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Establishing a method similar to ICP-MS that can quantitatively analyze multiple heavy metals simultaneously, conveniently, and in situ is highly anticipated. In this study, we integrated the sensing elements of multiple targets and different fluorescence reporting elements to construct an engineered Escherichia coli. When these targets are present, the engineered bacteria can emit a fluorescent signal at the corresponding wavelength. To avoid the inability to accurately distinguish and quantify the content of each target due to the overlap of fluorescence signals when multiple targets coexist, a hydrogel-based separation platform similar to a separation column was constructed. The hydrogel platform can change the detection limit (LOD) and sensitivity by adjusting the adsorption strength towards different targets, so as to realize the differentiation and recognition of their respective detection signals. The LODs of this new detection method for Cd(II), Hg(II), As(III), and Pb(II) are 1.249, 0.380, 3.917, and 0.755 μg/L, respectively. In addition, this biosensor system was applied to detect coexisting Cd(II), Hg(II), As(III), and Pb(II) in actual samples with a recovery rate of 85.61–110.30 %, which is consistent with the classical ICP-MS detection results, confirming the accuracy and reliability of the method for detecting multiple heavy metal coexisting samples. [Display omitted] • A hydrogel with adjustable adsorption strength for heavy metal was constructed. • A multi-stimulus-responsive engineered bacterium was constructed. • A method for simultaneously detecting 4 coexisting heavy metals was established. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Organic probe of RBP with spiral lactam structure has been designed. • RBP can be used to simultaneously detect Al3 + and F-. • Logic detector based on RBP was designed for intelligent detection of Al3 + and F-. • The detection limits for Al3 + and F- were 0.130 mg/L and 0.0186 mg/L, respectively. [ABSTRACT FROM AUTHOR]

Nowadays, selective, sensitive and visual detection of 2,4,6-trinitrotoluene (TNT) explosives residues in groundwater system has been a great challenge for human security. Herein, a visual fluorescence paper sensor for accurate and on-site detection of TNT in groundwater system by linking the recognition molecule onto the surface of the carbon quantum dots (CDs) was introduced. The fluorescence of CDs based nanosensor can be selectively and efficiently quenched by TNT through a photo-induced electron transfer effect between primary amino groups and TNT explosives. The fluorescence quantum yield of this kind of nanosensor is up to 32.25％ and the detection limit reaches as low as 0.213 μmol/L. The interference molecules, such as the nitrobenzene derivatives have no influence on the sensitive detection of TNT. Furthermore, the paper sensor based on the CDs probe has been prepared, which can efficiently detect TNT residues in groundwater system. This developed nanosensor possesses the great capability of on-site and visual detection of TNT residues in groundwater without any further processing step. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • The small-scaled Eu-based MOF was prepared. • Fluorescence sensing FA by Eu-based MOF was conducted with LOD of 31.7 ppb. • A logic detector was designed for intelligent detection of FA in aqueous solution. • Fluorescent films were fabricated for gaseous FA detection with LOD of 11.8 ppb. [ABSTRACT FROM AUTHOR]

Abstract To develop a highly sensitive colorimetric detection method for the diabetes early diagnosis by determining the glucose in urine instead of blood can avoid the painful blood collection and risks of cross infection. In this paper, novel artificial enzyme mimics were formed by loading bimetallic nanoparticle Fe Pd on the surface of reduced graphene (rGO). Also, we proposed a Fe Pd/rGO coupled with portable paper sensor for the detection of glucose in urine. The results indicated that urine glucose can be sensitively detected in a wide range of 1–200 μM with a limit of detection (LOD) of 1.76 μM. Most important, the color difference along with the increase of urine glucose concentration can be easily distinguished by naked eyes, which is important to its practical usage in screening and diagnosis of diabetes. Furthermore, the reason of the high sensitivity of Fe Pd/rGO towards glucose was investigated in detail via various probing experiments. Fe Pd/rGO has an artificial enzyme mimic activity, which can catalyze O 2 and generate H 2 O 2 from glucose oxidation. The electron transfer between Fe Pd and H 2 O 2 will produce •OH that can oxidize terephthalic acid (TMB) by emitting a blue color. The findings in this study provide a promising alternative for the early screening and diagnosis of diabetes. Graphical abstract Hydrogen peroxide, as the product of glucose oxidation, was adsorbed and catalytic decomposition to form Free radicals (•OH) on the surface of Fe Pd/rGO nanocomposite via the partial electron exchange interaction. The strong oxidation performance of •OH can promote catalytic oxidation of TMB so as to improve sensitivity of glucose detection. Image 1 Highlights • Highly sensitive Fe Pd/rGO nanosensor were formed to detect glucose concentration. • The formation of •OH provide excellent glucose detection performance for Fe Pd/rGO nanosensor. • Sensitive visual detection of urine glucose was realized with portable paper sensor. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • A fluorescence sensor array (4 ×8 ×5) has been constructed. • The array can be used for ultra-trace detection and adsorption removal of VOC. • The detection limit of the array towards VOCs is as low as ppb. [ABSTRACT FROM AUTHOR]

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-1 H -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. [Display omitted] • 1 was prepared as a self-calibration fluoride probe. • The detection limit of 1 toward fluoride is as low as 2.09 ppb. • Fluoride detection is based on the triggered Si-O cleavage driven ESIPT process. • Smartphone as a device was prepared for visual and on-site detection of fluoride. [ABSTRACT FROM AUTHOR]

As seen, Eu3+ combined with the exposed amino groups of Eu-MOF, and induced the aggregation of Eu-MOF. And then fluorescence of Eu-MOF would quench a lot accompanying with the fluorescence changing from blue to colorless. After the gradual addition of fluoride, the fluoride anions would replace Eu3+ combined with amino groups, and the fluorescence would be recovered simultaneously. • Eu-MOF was prepared and characterized. • The LOD of Eu-MOF toward Eu3+ was calculated as (2.481 ± 0.014)×10−7 M. • The LOD of Eu-MOF toward fluoride was calculated as (1.145 ± 0.009)×10−6 M. • The logic detector was designed for Eu3+ and fluoride detection intelligently. • Paper sensors were fabricated for visual detection of Eu3+ and fluoride. Developing a portable analytical device for rapid and visual detection of multiple targeted pollutants in groundwater is very important. In this paper, a novel Eu-MOF was prepared and applied for the highly sensitive and selective detection of Eu3+ and fluoride in groundwater. In the presence of Eu3+, the blue-violet fluorescence at 425 nm of Eu-MOF is greatly quenched because of the aggregation effect caused by Eu3+ combined with the amino functional groups exposed on Eu-MOF. The detection limit of Eu3+ has been determined as (2.481 ± 0.014) ×10−7 M according to the 3σ rule. Furthermore, the addition of fluoride would replace Eu3+ bound to amino group to induce the fluorescence recovery, and the detection limit of fluoride was calculated to be (1.145 ± 0.009) ×10-6 M. The common interfering ions have no influences on the selective detection of Eu3+ and fluoride by Eu-MOF. In addition, the spiked and recovery test indicated that Eu-MOF can be used for detection of Eu3+ and fluoride in real water samples and possess efficient and favorable practicability. More importantly, the logic detectors and paper sensors based on Eu-MOF were designed and fabricated as the portable analytical devices for the visual detection of Eu3+ and fluoride in groundwater. Our research would be beneficial and helpful for the water quality safety and human health guarantee. [ABSTRACT FROM AUTHOR]