Showing papers in "ACS Applied Materials & Interfaces in 2016"
TL;DR: Considering the promising performance of Ti3C2 MXenes with the modified surface, this work is expected to open the door for the expanded applications of MXenes family in EM absorbing and shielding fields.
Abstract: Electromagnetic (EM) absorbing and shielding composites with tunable absorbing behaviors based on Ti3C2 MXenes are fabricated via HF etching and annealing treatment. Localized sandwich structure without sacrificing the original layered morphology is realized, which is responsible for the enhancement of EM absorbing capability in the X-band. The composite with 50 wt % annealed MXenes exhibits a minimum reflection loss of −48.4 dB at 11.6 GHz, because of the formation of TiO2 nanocrystals and amorphous carbon. Moreover, superior shielding effectiveness with high absorption effectiveness is achieved. The total and absorbing shielding effectiveness of Ti3C2 MXenes in a wax matrix with a thickness of only 1 mm reach values of 76.1 and 67.3 dB, while those of annealed Ti3C2 MXenes/wax composites are 32 and 24.2 dB, respectively. Considering the promising performance of Ti3C2 MXenes with the modified surface, this work is expected to open the door for the expanded applications of MXenes family in EM absorbing an...
691 citations
TL;DR: The improved charge separation and exposed active facets dramatically boost the photocatalytic degradation of methyl orange dye, showing the promise of 2D transition metal carbide for fabricating functional catalytic materials.
Abstract: Effectively harvesting light to generate long-lived charge carriers to suppress the recombination of electrons and holes is crucial for photocatalytic reactions. Exposing the highly active facets has been regarded as a powerful approach to high-performance photocatalysts. Herein, a hybrid comprised of {001} facets of TiO2 nanosheets and layered Ti3C2, an emerging 2D material, was synthesized by a facile hydrothermal partial oxidation of Ti3C2. The in situ growth of TiO2 nanosheets on Ti3C2 allows for the interface with minimized defects, which was demonstrated by high-resolution transmission electron microscopy and density functional theory calculations. The highly active {001} facets of TiO2 afford high-efficiency photogeneration of electron–hole pairs, meanwhile the carrier separation is substantially promoted by the hole trapping effect by the interfacial Schottky junction with 2D Ti3C2 acting as a reservoir of holes. The improved charge separation and exposed active facets dramatically boost the photo...
572 citations
TL;DR: Li et al. as discussed by the authors showed that the short circuit formation was not due to the low relative density of the samples nor the reduction of Li-Al glassy phase at grain boundaries, but was caused by Li dendrite formation inside HP-LLZ:Ta, which took place along the grain boundaries.
Abstract: Al-contaminated Ta-substituted Li7La3Zr2O12 (LLZ:Ta), synthesized via solid-state reaction, and Al-free Ta-substituted Li7La3Zr2O12, fabricated by hot-press sintering (HP-LLZ:Ta), have relative densities of 92.7% and 99.0%, respectively. Impedance spectra show the total conductivity of LLZ:Ta to be 0.71 mS cm–1 at 30 °C and that of HP-LLZ:Ta to be 1.18 mS cm–1. The lower total conductivity for LLZ:Ta than HP-LLZ:Ta was attributed to the higher grain boundary resistance and lower relative density of LLZ:Ta, as confirmed by their microstructures. Constant direct current measurements of HP-LLZ:Ta with a current density of 0.5 mA cm–2 suggest that the short circuit formation was neither due to the low relative density of the samples nor the reduction of Li–Al glassy phase at grain boundaries. TEM, EELS, and MAS NMR were used to prove that the short circuit was from Li dendrite formation inside HP-LLZ:Ta, which took place along the grain boundaries. The Li dendrite formation was found to be mostly due to the i...
557 citations
TL;DR: The results show that the as-synthesized composites exhibit more highly efficient photocatalytic activity than pure g-C3N4 and BiOI and that the product yields change remarkably depending on the reaction conditions such as irradiation light wavelength.
Abstract: Rational design and construction of Z-scheme photocatalysts has received much attention in the field of CO2 reduction because of its great potential to solve the current energy and environmental crises. In this study, a series of Z-scheme BiOI/g-C3N4 photocatalysts are synthesized and their photocatalytic performance for CO2 reduction to produce CO, H2 and/or CH4 is evaluated under visible light irradiation (λ > 400 nm). The results show that the as-synthesized composites exhibit more highly efficient photocatalytic activity than pure g-C3N4 and BiOI and that the product yields change remarkably depending on the reaction conditions such as irradiation light wavelength. Emphasis is placed on identifying how the charge transfers across the heterojunctions and an indirect Z-scheme charge transfer mechanism is verified by detecting the intermediate I3(-) ions. The reaction mechanism is further proposed based on the detection of the intermediate (•)OH and H2O2. This work may be useful for rationally designing of new types of Z-scheme photocatalyst and provide some illuminating insights into the Z-scheme transfer mechanism.
524 citations
TL;DR: In this study, yolk-shell Ni@void@SnO2 composites with a designable interspace with outstanding electromagnetic wave absorption properties were successfully prepared by the simple acid etching hydrothermal method.
Abstract: In this study, yolk–shell Ni@SnO2 composites with a designable interspace were successfully prepared by the simple acid etching hydrothermal method. The Ni@void@SnO2 composites were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results indicate that interspaces exist between the Ni cores and SnO2 shells. Moreover, the void can be adjusted by controlling the hydrothermal reaction time. The unique yolk–shell Ni@void@SnO2 composites show outstanding electromagnetic wave absorption properties. A minimum reflection loss (RLmin) of −50.2 dB was obtained at 17.4 GHz with absorber thickness of 1.5 mm. In addition, considering the absorber thickness, minimal reflection loss, and effective bandwidth, a novel method to judge the effective microwave absorption properties is proposed. On the basis of this method, the best microwave absorption properties were obtained with a 1.7 mm th...
522 citations
TL;DR: A facile synthesis method of nanoscale Fe3O4/graphene capsules (GCs) composites using the combination of catalytic chemical vapor deposition (CCVD) and hydrothermal process offers an effective way to design high-performance functional materials to facilitate the research in electromagnetic shielding and microwave absorption.
Abstract: Graphene has good stability and adjustable dielectric properties along with tunable morphologies, and hence can be used to design novel and high-performance functional materials. Here, we have reported a facile synthesis method of nanoscale Fe3O4/graphene capsules (GCs) composites using the combination of catalytic chemical vapor deposition (CCVD) and hydrothermal process. The resulting composite has the advantage of unique morphology that offers better synergism among the Fe3O4 particles as well as particles and GCs. The microwave-absorbing characteristics of developed composites were investigated through experimentally measured electromagnetic properties and simulation studies based on the transmission line theory, explained on the basis of eddy current, natural and exchange resonance, as well as dielectric relaxation processes. The composites bear minimum RL value of −32 dB at 8.76 GHz along with the absorption bandwidth range from 5.4 to 17 GHz for RL lower than −10 dB. The better performance of the c...
489 citations
TL;DR: Findings indicate that ring-like and core-shell nanostructures are promising structures for devising new and effective microwave absorbers.
Abstract: Using elliptical iron glycolate nanosheets as precursors, elliptical Fe3O4/C core-shell nanorings (NRs) [25 ± 10 nm in wall thickness, 150 ± 40 nm in length, and 1.6 ± 0.3 in long/short axis ratio] are synthesized via a one-pot hydrothermal route. The surface-poly(vinylpyrrolidone) (PVP)-protected-glucose reduction/carbonization/Ostwald ripening mechanism is responsible for Fe3O4/C NR formation. Increasing the glucose/precursor molar ratio can enhance carbon contents, causing a linear decrease in saturation magnetization (Ms) and coercivity (Hc). The Fe3O4/C NRs reveal enhanced low-frequency microwave absorption because of improvements to their permittivity and impedance matching. A maximum RL value of -55.68 dB at 3.44 GHz is achieved by Fe3O4/C NRs with 11.95 wt % C content at a volume fraction of 17 vol %. Reflection loss (RL) values (≤-20 dB) are observed at 2.11-10.99 and 16.5-17.26 GHz. Our research provides insights into the microwave absorption mechanism of elliptical Fe3O4/C core-shell NRs. Findings indicate that ring-like and core-shell nanostructures are promising structures for devising new and effective microwave absorbers.
489 citations
TL;DR: The as-prepared CoP hollow polyhedron, which have large specific surface area and high porosity providing rich catalytic active sites, show excellent electrocatalytic performances for both HER and OER in acidic and alkaline media, which are remarkably superior to those of particulate CoP (CoP particles) and comparable toThose of commercial noble-metal catalysts.
Abstract: The development of efficient and low-cost hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) electrocatalysts for renewable-energy conversion techniques is highly desired. A kind of hollow polyhedral cobalt phosphide (CoP hollow polyhedron) is developed as efficient bifunctional electrocatalysts for HER and OER templated by Co-centered metal–organic frameworks. The as-prepared CoP hollow polyhedron, which have large specific surface area and high porosity providing rich catalytic active sites, show excellent electrocatalytic performances for both HER and OER in acidic and alkaline media, respectively, with onset overpotentials of 35 and 300 mV, Tafel slopes of 59 and 57 mV dec–1, and a current density of 10 mA cm–2 at overpotentials of 159 and 400 mV for HER and OER, respectively, which are remarkably superior to those of particulate CoP (CoP particles) and comparable to those of commercial noble-metal catalysts. In addition, the CoP hollow polyhedron also show good durability after lon...
441 citations
TL;DR: The results indicate that the hybrid nanocomposites with enhanced microwave absorption properties and lightweight have a promising future in decreasing electromagnetic wave irradiation.
Abstract: Hybrid nanocomposites with enhanced microwave absorption properties have been designed by growing CuS nanoflakes on magnetically decorated graphene, and the effect of special nanostructures on microwave absorption properties has been investigated. The structure of the nanocomposites was characterized by Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), N2 adsorption–desorption, and vibrating sample magnetometer (VSM). The influence of cetyltrimethylammonium bromide (CTAB) on the morphology of CuS nanoflakes was also investigated. A possible formation process of the nanocomposites and the mechanism of microwave absorption were explained in detail. As an absorber, the nanocomposites with a filler loading of 20 wt % exhibited enhanced microwave absorption properties due to the special nanostructures, extra void space, and synergistic effect...
423 citations
TL;DR: These self-healable conductive biodegradable injectable hydrogels based on chitosan-graft-aniline tetramer and dibenzaldehyde-terminated poly(ethylene glycol) (PEG-DA) are excellent candidates as cell delivery vehicle for cardiac repair.
Abstract: Cell therapy is a promising strategy to regenerate cardiac tissue for myocardial infarction. Injectable hydrogels with conductivity and self-healing ability are highly desirable as cell delivery vehicles for cardiac regeneration. Here, we developed self-healable conductive injectable hydrogels based on chitosan-graft-aniline tetramer (CS-AT) and dibenzaldehyde-terminated poly(ethylene glycol) (PEG-DA) as cell delivery vehicles for myocardial infarction. Self-healed electroactive hydrogels were obtained after mixing CS-AT and PEG-DA solutions at physiological conditions. Rapid self-healing behavior was investigated by rheometer. Swelling behavior, morphology, mechanical strength, electrochemistry, conductivity, adhesiveness to host tissue and antibacterial property of the injectable hydrogels were fully studied. Conductivity of the hydrogels is ∼10–3 S·cm–1, which is quite close to native cardiac tissue. Proliferation of C2C12 myoblasts in the hydrogel showed its good biocompatibility. After injection, via...
423 citations
TL;DR: A feasible approach to modify the tribo-material of TENG by filling it with high permittivity nanoparticles and forming pores is designed, which gives a better understanding of the triboelectricity produced by the TENG from the view of materials and provides a new and effective way to enhance the performance of T ENG from the material itself, not just its surface modification.
Abstract: Understanding of the triboelectric charge accumulation from the view of materials plays a critical role in enhancing the output performance of triboelectric nanogenerator (TENG). In this paper, we have designed a feasible approach to modify the tribo-material of TENG by filling it with high permittivity nanoparticles and forming pores. The influence of dielectricity and porosity on the output performance is discussed experimentally and theoretically, which indicates that both the surface charge density and the charge transfer quantity have a close relationship with the relative permittivity and porosity of the tribo-material. A high output performance TENG based on a composite sponge PDMS film (CS-TENG) is fabricated by optimizing both the dielectric properties and the porosity of the tribo-material. With the combination of the enhancement of permittivity and production of pores in the PDMS film, the charge density of ∼19 nC cm(-2), open-circuit voltage of 338 V, and power density of 6.47 W m(-2) are obtained at working frequency of 2.5 Hz with the optimized film consisting of 10% SrTiO3 nanoparticles (∼100 nm in size) and 15% pores in volume, which gives over 5-fold power enhancement compared with the nanogenerator based on the pure PDMS film. This work gives a better understanding of the triboelectricity produced by the TENG from the view of materials and provides a new and effective way to enhance the performance of TENG from the material itself, not just its surface modification.
TL;DR: It is believed that the strategy for fabricating PGC foams through a simple dip-coating method could potentially promote the large-scale production of lightweight foam materials for EMI shielding.
Abstract: The fabrication of low-density and compressible polymer/graphene composite (PGC) foams for adjustable electromagnetic interference (EMI) shielding remains a daunting challenge. Herein, ultralightweight and compressible PGC foams have been developed by simple solution dip-coating of graphene on commercial polyurethane (PU) sponges with highly porous network structure. The resultant PU/graphene (PUG) foams had a density as low as ∼0.027–0.030 g/cm3 and possessed good comprehensive EMI shielding performance together with an absorption-dominant mechanism, possibly due to both conductive dissipation and multiple reflections and scattering of EM waves by the inside 3D conductive graphene network. Moreover, by taking advantage of their remarkable compressibility, the shielding performance of the PUG foams could be simply adjusted through a simple mechanical compression, showing promise for adjustable EMI shielding. We believe that the strategy for fabricating PGC foams through a simple dip-coating method could p...
TL;DR: The excellent absorbing performance together with lightweight and ultrathin thickness endows the CNTs/Co composite with the potential for application in the electromagnetic wave absorbing field.
Abstract: Porous carbon nanotubes/cobalt nanoparticles (CNTs/Co) composite with dodecahedron morphology was synthesized by in situ pyrolysis of the Co-based zeolitic imidazolate framework in a reducing atmosphere. The morphology and microstructure of the composite can be well tuned by controlling the pyrolysis conditions. At lower pyrolysis temperature, the CNTs/Co composite is composed of well-dispersed Co nanoparticles and short CNT clusters with low graphitic degree. The increase of pyrolysis temperature/time promotes the growth and graphitization of CNTs and leads to the aggregation of Co nanoparticles. The optimized CNTs/Co composite exhibits strong dielectric and magnetic losses as well as a good impedance matching property. Interestingly, the CNTs/Co composite displays extremely strong electromagnetic wave absorption with a maximum reflection loss of −60.4 dB. More importantly, the matching thickness of the absorber is as thin as 1.81 mm, and the filler loading of composite in the matrix is only 20 wt %. The...
TL;DR: The fabrication of novel carboxylated agarose/tannic acid hydrogel scaffolds cross-linked with zinc ions for the pH-controlled release of tannic acids display cytocompatibility, antibacterial, and anti-inflammatory characteristics that make them promising candidates for wound dressings.
Abstract: pH-sensitive hydrogels play an important role in controlled drug release applications and have the potential to impact the management of wounds. In this study, we report the fabrication of novel carboxylated agarose/tannic acid hydrogel scaffolds cross-linked with zinc ions for the pH-controlled release of tannic acid. The resulting hydrogels exhibited negligible release of tannic acid at neutral and alkaline pH and sustained release at acidic pH, where they also displayed maximum swelling. The hydrogels also displayed favorable antibacterial and anti-inflammatory properties, and a lack of cytotoxicity toward 3T3 fibroblast cell lines. In simulated wound assays, significantly greater cell migration and proliferation was observed for cells exposed to tannic acid hydrogel extracts. In addition, the tannic acid hydrogels were able to suppress NO production in stimulated human macrophages in a concentration-dependent manner, indicating effective anti-inflammatory activity. Taken together, the cytocompatibilit...
TL;DR: The hollow Fe3O4-Fe nanoparticles with average diameter and shell thickness of 20 and 8 nm, respectively, were uniformly anchored on the graphene sheets without obvious aggregation and the minimal reflection loss RL values of the composite could reach -30 dB at the absorber thickness ranging from 2.0 to 5.0 mm.
Abstract: We developed a strategy for coupling hollow Fe3O4–Fe nanoparticles with graphene sheets for high-performance electromagnetic wave absorbing material. The hollow Fe3O4–Fe nanoparticles with average diameter and shell thickness of 20 and 8 nm, respectively, were uniformly anchored on the graphene sheets without obvious aggregation. The minimal reflection loss RL values of the composite could reach −30 dB at the absorber thickness ranging from 2.0 to 5.0 mm, greatly superior to the solid Fe3O4–Fe/G composite and most magnetic EM wave absorbing materials recently reported. Moreover, the addition amount of the composite into paraffin matrix was only 18 wt %.
TL;DR: AMoS2/CdS nanohybrid as a noble-metal-free efficient visible-light driven photocatalyst, which has the unique nanosheets-on-nanorod heterostructure with partially crystalline MoS2 nanOSheets intimately but discretely growing on single-crystalline CdS Nanorod, will open opportunities for developing low-cost efficient photocatalysts for water splitting.
Abstract: Semiconductor-based photocatalytic H2 generation as a direct approach of converting solar energy to fuel is attractive for tackling the global energy and environmental issues but still suffers from low efficiency. Here, we report a MoS2/CdS nanohybrid as a noble-metal-free efficient visible-light driven photocatalyst, which has the unique nanosheets-on-nanorod heterostructure with partially crystalline MoS2 nanosheets intimately but discretely growing on single-crystalline CdS nanorod. This heterostructure not only facilitates the charge separation and transfer owing to the formed heterojunction, shorter radial transfer path, and fewer defects in single-crystalline nanorod, thus effectively reducing the charge recombination, but also provides plenty of active sites for hydrogen evolution reaction due to partially crystalline structure of MoS2 as well as enough room for hole extraction. As a result, the MoS2/CdS nanosheets-on-nanorod exhibits a state-of-the-art H2 evolution rate of 49.80 mmol g–1 h–1 and a...
TL;DR: A novel heterostructured photocatalyst AgI/BiVO4 was synthesized by an in situ precipitation procedure that exhibited excellent photoactivity for the refractory pollutant (tetracycline) decomposition under visible light illumination and efficiently accelerated photoinduced electron-hole pairs' separation and improved the efficiency of TC degradation.
Abstract: Recently, visible-light-driven photocatalysis is of great interest in the environmental pollutant remediation. In the present study, a novel heterostructured photocatalyst AgI/BiVO4 was synthesized by an in situ precipitation procedure. The AgI/BiVO4 heterojunctions exhibited excellent photoactivity for the refractory pollutant (tetracycline (TC), a typical antibiotic) decomposition under visible light illumination. The synthetic sample with 1:4 mass ratio of AgI:BiVO4 possessed the highest photocatalytic performance in all of the as-prepared catalysts. The TC molecules were substantially eliminated (94.91%) within 60 min, and degradation efficiency was considerably better than those of bare BiVO4 (62.68%) and AgI (75.43%) under identical conditions. Simultaneously, 90.46% of TOC removal was also achieved within 120 min, suggesting that the mineralization was superior and further confirmed by three-dimensional excitation–emission matrix fluorescence spectroscopy (3D EEMs). The XRD, XPS, DRS, and PL measur...
TL;DR: The synthesized MoS2/SnO2 hybrid composite was proved to be an excellent candidate for constructing ultrahigh-performance humidity sensor toward various applications and the sensor response yielded in this work was tens of times higher than that of the existing humidity sensors.
Abstract: An ultrasensitive humidity sensor based on molybdenum-disulfide- (MoS2)-modified tin oxide (SnO2) nanocomposite has been demonstrated in this work. The nanostructural, morphological, and compositional properties of an as-prepared MoS2/SnO2 nanocomposite were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive spectrometry (EDS), nitrogen sorption analysis, and Raman spectroscopy, which confirmed its successful preparation and rationality. The sensing characteristics of the MoS2/SnO2 hybrid film device against relative humidity (RH) were investigated at room temperature. The RH sensing results revealed an unprecedented response, ultrafast response/recovery behaviors, and outstanding repeatability. To our knowledge, the sensor response yielded in this work was tens of times higher than that of the existing humidity sensors. Moreover, the MoS2/SnO2 hybrid nanocomposite film sensor exhibited great enhancement in humidity sensi...
TL;DR: The synthesis of CoSe2 and NiSe2 nanocrystals (NCs) are reported as excellent bifunctional catalysts for simultaneous generation of H2 and O2 in water-splitting reactions and strong evidence for surface oxidation suggests that the surface oxide layers are the actual active sites for OER.
Abstract: Catalysts for oxygen evolution reactions (OER) and hydrogen evolution reactions (HER) are central to key renewable energy technologies, including fuel cells and water splitting. Despite tremendous effort, the development of low-cost electrode catalysts with high activity remains a great challenge. In this study, we report the synthesis of CoSe2 and NiSe2 nanocrystals (NCs) as excellent bifunctional catalysts for simultaneous generation of H2 and O2 in water-splitting reactions. NiSe2 NCs exhibit superior electrocatalytic efficiency in OER, with a Tafel slope (b) of 38 mV dec(-1) (in 1 M KOH), and HER, with b = 44 mV dec(-1) (in 0.5 M H2SO4). In comparison, CoSe2 NCs are less efficient for OER (b = 50 mV dec(-1)), but more efficient for HER (b = 40 mV dec(-1)). It was found that CoSe2 NCs contained more metallic metal ions than NiSe2, which could be responsible for their improved performance in HER. Robust evidence for surface oxidation suggests that the surface oxide layers are the actual active sites for OER, and that CoSe2 (or NiSe2) under the surface act as good conductive layers. The higher catalytic activity of NiSe2 is attributed to their oxide layers being more active than those of CoSe2. Furthermore, we fabricated a Si-based photoanode by depositing NiSe2 NCs onto an n-type Si nanowire array, which showed efficient photoelectrochemical water oxidation with a low onset potential (0.7 V versus reversible hydrogen electrode) and high durability. The remarkable catalytic activity, low cost, and scalability of NiSe2 make it a promising candidate for practical water-splitting solar cells.
TL;DR: The results demonstrate that the NiCo2S4@PPy-50 core-shell heterostructure nanotube array is promising as electrode material for supercapacitors in energy storage.
Abstract: In this paper, a hierarchical NiCo2S4@polypyrrole core–shell heterostructure nanotube array on Ni foam (NiCo2S4@PPy/NF) was successfully developed as a bind-free electrode for supercapacitors. NiCo2S4@PPy-50/NF obtained under 50 s PPy electrodeposition shows a low charge-transfer resistance (0.31 Ω) and a high area specific capacitance of 9.781 F/cm2 at a current density of 5 mA/cm2, which is two times higher than that of pristine NiCo2S4/NF (4.255 F/cm2). Furthermore, an asymmetric supercapacitor was assembled using NiCo2S4@PPy-50/NF as positive electrode and activated carbon (AC) as negative electrode. The resulting NiCo2S4@PPy-50/NF//AC device exhibits a high energy density of 34.62 Wh/kg at a power density of 120.19 W/kg with good cycling performance (80.64% of the initial capacitance retention at 50 mA/cm2 over 2500 cycles). The superior electrochemical performance can be attributed to the combined contribution of both component and unique core–shell heterostructure. The results demonstrate that the ...
TL;DR: This work demonstrates enhanced water and light stability of high-surface-area colloidal perovskite nanocrystals by encapsulation of colloidal CsPbBr3 quantum dots into matched hydrophobic macroscale polymeric matrices, and provides a robust platform for diverse photonic applications.
Abstract: Lead halide perovskites hold promise for photonic devices, due to their superior optoelectronic properties. However, their use is limited by poor stability and toxicity. We demonstrate enhanced water and light stability of high-surface-area colloidal perovskite nanocrystals by encapsulation of colloidal CsPbBr3 quantum dots into matched hydrophobic macroscale polymeric matrices. This is achieved by mixing the quantum dots with presynthesized high-molecular-weight polymers. We monitor the photoluminescence quantum yield of the perovskite–polymer nanocomposite films under water-soaking for the first time, finding no change even after >4 months of continuous immersion in water. Furthermore, photostability is greatly enhanced in the macroscale polymer-encapsulated nanocrystal perovskites, which sustain >1010 absorption events per quantum dot prior to photodegradation, a significant threshold for potential device use. Control of the quantum dot shape in these thin-film polymer composite enables color tunabilit...
TL;DR: Silver nanoparticles exhibited concentration dependent antibacterial activity and 100% killing of E. coli and P. aeruginosa when the cells were treated with 4.5 and 2.7 μg/mL AgNPs, respectively for 4 h.
Abstract: Understanding the interactions of silver nanoparticles (AgNPs) with the cell surface is crucial for the evaluation of bactericidal activity and for advanced biomedical and environmental applications. Biosynthesis of AgNPs was carried out through in situ reduction of silver nitrate (AgNO3) by cell free protein of Rhizopus oryzae and the synthesized AgNPs was characterized by UV–vis spectroscopy, high resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), ζ-potential analysis, and FTIR spectroscopy. The HRTEM measurement confirmed the formation of 7.1 ± 1.2 nm AgNPs, whereas DLS study demonstrated average hydrodynamic size of AgNPs as 9.1 ± 1.6 nm. The antibacterial activity of the biosynthesized AgNPs (ζ = −17.1 ± 1.2 mV) was evaluated against Gram-negative bacteria such as Escherichia coli and Pseudomonas aeruginosa. The results showed that AgNPs exhibited concentration dependent antibacterial activity and 100% killing of E. coli and P. aeruginosa achieved when the cells were...
TL;DR: A flexible and wearable pressure sensor based on the giant piezocapacitive effect of a three-dimensional microporous dielectric elastomer, which is capable of highly sensitive and stable pressure sensing over a large tactile pressure range and marks the realization of a true tactile pressure sensor.
Abstract: We report a flexible and wearable pressure sensor based on the giant piezocapacitive effect of a three-dimensional (3-D) microporous dielectric elastomer, which is capable of highly sensitive and stable pressure sensing over a large tactile pressure range. Due to the presence of micropores within the elastomeric dielectric layer, our piezocapacitive pressure sensor is highly deformable by even very small amounts of pressure, leading to a dramatic increase in its sensitivity. Moreover, the gradual closure of micropores under compression increases the effective dielectric constant, thereby further enhancing the sensitivity of the sensor. The 3-D microporous dielectric layer with serially stacked springs of elastomer bridges can cover a much wider pressure range than those of previously reported micro-/nanostructured sensing materials. We also investigate the applicability of our sensor to wearable pressure-sensing devices as an electronic pressure-sensing skin in robotic fingers as well as a bandage-type pr...
TL;DR: A mechanical sensor with graphene porous network (GPN) combined with polydimethylsiloxane (PDMS) together with nickel foam demonstrated by the first time shows potential applications in monitoring or even recognize the walking states, finger bending degree, and wrist blood pressure.
Abstract: A mechanical sensor with graphene porous network (GPN) combined with polydimethylsiloxane (PDMS) is demonstrated by the first time. Using the nickel foam as template and chemically etching method, the GPN can be created in the PDMS-nickel foam coated with graphene, which can achieve both pressure and strain sensing properties. Because of the pores in the GPN, the composite as pressure and strain sensor exhibit wide pressure sensing range and highest sensitivity among the graphene foam-based sensors, respectively. In addition, it shows potential applications in monitoring or even recognize the walking states, finger bending degree, and wrist blood pressure.
TL;DR: An asymmetric supercapacitor based on Ni,Co-OH/rGO and three-dimensional (3D) hierarchical porous carbon is developed, exhibiting a high energy density along with remarkable cycling stability (80% retention after 17 000 cycles), which holds great promise for practical applications in energy storage devices.
Abstract: Nanolayered structures present significantly enhanced electrochemical performance by facilitating the surface-dependent electrochemical reaction processes for supercapacitors, which, however, causes capacitance fade upon cycling due to their poor chemical stability. In this work, we report a simple and effective approach to develop a stable, high performance electrode material by integrating 2D transition metal hydroxide and reduced graphene oxide sheets at nanometer scale. Specifically, a hybrid nanolayer of Ni–Co hydroxide @reduced graphene oxide (Ni,Co–OH/rGO) with an average thickness of 1.37 nm is synthesized through an easy one-pot hydrothermal method. Benefiting from the face to face contact model between Ni–Co hydroxide and rGO sheets, such unique structure presents superior specific capacitance and cycling performance as compared to the pure Ni–Co hydroxide nanolayers. An asymmetric supercapacitor based on Ni,Co–OH/rGO and three-dimensional (3D) hierarchical porous carbon is developed, exhibiting...
TL;DR: The integration of an environmentally friendly PBA cathode, a nontoxic and low-cost Zn anode, and a biodegradable ionic liquid-water electrolyte provides new perspective to develop rechargeable zinc ion batteries for various applications in electric energy storage.
Abstract: The development of rechargeable zinc ion batteries with high capacity and high cycling stability is a great challenge in aqueous solution due to hydrogen evolution and dendritic growth of zinc. In this study, we present a zinc ion secondary battery, comprising a metallic zinc anode, a bio-ionic liquid–water electrolyte, and a nanostructured prussian blue analogue (PBA) cathode. Both the Zn anode and the PBA cathode exhibit good compatibility with the bio-ionic liquid-water electrolyte, which enables the electrochemical deposition/dissolution of zinc at the zinc anode, and reversible insertion/extraction of Zn2+ ions at the PBA cathode. The cell exhibits a well-defined discharge voltage plateau of ∼1.1 V with a specific capacity of about 120 mAh g–1 at a current of 10 mA g–1 (∼0.1 C). The Zn anode shows great reversibility, and dendrite-free Zn deposits were obtained after 100 deposition/dissolution cycles. The integration of an environmentally friendly PBA cathode, a nontoxic and low-cost Zn anode, and a ...
TL;DR: The proposed electrode structure capitalizes on the high specific capacitance of MnO2 and the ability of MXenes to improve conductivity and cycling stability and exhibited excellent cycling stability.
Abstract: Transition-metal carbides (MXenes) are an emerging class of two-dimensional materials with promising electrochemical energy storage performance. Herein, for the first time, by direct chemical synthesis, nanocrystalline e-MnO2 whiskers were formed on MXene nanosheet surfaces (e-MnO2/Ti2CTx and e-MnO2/Ti3C2Tx) to make nanocomposite electrodes for aqueous pseudocapacitors. The e-MnO2 nanowhiskers increase the surface area of the composite electrode and enhance the specific capacitance by nearly 3 orders of magnitude compared to that of pure MXene-based symmetric supercapacitors. Combined with enhanced pseudocapacitance, the fabricated e-MnO2/MXene supercapacitors exhibited excellent cycling stability with ∼88% of the initial specific capacitance retained after 10000 cycles which is much higher than pure e-MnO2-based supercapacitors (∼74%). The proposed electrode structure capitalizes on the high specific capacitance of MnO2 and the ability of MXenes to improve conductivity and cycling stability.
TL;DR: These findings demonstrate the promising catalytic activity of LDHs for scale-up alkaline water splitting and approaches the performance of platinum (Pt) for HER.
Abstract: Efficient and durable electrocatalysts from earth-abundant elements play a vital role in the key renewable energy technologies including overall water splitting and hydrogen fuel cells. Here, generally used CoFe based layered double hydroxides (LDHs) were first delaminated and exfoliated in the DMF-ethanol solvent (CoFe LDH-F), with enhancement both in oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The exfoliation process creates more coordinatively unsaturated metals and improves the intrinsic electronic conductivity, which is important in water electrolyzer reactions. In the basic solution, the CoFe LDH-F catalyst outperforms the commercial iridium dioxide (IrO2) electrocatalyst in activity and stability for OER and approaches the performance of platinum (Pt) for HER. The bifunctional electrocatalysts can be further used for overall water splitting, with a current density of ∼10 mA/cm2 at the applied voltage of 1.63 V for long-term electrolysis test, rivalling the performance of Pt and IrO2 combination as benchmarks. Our findings demonstrate the promising catalytic activity of LDHs for scale-up alkaline water splitting.
TL;DR: The optimized ZnO@ZIF-8-based nanocomposite sensor shows markedly selective response to H2 in comparison with the pristine ZnNO nanowires sensor, while showing the negligible sensing response to C7H8 and C6H6.
Abstract: Gas sensors are of a great interest for applications including toxic or explosive gases detection in both in-house and industrial environments, air quality monitoring, medical diagnostics, or control of food/cosmetic properties. In the area of semiconductor metal oxides (SMOs)-based sensors, a lot of effort has been devoted to improve the sensing characteristics. In this work, we report on a general methodology for improving the selectivity of SMOx nanowires sensors, based on the coverage of ZnO nanowires with a thin ZIF-8 molecular sieve membrane. The optimized ZnO@ZIF-8-based nanocomposite sensor shows markedly selective response to H2 in comparison with the pristine ZnO nanowires sensor, while showing the negligible sensing response to C7H8 and C6H6. This original MOF-membrane encapsulation strategy applied to nanowires sensor architecture pave the way for other complex 3D architectures and various types of applications requiring either gas or ion selectivity, such as biosensors, photo(catalysts), and ...
TL;DR: This study provides scientific basis for rational construction of Z-scheme photocatalytic system by verified the increased hydroxyl radical generation and improved photocurrent on WO3-Cu-gC3N4 (with the desired Fermi level structure), and demonstrated the necessity of a suitable electron mediator in Z-Scheme system.
Abstract: Z-scheme photocatalytic system shows superiority in degradation of refractory pollutants and water splitting due to the high redox capacities caused by its unique charge transfer behaviors. As a key component of Z-scheme system, the electron mediator plays an important role in charge carrier migration. According to the energy band theory, we believe the interfacial energy band bendings facilitate the electron transfer via Z-scheme mechanism when the Fermi level of electron mediator is between the Fermi levels of Photosystem II (PS II) and Photosystem I (PS I), whereas charge transfer is inhibited in other cases as energy band barriers would form at the semiconductor-metal interfaces. Here, this inference was verified by the increased hydroxyl radical generation and improved photocurrent on WO3-Cu-gC3N4 (with the desired Fermi level structure), which were not observed on either WO3-Ag-gC3N4 or WO3-Au-gC3N4. Finally, photocatalytic degradation rate of 4-nonylphenol on WO3-Cu-gC3N4 was proved to be as high a...