Search

Non‐precious metal‐based nitrogen‐doped carbon (M‐Nx/C) shows great potential as a substitute for precious metal Pt‐based catalysts. However, the conventional pyrolytic methods for forming M‐Nx/C active sites are prone to issues such as the lack of synergistic interactions among bimetallic atoms and the potential encasement of active sites, leading to compromised catalytic efficiency and hindered mass transfer. In this work, a highly active FeCo‐N‐C@U‐AC electrocatalyst is developed with a high density of active sites, adequate exposure of catalytic sites, and robust mass transfer capability using the chemical vapor‐phase deposition (CVD) technique. The resulting catalyst demonstrates impressive oxygen reduction reaction (ORR) catalytic performance and stability, with half‐wave potentials of 0.820 V (0.1 M HClO4) and 0.911 V (0.1 M KOH), respectively. It also exhibits significantly enhanced stability, retaining 93.25% and 98.38% of current after continuous 50 000 s of durability testing, surpassing the retention rates of Pt/C (80.31% in HClO4 and 84.96% in KOH electrolytes). Notably, when employed as a cathode catalyst in proton exchange membrane fuel cells (PEMFCs) and zinc‐air flow batteries (ZAFBs), the FeCo‐N‐C@U‐AC catalyst delivers peak power densities of 859 and 162 mW·cm−2, respectively, showcasing competitive performance comparable to benchmark Pt/C. [ABSTRACT FROM AUTHOR]

The concept of polyrotaxane comes from the rotaxane structure in the supramolecular field. It is a mechanically interlocked supramolecular assembly composed of linear polymer chains and cyclic molecules. Over recent decades, the synthesis and application of polyrotaxanes have seen remarkable growth. Particularly, cyclodextrin‐based polyrotaxanes have been extensively reported due to the low‐price raw materials, good biocompatibility, and ease of modification. Hence, it is also one of the most promising mechanically interlocking supramolecules for wide industrialization in the future. Polyrotaxanes are widely introduced into materials such as elastomers, hydrogels, and engineering polymers to improve their mechanical properties or impart functionality to the materials. In these materials, polyrotaxane acts as a slidable cross‐linker to dissipate energy through sliding or assist in dispersing stress concentration in the cross‐linked network, thereby enhancing the toughness of the materials. Further, the unique sliding‐ring effect of cyclodextrin‐based polyrotaxanes has pioneered advancements in stretchable electronics and energy storage materials. This includes their innovative use in stretchable conductive composite and binders for anodes, addressing critical challenges in these fields. In this mini‐review, our focus is to highlight the current progress and potential wider applications in the future, underlining their transformative impact across various domains of material science. [ABSTRACT FROM AUTHOR]

Wearable electronics based on conductive hydrogels (CHs) easily suffer from prolonged response times, reduced wearing comfort, shortened service lives, and impaired signal accuracy in cold environments, because conventional CHs tend to freeze at subzero temperatures and lose their flexibility, adhesion, transparency, and conductivity, which will limit their applications in extreme environments. Inspired by the way psychrotolerant creatures and superabsorbent materials interfere with the hydrogen bonding networks of water, a freeze‐resistant conductive organohydrogel (COH) is facilely fabricated. The synergy effect between charged polar terminal groups and a binary solvent system of water–ethylene glycol weakens the hydrogen bonding between water molecules and endows the COH with remarkable freezing tolerance (−78 °C). Additionally, the obtained COH is ultra‐stretchable (≈6185%), tough (9.2 MJ m−3), highly transparent (≈99%), self‐adhesive (10.2–27.8 kPa), and biocompatible. This versatile COH is assembled into a strain sensor and a well‐designed bracelet electrocardiogram sensor. Benefiting from the exceptional low‐temperature tolerance of the prepared COH, these devices exhibit fast response with delay‐free signals even at −40 °C. Overall, this work proposes a strategy to develop multifunctional COHs for supporting human health in cold environments. [ABSTRACT FROM AUTHOR]

Adhesive hydrogels have been applied in biomedical field as an alternative to surgical sutures. However, there still exist rigorous challenges in rough underwater adhesion and asymmetric adhesion of hydrogels, especially applied in wound healing and organ repair in vivo. Herein, a strategy is proposed to prepare integrated hydrogels with asymmetric underwater adhesion capability by forming the asymmetric electrical interface under an electrostatic field. The synergistic effects between catechol and amine and complex coacervation are used to improve the underwater adhesion of hydrogel. Furthermore, by applying an electrostatic field, the cations and anions in solution of monomers are separated to form asymmetric adhesion interfaces. The hydrogel exhibits obvious asymmetric underwater adhesion ability on porcine skin with a strong adhesive strength of 97 kPa on cation side and 25 kPa on the anion side. Animal experiment outcomes reveal that only one side of the asymmetric hydrogel could adhere firmly to the rat liver and the rabbit stomach, while the other side could not effectively prevent postoperative tissue adhesion. The asymmetric distribution of adhesive molecules induced by electrostatic fields will provide a new alternative for designing and adjusting asymmetric adhesives after surgery. [ABSTRACT FROM AUTHOR]

Conductive hydrogels (CHs) are regarded as one of the most promising materials for bioelectronic devices on human‐machine interfaces (HMIs). However, conventional CHs cannot conform well with complex skin surfaces, such as hairy or wrinkled skin, due to pre‐formation and insufficient adhesion; they also usually lack antibacterial abilities and require tissue‐harm and time‐consuming preparation (e.g., heating or ultraviolet irradiation), which limits their practical application on HMIs. Herein, an in situ forming CH is proposed by taking advantage of the PEDOT:PSS‐promoted self‐polymerization of zwitterionic [2‐(methacryloyloxy)ethyl]dimethyl‐(3‐sulfopropyl) (SBMA). The hydrogel is formed spontaneously after injection of the precursor solution onto the desired location without any additional treatments. The as‐prepared hydrogel possesses excellent elasticity (elastic recovery >96%), desirable adhesive strength (≈6.5 kPa), biocompatibility, and intrinsically antibacterial properties. Without apparent heat release (<5 °C) during gelation, the hydrogel can form in situ on skin. Additionally, the obtained hydrogel can establish tight contact with skin, forming highly conformal interfaces on hairy skin surfaces and irregular wounds. Finally, the in situ forming hydrogels are applied as conformal epidermal electrodes to record stable and reliable surface electromyogram signals from hairy skin (with high signal‐to‐noise ratio, SNR ≈ 32 dB) and accelerate diabetic wound healing under electrical stimulation. [ABSTRACT FROM AUTHOR]

Ionic conductive soft materials for mimicking human skin are a promising topic since they can be thought of as a possible basis for biomimetic sensing. In pursuit of devices with a long working range and low signal delay, conductive materials with low hysteresis and good stretchability are highly demanded. To overcome the challenges of highly stretchable conductive materials with good resilience, herein a chemical design is proposed where polyrotaxanes act as topological cross‐linkers to enhance the stretchability by sliding‐induced reduced stress concentration while the compatible ionic liquid is introduced as a dispersant for low hysteresis. The obtained ionogels exhibit versatile properties more than low hysteresis (residual strain = 7%) and good stretchability (550%), and also anti‐fatigue, biocompatibility, and good adhesion. The low hysteresis is attributed to lower energy dissipation from the well‐dispersed polyrotaxanes by compatible ionic liquids. The mechanism provides a new insight in fabricating highly stretchable and low‐hysteresis slide‐ring materials. Furthermore, the conductivity of the ionogels and their responses to strains and temperatures are measured. Benefiting from the good conductivity and low hysteresis, the ionogel is applied to develop a wireless communication system to realize rapid human‐machine interactions. [ABSTRACT FROM AUTHOR]

Tough and self‐healable substrates can enable stretchable electronics long service life. However, for substrates, it still remains a challenge to achieve both high toughness and autonomous self‐healing ability at room temperature. Herein, a strategy by using the combined effects between quadruple H‐bonding and slidable cross‐links is proposed to solve the above issues in the elastomer. The elastomer exhibits high toughness (77.3 MJ m−3), fracture energy (≈127.2 kJ m−2), and good healing efficiency (91 %) at room temperature. The superior performance is ascribed to the inter and intra crosslinking structures of quadruple H‐bonding and polyrotaxanes in the dual crosslinking system. Strain‐induced crystallization of PEG in polyrotaxanes also contributes to the high fracture energy of the elastomers. Furthermore, based on the dual cross‐linked supramolecular elastomer, a highly stretchable and self‐healable electrode containing liquid metal is also fabricated, retaining resistance stability (0.16–0.26 Ω) even at the strain of 1600 %. [ABSTRACT FROM AUTHOR]

Silicon is expected to become the ideal anode material for the next generation of high energy density lithium battery because of its high theoretical capacity (4200 mAh g−1). However, for silicon electrodes, the initial coulombic efficiency (ICE) is low and the volume of the electrode changes by over 300% after lithiation. The capacity of the silicon electrode decreases rapidly during cycling, hindering the practical application. In this work, a slidable and highly ionic conductive flexible polymer binder with a specific single‐ion structure (abbreviated as SSIP) is presented in which polyrotaxane acts as a dynamic crosslinker. The ionic conducting network is expected to reduce the overall resistance, improve ICE and stabilize the electrode interface. Furthermore, the introduction of slidable polyrotaxane increases the reversible dynamics of the binder and improves the long‐term cycling stability and rate performance. The silicon anode based on SSIP provides a discharge capacity of ≈1650 mAh g−1 after 400 cycles at 0.5C with a high ICE of upto 92.0%. Additionally, the electrode still exhibits a high ICE of 87.5% with an ultra‐high Si loading of 3.84 mg cm−2 and maintains a satisfying areal capacity of 5.9 mAh cm−2 after 50 cycles, exhibiting the potential application of SSIP in silicon‐based anodes. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the accuracy of pulmonary nodule (PN) detection in overweight or obese adult patients using ultralow‐dose computed tomography (ULDCT) with tin filtration at 100 kV and advanced model‐based iterative reconstruction (ADMIRE). Methods: Eighty‐one patients with body mass indices of ≥25 kg/m2 were enrolled. All patients underwent low‐dose chest CT (LDCT), followed by ULDCT. Two radiologists experienced in LDCT established the standard of reference (SOR) for PNs. The number, type, size, and location of PNs were identified in the SOR. Effective dose, objective image quality (IQ), and subjective IQ based on two radiologists' scores were compared between ULDCT and LDCT. The detection performances of radiologists based on ULDCT were calculated according to the nodule analyses. Logistic regression was used to test for independent predictors of PN detection sensitivity. Results: Both the effective dose and objective IQ were lower for ULDCT than for LDCT (both p < 0.001). Both radiologists rated the subjective IQ of the overall IQ on ULDCT to be diagnostically sufficient. In total, 234 nodules (mean diameter, 3.4 ± 1.9 mm) were classified into 32 subsolid, 149 solid, and 53 calcified nodules according to the SOR. The overall sensitivity of ULDCT for nodule detection was 93.6%. Based on multivariate analyses, the nodule types (p = 0.015) and sizes (p = 0.013) were independent predictors of nodule detection. Conclusions: Compared with LDCT, ULDCT with tin filtration at 100 kV and ADMIRE could significantly reduce the radiation dose in overweight or obese patients while maintaining good sensitivity for nodule detection. [ABSTRACT FROM AUTHOR]

Lithium‐ion batteries play a significant role in modern electronics and electric vehicles. However, current Li‐ion battery chemistries are unable to satisfy the increasingly heightened expectations regarding energy demand and reliability. To boost the overall energy density while ensuring the safety of Li batteries, researchers have focused on alternative battery materials, such as silicon, sulfur, and Li metal. These represent promising avenues, although numerous obstacles (e.g., Si cracking, polysulfide shuttling, Li dendrites, etc.) must be tackled before batteries based on these materials can enter mass production and penetrate the mainstream market. Polymers are a class of materials that are widely used in current battery systems; however, many novel polymer chemistries may offer better performance and reliability than the current ones, and even overcome the issues of the above‐mentioned new battery materials. In this review, selected polymeric materials for solving these issues are categorized into four parts: polymer electrolytes, polymer artificial solid‐electrolyte interphases, binders, and separators. Both the current progress and the characterization methods are included. Potential future directions of energy materials research are pointed out as well. [ABSTRACT FROM AUTHOR]

Stretchable electrodes are playing important roles in the measurement of bio‐electrical signals especially in wearable electronic devices. These electrodes usually adopt commercial elastomers such as polydimethylsiloxane or polystyrene‐ethylene‐butylene‐styrene as substrates, which result in poor stability and reliability due to weak interfacial adhesion between electrodes and human skin. Here, dopamine is introduced into the hydrogen bonding based elastomer as pendent groups. The elastomer shows both mechanical strength and adhesion strength at the same time. It exhibits high stress at break (1.9 MPa) and high fracture strain (5100%). Significantly, it exhibits a high adhesive strength (≈62 kPa) and underwater adhesive strength (≈16 kPa) with epithelial tissue. Thus, a stretchable bio‐interfacial electrode is fabricated by spray‐coating silver nanowires on the elastic substrate, which is stretchable, self‐healable, and highly adhesive and suitable for electromyogram measurement. [ABSTRACT FROM AUTHOR]

Abstract: Spiropyran (SP) shows excellent ability in light‐ or force‐triggered color and fluorescence generation. However, it has the fatal weakness of poor antithermal bleaching properties in polymers, especially when exposed to severe environments, which will shorten the life of mechanical responsive materials. Here, a strategy is reported to protect SP through incorporation of multifunctional polyhedral oligomeric silsesquioxanes (POSS) as cross‐linkers into a polyurethane network. The introduction of POSS not only improves the mechanical strength of the elastomer, but also enhances the thermal stability of the mechanophore, showing much more sensitive force‐responsive and photoresponsive properties, especially after thermal annealing. POSS contributes to the construction of a 3D network and hinders the mobility of the hard domains of molecular chains, thus enhancing the thermal stability of the mechanophore in the network. The strategy can not only extend the life of the stimuli‐responsive materials, but also promote the application temperature of the mechanically responsive polymers. [ABSTRACT FROM AUTHOR]

A series of new donor-acceptor (D-A)-type semiconducting conjugated polymers (SCPs), which can form cross-linked structural and supramolecular assembly films by hydrogen-bonding, is successfully synthesized. The microstructures of supramolecular assembly films are further investigated by X-ray diffraction (XRD), high- resolution transmission electron microscopy (HRTEM), and variable-temperature Fourier transform infrared (FT-IR) absorption spectra. As electronic transmission (ET) materials, the SCPs demonstrate superior properties by means of fabricating electron-only devices with the configuration of ITO/ET (SCPs)/Ca/Al. According to space-charge-limited current (SCLC) measurements, fluorine-containing SCPs exhibit much smaller threshold voltages and much higher electron mobilities than Alq3. Meanwhile, a significant enhancement for their luminescence properties is verified by the photoluminescence (PL) and electroluminescent (EL) spectra of cross-linked-type SCPs, compared to non-cross-linked-type SCPs. The fabricated polymer light-emitting diodes (PLEDs) with the configuration of ITO/PEDOT:PSS/EML (SCPs)/BCP/LiF/Al are able to emit the color from green to red with moderately low turn-on voltages. These results suggested that cross-linked D-A-type SCP can become a potential candidate as a kind of multifunctional materials applied in the field of optoelectronic devices. [ABSTRACT FROM AUTHOR]

ABSTRACT Novel polybenzoxazine precursor containing m-carborane unit in the main-chain has been firstly synthesized through click reaction of diazidomethyl m-carborane (DAMC) and diacetylene bisbenzoxazine (DABB). Meanwhlie, the traditional polybenzoxazine precursor was also prepared through click reaction of diazidomethyl p-benzene (DAPB) and DABB as a control. 1H NMR was used to confirm the structures of the monomers and the resulting polymers. FT-IR and differential scanning calorimetry (DSC) were used to study the curing behavior of carborane-containing benzoxazine polymer (CCBP). Dynamic mechanical analysis (DMA) study demonstrated that the cured CCBP had high storage moduli and high Tg. Thermogravimetric analysis (TGA) and ablation test showed that the cured CCBP had outstanding thermo-oxidative stability. During thermal ablation of cured CCBP, organic material was degraded, and a passivation layer with oxidized m-carboranes was formed, which prevented the underlying polymer from further degradation. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 973-980 [ABSTRACT FROM AUTHOR]

Previous human intervention trial demonstrated that vitamin E (Ve) and selenium (Se) supplementation decreased esophageal cancer deaths among younger participants, but may have no effect or produce an opposite effect among older ones. In our study, we intended to mimic this human nutritional trial to determine the chemopreventive effects of Ve/Se supplementation at the early or late stage of esophageal carcinogenesis in rats. Esophageal squamous cell carcinoma (ESCC) was induced in Fischer 344 rats with N-nitrosomethylbenzylamine (NMBzA, 0.35 mg/kg BW, s.c., three times per week for 5 weeks). The rats were maintained on a modified AIN-93M diet with low levels of Ve/Se or supplemented with high levels of Ve/Se at different stages. At Week 25, the number and volume of visible tumors, the numbers of dysplasia and ESCC were significantly lower in rats of supplementation during the early stage (Group C) or during the entire experimental period (Group E), but not during the late stage (Group D). Ve/Se supplementation at the early stage also significantly decreased cell proliferation, nuclear factor kappaB (NFκB) activation, protein and mRNA expression of cyclooxygenase 2 and 5-lipoxygenase and biosynthesis of prostaglandin E2 and leukotriene B4 during the carcinogenesis of rat esophagus. Our results demonstrated that the chemopreventive efficacy of Ve/Se supplementation on NMBzA-induced esophageal cancer is time selective and that supplementation during the early stage is clearly effective but probably ineffective during the late stage of carcinogenesis. NFκB signaling pathway activation and aberrant arachidonic acid metabolism might be the underlying mechanism. [ABSTRACT FROM AUTHOR]

The article presents a study which assessed the moisture-resistance and low-dielectric-constant applications of polyimide-polydimethylsiloxane (PI-PDMS) copolymers. The researchers examined the effects if the dielectric constant of the copolymers was reduced and if PDMS is incorporated into the polyimide chain. They found that the water contact angles of the copolymers have enhanced to 109 degrees from 51 degrees.

The article presents a study which synthesized novel blood-compatible waterborne polyurethane (PU) materials by copolymerization using water soluble chitosan (CS) as an extender. It discusses the steps of preparing a series of novel block polymers of PU and CS. Dynamic light scattering (DLS), general tensile heat, infrared spectroscopy (IR), transmission electron microscopy (TEM), and surface contact angle measurement characterized the latex particles, morphology, and copolymer architecture.

The long application life and stable performance of stretchable electronics have been putting forward requirements for both higher mechanical properties and better self‐healing ability of polymeric substrates. However, for self‐healing materials, simultaneously improving stretchability and robustness is still challenging. Here, by incorporating sliding crosslinker (polyrotaxanes) and hydrogen bonds into a polymer, a highly stretchable and self‐healable elastomer with good mechanical strength is achieved. The elastomer exhibits very high stretchability, such that it can be stretched to 2800% with a fracture strength of 1.05 MPa. Moreover, the elastomer can achieve nearly complete self‐healing (93%) at 55 °C. Next, tensile tests under different temperatures, step extension experiments, and in situ small angle X‐ray scattering confirm that the excellent stretchability is attributed to the combined effects of sliding cyclodextrins along guest chains and hydrogen bonds. Furthermore, a strain sensor by coating the single‐wall carbon nanotubes onto the surface of the elastic substrate is fabricated. [ABSTRACT FROM AUTHOR]

A new kind of donor–acceptor‐type semiconducting conjugated polymers with hydrogen bonding cross‐linked structure is successfully synthesized by X. Zhang, X. Jia, and co‐workers on page 1646. This polymer has potential for applications in flat‐panel displays, with firework‐like illumination from their excellent electronic transmission, photoluminescence, and electroluminescent properties. [ABSTRACT FROM AUTHOR]

trans-Resveratrol (resveratrol) has been shown to have beneficial effects on the cardiovascular system in a number of studies. It is, however, unclear whether this naturally occurring compound can protect against cardiac hypertrophy. The aim of the present study was to investigate the effects of resveratrol on cardiac hypertrophy in vivo and the potential underlying mechanisms involving endothelin (ET), angiotensin (Ang) II and nitric oxide (NO) in partially nephrectomized rats. Animal models bearing cardiac hypertrophy were replicated in male Sprague-Dawley rats following partial nephrectomy (PNX). Resveratrol (10 or 50 mg/kg) was administered to rats by gavage for 4 weeks. Simultaneous PNX and sham operation controls were simultaneously established in the present study. The systolic blood pressure (SBP) of rats was measured at baseline and, along with heart weight, after 4 weeks treatment. Serum ET-1, AngII and NO concentrations were determined. In the present study, it was shown that, compared with rats in the sham-operated group, rats in the PNX group had significantly higher SBP (154.1 +/- 22.7 mmHg), heart weight (1.69 +/- 0.24 g) and serum ET-1 (125.70 +/- 26.27 pg/mL) and AngII serum concentrations (743.63 +/- 86.50 pg/mL), whereas serum NO concentrations were lower (21.1 +/- 6.9 micromol/L; all P < 0.05). These values in the sham control group were 114 +/- 10 mmHg, 1.28 +/- 0.13 g, 52.44 +/- 21.85 pg/mL, 528.7 +/- 158.5 pg/mL and 53.21 +/- 23.87 micromol/L, respectively. After 4 weeks treatment with 50 mg/kg resveratrol, SBP, heart weight and ET-1 and AngII concentrations had decreased to 135.4 +/- 15.8 mmHg, 1.39 +/- 0.15 g, 97.11 +/- 26.74 pg/mL and 629.64 +/- 116.18 pg/mL, respectively. However, the serum NO concentration had increased to 40.1 +/- 14.6 micromol/L. These values were significantly different from those obtained for the PNX group. In conclusion, trans-resveratrol appears to be able to protect against the increase in SBP and subsequent cardiac hypertrophy in vivo and the mechanisms responsible may involve, at least in part, modulation of NO, AngII and ET-1 production.