Practical Water Samples Research Articles

The ratiometric detection and mechanism of three typical phosphonates by quercetin-based fluorescent probe with low detection limits

Phosphonates are efficient corrosion and scale inhibitors commonly used in industrial circulating water systems. However, conventional detection methods cannot accurately detect their concentration in some water bodies and sludge because of their low concentration. In this study, a ratiometric fluorescent probe was constructed based on quercetin (QC) and divalent zinc ion (Zn2+) to comparatively detect three typical phosphonates for the first time. Compared with the naked QC, Zn2+-quercetin complex (ZnQC) in the designed probe shows considerable differences in terms of luminescence properties and surface morphology. When the concentration of QC and Zn2+ were 10 mM and 50 μM, the detection limits for ATMP, HEDP, and DTPMPA were 0.223, 0.205 and 0.152 μM, respectively, which were lower than of the corresponding values obtained through the chromatography method and phosphomolybdenum blue spectrophotometry. Moreover, for the first time, the quantitative analysis of molecular surface, basin analysis, and atoms in molecules (AIM) analysis and non-covalent interaction analysis (NCI) in the Multiwfn program were employed to investigate the binding sites of QC with Zn2+. The electron excitation properties were further analyzed via theoretical calculations based on the dependent density functional theory (DFT) and time-dependent density functional theory (TDDFT). The detection mechanism can be ascribed to the static quenching considering the formation of non-fluorescent ground-state complexes. Additionally, the ratiometric probe demonstrated some features such as high sensitivity, selectivity, and a simpler operation which has been applied to detect practical water samples with satisfactory results.

Integration of CuS nanoparticles and cellulose fibers towards fast, selective and efficient capture and separation of mercury ions

This work demonstrates a novel nanomaterial for rapid, efficient and selective enrichment as well as portable separation of Hg(II) ions, which integrates the advantages of hydrophilic porous cellulose fibers and specific Hg(II) recognizing CuS nanoparticles. The optimal CuS/cellulose fibers nanomaterial (CC-60) exhibits a markedly faster adsorption rate, reaching adsorption equilibrium within 30 s, and a large Hg(II) uptake capacity as high as 1040 mg g−1 in 2 min. The distribution coefficient (Kd) of CC-60 for Hg(II) ions is four orders of magnitude higher than those for other common metal ions, thus giving unique selectivity for Hg(II) ions in the presence of other common metal ions. CC-60 can be used in portable column devices for the sequestration of Hg(II) ions from practical water samples, rapidly lowering the Hg(II) concentration from 16.6 mg L−1 to 9 μg L−1 in 5 s, which surpasses all those sulfur-based materials reported thus far. Such exciting properties are closely related to the synergistic effects arising from the porous structure and hydrophilicity of cellulose fibers, the unique recognition capability of CuS towards Hg(II), and the readily accessible CuS sites on cellulose fibers. This work would open up a new avenue to materials and devices for fast recognition, sequestration, enrichment and detection of Hg(II) as well as other toxic heavy metal ions.

A Novel Donor-Acceptor Fluorescent Sensor for Zn2+ with High Selectivity and its Application in Test Paper.

A novel donor-acceptor fluorescent sensor was designed and synthesized. The sensor exhibited high selectivity and sensitivity to Zn2+ in acetonitrile solution. When 3.0 equiv. of Zn2+ was added gradually, the emission intensity at 500nm increased 54-fold, accompanied by the fluorescent color of the solution changed from dark to green. Job's plot and ESI-MS were carried out to verify a 1:1 stoichiometric complex was formed between the sensor and Zn2+. The limit of detection (LOD) to Zn2+ was measured to be 2.81 × 10-9molL-1. Moreover, the sensor not only could be used to detect Zn2+ in practical water samples with high accuracy, but also could be made into test paper for the qualitative detection for Zn2+.

A double target fluorescent sensor based on diarylethene for detection of Al3+ and Zn2+

A novel double target sensor based on diarylethene for the detection of Al3+ and Zn2+ has been synthesized successfully. Its photochromic and fluorescent behaviors have been investigated systematically by the stimulation of UV/vis lights, Al3+, and Zn2+ in methanol solution. The sensor exhibited excellent selectivity and sensitivity towards Al3+ and Zn2+, respectively. The 1:1 stoichiometry between the sensor and Al3+/Zn2+ was verified by Job's plot and ESI-MS analysis. Moreover, the limits of detection for Al3+ and Zn2+ were 8.99 × 10−9 mol L−1 and 3.53 × 10−8 mol L−1, respectively. Finally, the sensor could be used to detect Al3+ and Zn2+ in practical water samples with high accuracy.

Surface Functional Nanofiber Membrane for Ultrasensitive and Naked-Eye Visualization of Bacterial Concentration.

Bacterial contamination in water is a serious health risk to human beings, so it is very important to realize the point-of-care (POC) bacterial detection in water. However, the traditional bacterial detection methods are time-consuming, professional- and equipment-dependent, and do not meet the needs of POC detection. There is a pressing need to develop a platform for POC bacterial detection to defeat the increasing risk of bacterial infections. Herein, a surface functional nanofiber membrane (NFM) is prepared by layer-by-layer (LBL) self-assembly as a platform for POC detection of bacterial concentration; it is naked-eye visualization and ultrasensitive. The platform shows obvious bacterial responsiveness, which allows naked-eye visualization of bacterial concentration (102-106 CFU/mL) within 30 min and can quantitatively detect the bacterial concentration (101-106 CFU/mL) by fluorescence within 5 min. The platform not only exhibits high efficiency but also has a low threshold for bacterial concentration detection. Furthermore, the platform shows good consistency with traditional methods in the detection of bacteria in practical water samples, and has the potential for use in detecting bacterial concentrations in water supplies to protect human beings from health hazards. This work also provides useful reference for research on bacterial detection, taking advantage of the surface characteristics of bacteria and the high sensitivity of NFM.

A Fiber Optic Sensor for 2,4-dichlorophenol Analysis based on Optical Composite Oxygen-sensitive Film

A novel fiber optic sensor based on optical composite oxygen-sensitive film was developed for determination of 2,4-dichlorophenol (DCP). The optical composite oxygen-sensitive film consists of tris(2,2′-bipyridyl) dichloro ruthenium(II) hexahydrate (Ru(bpy)3Cl2) as the fluorescence indicator and iron(III) tetrasulfophthalocyanine (Fe(III)PcTs) as bionic enzyme. A lock-in amplifier was used for detecting the lifetime of the composite oxygen-sensitive film by measuring the phase delay of the sensor head. The different variables affecting the sensor performance were evaluated and optimized. Under the optimal conditions (i e, pH 6.0, 25 °C, Fe(III)PcTs concentration of 5.0·10−5 mol/L), the linear detection range, detection limit and response time of the fiber optic sensor are 3.0×10−7–9.0×10−5 mol/L, 4.8×10−8 mol/L(S/N=3), and 220 s, respectively. The sensor displays high selectivity, good repeatability and stability, which have good potentials in analyzing DCP concentration in practical water samples.

A novel diarylethene‐based fluorescence sensor with a benzohydrazide unit for the detection of Zn2+

AbstractA novel fluorescent sensor on the basis of diarylethene and benzohydrazide unit was successfully synthesized. Its photochromic and fluorescent switching properties have been studied in detail by the irradiation of UV‐visible (UV‐Vis) lights and the stimulus of Zn2+/EDTA. The sensor exhibited high sensitivity and selectivity toward Zn2+ in tetrahydrofuran, which is not interfered by other cations, especially of congener Cd2+. The fluorescence intensity enhanced 84 times along with a 44‐nm blue shift of the emission peak after adding Zn2+. The stoichiometric ratio between the sensor and Zn2+ was 1:1, and the limit of detection (LOD) was calculated as 5.60 × 10−9 mol L−1. Besides, the sensor was applied in the detection of practical water samples with high accuracy.

Magnetically assisted imprinted sensor for selective detection antibiotics in river based on surface-enhanced Raman scattering

Abstract Up to date, absence of special detection property, causing a lot of waste by traditional separation technique and second pollutant were the major challenges to sensor. Herein, a SERS imprinted sensor simultaneously possessing both high sensitivity and easy separation was developed. The Ag@Fe3O4 composites were selected as SERS substrate to improve the magnetic separation performance of SERS substrate. Meanwhile, in order to promote the environmental suitability, the composite substrate modified with dopamine to synthesize the SERS imprinted sensor (Fe3O4@Ag@MIPs). The resulting materials were characterized by modern analysis measurement and the results demonstrated Fe3O4@Ag@MIPs exhibiting good magnetic separation and could be applied into selective detection of enrofloxacin hydrochloride in the practical sample. Fe3O4@Ag@MIPs as highly sensitive sensor provided an approach to residual antibiotics detection in the practical water samples.

A Highly Sensitive Visible-Light Photoelectrochemical Sensor for Pentachlorophenol Based on Synergistic Effect of 2D TiO2 Nanosheets and Carbon Dots

A new visible-light photoelectrochemical (PEC) sensor based on 2D graphene-like TiO2 nanosheets and carbon dots nanocomposites modified glassy carbon electrode (TiO2NSs/C-dots/GCE) is developed for pentachlorophenol (PCP) detection. The 2D TiO2NSs and C-dots are both synthesized by one-step solvothermal methods and the TiO2NSs/C-dots nanocomposites are prepared by a simple physical mixing method. The C-dots could effectively reduce the recombination of electrons and holes in the nanocomposites, improve the excitation conversion efficiency in visible-light area, and thus remarkably amplify the PEC signal. The PEC signal for PCP at the TiO2NSs/C-dots/GCE sensor is about 11-times and 3.2-times larger than that at the C-dots/GCE and TiO2NSs/GCE, respectively. The TiO2NSs/C-dots/GCE sensor exhibits a wide linear proportion to the PCP concentration in the range from 0.1 to 4.5 nM with a detection limit of 0.05 nM (3S N−1). Moreover, the TiO2NSs/C-dots/GCE sensor also shows high selectivity, excellent stability, and good repeatability in PCP determination. Furthermore, the TiO2NSs/C-dots/GCE sensor is further applied to determinate PCP in practical water samples.

Developed a novel quinazolinone based turn-on fluorescence probe for highly selective monitoring hypochlorite and its bioimaging applications.

A novel quinazolinone based turn-on fluorescence probe for sensitive monitoring hypochlorite was prepared using the mild condensation reaction between 2-(2'-hydroxyphenyl)-4(3H)-quinazolinone derivative and 4-methylbenzenesulfonyl hydrazide. The probe exhibited specific selectivity to ClO- with obvious optical signal changes from weak fluorescence at 560nm to a strong fluorescence emission at 520nm and color changes from colorless to yellow, which could be noticed by the naked eye. The detection limit toward hypochlorite is as low as 11.4nM. Moreover, the probe could sensitively response to ClO- in living cells with satisfying imaging effect and has been successfully applied to the determination of ClO- in practical water samples, which indicated that the probe has certain application potential for hypochlorite monitoring.

Simultaneous Cr(VI) reduction and bisphenol A degradation by a 3D Z-scheme Bi2S3-BiVO4 graphene aerogel under visible light

Rational design strategy and facile synthesis method of photocatalysts with high efficiency and stability have been still a significant challenge for the removal of environmental contaminants. In this study, a three dimensional (3D) all-solid-state Z-scheme heterojunction photocatalytic system containing bismuth sulphide (Bi2S3) and bismuth vanadate (BiVO4) was constructed as Bi2S3-BiVO4 graphene aerogel (SVGA) by a facile hydrothermal method. The potential application of as-synthesized SVGA was demonstrated to remove Cr(VI) and bisphenol A (BPA) simultaneously in aqueous media via the synergy of adsorption and photocatalysis under visible light irradiation. The removal rates of Cr(VI) and BPA both nearly reached 100% after adsorption for 40 min and photocatalysis for 120 min under visible light (λ > 420 nm), which was much better than the removal efficiency of individual Bi2S3 and BiVO4, as well as Bi2S3 graphene aerogel (SGA) and BiVO4 graphene aerogel (VGA) samples. The rGO played an important role as photoinduced electron transfer mediator between Bi2S3 and BiVO4, which promoted the photogenerated electrons transfer efficiency and enhanced photocatalytic ability of SVGA efficiently. The harmful Cr(VI) was conserved into hypotoxic Cr(III) and BPA was degraded into CO2 and H2O after photocatalysis on SVGA, and the fabricated SVGA also presented favorable stability and satisfactory application effect in practical water samples, implied that such photocatalyst has a promising application for simultaneous removal of heavy metals and organics from aqueous environment.

Novel Diarylethene-Based Fluorescent Switching for the Detection of Al3+ and Construction of Logic Circuit.

A novel photochromic diarylethene was synthesized successfully containing a phthalazine unit. Its multistate fluorescence switching properties were investigated by stimulating with UV/vis lights and Al3+/EDTA. The synthesized diarylethene displayed excellent selectivity to Al3+ with a distinct fluorescence change, revealing that it could be used as a sensor for fluorescence identification of Al3+, and a logic circuit was constructed by utilizing this diarylethene molecular platform. Moreover, it also exhibited a high accuracy for the determination of Al3+ in practical water samples.

Spectrophotometric determination of hydrogen peroxide in water by oxidative decolorization of azo dyes using Fenton system.

In this study, based on the oxidative decolorization of three azo dyes (Orange G (OG), Acid Orange 7 (AO7) and Reactive Black 5 (RB5)) with hydroxyl radicals generated in Fenton system, we have successfully established three types of azo dyes spectrophotometric methods for measuring aqueous hydrogen peroxide (H2O2) concentration. The decolorization extent of OG, AO7 and RB5 at the corresponding characteristic wavelengths of 478 nm, 484 nm and 597 nm are proportion to the concentration of H2O2 in aqueous solutions. Under the selected reaction conditions, three well linear correlations between the depletion of azo dyes and the H2O2 concentration are established in the range of 0.45-175 μmol L-1 of OG, 0.36-120 μmol L-1 of AO7 and 0.44-175 μmol L-1 of RB5, respectively. These proposed spectrophotometric methods are enough accurate to measure low concentrations of H2O2 in practical water samples and monitor the variations of H2O2 concentration during the phenol degradation in the Cu(II)/HCO3-/H2O2 process.

A novel coumarin-based fluorescent probe with fine selectivity and sensitivity for hypochlorite and its application in cell imaging

It is necessary to develop simple and highly sensitive methods for the detection of hypochlorous acid (HOCl)/hypochlorite (ClO−) to ravel its relationship with disease. In this paper, a novel bio-compatible fluorescent (Z)-8-(hydrazonomethyl)-7-hydroxy-4-methyl-2H-chromen-2-one (probe 1b) based on coumarin was synthesized and used for detecting ClO− in PBS buffer (pH = 7.2, 10 mM, 60% C2H5OH). Probe 1b showed a remarkable fluorescence change from yellow to blue with the limit of detection as low as 2.4 × 10−9 M−1 when ClO− was added. The coexisted anions, metal ions and reactive oxygen species (•OH, 1O2, H2O2, KO2) showed any competitiveness towards ClO−. In response to ClO−, the fluorescence emission intensity of probe 1b was obviously enhanced within 20 s. The mechanism was confirmed by the ESI - MS and density functional theory calculations (DFT) to reveal that the coumarin lactone bonds C − O was cleavaged by oxidation of ClO−. What's more, probe 1b could be used in practical water samples and showed well recovery. Additionally, the cell imaging experiment was demonstrated that probe 1b could be effectively exploited to imaging exogenous ClO− in vitro.

Pyrene-based ratiometric and fluorescent sensor for selective Al3+ detection

A pyrene-based sensor, named DBT, was synthesized through a one-step reaction and used as a ratiometric and fluorescent sensor for recognizing Al3+. The sensor showed high selectivity and sensitivity toward Al3+ relative to other competitive metal ions. DBT exhibited very weak fluorescence because of the photo–induced electron transfer process (PET). In the presence of Al3+, the emission of DBT at 451 nm enhanced owing to the coordination between DBT and Al3+ which hindered the PET. The detection of Al3+ by DBT was realized in a wide pH range of 5–12. The detection limits of Al3+ were 0.19 and 0.10 µM by ratiometric absorption (A360 nm/A342 nm) and fluorescent (F451 nm) methods, respectively. Moreover, DBT was also successfully applied to detect Al3+ in practical water samples and solid phase (TLC plate).

Chemosensing properties and logic gate behaviors of graphene quantum dot-appended terpyridine

Graphene quantum dot-covalently appended terpyridine, GQDs–tpy, was synthesized and characterized by X-ray photoelectron spectroscopy, FTIR spectroscopy and transmission electron microscopy. GQDs–tpy was found to act as multifunctional chemosensors: a highly selective colorimetric chemosensor for Fe2+ as evidenced by an obvious color change from colorless to pink, and a typical fluorescence enhanced probe for Zn2+ over 13 metal cations even in practical water samples. Moreover, two-input XOR, INHIBIT and IMPICATION logic gates as well as four-input OR and NOR logic gates were constructed according to the characteristic responses of GQDs-tpy to a sequence of cations.

A bifunctional sensor based on diarylethene for the colorimetric recognition of Cu2+ and fluorescence detection of Cd2.

A novel bifunctional sensor based on diarylethene with a benzyl carbazate unit was synthesized successfully. It not only served as a colorimetric sensor for the recognition of Cu2+ by showing changes in absorption spectra and solution color, but also acted as a fluorescent sensor for the detection of Cd2+ through obvious emission intensity enhancement and fluorescence color change. The sensor exhibited excellent selectivity and sensitivity towards Cu2+ and Cd2+, and the limits of detection for Cu2+ and Cd2+ were 8.36 × 10−8 mol L−1 and 1.71 × 10−7 mol L−1, respectively, which were much lower than those reported by the WHO and EPA in drinking water. Furthermore, its application in practical samples demonstrated that the sensor can be effectively applied for the detection of Cu2+ and Cd2+ in practical water samples.

A fluorescence method of detecting sulfur dioxide derivatives

A fluorescence spectrometry method is proposed to detect SO32−. The sensing mechanism is realized by utilizing the nucleophilic addition reaction between SO32− and α, β- unsaturated compounds, exhibiting remarkable blue-shift in the maximum emission wavelength (from 650 nm to 555 nm). Preliminary experiments are conducted and results show that the method exhibits high selectivity and sensitivity toward sulfite over other common anions. The fluorescence intensity ratio at 555 nm and 650 nm (I555/I650) has a good linearly with sulfite concentration ranging from 0.5 to 15 μΜ with a detection limit of 0.28 μΜ. These results provide theoretical fundamentals for sulfite detection in practical water samples.

A photoelectrochemical aptasensor constructed with core-shell CuS-TiO2 heterostructure for detection of microcystin-LR

In this work, a CuS-TiO2 heterojunction composite was prepared by dispersedly depositing CuS nanoparticles on TiO2 nanospheres surface with a hydrothermal method, and was then used to construct a photoelectrochemical (PEC) aptasensor for sensitive detection of microcystin-LR (MC-LR) in aquatic environment. The energy bands of CuS nanoparticles and spherical anatase TiO2 were well matched, which enhanced the photo-to-current conversion efficiency. The composite exhibited the enhanced visible light absorption, the improved separation of photo-generated charges, and the reduced self-aggregation of CuS nanoparticles, leading to the enhanced photocurrent response. The PEC aptasensor was constructed by immobilizing CuS-TiO2 composite on ITO electrode with chitosan film that further covalently bound aminated aptamer. After the target, microcystin-LR (MC-LR) as an analyte model, was captured by the aptamer on the aptasensor, it could be oxidized by the photo-generated hole to impede the electron-hole recombination and further amplify the photocurrent. The PEC aptasensor showed superior analytical performance for MC-LR with a linear range of 5.0 × 10−5 nM to 250 nM and a detection limit of 2.0 × 10−5 nM. The detection results with the aptasensor for practical water samples indicated its promising application in environmental monitoring.

Enhanced adsorption performance of aspartic acid intercalated Mg-Zn-Fe-LDH materials for arsenite.

A series of hydrophobic and hydrophilic amino acid (aspartic acid, phenylalanine, glutamic acid, and proline) intercalated LDH materials were synthesized and characterized. The results of batch experiments showed that Mg7Zn1Fe4-Asp-LDH and Mg7Zn1Fe4-Phe-LDH showed good adsorption performances for both arsenate and arsenite in aqueous solutions. The effects of various experimental conditions have been investigated by the batch test, which included the effects of initial pH, arsenic concentration, contact time and coexisting ions. For Mg7Zn1Fe4-Asp-LDH under the optimal experimental conditions, the maximum adsorption capacity of As(iii) and As(v) reached 94.81 mg g-1 and 57.42 mg g-1, respectively. It showed a higher adsorption capacity for As(iii) than that for As(v), which is of great significance to remove the trivalent arsenic species with higher toxicity. When the dosage of Mg7Zn1Fe4-Asp-LDH was 0.8 g L-1, the concentration of As(iii) in the aqueous solution could be reduced from 2 mg L-1 to below 10 μg L-1.When Mg-Zn-Fe-Asp-LDH was applied in practical water samples with a dosage of 0.2 g L-1, the residual concentrations of arsenic in three actual water samples were all lower than 10 μg L-1 after adsorption. The column test showed that 1.0 g of Mg7Zn1Fe4-Asp-LDH could continuously treat 2.6 L of As(iii) aqueous solution (2 mg L-1) and reduced the concentration of As(iii) to below 10 μg L-1 or handle 0.4 L of arsenic-contaminated (10 mg L-1, As(iii) : As(v) = 1 : 1) water, and the effluent concentration was below 10 μg L-1. Compared with the previously reported hydrophobic amino acid intercalated LDHs, aspartic acid (hydrophilic amino acid) intercalated LDH has a good removal efficiency for arsenic. The synthesized Mg7Zn1Fe4-Asp-LDH is considered to be a potentially functional material that can be used to treat arsenic contamination in water.