A Stable and Sensitive Engineering Bacterial Sensor via Physical Biocontainment and Two-Stage Signal Amplification.

Although engineering bacterial sensors have outstanding advantages in reflecting the actual bioavailability and continuous monitoring of pollutants, the potential escape risk of engineering microorganisms and lower detection sensitivity have always been one of the biggest challenges limiting their wider application. In this study, a core-shell hydrogel bead with functionalized silica as the core and alginate-polyacrylamide as the shell have been developed not only to realize zero escape of engineered bacteria but also to maintain cell activity in harsh environments, such as extremely acidic/alkaline pH, high salt concentration, and strong pressure. Particularly, after combining the selective preconcentration toward pollutants by functionalized core and the positive feedback signal amplification of engineering bacteria, biosensors have realized two-stage signal amplification, significantly improving the detection sensitivity and reducing the detection limit. In addition, this strategy was actually applied to the detection of As(III) and As(V) coexisting in environmental samples, and the detection sensitivity was increased by 3.23 and 4.39 times compared to sensors without signal amplification strategy, respectively, and the detection limits were as low as 0.39 and 0.86 ppb, respectively.

A cancer cell nanotherapy method based on GHz film bulk acoustic resonator and nanoscale CaO2.

Sonodynamic therapy (SDT) is an emerging cancer treatment method in recent years. However, the ultrasound signal utilized for SDT is usually located at a low-frequency spectrum (<2 MHz), and in the field of SDT research, few studies have focused on the exploration and development of ultrasound frequency. Studies have shown that the GHz-level ultrasound can increase cell membrane permeability and have a negligible effect on cell vitality. Herein, we reported the study of a GHz thin film bulk acoustic resonator as an ultrasound source for synergistic treatment with nanoscale calcium peroxide (CaO2). It was discovered that this ultrasound source ultimately achieved an efficient therapeutic outcome on mouse breast cancer cell line 4T1. Such GHz-level ultrasound application in SDT is of high significance to broaden the cognition and application scope of SDT.

Unravelling the impacts of soluble Mn(III)-NOM on arsenic immobilization by ferrihydrite or goethite under aquifer conditions.

The environmental fate of arsenic (As) relies substantially on its speciation, which occurs frequently coupled to the redox transformation of manganese. While trivalent manganese (Mn(III)), which is known for its high reactivity, is believed to play a role in As mobilization by iron (oxyhydr)oxides in dynamic aquifers, the exact roles and underlying mechanisms are still poorly understood. Using increasingly complex batch experiments that mimick As-affected aquifer conditions in combination with time-resolved characterization, we demonstrate that Mn(III)-NOM complexes play a crucial role in the manganese-mediated immobilization of As(III) by ferrihydrite and goethite. Under anaerobic condition, Mn(III)-fulvic acid (FA) rapidly oxidized 31.8% of aqueous As(III) and bound both As(III) and As(V). Furthermore, Mn(III)-FA exerted significantly different effects on the adsorption of As by ferrihydrite and goethite. Mn(III)-FA increased the adsorption of As by 6-16% due to the higher affinity of oxidation-produced As(V) for ferrihydrite under circumneutral conditions. In contrast, As adsorption by crystalline goethite was eventually inhibited due to the competitive effect of Mn(III)-FA. To summarize, our results reveal that Mn(III)-NOM complexes play dual roles in As retention by iron oxides, depending on the their crystallization. This highlights the importance of Mn(III) for the fate of As particularly in redox fluctuating groundwater environments.

Different effects of selenium speciation on selenium absorption, selenium transformation and cadmium antagonism in garlic.

Currently, planting selenium-rich crops using inorganic selenium such as selenate and selenite is used to address human selenium deficiency problems. In this paper, besides the above two traditional inorganic selenium speciation, we chose a new organic selenium speciation of potassium selenocyanoacetate to investigate the different effects of selenium speciation on selenium absorption, selenium transformation and cadmium antagonism via foliar application. Plantingexperiments showed that the selenium content of garlic bulbs treated with organic selenium was 1.8-3.9 times higher than that of inorganic selenium. Additionally, the absorption and transformation efficiency of organic selenium in garlic was also the highest, reaching over 95 %. Importantly, it was noteworthy that the cadmium content in bulbs treated with organic selenium was significantly lower than the Chinese food safety standard (0.2 mg/kg). Hence, this study provides an efficient organic selenium speciation which is beneficial to meet human selenium requirements and ensure safe utilization of cadmium-contaminated soils.

Self-acclimation mechanism of pyrite to sulfamethoxazole concentration in terms of degradation behavior and toxicity effects caused by reactive oxygen species.

Pyrite has been extensively tested for oxidizing contaminants via the activation of water molecule or dissolved oxygen, while the changing of oxidation species induced by contaminant's concentration has been largely underestimated. In this study, we revealed a self-acclimation mechanism of pyrite in terms of •OH conversion to 1O2 during the sulfamethoxazole (SMX) degradation process under oxic conditions. Two reaction stages of SMX degradation by pyrite were observed. The SMX concentration decreased by 70% rapidly in the first 12 h after the reaction was initiated, then, the removal rate began to decrease as the SMX concentration decreased. Importantly, •OH and O2•- were the dominant oxidizing species in stage one, while 1O2 was responsible for the further degradation of SMX in stage two. The self-acclimated mechanism of pyrite was proven to be caused by the conversion of oxidative species at the surface of pyrite. This process can overcome the shortages of •OH such as ultrashort lifetime and limited effective diffusion in the decontamination of micropollutant. Moreover, different reactive oxygen species will lead to different degradation pathways and environmental toxicity while degrading pollutants. This finding of oxidizing species' self-acclimation mechanism should be of concern when using pyrite for water treatment.

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.

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.

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.

Colloidal iron species driven enhanced H2O2 decomposition into hydroxyl radicals for efficient removal of methylene blue from water.

Colloids are wide-spread in natural waters and colloid-facilitated transport via adsorption was established as the most important mechanism for the mobilization of aqueous contaminants. This study reports another possible, but reasonable, role of colloids for the contaminants driven by redox reactions. Under the same conditions (pH 6.0, 0.3 ml 30% H2O2, and 25 °C), the degradation efficiencies of methylene blue (MB) at 240 min over Fe colloid, Fe ion, Fe oxide and Fe(OH)3 were 95.38%, 42.66%, 4.42% and 9.40%. We suggested that, Fe colloid can promote the H2O2 based in-situ chemical oxidation process (ISCO) compared with other iron species such as Fe(Ⅲ) ion, Fe oxide and Fe(OH)3 in natural water. Furthermore, the MB removal via adsorption by Fe colloid was only 1.74% at 240 min. Hence, the occurrence, behavior and fate of MB in Fe colloid containing natural water system mainly depends on the reduction-oxidation rather than adsorption-desorption process. Based on the mass balance of colloidal iron species and characterization of iron configurations distribution, Fe oligomers were the active and dominant components for Fe colloid-driven enhanced H2O2 activation among three types of Fe species. The quick and steady conversion of Fe(III) to Fe(II) was proven to be reason why Fe colloid can efficiently react with H2O2 to produce hydroxyl radicals.

Chalcogen Elements in Regulating the Local Electron Density of Cu2X for an Efficient Heterogeneous Fenton-like Process.

In this work, a novel strategy for Fenton activity improvement of Cu2X was reported, in which the local electron density of Cu sites was regulated via manipulation of simple chalcogen elements (O, S, and Se). Among them, Cu2Se catalysts show excellent catalytic activity to activate H2O2 for the complete removal of ofloxacin (10 mg/L) at an initial pH of 6.5 within 120 min. Radical scavenger experiments and electron spin resonance spectroscopy confirm that •OH radicals are the primary oxygen reactive species to drive ofloxacin degradation. In addition, density functional theory calculations further proved that electrons would migrate from X and accumulate on Cu active sites in the order Se > S > O. Compared with Cu2O and Cu2S, the highly concentrated electron density of Cu atoms in Cu2Se not only decreased the activation energy of the Fenton-like reaction but also boosted the Cu2+/Cu+ cycle with the generation of more •OH radicals (18-66 µm) and the maintenance of high stability of catalysts, leading to excellent catalytic activity and application potential. We believe this work will lay the foundation for designing excellent Fenton catalysts for practical applications since developing a heterogeneous Fenton system with the highest oxidation efficiency has always been the long-term goal in this field.

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.

Ultra-trace detection and efficient adsorption removal of multiple water-soluble volatile organic compounds by fluorescent sensor array.

Due to the extremely low concentration, complex composition and easy to be converted into each other in water and air of water-soluble volatile organic compounds (VOCs), it is a great challenge to the traditional detection technology, pollution control and traceability, etc. Therefore, developing a convenient, swift and on-site detection method for simultaneous quantification of multiple VOCs is highly anticipated. In this paper, a multifunctional sensor array with adsorption and sensing of VOCs has been constructed by four fluorescence channels of small-sized Eu@Uio-66 and Tb@Uio-66. Due to the obvious cross-reactive characteristics between 4 fluorescence channels and VOCs, the sensor array could detect 8 VOCs simultaneously with all detection limits as low as ppb level. In addition, the detection results of sensor array for actual water samples coexisting with multiple VOCs confirmed that it has strong anti-interference performance and could be used for simultaneous detection of multiple VOCs in real water. The construction of sensor array with VOC adsorption function not only helps to reduce the detection limit of VOCs benefiting from the pre-concentration of materials, but also has significant value to reduce the harmfulness of pollutants. Predictably, this work is of great significance for VOC traceability, analysis of ecotoxicological effects and monitoring of pollution distribution characteristics.

New method for morphological identification and simultaneous quantification of multiple tetracyclines by a white fluorescent probe.

The threat of tetracycline antibiotics to the environment and human health is attracting widespread attention. The development of morphological analysis and quantitative techniques of multiple tetracyclines is of great significance for the evaluation of biochemical toxicity, wide-spectrum antibacterial property and degradation cycle between different tetracyclines. In this study, the white fluorescent Eu/Tb@CDs was synthesized and applied successfully to the identification and detection of the most widely used tetracycline antibiotics (tetracycline (TC), oxytetracycline (OC), chlortetracycline (CC) and doxycycline (DC)) with detection limits all below 1 nM. For the actual water samples with coexistence of the above 4 tetracyclines, their simultaneous morphology identification and accurate quantitative detection can also be realized through simple spectrometric measurement. In addition, the selective and competitive experiments have been carried out on the pollutants widely present in water, and the results have also confirmed that other pollutants could not interfere with the detection of the above 4 tetracyclines. It is undeniable that this work will conveniently and visually reveal the existence information and geographical distribution characteristics of different tetracycline antibiotics in the environment and their action mechanism on organisms.

Film-based fluorescent sensor for visual monitoring and efficient removal of aniline in solutions and gas phase.

Aniline has attracted much concern for its long degradation half-life and huge toxicity to the environment and human beings. Therefore, the development of a multi-functional device for visual detection and efficient removal of aniline was highly anticipated. In our work, the small-size Eu@UiO-66(COOH) was obtained by post-synthesis modification (PSM), and then the film-based fluorescent sensor was prepared by crosslinking reaction. The films not only showed incredible mechanical stability and potential for large-scale preparation, but also have excellent fluorescence response to aniline in solutions and gas phase. As the concentration of aniline increased, the fluorescence of films gradually increased at 350 nm, while the fluorescence gradually quenching at 620 nm, and the detection limits (LOD) of aniline in water and air were 0.27 ppb and 0.086 ppb, respectively. In addition, the adsorption performance of the film for aniline has also been confirmed and the maximum adsorption capacity was 32.6 mg/g, which is a strong guarantee for the realization of ultra-trace detection and toxicity reduction of aniline. In summary, the multi-functional film sensor has been designed for ultra-trace detection and efficient removal of aniline in solutions and gas phase, and have significant value for pollutant treatment, ecological restoration and early prevention.

New Insight into a Fenton-like Reaction Mechanism over Sulfidated ß-FeOOH: Key Role of Sulfidation in Efficient Iron(III) Reduction and Sulfate Radical Generation.

Sulfidation can greatly improve the efficiency of utilization of reducing equivalents for contaminant removal; however, whether this method benefits Fenton-like reactions or not and the possible mechanism are not well understood. In this study, we revealed that surface sulfidation can greatly promote the heterogeneous Fenton activity of ß-FeOOH (Fe3S4@ß-FeOOH) by 40 times, in which not only the •OH formation was enhanced but also SO4•- as a new oxidation species was generated. Moreover, their contribution to metronidazole (MTZ) degradation was 52.5 and 37.1%, respectively. In comparison, almost no HO2•/O2•- was detected in the Fe3S4@ß-FeOOH/H2O2 system. These results were different from some previously reported Fenton counterparts. Based on the characterization and probe experiments, sulfur species, including S2-, S0, and Sn2-, as an electron donor and electron shuttle were responsible for efficient conversion of Fe(III) into Fe(II) other than via the Haber-Weiss mechanism, leading to excellent •OH generation via a Fenton-like mechanism. Most importantly, HSO5- can be generated from SO32- oxidized by •OH, and its scission into SO4•- was not dependent on the extra electric potential or Fe-O2-S(IV) intermediate. These findings provided new insight for utilizing sulfidation to improve the activity of iron-based Fenton catalysts.

Insight into enhanced Fenton-like degradation of antibiotics over CuFeO2 based nanocomposite: To improve the utilization efficiency of OH/O2- via minimizing its migration distance.

In Fenton or Fenton-like processes, the key step is to catalyze H2O2 and produce highly reactive OH radicals. More efforts are then focus on designing efficient heterogeneous Fenton catalysts by activating H2O2 to generate OH at the highest possible steady state concentration. In this study, using the antibiotic ofloxacin as target organic pollutant, we firstly demonstrate a point of view for improving OH utilization efficiency by regulating surface chemical reactions to minimizing its migration distance to the target pollutant. C doped g-C3N4 incorporated CuFeO2 (CCN/CuFeO2) exhibited almost ten times higher ofloxacin degradation rate constant than our previously reported CuFeO2 {012} catalyst (0.1634 vs 0.0179 min-1). Since similar amount of OH was generated, the different inhibition effect of tert-butyl alcohol and nitrobenzene on the ofloxacin degradation confirmed that the much-enhanced ofloxacin degradation was attributed to the surface Fenton reaction process. According to XPS and EXAFS characterization, the C-O-Cu bond between g-C3N4 and CuFeO2 established a closed-circuit surface Fenton reaction mechanism. H2O2 was adsorbed and decomposed into OH/O2- over ≡Cu + site in CuFeO2. The successful construction of CCN/CuFeO2 creates a negative surface potential and benefits the enrichment of target antibiotics from water, which greatly reduces the migration distance of OH/O2•- to adjacent pollutant and then increases the OH/O2- utilization efficiency by avoiding the unwanted quenching. Hence, CCN/CuFeO2 possesses superior Fenton catalytic activity and long-term stability.

Rapid and sensitive screening of multiple polycyclic aromatic hydrocarbons by a reusable fluorescent sensor array.

Simple and rapid sensing of polycyclic aromatic hydrocarbons (PAHs) remains a great technical challenge due to their chemical stability and structural similarity. Here, a simple, sensitive and cost-effective sensing strategy is proposed to detect multiple PAHs by utilizing the inner filter effect (IFE) and a reusable fluorescent sensor array consisting of four polyvinyl alcohol (PVA) composite carbon quantum dots (CDs) film sensors. The CDs/PVA films have a wide and tunable excitation range, which provide sufficient spectral overlap with PAHs and ensure the efficient occurrence of IFE. Under different excitations, the diverse UV absorption capacities of PAHs resulted in diverse spectral responses, enabling a unique chemical fingerprint for each PAH. Upon multivariate pattern recognition analysis, the array rendered high-throughput discrimination and sensitive quantification of 16 priority PAHs with 100% classification accuracy and detection limit as low as 57 nM. Moreover, the rapid and accurate screening of multiple environmental samples were also realized with the results consistent with high-performance liquid chromatography. This IFE-based reusable array is readily prepared, green and feasible, which exhibits great potential in environmental analysis and brings an advanced strategy to high-throughput sensing of more pollutants with similar structures and lack of recognition sites.

Identification and manipulation of active centers on perovskites to enhance catalysis of peroxymonosulfate for degradation of emerging pollutants in water.

Perovskites (the general formula of ABO3) with versatile substrates can serve as desirable catalysts to initiate advanced oxidation processes (AOPs) for environmental remediation. However, the knowledge regarding the active centers remains piecemeal and unclear, such as how the redox metal centers of B site, inert metals of A site, oxygen vacancies, and direct oxidation of catalysts govern the chemical degradation of aqueous pollutants. This study aimed to identify principal alternations in physicochemical and electrical properties of ABO3-based perovskites modified with partial/overall substitution at A/B sites and synthesized at different conditions. In order to probe varied catalytic activity of these catalysts, ofloxacin (OFX) was used as a model micro-pollutant. Results showed that the OFX degradation by activation of peroxymonosulfate (PMS) with LaFeO3 perovskite was favored by the Sr substitution at A site, Cu substitution at B site, and increasing calcination temperature. Evolution of 1O2, •OH and SO4•- have proven for efficient OFX oxidation, as evidenced by results from in-situ electron paramagnetic resonance (EPR) analyses and quenching tests. Specifically, the introduction of Sr at A site can facilitate PMS self-decomposition to produce more 1O2 due to the increased abundance of surface oxygen vacancies. In contrast, the Cu substitution at B site improved the surface oxygen vacancies, as well as the electrical conductivity, which can further accelerate •OH and SO4•- generation for the OFX degradation. This study provides deeper insights into the underlying mechanisms governing the catalytic activity of perovskites. These findings build a basis for better decontamination of hazardous environmental organic pollutants.

Smartphone as a simple device for visual and on-site detection of fluoride in groundwater.

Developing a portable device for visual and on-site detection of fluoride in groundwater is highly anticipated. In this paper, 2-(tert-butyl-diphenylsilanyloxy)-5-nitro-1H-benzoimidazole (1) has been rationally designed via a silanization reaction for self-calibration detection of fluoride, and the detection limit was calculated as 0.11 µM. The contact of 1 with fluoride would induce the cleavage of Si-O bond and trigger the emergence of excited state intramolecular proton transfer (ESIPT) process, and then the enol-like emission at 437 nm decreased accompanying with the increase of keto-like tautomerism emission at 550 nm. More importantly, considering the demand of field detection for fluoride in groundwater and combining the function of smartphone to obtain the chroma of photos. The chroma value of the fluorescence color changes from blue to yellow could be conveniently determined through a color recognizer application installed in smartphone. The device can accurately reflect the concentration of fluoride by analyzing the chroma value. The test in actual water samples confirmed that the simple device based on smartphone could be used efficiently for visual, on-site and accurate detection of fluoride in groundwater.