Conductive Nanopaper Research Articles

Multifunctional highly conductive cellulose nanopaper with ordered PEDOT:PSS alignment enabled by external surface area-promoted phase separation

Integrating cellulose, the most abundant biopolymer on Earth, with PEDOT:PSS, the most commercially available conducting polymer, can create multifunctional conductive nanopapers for sustainable electronics. However, conventional PEDOT:PSS/cellulose composites often exhibit limited conductivity, primarily due to the random distribution of PEDOT and the aggregation of PSS within the cellulose matrix. Herein, we introduce a confined phase separation approach that leverages the inherent physical characteristics of the cellulose substrate to enhance the performance of these composites. By systematically investigating the influence of the external surface area of nanocellulose on PEDOT:PSS coverage and composition evolution, we demonstrate that a higher external surface area ensures uniform PEDOT:PSS coating on nanocellulose networks and facilitates effective PSS removal during secondary doping. This process enhances phase separation and promotes ordered alignment of PEDOT chains along nanocellulose, resulting in an electrical conductivity of up to 252 S cm−1. Such highly conductive nanopapers exhibit exceptional performances in supercapacitors and electromagnetic shielding, achieving an ultrahigh specific electromagnetic shielding effectiveness of 33,122 dB cm2 g⁻1 at only 6 μm thickness. Our study highlights the critical role of cellulose substrate selection at the nanoscale and elucidates the interactions within conducting polymers, offering a promising pathway for developing high-performance, sustainable electronics.

Aminated nanocellulose-mediated synthesis of polyaniline/nanocellulose hybrid materials for sustainable conductive and supercapacitors nanopapers

Diamine-functionalized cellulose nanocrystals (DamCNCs) prepared by periodate oxidation and reductive amination were used as a scaffold for the in-situ oxidative polymerization of polyaniline (PANI). Unlike unmodified CNCs, the hybrid PANI/DamCNC particles formed a stable colloidal suspension over a large pH domain, PANI particles having nucleated and grown from the nanocrystals. The hybridization of PANI was validated by transmission electron microscopy images, along with Fourier-transform infrared, Raman, and UV–Vis spectra. By taking advantage of the colloidal stability of the PANI/DamCNC nanohybrids, flexible and freestanding thin nanopapers were prepared, with different contents in PANI/DamCNCs, using cationic or anionic cellulose nanofibrils (CCNFs or ACNFs, respectively). Conductive nanopapers were obtained by mixing CCNFs with PANI/DamCNCs at a content higher than 20 wt%, exhibiting high flexibility, mechanical integrity, transparency, and stability over time. This work proposes a simple process to fabricate a novel class of biobased conductive hybrid nanofiller based on PANI grafted on DamCNCs, stable in water, that may be used as an additive in nanocellulose suspensions to produce green flexible thin nanopapers, with potential use in different types of electronic devices such as electronic displays, smart packaging, or paper-based supercapacitors for energy storage.

Flexible freestanding conductive nanopaper based on PPy:PSS nanocellulose composite for supercapacitors with high performance

A freestanding, binder-free flexible polypyrrole: polystyrene sulfonate/cellulose nanopaper (PPy:PSS/CNP) electrode is successfully fabricated by a low-cost, simple, and fast vacuum filtration method for the first time. The hierarchical structure of CNP with high surface area and good mechanical strength not only provides a high electroactive region and shortens the diffusion distance of electrolyte ions, but also mitigates the volumetric expansion/shrinkage of the PPy during the charging/discharging process. The optimized PPy:PSS/CNP exhibits a high areal specific capacitance of 3.8 F cm−2 (corresponding to 475 F cm−3 and 240 F g−1) at 10 mV s−1 and good cycling stability (80.9% capacitance retention after 5000 cycles). The cyclic voltammetry curves of PPy:PSS/CNP at different bending angles indicate prominent flexibility and electrochemical stability of the electrode. Moreover, a symmetric supercapacitor device is assembled and delivers a high areal energy density of 122 µ cm−2 (15 W h cm−3) at a power density of 4.4 mW cm−2 (550 mW cm−3), which is superior to other cellulose-based materials. The combination of high supercapacitive performance, flexibility, easy fabrication, and cheapness of the PPy: PSS/CNP electrodes offers great potential for developing the next generation of green and economical portable and wearable consumer electronics.

Foldable and Recyclable Iontronic Cellulose Nanopaper for Low‐Power Paper Electronics

AbstractAn increase in the demand for the next generation of “Internet‐of‐Things” (IoT) has motivated efforts to develop flexible and affordable smart electronic systems, in line with sustainable development and carbon neutrality. Cellulose holds the potential to fulfil such demands as a low‐cost green material due to its abundant and renewable nature and tunable properties. Here, a cellulose‐based ionic conductive substrate compatible with printing techniques that combines the mechanical robustness, thermal resistance and surface smoothness of cellulose nanofibrils nanopaper with the high capacitance of a regenerated cellulose hydrogel electrolyte, is reported. Fully screen‐printed electrolyte‐gated transistors and universal logic gates are demonstrated using the engineered ionic conductive nanopaper and zinc oxide nanoplates as the semiconductor layer. The devices exhibit low‐voltage operation (<3 V), and remarkable mechanical endurance under outward folding due to the combination of the robustness of the nanopaper and the compliance of the semiconductor layer provided by the ZnO nanoplates. The printed devices and the ion‐conductive nanopaper can be efficiently recycled to fabricate new devices, which is compatible with the circular economy concept.

Nitro-oxidized carboxylated cellulose nanofiber based nanopapers and their PEM fuel cell performance

Sustainable and highly proton conductive nanopapers were prepared from carboxycellulose nanofibers and applied in PEM fuel cells.

Bispyrene Functionalization Drives Self-Assembly of Graphite Nanoplates into Highly Efficient Heat Spreader Foils.

Thermally conductive nanopapers fabricated from graphene and related materials are currently showing great potential in thermal management applications. However, thermal contacts between conductive plates represent the bottleneck for thermal conductivity of nanopapers prepared in the absence of a high temperature step for graphitization. In this work, the problem of ineffective thermal contacts is addressed by the use of bifunctional polyaromatic molecules designed to drive self-assembly of graphite nanoplates (GnP) and establish thermal bridges between them. To preserve the high conductivity associated to a defect-free sp2 structure, non-covalent functionalization with bispyrene compounds, synthesized on purpose with variable tethering chain length, was exploited. Pyrene terminal groups granted for a strong π–π interaction with graphene surface, as demonstrated by UV–Vis, fluorescence, and Raman spectroscopies. Bispyrene molecular junctions between GnP were found to control GnP organization and orientation within the nanopaper, delivering significant enhancement in both in-plane and cross-plane thermal diffusivities. Finally, nanopapers were validated as heat spreader devices for electronic components, evidencing comparable or better thermal dissipation performance than conventional Cu foil, while delivering over 90% weight reduction.

Rapid Processing of Holocellulose-Based Nanopaper toward an Electrode Material

Developing a flexible, lightweight, and sustainable electrode with low impedance, electromagnetic stability, long cycle life, and operational safety is essential for meeting the urgent demands for wearable and flexible equipment in contemporary society. Herein, we demonstrate a simple and scalable method to fabricate a high-performance and low-cost nanopaper based on holocellulose nanofiber and multiwalled carbon nanotubes in aqueous by vacuum filtration. Compared with cellulose-based nanopaper, the holocellulose-based nanopaper has distinct advantages such as being easy to fabricate, eco-friendly, and economical. The holocellulose nanofiber of wheat straw was obtained by a mechanical method which retained the natural core–shell structure with an ∼40 nm diameter and ∼3 μm length. Compared with cellulose-based nanopaper, the pure holocellulose nanopaper exhibited high toughness (1.97 × 10⁴ kJ/m³). The fabricated holocellulose-based conductive nanopaper exhibited a desirable electrical performance, including an electric conductivity of 0.72 S cm–¹, a high gravimetric capacitance of 271.99 F g–¹ at a current density of 50 mA g–¹, and cycling stability at a discharge current density of 100 mA g–¹ under room temperature. In addition, the holocellulose-based nanopaper demonstrated good thermal and dimensional stability. The holocellulose-based nanopaper showed these advantageous features of high physical flexibility, good electrochemical properties, and excellent mechanical properties, which are desirable for flexible electrodes, supercapacitors, and sensors.

Vapor phase polymerization for electronically conductive nanopaper based on bacterial cellulose/poly(3,4-ethylenedioxythiophene)

Eco-friendly conductive polymer nanocomposites have garnered attention as an effective alternative for conventional conductive nanocomposites. Here, we report the fabrication and optimization of flexible, self-standing, and conductive bacterial cellulose/poly(3,4-ethylene dioxythiophene) (BC/PEDOT) nanocomposites using the vapor phase polymerization (VPP) method. Eco-friendly bacterial cellulose (BC) is used as a flexible matrix, and the highly conductive PEDOT polymer is introduced into the BC matrix to achieve electronic conductivity. We demonstrate that vapor phase polymerized BC/PEDOT composites exhibit more than 10 times lower sheet resistance (18 Ω/square) compared to solution polymerized BC/PEDOT (188 Ω/square). The resultant BC/PEDOT fabricated could be bent up to 100 times and completely rolled up without a notable decrease in electronic performance. Moreover, bent BC/PEDOT films enable operation of a green light-emitting diode (LED) light, indicating the flexibility and stability of conductive BC/PEDOT films. Overall, this study suggests a strategy for the development of eco-friendly, flexible, and conductive nanocomposite films.

Nanopaper‐Based Organic Inkjet‐Printed Diodes

AbstractThe rise of internet of things (IoTs) applications has led to the development of a new generation of light‐weight, flexible, and cost‐effective electronics. These devices and sensors have to be simultaneously easily replaceable and disposable while being environmentally sustainable. Thus, the introduction of new functionalized materials with mechanical flexibility that can be processed using large‐area and facile fabrication methods (as, for example, printing technologies) has become a matter of great interest in the scientific community. In this context, cellulose nanofibers (CNFs) are renewable, affordable, robust, and nontoxic materials that are rapidly emerging as components for eco‐friendly electronics. Their combination with conductive polymers (CPs) to obtain conductive nanopapers (CNPs) allows moving their functionality from just substrates to active components of the device. In this work, a route for the inkjet‐printing of organic diodes is outlined. The proposed strategy is based on the use of CNPs as both substrates and bottom electrodes onto which insulator and organic semiconducting layers are deposited to fabricate novel diode structures. Remarkable rectification ratios of up to 1.2 × 103 at |3 V| and a current density up to 5.1 µA cm−2 are achieved. As a proof‐of‐concept of the potentiality of the approach for versatile, low‐temperature, and disposable sensing applications, an NO2 gas sensor is presented.

Assembling polymeric silver nanowires for transparent conductive cellulose nanopaper

Transparent conductive nanopaper was assembled by using PEDOT:PSS enhanced AgNW networks adsorbed on polydopamine functionalized nanocellulose.

Thermally and Electrically Conductive Nanopapers from Reduced Graphene Oxide: Effect of Nanoflakes Thermal Annealing on the Film Structure and Properties.

In this study, we report a novel strategy to prepare graphene nanopapers from direct vacuum filtration. Instead of the conventional method, i.e., thermal annealing nanopapers at extremely high temperatures prepared from graphene oxide (GO) or partially reduced GO, we fabricate our graphene nanopapers directly from suspensions of fully reduced graphene oxide (RGO), obtained after RGO and thermal annealing at 1700 °C in vacuum. By using this approach, we studied the effect of thermal annealing on the physical properties of the macroscopic graphene-based papers. Indeed, we demonstrated that the enhancement of the thermal and electrical properties of graphene nanopapers prepared from annealed RGO is strongly influenced by the absence of oxygen functionalities and the morphology of the nanoflakes. Hence, our methodology can be considered as a valid alternative to the classical approach.

Humidity-Sensitive and Conductive Nanopapers from Plant-Derived Proteins with a Synergistic Effect of Platelet-Like Starch Nanocrystals and Sheet-Like Graphene

In the present study, a multifunctional composite nanopaper was developed on the basis of soy protein isolate (SPI) from the synergistic reinforcement of sheet-like graphene (RGO) and platelet-like starch nanocrystals (SNCs), providing a conductive function as well as enhanced mechanical and barrier properties. As a highly crystalline and rigid nanoparticle derived from a natural polymer, the introduction of SNCs improved the dispersion of graphene nanoparticles at the relative ratio of 15/1 (SNC/RGO, w/w), and therefore promoted the electrical conductivity of the composite nanopapers under various humidity atmospheres. Because of hydrogen-bonding interactions from the surface groups, the effect of SNCs as a dispersing agent for RGO was investigated by rheological analysis of the composite suspensions and meanwhile directly observed by microscopy in the composite films. The proposed strategy of dual-enhanced fillers (with molecular interaction) in the composites can provide remarkable improvement of the p...

In-Plane Anisotropic Thermally Conductive Nanopapers by Drawing Bacterial Cellulose Hydrogels.

We developed flexible polymeric "heat-guiding materials" by simply drawing bacterial cellulose (BC) hydrogels to align the cellulose nanofibers and form "nanopapers" with anisotropic thermal conductivity. The in-plane anisotropy of thermal conductivity between the drawn and transverse directions increased as the draw ratio increased. For the drawn BC nanopapers, the coefficient of thermal expansion was found to be inversely correlated with the thermal diffusivity. We fabricated a planar spiral sheet by assembling the drawn BC strips to visualize the "heat flux controllability". The coexistence of heat-diffusing and heat-insulating capacities within the single nanopaper plane could help to cool future thin electronics.

Smart nanopaper based on cellulose nanofibers with hybrid PEDOT:PSS/polypyrrole for energy storage devices

In the current work, flexible, lightweight, and strong conductive nanopapers based on cellulose nanofibers (CNFs) with poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and/or polypyrrole (PPy) were prepared by following a mixing and in situ chemical polymerization method. A successful homogeneous coating of PEDOT:PSS on cellulose nanofibers occurred by means hydrogen-bonding interactions between the hydroxyl functionalized CNF and the electronically charged PEDOT:PSS, as shown by FTIR spectra. The electrical conductivity and the specific capacitance of CNF-PEDOT:PSS nanopapers were 2.58Scm−1 and 6.21Fg−1, respectively. Further coating of PPy produced a substantial improvement on the electrical conductivity (10.55Scm−1) and the specific capacitance (315.5Fg−1) of the resulting CNF-PEDOT:PSS-PPy nanopaper. A synergistic phenomenon between both conductive polymers supported the high electrical conductivity and specific capacitance of the ternary formulation. Moreover, CNF-PEDOT:PSS-PPy nanopaper showed higher mechanical properties and it was more flexible than the nanopaper containing only polypyrrole conducting polymer (CNF-PPy). It is concluded that the good mechanical, electrical and electrochemical properties of the ternary formulation can apply for smart nanopaper in flexible electronics and energy storage devices.

Foldable Electronic Devices: Highly Transparent Conducting Nanopaper for Solid State Foldable Electrochromic Devices (Small 46/2016)

Nanocellulose can be made into a highly transparent and conducting nanopaper substrate through an efficient and facile transfer method. This transparent conductive nanopaper easily withstands extreme folding and crumpling. Integrated with an active electrochrome material, a functional wearable camouflage skin tag that changes its color upon small voltage bias is prepared through electrochemical redox reaction by P. S. Lee and co-workers on page 6370.

Highly Transparent Conducting Nanopaper for Solid State Foldable Electrochromic Devices.

It is of great challenge to develop a transparent solid state electrochromic device which is foldable at the device level. Such devices require delicate designs of every component to meet the stringent requirements for transparency, foldability, and deformation stability. Meanwhile, nanocellulose, a ubiquitous natural resource, is attracting escalating attention recently for foldable electronics due to its extreme flexibility, excellent mechanical strength, and outstanding transparency. In this article, transparent conductive nanopaper delivering the state-of-the-art electro-optical performance is achieved with a versatile nanopaper transfer method that facilitates junction fusing for high-quality electrodes. The highly compliant nanopaper electrode with excellent electrode quality, foldability, and mechanical robustness suits well for the solid state electrochromic device that maintains good performance through repeated folding, which is impossible for conventional flexible electrodes. A concept of camouflage wearables is demonstrated using gloves with embedded electrochromics. The discussed strategies here for foldable electrochromics serve as a platform technology for futuristic deformable electronics.

Combined effect of carbon nanotubes and polypyrrole on the electrical properties of cellulose-nanopaper

In the present study, 2,2,6,6,-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibers (CNF) were combined with multi-walled carbon nanotubes (MWCNTs) and with hybrid MWCNT/polypyrrole to produce a variety of binary and ternary formulations of conductive nanopapers. By following a simple mixing/sonication/filtering process, a homogeneous and well-distributed CNF-MWCNT nanostructure was formed, resulting in a nanopaper of strong mechanical properties (141 MPa tensile strength and 9.41 GPa Young’s modulus) and good electrical conductivity (0.78 S cm−1), for the formulation with 50 wt% of MWCNT. The subsequent in situ polymerization of pyrrole in CNF-MWCNT mixtures produced ternary multiphase CNF-MWCNT-PPy nanopapers with much improved electrical conductivity (2.41 S cm−1) and electrochemical properties (113 F g−1 specific capacitance), even using little amounts of MWCNTs. With these materials, improved hybrid capacitors can be designed. The article presents a trend for the application of cellulose nanofibers in the field of green and flexible electronics.

Strong and electrically conductive nanopaper from cellulose nanofibers and polypyrrole

In this work, we prepare cellulose nanopapers of high mechanical performance and with the electrical conductivity of a semiconductor. Cellulose nanofibers (CNF) from bleached softwood pulp were coated with polypyrrole (PPy) via in situ chemical polymerization, in presence of iron chloride (III) as oxidant agent. The structure and morphology of nanopapers were studied, as well as their thermal, mechanical and conductive properties. Nanopaper from pure CNF exhibited a very high tensile response (224MPa tensile strength and 14.5GPa elastic modulus). The addition of up to maximum 20% of polypyrrole gave CNF/PPy nanopapers of high flexibility and still good mechanical properties (94MPa strength and 8.8GPa modulus). The electrical conductivity of the resulting CNF/PPy nanopaper was of 5.2 10−2Scm−1, with a specific capacitance of 7.4Fg−1. The final materials are strong and conductive nanopapers that can find application as biodegradable flexible thin-film transistor (TFT) or as flexible biosensor.

Silicon-conductive nanopaper for Li-ion batteries

There is an increasing interest in the development of thin, flexible energy storage devices for new applications. For large scale and low cost devices, structures with the use of earth abundant materials are attractive. In this study, we fabricated flexible and conductive nanopaper aerogels with incorporated carbon nanotubes (CNT). Such conductive nanopaper is made from aqueous dispersions with dispersed CNT and cellulose nanofibers. Such aerogels are highly porous with open channels that allow the deposition of a thin-layer of silicon through a plasma-enhanced CVD (PECVD) method. Meanwhile, the open channels also allow for an excellent ion accessibility to the surface of silicon. We demonstrated that such lightweight and flexible Si-conductive nanopaper structure performs well as Li-ion battery anodes. A stable capacity of 1200mAh/g for 100 cycles in half-cells is achieved. Such flexible anodes based on earth abundant materials and aqueous dispersions could potentially open new opportunities for low-cost energy devices, and potentially can be applied for large-scale energy storage.