Rose-Marie Latonen

The urgent need for renewable energy technologies has fuelled the exploration of biophotovoltaic devices (BPVs) that harness photosynthetic microorganisms, such as cyanobacteria, for solar-to-electricity conversion. To address the need for sustainable and scalable BPV power generation, the development of suitable electrode materials is crucial. In this study, we investigated electrically conducting few-layer graphene films and composites of graphene and cellulose nanocrystals (CNC) as potential BPVs anodes. Graphene and graphene–CNC electrodes were fabricated using a green liquid-phase shear exfoliation method in aqueous environments, employing sodium cholate (SC) surfactant solution or a CNC suspension, respectively, followed by spray-coating onto non-conductive glass substrates. Both CNC and SC are non-toxic, naturally derived, and renewable. Surface characterisation revealed hydrophilic films with nanoscale roughness, ideal for interfacing cyanobacterial cells. Cyclic voltammetry experiments demonstrated the electroactivity and stability of the electrodes in aqueous electrolyte solutions compatible with cyanobacteria. The photoelectrochemical performance of cyanobacterial cells on these electrodes was evaluated using a three-electrode electrochemical set-up. The graphene and graphene–CNC electrodes harvested photocharge densities over a 5 min period of 86.0 ± 32.0 μC cm⁻² and 52.8 ± 23.2 μC cm⁻², respectively; and with ferricyanide 339 ± 139 μC cm⁻² and 134 ± 79 μC cm⁻², respectively (photocurrent densities with ferricyanide of 2.17 ± 0.74 μA cm⁻² and 1.11 ± 0.60 μA cm⁻², respectively). Due to their abundant source materials and efficient fabrication method, few-layer graphene and graphene–CNC composites present a sustainable solution as anodes for renewable electricity generation in BPVs. This research provides a foundation for the advancement of cost-effective and environmentally friendly BPV technologies, thereby contributing to the reduction of fossil fuel dependence in energy generation.

One-dimensional (1D) nanomaterials of conductive polypyrrole (PPy) are competitive biomaterials for constructing bioelectronics to interface with biological systems. Synergistic synthesis using lignocellulose nanofibrils (LCNF) as a structural template in chemical oxidation of pyrrole with Fe(III) ions facilitates surface-confined polymerization of pyrrole on the nanofibril surface within a submicrometer- and micrometer-scale fibril length. It yields a core-shell nanocomposite of PPy@LCNF, wherein the surface of each individual fibril is coated with a thin nanoscale layer of PPy. A highly positive surface charge originating from protonated PPy gives this 1D nanomaterial a durable aqueous dispersity. The fibril-fibril entanglement in the PPy@LCNFs facilely supported versatile downstream processing, e.g., spray thin-coating on glass, flexible membranes with robust mechanics, or three-dimensional cryogels. A high electrical conductivity in the magnitude of several to 12 S·cm^-1 was confirmed for the solid-form PPy@LCNFs. The PPy@LCNFs are electroactive and show potential cycling capacity, encompassing a large capacitance. Dynamic control of the doping/undoping process by applying an electric field combines electronic and ionic conductivity through the PPy@LCNFs. The low cytotoxicity of the material is confirmed in noncontact cell culture of human dermal fibroblasts. This study underpins the promises for this nanocomposite PPy@LCNF as a smart platform nanomaterial in constructing interfacing bioelectronics.

Electrically conductive composite nanofibers were fabricated using poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT–PSS) and cellulose nanofibrils (CNFs) via the electrospinning technique. Poly(ethylene oxide) (PEO) was used to assist the electrospinning process, and poly(ethylene glycol) diglycidyl ether was used to induce chemical cross-linking, enabling stability of the formed fibrous mats in water. The experimental parameters regarding the electrospinning polymer dispersion and electrospinning process were carefully studied to achieve a reproducible method to obtain bead-free nanofibrous mats with high stability after water contact, with an electrical conductivity of 13 ± 5 S m^–1, thus making them suitable for bioelectrochemical applications. The morphology of the electrospun nanofibers was characterized by scanning electron microscopy, and the C/S ratio was determined with energy dispersive X-ray analysis. Cyclic voltammetric studies showed that the PEDOT–PSS/CNF/PEO composite fibers exhibited high electroactivity and high stability in water for at least two months. By infrared spectroscopy, the slightly modified fiber morphology after water contact was demonstrated to be due to dissolution of some part of the PEO in the fiber structure. The biocompatibility of the PEDOT–PSS/CNF/PEO composite fibers when used as an electroconductive substrate to immobilize microalgae and cyanobacteria in a photosynthetic bioelectrochemical cell was also demonstrated.

A water-based environmentally friendly electrically conducting ink composed of cellulose nanocrystals (CNC) and polyaniline (PANI) was prepared. PANI was synthesized by the emulsion polymerization approach using dodecylbenzenesulfonic acid (DBSA) as the dopant to induce spherical nanoparticulate formation. Glycerol was used to adjust the viscosity of the ink. The CNC–PANI ink was characterized by transmission electron microscopy, UV-visible spectroscopy and viscosity measurements. The ink was successfully printed on multilayer curtain coated paper by the flexographical printing method. The printed layers were characterized by optical and atomic force microscopy techniques and cyclic voltammetry. A stable nanoparticulate CNC–PANI ink with an electrical conductivity of the printed films between 30 and 60 S cm⁻¹ was obtained which was more than an order of magnitude higher than for the corresponding film without CNC.