Glucose/O2 biofuel cell based on enzymes, redox mediators, and Multiple-walled carbon nanotubes deposited by AC-electrophoresis then stabilized by electropolymerized polypyrrole

The Interpretation of Carbon Nanotubes' Electrochemistry: Electrocatalysis and Mass Transport Regime in the Apparent Promotion of Electron Transfer

Carbon nanotubes (CNTs) are widely used in electrochemical sensors due to their significant impact on the electroanalytical signal. However, there remain significant doubts regarding the origin of the improved electroanalytical response observed in CNT-based sensors, particularly concerning the precise role of CNTs in these systems. In particular, the origin of the electrochemical response is controversial, as it may be due to either electrocatalytic or non-electrocatalytic processes. The latter implies that the electroanalytical response is mainly governed by the mass transport phenomena within the porous CNT layer. This article briefly reviews the several comprehensive models based on the role of porosity (diffusion in a 'thin-layer') on the electrochemical behavior as well as on the electrocatalytic properties of CNTs to resolve conflicts arising from misinterpretations of the electroanalytical response of CNT-based sensors. However, even though there are some explanations and conclusions on this topic, they seem to be valuable for specific electroactive species, the type of CNTs and/or electrode architecture, the electrode surface, etc. Accordingly, general theories and conclusions are not yet defined, so different approaches to this topic are still needed, since the main phenomenological effects responsible for the nature of the electrochemical response of the electrodes modified with CNTs need to be determined in a rational way.

Microbial Fuel Cell-Based Biosensors and Applications

The sustainable development of human society in today's high-tech world depends on some form of eco-friendly energy source because existing technologies cannot keep up with the rapid population expansion and the vast amounts of wastewater that result from human activity. A green technology called a microbial fuel cell (MFC) focuses on using biodegradable trash as a substrate to harness the power of bacteria to produce bioenergy. Production of bioenergy and wastewater treatment are the two main uses of MFC. MFCs have also been used in biosensors, water desalination, polluted soil remediation, and the manufacture of chemicals like methane and formate. MFC-based biosensors have gained a lot of attention in the last few decades due to their straightforward operating principle and long-term viability, with a wide range of applications including bioenergy production, treatment of industrial and domestic wastewater, biological oxygen demand, toxicity detection, microbial activity detection, and air quality monitoring, etc. This review focuses on several MFC types and their functions, including the detection of microbial activity.

Urchin-like PtNPs@Bi2S3: synthesis and application in electrochemical biosensor

Novel urchin-like Pt nanoparticles@Bi2S3 composite materials were prepared by a simple route. The composite nanomaterial was used to modify an electrode for the immobilization of enzyme molecules to construct a sensitive electrochemical biosensor.

Review of Electrochemically Triggered Macromolecular Film Buildup Processes and Their Biomedical Applications

Macromolecular coatings play an important role in many technological areas, ranging from the car industry to biosensors. Among the different coating technologies, electrochemically triggered processes are extremely powerful because they allow in particular spatial confinement of the film buildup up to the micrometer scale on microelectrodes. Here, we review the latest advances in the field of electrochemically triggered macromolecular film buildup processes performed in aqueous solutions. All these processes will be discussed and related to their several applications such as corrosion prevention, biosensors, antimicrobial coatings, drug-release, barrier properties and cell encapsulation. Special emphasis will be put on applications in the rapidly growing field of biosensors. Using polymers or proteins, the electrochemical buildup of the films can result from a local change of macromolecules solubility, self-assembly of polyelectrolytes through electrostatic/ionic interactions or covalent cross-linking between different macromolecules. The assembly process can be in one step or performed step-by-step based on an electrical trigger affecting directly the interacting macromolecules or generating ionic species.

Fabrication of enzyme-based coatings on intact multi-walled carbon nanotubes as highly effective electrodes in biofuel cells

CNTs need to be dispersed in aqueous solution for their successful use, and most methods to disperse CNTs rely on tedious and time-consuming acid-based oxidation. Here, we report the simple dispersion of intact multi-walled carbon nanotubes (CNTs) by adding them directly into an aqueous solution of glucose oxidase (GOx), resulting in simultaneous CNT dispersion and facile enzyme immobilization through sequential enzyme adsorption, precipitation, and crosslinking (EAPC). The EAPC achieved high enzyme loading and stability because of crosslinked enzyme coatings on intact CNTs, while obviating the chemical pretreatment that can seriously damage the electron conductivity of CNTs. EAPC-driven GOx activity was 4.5- and 11-times higher than those of covalently-attached GOx (CA) on acid-treated CNTs and simply-adsorbed GOx (ADS) on intact CNTs, respectively. EAPC showed no decrease of GOx activity for 270 days. EAPC was employed to prepare the enzyme anodes for biofuel cells, and the EAPC anode produced 7.5-times higher power output than the CA anode. Even with a higher amount of bound non-conductive enzymes, the EAPC anode showed 1.7-fold higher electron transfer rate than the CA anode. The EAPC on intact CNTs can improve enzyme loading and stability with key routes of improved electron transfer in various biosensing and bioelectronics devices.

Membraneless glucose/O2 microfluidic enzymatic biofuel cell using pyrolyzed photoresist film electrodes

Biofuel cells typically yield lower power and are more difficult to fabricate than conventional fuel cells using inorganic catalysts. This work presents a glucose/O2 microfluidic biofuel cell (MBFC) featuring pyrolyzed photoresist film (PPF) electrodes made on silicon wafers using a rapid thermal process, and subsequently encapsulated by rapid prototyping techniques into a double-Y-shaped microchannel made entirely of plastic. A ferrocenium-based polyethyleneimine polymer linked to glucose oxidase (GOx/Fc-C6-LPEI) was used in the anode, while the cathode contained a mixture of laccase, anthracene-modified multi-walled carbon nanotubes, and tetrabutylammonium bromide-modified Nafion (MWCNTs/laccase/TBAB-Nafion). The cell performance was studied under different flow-rates, obtaining a maximum open circuit voltage of 0.54 ± 0.04 V and a maximum current density of 290 ± 28 μA cm(-2) at room temperature under a flow rate of 70 μL min(-1) representing a maximum power density of 64 ± 5 μW cm(-2). Although there is room for improvement, this is the best performance reported to date for a bioelectrode-based microfluidic enzymatic biofuel cell, and its materials and fabrication are amenable to mass production.