Self-assembled PtNi layered metallene nanobowls for pH-universal electrocatalytic hydrogen evolution

Compared with layered materials such as graphite and transition metal disulfide compounds with highly anisotropic in-plane covalent bonds, it is inherently more challenging to obtain independent metallic two-dimensional films with atomic thickness. In this study, PtNi layered metallene nanobowls (LMBs) with multilayer atomic-scale nanosheets and bowl-like structures have been synthesized in one step using structural and electronic effects. The material has the advantage of catalyzing pH-universal hydrogen evolution reaction (HER). Compared with Pt/C, PtNi LMBs exhibited excellent HER activity and stability under all pH conditions. The overpotentials of 10 mA cm-2 at 0.5 M H2SO4, 1.0 M phosphate buffer and 1.0 M KOH were 14.8, 20.3, and 34.0 mV, respectively. Under acidic, neutral and alkaline conditions, the HER Faraday efficiencies reach 98.97%, 98.85%, and 99.04%, respectively. This study provides an example for the preparation of unique multilayer nanobowls, and also provides a basic research platform for the development of special HER materials.

Multilayer structure covalent organic frameworks (COFs) linking by double functional groups for advanced K+ batteries

Covalent organic frameworks (COFs) are regarded as the potential and promising anode materials for potassium ion batteries (PIBs) on account of their robust and porous crystalline structure. In this work, multilayer structural COF connected by double functional groups, including imine and amidogent through a simple solvothermalprocess, have been successfully synthesized. The multilayer structure of COF can provide fast charge transfer and combine the merits of imine (the restraint of irreversible dissolution) and amidogent (the supply of more active sites). It presents superior potassium storage performance, including the high reversible capacity of 229.5 mAh g^-1 at 0.2 A g^-1 and outstanding cycling stability of 106.1 mAh g^-1 at the high current density of 5.0 A g^-1 after 2000 cycles, which is superior to the individual COF. The structural advantages of the covalent organic framework linking by double functional groups (d-COF) can develop a new road for that COF anode material for PIBs in further research.

Efficient carbon removal and excellent anti-clogging performance have been achieved in multilayer quartz sand horizontal subsurface flow constructed wetland for domestic sewage treatment

The present study aimed to investigate the application of a multilayer quartz sand substrate horizontal subsurface flow constructed wetland (HSFCW) for campus sewage treatment. It aimed to assess the pollutant removal efficiency and anti-clogging performance under the suggested maximum organic loading rate (250 g/m²/d). The results of the multilayer HSFCW (CW6) were compared to the mololayer HSFCW (CW1) for the removal of the chemical oxygen demand (COD), solid accumulation, and microbial communities. During operation, the combination conditions of high hydraulic loading rate (HLR) with low COD concentration were better for COD removal under a high organic loading rate (OLR) of 200-300 g/m²/d. The maximum removal rate reached 80.4% in CW6 under high HLR, which was 13.8% higher than that in CW1, showing better adsorption and biodegradation ability of organic matter. Impressive clogging resistance capacity was found in CW6 due to the lower contents of the insoluble organic matter (IOM) that are prone to clogging, indicating full degradation of organic matters, particularly IOM, in CW6 under high HLR. Less abundance of unclassified Chitinophagaceae (under low HLR), Pedobacter and Saccharibacteria_genera_incertae_sedis (under high HLR) in CW6, which contributed to aerobic membrane fouling, helped to prevent clogging. Moreover, Brevundimonas, Cloacibacterium, Citrobacter, Luteimonas contributed to IOM degradation, thus further enhancing the anti-clogging performance. In view of the better clogging resistance performance, the application of CW6 operated under high HLR and low COD concentrations was recommended to achieve economical, efficient, and steady COD removal for domestic sewage treatment in long-term operation.

Multilevel structured PASS nanofiber filter with outstanding thermal stability and excellent mechanical property for high-efficiency particulate matter removal

Particulate matter (PM) pollution from industrialization poses a great threat to people's health. Although fiber-based filters are used effectively to capture PM, the traditional filters with large diameter suffer from low filtration efficiency, high pressure drop and low temperature resistance. In this study, multilayer poly arylene sulfide sulfone (M-PASS) composite filter was designed and fabricated via electrospinning technology. The M-PASS composite filter is sandwich-structure. Due to the unique structure and composition, the M-PASS filter exhibited outstanding removal efficiency of 99.97 ± 0.0050%, extremely low air resistance of 44.3 ± 0.7 Pa, excellent quality factor (QF) of 0.19 ± 0.0019 Pa^-1, and desirable mechanical strength of 7.0 ± 0.2 MPa. Furthermore, the as-prepared M-PASS filter can remain outstanding filtration performance at 200.0 ℃ due to the high thermal stability of PASS and the removal efficiency was still above 95.2 ± 0.4% after long-term filtration test. These results demonstrate that the structure of filter is the important one for air filtration and the M-PASS nanofiber filters have great potential in PM removal, especially under high temperature conditions.

Ultrasonic autofocus imaging of internal voids in multilayer polymer composite structures

Multilayer polymer composite structures have been playing important roles in various fields, but the voids inside are not allowed in most scenarios. Ultrasonic technology has been widely used to inspect voids in concrete and metal structures. However, the application of ultrasonic imaging in polymer composite structures is severely blocked by the coating and lamination structures and unstable manufacturing induced sound speed variations. In this paper, a method to autofocus imaging of internal voids in multilayer polymer composite structures with ultrasonic phased array is firstly proposed. The method processes the full matrix capture (FMC) and focuses all voids in the multilayer structure automatically without the prior information of the speed of sound (SOS). The method utilizes the focus criterions to evaluate the focusing quality and then estimates the SOS with differential evolution layer by layer from surface to deep, which improves the robustness and computational efficiency. The method was examined with simulation data from three multilayer structures and well-focused all voids with position error less than 0.6 mm and SOS error less than 6 %. Moreover, the method was verified with the experimental data and focused voids with position error less than 1 mm.

Efficient removal of diclofenac from surface water by the functionalized multilayer magnetic adsorbent: Kinetics and mechanism

Developing robust and effective adsorbent for removing ubiquitous pharmaceutical diclofenac (DCF) from the aquatic environment is vitally important for environmental safety. Hence, a novel chitosan-based multilayer adsorbent (FCS-PD) with magnetic separation ability and surface functionality was successfully assembled, which had countless potential for removing contaminants from water. A series of instrumental technologies were performed to demonstrate the physicochemical properties of FCS-PD. Its adsorption performance toward DCF removal was comprehensively evaluated in synthetic water and surface water. The effects of microplastics, inorganic ions and humic acid on the adsorption were investigated. The maximum adsorption capacity of FCS-PD was calculated as 434.78 mg/g under neutral conditions, exhibiting superior adsorption performance than most reported adsorbents. The DCF in surface water was practically removed at low concentration (50 μg/L). FCS-PD presented a multistage kinetics controlled by chemisorption and intraparticle diffusion, which was emphasized by the pseudo-second-order kinetic and intra-particle diffusion analysis. After five cycles of adsorption and regeneration, the adsorption capacity only decreased by 9.9%, indicating the satisfactory regeneration of FCS-PD. The analysis of high-resolution X-ray photoelectron spectroscopic (XPS) and Fourier transform infrared spectroscopy (FTIR) revealed that the quaternary ammonium groups on the outer layer and the amino and hydroxyl groups on the chitosan layer are involved in the capture of DCF under electrostatic force and hydrogen bonding.

Green preparation of polyvinylidene fluoride loose nanofiltration hollow fiber membranes with multilayer structure for treating textile wastewater

In this work, polyvinylidene fluoride (PVDF) loose nanofiltration (NF) hollow fiber membranes with multilayer structure were prepared successfully based on a solvent-free process. Graphene oxide (GO) was used to cover the interface pores of the pristine PVDF membranes via vacuum filtration, and polypyrrole (PPy) was polymerized on the surface to further decorate the membrane structure. Interestingly, the modified membranes exhibited a multilayer structure due to synergistic effect of GO and PPy. The structure and property of PVDF loose NF membranes were investigated in detail. After modifying by GO and PPy, the hydrophilicity improved obviously. Moreover, the molecular weight cut off (MWCO) was about 3580 Da, and the smallest pore size of skin layer decreased to 2.5-4 nm. Furthermore, the PVDF loose NF hollow fiber membranes presented a high dye rejection (˃98.5%) for negative dyes, whereas a low salt rejection for NaCl (about 4%), showing a great potential for separating dye/salt accurately. Specifically, there were not any solvent used in all the preparation processes. The work offered a novel strategy for green preparation of loose NF membranes.

Long-term results of triple-layered small diameter vascular grafts in sheep carotid arteries

There is an urgent clinical for small diameter vascular grafts (SDVGs) for use in the treatment of coronary artery disease. Moreover, biodegradable SDVGs are drawing increasing attention because they have the potential to restore vascular function with the degradation of vascular graft and tissue regeneration. In this study, we designed triple-layered SDVGs to mimic the native arterial structure, with each layer contributing its unique porosity to the porous structure. We evaluated triple-layered SDVGs in a sheep carotid arterial replacement model. After implantation for 12 months, two grafts were patent and indicated the feasibility of using grafts in large animals. Nevertheless, it was determined that both grafts formed aneurysms at the proximal end. The prevention of such aneurysms remains a challenge for future investigation.

SEM-EDX linear scanning: a new tool for morpho-compositional analysis of growth bands in urinary stones

The genesis and growth of calculi are imprinted in their structure, so the pathogenesis of lithiasis could potentially be read via proper analytical techniques. In this study, electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) is used to obtain a description of the morphology and compositional structure of a single bladder stone. This technique establishes the chemical and crystalline architecture of the urolith to assess the effect of the chemical environment on its growth. Scanning electron microscopy-backscattered electrons (SEM-BSE) images clearly show that the stone has a multilayered structure. These layers and Liesegang ring-like structures are characterized by one predominant chemical component but also by slighter compositional changes. The mean crystalline components are determined by X-ray diffraction (DRX), infrared spectroscopy (FT-IR), and Raman analysis (RMN). Elemental analysis along a radial trajectory of the calculus by EDX linear scanning (EDX-LS) also reveals the compositional structure of the layers and the spatial distribution of the main chemical components. EDX-LS data processing reveals concentration profiles that clearly show morpho-compositional growth bands, which correspond to precipitation waves and urinary concentration peaks. The width of the growth bands is independent of the radial position, layer, and element analyzed. We conclude that the bands observed are a consequence of slight changes in the biochemical composition of the urine and consequently reflect a short-term biological cycle of the renal system. This non-specific growth rate suggests that stone formation is a kinetically controlled phenomenon in which promoters of crystal cluster aggregation may have played a key role.

Improving thermal and electrical stability of silver nanowire network electrodes through integrating graphene oxide intermediate layers

Silver nanowire (Ag NW)-based flexible and transparent electrodes are a promising candidate for various electronic and optoelectronic applications. However, thermal and electrical instabilities of Ag NW networks during operation and post treatments need to be improved for practical applications. In this work, Ag NW/Graphene Oxide (GO) hybrid films with a multilayer structure were developed, in which transparent GO sheets were inserted between Ag NWs. For the pristine Ag NW networks, contacted NWs exhibited poorer thermal stability than individual NWs as faster Ag diffusion between NWs led to the breakage of the junctions at working temperatures, hence leading to the overall device failure. In contrast, the GO intermediate layers hindered the Ag diffusion between NWs in the Ag NW/Graphene Oxide hybrid films and maintained the junction structure, giving rise to enhanced thermal stability compared to the pristine networks and the GO-covered samples. For electrical tests, unlike the network degradation under annealing treatments, a local deterioration perpendicular to the current flow was directly observed after electrical breakdown, which was attributed to high local temperature under large applied voltage. The electrical failure of the devices was related to the network structure and defects. Furthermore, the pristine devices showed notable variation of failure voltage, which in the hybrid devices is more uniform and improved in general.

Ultrafast synthesis of Au(I)-dodecanethiolate nanotubes for advanced Hg(2+) sensor electrodes

In this work, an ultrafast and facile method is developed to synthesize Au(I)-dodecanethiolate nanotubes (Au(I)NTs) with the assistance of glycyl-glycyl-glycine (G-G-G). Transmission electron microscopy (TEM) images reveal that the as-prepared Au(I)NTs can be obtained in a 2-h reaction instead of a previous 24-h reaction and are uniform with a hollow structure and smooth surface by virtue of the G-G-G peptide tubular template. According to structural analysis, a possible preparative mechanism is proposed that the G-G-G peptide could help to curl into tube-like morphology in alkaline situation spontaneously to accelerate the formation of Au(I)NTs. Meanwhile, PVDF-stabilized Au(I)NT-modified glassy carbon electrodes present their promising potential for Hg(2+) detection.