Tomi Laurila

Hybrid nanoarchitectures that combine structural functionality of nanocellulose (NC) with electrical conductivity of carbon nanotubes (CNTs) are of growing interest for electroanalytical electrode design. However, CNT:NC hybrid film electrodes reported to date typically rely on separate conductive substrates, require binders, and rarely establish systematic relationships between processing, structure, and electrochemical performance. Here, we develop intrinsically conductive hybrid electrodes with a straightforward design, comprising current-collector-free, binder-free active layer from long-length single-wall carbon nanotubes (LLSWCNTs) and TEMPO-oxidized cellulose nanofibers (TOCNFs), fabricated on insulating support. To evaluate the influence of composition and processing parameters, films were prepared at three LLSWCNTs:TOCNFs mass ratios (1:1, 2:1, 3:1) and three postmixing sonication times (5, 10, 30 min). The films were subsequently characterized in terms of their structure, interfacial chemistry, and electroanalytical performance. Noncovalent interactions produced interconnected conductive LLSWCNTs networks embedded within an insulating TOCNFs scaffold, where electrical transport occurs through percolating interbundle contacts. Increasing LLSWCNTs content enhanced conductivity but densified the network, revealing a composition-dependent trade-off between charge and mass transfer. Extending postmixing reduced surface roughness and improved network homogeneity and charge-transfer kinetics. Electrochemical measurements demonstrated efficient outer-sphere electron transfer (k0 ∼ 0.4 × 10–2 cm s–1), a large electrochemically active surface area (ECSA = 0.053 ± 0.003 cm2), a wide potential window (ΔE = 2.41 ± 0.35 V in PBS), and significant pseudocapacitance (Cpseudo = 58.9 ± 7.7 μF cm–2), consistent with highly accessible porous electrode structures based on current collectors’ substrates. This work provides design guidelines for fabricating aqueous-processed nanostructured hybrid electrochemical sensors.

Self-standing electroactive thin films enable direct interrogation of intrinsic structure-composition-property relationships without contributions from external current collectors. Here, we report a bioderived hybrid thin film composed of single-walled carbon nanotubes (SWCNTs) and TEMPO-oxidized cellulose nanofibers (TOCNFs) that functions simultaneously as a conductive scaffold and an electrochemically active sensing interface. The hybrid architecture integrates the hydrophobic, conductive SWCNTs with the hydrophilic, carboxyl-functionalized TOCNF network to form a mechanically robust, porous film with composition-tunable interfacial charge and electron transfer properties. By systematically varying the SWCNT:TOCNF ratio and electrolyte conditions, we elucidate how hybrid composition governs charge distribution, redox probe accessibility, and electron transfer kinetics. The optimized self-standing films exhibit reproducible, composition-dependent electrochemical behavior and enable electrostatic discrimination between oppositely charged redox species. These findings provide mechanistic insight into charge-regulated electrochemistry in carbon nanotube–nanocellulose hybrids and establish composition-controlled charge regulation as a design principle for self-supporting electroactive thin films.

Ammonia (NH₃) is a widely used etchant gas in the plasma‐enhanced chemical vapor deposition (PECVD) synthesis of carbon nanofibers (CNFs). In addition to being an effective etchant, NH₃ also serves as a dopant by providing N heteroatoms. However, this secondary role has not been comprehensively investigated. Moreover, the influence of N‐doping on the electroanalytical performance of CNFs has not been thoroughly assessed. In this work, we have prepared CNFs of two varieties by altering the ratio of etchant and feedstock gases (NH₃ and C₂H₂, respectively), resulting in N‐doped CNFs with different doping levels. Differences were also observed in the morphology and electrochemical characteristics of the CNFs. While inner sphere redox (ISR) characteristics were not significantly affected, a significant shift between the peak potentials of ascorbic acid (AA) and dopamine (DA) was detected in the higher doped CNFs, resulting in enhanced selectivity towards DA. Our results demonstrate a simple yet effective method for enhancing the electroanalytical properties of CNFs.

Electrochemical detection of dopamine with MoS₂–Ni(OH)₂ thin films facilitated by a wireless, customizable and portable potentiostat.

Challenges in electrochemical aptamer-based (EAB) sensor development using carbon nanotube networks.