Extensive Interest In Recent Years Research Articles

Enhanced photon harvesting by embedding cost-effective polystyrene microspheres as light scatterers in the perovskite photodetector

Solution processed perovskite photodetectors have attracted extensive interest in recent years.

Face Image Compression and Reconstruction Based on Improved PCA

Face recognition technology has many usages in the real-world applications, and it has generated extensive interest in recent years. However, the amount of data in a digital image is growing explosively, taking up a lot of storage and transmission resources. There is a lot of redundancy in an image data representation. Thus, image compression has become a hot topic. The principal component analysis (PCA) can effectively remove the correlation of an image and condense the image information into a characteristic image with several main components. At the same time, it can restore different data images according to their principal components and meet the needs of image compression and reconstruction at diverse levels. This paper introduces an improved PCA algorithms. The covariance matrix, calculated according to a batch of training samples, is an approximation of the real covariance matrix. The matrix is relatively to the dimension of the covariance matrix, and the number of training samples is often too small. Therefore, it difficult to accurately obtain the covariance matrix. This improved PCA algorithm called 2DPCA can solve this problem effectively. By comparing it with several discrete PCA improvement algorithms, we show that the 2DPCA has a better dimensionality reduction effect. Compared with the PCA algorithm, the 2DPCA has a lower root-mean-square error under the constant noise condition.

Optimizing the Proton Conductivity of Fe-Diphosphonates by Increasing the Relative Number of Protons and Carrier Densities.

Proton conductive materials have attracted extensive interest in recent years due to their fascinating applications in sensors, batteries, and proton exchange membrane fuel cells. Herein, two Fe-diphosphonate chains (H4-BAPEN)0.5·[FeIII(H-HEDP)(HEDP)0.5(H2O)] (1) and (H4-TETA)2·[FeIII2FeII(H-HEDP)2(HEDP)2(OH)2]·2H2O (2) (HEDP = 1-hydroxyethylidenediphosphonate, BAPEN = 1,2-bis(3-aminopropylamino)ethane, and TETA = triethylenetetramine) with different templating agents were prepared by hydrothermal reactions. The valence states of the Fe centers were demonstrated by 57Fe Mössbauer spectra at 100 K, with a high-spin FeIII state for 1 and mixed high-spin FeIII/FeII states for 2. Their magnetic properties were determined, which featured strong antiferromagnetic couplings in the chain. Importantly, the proton conductivity of both compounds at 100% relative humidity was explored at different temperatures, with 2.79 × 10-4 S cm-1 at 80 °C for 1 and 7.55 × 10-4 S cm-1 at 45 °C for 2, respectively. This work provides an opportunity for improving proton conductive properties by increasing the relative number of protons and the carrier density using protonated flexible aliphatic amines.

Nickel sulfide-based energy storage materials for high-performance electrochemical capacitors

Supercapacitors are favorable energy storage devices in the field of emerging energy technologies with high power density, excellent cycle stability and environmental benignity. The performance of supercapacitors is definitively influenced by the electrode materials. Nickel sulfides have attracted extensive interest in recent years due to their specific merits for supercapacitor application. However, the distribution of electrochemically active sites critically limits their electrochemical performance. Notable improvements have been achieved through various strategies such as building synergetic structures with conductive substrates, enhancing the active sites by nanocrystallization and constructing nanohybrid architecture with other electrode materials. This article overviews the progress in the reasonable design and preparation of nickel sulfides and their composite electrodes combined with various bifunctional electric double-layer capacitor (EDLC)-based substances (e.g., graphene, hollow carbon) and pseudocapacitive materials (e.g., transition-metal oxides, sulfides, nitrides). Moreover, the corresponding electrochemical performances, reaction mechanisms, emerging challenges and future perspectives are briefly discussed and summarized. This review presents the progress in the reasonable design and preparation of nickel sulfides and their applications in electrochemical capacitors. The corresponding electrochemical performances, reaction mechanisms, emerging challenges, and future perspectives are briefly discussed and summarized.

Three-terminal Weyl complex with double surface arcs in a cubic lattice

Exploring unconventional topological quasiparticles and their associated exotic physical properties has become a hot topic in condensed matter physics, thus stimulating extensive interest in recent years. Here, in contrast to the double-Weyl phonons (the topological chiral charge +2) in the trigonal and hexagonal crystal systems, we propose that the unconventional double-Weyl without counterparts in high-energy physics can emerge in the phonons of cubic structures, i.e., SrSi2. Employing a two-band k ⋅ p Hamiltonian, we prove that the quadratic double-Weyl nodes are protected by the fourfold screw rotational symmetry {tilde{C}}_{4}. Strikingly, we find that the surface arcs are terminated with the Weyl nodes that possess unequal topological charges with opposite sign (i.e., +2 and −1), leading to unique three-terminal Weyl complex (one quadratic double-Weyl and two linear single-Weyl) with double surface arcs in SrSi2. In addition, we apply a uniaxial tensile strain along z-axis to examine the evolution of the three-terminal Weyl complex when the corresponding symmetries are broken. Our work not only provides an ideal candidate for the realization of the quadratic double-Weyl and the corresponding unique surface arc states, but also broadens the understanding of topological Weyl physics.

Ultrasensitive and fast photoresponse in graphene/silicon-on-insulator hybrid structure by manipulating the photogating effect

Abstract The hybrid structures of graphene with semiconductor materials based on photogating effect have attracted extensive interest in recent years due to the ultrahigh responsivity. However, the responsivity (or gain) was increased at the expense of response time. In this paper, we devise a mechanism which can obtain an enhanced responsivity and fast response time simultaneously by manipulating the photogating effect (MPE). This concept is demonstrated by using a graphene/silicon-on-insulator (GSOI) hybrid structure. An ultrahigh responsivity of more than 107 A/W and a fast response time of 90 µs were obtained. The specific detectivity D* was measured to be 1.46 ⨯ 1013 Jones at a wavelength of 532 nm. The Silvaco TCAD modeling was carried out to explain the manipulation effect, which was further verified by the GSOI devices with different doping levels of graphene in the experiment. The proposed mechanism provides excellent guidance for modulating carrier distribution and transport, representing a new route to improve the performance of graphene/semiconductor hybrid photodetectors.

High-Performance Triboelectric Nanogenerators Based on a Mechanoradical Mechanism

Flexible nanogenerators (NGs) with high power output and high efficiency have attracted extensive interests in recent years. Herein, we report highly efficient, mechanoradical-based NGs based on po...

Distributed Multiagent Coordinated Learning for Autonomous Driving in Highways Based on Dynamic Coordination Graphs

Autonomous driving is one of the most important AI applications and has attracted extensive interest in recent years. A large number of studies have successfully applied reinforcement learning techniques in various aspects of autonomous driving, ranging from low-level control of driving maneuvers to higher level of strategic decision-making. However, comparatively less progress has been made in investigating how co-existing autonomous vehicles would interact with each other in a common environment and how reinforcement learning can be helpful in such situations by applying multiagent reinforcement learning techniques in the high-level strategic decision-making of the following or overtaking for a group of autonomous vehicles in highway scenarios. Learning to achieve coordination among vehicles in such situations is challenging due to the unique feature of vehicular mobility, which renders it infeasible to directly apply the existing coordinated learning approaches. To solve this problem, we propose using dynamic coordination graph to model the continuously changing topology during vehicles’ interactions and come up with two basic learning approaches to coordinate the driving maneuvers for a group of vehicles. Several extension mechanisms are then presented to make these approaches workable in a more complex and realistic setting with any number of vehicles. The experimental evaluation has verified the benefits of the proposed coordinated learning approaches, compared with other approaches that learn without coordination or rely on some traditional mobility models based on some expert driving rules.

Energy harvesters based on fluorinated ethylene propylene unipolar ferroelectrets with negative charges

Energy harvesting devices can convert energy from various ambient sources (that are usually ignored) into electricity to power portable electronic devices and wireless sensor networks. Such devices have stimulated extensive interest in recent years. For the current study, we succeeded in designing and fabricating a new type of energy harvester using high performance unipolar ferroelectrets made from fluorinated ethylene propylene (FEP), consisting of a negatively charged and a noncharged wave-shaped FEP layer. Such materials are resistant to elevated temperatures owing to the thermally stable negative charges in this material. They also exhibit great stretchability due to the symmetric wave-shaped structure. By using a variety of test frequencies, seismic masses, external resistances, and wave-shaped FEP films with different surface potentials, we systematically investigated the energy harvesting performance of these devices. Typically, wave-shaped films with a material thickness of 12.5 μm and a maximum total thickness of the wavy structure (including the air thickness) of about 160 µm were employed. When charged to a surface potential of −500 V and operated with a seismic mass of 3 g fixed on the center of the band shaped unipolar ferroelectret sample, a power of 355 µW for an input acceleration of 1 g (g is the gravity of the Earth) was delivered to the optimal load resistance at the resonance frequency of 22 Hz. The relatively large power generated is due to the sizeable elasticity of the wave-shaped FEP film and the amplification of the force acting on the film in the specifically designed device.

All-Day Mobile Healthcare Monitoring System Based on Heterogeneous Stretchable Sensors for Medical Emergency

Epidermal and wearable electronic sensor technologies have gained extensive interest in recent years owing to deliver real-time healthcare information to the personalized smartphone. Herein, we proposed a fully integrated wearable smart patch-based sensor system with Kirigami-inspired strain-free deformable structures having temperature and humidity sensors along with a commercial acceleration sensor. The presented fully integrated wearable sensor system easily attaches to the skin to accurately determine the body information, and integrated circuit including read-out circuit and wireless communication transfer medical information (temperature, humidity, and motion) to mobile phone to assist with emergencies due to “unpredictable” deviations and to aid in medical checkups for vulnerable patients. This article addresses the challenge of all-day continuous monitoring of human body biological signals by introducing the well-equipped breathable (water permeability ∼ 80 gm−1·h−1), excellent adhesion to the skin (peel strength < 200 gf/12 mm), biocompatible, and conformable smart patch that can absorb the moisture (sweat) generated from the skin without any harshness and allowing the users’ to continuously monitor the early detection of diagnosis. Furthermore, the proposed patch-based medical device enables wireless sensing capabilities in response to rapid variation, equipped with a customized circuit design, low-power Bluetooth module, and a signal processing integrated circuit mounted on a flexible printed circuit board. Thus, a unique platform is established for multifunctional sensors to interface with hard electronics, providing emerging opportunities in the biomedical field as well as Internet-of-Things applications.

High-throughput droplet microfluidic synthesis of hierarchical metal-organic framework nanosheet microcapsules

Using two-dimensional (2D) metal-organic framework (MOF) nanosheets as new building blocks to create more complex architectures at the mesoscopic/macroscopic scale has attracted extensive interest in recent years. Nevertheless, it remains a great challenge to assemble MOF nanosheets into hierarchical hollow structures so far. In this paper, we describe a successful example of hierarchical MOF nanosheet microcapsules, with precisely controlled sizes, produced on large scale within minutes with a continuous droplet microfluidic strategy. Following a reaction/diffusion growth mechanism, the microcapsule shells feature a continuous smooth inner layer and a porous outer layer. Such hierarchical structure enables the encapsulation of magnetite nanoparticles inside and loading of dense gold nanoparticles outside the microcapsules, which exhibit highly efficient heterogeneous catalytic activity and easy recyclability. The present microfluidic assembly method offers a new pathway for preparing hierarchical MOF nanosheet structures, with the potential for extension to the formation of other 2D nanosheets in general.

Chemical Reaction-Driven Spreading of an Organic Extractant on the Gas-Water Interface: Insight into the Controllable Formation of a Gas Bubble-Supported Organic Extractant Liquid Membrane.

The extraction and recovery of low-concentration valuable metals from various complex aqueous solutions or industrial waste waters have attracted extensive interests in recent years. In our previous works, we suggested a novel technique called bubbling organic liquid membrane extraction by spreading and covering an organic extractant with extremely small volume on the surface of gas bubbles to form a layer of the gas bubble-supported organic liquid membrane for selective extraction and enrichment of low-concentration targets from dilute aqueous solutions. It was found that for successfully performing the bubbling organic liquid membrane extraction, a prerequisite is knowing how to control the formation of a stable organic liquid membrane covered on the surface of gas bubbles. However, once the organic extractant starts to spread on the surface of gas bubbles, the extraction chemical reaction at the interface between the organic extractant liquid membrane and the rare-earth aqueous solution will occur. In the present work, the spreading behavior of the organic extractant P507 on the surface of rare-earth aqueous solutions was investigated and was compared with the behaviors on the surface of deionized water. It was revealed that the spreading of the organic extractant P507 on the surface of aqueous solutions containing rare-earth ions was accelerated because of the occurrence of the chemical reactions at the gas-water interface. The difference in the spreading rate of organic extractant P507 liquid droplets on the surface of deionized water and on that of Er(III) aqueous solutions with an increase in the P507 concentration, the saponification degrees of the P507 extractant, and the preloading amount of Er(III) in the P507 extractant revealed that the chemical reaction at the interface between the spreading P507 thin liquid membrane and the Er(III) aqueous solution would result in the Marangoni convection along the interface, which is in favor of overcoming the resistance from the viscous force when the surface tension gradient replaces gravity as a dominant driving force for the spreading. The present work provides an experimental foundation toward understanding the effect of the interfacial chemical reaction on the spreading behavior of an organic oil droplet on the gas-water interface. It is beneficial for the development of our suggested new technique of bubbling organic liquid membrane extraction and to achieve a controllable generation of a stable gas bubble-supported organic liquid membrane for performing solvent extraction at large aqueous-to-oil phase ratios.

Comprehensive dependence of triboelectric nanogenerator on dielectric thickness and external impact for high electric outputs

Triboelectric nanogenerators (TENGs) have aroused extensive interests in recent years, and their energy conversion efficiency increased gradually under massive efforts. Applied force and dielectric thickness are two important factors accounting for the high output performance. Nevertheless, for the most commonly used TENGs in the contact-separation mode, the comprehensive dependence of dielectric thickness and impact force is still expected to be further deeply researched and optimized. Hence, we fabricated a nylon-PTFE TENG in the contact-separation mode and explored the dual influence of dielectric thickness and applied force on the output performance. The results indicate that the dielectric thickness and the magnitude of force have a comprehensive influence on the outputs, which is due to the dual effect of charge transport properties and the microcosmic deformation at different thicknesses. In general, the optimum thickness increases from 0.5 mm to 0.7 mm obviously as the force magnitude increases from 15 N to 60 N, but stays steadily with varying fabric count. With the continuous enlargement of impact force, the dielectric thickness reaches a boundary limitation of 0.8 mm. This work contributes greatly not only to the design and optimization of TENG devices, but also to the deeper understanding of the nano-triboelectric effect mechanism.

NiCu magnetic nanoparticles: review of synthesis methods, surface functionalization approaches, and biomedical applications

Abstract Magnetic nanoparticles (MNPs) have attracted extensive interest in recent years because of their unique magnetic, electronic, catalytical, optical, and chemical properties. Lately, research on bimetallic MNPs based on nickel and copper (NiCu MNPs) gained momentum owing to their desired properties for use in biomedicine, such as their chemical stability, biocompatibility, and highly tunable magnetic properties by means of synthesis parameter tuning. The general interest of using NiCu MNPs in biomedical applications is still low, although it is steadily increasing as can be deduced from the number of related publications in the last years. When exposed to an alternating magnetic field (AMF), superparamagnetic particles (such as NiCu MNPs) generate heat by relaxation losses. Consequently, magnetic hyperthermia in cancer treatment seems to be their most promising application in medicine, although others are emerging as well, such as their use to guide potent drugs to the targeted site or to prolong their localization at a desired site in the body. This review is the first, to the best of our knowledge, that covers the available knowledge related to the preparation of NiCu MNPs using different methods, their resulting properties, and the already developed functionalization methods and that discusses everything mentioned in relation to their possible applicability in biomedicine.

Unanticipated Strong Blue Photoluminescence from Fully Biobased Aliphatic Hyperbranched Polyesters

Nonconventional fluorescent polymers without π-aromatic structure have attracted extensive interest in recent years. Hyperbranched polyesters are generally known because of their industrial applications; however, the luminescent properties of the polyester has not been reported. Herein, we synthesized a series of fully biobased aliphatic hyperbranched polyesters via a one-pot A2 + B3 esterification reaction. Intriguingly, the resultant hyperbranched polyesters carrying no conventional fluorescent units exhibited unexpected bright blue fluorescence under 365 nm UV light. It was found that the fluorescence intensity was enhanced with increasing solution concentrations and molecular weights of the polyesters. Moreover, the results suggested that the luminescence of polyesters could be controlled by solvents and metal ions. In particular, the fluorescence of the polyesters was extremely sensitive to Fe3+. More interesting is that the fluorescence of the polyesters showed an aggregation-induced enhanced emissi...

Isorhapontigenin induced cell growth inhibition and apoptosis by targeting EGFR-related pathways in prostate cancer.

Isorhapontigenin (ISO), a naturally phytopolyphenol compound existing in Chinese herb, apples, and various vegetables, has attracted extensive interest in recent years for its diverse pharmacological characteristics. Increasing evidences reveal that ISO can inhibit cancer cell growth by induced apoptosis, however, the molecular mechanisms is not fully understood. In this study, we found for the first time that ISO apparently induced cell growth inhibition and apoptosis by targeting EGFR and its downstream signal pathways in prostate cancer (PCa) cells both in vitro and in vivo, whereas no obviously effect on normal prostate cells. From the results, we found that ISO competitively targeted EGFR with EGF and inhibited EGFR auto-phosphorylation, and then decreased the levels of p-Erk1/2, p-PI3 K, and p-AKT, and further induced down-regulation of p-FOXO1 and promoted FOXO1 nuclear translocation; and finally resulted in a significantly up-regulation of Bim/p21/27/Bax/cleaved Caspase-3/cleaved PARP-1 and a markedly down-regulation of Sp1/Bcl-2/XIAP/Cyclin D1. Moreover, our experimental data demonstrated that treatment of ISO decreased protein level of AR via both inhibiting the expression of AR gene and promoting the ubiquitination/degradation of AR proteins in proteasome. In vivo, we also found that ISO inhibited the growth of subcutaneous xenotransplanted tumor in nude mice by inducing PCa cell growth inhibition and apoptosis. Taken together, all findings here clearly implicated that EGFR-related signal pathways, including EGFR-PI3K-Akt and EGFR-Erk1/2 pathways, were involved in ISO-induced cell growth inhibition and apoptosis in PCa cells, providing a more solid theoretical basis for the application of ISO to treat patients with prostate cancer in clinic.

Rigid Amino Acid as Linker to Enhance the Crystallinity of CH3NH3PbI3 Particles

Organic–inorganic hybrid perovskites have attracted extensive interest in recent years due to their remarkable properties in highly efficient solar cells. The quality of the perovskite thin films has been identified as a critical factor to affect the performances of the solar cells. To achieve uniform and dense perovskite films, many efforts have been attempted on controlling the crystallinity of the particles, grain size, as well as surface coverage. Using organic coupling agents to connect the mesoporous TiO2 with the perovskite film is an effective way to guide the growth of perovskite film. However, the influences of organic molecular configurations on the perovskite crystallization are still not being well studied. In this article, two amino acids, 4‐aminobenzoic acid and 4‐aminobutyric acid, are employed with similar molecular size and closed chain length to study the molecular rigidity of the organic coupling agents affecting the quality of perovskite films. Greatly improved perovskite film has been obtained with the template effect of rigid 4‐aminobenzoic acid and thus the cell performance has been significantly increased.

Robust macroporous polymers: Using polyurethane diacrylate as property defining crosslinker

Polymerised high internal phase emulsions (polyHIPEs) have drawn extensive interest in recent years; however, industrial applications do require polyHIPEs to be tough and robust. The mechanical properties of polyHIPEs can be tuned by copolymerisation of polyurethane diacrylate (PUDA) and styrene. The resulting open-porous poly(styrene-co-PUDA)HIPEs were much less brittle and friable when compared to conventional poly(styrene-co-divinylbenzene)HIPEs. Moreover, poly(styrene-co-PUDA)HIPEs have impact strengths up to 10 times higher than poly(styrene-co-divinylbenzene)HIPEs. The styrene/PUDA ratio determines the morphology, thermal and mechanical properties of the poly(styrene-co-PUDA) macroporous polymers. The viscous PUDA promotes the formation of small pores in polyHIPEs. A high PUDA content of the copolymer results in a dual glass transition temperature and low mechanical properties. By using an optimised St/PUDA ratio, we manufactured polyHIPEs with impact strength similar to that of commercial closed-cell polyurethane foam.

Biochar-induced changes in soil properties affected immobilization/mobilization of metals/metalloids in contaminated soils

Remediation of metal contaminated soil with biochar is attracting extensive interest in recent years. Understanding the significance of variable biochar properties and soil types helps elucidating the meticulous roles of biochar in immobilizing/mobilizing metals/metalloids in contaminated soils. Six biochars were produced from widely available agricultural wastes (i.e., soybean stover, peanut shells and pine needles) at two pyrolysis temperatures of 300 and 700 °C, respectively. The Pb-, Cu-, and Sb-contaminated shooting range soils and Pb-, Zn-, and As-contaminated agricultural soils were amended with the produced biochars. The mobility of metals/metalloids was assessed by the standard batch leaching test, principal component analysis and speciation modeling. The changes in soil properties were correlated to feedstock types and pyrolysis temperatures of biochars based on the principal component analysis. Biochars produced at 300 °C were more efficient in decreasing Pb and Cu mobility (>93 %) in alkaline shooting range soil via surface complexation with carboxyl groups and Fe-/Al-minerals of biochars as well as metal-phosphates precipitation. By contrast, biochars produced at 700 °C outperformed their counterparts in decreasing Pb and Zn mobility (100 %) in acidic agricultural soil by metal-hydroxides precipitation due to biochar-induced pH increase. However, Sb and As mobility in both soils was unfavorably increased by biochar amendment, possibly due to the enhanced electrostatic repulsion and competition with phosphate. It is noteworthy that the application of biochars is not equally effective in immobilizing metals or mobilizing metalloids in different soils. We should apply biochar to multi-metal contaminated soil with great caution and tailor biochar production for achieving desired outcome and avoiding adverse impact on soil ecosystem.

Measurement of Lateral and Interfacial Thermal Conductivity of Single- and Bilayer MoS2 and MoSe2 Using Refined Optothermal Raman Technique.

Atomically thin materials such as graphene and semiconducting transition metal dichalcogenides (TMDCs) have attracted extensive interest in recent years, motivating investigation into multiple properties. In this work, we demonstrate a refined version of the optothermal Raman technique to measure the thermal transport properties of two TMDC materials, MoS2 and MoSe2, in single-layer (1L) and bilayer (2L) forms. This new version incorporates two crucial improvements over previous implementations. First, we utilize more direct measurements of the optical absorption of the suspended samples under study and find values ∼40% lower than previously assumed. Second, by comparing the response of fully supported and suspended samples using different laser spot sizes, we are able to independently measure the interfacial thermal conductance to the substrate and the lateral thermal conductivity of the supported and suspended materials. The approach is validated by examining the response of a suspended film illuminated in different radial positions. For 1L MoS2 and MoSe2, the room-temperature thermal conductivities are 84 ± 17 and 59 ± 18 W/(m·K), respectively. For 2L MoS2 and MoSe2, we obtain values of 77 ± 25 W and 42 ± 13 W/(m·K). Crucially, the interfacial thermal conductance is found to be of order 0.1-1 MW/m(2) K, substantially smaller than previously assumed, a finding that has important implications for design and modeling of electronic devices.