Ions In Aqueous Media Research Articles

Development of Highly Efficient Dual Sensor Based on Carbon Dots for Direct Estimation of Iron and Fluoride Ions in Drinking Water

AbstractThe fluorescent nanomaterial carbon dots (CDs) have attracted tremendous attention in the recent times because of their unique physico‐chemical characteristics. Highly fluorescent CDs were prepared through a simple and nontoxic one‐step hydrothermal carbonization of polyvinylpyrrolidone (PVP). The as‐synthesised CDs, without any pre‐treatments or post‐treatments, show high stability over a broad pH range and have an excellent potential in chemical sensing applications. The as‐prepared CDs have been demonstrated to be an excellent nano probe for Fe3+ ions sensing in aqueous media based on the fluorescence quenching with high sensitivity (lower limit of detection ∼ 1 μM) and selectivity towards Fe3+ ions. “Turn off” fluorescence arises due to the formation of CDs‐Fe3+ nanocomposite complex in the solution. The nanocomposite complex forms by the attachment of Fe3+ ions to the surface emissive site of the CDs, resulting in an obvious fluorescence quenching. Here, CDs itself act as a promising nano carrier for loading of Fe3+ ions to form the CDs‐Fe3+ nanocomposite complex in the solution. In addition to all, in this study we are intensely focused to explore the application of CDs‐Fe3+ nanocomposite complex. We have used the CDs‐Fe3+ nanocomposite complex as a novel sensor probe for the detection of F‐ ions in aqueous media based on “Turn on” fluorescence mechanism. “Turn on” fluorescence occurs due to the formation of thermodynamically highly stable [FeF6]3‐ complex and bare CDs in the solution. The developed sensor has high sensitivity (lower limit of detection ∼ 1 μM) and selectivity towards F‐ ions over a wide‐ranging other competing anions. Finally, we successfully demonstrate the real life application of the developed sensor by estimating the trace F‐ ions in the real world drinking water samples.

Execution of julolidine based derivative as bifunctional chemosensor for Zn2+ and Cu2+ ions: Applications in bio-imaging and molecular logic gate.

A simple julolidine based chemosensor (JT) was designed and synthesized by single condensation step. JT displayed excellent selectivity and sensitivity with on-off responses towards Zn2+ and Cu2+ over other biologically relevant metal ions in aqueous media. Upon addition of Zn2+ ions, JT exhibited a significant blue shift in emission followed by turn-on enhancement while with Cu2+, the fluorescence intensity of JT was completely vanished. The 1:1 binding affinity between JT and Zn2+/Cu2+ was proposed by Job's plot analysis. The detection limit for Zn2+ and Cu2+ ions reached at 3.5 × 10-8 M and 1.46 × 10-6 M, respectively. The sensing mechanism of JT with Zn2+/Cu2+ was supported by DFT calculations. Based on photophysical studies and its reversibility environment with EDTA, molecular logic gates were fabricated. Furthermore, JT was successfully established to detect intracellular Zn2+ ions in live cells by turn-on response.

Selective Detection of Sub-hundred Picomolar Mercuric Ion in Aqueous Systems by Visible Spectrophotometry Using Gripe Water Functionalized Gold Nanoparticles

A selective and sensitive spectrophotometric determination of Hg2+ was designed based on gripe water functionalized gold nanoparticles (AuNP). Gripe water was employed as both a reducing and a stabilizing agent for the synthesis of gold nanoparticles. The sugar moieties of gripe water were responsible for the reduction of auric ions to Au and the resultant nanoparticles possessing an average particle size of 16 nm were highly stable over a period of 1 year. The gripe water-functionalized gold nanoparticle system was highly sensitive in detecting Hg2+ ions in aqueous medium, with the limit of detection being as low as 0.05 nM. It was also highly selective of mercury even in presence of eleven different commonly associated cations. The efficacy of the nanoparticle sensor system in the analysis of mercury in real-time samples such as bottled, tap, lake and river water has also been evaluated to be good.

Sensitive and selective detection of metal ions and small molecules in aqueous media using a hydrolytically stable amide-functionalized metal–organic framework

With the increase in human activities, the issue of environmental pollution is currently more and more serious, such as metal ions and chemical solvent pollutants which deeply influenced the human health and the environment. Herein, microporous MOF, TMU-22, with amide-decorated pores was employed for the detection of Al3+ and Fe3+ ions in aqueous media. The results demonstrated high selectivity to these ions especially Fe3+, with no interference from other metal ions. This MOF shows fast recognition of Al3+ and Fe3+ with a response time of <1 min and detection limit of 1.2 µM and 3 µM, respectively. More importantly, the KSV constant of Fe3+ was 65184 M−1, which is higher than other MOFs reported in the previous literature. Further luminescent studies revealed that TMU-22 exhibits a high-sensitivity sensing response to tetrahydrofuran with a response time of <1 min and the detection limit of 0.09%. This work would open up a new door for MOF applications in the detection of metal ions and THF in complex environments.

Highly selective silica-based fluorescent nanosensor for ferric ion (Fe3+) detection in aqueous media.

A highly selective fluorescence nanosensor was built based on the functionalized SBA-15 mesoporous silica with Dinitrophenylhydrazine (DNPH). The interaction of fabricated nanosensor was studied with metals ions in aqueous media. Under optimum conditions (time 5min, pH7, sensor dose 0.02g dispersed in 1L), SBA-15-DNPH was highly selective toward the Fe3+ ion in the presence of the different groups of interfering metal ions. The detection limit and linear concentration range of the nanosensor were 39×10-6M and 5×10-5-375×10-5M; respectively. The efficiency of nanosensor was independent on the pH range studied (6-9), which indicated that SBA-15-DNPH is a promising candidate for sensing and identification of Fe3+ ion in the environmental and other real matrix samples. SBA-15-DNPH showed good performance for Fe3+ ion detection and quantification in real samples.

Using Gold Nanoparticles with Spectroscopic and Analytical Models for Rapid Colorimetric Detection of Mercury Ions in Aqueous Media

In this study, high-sensitively colorimetric detection of mercury ions was developed according to the surface plasmon resonance of modified gold nanoparticles. While in a citrate buffer solution, the selected modifier Bismuthiol II can cause gold nanoparticles to aggregate. Gold nanoparticles with a spherical shape and average diameter of about 13 nm were prepared. While mercury ions can inhibit gold nanoparticle aggregation, after the addition of mercury ions, the color of the gold nanoparticles solution changes from light violet to red with a hypochromatic shift at the absorption peak. By collecting the UV-Vis spectrum of the solution after the reaction, the characteristic bands are selected to build a partial least squares model. Both the 0.9477 correlation coefficient with a 0.0986 mg/L standard deviation for the calibration set, and 0.9274 correlation coefficient with a 0.1020 mg/L standard deviation for the prediction set were obtained via a partial least squares model.

Activity of All-Russian Research Institute of Physical-Technical and Radio-Technical Measurements (VNIIFTRI) in the sphere of physicochemical measurements

This article presents the description, metrological characteristics and application of State primary standards developed at the All-Russian Research Institute of Physicol-Technical and Radio-Technical Measurements (VNIIFTRI). These include the state primary standards for pH and pX in aqueous solutions, units of the dispersed parameters of aerosols, suspensions and powdery materials, units of the mass fraction and mass (molar) concentration of inorganic components in aqueous solutions based on gravimetric and spectral methods of analysis. In addition, the article discusses R&amp;D projects that are currently being realized at VNIIFTRI, including the production of standard-titres and buffer solutions for pH-metry, as well as working standards for assessing the activity of Na+, K+, F-, Cl-, Br-, I-, NO3-(pX) ions in aqueous media.

Adsorption Study of Lead Ions on Nickel-Metal Organic Framework

Nickel(II) based metal-organic framework (MOF) was synthesized using terephthalic acid, C6H4(COOH)2 as an organic linker. This MOF was characterized and used as an adsorbent for the removal of lead ions in aqueous medium. Characterization was conducted by X-ray diffraction, Fourier transform infrared spectroscopy, thermal gravimetric analysis and scanning electron microscopy techniques. The removal of Pb2+ ions from aqueous medium varied with contact time, concentration, pH and temperature.

Three water soluble coordination polymers: Synthesis, crystal structure and luminescent sensing for Cr(VI) and MnO4− ions in the aqueous phase

Three isostructural coordination polymers have been synthesized and structurally characterized by IR, TGA, PXRD and X-ray single crystal diffraction. The 1D butterfly chains assembled to a novel 3-D supramolecular framework via hydrogen bonding and π–π stack. The complex 1 exhibited high fluorescence stability in water solution and can simultaneously detect Cr2O72−, CrO42− and MnO4− ions in aqueous media with high quenching constant and low detection limits of 6.82 × 104 M−1 and 4.06 μM for Cr2O72−, 1.38 × 103 M−1 and 26.1 μM for CrO42− ions, 3.1 × 104 M−1 and 6.73 μM for MnO4−. The result of interference study displayed that the compound can selectively detect Cr(VI) and MnO4− anions, indicating compound 1 may be a potential material for sensing Cr(VI) and MnO4− anions.

Highly selective luminescent sensing of Cu2+ in aqueous solution based on a Eu(III)-centered periodic mesoporous organosilicas hybrid

Using Pluronic P123 surfactant as template, a periodic mesoporous organosilica (PMO) functionalized with 4′-(4-carboxy-methyleneoxy phenyl)-2,2′:6′,2″-terpyridine (L-COOH) was successfully prepared via co-condensation using 1,2-bis(triethoxysilyl)ethane (BTESE) and the modified L-COOH (L-COOH-NH2). This terpyridine moiety forms interesting chelates to europium ions and enhances the luminescence of Eu3+ ions. Thus, a novel luminescent hybrid material was developed via linking Eu3+ complex Eu(NTA)3(H2O)2 to L-COOH-functionalized PMO material (L-COOH-PMO) using ligand exchange reactions. Investigation of photoluminescent properties shows that the prepared mesoporous hybrid Eu(NTA)3L-COOH-PMO exhibited red emission, long lifetime and high absolute quantum efficiency Φ in solid-state and aqueous solution. More interestingly, it demonstrates greatly sensitive and selective detection of Cu2+ ions in aqueous medium among test ions. The sensing mechanism was also discussed in this report.

Hot injection blended tunable CdS quantum dots for production of blue LED and a selective detection of Cu2+ ions in aqueous medium

Cadmium sulphide (CdS) quantum dots (QDs) were synthesized via hot injection colloidal technique, while oleic acid (OA) is used as capping agent to control the particle size and to prevent agglomeration. Further, using ligand exchange technique to transform hydrophobic QDs into hydrophilic. The circular shape and size (2.7–4.0 nm) of QDs were investigate through high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and Brous hypothesis respectively. The HRTEM and XRD of prepared QDs show high crystallinity and wurtzite structure. The CdS QDs showed a strong absorption and photoluminescence (PL) properties in the visible region. The absorption and PL band maxima shifted from 366–450 nm and 425–456 nm respectively with increase in the time (15–105 min). The prepared QDs show that the increased quantum yield (QY) and reduce in PL-lifetime with increasing synthesis time. The CIE-1931 chromaticity diagram of CdS QDs with varying time has lie in blue region which indicate the synthesized QDs has serve as a blue colour producing material for light emitting diode (LED). The fluorescence intensity of MPA-CdS QDs was significantly quenched in the presence of Cu2+ metal ions and limit of detection (LOD) were observed in the range of 0.63×10-3ML-1. On the basic of PL quenching peak position and Stern-Volmer relation the quenching mechanism of QDs appeared as static in nature. These finding would be helpful for determining the suitability of the CdS QDs as LED and Cu2+ optical sensor.

Biocompatible superparamagnetic carriers of chondroitin sulfate

The present study reports on the fabrication, morphological and structural characterizations, magnetic and biological tests of a biocompatible superparamagnetic carrier comprising iron oxide nanoparticle (ION) surface-functionalized with chondroitin sulfate (ChS), labelled ION@ChS. The reported ION@ChS sample is produced by alkaline coprecipitation of Fe2+ and Fe3+ ions in aqueous media in the presence of ChS. Fourier Transform infrared, Raman and x-ray photoelectron spectroscopies provide evidences for coordination of the ChS molecule (mainly through sulfonic groups) onto the ION’s surface. Transmission electron microscopy reveals that the ION@ChS are nearly spherical (mean diameter = 8.2 nm ± 0.1) and almost monodispersed (diameter dispersity = 0.11 ± 0.01), while dynamic light scattering and electrophoretic mobility measurements confirm the presence of ChS at the ION’s surface, providing mean hydrodynamic diameter (∼100 nm) and very high negative zeta potential (around −50 mV). Moreover, the ION@ChS is superparamagnetic at room temperature, with no coercivity or remanence. Cell viability tests performed by means of the MTT assay indicates that ION@ChS shows no cytotoxiciy effect (p < 0.05). Therefore, one can anticipate potential biotechnological applications of the ION@ChS sample for site-specific delivery of ChS as well as a contrast agent in magnetic resonance imaging.

Siderophore-inspired chelator hijacks uranium from aqueous medium

Over millennia, nature has evolved an ability to selectively recognize and sequester specific metal ions by employing a wide variety of supramolecular chelators. Iron-specific molecular carriers—siderophores—are noteworthy for their structural elegance, while exhibiting some of the strongest and most selective binding towards a specific metal ion. Development of simple uranyl (UO22+) recognition motifs possessing siderophore-like selectivity, however, presents a challenge. Herein we report a comprehensive theoretical, crystallographic and spectroscopic studies on the UO22+ binding with a non-toxic siderophore-inspired chelator, 2,6-bis[hydroxy(methyl)amino]-4-morpholino-1,3,5-triazine (H2BHT). The optimal pKa values and structural preorganization endow H2BHT with one of the highest uranyl binding affinity and selectivity among molecular chelators. The results of small-molecule standards are validated by a proof-of-principle development of the H2BHT-functionalized polymeric adsorbent material that affords high uranium uptake capacity even in the presence of competing vanadium (V) ions in aqueous medium.

Electrochemical sensors based on functionalized carbon nanotubes modified with platinum nanoparticles for the detection of sulfide ions in aqueous media

Vertically aligned carbon nanotube (CNT) arrays were synthesized by thermal chemical vapor deposition (CVD) on stainless steel substrates coated by cobalt nanoparticles as catalyst. Morphological and elemental analyses conducted by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) revealed that bamboo-like CNTs were blocked by Co nanoparticles at the tips. The fabricated nanotubes underwent functionalization by electrochemical oxidation in sulfuric acid, and the subsequent structural studies, as well as Fourier transform infrared (FTIR) spectroscopy confirmed that the tips of functionalized CNTs were opened while oxygenated functional groups were generated at the sidewalls and tube endings. In order to enhance the catalytic performance of the functionalized CNT-based electrodes, platinum nanoparticles were deposited on nanotubes by the potentiostatic and pulse potential electrodeposition processes, and the optimum operating parameters in both techniques were determined. The catalytic activities of these two electrodes towards methanol oxidation were determined by cyclic voltammetry (CV) testing, and a superior electrocatalytic activity and poisoning tolerance were detected for the electrode prepared by pulse deposition. The sensing performance of the pulse plated Pt/CNT electrode for the electrochemical detection and oxidation of dissolved sulfide ions was investigated. A sensitivity of $$0.632\, \upmu \hbox {A }\upmu \hbox {M}^{-1 }\hbox {cm}^{-2 }$$ and a detection limit of $$0.26~\upmu \hbox {M}$$ were obtained, indicating the enhanced capabilities of the developed sensor as a promising candidate for various industrial and environmental applications. Vertically aligned carbon nanotubes (CNTs) were synthesized by thermal chemical vapor deposition (CVD), and were subsequently functionalized by 10 cycles of electrochemical oxidation in sulfuric acid solution. CNT-based electrodes were modified by pulse plated platinum nanoparticles. The catalytic performance of the designed electrode towards methanol oxidation was investigated, and its sensing performance for the electrochemical detection of dissolved sulfide ions was explored.

A Dihomooxacalix[4]arene-gold nanohybrid based colorimetric sensor for sensitive and selective detection of iodide

ABSTRACTBidentate ureido-dihomooxacalix[4]arene based supramolecular hosts (n-propyl 1 and tert-butyl 2) were processed into organic nanoparticles via a bottom up approach in which a single step of re-precipitation was employed. These organic nanoparticles were then coupled with gold nanoparticles on the surface, resulting in an organic – inorganic hybrid framework (n-propyl H1 and tert-butyl H2). Photophysical studies of the organic nanoparticles and of the hybrid material were performed. The size and morphology were determined by TEM and DLS analysis. Moreover, the prepared hybrid frameworks were screened against various anions using UV-Visible absorption and fluorescence spectrophotometry. H1 exhibited ratiometric response towards iodide ion in aqueous medium, and colour change of the solution from pink to light blue was observed. This hybrid material selectively and sensitively detected iodide ion with detection limit of 8.3 nM and with almost no interference from other anions. H1 sensor ability was also tested with artificial and real urine samples. H2 showed different responses and no selectivity to any anion.

Colorimetric sensor for real-time detection of cyanide ion in water and food samples

An unreported organic probe (A1) was rationally designed and synthesized. The structural characterization of the A1 has been examined using NMR, FT-IR, ESI-MS and UV–Vis spectral techniques. The A1 dispensed high sensitivity and improved selectivity towards the cyanide ion in aqueous media, which was evidenced from the drastic color change. The detection limit of A1 was found to be 1.95 × 10−7 M which appreciably competes with existing CN− probes. The binding mechanism of the probe with cyanide ion was confirmed through 1H NMR titration method. Furthermore, A1 will be efficiently used to detect trace amount of cyanide ion present in food samples such as cassava flour, apple seeds, and sporting potatoes.

Тест-средства для раздельного и суммарного определения тяжелых металлов в водных средах

The classification of the main indicators of the quality of water bodies is considered. The data on controlled chemical indicators are given (content of dissolved oxygen, suspended solids, phenols, petroleum products, etc.) A list of priority hydrochemical water pollutants and the sources of their pollution are presented. The expediency of determining both individual ions of heavy metals (HM) and their complex (integral) indicators is shown by the example of the sum of HMs. The authors summarized existing data on contemporary test methods used for detection and quantitative measurement of the most prominent HM pollutants of aqueous media, namely – Fe(II), Fe(III), Co(II), Ni(II), Cu(II), Mn(II) and Al(III) ions. Concentration of such HM ions can be evaluated by various test means such as indicator papers, detector tubes and polymer plates etc. The main matrices of the test means are considered: cellulose papers, fabrics from artificial and natural fibers, silica gels, xerogels, polymeric materials, etc. The conditions for immobilization and modification of test means (carrying agent, reagent, surfactant, etc.) and principles of analyte determination using the developed test tools (visual and instrumental assessment of the intensity of staining of test forms, determination of the length of staining or bleaching of test tube zones, etc.), as well as some metrological characteristics (detection limit, range of determined contents, relative errors of definitions, etc.) are shown in this article. Detection limits of studied heavy metal ions in aqueous media that can be achieved with proposed test means are as follows: Fe(II) – (0.005-0.01) mg/l; Fe(III) – 0.1 mg/l; Co(II) – (0.02-0.4) mg/l; Ni(II) – (0.1-10) mg/l; Cu(II) – 0.05 mg/l; Mn(II) – 0.03 mg/l; Al(III) – 0.02 mg/l; total concentration of several HM ions – (0.0005-0.001) mg/l.

Optical chemosensors for metal ions in aqueous medium with polyfluorene derivatives: Sensitivity, selectivity and regeneration

Six polyfluorene derivatives, P1–P6, were synthesized and investigated as responsive materials for the optical sensing of metal ions in an aqueous medium. They were designed by combining carbazole with fluorene units within the backbone. Carbazole was N-functionalized with three coordinating groups, 2-pyridyl-benzimidazole (P1 and P4), 2-phenyl-benzimidazole (P2 and P5) and 4-phenyl-terpyridyl (P3 and P6), respectively. P1–P3 are random copolymers with fluorene:carbazole ratios of 9:1 for P1 and P2, and 9.7:0.3 for P3; P4–P6 are the corresponding alternating polymers. This design lead to polymers made of a conjugated backbone and pendant coordinating groups. The optical properties of the monomers were impacted in various ways by metal ions, and the formation of the [NiM3]2+ and [ZnM3]2+ and [ZnM32]2+ were evidenced with association constants of 105.22, 106.45 and 1014.0, respectively. The emission of the polymers was afterwards found to be influenced by theses metal ions with different sensitivity and selectivity. P1 was found to be more sensitive to the Ni2+ and Cu2+ ions with a better selectivity for Ni2+. Emission of the corresponding alternating polymer P4 was more efficiently quenched by these two ions with respect to P1, in addition of being sensitive to the Ca2+ and Al3+ ions. P3 showed sensitivity to the Ni2+, Cu2+, Al3+, Ca2+, and Zn2+ ions. The luminescence of P6 was much more pronounced with the Ni2+, Cu2+, Cd2+, Zn2+, Al3+, Fe2+, and Fe3+ ions with respect to P3. More remarkably, the presence of the Zn2+ or Cd2+ ions resulted in a new emission band, leading to the possibility to selectively sense these two ions. Relatively high Stern-Volmer constants (in the 106–105 range) were obtained, and sensitivities down to the ppb level were reached, especially for the Ni2+ ion. Influence of both the coordinating group and the polymer backbone on the polymers sensitivity and selectivity was emphasized. Finally, the recyclability of some representative optical sensors was shown both in solution and in the solid state. In particular, thin films were shown to be easily regenerated, which opens the way to the elaboration of reusable optical sensors.

A novel dendritic polymer based turn- off fluorescence sensor for the selective detection of cyanide ion in aqueous medium

Porphyrin cored polyepichlorohydrin (POR-PECH) dendritic polymer was identified as an efficient turn-off fluorescence probe for selective determination of cyanide ion in aqueous medium. The dendritic polymer showed strong red fluorescence at 656 and 718 nm which was quenched in the presence of cyanide ion. POR-PECH showed high selectivity towards cyanide ion over other relevant anions including Cl−, Br−, F−, I−, NO2−, NO3−, CH3COO−, SO32−, CO32−, SCN−, HCO3−, HPO42−, H2PO4− etc. The proposed sensor is highly selective, sensitive which showed quick response towards cyanide ion. The limit of detection of proposed method was found to be 1.2 μM which was admirably lower than the maximum allowed cyanide content in drinking water (1.9 μM) as recommended by WHO. Back folding of self assembled porphyrin cored PECH dendritic chains by the addition of cyanide ion caused the quenching of fluorescence. The time resolved fluorescence life time, FE-SEM image and DFT studies supported the quenching mechanism.

Peptide-based ratiometric fluorescent probe for highly selective detection of Cd (II) and its application in bioimaging

This work reported a new peptide fluorescent probe L including dansyl group (acceptor) and tryptophan (donor) via imitated the binding sites of natural protein. L exhibited exclusively selective ratiometric fluorescence response towards Cd2+ ions over other metal ions based on fluorescent resonance energy transfer (FRET) effects. As designed, L showed exciting sensitivity to Cd2+ ions in aqueous media, and the detection limits are less than 27.5 nM. In addition, the binding pattern of L and Cd2+ was confirmed by fluorescence titration analysis which was found to be 2:1 and further it was confirmed by Job’s plot. What’ more, L exhibited very low biotoxicity and exciting cell infiltration, and have been successfully used for fluorescence imaging of Cd2+ ions in living HeLa cells.