A Comprehensive Contamination Investigation of Bohai Bay Seawater: Antibiotics Occurrence, Distribution, Ecological Risks and Their Interactive Factors.

A comprehensive, large-scale coastal investigation of antibiotics in seawater from Bohai Bay is lacking. Therefore, in this study, we investigated the occurrence and ecological risks of 45 antibiotics belonging to 5 classes in seawater from Bohai Bay, as well as their inter-relation with trace elements and other contaminants. The results show that tetracyclines (TCs) were detected in the highest concentration among the five classes (in the range of 0.6−2.0 µg/L). The total concentrations of the five classes of antibiotics were detected in the following order: tetracyclines (TCs) > quinolones (QAs) > sulfonamides (SAs) > macrolides (MAs) > lactams (LAs). Higher antibiotic concentrations were detected at the sampling sites closest to the coast or the shipping port. Among seven trace elements, four were quantitatively detected, with Zn representing the highest concentration. Antibiotic residuals were found to be positively correlated with total organic carbon (TOC), conductivity (Ec) and suspended solids (SS); pH and NH4+-N usually showed a negative correlation with antibiotics; TN and TP also exhibited relationships with antibiotics. The risk quotient (RQ) was calculated for different antibiotics at different sites. It was found that antibiotics pose higher risks to algae than to invertebrates or fish; sulfamethoxazole, enrofloxacin and ofloxacin were all found to pose high risk to algae at some of the sampling sites. Structural equation model (SEM) results show that trace elements, antibiotic levels and EC50 are the main factors affecting the ecological risks of antibiotics.

Commercially Viable Hybrid Li-Ion/Metal Batteries with High Energy Density Realized by Symbiotic Anode and Prelithiated Cathode.

The energy density of commercial lithium (Li) ion batteries with graphite anode is reaching the limit. It is believed that directly utilizing Li metal as anode without a host could enhance the battery's energy density to the maximum extent. However, the poor reversibility and infinite volume change of Li metal hinder the realistic implementation of Li metal in battery community. Herein, a commercially viable hybrid Li-ion/metal battery is realized by a coordinated strategy of symbiotic anode and prelithiated cathode. To be specific, a scalable template-removal method is developed to fabricate the porous graphite layer (PGL), which acts as a symbiotic host for Li ion intercalation and subsequent Li metal deposition due to the enhanced lithiophilicity and sufficient ion-conducting pathways. A continuous dissolution-deintercalation mechanism during delithiation process further ensures the elimination of dead Li. As a result, when the excess plating Li reaches 30%, the PGL could deliver an ultrahigh average Coulombic efficiency of 99.5% for 180 cycles with a capacity of 2.48 mAh cm-2 in traditional carbonate electrolyte. Meanwhile, an air-stable recrystallized lithium oxalate with high specific capacity (514.3 mAh g-1) and moderate operating potential (4.7-5.0 V) is introduced as a sacrificial cathode to compensate the initial loss and provide Li source for subsequent cycles. Based on the prelithiated cathode and initial Li-free symbiotic anode, under a practical-level 3 mAh capacity, the assembled hybrid Li-ion/metal full cell with a P/N ratio (capacity ratio of LiNi0.8Co0.1Mn0.1O2 to graphite) of 1.3 exhibits significantly improved capacity retention after 300 cycles, indicating its great potential for high-energy-density Li batteries.

In Situ Constructed Ionic-Electronic Dual-Conducting Scaffold with Reinforced Interface for High-Performance Sodium Metal Anodes.

The formation of severe dendritic sodium (Na) microstructure reduces the reversibility of anode and further hinders its practical implementation. In this work, an ionic-electronic dual-conducting (IEDC) scaffold composed of Na3 P and carbon nanotubes is in situ developed by a scalable strategy with subsequent alloying reaction, for realizing dendrite-free Na deposition under high current density and large areal capacity. The in situ formed Na3 P with high sodiophilicity not only sets up a hierarchically efficient ionic conducting network, but also participates in the construction of reinforced solid electrolyte interphase, while carbon nanotubes can assemble an electronic conducting framework. As a result, the multifunctional IEDC scaffold contributes to smooth Na plating and exceptionally reversible Na stripping. High average Coulombic efficiency of 99.8% after prolonged 1200 cycles at 3 mA cm-2 and small overpotential of 20 mV over 250 h (equals to 530 cycles) at high rate of 5 mA cm-2 are obtained. The high availability of Na in IEDC scaffold enables the impressive performance of full cell with limited Na, using Na3 V2 (PO4 )3 (NVP) cathode at practical level. More importantly, the as-developed anode-free full cell with IEDC||NVP configuration delivers a high capacity retention with long lifetime, indicating its great potential for practical Na metal batteries.

Facile Synthesis of Ant-Nest-Like Porous Duplex Copper as Deeply Cycling Host for Lithium Metal Anodes.

Suppressing the dendrite formation and managing the volume change of lithium (Li) metal anode have been global challenges in the lithium batteries community. Herein, a duplex copper (Cu) foil with an ant-nest-like network and a dense substrate is reported for an ultrastable Li metal anode. The duplex Cu is fabricated by sulfurization of thick Cu foil with a subsequent skeleton self-welding procedure. Uniform Li deposition is achieved by the 3D interconnected architecture and lithiophilic surface of self-welded Cu skeleton. The sufficient space in the porous layer enables a large areal capacity for Li and significantly improves the electrode-electrolyte interface. Simulations reveal that the structure allows proper electric field penetration into the connected tunnels. The assembled Li anodes exhibit high coulombic efficiency (97.3% over 300 cycles) and long lifespan (>880 h) at a current density of 1 mA cm-2 with a capacity of 1 mAh cm-2 . Stable and deep cycling can be maintained up to 50 times at a high capacity of 10 mAh cm-2 .

Boosting Sodium Storage in Two-Dimensional Phosphorene/Ti3C2Tx MXene Nanoarchitectures with Stable Fluorinated Interphase.

The stacking of complementary two-dimensional (2D) materials into hybrid architectures is desirable for batteries with enhanced capacity, fast charging, and long lifetime. However, the 2D heterostructures for energy storage are still underdeveloped, and some associated problems like low Coulombic efficiencies need to be tackled. Herein, we reported a phosphorene/MXene hybrid anode with an in situ formed fluorinated interphase for stable and fast sodium storage. The combination of phosphorene nanosheets with Ti3C2Tx MXene not only facilitates the migration of both electrons and sodium cations but also alleviates structural expansion of phosphorene and thereby improves the cycling performance of the hybrid anode. X-ray photoelectron spectroscopy in-depth analysis reveals that the fluorine terminated MXene stabilize the solid electrolyte interphase by forming fluorine-rich compounds on the anode surface. Density functional theory calculations confirm that the sodium affinities and diffusion kinetics are significantly enhanced in the phosphorene/MXene heterostructure, particularly in the phosphorene/Ti3C2F2. As a result, the hybrid electrode achieved a high reversible capacity of 535 mAh g-1 at 0.1 A g-1 and superior cycling performance (343 mAh g-1 after 1000 cycles at 1 A g-1 with a capacity retention of 87%) in a fluorine-free carbonate electrolyte.

Deep-Eutectic-Solvent-Based Self-Healing Polymer Electrolyte for Safe and Long-Life Lithium-Metal Batteries.

The deployment of high-energy-density lithium-metal batteries has been greatly impeded by Li dendrite growth and safety concerns originating from flammable liquid electrolytes. Herein, we report a stable quasi-solid-state Li metal battery with a deep eutectic solvent (DES)-based self-healing polymer (DSP) electrolyte. This electrolyte was fabricated in a facile manner by in situ copolymerization of 2-(3-(6-methyl-4-oxo-1,4-dihydropyrimidin-2-yl)ureido)ethyl methacrylate (UPyMA) and pentaerythritol tetraacrylate (PETEA) monomers in a DES-based electrolyte containing fluoroethylene carbonate (FEC) as an additive. The well-designed DSP electrolyte simultaneously possesses non-flammability, high ionic conductivity and electrochemical stability, and dendrite-free Li plating. When applied in Li metal batteries with a LiMn2 O4 cathode, the DSP electrolyte effectively suppressed manganese dissolution from the cathode and enabled high-capacity and a long lifespan at room and elevated temperatures.

Tunable optofluidic sorting and manipulation on micro-ring resonators from a statistics perspective.

Based on the optical trapping force of an evanescent wave at a micro-ring resonator alongside a waveguide, we propose a tunable optofluidic sorting unit for micro-nanoparticles by localized thermal phase tuning. With the tuning of field build-up factor of resonator, the depth of trapping potential well and the size of trapped particle are adjustable. Furthermore, by considering the Brownian motion of trapped particles from a statistics perspective, we verify the critical trapping threshold of a potential well, which is usually assumed to be 1kBT. The threshold depends not only on the optical power and particle size, but also on the length of the coupling region. Compared with a wavelength tuning mechanism, localized thermal tuning enables large-scale integration of many independent tunable resonators. As a demonstration, we propose a set of operations with three resonators for nanoparticle manipulation, including sorting, storing, and mixing. Our proposed function units are of great importance for on-chip large-scale integration of optofluidic systems.

Integrated optofluidic micro-pumps in micro-channels with uniform excitation of a polarization rotating beam.

We report an integrated optofluidic micro-pump with a pair of mirrored stirrers of circulating micro-beads in a micro-channel, driven by plasmon-assisted optical manipulation with the excitation of a polarization rotating beam. H-shaped apertures (HSAs) on a gold surface produce strong near-field hot spots when they are illuminated with a light beam polarized parallel to the long axis of "H." With the rotating of excitation polarization, loops of HSAs with gradually varied orientations can produce the circulation of hot spots, which can further trap micro-beads and make them go around in circles. A different sequence of HSAs can produce a different direction and phase of bead rotation, even under uniform excitation. A pair of mirrored circulations of micro-beads in a micro-channel can induce very effective directional flow. Through numerical modeling, we find that a group of non-synchronized multi-phase mirrored circulations can produce a very uniform flow rate with a speed of more than 10 micrometers per second. These micro-pumps can be heavily integrated and activated by a single beam, while the flow direction of each pump can be regulated, even under a uniform excitation. Our design proposes a new approach for the flow pumping in micro- and nanofluidic devices.

Impact of artificial reefs on sediment bacterial structure and function in Bohai Bay.

Artificial reefs have significantly altered ecological and environmental conditions compared with natural reefs, but how these changes affect sediment bacteria structure and function is unknown. Here, we compared the structure and function of the sediment bacterial community in the artificial reef area, the future artificial reef area, and the control area in Bohai Bay by 16S rRNA genes sequencing. Our results indicated that bacteria communities in the sediment were both taxonomically and functionally different between the reef area and control area. In the artificial reef area, the α-diversity was significantly lower, whereas the ß-diversity was significantly higher. Functional genes related to chemo-heterotrophy, nitrate reduction, hydrocarbon degradation, and the human pathogens and human gut were more abundant, whereas genes related to the metabolism of sulfur compounds were less abundant in the artificial reef than in the control area. The differences in bacterial communities were primarily determined by depth in the artificial reef area, and by total organic carbon in the future reef area and control area. This study provides the first overview of molecular ecology to assess the impacts of artificial reefs on the bacteria community.

Multi-level sorting of nanoparticles on multi-step optical waveguide splitter.

We propose an optofluidic sorting method for nanoparticles with different size by using optical waveguide splitter, and moreover, multiple cascaded splitters with different threshold could act as multi-level sorting unit. For a directional coupler (DC) with a specific wavelength excitation, the power splitting ratio is related to the coupling length and the gap between parallel waveguides. The power splitting ratio further determines the trapping force and potential wells distribution of both output ports. Most importantly, the potential well distribution is dependent on the particle size. For larger particles, the potential wells of both waveguides are inclined to merge, which makes it easier to be attracted and transfers to the adjacent waveguide with deeper potential well. The critical size of sorting is corresponding to the case when the barrier between wells just disappears, or the second derivative of the potential distribution is exactly zero. Moreover, since the sorting threshold of nanoparticles is related to coupling length and gap, multiple cascaded splitters with length or gap gradually varied could act as a multi-level sorting unit. A four-level sorting unit with a critical particle size of 600nm, 700nm, and 800nm are demonstrated. By considering the Brownian motion of particles and using particle-tracking method, the random distribution of nanoparticles on parallel waveguides in the sorting process is statistically presented, which agreed well with its corresponding potential wells distribution analysis. This sorting method based on multi-step optical waveguide splitter offers a number of advantages including single wavelength excitation, low loss, low power performance and ease of fabrication. This design can realize the high-throughput and large-scale nanoparticle automatic sorting in integrated photonic circuits, which have great potential for a large scale lab-on-a-chip system.

A room-temperature sodium-sulfur battery with high capacity and stable cycling performance.

High-temperature sodium-sulfur batteries operating at 300-350 °C have been commercially applied for large-scale energy storage and conversion. However, the safety concerns greatly inhibit their widespread adoption. Herein, we report a room-temperature sodium-sulfur battery with high electrochemical performances and enhanced safety by employing a "cocktail optimized" electrolyte system, containing propylene carbonate and fluoroethylene carbonate as co-solvents, highly concentrated sodium salt, and indium triiodide as an additive. As verified by first-principle calculation and experimental characterization, the fluoroethylene carbonate solvent and high salt concentration not only dramatically reduce the solubility of sodium polysulfides, but also construct a robust solid-electrolyte interface on the sodium anode upon cycling. Indium triiodide as redox mediator simultaneously increases the kinetic transformation of sodium sulfide on the cathode and forms a passivating indium layer on the anode to prevent it from polysulfide corrosion. The as-developed sodium-sulfur batteries deliver high capacity and long cycling stability.

Controllable trapping and releasing of nanoparticles by a standing wave on optical waveguides.

Based on the balance between the scattering force and the trapping force of an evanescent field of a standing wave on silicon waveguides, we propose a structure for controllable trapping and releasing of nanoparticles, which can act as pause operation for nanoparticle flow control. The design is realized by the cascade of an optical switch with a structure of a ring-assisted Mach-Zehnder interferometer (RAMZI) and a Sagnac loop reflector which connects to one output of the switch. Through thermal tuning, with a tiny refractive index change of 4.3×10-4 on a ring resonator, the output of a RAMZI can be switched between two ports. As for the release state of the nanoparticle flow, the light is guided to the port without a reflector. There is no standing wave or traps formed on a waveguide. Therefore, the scattering force dominates, which drives particles moving forward to output ports. Otherwise, for trapping a state, the light will be reflected by the Sagnac loop and form a stationary standing wave which provides an array of traps for nanoparticles. Most importantly, the structure can switch its state to trap or sequentially release particles without losing the control of samples which, to the best of our knowledge, has not been realized before. With the statistical description of particle motion, the balance between trapping and releasing is distinguished by the trapping time and tuned by reflectance. The feasibility of our design is verified using the three-dimensional finite-difference time domain and Maxwell stress tensor methods. Our structure possesses the merits of high compactness and time effectiveness and, thereby, it is highly suitable for on-chip optical manipulation of nanoparticle flow control, which brings great potential in integrated on-chip optofluidics.

Electrospun N-Doped Hierarchical Porous Carbon Nanofiber with Improved Degree of Graphitization for High-Performance Lithium Ion Capacitor.

The lithium-ion capacitor (LIC) has been regarded as a promising device that combines the merits of lithium-ion batteries and supercapacitors, and that meets the requirements for both high energy and high power density. The development of advanced electrode materials is the key requirement. Herein, we report the bottom-up synthesis of activated carbon nanofiber (a-PANF) with a hierarchical porous structure and a high degree of graphitization. Electrospinning has been employed to prepare an interconnected fiber network with macropores, and ferric acetylacetonate has been introduced as both a mesopore-creating agent and a graphitic catalyst to increase the degree of graphitization. Furthermore, chemical activation enlarges the specific surface area by producing abundant micropores. Half-cell evaluation of the as-prepared a-PANF gave a discharge capacity of 80 mA h g-1 at 0.1 A g-1 within 2-4.5 V and no capacity fading after 1000 cycles at 2 A g-1 , which represents a significant improvement compared to conventional activated carbon (AC). Furthermore, an as-assembled LIC with a-PANF cathode and Fe3 O4 anode showed a superior energy density of 124.6 W h kg-1 at a specific power of 93.8 W kg-1 , which remained at 103.7 W h kg-1 at 4687.5 W kg-1 . This indicates promising application potential of a-PANF as an electrode material for efficient energy storage systems.

Radial distributions of temperature pressure and velocities for pulsatile blood flow in an axisymmetrical stiff tube.

Using perturbation theory with the assumption that the pulsatile blood flow in an axisymmetrical stiff tube is the first-order term to solve the linear equations of continuity, motion and heat conduction, the equations of the pulsatile flow, including temperature, are derived, and the instantaneous radial distribution of temperature, pressure and velocities for one frequency component are obtained. Using the published geometrical and physiological parameters of a large artery, a numerical analysis of the distribution relationship between the axial velocity and temperature is carried out. The primary studies show that the amplitude of temperature fluctuation in the tube is inversely proportional to the pulsatile frequency, the temperature and velocities gradients are mainly restricted in the near-wall layers with the increase of pulsatile frequency, and there is a close similarity of the radial pulsating distribution between temperature and axial velocity, which indicates that the blood flux in the artery as well as the motion function of heart can be indirectly described by the measurement of temperature fluctuation.