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This work presents the modification of glassy carbon electrodes (GCE) by using a dispersion resulting from the non-covalent functionalization of multi-walled carbon nanotubes (MWCNT) with polyarginine (polyArg). MWCNT-polyArg is used for the quantification of ascorbic acid (AA) in the presence of acetaminophen (APAP) and viceversa. Since ascorbic acid and acetaminophen are strongly absorbed on GCE/MWCNT-polyArg, they can be detected in the presence of 4.0×10 -5 M acetaminophen (and 3.0×10 -5 M ascorbic acid) by using adsorptive stripping with media exchange and differential pulse voltammetry. Using water as the solvent for the MWCNT dispersion, the result was Z-potential of 0.053 ± 0.006 V. The developed sensor showed excellent specificity, sensitivity, stability and reproducibility compared to previously published sensors. The GCE/MWCNT-polyArg sensor shows a fast response time of ∼5 minutes, low limits of detection and quantification for AA (0.95 and 2.9 μM respectively) and APAP (0.27 and 0.82μM, respectively), high sensitivity of 0.0616 μA/M for AA or APAP 0.240μA/M. It was used to test its practicability by determining the concentration of AA or APAP (AA and APAP) in pharmaceutical samples. Finally, the simultaneous measurement of ascorbic acid and acetaminophen in pharmaceuticals showed a good correlation, with a maximum error and RSD of 4.5 and 5.1 %, respectively., Competing Interests: Declaration of Competing Interest The authors declare no competing interests, (Copyright © 2024 Elsevier B.V. All rights reserved.)

Conventionally, the optimization of glucose biosensors is achieved by varying the concentrations of the individual reagents used to immobilize the enzyme. In this work, the effect and interaction between glucose oxidase enzyme (GOx), ferrocene methanol (Fc), and multi-walled carbon nanotubes (MWCNTs) at different concentrations were investigated by a design of experiments (DoE). For this analysis, a factorial design with three factors and two levels each was used with the software RStudio for statistical analysis. The data were obtained by electrochemical experiments on the immobilization of GOx-Fc/MWCNT at different concentrations. The results showed that the factorial DoE method was confirmed by the non-normality of the residuals and the outliers of the experiment. When examining the effects of the variables, analyzing the half-normal distribution and the effects and contrasts for GOx-Fc/MWCNT, the factors that showed the greatest influence on the electrochemical response were GOx, MWCNT, Fc, and MWCNT:Fc, and there is a high correlation between the factors GOx, MWCNT, Fc, and MWCNT:Fc, as shown by the analysis of homoscedasticity and multicollinearity. With these statistical analyses and experimental designs, it was possible to find the optimal conditions for different factors: 10 mM mL -1 GOx, 2 mg mL -1 Fc, and 15 mg mL -1 MWCNT show a greater amperometric response in the glucose oxidation. This work contributes to advancing enzyme immobilization strategies for glucose biosensor applications. Systematic investigation of DoE leads to optimized immobilization for GOx, enables better performance as a glucose biosensor, and allows the prediction of some outcomes., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.)

This article provides an overview of the work reported in the past decade in the field of microfluidic fuel cells. To develop appropriate research, the most commonly used electrocatalytic materials were considered and a new classification was proposed based on their nature: abiotic, hybrid, or biological. This classification allowed the authors to discern the information collected. In this sense, the types of electrocatalysts used for the oxidation of the most common fuels in different environments, such as glucose, ethanol, methanol, glycerol, and lactate, were presented. There are several phenomena presented in this article. This information gives an overview of where research is heading in the field of materials for electrocatalysis, regardless of the fuel used in the microfluidic fuel cell: the synthesis of abiotic and biological materials to obtain hybrid materials that allow the use of the best properties of each material., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

This systematic review presents the current state of research in the last five years on contaminants in soils, especially in leachates from solid waste landfills, with emphasis on biological remediation. In this work, the pollutants that can be treated by microorganisms and the results obtained worldwide were studied. All the data obtained were compiled, integrated, and analyzed by soil type, pollutant type, bacterial type, and the countries where these studies were carried out. This review provides reliable data on the contamination of soils worldwide, especially soils contaminated by leachate from municipal landfills. The extent of contamination, treatment objectives, site characteristics, cost, type of microorganisms to be used, and time must be considered when selecting a viable remediation strategy. The results of this study can help develop innovative and applicable methods for evaluating the overall contamination of soil with different contaminants and soil types. These findings can help develop innovative, applicable, and economically feasible methods for the sustainable management of contaminated soils, whether from landfill leachate or other soil types, to reduce or eliminate risk to the environment and human health, and to achieve greater greenery and functionality on the planet.

This work reports on Fe 2 O 3 and ZnO materials for lactate quantification. In the synthesis, the bi-phase γ-/α-Fe 2 O 3 and γ-/α-Fe 2 O 3 /ZnO nanoparticles (NPs) were obtained for their application in a lactate colorimetric sensor. The crystalline phases of the NPs were analyzed by XRD and XPS techniques. S/TEM images showed spheres with an 18 nm average and a needle length from 125 to 330 nm and 18 nm in diameter. The γ-/α-Fe 2 O 3 and γ-/α-Fe 2 O 3 /ZnO were used to evaluate the catalytic activity of peroxidase with the substrate 3,3,5,5-tetramethylbenzidine (TMB), obtaining a linear range of 50 to 1000 μM for both NPs, and a 4.3 μM and 9.4 μM limit of detection (LOD), respectively. Moreover, γ-/α-Fe 2 O 3 and γ-/α-Fe 2 O 3 /ZnO/lactate oxidase with TMB assays in the presence of lactate showed a linear range of 50 to 1000 µM, and both NPs proved to be highly selective in the presence of interferents. Finally, a sample of human serum was also tested, and the results were compared with a commercial lactometer. The use of ZnO with Fe 2 O 3 achieved a greater response toward lactate oxidation reaction, and has implementation in a lactate colorimetric sensor using materials that are economically accessible and easy to synthesize.

Ferrocene-based polymers as redox mediators are considered versatile and important in the study of glucose biosensors. Poly-L-lysine (PLL), as a cationic polymer, possesses good properties including biocompatibility, biodegradation and water solubility. In this work, PLL was modified with ferrocene carboxylate in a very simple way by activating the carboxyl group of Fc, which reacted with the amino groups of the polymer. The resulting product was analysed by FTIR. Performance as a redox mediator (Fc-PLL) with the enzyme glucose oxidase was tested by cyclic voltammetry and showed an increase in the oxidation current in the presence of glucose in PBS pH 7.4. Additionally, performance as a biosensor was evaluated by amperometry and gave a linear range of 0-10 mM, a limit of detection of 23 μM, a sensitivity of 6.55 μA/cm 2 mM and high selectivity. To evaluate the charged regions of Fc-PLL/GOx on the electrode surface, analysis by scanning electrochemical microscopy showed remarkable activity. The Fc-PLL redox polymer as a glucose biosensor has been well accepted as this kind of material, and the results showed remarkable activity as an electron transfer mediator between the redox polymer and the GOx enzyme., (Copyright © 2022 Elsevier B.V. All rights reserved.)

In this work, unsupported Pd aerogel catalysts were synthesized for the very first time by using microwaves as a heating source followed by a lyophilization drying process and used towards formic acid electro-oxidation in a microfluidic fuel cell. Aerogels were also made by heating in a conventional oven to evaluate the microwave effect during the synthesis process of the unsupported Pd aerogels. The performance of the catalysts obtained by means of microwave heating favored the formic acid electro-oxidation with H 2 SO 4 as the electrolyte. The aerogels' performance as anodic catalysts was carried out in a microfluidic fuel cell, giving power densities of up to 14 mW cm -2 when using mass loads of only 0.1 mg on a 0.019 cm 2 electrode surface. The power densities of the aerogels obtained by microwave heating gave a performance superior to the resultant aerogel prepared using conventional heating and even better than a commercial Pd/C catalyst.

In this work, atomically substituted three-dimensionally ordered macroporous (3DOM) spinels based on Co and Mn (MnCo 2 O 4 and CoMn 2 O 4 ) were synthetized and used as cathodic electrocatalysts in a primary Zn-air battery. Scanning/transmission electron microscopy images show a 3DOM structure for both materials. Skeleton sizes of 114.4 and 140.8 nm and surface areas of 65.3 and 74.6 m 2 g -1 were found for MnCo 2 O 4 and CoMn 2 O 4 , respectively. The increase in surface area and higher presence of Mn 3+ and Mn 4+ species in the CoMn 2 O 4 3DOM material improved battery performance with a maximum power density of 101.6 mW cm -2 and a specific capacity of 1440 mA h g -1 , which shows the highest battery performance reported to date using similar spinel materials. The stability performance of the electrocatalyst was evaluated in half-cell and battery cell systems, showing the higher durability of CoMn 2 O 4 , which was related to its better capability to perform the electrocatalytic process as adsorption, electron transfer, and desorption. It was found through density functional theory calculations that the CoMn 2 O 4 spinel has a higher density of states in the Fermi level vicinity and better conductivity. Finally, the unique shape of 3DOM spinels promoted a high interaction between electroactive species and catalytic sites, making them suitable for oxygen reduction reaction applications.

The aim of this work is the evaluation of a Sulfonated Poly Ether-Ether Ketone (S-PEEK) polymer modified by the addition of pure Santa Barbara Amorphous-15 (SBA-15, mesoporous silica) and SBA-15 previously impregnated with phosphotungstic acid (PWA) fillers (PWA/SBA-15) in order to prepare composite membranes as an alternative to conventional Nafion ® membranes. This component is intended to be used as an electrolyte in electrochemical energy systems such as hydrogen and methanol Proton Exchange Membrane Fuel Cell (PEMFC) and Electrochemical Hydrogen Pumping (EHP). The common requirements for all the applications are high proton conductivity, thermomechanical stability, and fuel and oxidant impermeability. The morphology of the composite membranes was investigated by Scanning Electron Microscopy- Energy Dispersive X-ray Spectroscopy (SEM-EDS) analysis. Water Uptake (Wup), Ion Exchange Capacity (IEC), proton conductivity, methanol permeability and other physicochemical properties were evaluated. In PEMFC tests, the S-PEEK membrane with a 10 wt.% SBA-15 loading showed the highest performance. For EHP, the inclusion of inorganic materials led to a back-diffusion, limiting the compression capacity. Concerning methanol permeability, the lowest methanol crossover corresponded to the composites containing 5 wt.% and 10 wt.% SBA-15.

The demand for hydrophobic polymer-based protective coatings to impart high corrosion resistance has increased recently. The increase of the hydrophobicity in a hybrid coating is a new challenge, for that reason and in order to protect a metallic surface of oxidant agents, a poly (methyl methacrylate) (PMMA) coating with the addition of a different amount of silicon dioxide (SiO 2 ) was developed. The hybrid coating was applied on a sample of stainless steel AISI 304 by the dip-coating method. The characterization of the coatings was determined by electrochemical impedance spectroscopy and with a scanning electrochemical microscopy. The best coatings were PMMA and PMMA + SiO 2 0.01% that exhibits a real impedance in the Nyquist diagram of 760 and 427,800 MΩ⋅cm 2 , respectively, and the modulus of the real impedance in the Bode diagram present values of 2.2 × 10 8 and 3.3 × 10 8 Ω⋅cm 2 . Moreover, the phase angle presents constant values around 75° to 85° and 85° for the PMMA and PMMA + SiO 2 0.01%, respectively. Moreover, the values of the real resistance for the PMMA + SiO 2 0.01% coating present values in the order of Mega-ohms despite the coating exhibits an artificial defect in their surface. The contact angle test showed that the hydrophobicity of the hybrid PMMA + SiO 2 0.01% coating is higher than that of the pure PMMA coatings. The hybrid PMMA + SiO 2 coatings developed in this work are a very interesting and promising area of study in order to develop efficient products to protect metallic surfaces from corrosion phenomenon.

Titanium oxide nanotubes (TNTs) were anodically grown in ethylene glycol electrolyte. The influence of the anodization time on their physicochemical and photoelectrochemical properties was evaluated. Concomitant with the anodization time, the NT length, fluorine content, and capacitance of the space charge region increased, affecting the opto-electronic properties (bandgap, bathochromic shift, band-edge position) and surface hydrophilicity of TiO 2 NTs. These properties are at the origin of the photocatalytic activity (PCA), as proved with the photooxidation of methylene blue.

The purpose of this work is to evaluate single and double-cell membraneless microfluidic fuel cells (MMFCs) that operate in the presence of simulated body fluids SBF, human serum and blood enriched with ethanol as fuels. The study was performed using the alcohol dehydrogenase enzyme immobilised by covalent binding through an array composed of carbon Toray paper as support and a layer of poly(methylene blue)/tetrabutylammonium bromide/Nafion and glutaraldehyde (3D bioanode electrode). The single MMFC was tested in a hybrid microfluidic fuel cell using Pt/C as the cathode. A cell voltage of 1.035V and power density of 3.154mWcm -2 were observed, which is the highest performance reported to date. The stability and durability were tested through chronoamperometry and polarisation/performance curves obtained at different days, which demonstrated a slow decrease in the power density on day 10 (14%) and day 20 (26%). Additionally, the cell was tested for ethanol oxidation in simulated body fluid (SBF) with ionic composition similar to human blood plasma. Those tests resulted in 0.93V of cell voltage and a power density close to 1.237mWcm -2 . The double cell MMFC (Stack) was tested using serum and human blood enriched with ethanol. The stack operated with blood in a serial connection showed an excellent cell performance (0.716mWcm -2 ), demonstrating the feasibility of employing human blood as energy source., (Copyright © 2017 Elsevier B.V. All rights reserved.)

A membraneless nanofluidic fuel cell with flow-through electrodes that works with several fuels (individually or mixed): methanol, ethanol, glycerol and ethylene-glycol in alkaline media is presented. For this application, an efficient Cu@Pd electrocatalyst was synthesized and tested, resulting outstanding performance until now reported, opening the possibility of power nano-devices for multi-uses purposes, regardless of fuel re-charge employed.

The use of three-dimensional flow-through nanoporous electrodes and the merging of a flow-through and air-breathing cathode were explored and successfully applied in a formic acid air-breathing nanofluidic fuel cell. The effects of fuel concentration, reaction stoichiometry and catalyst mass loading were investigated, resulting in power densities ranging from 28 to 100 mW cm(-2).

A hybrid glucose microfluidic fuel cell composed of an enzymatic cathode (Laccase/ABTS/C) and an inorganic anode (AuAg/C) was developed and tested. The enzymatic cathode was prepared by adsorption of 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and Laccase on Vulcan XC-72, which act as a redox mediator, enzymatic catalyst and support, respectively. The Laccase/ABTS/C composite was characterised by Fourier Transform Infrared (FTIR) Spectroscopy, streaming current measurements (Zeta potential) and cyclic voltammetry. The AuAg/C anode catalyst was characterised by Transmission electron microscopy (TEM) and cyclic voltammetry. The hybrid microfluidic fuel cell exhibited excellent performance with a maximum power density value (i.e., 0.45 mW cm(-2)) that is the highest reported to date. The cell also exhibited acceptable stability over the course of several days. In addition, a Mexican endemic Laccase was used as the biocathode electrode and evaluated in the hybrid microfluidic fuel cell generating 0.5 mW cm(-2) of maximum power density., (Copyright © 2014 Elsevier B.V. All rights reserved.)

AuPd/polyaniline was used for the first time, for ethylene glycol (EG) electrooxidation in a novel microfluidic fuel cell (MFC) operated at room temperature. The device exhibits high electrocatalytic performance and stability for the conversion of cheap and fully available EG as fuel.