Publications by authors named "Penggang Ren"

Article Synopsis
  • * Single metal-organic frameworks (MOFs) struggle to provide efficient EMW absorption across a wide frequency range due to their limitations in properties and structure.
  • * A new "sandwich-like" ternary MOF composite has been developed, which transforms into nitrogen-doped porous carbon with added metals and carbon nanotubes, significantly improving EMW absorption and expanding the effective absorption bandwidth (EAB) to between 6.1-18 GHz, with notable reflection loss values.
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Due to excellent flexibility and dispersibility, 2D graphene oxide (GO) is regarded as one of the prospective materials for preparing self-supporting electrode material. Nevertheless, the self-stacking characteristic of GO significantly restricts the ion transmission and accessibility in GO-based electrodes, especially in the direction perpendicular to the electrode surface. Herein, a novel composite film was fabricated from GO and 3D porous carbon (PC) through vacuum filtration combined with thermal reduction strategy.

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Ionic conductive hydrogels (ICHs) have attracted great attention because of their excellent biocompatibility and structural similarity with biological tissues. However, it is still a huge challenge to prepare a high strength, conductivity and durability hydrogel-based flexible sensor with dual network structure through a simple and environmentally friendly method. In this work, a simple one-pot cycle freezing thawing method was proposed to prepare ICHs by dissolving polyvinyl alcohol (PVA) and ferric chloride (FeCl) in cellulose nanofiber (CNF) aqueous dispersion.

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Preparing electrode material integrated with high gravimetric/volumetric capacitance and fast electron/ion transfer is crucial for the practical application. Owing to the structural contradiction, it is a big challenge to construct electrode material with high packing density, sufficient ion transport channels, and fast electronic transfer pathways. Herein, MnO porous carbon composite with abundant porous structure and 3D carbon skeleton was facilely fabricated from Linum usitatissimum.

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Chitosan and its derivatives are widely used in food packaging, pharmaceutical, biotechnology, medical, textile, paper, agriculture, and environmental industries. However, the flexibility of chitosan films is extremely poor, which limits its relevant applications to a large extent. In this paper, chitosan/sorbitol/nano-silica (CS/sorbitol/SiO) composite films were prepared by the casting film method using chitosan, sorbitol, Tween-80 and nano-SiO as raw materials.

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Titanium dioxide (TiO) is an ideal photocatalyst candidate due to its high activity, low toxicity and cost, and high chemical stability. However, its practical application in photocatalysis is seriously hindered by the wide band gap energy of TiO and the prone recombination of electron-hole pairs. In this study, C, N doped TiO were supported on spent coffee grounds-derived carbon (ACG) via in situ formation, which was denoted as C, N-TiO@ACG.

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Exploring electromagnetic interference (EMI) shielding materials with ultra-efficient EMI shielding effectiveness (SE) and an absorption-dominated mechanism is urgently required for fundamentally tackling EMI radiation pollution. Herein, zeolitic imidazolate framework-67 (ZIF-67)/MXene/cellulose aerogels were first prepared via a simple solution mixing-regeneration and freeze-drying process. Subsequently, they are converted into electric/magnetic hybrid carbon aerogels (Co/C/MXene/cellulose-derived carbon aerogels) through a facile pyrolysis strategy.

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Developing high-efficiency electromagnetic interference (EMI) shielding composite films with outstanding flexibility and excellent thermal management capability is vital but challenging for modern integrated electronic devices. Herein, a facile two-step vacuum filtration method was used to fabricate ultrathin, flexible, and multifunctional cellulose nanofiber (CNF)-based composite films with an asymmetric layered architecture. The asymmetric layered structure is composed of a low-conductivity CoFeO@MXene/CNF layer and a highly conductive silver nanowires (AgNWs)/CNF layer.

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Flexible strain sensors have attracted intense interest due to their application as intelligent wearable electronic devices. However, it is still a huge challenge to achieve a flexible sensor with simultaneous high sensitivity, excellent durability, and a wide sensing region. In this work, a crack-based strain sensor with a paired-serpentine conductive network is fabricated onto flexible film by screen printing.

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Manufacturing dielectric/magnetic composites with hierarchical structure is regard as a promising strategy for the progress of high-performance microwave absorption (MA) materials. In this paper, the nano-grass structured CoNiO magnetic shell was uniformly anchored on the yeast-derived carbon microspheres by in-situ one-pot synthesis method. Profiting from the unique nano-grass and core-shell structure, capable dielectric/magnetic loss, along with improved impedance matching, the prepared absorber realizes desirable MA performance.

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The development of electromagnetic interference (EMI) shielding materials with excellent absorption coefficient (A) is vital to completely eliminate the pollution of the ever-increasing electromagnetic waves (EMWs). In this regard, a TiC/carbon hybrid aerogel, derived from MXene/cellulose aerogel, was successfully fabricated via freeze-drying and subsequent pyrolysis process. Profiting from the open, loose three-dimensional (3D) macro pores with sheet-like morphology and high porosity, as well as the rich heterogeneous interfaces between TiC and cellulose-derived carbon, the as-prepared hybrid carbon aerogel achieves ultra-efficient EMI shielding effectiveness of 72.

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Nowadays, developing microwave absorption materials (MAMs) with thin thickness, wide-frequency effective absorption bandwidth (EAB) and strong absorbing capacity is an urgent requirement to tackle the increasingly serious electromagnetic radiation issue. Herein, we report a novel high-performance MAMs by growing FeO nanoparticles on activated porous carbon derived from egg white via a facile carbonization and subsequent hydrothermal approach. The resultant composite features three-dimensional hierarchical porous carbon embedded with FeO nanoparticles.

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Flexible strain sensors with high performance are actively and widely investigated for wearable electronic devices. However, the conventional sensors often suffer from a lack of detection of complex multidimensional strain, which severely limits their wide applications. To overcome this critical challenge, we propose a pattern design by screen printing to construct an asymmetrical cross-conductive network in the piezoresistive strain sensor, which can enhance the response to external stimuli in different directions.

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To effectively and selectively remove toxic anionic dyes which are heavily discharged and to promote them recovery, a sustainable cellulose nanofiber/chitosan (CNF/CS) composite film was elaborately designed through a facile procedure. Based on the strong supporting effect of CNF and excellent compatibility between CNF and CS, the composite film presents low swelling and acid-proof properties, which can prevent the adsorption process from the disintegration of adsorbent. Moreover, the positive electrical property of CNF/CS film increases the discrepancy in adsorption capacities for anionic and cationic dyes.

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Conductive hydrogel-based epidermal strain sensors can generate repeatable electrical changes upon mechanical deformations for indication of the skin's physiological condition. However, this remains challenging for many conductive hydrogel sensors due to biomechanical mismatch with skin tissues and an unstable resistance variation response, resulting in non-conformable deformations with the epidermis and dermis, and consequently generating inaccurate monitoring of human movements. Herein, a conductive hydrogel that highly matches the skin is fabricated from dynamically hydrogen-bonded nanocrystallites of polydopamine-modified reduced graphene oxide (PDA-rGO) nanosheets composited with polyvinyl alcohol, namely the PDA-rGO/PVA hydrogel.

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Introducing macromolecular micelles into a biocompatible hyaluronic acid (HA) hydrogel is a promising strategy to improve its mechanical properties for biomedical applications. However, it is still unclear whether the solvent nature has an influence on the structure and property of HA gels especially when they are used for those cases containing binary solvents because reversible hydrophobic association within micelles could be weakened or even dissociated by organic solvents. In this work, we demonstrated that a binary solvent consisting of water and low-toxic dimethyl sulfoxide (DMSO), a commonly used cryoprotectant agent in biomedicine, can enhance the mechanical properties of hydrophobic-associated methacrylated hyaluronate (MeHA) gels crosslinked by diacrylated PEO99-PPO65-PEO99 (F127DA) macromolecular micelles, namely FH gels.

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The increasing amount of dye discharge is imposing more stringent requirements on dye removal than ever before. In this work, a three-dimensional network structured cationic cellulose foam (CCF) with high dye adsorption capability and highly selective adsorption of anionic dyes is prepared through grafting and chemical crosslinking. It exhibits a maximum anionic dye Eosin Y (EY) adsorption capacity of 364.

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The pressure sensor with high sensitivity and a broad pressure sensing range is highly desired for flexible electronics. Here, a high-performance pressure sensor based on a hybrid structure was facilely fabricated using the glass template method, which consists of polyurethane (PU) mesodomes embedded with gradient-distributed silver nanowire (AgNW). Such a novel hybrid architecture enables the as-prepared PU/AgNW pressure sensor to have high sensitivity as well as a wide detection range.

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To clarify the influence of various molar concentrations of vinylidene fluoride (VDF) on the piezoelectric and acoustic emission (AE) reception performances of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] sensors, we systematically investigated the crystal structures and the dielectric and ferroelectric properties of P(VDF-TrFE) films with different compositions of VDF and TrFE monomers and found that low proportion (<30 mol%) TrFE as a wedge inserted into molecular chains of P(VDF-TrFE) will not only improve the fraction of regular β -phase crystal grains but also decrease the dielectric constant ( ε ) of these copolymers, which favors the piezoelectric voltage coefficient ( g ) of this P(VDF-TrFE) film. As such, a considerable remanent electric polarization ( [Formula: see text]/cm) under 200 MV/m and a large piezoelectric coefficient ( d  ∼ -25 pC/N) are obtained in P(VDF-TrFE) 80/20-mol% films. It is worth noting that a sensor made from P(VDF-TrFE) 80/20 mol% shows an attractive AE reception property of approximately 84 dB, a high signal voltage of above 10 mV from time-domain analysis, and a large signal voltage of above 4 mV from frequency-domain analysis, which are close to standard lead zirconate titanate (PZT) sensors.

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An efficient electromagnetic interference (EMI) shielding paper with excellent water repellency and mechanical flexibility has been developed, by assembling silver nanowires (AgNWs) and hydrophobic inorganic ceramic on the cellulose paper, via a facile dip-coating preparation. Scanning electron microscope (SEM) observations confirmed that AgNWs were interconnected and densely coated on both sides of the cellulose fiber, which endows the as-prepared paper with high conductivity (33.69 S/cm in-plane direction) at a low AgNW area density of 0.

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Regenerated cellulose (RC) films exhibit poor water barrier performance, which seriously restricts its applications. To address this issue, an impermeable and hydrophobic graphene oxide modified by chemically grafting octadecylamine (GO-ODA) was utilized to enhance the water vapor barrier performance of RC nanocomposite films. Compared to the neat RC film, more than 20% decrease in the coefficient of water vapor permeability ( ) was achieved by loading only 2.

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Pluronic F127 diacrylate (F127DA) nano-micelle crosslinked methacrylated hyaluronic acid (MeHA) hydrogels (NMgels) with strong compressive properties have been demonstrated in our previous study. The current study further focuses on how the F127DA micelles and long-term swelling affect the mechanical performance of hydrogels from the view of in vitro/in vivo applications. Co-contributions of the F127DA micelles and MeHA to the compression performance are first investigated through mechanical analysis and cyclic loading/unloading tests before and after swelling.

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Flexible strain sensors have attracted a great amount of attention for promising applications in next-generation artificially intelligent devices. However, it is difficult for conventional planar strain sensors to meet the requirements of miniature size and light weight for flexible electronics. Herein, a highly sensitive and stretchable fiber strain sensor with a millimeter diameter was innovatively fabricated by the capillary tube method to integrate silver nanowires (AgNWs) in polyurethane (PU) fibers.

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In this work, we propose novel layer-structured polymer composites (PCs) for manipulating the electromagnetic (EM) wave transport, which holds unique electromagnetic interference (EMI) shielding features. The as-prepared PCs with a multilayered structure exhibits significant improvement in overall EMI shielding effectiveness (EMI SE) by adjusting the contents and distribution of electrical and magnetic loss fillers. The layer-structured PCs with low nanofiller content (5 wt % graphene nanosheets (GNSs) and 15 wt % Fe₃O₄) and a thickness of only 2 mm exhibited ultrahigh electrical conductivity and excellent EMI SE, reaching up to 2000 S/m and 45.

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