specific area activity (SA), and a 1.5 and 1.2 fold increase in mass activity (MA) were observed for 30% and 40% Pt loading on PEDOT:PSS after the addition of EG. A composite of rGO and PEDOT:PSS(EG) was investigated for different (w/w) ratios of PEDOT:PSS and rGO. The 1 : 2 w/w ratio showed an enhanced catalytic activity with high limiting current, more positive onset potential, higher SA and MA with lower H2O2 yield compared to PEDOT:PSS(EG) and rGO and previously reported values for PEDOT:PSS.

Quantification of lead in cooking utensils and vegetables using square wave anodic stripping voltammetry.

A simple and sensitive voltammetric method using in-situ bismuth film modified glassy carbon electrode (BiFGE) and Nafion-coated bismuth film modified glassy carbon electrode (NC-BiFGE) were used to determine the amount of lead(II) present in locally produced (at Kombolcha, 376 km North of Addis Ababa, Ethiopia) and imported cooking utensils and vegetable samples before and after cooking with the utensils. The voltammetric method was validated using standard spectroscopic method and recovery tests. The amount of lead(II) found in the locally produced utensil (6.48 mg L-1) was very high compared to the imported utensil (0.007 mg L-1). Moreover, a 3-5 fold increase in the amount of lead(II) was found when different vegetables were cooked with the local utensil as a result of the leaching out of the lead(II) from the cooking utensil.

Bioinspired Redox-Active Catechol-Bearing Polymers as Ultrarobust Organic Cathodes for Lithium Storage.

Redox-active catechols are bioinspired precursors for ortho-quinones that are characterized by higher discharge potentials than para-quinones, the latter being extensively used as organic cathode materials for lithium ion batteries (LIBs). Here, this study demonstrates that the rational molecular design of copolymers bearing catechol- and Li+ ion-conducting anionic pendants endow redox-active polymers (RAPs) with ultrarobust electrochemical energy storage features when combined to carbon nanotubes as a flexible, binder-, and metal current collector-free buckypaper electrode. The importance of the structure and functionality of the RAPs on the battery performances in LIBs is discussed. The structure-optimized RAPs can store high-capacities of 360 mA h g-1 at 5C and 320 mA h g-1 at 30C in LIBs. The high ion and electron mobilities within the buckypaper also enable to register 96 mA h g-1 (24% capacity retention) at an extreme C-rate of 600C (6 s for total discharge). Moreover, excellent cyclability is noted with a capacity retention of 98% over 3400 cycles at 30C. The high capacity, superior active-material utilization, ultralong cyclability, and excellent rate performances of RAPs-based electrode clearly rival most of the state-of-the-art Li+ ion organic cathodes, and opens up new horizons for large-scalable fabrication of electrode materials for ultrarobust Li storage.

Simultaneous determination of caffeine and paracetamol by square wave voltammetry at poly(4-amino-3-hydroxynaphthalene sulfonic acid)-modified glassy carbon electrode.

Poly(4-amino-3-hydroxynaphthalene sulfonic acid)-modified glassy carbon electrode (poly(AHNSA)/GCE) was prepared for simultaneous determination of caffeine and paracetamol using square-wave voltammetry. The method was used to study the effects of pH and scan rate on the voltammetric response of caffeine and paracetamol. Linear calibration curves in the range of 10-125µM were obtained for both caffeine and paracetamol in acetate buffer solution of pH 4.5 with a correlation coefficient of 0.9989 and 0.9986, respectively. The calculated detection limits (S/N=3) were 0.79µM for caffeine and 0.45µM for paracetamol. The effects of some interfering substances in the determination of caffeine and paracetamol were also studied and their interferences were found to be negligible which proved the selectivity of the modified electrode. The method was successfully applied for the quantitative determination of caffeine and paracetamol in Coca-Cola, Pepsi-Cola and tea samples.

Charge storage properties of biopolymer electrodes with (sub)tropical lignins.

The electrochemical and charge storage properties of different lignins inside biopolymer electrodes were studied and correlated with the chemical variations of the lignins as indicated from the nuclear magnetic resonance (NMR) spectroscopic data. The varying fractions of monolignols were found to correlate with charge storage properties. It was found that as the sinapyl to guaiacyl (S/G) ratio increased both the specific capacitance and charge capacity increased considerably. This indicates that quinones generated on S-units can contribute more to charge storage in the biopolymer electrodes.

Determination of fenitrothion in water using a voltammetric sensor based on a polymer-modified glassy carbon electrode.

A glassy carbon electrode (GCE) modified with poly(4-amino-3-hydroxynaphthalene sulfonic acid) (poly-AHNSA) was used for the selective and sensitive determination of fenitrothion (FT) organophosphorus pesticide in water. The electrochemical behavior of FT at the bare GCE and the poly-AHNSA/GCE were compared using cyclic voltammetry. Enhanced peak current response and shift to a lower potential at the polymer-modified electrode indicated the electrocatalytic activity of the polymer film towards FT. Under optimized solution and method parameters, the adsorptive stripping square wave voltammetric reductive peak current of FT was linear to FT concentration in the range of 0.001 to 6.6 x 10(-6) M, and the LOD obtained (3delta/m) was 7.95 x 10(-10) M. Recoveries in the range 96-98% of spiked FT in tap water and reproducible results with RSD of 2.6% (n = 5) were obtained, indicating the potential applicability of the method for the determination of trace levels of FT in environmental samples.

25th anniversary article: organic photovoltaic modules and biopolymer supercapacitors for supply of renewable electricity: a perspective from Africa.

The role of materials in civilization is well demonstrated over the centuries and millennia, as materials have come to serve as the classifier of stages of civilization. With the advent of materials science, this relation has become even more pronounced. The pivotal role of advanced materials in industrial economies has not yet been matched by the influence of advanced materials during the transition from agricultural to modern societies. The role of advanced materials in poverty eradication can be very large, in particular if new trajectories of social and economic development become possible. This is the topic of this essay, different in format from the traditional scientific review, as we try to encompass not only two infant technologies of solar energy conversion and storage by means of organic materials, but also the social conditions for introduction of the technologies. The development of organic-based photovoltaic energy conversion has been rapid, and promises to deliver new alternatives to well-established silicon photovoltaics. Our recent development of organic biopolymer composite electrodes opens avenues towards the use of renewable materials in the construction of wooden batteries or supercapacitors for charge storage. Combining these new elements may give different conditions for introduction of energy technology in areas now lacking electrical grids, but having sufficient solar energy inputs. These areas are found close to the equator, and include some of the poorest regions on earth.

Enhanced lithium battery with polyethylene oxide-based electrolyte containing silane-Al2 O3 ceramic filler.

A solid polymer electrolyte prepared by using a solvent-free, scalable technique is reported. The membrane is formed by low-energy ball milling followed by hot-pressing of dry powdered polyethylene oxide polymer, LiCF3 SO3 salt, and silane-treated Al2 O3 (Al2 O3 -ST) ceramic filler. The effects of the ceramic fillers on the properties of the ionically conducting solid electrolyte membrane are characterized by using electrochemical impedance spectroscopy, XRD, differential scanning calorimeter, SEM, and galvanostatic cycling in lithium cells with a LiFePO4 cathode. We demonstrate that the membrane containing Al2 O3 -ST ceramic filler performs well in terms of ionic conductivity, thermal properties, and lithium transference number. Furthermore, we show that the lithium cells, which use the new electrolyte together with the LiFePO4 electrode, operate within 65 and 90 °C with high efficiency and long cycle life. Hence, the Al2 O3 -ST ceramic can be efficiently used as a ceramic filler to enhance the performance of solid polymer electrolytes in lithium batteries.

Stripping voltammetric determination of pyridine-2-aldoxime methochloride at the iron(III) doped zeolite modified glassy carbon electrode.

An iron(III) doped zeolite modified glassy carbon electrode was constructed for the determination of pyridine-2-aldoxime methochloride. X-ray diffraction and chemical analysis were utilized to determine the optimum pH and chemical content for doping zeolite. Cyclic voltammetry was used to characterize the modified electrode and study the kinetics of the acid treated and untreated modified electrode. Acid treatment of the modified electrode showed a better electrochemical behavior compared to the untreated iron(III) doped zeolite modified electrode. Square wave anodic stripping voltammetry was employed to investigate the working pH and preconcentration time. The analytical performance of the modified electrode was evaluated, and a linear anodic stripping response for pyridine-2-aldoxime methochloride in the concentration range of 0.5-100.0 µM with a detection limit of 1.61 × 10(-7) M was obtained. Finally, the developed method was successfully applied for the determination of pyridine-2-aldoxime methochloride in a biological sample.

Polymer-modified glassy carbon electrode for the electrochemical detection of quinine in human urine and pharmaceutical formulations.

Glassy carbon electrode was modified by electropolymerization of 4-amino-3-hydroxynaphthalene sulfonic acid. Cyclic voltammetric study of quinine showed higher current response at the modified electrode compared to the bare and activated glassy carbon electrodes in pH 7.0 phosphate buffer solution. Under optimized conditions, a calibration curve was obtained by square wave voltammetry at the modified electrode. The linear relationship between the peak current and the concentration of quinine in the range of 1.0 × 10(-7) to 1.0 × 10(-5) M was I (pa) (in microamperes) = 6.26C (in micromolars) + 0.2997 (R (2) = 0.999). The detection limit calculated (S/N = 3) was 1.42 × 10(-8) M, which is much lower than similar reports. The method was successfully applied for the determination of quinine in spiked human urine, and pharmaceutical formulations and recovery values >90 % were obtained.

Polymer modified glassy carbon electrode for the electrochemical determination of caffeine in coffee.

4-Amino-3-hydroxynaphthalene sulfonic acid (AHNSA) was electropolymerized on a glassy carbon electrode. The deposited film showed electrocatalytic activity towards the oxidation of caffeine. The polymer-modified electrode showed high sensitivity, selectivity and stability in the determination of caffeine in coffee. The peak current increased linearly with the concentration of caffeine in the range of 6 × 10(-8) to 4 × 10(-5) mol L(-1), with a detection limit of 1.37 × 10(-7) mol L(-1) (LoD = 3δ/slope). Analysis of caffeine in coffee was affected neither by sample matrices nor by structurally similar compounds. Recoveries ranging between 93.75 ± 2.32 and 100.75 ± 3.32 were achieved from coffee extracts indicating the applicability of the developed method for real sample analyses.

Simultaneous determination of N-acetyl-p-aminophenol and p-aminophenol with poly(3,4-ethylenedioxythiophene) modified glassy carbon electrode.

A sensitive and selective method was developed for the determination of N-acetyl-p-aminophenol (APAP) and p-aminophenol (PAP) using poly(3,4-ethylenedioxythiophene) (PEDOT)-modified glassy carbon electrode (GCE). Cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical reaction of APAP and PAP at the modified electrode. Both APAP and PAP showed quasireversible redox reactions with formal potentials of 367 mV and 101 mV (vs. Ag/AgCl), respectively, in phosphate buffer solution of pH 7.0. The significant peak potential difference (266 mV) between APAP and PAP enabled the simultaneous determination both species based on differential pulse voltammetry. The voltammetric responses gave linear ranges of 1.0×10(-6)-1.0×10(-4) mol L(-1) and 4.0×10(-6)-3.2×10(-4) mol L(-1), with detection limits of 4.0×10(-7) mol L(-1) and 1.2×10(-6) mol L(-1) for APAP and PAP, respectively. The method was successfully applied for the determination of APAP and PAP in pharmaceutical formulations and biological samples.