Discrimination and simultaneous quantification of poly(ethylene terephthalate) and poly(butylene terephthalate) microplastics in environmental samples via gas chromatography-tandem mass spectrometry.

A method has been developed to quantify PET and PBT microplastics (MPs) based on depolymerization and detection of depolymerization products by gas chromatography-tandem mass spectrometry (GC-MS/MS) without a complex separation process from environmental samples. Under the optimal depolymerization conditions, PET and PBT were efficiently converted to ethylene glycol (78%) and 1,4-butanediol (87%), respectively. Subsequently, the linear curves were constructed between signal intensities of depolymerization products and polymer masses by GC-MS/MS, and the correlation coefficients of PET and PBT were 0.996 and 0.997, respectively. The spiking and recovery experiments of PET and PBT in the environmental samples showed that the recovery was stable in the range 89-100%, and the limit of detection was 4.95 µg and 1.39 µg of PET and PBT, respectively. The method has been proven to be capable of simultaneous identification and quantification of PBT and PET MPs in real environmental water samples without complex separation process, which provided a scheme for the determination of microplastics.

Insights into the aspect ratio effects of ordered mesoporous carbon on the electrochemical performance of sulfur cathode in lithium-sulfur batteries.

Tailoring porous host materials, as an effective strategy for storing sulfur and restraining the shuttling of soluble polysulfides in electrolyte, is crucial in the design of high-performance lithium-sulfur (Li-S) batteries. However, for the widely studied conductive hosts such as mesoporous carbon, how the aspect ratio affects the confining ability to polysulfides, ion diffusion as well as the performances of Li-S batteries has been rarely studied. Herein, ordered mesoporous carbon (OMC) is chosen as a proof-of-concept prototype of sulfur host, and its aspect ratio is tuned from over âˆ¼ 2 down to below âˆ¼ 1.2 by using ordered mesoporous silica hard templates with variable length/width scales. The correlation between the aspect ratio of OMCs and the electrochemical performances of the corresponding sulfur-carbon cathodes are systematically studied with combined electrochemical measurements and microscopic characterizations. Moreover, the evolution of sulfur species in OMCs at different discharge states is scrutinized by small-angle X-ray scattering. This study gives insight into the aspect ratio effects of mesoporous host on battery performances of sulfur cathodes, providing guidelines for designing porous host materials for high-energy sulfur cathodes.

Simultaneous detection of As(III/V), Cr(III/VI), and Fe(II/III) by a sensor array based on the morphology regulation of CeO2 oxidase.

To develop a convenient method for simultaneous detection of As(III/V), Cr(III/VI), and Fe(II/III), three morphologies of CeO2 oxidase have been prepared. Based on the difference in oxidase activity and binding ability with substrate TMB of CeO2 of different morphologies, a 3 (Signal unit) × 6 (Target number) × 5 (Repetition) sensor array was constructed to realize simultaneous detection of six variable valence metal ions As(III/V), Cr(III/VI), and Fe(II/III). The lowest detection limit of the array for metal ions was 1.68 µg/L. The analysis of environmental samples with multiple metal ions (binary and ternary mixtures) co-existing has confirmed that the sensor array can achieve simultaneous qualitative and quantitative results for composite samples. This study not only revealed the influencing factors of crystal morphology regulation on oxidase activity, but also provided a scheme for the morphology detection of easily convertible metal ions in the field through the construction of the sensor array.

Enhancement of the Peroxidase Activity of g-C3N4 with Different Morphologies for Simultaneous Detection of Multiple Antibiotics.

The classes and forms of antibiotics directly determine their ecotoxicity and environmental chemical behavior, and developing a sensor array for simultaneous and in situ detection of antibiotics is highly anticipated. In this study, different morphologies of g-C3N4 with different fluorescence properties and peroxidase activity were prepared by regulating the degree of interlayer stacking and planar connectivity. Subsequently, in order to enhance its enzyme activity and amplify the differences in response signals to different antibiotics, three morphologies of g-C3N4/MIL-101(Fe) were prepared by in situ growth of equivalent amounts of MIL-101(Fe) on g-C3N4, respectively. The sensor array constructed based on the cross-response signals between g-C3N4/MIL-101(Fe) and antibiotics not only realized the simultaneous detection of quinolones, furans, tetracyclines, and lincomamides but also could efficiently identify their seven different forms. In the range of 0.2-0.8 ppm, the minimum detection limit for antibiotics was 12 ppb. In addition, the recovery experiments of multicomponent-mixed antibiotics in environmental samples show that the recovery rate remained at 91.42-107.59%, confirming the reliability and practicality of the sensor array. This study not only revealed the influence of crystal morphology regulation on the optical properties and enzyme activities of nanozymes, but also provided support for tracing, ecological remediation, and in situ environmental chemical behavior research of antibiotics.

Simultaneous visual detection of multiple heavy metal ions by a high-throughput fluorescent probe.

To develop simultaneous and in-situ detection techniques towards Cr(VI) and Mn(II), Eu/Tb@CDs with white fluorescence were prepared by a one-step hydrothermal method. With the increase of Cr(VI), all fluorescence channels of Eu/Tb@CDs exhibited obvious quenching, and the detection limit (LOD) was 0.10 µM. In the presence of Mn(II), only the fluorescence from Tb and Eu was quenched, while the fluorescence of CDs was not effected. The LOD for Mn(II) was 0.16 µM. More importantly, in the actual water samples where Cr(VI) and Mn(II) coexist, Eu/Tb@CDs can realize their rapid and simultaneous detection by simple spectral calculation. The selective and competitive experiments have also confirmed that the detection of Cr(VI) and Mn(II) was not interfered by common pollutants in groundwater. It is undeniable that the simultaneous detection of multiple targets by one probe not only greatly improves the detection efficiency, but also has important significance for the field monitoring of water quality parameters.

A portable and intelligent logic detector for simultaneous and in-situ detection of Al3+ and fluoride in groundwater.

To develop a convenient and intelligent detector for simultaneous and in-situ detection of Al3+ and F- in groundwater, a novel organic probe called RBP has been prepared. With the increase of Al3+, RBP showed a significant fluorescence enhancement at 588 nm, and the detection limit was 0.130 mg/L. After combining with fluorescent internal standard CDs, the fluorescence of RBP-Al-CDs at 588 nm was quenched due to the replace of F- for Al3+, while the CDs at 460 nm remained unchanged, and the detection limit was 0.0186 mg/L. For convenient and intelligent detection, an RBP-based logic detector has been developed for simultaneous detection of Al3+ and F-. Within the ultra-trace, low concentration, and high concentration range of Al3+ and F-, the logic detector can achieve rapid feedback on their concentration levels ("U", "L" and "H") through different output modes of the signal lamps. The development of logical detector is of great significance for studying the in-situ chemical behavior of Al3+ and F- and for daily household detection.

Fabric-like Electrospun PVAc-Graphene Nanofiber Webs as Wearable and Degradable Piezocapacitive Sensors.

Flexible piezocapacitive sensors utilizing nanomaterial-polymer composite-based nanofibrous membranes offer an attractive alternative to more traditional piezoelectric and piezoresistive wearable sensors owing to their ultralow powered nature, fast response, low hysteresis, and insensitivity to temperature change. In this work, we propose a facile method of fabricating electrospun graphene-dispersed PVAc nanofibrous membrane-based piezocapacitive sensors for applications in IoT-enabled wearables and human physiological function monitoring. A series of electrical and material characterization experiments were conducted on both the pristine and graphene-dispersed PVAc nanofibers to understand the effect of graphene addition on nanofiber morphology, dielectric response, and pressure sensing performance. Dynamic uniaxial pressure sensing performance evaluation tests were conducted on the pristine and graphene-loaded PVAc nanofibrous membrane-based sensors for understanding the effect of two-dimensional (2D) nanofiller addition on pressure sensing performance. A marked increase in the dielectric constant and pressure sensing performance was observed for graphene-loaded spin coated membrane and nanofiber webs respectively, and subsequently the micro dipole formation model was invoked to explain the nanofiller-induced dielectric constant enhancement. The robustness and reliability of the sensor have been underscored by conducting accelerated lifetime assessment experiments entailing at least 3000 cycles of periodic tactile force loading. A series of tests involving human physiological parameter monitoring were conducted to underscore the applicability of the proposed sensor for IoT-enabled personalized health care, soft robotics, and next-generation prosthetic devices. Finally, the easy degradability of the sensing elements is demonstrated to emphasize their suitability for transient electronics applications.

Boric Acid Functional Fluorescent Covalent-Organic Framework for Sensitive and Selective Visualization of CH3Hg.

Methylmercury (CH3Hg+) recognition remains a challenging and imperative task due to its high toxicity and wide existence in the ecosystem. Herein, a novel fluorescent covalent-organic framework containing a boric acid functional group (COF-BA) was prepared by a postmodification strategy for CH3Hg+ detection. COF-BA served as a sensing platform for CH3Hg+ with fluorescence static quenching accompanied by fluorescence color changing from intense blue to colorless, and the detection limit was determined as 1.68 µM in a relatively narrow concentration range. COF-BA also exhibited superior selectivity toward CH3Hg+ detection. Furthermore, the spiked and recovery test in real water samples showed its efficient detection practicality. The detection mechanism of COF-BA toward CH3Hg+ was investigated. The recognitive boric acid group in COF-BA was first replaced by CH3Hg+. Then, the quinoline structure that served to limit the rotation of the imine bond was disrupted, leading to dramatic fluorescence quenching. The boric acid functional COF fluorescent probe can be a promising sensing platform for the detection of methylmercury and also provides new ideas for the construction of new fluorescent COF materials.

Kármán Vortex Street Driven Membrane Triboelectric Nanogenerator for Enhanced Ultra-Low Speed Wind Energy Harvesting and Active Gas Flow Sensing.

Wind energy harvesting and sensing have a huge prospect in constructing self-powered sensor nodes, but the energy transducing efficiency at low and ultra-low wind speeds is still limited. Herein, we proposed a Kármán vortex street driven membrane triboelectric nanogenerator (KVSM-TENG) for ultra-low speed wind energy harvesting and flow sensing. By introducing Kármán vortex in the KVSM-TENG, the cut-in wind speed of the KVSM-TENG decreased from 1 to 0.52 m/s that is the lowest cut-in wind speed in current TENGs. The instantaneous output density of the KVSM-TENG significantly increased by 1000 times and 2.65 times at the inlet wind speeds of 1 and 2 m/s, respectively. In addition, with the excellent energy transducing performance at the ultra-low speed range, the KVSM-TENG was successfully demonstrated to detect a weak leakage of gas pipeline (∼0.6 m/s) for alarming with high sensitivity. The interaction mechanism between the vortex and KVSM-TENG was systematically investigated. Through the simulation and experimental validation, the enhancement mechanism of vortex dependence on the cylinder diameter and placement location of KVSM-TENG was investigated in detail. The influence of parameters such as membrane length, width, thickness, and electrode gap on the performance of the KVSM-TENG was systematically studied. This work not only provided an ingenious strategy for ultra-low speed wind energy harvesting but also demonstrates the promising prospects for monitoring the air flow in the natural gas exploitation and transportation.

Broad-spectrum pesticide screening by multiple cholinesterases and thiocholine sensors assembled high-throughput optical array system.

Accurate screening of organophosphorus and carbamates pesticides from the complex real sample is crucial for water quality analysis and food safety control. Herein, a simple, low-cost and accurate pesticides screening method based on a high-throughput optical array system assembled by multiple cholinesterases (ChE) and thiocholine (TCh) sensors is described. The detection mechanism is that the inhibition of ChE activity by pesticides reduces the TCh produced by the hydrolysis of butyryl/acetylthiocholine iodide, thus changing the fluorescence intensity of TCh sensor. The diverse response of ChEs to pesticides and different affinity of sensors to TCh ensure the high-throughput and distinguishable signal output, which allow the establishment of high discrete pesticide database with intra-cluster agglomeration and inter-cluster dispersion. By using the database, the screening of unknown real contaminated samples were successfully operated, and the screened pesticide species and concentrations were consistent with high-performance liquid chromatography. This screening strategy demonstrates the feasibility of replacing existing complex mass spectrometry-based screening strategy with simple optical analysis, providing a new idea for the development of simple accurate screening technologies for widespread organic pollutants including pesticides.

A versatile logic detector and fluorescent film based on Eu-based MOF for swift detection of formaldehyde in solutions and gas phase.

Due to the huge threat of formaldehyde (FA) on human beings, the development of chemical sensors for swift detection of FA in solutions and gas phase is highly anticipated. In this paper, a versatile logic detector and a portable fluorescent film based on small-scaled Eu-based MOF were applied successfully to detect FA in solutions and gas phase, respectively. For FA in aqueous solution, the design of logic detector will efficiently identify FA in different concentration ranges: when the FA concentration are 0-500 ppb, 500-1000 ppb and >1000 ppb, the output signals of logic detector are the concentration level of FA ("L", "H" and "VH"), and accompanied by red, purple and blue signal lamps to remind, respectively. For FA in the air, the color of rigid film sensor will gradually change from red to blue with the increase of FA under UV lamp, and the detection limit of gaseous FA is 11.8 ppb. Through the preparation of logic devices and fluorescent films, Eu-based MOF realized swift detection of FA in solutions and gas phase, which will be very helpful to improve the human response level to FA from different emission sources.

Surface acidity and basicity of Mg/Al hydrotalcite for 2, 4-dichlorophenoxyacetic acid degradation with ozone: Mineralization, mechanism, and implications to practical water treatment.

The Mg/Al hydrotalcite (Mg/Al HT) was firstly used as a heterogeneous ozonation catalyst and 2,4-dichlorophenoxyacetic acid (2,4-D) was efficiently degraded by Mg3/Al HT with a COD removal of 68 %. It was higher than that of α-FeOOH with a COD removal of 50 %. The effects of Mg/Al atomic ratio, phosphate and pyrrole on the ozonation performance of Mg/Al HTs were also investigated. The X-ray photoelectron spectroscopy (XPS), nitrogen adsorption-desorption experiment and temperature programmed desorption of adsorbed CO2 or NH3 were used to characterize the surface properties of Mg/Al HT. The surface acidity and basity was proven to be responsible to the excellent ozonation activity of Mg/Al HT. The results of electron spin resonance (ESR) analysis and probe experiments confirmed that OH, O2- and 1O2 were involved in the 2,4-D degradation process and their contributions are as followed: OH > O2- > 1O2. The synergistic effect of surface acid (ozone adsorption center) and base sites (catalytic center) determines Mg/Al HT in the enhanced catalytic ozone decomposition into reactive species. More important, the transition metal free based Mg/Al HTs is steady, non-toxic, naturally abundant and environment friendly, which provided a promising alternative in practical water treatment by catalytic ozonation.

More reactive oxygen species generation facilitated by highly dispersed bimodal gold nanoparticle on the surface of Bi2WO6 for enhanced photocatalytic degradation of ofloxacin in water.

An essential strategy to eliminate emerging contamination in water is to initiate more reactive oxygen species (ROS) in the catalytic systems. 0.14 wt.% Au loaded Bi2WO6 (Bi2WO6/Au-400 °C) was fabricated after 400 °C annealing with the assistance of glutathione for Au atom anchoring and stabilization on Bi2WO6 surface. Bimodal Au size distribution of highly dispersed small size clusters (0.5 ± 0.1 nm) and large size nanoparticles (6.3 ± 1.0 nm) simultaneously existed on Bi2WO6 nanosheets in Bi2WO6/Au-400 °C, which were verified through high resolution transmission electron microscopy (HR-TEM). 95% of ofloxacin (OFX) was degraded over Bi2WO6/Au-400 °C in 180 min under visible light irradiation with a reaction constant of 24.5 × 10-3 min-1, which showed 3.0 and 2.5-fold enhancement compared with bare Bi2WO6 and unimodal Bi2WO6/Au-500 °C (annealed at 500 °C, Au NPs (8.6 ± 1.0 nm)), respectively. The enhanced catalytic activity originated from the additional ROS production that initiated by photo-induced electron transported from small Au clusters to large Au NPs through the conduction band of Bi2WO6. Moreover, it still maintained a good stability after five cycling performance and the total cost of 10 g Bi2WO6/Au-400 °C was estimated to be 6.78 $. Lower-content of bimodal Au NPs decorated Bi2WO6 catalyst possesses high efficiency to degrade pollutant and lower cost, which provides a promising alternative in practical environmental remediation by photocatalysis.

Windbreak and airflow performance of different synthetic shrub designs based on wind tunnel experiments.

Wind erosion has gained increasing attention as one of the most serious global ecological and environmental threats. Windbreaks are effective at decreasing wind erosion by reducing wind speed to protect crops, livestock, and farmsteads, while providing wildlife habitats. Synthetic shrubs can act as novel windbreaks; however, there is limited knowledge on how their design affects wind speed. This study determined the protective effects (airflow field and sheltering efficiency) based on the design of synthetic shrubs in a wind tunnel. Broom-shaped synthetic shrubs weakened the wind speeds mainly at the middle and upper parts of the shrubs (5-14 cm), while for hemisphere-shaped shrubs this effect was greatest near their bases (below 4 cm) and least in the middle and upper parts (7-14 cm). Spindle-shaped synthetic shrubs provided the best reduction effect in wind range and strength. Moreover, the wind speed reduction ratio decreased with improved wind speeds and ranged from 26.25 cm (between the second and third rows) to 52.5 cm (after the third row). These results provide strong evidence that synthetic shrubs should be considered to decrease wind speed and prevent wind erosion.

Carbon dots-MnO2 nanocomposites for As(III) detection in groundwater with high sensitivity and selectivity.

As(iii) pollution has caused increasing concern due to its significant impact in environmental safety and human health. Carbon dots (CDs)-MnO2 nanocomposites were prepared and characterized for As(iii) detection. The intense blue fluorescence of CDs can be greatly quenched by functionalization with MnO2 nanosheets due to the existence of the fluorescence resonance energy transfer (FRET) effect. CDs-MnO2 nanocomposites were then used as a fluorescence sensor for As(iii) detection with high detection sensitivity and selectivity. The redox reaction between As(iii) and MnO2 nanosheets can induce the decomposition of MnO2 and termination of the FRET process. Then the blue fluorescence originating from CDs can be recovered. The detection limit of CDs-MnO2 nanocomposites toward As(iii) was calculated to be 16.8 nM (1.40 ppb) in a linear concentration range of 0-200 nM. CDs-MnO2 nanocomposites were also found to possess highly selective ability toward As(iii) detection. In addition, the spiked and recovery test also confirmed the practicality and reliability of CDs-MnO2 nanocomposites toward As(iii) detection in real water samples, such as groundwater etc. Our research has provided a reliable tool and strategy for visual detection of As(iii) with outstanding sensing ability.

Portable smartphone-integrated paper sensors for fluorescence detection of As(III) in groundwater.

Arsenic contamination in groundwater is a supreme environmental problem, and levels of this toxic metalloid must be strictly monitored by a portable, sensitive and selective analytical device. Herein, a new system of smartphone-integrated paper sensors with Cu nanoclusters was established for the effective detection of As(III) in groundwater. For the integration system, the fluorescence emissive peak of Cu nanoclusters at 600 nm decreased gradually with increasing As(III) addition. Meanwhile, the fluorescence colour also changed from orange to colourless, and the detection limit was determined as 2.93 nM (0.22 ppb) in a wide detection range. The interfering ions also cannot influence the detection selectivity of As(III). Furthermore, the portable paper sensors based on Cu nanoclusters were fabricated for visual detection of As(III) in groundwater. The quantitative determination of As(III) in natural groundwater has also been accomplished with the aid of a common smartphone. Our work has provided a portable and on-site detection technique toward As(III) in groundwater with high sensitivity and selectivity.

Novel Colorimetric Method for Simultaneous Detection and Identification of Multimetal Ions in Water: Sensitivity, Selectivity, and Recognition Mechanism.

Accurate recognition and speciation analysis of heavy-metal ions in complex hydrological environments is always a serious challenge. In this work, we proposed a small-molecule-based ultrasensitive colorimetric detection strategy and successfully applied it to the accurate detection of Fe2+, Fe3+, Co2+, and Hg2+ in groundwater through the specific recognition of multiple ligands of different metal ions. The detection limits for Hg2+, Co2+, Fe2+, and Fe3+ are calculated to be 6.51, 0.34, 0.49, and 1.01 ppb, respectively, which are far below the drinking water standards and superior to most of the reported colorimetric sensors. Remarkably, the speciation analysis of Fe2+/Fe3+ also has been successfully realized by a one-step method without complex pretreatment. The speciation and concentration of Fe2+ and Fe3+ in actual water samples can be accurately identified and monitored. In addition, as an attempt of visual onsite detection, we have developed a simple test strip, which has been applied to visual monitoring of four metal ions with the detection limit estimated by the naked eye to be as low as ppb level. This proposed colorimetric method realizes the rapid, sensitive, and portable multiple metal ions recognition and Fe2+/Fe3+ speciation analysis, displaying great potential for onsite rapid water quality analysis.

Template-Free Synthesis of Nanoporous Nickel and Alloys as Binder-Free Current Collectors of Li Ion Batteries.

This paper reports a versatile template-free method based on the hydrogen reduction of metallic salts for the synthesis of nanoporous Ni and alloys. The approach involves thermal decomposition and reduction of metallic precursors followed with metal cluster nucleation and ligament growth. Topological disordered porous architectures of metals with a controllable distribution of pore size and ligament size ranging from tens of nanometers to micrometers are synthesized. The reduction processes are scrutinized through X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The formation mechanism of the nanoporous metal is qualitatively explained. The as-prepared nanoporous Ni was tested as binder-free current collectors for nickel oxalate anodes of lithium ion batteries. The nanoporous Ni electrodes deliver enhanced reversible capacities and cyclic performances compared with commercial Ni foam. It is confirmed that this synthesis method has versatility not only because it is suitable for different types of metallic salts precursors but also for various other metals and alloys.

Visual and sensitive fluorescent sensing for ultratrace mercury ions by perovskite quantum dots.

Mercury ions sensing is an important issue for human health and environmental safety. A novel fluorescence nanosensor was designed for rapid visual detection of ultratrace mercury ions (Hg2+) by using CH3NH3PbBr3 perovskite quantum dots (QDs) based on the surface ion-exchange mechanism. The synthesized CH3NH3PbBr3 QDs can emitt intense green fluorescence with high quantum yield of 50.28%, and can be applied for Hg2+ sensing with the detection limit of 0.124 nM (24.87 ppt) in the range of 0 nM-100 nM. Furthermore, the interfering metal ions have no any influence on the fluorescence intensity of QDs, showing the perovskite QDs possess the high selectivity and sensitivity for Hg2+ detection. The sensing mechanism of perovskite QDs for Hg2+ is has also been investigated by XPS, EDX studies, showing Pb2+ on the surface of perovskite QDs has been partially replaced by Hg2+. Spot plate test shows that the perovskite QDs can also be used for visual detection of Hg2+. Our research indicated the perovskite QDs are promising candidates for the visual fluorescence detection of environmental micropollutants.

Oxygen Vacancy Promoted Heterogeneous Fenton-like Degradation of Ofloxacin at pH 3.2-9.0 by Cu Substituted Magnetic Fe3O4@FeOOH Nanocomposite.

To develop an ultraefficient and reusable heterogeneous Fenton-like catalyst at a wide working pH range is a great challenge for its application in practical water treatment. We report an oxygen vacancy promoted heterogeneous Fenton-like reaction mechanism and an unprecedented ofloxacin (OFX) degradation efficiency of Cu doped Fe3O4@FeOOH magnetic nanocomposite. Without the aid of external energy, OFX was always completely removed within 30 min at pH 3.2-9.0. Compared with Fe3O4@FeOOH, the pseudo-first-order reaction constant was enhanced by 10 times due to Cu substitution (9.04/h vs 0.94/h). Based on the X-ray photoelectron spectroscopy (XPS), Raman analysis, and the investigation of H2O2 decomposition, •OH generation, pH effect on OFX removal and H2O2 utilization efficiency, the new formed oxygen vacancy from in situ Fe substitution by Cu rather than promoted Fe3+/Fe2+ cycle was responsible for the ultraefficiency of Cu doped Fe3O4@FeOOH at neutral and even alkaline pHs. Moreover, the catalyst had an excellent long-term stability and could be easily recovered by magnetic separation, which would not cause secondary pollution to treated water.