Bioelectrochemistry

Design and Applications of Biomaterials

Serge Cosnier

• Publisher: De Gruyter
• Year: 2019
• eBook ISBN: 9783110569261
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Biochemistry
• Index: Technology & Engineering

Bioelectrochemistry is a fast growing field linking together electrochemistry, biochemistry, medicinal chemistry and analytical chemistry. The current book outlines the recent progress in the area and the applications in biological materials design and bioenergy, covering in particular biosensors, bioelectronic devices, biofuel cells, biodegradable batteries and biomolecule-based computing.

Andrew J. Gross, Michael Holzinger, Serge Cosnier

1 Buckypapers for bioelectrochemical applications

Andrew J. Gross, Michael Holzinger, Serge Cosnier: Department of Molecular Chemistry, Université Grenoble Alpes, Grenoble, France

1.1 Introduction to buckypapers for bioelectrochemistry

Buckypapers are self-supporting nanostructured thin films of entangled carbon nanotubes (CNTs), resembling an electronic paper, which are held together by π–π stacking and interweaving interactions. In 1998, Richard Smalley’s group was the first to report the formation of CNT sheets (coining the term “buckypaper”) as a method for characterizing the production quality of CNTs [1]. CNT buckypapers and their composites have excellent prospects for a wide range of applications from aerospace materials [2] to sensors [3, 4] and fuel cells [5, 6], and are thus of interest to a vast research and industrial community. Over the last 5–7 years, buckypaper materials have emerged for the construction of implantable, wearable, and portable bioelectronic devices owing to their properties including high conductivity and porosity, flexibility, lightweight, biocompatibility, and the ability for electron transfer with enzymes and microbes [7]. In addition to being used for enzymatic and microbial biofuel cell construction [7, 8, 9], buckypapers are also being used for hybrid supercapacitors [10], photoelectric biofuel cells [11], and other bioelectronic systems including biosensors [4, 12], bioreactors [13], and biologic devices [14].

Buckypaper is an accepted term for CNT sheets, disordered or aligned, formed by vacuum filtration of aqueous (e.g., in the presence of a nonionic surfactant such as Triton X-100) and nonaqueous dispersions (e.g., in N, N-dimethylformamide, DMF) of single-walled, double-walled, and multiwalled carbon nanotubes (SWCNTs, DWCNTs, and MWCNTs) [1, 6, 15]. Sonication, centrifugation, and additional filtration steps are also commonly used to improve the quality and purity of the CNT dispersion prior to filtration through a porous membrane [6, 15]. Finally, free-standing “lab-made” buckypaper sheets are obtained after washing, drying, and peeling from the underlying membrane. “Commercial” buckypaper prepared by continuous manufacturing is a popular type of buckypaper. The MWCNT buckypaper from Buckeye Composites (a division of NanoTechLabs, USA) is the most widely reported commercialized buckypaper for bioelectrochemical applications [16, 17, 18, 19]. In addition to vacuum filtration, lab-made buckypaper can also be prepared by methods including domino-pushing [20], CNT winding [21], and by using a lab-scale hand sheet former [22]. The most common types of buckypapers used in bioelectrochemistry are illustrated in Fig. 1.1.

Fabrication of buckypaper is conceptually straightforward, but factors such as dispersion homogeneity, CNT type and chemical functionality, membrane porosity, and the presence of additives in the dispersion all create differences with respect to material reproducibility and functionality. Several studies have focused on tuning the physical and mechanical properties of buckypaper such as porosity, Young’s modulus, hardness, and electrical conductivity [15, 22–30]. For example, Shen et al. investigated the length of CNTs and showed how this parameter strongly governed the viscoelasticity and permeability of buckypaper [30]. Whitby et al. demonstrated that the porosity of buckypaper could be tuned using different casting solvents [29]. Oh et al. revealed the crucial roles of CNT suspension concentration and filtration velocity for self-assembled alignment of buckypaper to enhance the mechanical properties [15]. In our recent electrochemical study, we compared the physical, chemical, electrochemical, and bioelectrocatalytic properties of lab-made and commercial buckypapers [16].

For bioelectrochemical applications, surfactant-free methods of producing buckypaper are highly desirable owing to the undesirable impact of residual surfactant on conductivity and biocompatibility risks such as cell lysis [6, 16, 29]. Buckypaper prepared from nonaqueous solvent DMF or alcohols without surfactant has been reported with success, for example, owing to improved CNT-solvent interactions and the possibility to dissolve a wide range of chemical modifiers [6, 22, 31, 32, 33]. However, the removal of nonaqueous solvents is crucial to minimize enzyme denaturation, microbe deactivation, and material toxicity, in particular for in vivo applications.

Fig. 1.1: Illustration of fabrication procedures for commercial and lab-made buckypaper via mass production and lab-scale vacuum filtration, respectively.

Porous 3D-nanostructured carbon structures based on CNTs [34], mesoporous carbons [35, 36], and carbon black [37] have become privileged conducting supports for bioelectrode design. Many of the best performing enzymatic bioelectrodes to date have been fabricated using CNTs due to their high specific surface area and exceptional electronic and mechanical properties, for example, that allow effective direct and mediated electron transfer with enzymes for bioelectrocatalysis [8, 34]. Porous 3D-nanostructured carbon electrodes are particularly attractive due to the high surface/volume ratio, which increases the loading of catalyst per geometric area. The size and curvature of pore and nanotube structures (e.g., nano-, micro-, and meso-pores) and their surface chemistry play a crucial role on the bioelectrocatalytic parameters of the electrode, such as mass transport, enzyme orientation and activity, and electron transfer kinetics [16, 35, 38, 39].

An important aspect that is frequently overlooked in bioelectrode design is the development of porous electrodes with practical physical properties for their target application. For example, for wearable biofuel cell and biosensor applications, “skin-like” electrodes that are soft, bendable, and even stretchable are required [40, 41]. For implantation, compact and lightweight electrodes are required with flexible geometries and superior stability and biocompatibility [7, 42]. Many bioelectrodes, including 3D-nanostructured electrodes, are prepared via the simple adsorption of nanocarbons (e.g., MgO-templated carbon [35], mesoporous nanoparticles [43], and Ketjen black [37]) onto robust but bulky and nonflexible glassy carbon supports. The resulting thin films can also be fragile and prone to delamination from the electrode. Bulk CNT “pellet” electrodes formed by compression in the presence of enzyme emerged as a more practical solution to glassy carbon-based electrodes for implantable biofuel cells; however, the pellet electrodes were still quite cumbersome, fragile, and brittle [44, 45]. For wearable applications, carbon electrodes based on printed CNT inks and pellets supported on a flexible substrate have been developed [46, 47].

Buckypaper is an alternative form of 3D-nanostructured electrode, which is the electrode itself (no support is required) and has attractive qualities for interfacing biological and electrochemical systems for bioelectrochemical applications [7]. Compared to the existing CNT pellet bioelectrodes, for example, buckypapers offer a higher density of CNTs per surface area and improved stability owing to their more compact structure. A comparison of the quantity of enzymes used per electrode also reveals that buckypapers are more economical than CNT pellet electrodes [6, 48]. Nevertheless, buckypapers do suffer from being brittle and fragile in several cases. In addition, lab-made fabrication of buckypapers can also require the use of significant amounts of organic solvent.

1.2 Biological fuel cell devices

One of the important applications of buckypaper is in the field of biofuel cells [7]. Buckypaper electrodes have been used in implanted bioelectronic devices since 2012. Notably, enzymatic biofuel cells based on commercial buckypaper have been implanted in different animals and used for in vivo energy harvesting and device powering via the organism [17, 49]. Biofuel cells are emerging power sources that can generate clean electrical energy from chemical substrates present in various media such as biofluids and en...

Table of contents

• Cover
• Title Page
• Copyright
• Contents
• List of contributors
• 1 Buckypapers for bioelectrochemical applications
• 2 Molecular electrocatalysts for carbon-based biofuels, H2 and O2 activation: an alternative to precious metals and enzymes in fuel cells
• 3 Electrospun biomaterials
• 4 Porous carbon materials for enzymatic fuel cells
• 5 DNA assembly for electrochemical biosensing
• 6 Biochemical sensing based on bipolar electrochemistry
• 7 Biomaterials for electrochemiluminescence
• 8 Signal-activated biomolecular release from alginate-modified electrodes
• 9 Self-powered electrochemical biosensors
• 10 Supercapacitors in bioelectrochemical systems
• 11 Wearable bioelectronic devices
• 12 Biodegradable electric power devices
• 13 Current trends for water treatment with microbial electrodes
• Index