Large-Scale Preparation of Mechanically High-Performance and Biodegradable PLA/PHBV Melt-Blown Nonwovens with Nanofibers

Biodegradable polylactic acid(PLA)melt-blown nonwovens are attractive candidates to replace nondegradable polypropylene melt-blown nonwovens.However,it is still an extremely challenging task to prepare PLA melt-blown nonwovens with sufficient mechanical properties for practical application.Herein,we report a simple strategy for the large-scale preparation of biodegradable PLA/poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)melt-blown nonwovens with high strength and excellent toughness.In this process,a small amount of PHBV is added to PLA to improve the latter’s crystallization rate and crystallinity.In addition,when the PHBV content increases from 0 to 7.5 wt%,the diameters of the PLA/PHBV melt-blown fibers decrease significantly(with the proportion of nanofibers increasing from 7.7%to 42.9%).The resultant PLA/PHBV(5 wt%PHBV)melt-blown nonwovens exhibit the highest mechanical properties.The tensile stress,elongation,and toughness of PLA/PHBV(5 wt%PHBV)melt-blown nonwovens reach 2.5 MPa,45%,and 1.0 MJm3,respectively.More importantly,PLA/PHBV melt-blown nonwovens can be completely degraded into carbon dioxide and water after four months in the soil,making them environmentally friendly.A general tensile-failure model of melt-blown nonwovens is proposed in this study,which may shed light on mechanical performance enhancement for nonwovens.

Diphylleia Grayi-Inspired Intelligent Temperature-Responsive Transparent Nanofiber Membranes

Nanofiber membranes(NFMs) have become attractive candidates for next-generation flexible transparent materials due to their exceptional flexibility and breathability. However, improving the transmittance of NFMs is a great challenge due to the enormous reflection and incredibly poor transmission generated by the nanofiber-air interface. In this research, we report a general strategy for the preparation of flexible temperature-responsive transparent(TRT) membranes,which achieves a rapid transformation of NFMs from opaque to highly transparent under a narrow temperature window. In this process, the phase change material eicosane is coated on the surface of the polyurethane nanofibers by electrospray technology. When the temperature rises to 37 ℃, eicosane rapidly completes the phase transition and establishes the light transmission path between the nanofibers, preventing light loss from reflection at the nanofiber-air interface. The resulting TRT membrane exhibits high transmittance(> 90%), and fast response(5 s). This study achieves the first TRT transition of NFMs, offering a general strategy for building highly transparent nanofiber materials, shaping the future of next-generation intelligent temperature monitoring, anti-counterfeiting measures, and other high-performance devices.

Fibrous MXene Aerogels with Tunable Pore of Contaminated Seawater

The seawater desalination based on solardriven interfacial evaporation has emerged as a promising technique to alleviate the global crisis on freshwater shortage.However,achieving high desalination performance on actual,oil-contaminated seawater remains a critical challenge,because the transport channels and evaporation interfaces of the current solar evaporators are easily blocked by the oil slicks,resulting in undermined evaporation rate and conversion efficiency.Herein,we propose a facile strategy for fabricating a modularized solar evaporator based on flexible MXene aerogels with arbitrarily tunable,highly ordered cellular/lamellar pore structures for high-efficiency oil interception and desalination.The core design is the creation of 1D fibrous MXenes with sufficiently large aspect ratios,whose superior flexibility and plentiful link forms lay the basis for controllable 3D assembly into more complicated pore structures.The cellular pore structure is responsible for effective contaminants rejection due to the multi-sieving effect achieved by the omnipresent,isotropic wall apertures together with underwater superhydrophobicity,while the lamellar pore structure is favorable for rapid evaporation due to the presence of continuous,large-area evaporation channels.The modularized solar evaporator delivers the best evaporation rate(1.48 kg m-2h-1)and conversion efficiency(92.08%)among all MXene-based desalination materials on oil-contaminated seawater.

Highly Efficient and Stable FAPbI_(3) Perovskite Solar Cells and Modules Based on Exposure of the(011)Facet

Perovskite crystal facets greatly impact the performance and stability of their corresponding photovoltaic devices.Compared to the(001)facet,the(011)facet yields better photoelectric properties,including higher conductivity and enhanced charge carrier mobility.Thus,achieving(011)facet-exposed films is a promising way to improve device performance.However,the growth of(011)facets is energetically unfavorable in FAPbI_(3) perovskites due to the influence of methylammonium chloride additive.Here,1-butyl-4-methylpyridinium chloride([4MBP]Cl)was used to expose(011)facets.The[4MBP]^(+)cation selectively decreases the surface energy of the(011)facet enabling the growth of the(011)plane.The[4MBP]^(+)cation causes the perovskite nuclei to rotate by 45°such that(011)crystal facets stack along the out-of-plane direction.The(011)facet has excellent charge transport properties and can achieve better-matched energy level alignment.In addition,[4MBP]Cl increases the activation energy barrier for ion migration,suppressing decomposition of the perovskite.As a result,a small-size device(0.06 cm2)and a module(29.0 cm2)based on exposure of the(011)facet achieved power conversion efficiencies of 25.24%and 21.12%,respectively.

Sustainable Generation of Sulfate Radicals and Decontamination of Micropollutants via Sequential Electrochemistry

The removal of emerging micropollutants in the aquatic environment remains a global challenge.Conventional routes are often chemically,energetically,and operationally intensive,which decreases their sustainability during applications.Herein,we develop an advanced chemical-free strategy for micropollutants decontamination that is solely based on sequential electrochemistry involving ubiquitous sulfate anions in natural and engineered waters.This can be achieved via a chain reaction initiated by electrocatalytic anodic sulfate(SO_(4)^(2-))oxidation to produce persulfate(S_(2)O_(8)^(2-))and followed by a cathodic persulfate reduction to produce sulfate radicals(SO_(4)^(·-)).These SO_(4)^(·-)are powerful reactive species that enable the unselective degradation of micropollutants and yield SO_(4)^(2-)again in the treated water.The proposed flow-through electrochemical system achieves the efficient degradation(100.0%)and total organic carbon removal(65.0%)of aniline under optimized conditions with a single-pass mode.We also reveal the effectiveness of the proposed system for the degradation of a wide array of emerging micropollutants over a broad pH range and in complex matrices.This work provides the first proof-ofconcept demonstration using ubiquitous sulfate for micropollutants decontamination,making water purification more sustainable and more economical.

Smart Interfacing between Co-Fe Layered Double Hydroxide and Graphitic Carbon Nitride for High-efficiency Electrocatalytic Nitrogen Reduction

Bimetallic compounds such as hydrotalcite-type layered double hydroxides(LDHs)are promising electrocatalysts owing to their unique electronic structures.However,their abilities toward nitrogen adsorption and reduction are undermined since the surface-mantled,electronegative-OH groups hinder the charge transfer between transition metal atoms and nitrogen molecules.Herein,a smart interfacing strategy is proposed to construct a coupled heterointerface between LDH and 2D g-C_(3)N_(4),which is proven by density functional theory(DFT)investigations to be favorable for nitrogen adsorption and ammonia desorption compared with neat LDH surface.The interfaced LDH and g-C_(3)N_(4) is further hybridized with a self-standing TiO_(2) nanofibrous membrane(NM)to maximize the interfacial effect owing to its high porosity and large surface area.Profited from the synergistic superiorities of the three components,the LDH@C_(3)N_(4)@TiO_(2) NM delivers superior ammonia yield(2.07×10^(−9) mol s^(−1) cm^(−2))and Faradaic efficiency(25.3%),making it a high-efficiency,noble-metal-free catalyst system toward electrocatalytic nitrogen reduction.

Earthquake-triggered landslide interpretation model of high resolution remote sensing imageries based on bag of visual word

Traditional visual interpretation is often inefficient due to its excessively workload professional knowledge and strong subjectivity.Therefore,building an automatic interpretation model on high spatial resolution remote sensing images is the key to the quick and efficient interpretation of earthquake-triggered landslides.Aiming at addressing this problem,a landslide interpretation model of high-resolution images based on bag of visual word(BoVW)feature was proposed.The high-resolution images were pre-processed,and then BoVW feature and support vector machine(SVM)was adopted to establish an automatic landslide interpretation model.This model was further compared with the currently widely used Histogram of Oriented Gradient(HoG)feature extraction model.In order to test the effectiveness of the method,typical landslide images were selected to construct a landslide sample library,which was subsequently utilized as the foundation for conducting an experimental study.The results show that the accuracy of landslide extraction using this method reaches as high as 89%,indicating that the method can be used for the automatic interpretation of landslides in disaster-prone areas,and has high practical value for regional disaster prevention and damage reduction.

内镜下硬化术与吻合器痔上黏膜环切术治疗内痔的对比研究

目的研究内镜下硬化术与吻合器痔上黏膜环切术(PPH)治疗内痔的疗效和安全性。方法选取2015年3月-2020年8月九江市第一人民医院收治的100例内痔患者作为研究对象,分别采用结肠镜下聚桂醇注射术和PPH治疗,随访6个月,观察两组症状改善、术后并发症、有效率、平均住院天数及费用等情况。结果硬化组治疗总有效率为94.0%,PPH组治疗总有效率为88.0%,两组比较,差异无统计学意义(P>0.05)。硬化组平均住院时间、住院费用、患者满意度明显优于对照组,术后疼痛评分明显低于PPH组,差异均有统计学意义(P<0.05)。硬化组并发症总发生率为8.0%,明显低于PPH组的32.0%,差异有统计学意义(P<0.05)。结论内痔内镜下硬化术操作简单,恢复快,安全有效,值得临床推广应用。

From 1D Nanofibers to 3D Nanofibrous Aerogels: A Marvellous Evolution of Electrospun SiO_(2) Nanofibers for Emerging Applications

One-dimensional(1D)SiO_(2) nanofibers(SNFs),one of the most popular inorganic nanomaterials,have aroused widespread attention because of their excellent chemical stability,as well as unique optical and thermal characteristics.Electrospinning is a straightforward and versatile method to prepare 1D SNFs with programmable structures,manageable dimensions,and modifiable properties,which hold great potential in many cutting-edge applications including aerospace,nanodevice,and energy.In this review,substantial advances in the structural design,controllable synthesis,and multifunctional applications of electrospun SNFs are highlighted.We begin with a brief introduction to the fundamental principles,available raw materials,and typical apparatus of electrospun SNFs.We then discuss the strategies for preparing SNFs with diverse structures in detail,especially stressing the newly emerging three-dimensional SiO_(2) nanofibrous aerogels.We continue with focus on major breakthroughs about brittleness-to-flexibility transition of SNFs and the means to achieve their mechanical reinforcement.In addition,we showcase recent applications enabled by electrospun SNFs,with particular emphasis on physical protection,health care and water treatment.In the end,we summarize this review and provide some perspectives on the future development direction of electrospun SNFs.

Transformation of Fibrous Membranes from Opaque to Transparent under Mechanical Pressing

There is a great demand for transparent films,membranes,or substrates in the fields of intelligent wearables,electronic skins,air filtration,and tissue engineering.Traditional materials such as glass and plastics cannot satisfy these requirements because of the lack of interconnected pores,undesirable porosity,and flexibility.Electrospun fibrous membranes offset these shortcomings because they contain small pores and have high porosity as well as outstanding flexibility.Thus,the development of transparent electrospun fibrous membranes is of great value.This work reports a simple and effective way to develop flexible and porous transparent fibrous membranes(TFMs)directly from electrospun fibrous membranes via mechanical pressing,without employing any other additives.In addition,the relationship between the transparency performance and the molecular structure of the polymers after pressing was summarized for the first time.After mechanical pressing,the membranes maintained fibrous morphology,micron-sized pores,and desired porosity.Polystyrene fibrous membranes,which exhibited excellent optical and mechanical properties,were used as a reference.The TFMs possessed high transparency(~89%visible light transmittance at 550 nm),high porosity(10%–30%),and strong mechanical tensile strength(~148 MPa),nearly 78 times that of the pristine electrospun fibrous membranes.Moreover,this study demonstrated that transparent and conductive membranes can be fabricated based on TFMs using vacuum-assisted filtration of silver nanowires followed by mechanical pressing.Compared with indium tin oxide films,conductive TFMs exhibited good electrical conductivities(9Ωper square(Ω·sq^(−1)),78%transmittance at 550 nm)and notable mechanical performance(to bear abundant bending stresses).

Thermal Modeling and Analysis of Metal Foam Heat Sink with Thermal Equilibrium and Non-Equilibrium Models

In the present study,the thermal performance of metal foam heat sink was numerically investigated by adopting the local thermal non-equilibrium(LTNE)model and local thermal equilibrium(LTE)model.Temperature field distributions and temperature difference field distributions of solid and fluid phases were presented.Detailed thermal performance comparisons based on the LTE and LTNE models were evaluated by considering the effects of the relevant metal foam morphological and channel geometrical parameters.Results indicate that a distinct temperature difference exists between the solid and fluid phases when the LTNE effect is pronounced.The average Nusselt numbers predicted by both the LTE and LTNE models are approaching with the increase of porosity,pore density,Reynolds number,large thermal conductivity ratio,and large aspect ratio.This is attributed to the significant reduction of the interstitial convective thermal resistance between the solid and fluid phases,as a result,the LTE model can replace the LTNE model for thermal modeling in these conditions.In addition,the overall thermal performance assessment of metal foam heat sink is compared with the non-porous heat sink,and it shows that the thermal performance factor of metal foam heat sink is approximately two times of the non-porous heat sink.

A New Method of Roughness Construction and Analysis of Construct Parameters

In micro-manufacturing,roughness is unavoidable due to the tolerance of micro-machining methods.Roughness in microchannel could have a significant influence on flow and heat transfer since the size of microchannel is very small.In our work,roughness is modeled as a superposition of waves.A simple Fourier series method is proposed to construct the rough surface.With this method,roughness is constructed on the bottom of the rectangular microchannel which has a hydraulic diameter of 0.5 mm.Two important parameters during roughness construction,triangulate size and correlation length are studied under the same relative roughness 1%.Results show that flow and heat transfer characteristics are not sensitive to triangulate size.While triangulate size is changing from 0.1 mm to 0.05 mm,the variations of pressure drop and average Nusselt number are less than 1%.Correlation length could influence the topography of roughness surface a lot,smaller correlation length will lead to more pressure drop and lower Nusselt number.

Advanced nanofabrication for elastic inorganic aerogels

Inorganic aerogels with low density,high porosity,large specific surface area,and superior mechanical properties are excellent candidate materials in fields such as thermal management,energy,catalysis,and biomedical applications.A comprehensive overview of existing elastic inorganic aerogels is provided,covering their structural units,preparation methods,mechanical performances,and applications.Meanwhile,based on the constituent building blocks and microstructures,a detailed analysis of the mechanical properties and guidelines for elastic design of aerogels is presented.Concluding with a succinct summary of prospective developmental direction,this review deliberates on the challenges and potential opportunities of elastic inorganic aerogels,with the intent of providing a versatile platform for designing new types of elastic inorganic aerogels for various applications.

A review on flexible solar cells

With the gradual progression of the carbon neutrality target,the future of our electricity supply will experience a massive increase in solar generation,and approximately 50%of the global electricity generation will come from solar generation by 2050.This provides the opportunity for researchers to diversify the applications of photovoltaics(PVs)and integrate for daily use in the future.Flexible solar cell technology is the next frontier in solar PV and is the key way to achieve CO_(2)neutrality.The integration of PV technology with other fields will greatly broaden the development areas for the PV industry,providing products with higher added value.In this paper,we reviewed the latest research progress on flexible solar cells(perovskite solar cells,organic solar cells,and flexible silicon solar cells),and proposed the future applications of flexible solar cell technology.

Multi-stable straw-like carbon nanotubes for mechanical programmability at microscale

Inspired by macroscale 3D pixel mechanical metamaterials and microscale straw-like carbon nanotube,we propose a design of multi-stable straw-like carbon nanotubes(MSCNT)via optimizing the structure of a unit to obtain multiple stable states under dis-placement loading by molecular dynamics.The unit of MSCNT is mirror-symmetrically connected two truncated graphene cones with specific apex angles.By switching the LJ term in AIREBO potential,we verify that the bistability of unit is co-determined by snap-through instability and microscale adhesions.Moreover,we examine the validity of the multi-stability of the unit cells arranged in series and in parallels.Simulation results indicate that the MSCNT can achieve mechanical programmability in microscale,which triggers many potential applications in need of customizing nanos-cale mechanical behaviors.

Smart Fibers for Self‑Powered Electronic Skins

Smart fibers are considered as promising materials for the fabrication of wearable electronic skins owing to their features such as superior flexibility,light weight,high specific area,and ease of modification.Besides,piezoelectric or triboelectric electronic skins can respond to mechanical stimulation and directly convert the mechanical energy into electrical power for self-use,thereby providing an attractive method for tactile sensing and motion perception.The incorporation of sensing capabilities into smart fibers could be a powerful approach to the development of self-powered electronic skins.Herein,we review several aspects of the recent advancements in the development of self-powered electronic skins constructed with smart fibers.The summarized aspects include functional material selection,structural design,pressure sensing mechanism,and proof-to-concept demonstration to practical application.In particular,various fabrication strategies and a wide range of practical applications have been systematically introduced.Finally,a critical assessment of the challenges and promising perspectives for the development of fiber-based electronic skins has been presented.

Composite Eu-MOF@CQDs“off&on”ratiometric luminescent probe for highly sensitive chiral detection of l-lysine and 2-methoxybenzaldehyde

The high amount of l-lysine can increase the potential risk of cardiovascular disease.Additionally,2-methoxy benzaldehyde(2-MB)has high toxicity and can easily pollute the environment.In this work,carbon quantum dots(CQDs)can be encapsulated into Eu-BTB(H_(3)BTB=1,3,5-tri(4-carboxyphenyl)benzene),forming the multi-emission composite material Eu-BTB@CQDs.It has two emissions peaks(617 nm for Eu and 470 nm for CQDs).Eu-BTB@CQDs can be applied as bi-functional ratiometric“off&on”luminescent sensor for l-lysine and 2-MB with high sensitivity and selectivity,the low limit of detection(LOD)for l-lysine is 3.68μmol/L and for 2-MB is 0.54μmol/L,respectively.Additionally,Eu-BTB@CQDs can quantitatively discriminate l-lysine in the mixed d-and l-lysine water solutions(five different concentrations ratio of l/d-lysine has been set)makes the chiral detection of l-lysine are more meaningful.On the other hand,Eu-BTB@CQDs also can detect 2-MB over 4-methoxybenzaldehyde(4-MB)with high selectivity.Further the detection of 2-MB and l-lysine in the lake water real samples with the reasonable recovery rate.Finally,the detection mechanisms for l-lysine and 2-MB were also investigated and discussed in detail.

Recent Advances in Ultrafine Fibrous Materials for Effective Warmth Retention

Extremely cold environment has led to a variety of serious public health issues and posed huge burden on the social econ-omy,which is an urgent challenge to the human worldwide.Featured with comfort,convenience,and cost-effectiveness,fibrous materials have been selected as heat insulation materials to protect the human body against the cold for centuries.The advanced ultrafine fibers,with remarkable softness,small average diameter and pore size,and high porosity,have found extensive attention,as promising candidate for application in reducing the heat loss.In this review,the heat transfer mechanisms for single fiber and fiber assembly are provided,and the typical categories of ultrafine fibrous materials for warmth retention,classified as fibrous membrane and fibrous sponge in terms of aggregate structures,are systematically summarized.In particular,this review comprehensively discusses the fabrication strategies,structure characteristics,and significant properties of various ultrafine fibrous materials.Finally,the current challenges and future development prospects of ultrafine fibrous materials for effective warmth retention are highlighted.

导热和自然对流对石蜡定向熔化特性的影响

相变散热器在有效保障功率瞬变、间歇性工作电子器件安全运行方面具有极大潜力.针对现有相变散热器性能亟需进一步提升的问题,本文通过改变加热位置和添加泡沫铜,实验探究了石蜡在导热+自然对流、导热、导热增强+自然对流抑制以及导热增强4种作用条件下的定向熔化特性.研究发现,在导热和自然对流同时作用条件下,石蜡的温度经历缓慢上升、极速上升、缓慢波动和继续上升4个阶段,自然对流的作用可将相变散热器的有限保护时间从导热作用时的483 s延长至4400 s.虽然添加泡沫铜能降低石蜡内部的温度梯度,但会延长自然对流作用的起始时间、缩短作用时长以及削弱作用强度,导致自然对流的作用权重比从8.1降至0.72,有效保护时间仅提升80 s.因此,采用相变材料(phase change material, PCM)散热器冷却低热流密度的电子器件时,应优先强化工质熔化过程中的自然对流,随着热流密度的增加,再逐渐强化其导热性能.

Highly stable carbon-based perovskite solar cell with a record efficiency of over 18% via hole transport engineering

Carbon-based perovskite solar cells show great potential owing to their low-cost production and superior stability in air, compared to their counterparts using metal contacts. The photovoltaic performance of carbon-based PSCs, however, has been progressing slowly in spite of an impressive efficiency when they were first reported. One of the major obstacles is that the hole transport materials developed for stateof-the-art Au-based PSCs are not suitable for carbon-based PSCs. Here, we develop a low-temperature,solution-processed Poly(3-hexylthiophene-2,5-diyl)(P3 HT)/graphene composite hole transport layer(HTL), that is compatible with paintable carbon-electrodes to produce state-of-the-art perovskite devices. Space-charge-limited-current measurements reveal that the as-prepared P3 HT/graphene composite exhibits outstanding charge mobility and thermal tolerance, with hole mobility increasing from8.3 × 10^-3 cm^2 V-1 s-1(as-deposited) to 1.2 × 10^-2 cm2 V^-1 s^-1(after annealing at 100°C)-two orders of magnitude larger than pure P3 HT. The improved charge transport and extraction provided by the composite HTL provides a significant efficiency improvement compared to cells with a pure P3 HT HTL. As a result, we report carbon-based solar cells with a record efficiency of 17.8%(certified by Newport);and the first perovskite cells to be certified under the stabilized testing protocol. The outstanding device stability is demonstrated by only 3% drop after storage in ambient conditions(humidity: ca. 50%) for 1680 h(nonencapsulated), and retention of ca. 89% of their original output under continuous 1-Sun illumination at room-temperature for 600 h(encapsulated) in a nitrogen environment.