Amidoxime-grafted cotton fibers with anti-microbial sludge for efficient uranium recovery.

Uranium as a nuclear fuel, its source and aftertreatment has been a hot topic of debate for developers. In this paper, amidoxime and guanidino-modified cotton fibers (DC-AO-PHMG) were synthesized by the two-step functionalization approach, which exhibited remarkable antimicrobial and high uranium recovery property. Adsorption tests revealed that DC-AO-PHMG had excellent selectivity and anti-interference properties, the maximum adsorption capacity of 609.75 mg/g. More than 85 % adsorption capacity could still be kept after 10 adsorption-desorption cycles, and it conformed to the pseudo-second-order kinetic model and the Langmuir adsorption isotherm model as a spontaneous heat-absorbing chemical monolayer process. FT-IR, EDS and XPS analyses speculated that the amidoxime and amino synergistically increased the uranium uptake. The inhibitory activities of DC-AO-PHMG against three aquatic bacteria, BEY, BEL (from Yellow River water and lake bottom silt, respectively) and B. subtilis were significantly stronger, and the uranium adsorption was not impacted by the high bacteria content. Most importantly, DC-AO-PHMG removed up to 94 % of uranium in simulated seawater and extracted up to 4.65 mg/g of uranium from Salt Lake water, which demonstrated its great potential in the field of uranium resource recovery.

Metal-organic frame material encapsulated Rhodamine 6G: A highly sensitive fluorescence sensing platform for the detection of picric acid contaminants in water.

As a water pollutant with excellent solubility, 2,4,6-trinitrophenol (also known as picric acid, PA) poses a potential threat to the natural environment and human health, so it is crucial important to detect PA in water. In this study, a novel composite material (MIL-53(Al)@R6G) was successfully synthesized by encapsulating Rhodamine 6G into a metal-organic frame material, which was used for fluorescence detection of picric acid (PA) in water. The composite exhibits bright yellow fluorescence emission with a fluorescence quantum yield of 58.23 %. In the process of PA detection, the composite has excellent selectivity and anti-interference performance, and PA can significantly quench the fluorescence intensity of MIL-53(Al)@R6G. MIL-53(Al)@R6G has the advantages of fast detection time (20 s), wide linear range (1-100 µM) and low detection limit (4.8 nM). In addition, MIL-53(Al)@R6G has demonstrated its potential for the detection of PA in environmental water samples with satisfactory results.

Synthesis Strategies, Preparation Methods, and Applications of Chiral Metal-Organic Frameworks.

Chiral Metal-Organic Frameworks (CMOFs) is a kind of material with great application value in recent years. Formed by the coordination of metal ions or metal clusters with organic ligands. It has ordered and adjustable pores, multi-dimensional network structure, large specific surface area and excellent adsorption properties. This material structure combines the properties of metal-organic frameworks (MOFs) with the chiral properties of chiral molecules. It has great advantages in catalysis, adsorption, separation and other fields. Therefore, it has a wide range of applications in chemistry, biology, medicine and materials science. In this paper, various synthesis strategies and preparation methods of chiral metal-organic frameworks are reviewed from different perspectives, and the advantages of each method are analyzed. In addition, the applications of chiral metal-organic framework materials in enantiomer recognition and separation, circular polarization luminescence and asymmetric catalysis are systematically summarized, and the corresponding mechanisms are discussed. Finally, the challenges and prospects of the development of chiral metal-organic frame materials are analyzed in detail.

Zirconium-based metal-organic framework encapsulated dye molecules: An excellent sensing platform for sensitive detection of Cu2+ in aqueous environments.

Residual heavy metal ions in water pose a major hazard to ecology as well as human health, and Cu2+, as the most common heavy metal ion in water bodies, can cause a variety of diseases in human beings with prolonged exposure, therefore, a rational sensing platform is needed for the specific detection of Cu2+. In this work, based on the solvothermal method, we successfully prepared the composite UIO-66@FS by encapsulating the dye fluorescein sodium molecule (FS) with a metal-organic framework material (UIO-66). The composite material has bright fluorescence emission properties with a fluorescence quantum yield of 62.03 %, and the composite material has been used to construct a fluorescence sensing platform for detecting the heavy metal Cu2+ in the aqueous environment. The fluorescence of UIO-66@FS can be greatly quenched by Cu2+, which is visible to the naked eye under UV lamp. The sensing platform is able to withstand environmental interference and has the advantages of high selectivity, excellent sensitivity, fast response, wide linear range (2.5 µM-500 µM), and low detection limit (0.246 µM) in the fluorescence quenching detection of Cu2+. In addition, the sensor has been used to detect Cu2+ in real water samples with satisfactory recoveries. Therefore, this sensing probe can be an excellent candidate for Cu2+ detection and has wonderful potential for real water sample detection.

Chiral Carbon Dots and Chiral Carbon Dots with Circularly Polarized Luminescence: Synthesis, Mechanistic Investigation and Applications.

Chiral carbon dots (CCDs) can be widely used in various fields such as chiral recognition, chiral catalysis and biomedicine because of their unique optical properties, low toxicity and good biocompatibility. In addition, CCDs with circularly polarized luminescence (CPL) can be synthesized, thus broadening the prospects of CCDs applications. Since the research on CCDs is still in its infancy, this paper reviews the chiral origin, formation mechanism, chiral evolution, synthesis and emerging applications of CCDs, with a special focus on CCDs with CPL activity. It is hoped that it will provide some reference to solve the current problems faced by CCDs. Finally, the opportunities and challenges of the current research on CCDs are described, and their future development trends have also been prospected.

Electrospun Nanofiber Membrane: An Efficient and Environmentally Friendly Material for the Removal of Metals and Dyes.

With the rapid development of nanotechnology, electrospun nanofiber membranes (ENM) application and preparation methods have attracted attention. With many advantages such as high specific surface area, obvious interconnected structure, and high porosity, ENM has been widely used in many fields, especially in water treatment, with more advantages. ENM solves the shortcomings of traditional means, such as low efficiency, high energy consumption, and difficulty in recycling, and it is suitable for recycling and treatment of industrial wastewater. This review begins with a description of electrospinning technology, describing the structure, preparation methods, and factors of common ENMs. At the same time, the removal of heavy metal ions and dyes by ENMs is introduced. The mechanism of ENM adsorption on heavy metal ions and dyes is chelation or electrostatic attraction, which has excellent adsorption and filtration ability for heavy metal ions and dyes, and the adsorption capacity of ENMs for heavy metal ions and dyes can be improved by increasing the metal chelation sites. Therefore, this technology and mechanism can be exploited to develop new, better, and more effective separation methods for the removal of harmful pollutants to cope with the gradually increasing water scarcity and pollution. Finally, it is hoped that this review will provide some guidance and direction for research on wastewater treatment and industrial production.

Enantioseparation Membranes: Research Status, Challenges, and Trends.

The purity of enantiomers plays a critical role in human health and safety. Enantioseparation is an effective way and necessary process to obtain pure chiral compounds. Enantiomer membrane separation is a new chiral resolution technique, which has the potential for industrialization. This paper mainly summarizes the research status of enantioseparation membranes including membrane materials, preparation methods, factors affecting membrane properties, and separation mechanisms. In addition, the key problems and challenges to be solved in the research of enantioseparation membranes are analyzed. Last but not least, the future development trend of the chiral membrane is expected.

An electrochemical chiral sensor based on the synergy of chiral ionic liquid and 3D-NGMWCNT for tryptophan enantioselective recognition.

A facile chiral composite (3D-NGMWCNT@(S,S)-CIL) was prepared by integrating three-dimensional N-doped graphene oxide multi-walled carbon nanotubes (3D-NGMWCNT) and chiral ionic liquid ((S,S)-CIL) via electrodeposition. SEM, XRD, XPS, and electrochemical methods were used to characterize this composite and it revealed that the integrated 3D-NGMWCNT@(S,S)-CIL composite showed excellent electrochemical performance. Therefore, a 3D-NGMWCNT@(S,S)-CIL/GCE electrochemical sensor was constructed for enantioselective recognition of Trp enantiomers. The coefficient (IL/ID) of the 3D-NGMWCNT@(S,S)-CIL/GCE chiral sensor was 2.26 by differential pulse voltammograms (DPV), revealing that the synthesized 3D-NGMWCNT@(S,S)-CIL had a higher affinity for L-Trp than D-Trp. Moreover, UV-V is spectroscopy and a water contact angle test also proved this result. The 3D-NGMWCNT@(S,S)-CIL/GCE sensor had a detection limit of 0.024 µM and 0.055 µM, and sensitivity of 62.35 µA·mM-1·cm-2 and 30.40 µA·mM-1·cm-2 for L-Trp and D-Trp, respectively, with a linear response range of 0.01 to 5 mM. In addition, the 3D-NGMWCNT@(S,S)-CIL/GCE chiral sensor showed excellent stability, and good reproducibility and was applied to detect L-Trp or D-Trp in real samples. The novel 3D-NGMWCNT@(S,S)-CIL/GCE chiral sensor provides an efficient and convenient strategy for chiral enantioselective recognition. Schematic construction of the 3D-NGMWCNT@(S,S)-CIL/GCE chiral electrochemical sensors.

Highly sensitive fluorescence sensor for mercury(II) based on boron- and nitrogen-co-doped graphene quantum dots.

In this work, we invented a new method to synthesize boron- and nitrogen-co-doped graphene quantum dots (B, N-GQDs). This synthesis method was more reliable, simple, and environmentally friendly than the bottom-up methods reported in the current literature that use citric acid or other organic materials as the carbon source. Instead, B, N-GQDs were synthesized from graphene oxide (GO) by a top-down method. The obtained B, N-GQDs showed a bright blue luminescence under a UV lamp at 365 nm, and the absolute photoluminescence quantum yield (PLQY) was 5.13%. Because mercury(II) ions (Hg2+) are highly toxic and can seriously affect the ecological environment and human health, the detection of low-concentration Hg2+ and the establishment of rapid, accurate and sensitive methods for detecting Hg2+ are of great significance to the activities of life, including those of humans. Therefore, using the good luminescence properties of B, N-GQDs, we invented a new type of fluorescence sensor that can detect Hg2+. The sensor was very sensitive to Hg2+, had a good linear relationship in the concentration range of 0.2-1 µM, and exhibited a minimum limit of detection of 6.4 nM. Furthermore, this approach was successfully applied to the detection of Hg2+ in real environmental water samples.

Fabrication of an electrochemical chiral sensor via an integrated polysaccharides/3D nitrogen-doped graphene-CNT frame.

We report a novel chiral interface based on polysaccharides that was integrated via an amidation reaction between the COOH of sodium alginate and the NH2 of chitosan to form a chiral selector (SA-CS) with three dimensional N-doped graphene-CNT (NGC) as the substrate material. This interface was used for chiral discrimination of tryptophan (Trp) enantiomers via electrochemical measurements. The FT-IR, SEM, TEM and XPS characterization showed that the chiral selector and substrate materials were prepared successfully. Compared with individual SA-CS and NGC, the integrated polysaccharides/3D NGC showed higher enantioselectivity for L-Trp than D-Trp due to the smaller steric hindrance for D-Trp during the formation of three-point interactions between the two diastereoisomeric enantiomer-selector complexes, which allowed L-Trp to more easily detach from the electrode modification layer and approach the electrode surface, facilitating its approach and confirming that SA-CS had a higher constant for L-Trp when applied to real samples.

Electrochemical chiral sensing of tryptophan enantiomers by using 3D nitrogen-doped reduced graphene oxide and self-assembled polysaccharides.

A chiral sensor is described for the enantioselective recognition of L- and D-tryptophan (Trp). The sensor is based on the use of (a) Cu(II) ions coordinated with ß-cyclodextrin (Cu-ß-CD) that was self-assembled with carboxymethyl cellulose (CD-Cu-CMC) as a chiral selector, (b) of N-doped reduced graphene oxide (N-rGO) as substrate materials, and (c) of differential pulse voltammetry that was used for enantiorecognition. The 3D N-rGO was prepared by using reduced graphene oxide and pyrrole as the starting materials. Electrostatic interaction occurs between the carboxy groups of CMC and Cu(II) ions in Cu-ß-CD. The FT-IR, SEM, XRD and XPS techniques showed that 3D N-rGO and the CD-Cu-CMC composite were successfully synthesized. The 3D N-rGO enabled the immobilization of the chiral selector (CD-Cu-CMC) and improves the active areas. A glassy carbon electrode was modified with N-rGO/CD-Cu-CMC and then showed a stronger electrochemical signal for L-Trp than for D-Trp, typically at a working potential of around 0.78 V (vs. SCE). UV-vis spectroscopy proved that CD-Cu-CMC has a higher affinity for D-Trp. The enantioselectivity for D-Trp over L-Trp is 4.72. The modified electrode had a limit of detection of 0.063 µM and 0.0035 µM for L-Trp and D-Trp, respectively, with a linear response range of 0.01 mM to 5 mM. The sensor was used to detect Trp (D- or L-Trp) in spiked real human urine and human serum protein samples. Graphical abstract Schematic representation of an electrochemical chirality sensor based on the merits of N-rGO and CD-Cu-CMC. It involves the preparation of a chiral selector and a substrate material. N-Doped graphene oxide (N-rGO) was prepared by using graphene oxide (GO) and pyrrole as precursor. The combination of carboxymethyl cellulose (CMC) with Cu-ß-CD leads to a novel self-assembly framework.

RGB-D SLAM Using Point-Plane Constraints for Indoor Environments.

Pose estimation and map reconstruction are basic requirements for robotic autonomous behavior. In this paper, we propose a point-plane-based method to simultaneously estimate the robot's poses and reconstruct the current environment's map using RGB-D cameras. First, we detect and track the point and plane features from color and depth images, and reliable constraints are obtained, even for low-texture scenes. Then, we construct cost functions from these features, and we utilize the plane's minimal representation to minimize these functions for pose estimation and local map optimization. Furthermore, we extract the Manhattan World (MW) axes on the basis of the plane normals and vanishing directions of parallel lines for the MW scenes, and we add the MW constraint to the point-plane-based cost functions for more accurate pose estimation. The results of experiments on public RGB-D datasets demonstrate the robustness and accuracy of the proposed algorithm for pose estimation and map reconstruction, and we show its advantages compared with alternative methods.

Perylene-functionalized graphene sheets modified with ß-cyclodextrin for the voltammetric discrimination of phenylalanine enantiomers.

A facile approach was reported to synthesize ß-cyclodextrin functionalized graphene that is bridged by 3,4,9,10-perylene tetracarboxylic acid (rGO-PTCA-CD) via a chemical route that involves the functionalization of rGO with PTCA followed by covalently cross-linking NH2-ß-CD. The as-prepared rGO-PTCA-CD was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical methods. The working electrodes were thoroughly studied for the cyclic voltammetry by using [Fe(CN)6]4-/3- as redox probe and using ferrocene as an internal standard. Furthermore, rGO-PTCA-CD was successfully applied to the recognition of phenylalanine enantiomers. The host-guest inclusion interaction between rGO-PTCA-CD and the phenylalanine enantiomers was investigated by differential pulse voltammetry with Fc used as a competitor. The recognition result showed that the rGO-PTCA-CD-modified glassy carbon electrode exhibited higher chiral recognition capability for L-Phe than for D-Phe with an enantioselectivity coefficient of 2.07. The proposed modified electrode had a limit of detection of 0.08 nM and 0.2 nM (S/N = 3) for L-Phe and D-Phe, respectively, with a linear response range of 0.01 mM to 5 mM, which was ascribed to the synergy of the rGO-PTCA (e.g., its excellent electrochemical performance) and ß-CD (e.g., the hydrophobic inner cavity with good molecular recognition and enrichment abilities).

Perylene-functionalized graphene sheets modified with chitosan for voltammetric discrimination of tryptophan enantiomers.

A composite was prepared from graphene functionalized with 3,4,9,10-perylene tetracarboxylic acid and chitosan (rGO-PTCA-chitosan) by a chemical method. It involves non-covalent functionalization of rGO with PTCA followed by amidation reaction with chitosan. Scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and electrochemical methods were used to characterize the composites. By combining the chiral features of chitosan and the excellent electrochemical behaviors of rGO-PTCA, a graphene-based material with enantioselectivity was constructed for electrochemical chiral recognition of tryptophan (Trp) enantiomers. A glassy carbon electrode (GCE) modified with rGO-PTCA-chitosan had a higher recognition capability for L-Trp than for D-Trp. Best operated at a working voltage near 0.78 V (vs. SCE), the enantioselectivity coefficient is 3.0. The sensor has a linear response in the 1 mM to 10 mM Trp concentration range and a 1.2 µM detection limit (at S/N = 3) for L-Trp, and of 3.0 µM to D-Trp. The sensor was successfully used to detect Trp enantiomers in real samples, and a recognition mechanism is presented. Graphical abstract Schematic presentation of a composoie prepared by graphene functionalized with 3,4,9,10-perylene tetracarboxylic acid and chitosan (rGO-PTCA-chitosan) via a chemical method. It involves non-covalent functionalization of rGO with PTCA followed by amidation reaction with chitosan and voltammetric determination of tryptophan enantiomers.

Graphene-ferrocene functionalized cyclodextrin composite with high electrochemical recognition capability for phenylalanine enantiomers.

Graphene oxide (GO) modified with ferrocene (Fc) was successfully assembled via the π-π interaction (GO-Fc) and had the features of large surface area and high loading. Then, a novel composite was synthesized via ß-cyclodextrin (ß-CD) functionalized GO-Fc by combining the advantages of GO-Fc and ß-CD. An efficient chiral electrochemical sensing interface was constructed by using the rGO-Fc-CD composite as the electrode modification for the recognition of phenylalanine (Phe) enantiomers. The successful synthesis of the composites was confirmed by FTIR, XRD, TGA, SEM, and XPS results. The host-guest inclusion interaction was detected by ultraviolet spectroscopy and DPV. The recognition results demonstrated that the rGO-Fc-CD/GCE showed a higher chiral recognition capability for L-Phe than for D-Phe. The enantioselectivity coefficient (ID/IL) of the proposed sensor was 2.47. The LOD values of 27 nM and 52 nM (S/N = 3) for L-Phenylalanine and D-Phenylalanine were obtained for this electrochemical sensor. The as-synthesized material was successfully exploited for the recognition of Phe enantiomers, indicating that the developed sensor has wide application prospects.

Advances in the use of functional composites of ß-cyclodextrin in electrochemical sensors.

ß-Cyclodextrin (ß-CD) possess a hydrophobic inner cavity and a hydrophilic exterior surface. They exhibit excellent inclusion properties with the guest molecules that match cavity size, and ß-CD-based materials drew widespread attention in electrochemical sensors. The hydroxy groups at the edge of the cavity can form hydrogen bonds and undergo electrostatic and dipole-dipole interactions with other molecules. This review (with 109 refs.) reveals ß-CD-based detection mechanisms from the viewpoint of the size/shape-fit concept, and summarizes the current state of multiple electrochemical sensors based on the use of ß-CD and functionalized ß-CD such as carboxymethyl-ß-CD, mono-(6-ethanediamine-6-deoxy)-ß-CD, hydroxypropyl-ß-CD, thio-ß-cyclodextrin, and others. Graphical abstract Schematic diagram of cyclodextrin inclusion complex formation in aqueous solution, represents water molecules, represents guest molecule.

In situ growth and phenyl functionalization of titania nanoparticles coating for solid-phase microextraction of ultraviolet filters in environmental water samples followed by high performance liquid chromatography-UV detection.

Based on TiO2-nanoparticles coating fabricated by a one-step anodization method on titanium wire substrate, a novel phenyl functionalized solid-phase microextraction (SPME) fiber coating was prepared by simple and rapid in situ chemical assembling technique between the fiber surface titanol groups and trichlorophenylsilane reaction. The as-fabricated fiber exhibited good extraction capability for some UV filters and was employed to determine the ultraviolet (UV) filters in combination with high performance liquid chromatography-UV detection (HPLC-UV). The main parameters affecting extraction performance were investigated and optimized. Under the optimized conditions, the developed method was applied to detect several UV filters at trace concentration levels with only 8 mL of sample volume. They were determined in the range from 0.005 to 25 µg L(-1) with detection limits (S/N=3) from 0.1 to 50 ng L(-1). The relative standard deviations (RSDs) for single fiber repeatability varied from 4.6 to 6.5% (n=5) and fiber-to-fiber reproducibility (n=5) ranged from 5.5 to 9.1%. The linear ranges spanned two-four magnitudes with correlation coefficients above 0.9990. Five real water samples including four Yellow River water samples and one rain water sample were determined sensitively with good recoveries ranging from 86.2 to 105.5%. The functionalized fiber coating performed good reproducible manner, high mechanical strength, good stability and long service life. Moreover, this study proposed an efficient sample pretreatment method for the determination of UV filters from environmental water samples.

A novel system of galangin-potassium permanganate-polyphosphoric acid for the determination of tryptophan and its chemiluminescence mechanism.

A novel galangin-potassium permanganate (KMnO4)-polyphosphoric acid (PPA) system was found to have an outstanding response to tryptophan (Trp). Trp determination using this KMnO4 -PPA system was enhanced significantly in the presence of galangin. A highly sensitive flow-injection chemiluminescence (CL) method to determine Trp was developed based on the CL reaction of galangin-KMnO4 -Trp in PPA media. The presence of galangin, a member of the flavonol class of flavonoid complexes, greatly increased the luminous intensity of Trp in KMnO4 -PPA systems. Under optimized conditions, Trp was determined in the 0.05-10 µg/mL range, with a detection limit (3σ) of 5.0 × 10(-3) µg/mL. The relative standard deviation (RSD) was 1.0% for 11 replicate determinations of 1.0 µg/mL Trp. Two synthetic samples were determined selectively with recoveries of 98.4-100.1% in the presence of other amino acids. The possible mechanism is summarized as follows: excited states of Mn(II)(*) and Mn(III(*) types are the main means of generating chemical luminescent species, and Trp concentration and luminescence intensity have a linear relationship, which enables quantitative analysis.

Superparamagnetic functional C@Fe3O4 nanoflowers: development and application in acetaminophen delivery.

Fe3O4 nanoflowers (NFs) were synthesized via an aqueous solution method and coated with carbon through an in situ carbonization process. The synthesized C@Fe3O4 composites were further modified with strong oxidizing agents, forming functional C@Fe3O4 (FCF) flower-like composites with porous superstructure. Finally, the stable composites were used in the drug delivery test under ambient conditions; the amount of acetaminophen adsorption on the composite can weigh up to 25.07% in 3 h. The FCF composites show excellent porosity (165.23 m2 g-1) and magnetic properties (24.33 emu g-1). The -COOH, C[double bond, length as m-dash]O and -OH groups in the composites could be used for interaction with biomolecules that contain -OH, C[double bond, length as m-dash]O and -NH2 groups. Therefore, the composite exhibits a sustained release model, with release rates of 51% in the first 6 h and 73% in 12 h. This special character gives the composites potential to be used in magnetic bio-separation and drug/gene delivery. The findings in this study are useful for the engineering design of porous iron oxide coated with functional carbon that is used for medical delivery applications and other biomedical devices.