•Optimized surface conditions for the immobilization of an expressive amount of active acetylcholinesterase.•The carbaryl pesticide detection follows a Langmuir isotherm with high affinity adsorption ...constant.•Simple and straightforward methodology to immobilize a high density of active acetylcholinesterase.•Acetylcholinesterase with the active site close to the interface enabling a fast direct electron transfer.•Enzymatic electrochemical biosensor with low LOD and high sensitivity toward the determination of carbaryl pesticide.
Efficient and portable sensors are required to monitor and evaluate pesticide contaminants in the environment, food supply and biological fluids. In this work, a study of indigo carmine and dodecyl sulphate doped polypyrrole - gold nanoparticle nanocomposite films revealed changes during the polymerization that optimized the surface conditions for the immobilization of acetylcholinesterase enzyme (from electric eel), leading to improved catalytic performance. The results suggest a similar behavior to AChE from electric ray, as previously reported in a theoretical study, where the active site is orientated closer to the electrode when the enzyme is immobilized on a positively charged surface, promoting faster direct electron transfer. In addition, this interaction allows the immobilization of an expressive amount of active enzymes. The lack of hindrance led to a high binding interaction of the analyte (carbaryl) towards the adsorption sites of the enzyme (Langmuir isotherm constant of 7.39 × 108). This electrochemical enzymatic biosensor presented linear responses ranging from 0.05 to 0.25 ng mL−1 for carbaryl (a wide spectrum insecticide), with a detection limit of 0.033 ng cm2 mL−1, quantification limit of 0.11 ng cm2 mL-1 and sensitivity of -59.5 × 103A cm-2 mL g−1. The biosensor showed good intra-electrode repeatability and inter-electrode reproducibility with the relative standard deviation of 1.8 % and 3.7 % towards thiocholine oxidation and carbaryl pesticide detection, respectively. The biosensor stability improved when stored at lower temperature (-15 °C).
Climate change and the demand for clean energy have challenged scientists worldwide to produce/store more energy to reduce carbon emissions. This work proposes a conductive gel biopolymer electrolyte ...to support the sustainable development of high‐power aqueous supercapacitors. The gel uses saline water and seaweed as sustainable resources. Herein, a biopolymer agar‐agar, extracted from red algae, is modified to increase gel viscosity up to 17‐fold. This occurs due to alkaline treatment and an increase in the concentration of the agar‐agar biopolymer, resulting in a strengthened gel with cohesive superfibres. The thermal degradation and agar modification mechanisms are explored. The electrolyte is applied to manufacture sustainable and flexible supercapacitors with satisfactory energy density (0.764 Wh kg−1) and power density (230 W kg−1). As an electrolyte, the aqueous gel promotes a long device cycle life (3500 cycles) for 1 A g−1, showing good transport properties and low cost of acquisition and enabling the supercapacitor to be manufactured outside a glove box. These features decrease the cost of production and favor scale‐up. To this end, this work provides eco‐friendly electrolytes for the next generation of flexible energy storage devices.
Seaweed‐based was used as conductive gel for eco‐friendly supercapacitors, offering high energy, long life, and low cost. Manufacturing is glove‐box‐free, reducing costs and enabling scale‐up.
A simple and low-cost method is proposed to synthesize graphene oxide incorporated with silver nanoparticles. The inter-sheet distance was controlled by introducing hexylamine into the graphene oxide ...sheets. The materials were investigated by Raman, UV-vis and Fourier transform infrared spectroscopy, X-ray diffraction and field-emission scanning electron microscopy. The increase in inter-sheet distance, due to the presence of hexylamine, favored the growth of the silver nanoparticles within the sheets. We demonstrate that silver nanoparticles increased the electrical conductivity and capacitive properties of the graphene oxide based electrode. The high concentration of well dispersed silver nanoparticles on the surface of the graphene sheets resulted in ca. 90 times higher specific capacitance than bare graphene oxide, in addition to improved electrochemical activity. The proposed method is promising for the development of hybrid materials with enhanced properties for applications mainly in electrochemical energy storage devices.
Herein, polypyrrole (PPy) films are prepared via electrochemical deposition in a mixture of 1- n -butyl-3-methylimidazolium methanesulfonate (BMI·CH 3 SO 3 ) ionic liquid (IL) and dodecyl sulfate ...(DS). The physico-chemical properties of the films have been investigated by a wide range of characterization techniques. PPy films synthesized in DS or IL have shown larger and irregular granules as compared to PPy films prepared in the mixture of DS and IL. This result is related to the preferential dissolution of pyrrole monomers in micelle templates formed by the IL and a co-assembly of IL and dodecyl-sulfate (DS), thereby decreasing the granule size and affecting the structural arrangement of the polymer chain. The template behavior of the IL in combination with DS promotes the selective formation of polaron and bipolaron states in the PPy films. This effect has been investigated by UV-Vis spectrophotometry, Raman spectroscopy, electrochemical impedance spectroscopy (EIS), cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, and electrical conductivity measurements. The synergy of IL–DS has helped to decrease the resistivity of the PPy film from 2.17 × 10 2 Ω cm for PPy–IL to 2.44 Ω for PPy–IL–DS. EIS has also shown a decreased interfacial charge transfer resistance for PPy–IL–DS when compared to PPy–IL. The cyclic voltammetry curves have shown that the PPy films are electrocatalytically active for the I − /I 3 − redox reaction, and therefore, can be applied as a counter electrode (CE) in dye sensitised solar cells. The PPy based CEs resulted in nearly the same photocurrent and energy conversion efficiencies as that obtained from a conventional Pt CE.
The development of efficient advanced functional materials is highly dependent on properties such as morphology, crystallinity, and surface functionality. In this work, hierarchical flowerlike ...nanostructures of SrTiO3 have been synthesized by a simple template-free solvothermal method involving poly(vinylpyrrolidone) (PVP). Molecular dynamics simulations supported by structural characterization have shown that PVP preferentially adsorbs on {110} facets, thereby promoting the {100} facet growth. This interaction results in the formation of hierarchical flowerlike nanostructures with assembled nanosheets. The petal morphology is strongly dependent on the presence of PVP, and the piling up of nanosheets, leading to nanocubes, is observed when PVP is removed at high temperatures. This work contributes to a better understanding of how to control the morphological properties of SrTiO3, which is fundamental to the synthesis of perovskite-type materials with tailored properties.
Ionic silsesquioxane-capped gold nanoparticle powders presenting narrow size distribution were synthesised, characterised and applied in the assembly of organic solar cells. The assembled devices ...were electrically modelled, and the nanoparticles encapsulated with a charged pendant silsesquioxane were found to provide enhanced photocurrent, and to result in better electrical properties than those capped with bridged double-charged silsesquioxane. Therefore, thinner layers of encapsulation result in higher efficiency.
The development of efficient advanced functional materials is highly dependent on properties such as morphology, crystallinity, and surface functionality. In this work, hierarchical flowerlike ...nanostructures of SrTiO
have been synthesized by a simple template-free solvothermal method involving poly(vinylpyrrolidone) (PVP). Molecular dynamics simulations supported by structural characterization have shown that PVP preferentially adsorbs on {110} facets, thereby promoting the {100} facet growth. This interaction results in the formation of hierarchical flowerlike nanostructures with assembled nanosheets. The petal morphology is strongly dependent on the presence of PVP, and the piling up of nanosheets, leading to nanocubes, is observed when PVP is removed at high temperatures. This work contributes to a better understanding of how to control the morphological properties of SrTiO
, which is fundamental to the synthesis of perovskite-type materials with tailored properties.
Treads of scrap tires present low contents of inorganic fillers and a large amount of carbon black. In this work, this material was treated with potassium hydroxide and zinc chloride followed by ...pyrolysis at 500 and 700 °C. The ability to remove methylene blue and methyl orange were investigated under environmental conditions of pH and concentration. Carbons obtained with KOH at 700 °C present superior adsorption capacity. A simulation of this process permitted the characterization of the gases which contributed to surface development. The obtained products present a mesoporous structure and narrow particle size distribution. The presence of contaminants originated from these carbons was investigated in the aqueous media. The absence of zinc and sulfur releasing and the excellent ability to remove organic dye make these materials useful in the treatment of waste water.
Herein, polypyrrole (PPy) films are prepared
via
electrochemical deposition in a mixture of 1-
n
-butyl-3-methylimidazolium methanesulfonate (BMI·CH
3
SO
3
) ionic liquid (IL) and dodecyl sulfate ...(DS). The physico-chemical properties of the films have been investigated by a wide range of characterization techniques. PPy films synthesized in DS or IL have shown larger and irregular granules as compared to PPy films prepared in the mixture of DS and IL. This result is related to the preferential dissolution of pyrrole monomers in micelle templates formed by the IL and a co-assembly of IL and dodecyl-sulfate (DS), thereby decreasing the granule size and affecting the structural arrangement of the polymer chain. The template behavior of the IL in combination with DS promotes the selective formation of polaron and bipolaron states in the PPy films. This effect has been investigated by UV-Vis spectrophotometry, Raman spectroscopy, electrochemical impedance spectroscopy (EIS), cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, and electrical conductivity measurements. The synergy of IL-DS has helped to decrease the resistivity of the PPy film from 2.17 × 10
2
Ω cm for PPy-IL to 2.44 Ω for PPy-IL-DS. EIS has also shown a decreased interfacial charge transfer resistance for PPy-IL-DS when compared to PPy-IL. The cyclic voltammetry curves have shown that the PPy films are electrocatalytically active for the I
−
/I
3
−
redox reaction, and therefore, can be applied as a counter electrode (CE) in dye sensitised solar cells. The PPy based CEs resulted in nearly the same photocurrent and energy conversion efficiencies as that obtained from a conventional Pt CE.
Herein, polypyrrole films are prepared
via
electrochemical deposition in a mixture of 1-
n
-butyl-3-methylimidazolium methanesulfonate ionic liquid and dodecy sulfate.
To provide a viable alternative for counter electrodes used in dye sensitized solar cells, polypyrrole (PPy) based films have been synthesized via electrochemical deposition in the presence of the ...ionic liquid 1-butyl-3-methylimidazolium bis-(trifluoromethanesulfonyl) imidate (NTf2) and incorporated with gold nanoparticles (Aunanop). The films were analyzed by SEM, UV-Vis-NIR, Raman, Electrochemical impedance spectroscopy, Cyclic voltammetry and Conductivity measurements. The presence of the ionic liquid is found to result in a more conductive film, to improve catalytic reduction of I3− and the electrochemical reversibility of the electrode. In addition to increase conductivity, impedance spectroscopy has shown that incorporating Aunanop in the PPy/NTf2 film helps improving the interfacial charge transportation, the electrocatalytic properties and solar energy conversion efficiency. DSSCs assembled with PPy based CE presented nearly the same J-V characteristic parameters as observed from conventional Pt based device.
PDF
