Potential applications of deep eutectic solvents in nanotechnology

Transparent conducting films (TCFs) are a critical component in many personal electronic devices. Transparent and conductive doped metal oxides are widely used in industry due to their excellent optoelectronic properties as well as the mature understanding of their production and handling. However, they are not compatible with future flexible electronics developments where large-scale production will likely involve roll-to-roll manufacturing. Recent studies have shown that carbon nanotubes provide unique chemical, physical, and optoelectronic properties, making them an important alternative to doped metal oxides. This Review provides a comprehensive analysis of carbon nanotube transparent conductive films covering detailed fabrication methods including patterning of the films, chemical doping effects, and hybridization with other materials. There is a focus on optoelectronic properties of the films and potential in applications such as photovoltaics, touch panels, liquid crystal displays, and organic light-emitting diodes in conjunction with a critical analysis of both the merits and shortcomings of carbon nanotube transparent conductive films.

Recent Development of Carbon Nanotube Transparent Conductive Films

Chemically cross-linked cellulose nanocrystal aerogels represent a versatile and universal substrate on which to prepare lightweight hybrid materials. In situ incorporation of polypyrrole nanofibers, polypyrrole-coated carbon nanotubes, and manganese dioxide nanoparticles in the aerogels gives flexible 3D supercapacitor devices with excellent capacitance retention, low internal resistance, and fast charge-discharge rates.

Cellulose Nanocrystal Aerogels as Universal 3D Lightweight Substrates for Supercapacitor Materials

Amorphous nanostructured FeOOH and Co–Ni double hydroxides for high-performance aqueous asymmetric supercapacitors

Polypyrrole (PPy) is a promising pseudocapacitive material for supercapacitor electrodes. However, its poor cycling stability is the major hurdle for its practical applications. Here a two-prong strategy is demonstrated to stabilize PPy film by growing it on a functionalized partial-exfoliated graphite (FEG) substrate and doping it with β-naphthalene sulfonate anions (NS−). The PPy electrode achieves a remarkable capacitance retention rate of 97.5% after cycling between −0.8 and 0 V versus saturated calomel electrode for 10 000 cycles. Moreover, an asymmetric pseudocapacitor using the stabilized PPy film as anode also retains 97% of capacitance after 10 000 cycles, which is the best value reported for PPy-based supercapacitors. The exceptional stability of PPy electrode can be attributed to two factors: 1) the flexible nature of FEG substrate accommodates large volumetric deformation and 2) the presence of immobile NS− dopants suppresses the counterion drain effect during charge–discharge cycling.

Pushing the Cycling Stability Limit of Polypyrrole for Supercapacitors

Polypyrrole coated carbon nanotubes for supercapacitor devices with enhanced electrochemical performance

Sustainable isolation of nanocellulose from cellulose and lignocellulosic feedstocks: Recent progress and perspectives.

A conceptually new approach has been developed for the fabrication of composite polypyrrole (PPy)–multiwalled carbon nanotube (MWCNT) electrodes for electrochemical supercapacitors (ESs). The approach is based on the use of pyrocatechol violet (PV), eriochrome cyanine R (ECR) and acid fuchsin (AF) dyes as dispersants for MWCNTs and dopants for PPy polymerization. Testing results showed excellent electrochemical performance of the composite electrodes at high active mass loadings. The composite electrodes showed superior capacitance retention at high scan rates, compared to pure PPy electrodes. The comparison of the experimental data for the ES electrodes, prepared using different dyes, provided insight into the influence of their structure and functional groups on the composite microstructure and electrochemical performance. The use of ECR as a dispersant for MWCNTs and dopants for PPy allowed the fabrication of PPy coated MWCNTs. The fabrication method is simple and suitable for mass production. This new finding opens up a new and promising strategy for the fabrication of efficient ES electrodes and devices. The PPy coated MWCNTs were used for the fabrication of electrodes with a specific capacitance of 2.430–4.798 F cm−2 in the scan rate range of 2–100 mV s−1 for active mass loading of 18 mg cm−2. The ES cells showed high capacitance at different charge discharge rates and good cycling stability. The ES cells and modules showed promising performance for practical applications.

Anionic dopant–dispersants for synthesis of polypyrrole coated carbon nanotubes and fabrication of supercapacitor electrodes with high active mass loading

Ion conductors (ICs) have gained extensive research interest in various advanced application scenarios including sensors, batteries, and supercapacitors. However, stretchable, tough, and long‐term stable ICs are still hard to achieve yet highly demanded. In this study, the authors propose a one‐pot green and sustainable fabrication of cellulose based ICs through polymerizable deep eutectic solvents treated cellulose followed by an in situ photo‐polymerization. The obtained ICs exhibit extremely high stretchability (3210 ± 302%), high toughness (13.17 ± 2.32 MJ m−3), high transparency, and self‐healing ability. Notably, the introduction of cellulose fibers greatly enhances the mechanical properties of ICs while eliminating the environmental concerns of traditional nanocellulose fabrication process. More importantly, the ICs possess good long‐term performance stability after 1 month storage. Due to these outstanding properties, the feasibility of applying ICs in human motion sensing and physiological signal detecting is demonstrated. This simple and green method will contribute to the development of tough, self‐healing, transparent, and long‐term stable ICs.

Yeling Zhu

Papers

Polypyrrole coated carbon nanotubes for supercapacitor devices with enhanced electrochemical performance

Sustainable isolation of nanocellulose from cellulose and lignocellulosic feedstocks: Recent progress and perspectives.

Anionic dopant–dispersants for synthesis of polypyrrole coated carbon nanotubes and fabrication of supercapacitor electrodes with high active mass loading

Tough and Ultrastretchable Liquid‐Free Ion Conductor Strengthened by Deep Eutectic Solvent Hydrolyzed Cellulose Microfibers

Influence of dopant structure and charge on supercapacitive behavior of polypyrrole electrodes with high mass loading