Ultrastrong Nanopapers with Aramid Nanofibers and Silver Nanowires Reinforced by Cellulose Nanofibril-Assisted Dispersed Graphene Nanoplates for Superior Electromagnetic Interference Shielding.

High-strength, lightweight, ultrathin, and flexible electromagnetic interference (EMI) shielding materials with a high shielding effectiveness (SE) are essential for modern integrated electronics. Herein, cellulose nanofibrils (CNFs) are employed to homogeneously disperse graphene nanoplates (GNPs) into an aramid nanofiber (ANF) network and silver nanowire (AgNW) network, respectively, producing high-performance nanopapers. These nanopapers, featuring nacre-mimetic microstructures and layered architectures, exhibited high tensile strength (601.11 MPa) and good toughness (103.56 MJ m-3) with a thickness of only 24.58 µm. Their specific tensile strength reaches 447.59 MPa·g-1·cm3, which is 1.74 times that of titanium alloys (257 MPa·g-1·cm3). The AgNW/GNP composite conductive layers exhibit an electrical conductivity of 12010.00 S cm-1, providing the nanopapers with great EMI shielding performance, achieving an EMI SE of 63.87 dB and an EMI SE/t of 25978.80 dB cm-1. The nanopapers also show reliable durability, retaining a tensile strength of 500.96 MPa and an EMI SE of 57.59 dB after 120,000 folding cycles. Additionally, they have a good electrical heating performance with a fast response time, low driving voltage, effective deicing capability, and reliable heating capacity in water. This work presents a strategy to develop a high-performance nanopaper, showing great potential for applications in electromagnetic compatibility, national defense, smart electronics, and human health.

Dialdehyde Cellulose Solution as Reducing Agent: Preparation of Uniform Silver Nanoparticles and In Situ Synthesis of Antibacterial Composite Films with High Barrier Properties.

The demand for antimicrobial materials is gradually increasing due to the threat of infections and diseases caused by microorganisms. Silver nanoparticles (AgNPs) are widely used because of their broad-spectrum antimicrobial properties, but their synthesis methods are often environmentally harmful and AgNPs difficult to isolate, which limits their application in several fields. In this study, an aqueous solution of dialdehyde cellulose (DAC) was prepared and used as a reducing agent to synthesize AgNPs in an efficient and environmentally friendly process. The synthesized AgNPs can be easily separated from the reducing agent to expand their applications. In addition, the AgNPs were immobilized in situ on dialdehyde cellulose to form antibacterial composite films. The results showed that the prepared silver nanoparticles were mainly spherical and uniformly dispersed, with an average size of about 25 nm under optimal conditions. Moreover, the dialdehyde cellulose-nanosilver (DAC@Ag) composite films had excellent mechanical properties, positive transparency, ultraviolet-blocking properties, and effective antibacterial activity against E. coli and S. aureus. Notably, the composite films exhibited excellent oxygen and water vapor barrier properties, with WVT and ORT of 136.41 g/m2·24 h (30 °C, 75% RH) and <0.02 cm3/m2·24 h·0.1 MPa (30 °C, 75% RH), respectively, better than commercial PE films. Hence, this study not only provides an environmentally friendly method for the preparation of silver nanoparticles, but also offers a simple and novel strategy for the in situ synthesis of silver-loaded antibacterial composite films.

Mechanically Strong Electrically Insulated Nanopapers with High UV Resistance Derived from Aramid Nanofibers and Cellulose Nanofibrils.

Aramid nanofibers (ANFs) have great potential for civil and military applications due to their remarkable mechanical modulus, excellent chemical reliability, and superior thermostability. Unfortunately, the weak combination of neighboring ANFs limits the mechanical properties of ANF-based materials owing to their inherent rigidity and chemical inertness. Herein, high-performance nanopapers are fabricated by introducing a tiny amount of cellulose nanofibrils (CNFs) to serve as reinforcing blocks via vacuum filtration. As a result of the formation of nanosized building blocks and hydrogen-bonding interaction of CNFs, the resultant ANF/CNF nanopaper yields a record-high tensile strength (406.43 ± 16.93 MPa) and toughness (86.13 ± 5.22 MJ m-3), which are 1.8 and 4.3 times higher than those of the pure ANF nanopaper, respectively. When normalized by weight, the specific tensile strength of the nanopaper is as high as 307.90 MPa·g-1·cm3, which is even significantly superior to that of titanium alloys (257 MPa·g-1·cm3). The ANF/CNF nanopaper also possesses excellent dielectric strength (53.42 kV mm-1), superior UV-shielding performance (≥99.999% absorption for ultraviolet radiation), and a favorable thermostability (Tonset = 530 °C). This study proposes a new design strategy for developing ultrathin ANF-based nanopapers combined with high reliability and thermostability for application in high-end electrical insulation fields, such as 5G communication, wearable electronics, and artificial intelligence.

Cellulose nanofibrils (CNFs) produced by different mechanical methods to improve mechanical properties of recycled paper.

In current study, CNFs produced by different mechanical methods, were used to improve the mechanical properties of recycled paper. The result showed the morphology of CNFs had great impact on reinforced effect and the length of fibrils determined their contribution in recycled paper strength. For different CNFs with similar diameter, the higher aspect ratio resulted in better reinforced effect. The CNFs produced by microfluidic homogenization and suitable PFI milling conditions (RM-CNF1) got best reinforced effect which improved tensile index and burst index by 35.5 % and 49.4 % at 5.0 wt% addition, respectively, due to their high aspect ratio. Although the CNFs produced by ball milling and ultrasonication (BU-CNF2) still had many bundles that were not fibrillated completely, their reinforced effect just below RM-CNF1 due to their special morphology and high retention rate. This work aims to study the influence of CNFs on recycled fibers reinforcement.

Scalable and Robust Bacterial Cellulose Carbon Aerogels as Reusable Absorbents for High-Efficiency Oil/Water Separation.

Efficient selective separation of oils or organic pollutants from water is important for ecological, environmental conservation and sustainable development. Various absorption methods have emerged; the majority of them still suffer from defects including low removal efficiency, a complicated preparation process, and high cost. Herein, we present a highly porous and mechanical resilient bacterial cellulose (BC) carbon aerogel directly from BC hydrogel via facile directional freeze-drying and high-temperature carbonization. The resultant BC carbon aerogel showed excellent mechanical compressibility (maximal height compression ∼99.5%) and elastic recovery due to the porous structure. Taking advantages of the high thermal stability and superhydrophobicity, the BC carbon aerogel was directly used as a versatile adsorbent for oil/water separation. The result demonstrated that the BC carbon aerogel showed super oil/water separation selectivity with the oil absorption capacity as high as 132-274 g g-1. More importantly, the BC carbon aerogel adsorbent can be reused by a simple absorption/combustion method and still keep high-efficiency oil absorption capacity and excellent superhydrophobicity after 20 absorption/combustion cycles, displaying recyclability and robust stability. In sum, the BC carbon aerogel introduced here is easy to fabricate, ecofriendly, highly scalable, low cost, mechanically robust, and reusable; all of these features make it highly attractive for oil/water separation application.