Metal Ions In Aqueous Solution Research Articles

Janus lamellar nanosheets fabricated at the air/liquid interface

Two-dimensional (2D) Janus nanostructures have attracted much interest due to their unique structure and properties, and researchers are making great efforts continuously to explore new preparation methods. Herein, we reported a facile method to fabricate Janus nanosheets with lamellar structures at the air/liquid interface of a water-miscible organic solution of fatty acids and an aqueous solution of metal ions. The organic solution spread on the subphase surface and diffuse into the subphase simultaneously, and the aqueous solution diffused into the organic solution at the same time. Thus, the fatty acid molecules and metal ions self-assembled into layered nanosheets with the aid of hydrophobic interaction of alkyl chains and coordination between carboxylic groups and metal ions in the mixed solution. The sides facing to air and the subphase are composed of alkyl chains and carboxylates, respectively, indicating that the nanosheets are Janus ones. Various organic solvents, metal ions and fatty acid molecules have been tried to fabricate such layered Janus nanosheets. This method is expected to be a useful way to assemble Janus nanostructures.

Carbon Dots-Doped Electrospun Fibers for Simultaneous Metal Ion Detection and Adsorption of Dyes

The required treatment and monitoring of contaminants in wastewater reinforces the development of low-cost adsorbents/chemosensors, introducing advantages relative to the detection/removal of toxic metals and dyes. Herein, it is reported a two-step process of fabrication of fluorescent carbon dots via the hydrothermal treatment of amino acids for the following encapsulation in electrospun fibers. The prominent anionic behavior of electrospun fibers of Eudragit L100 was explored for adsorption of cationic dyes (methylene blue and crystal violet)—with the prevailing electrostatic interaction of parts being favored by the formation of monolayers on the surface of adsorbents. On the other hand, the controlled release of carbon dots (CDs) from fibers to the reactor can be explored for a second application: the nitrogen ligands from released glycine-based carbon dots can be explored to indicate the presence of metal ions in aqueous solution. Our experiment resulted in a quenching in the fluorescence of the CDs in order of 90% in the emission of particles in the response of the presence of Fe3+ ions, characterizing a promising perspective for this experimental system.

Detection of Chemical Host–Guest Interactions Using a Quartz Tuning Fork Sensing System

In this paper, we investigate the potential of using quartz tuning fork (QTF) sensing system for detection of specific metal ions in aqueous solutions with sample volume of $1~\mu \text{L}$ . Functionalized self-assembled monolayers (SAMs) of L-glutathione (LG) on gold-coated QTFs were used to sense specific analytes of CaCl2 and HgCl2, whereas functionalized L-cysteine based SAMs used to sense PbCl2. The resonance frequency undergoes a shift in response to the interaction between functionalized QTF and target analyte. X-ray photoelectron spectroscopy was used to study the interaction of thiol groups between the functionalized SAM and gold coated on QTF surface. Our analysis revealed that active QTFs functionalized with LG are more sensitive to detection of CaCl2 compared with HgCl2. The SAM-based QTF sensors were found to be capable of detecting low concentrations ( $10^{- {12}}$ M) of divalent analyte solutes with high sensitivity.

Incorporating a Novel Hexaazatriphenylene Derivative to a Flexible Screen-Printed Electrochemical Sensor for Copper Ion Detection in Water Samples

A novel hexaazatriphenylene derivative, 6,7,16, 17,26,27-hexahydronaphtho[2,3-h]naphtho[2',3':7,8] quinoxalino[2,3-a]naphtho[2',3':7,8] quinoxalino[2,3-c]phenazine-5, 10,15,20,25,30-hexaone (HNQP), was successfully synthesized to selectively detect copper (Cu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ) ions over other metal ions in aqueous solutions. A flexible and planar electrochemical sensor with silver, carbon and silver/silver chloride as counter, working and reference electrodes, respectively was fabricated on a polyimide substrate using an additive screen printing process. The HNQP was drop casted on the electrochemical sensor and its capability to selectively detect Cu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ions was investigated by performing differential pulse voltammetry (DPV). A wide peak domain with average currents increasing from 0.16 μA to 17.97 μA was observed as the concentration of Cu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ions was increased from 0 μM to 100 μM, respectively, at reduction potential ~0.05V. A sensitivity of 135 μA/mM and a correlation coefficient of 0.99 was calculated for the HNQP drop casted electrochemical sensor. Further tests revealed selective detection of Cu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ions over other interfering metal ions including Co <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , Zn <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , Ni <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , Fe <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , Li <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1+</sup> , Pb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> , Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> and Ag <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1+</sup> using the HNQP drop casted electrochemical sensor. In addition, a limit of detection (LOD) and limit of quantification (LOQ) of 142 nM and 430 nM, respectively, was calculated for the sensor which is lower than the specified toxicity levels of Cu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2+</sup> ions in drinking water (20 - 30 μM) set by the U.S. environmental protection agency (EPA) and world health organization (WHO).

Differential Photosensor Activities for the L-Cysteine and L-Serine Capped ZnS:Mn Nanocrystals in the Detection of Divalent Transition Metal Ions in Aqueous Solution.

Colloidal ZnS:Mn nanocrystals (NCs) were synthesized in water by capping the NC surface with conventional amino acids: L-cysteine (Cys) and L-serine (Ser) molecules, which have very similar structures but different terminal functional groups. The optical properties were investigated by using UV-Visible and photoluminescence (PL) spectroscopy. The PL spectra for both ZnS:Mn-Cys and ZnS:Mn-Ser NCs showed broad emission peaks at 590 nm. The measured average particle size from the high-resolution transmission electron microscopy (HR-TEM) images were 4.38 nm (ZnS:Mn-Cys) and 5.57 nm (ZnS:Mn-Ser), which were also supported by Debye-Scherrer calculations. In addition, the surface charge of the NCs in aqueous solutions were measured using zeta-particle size analyzer spectroscopy, which showed formation of negatively charged surface for the ZnS:Mn-Cys (-43.93 mV) and ZnS:Mn-Ser (-8.21 mV) NCs in water. In this present study those negatively charged NCs were applied as photosensors for the detection of specific divalent transition metal cations in aqueous solution at the same condition. Consequently, the ZnS:Mn-Cys and ZnS:Mn-Ser NCs showed totally different photosensor activities upon the addition of first-row divalent transition metal ions. The former NCs showed luminescence quenching for most added metal ions except for Zn (II) ions; whereas the latter NCs showed exclusive quenching effect for Cu (II) ions at the same conditions. These results suggested that those NCs can be applied as Zn2+ and Cu2+ ion sensors in water.

Recyclable liquid crystal polymeric sensor beads based on the assistance of radially aligned liquid crystals

In this study, we first demonstrate the synthesis of recyclable polymer beads for Cu2+ sensing based on radially aligned liquid crystal (LC) assistance. To detect metal ions in water, sensing probe monomers and polymers derived from rhodamine B were synthesized. Recyclable polymeric LC beads were prepared from LC monomers RM257 and RM105, a nonreactive mesogen of 5CB and a rhodamine B-derived monomer. Due to the assistance of radially aligned LCs, highly sterically hindered spirocyclic terminal groups of rhodamine B-derived monomers were aligned and fixed at the outer surface of liquid crystal beads. The color of the polymeric LC beads changed from light pink to deep pink after the beads were dropped into an aqueous Cu2+ solution. The results were ascribed to the spiro ring-opening mechanism. The addition of a nonreactive mesogen resulted in the porous structure of the polymeric LC beads. The high sensitivity of the Cu2+ solution using polymeric LC beads was confirmed. The fabricated polymeric LC beads were recycled by putting the polymeric LC beads into aqueous ammonia. The removal of Cu2+ from polymeric LC beads was due to the formation of [Cu(NH3)4]2+. This recyclable LC bead sensor is an easy method for the detection of metal ions in aqueous solutions. The fabricated polymeric liquid crystal beads surfaces consist of aligned rhodamine B-derived active sites possess capacity of sensing copper ions in tested solutions. The color of the beads changed to deep pink while copper ions exist in the solutions, whereas it can be easily recycled by adding aqueous ammonia, indicating the beads applied as a powerful monitoring tool.

\xa0Complex Formation of Alkyl-N-iminodiacetic Acids and Hard Metal Ions in Aqueous Solution and Solid State

The calcium(II), iron(III) and chromium(III) alkyl-N-iminodiacetate systems have been studied in aqueous solution with respect to stability, acid–base properties and structure. The calcium(II) ion forms only one weak complex with methyl-N-iminodiacetic acid in water, K1 = 12.9 (2) mol–1⋅dm3, while iron(III) and chromium(III) form very stable complexes with alkyl-N-iminodiacetic acids. The calcium(II)–methyl-N-iminodiacetate complex is octahedral in the solid state with most probably water in the remaining positions giving a mean Ca–O bond distance of ca. 2.36 Å. The iron(III) alkyl-N-iminodiacetate complexes have low solubility due to a strong tendency to form polymeric structures. Depending on pH in the solution at their preparation, the degree of hydrolysis in the resulting compound(s) may differ. In the solid state, the polymeric iron(III) alkyl-N-iminodiacetate compounds seem to have the mean composition Fe2O(Cx-IDA)5; the mean Fe–O bond distances to the oxo group and the alkyl-N-iminodiacetate ligands are 1.92 and 2.02 Å, respectively. In these complexes the nitrogen atoms are bound at much longer bond distances, 0.1–0.2 Å, than the carboxylate oxygens. This distribution with short strong Fe–O bonds and much longer and weaker Fe–N bonds is also found in most other structurally characterized iron(III) carboxylated amine/polyamine complexes. The chromium(III) alkyl-N-iminodiacetate complexes are octahedral in both solution and solid state, and the low solubility of the solid compounds indicates a polymeric structure with the ligands bridging chromium(III) ions. Also, chromium(III) binds oxygen atoms in carboxylated amines at significantly shorter distance than the nitrogen stoms. The chromium(III) alkyl-N-iminodiacetate complexes display such slow kinetics at titration with strong base that the back-titration with strong acid shows completely different acid–base properties, thus the acid–base reactions are irreversible.

Critical flocculation concentration for polyvalent ions using silica nanoparticles; a new version of Schulze-Hardy rule

Critical Flocculation Concentration (CFC) is an important quantity because allows to know the optimal amount of flocculant required to remove (adsorb) specific quantities of metal ions in aqueous solution allowing to reduce both, the flocculation time and the excess of unreacted flocculant; this unreacted material produces, by itself, an additional contamination. The results reported here show that the standard Schulze-Hardy-Rule (SHR), based only in the valence z, is not longer valid to obtain the right values of CFC. In this work it is reported a correct determination of CFC for di- and tri-valent ions using different types of silica nanoparticles. Both, the initial pH slope (-pHo) and the valence z are required to determine correctly the CFC. The proposed modified version for CFC is CFC ∝ [(-pHo)z]−1.

A calcined clay fixed bed adsorption studies for the removal of heavy metals from aqueous solutions

A natural clay material from southern Tunisia was used as a low cost sorbent in a column-wise removal of metal pollutants. This is fundamentally important for a sustainable wastewater treatment strategy. This work has been performed within the framework of a project aiming to the valorization of natural geomaterials, from Tunisia, in several environmental applications. Column adsorption experiments were carried out for a better production of cleaner effluents and further understanding of the main mechanisms involved in the removal process, through a dynamic methodology, that would allow an industrial scale treatment. A calcined clay sample was used as an adsorbent for the removal of Pb(II), Cr(VI) and Cd(II) from aqueous solution. Lead removal, in presence of copper and zinc, was also studied. The effect of various parameters including bed height (2.0, 4.0 and 6.0 cm), flow rate (3, 5.8 and 9 mL/min) and influent metal ion concentrations (50, 100 and 150 mg/L) were investigated at an influent pH of 6. It was found that the exhaustion time increased with the increase of bed depth, the decrease of flow rate and initial concentration. Bohart -Adams, Thomas, Yoon–Nelson and Advection diffusion models were applied to the experimental data to predict the breakthrough curves for a better understanding of the main adsorption mechanisms. The assessment of the calcined clay performance may further explain the mechanism of metals-sorbent interaction at the water-clay interface. Thomas and Advection diffusion models were in good agreement with the experimental data. Column-wise packing of clays achieved excellent adsorption performances of metal ion in aqueous solution. The obtained results suggested a possible extension to the industrial scale of the fixed bed adsorption systems for cleaner water production, especially in the southern Tunisian districts where uncontrolled effluents discharge needs an immediate application of monitoring programs to for a sustainable improvement of water quality.

Fabrication of thiophene-chitosan hydrogel-trap for efficient immobilization of mercury (II) from aqueous environs

The fabrication of thiophene–chitosan (TCS) hydrogel has been carried out to show the excellent binding performance of Hg(II) from an aqueous solution of heavy metal ions in presence of thiophene moiety within the hydrogel network. Thiophene moiety has been implanted within chitosan, a wild bio-resources, through a facile Schiff base condensation strategy with 2-thiophenecarboxaldehyde to develop a three-dimensional network of TCS hydrogel. The parameters influencing adsorption capacity such as pH, volume of functional agent, contact time, amount of the hydrogel are included to broaden the in-depth study for the adsorption window of Hg(II) followed by the desorption and reusability performance of TCS. The results indicate that the TCS hydrogel for Hg(II) followed pseudo-second-order kinetics. Ethylenediaminetetraacetic acid (EDTA), acts as a better eluent compared to HCl to desorb Hg(II) and even after recurring adsorption/desorption cycles, removal efficacy of TCS hydrogel could be retained.

Co-pyrolysis of softwood with waste mussel shells: Biochar analysis

In this work, fisheries by-product (mussel shells) is co-pyrolyzed with forestry residues in a fast pyrolysis lab scale reactor to determine impact on biochar quality. Both mussel shells and forestry residues are waste materials with potential for the production of value added products. The pyrolysis temperature, nitrogen flow, and wood-to-mussel shell ratio (up to 50 wt%) were varied, and thermal, physical, and chemical properties of the produced biochars were investigated in a lab scale tube furnace reactor via response surface methodology (RSM). The smaller mussel shell (MS) particles decreased the surface area by filling the pores in the biochar structure. Biochars containing MS showed lower heating values, higher alkaline pH values, and higher ash content (due to the formation of CaO from CaCO3). Surface analysis showed higher functionality in co-pyrolyzed biochars, decreased hydrogen and increased nitrogen and oxygen. These properties could potentially improve adsorption of hydrophobic molecules (e.g. VOCs), acidic gases, and metal ions in aqueous solution compared to forestry biochar. Moreover, alkaline pH makes the biochar a promising additive for acidic soil.

Efficient Removal of Toxic mMetal Ions (Pb(II) and Hg(II) Ions in Single Component Systems by Adsorption on Romanian Clay Material

In this study, a local natural clay material was used for the efficient removal of Pb(II)ions and Hg(II) ions from aqueous media, in batch system. The adsorptive potential of clay material was testes at different initial solution pH, adsorbent dosage, contact time and initial heavy metal ions concentration and room temperature (20  2C). The highest adsorption efficiency of clay material was found at initial pH of 7.0 in case of Pb(II) ions, and 2.0 in case of Hg(II) ions, while the adsorbent dosage had the same value (4 g/L) for both metal ions. The adsorption equilibrium is very fast and was reach within 10 min. The modelling of experimental data showed that the adsorption processes followed the Freundlich isotherm model and pseudo-second order kinetic model. Detailed analysis of the experimental data indicate that the retention of Pb(II) and Hg(II) ions from aqueous solution on clay materials involves two processes, one of adsorption and the other of precipitation, whose succession depends on the speciation form of the metal ion in aqueous solution. However, the high adsorption capacity and short contact time are important characteristics which suggest the potential use of this clay material in environmental remediation processes.

Adsorption of multi-bivalent heavy metal ions in aqueous solution onto aminopropyl-functionalized MCM-48 preparation by co-condensation

ABSTRACT In this study, we successfully synthesized aminopropyl-functionalized MCM-48 (NH2-MCM-48) using the one-pot co-condensation strategy, with the use of co-templates. Using X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and scanning electron microscopy spectra (SEM), these findings proved that we bridged the amino groups on the mesoporous channel of MCM-48. Our results indicated that the maximum adsorption levels of Mn2+, Ni2+, Cu2+, Cd2+, and Pb2+ onto NH2-MCM-48 were 63.3 mg/g, 74.1 mg/g, 96.2 mg/g, 158.7 mg/g, and 322.6 mg/g, respectively. Our results demonstrate that NH2-MCM-48 could be used to remove Mn2+, Ni2+, Cu2+, Cd2+, and Pb2+ from wastewater.

Flash synthesis for conformal monolithic coatings of the Zr-based metal-organic framework (UiO-66-NH2) on non-modified surfaces: Applications in thin-film electrode systems

Synthesis of conformal coatings of MOFs, especially water stable ones, on different surfaces is of paramount interest due to their potential applications including electrocatalysis, sensing, and separation. Despite previous efforts that resulted in successful deposition of thin-films of MOFs on flat surfaces, a rapid, low cost, and atom-efficient synthesis of such thin-films is still challenging. Herein we report a flash synthesis to produce conformal coatings of the water-stable UiO-66-NH2 on different flat or patterned surfaces, including Si and Au-coated Si wafers, glass slides, TLC silica plates, carbon-coated and FTO-coated electrodes. The flash synthesis presented herein is accomplished within ten minutes reaction time, utilizing minimal amounts of solvent and reagents, and thus is a greener synthesis to attain conformal coatings of such MOF on solid surfaces. The versatility of the approach is demonstrated by successful conformal coatings of the UiO-66-NH2 on Si, Au, glass, silica, as well as carbon surfaces, all achieved through drop-casting on the respective substrate at 100 °C for 10 min. The utility of such thin layer coating of microporous solids in supercapacitor applications, thin layer chromatography, as well as detection of heavy metal ions in aqueous solutions is also demonstrated.

Efficient Adsorption of Heavy Metal Ions by A Novel AO‐PAN‐g‐Chitosan/Fe3O4 Composite

AbstractIn this study, a novel amidoxime‐based magnetic adsorbent (AO‐PAN‐g‐Chitosan/Fe3O4) was prepared by grafting acrylonitrile onto the surface of chitosan (CS) and magnetic Fe3O4 composite, followed by amidoximation. The magnetic adsorbents were characterized by infrared spectroscopy (FT‐IR) and X‐ray diffraction (XRD). The adsorption properties of the magnetic adsorbents for heavy metal ions in aqueous solutions were investigated under different conditions, including pH, contact time, and initial concentration of heavy metal ions. Under optimum conditions, the maximum Cu(II) and Ni(II) ion adsorption efficiencies were determined to be 38.39 mg/g and 32.68 mg/g by AO‐PAN‐g‐Chitosan/Fe3O4, respectively. Significantly, the Fe3O4/AO‐PAN‐g‐CS can be reproduced in a simple way and reused after five adsorption‐desorption cycles without any significant loss in the adsorption capacity.

Fabrication of fluorescent polymer latexes based on rhodamine B derivatives and their reusable films for Fe3+ detection

The stimulus-responsive P(MMA-co-BA-co-RhBUEA) latexes were prepared by miniemulsion polymerization of butyl acrylate (BA), methyl methacrylate (MMA), and a rhodamine-based probe RhBUEA. Their chemical composition and structures were characterized by FTIR and UV–Vis spectral analysis. Meanwhile, the effects of AIBN, SDS, and RhBUEA content on the miniemulsion polymerization and the morphology of latex particles were investigated. Based on the recipe of 30 mM SDS to the volume of water, 2 wt% AIBN and 5 wt% RhBUEA to the total monomers, the sensing properties of the resultant latex and its film were studied. Both the latex and the latex film displayed the noticeable color change, high sensitivity, superior selectivity, and anti-interference properties towards Fe3+ over other metal ions in aqueous solution. The detection limits of the latex and the latex film were 0.122 and 0.208 μM, respectively. Furthermore, the film sensor exhibited good recyclability thanks to the off-on switch, possessing the potential as a portable and reversible chemosensor for the naked-eye detection of Fe3+.

Adsorption of Cu (II)and Co (II) from aqueous solution using lignosulfonate/chitosan adsorbent

In practical application, the adsorption capacity, adsorption kinetics, recycling and production cost of adsorbent affect the application of adsorbent. In this study, porous lignosulfonate/chitosan adsorbent was prepared by simple radical polymerization of acrylic acid in the mixed solution of lignosulfonate and chitosan. The porous and large surface area of adsorbent provides more adsorption sites for heavy metal ions. A variety of characterization methods were used to characterize the appearance and structure of the adsorbent. Adsorbent can effectively adsorb heavy metal ions in aqueous solution, and has the best removal effect for Cu2+ and Co2+. The adsorption capacity of adsorbent for Co2+ is 386 mg g−1, and for Cu2+ is 283 mg g−1. 0.01 g adsorbent was used to adsorb 100 mg L−1 Cu2+, and the adsorption equilibrium was reached within 60 min. When the amount of adsorbent reaches 0.03 g, the removal rate of heavy metal ions of 100 mg L−1 can reach 99%. In this study, an adsorbent based on acrylic resin was developed.

Synthesis and coordination properties of a new ligand designed for surface functionalization of carbon substrates

The new ligand H2L, constituted by a tetraethylenepentamine functionalized with terminal 6-amino-3,4-dihydro-3-methyl-5-nitroso-4-oxopyrimidine groups, has been synthesized with the ultimate goal of preparing Pd2+-containing heterogeneous single metal ion catalysts based on multi-walled carbon nanotubes (MWCNT-L-Pd) and graphene (G-L-Pd) for catalytic applications. In this paper, we report the synthesis of the ligand and a preliminary characterization of its coordination properties performed by using Zn2+ and Cu2+ as test cations. The high stability constants, determined for the complexes with these metal ions in aqueous solution, the fast kinetic of the complexation reactions as well as the calculated structural features of the complexes are promising prerequisites supporting a successive study on the application of MWCNT-L-Pd and G-L-Pd catalysts.

Contrast-enhancing fluorescence detection of copper ions by functional fluorescent microgels

Highly sensitive and selective detection of trace Cu2+ over fourteen kinds of metal ions in aqueous solutions was achieved by the use of a novel contrast-enhancing fluorescent microgels. The microgels were prepared by the use of N-isopropylacrylamide and 1-vinylimidazole as monomers and fluorescent tetraphenylethene (TPE) derivatives as cross-linker, followed by post-functionalization with 4-(2-pyridylazo)-resorcinol (PAR). The obtained microgels were spherical in shape with narrow size distribution and could selectively fluorescent response to Cu2+ in aqueous solution or in real water samples at acidic condition, which could be even observed by naked eyes. The multi-color fluorescence emissions including white light were obtained by controlling the amount of Cu2+ added in the microgels. The detection limit for Cu2+ was ∼5.2 nM, which was nearly 1/4000 the maximum level in drinking water allowed by United States Environmental Protection Agency. The TPE-PAR probe could be renewed by adding excessive S2− to the TPE-PAR MG-Cu2+ complex. The discoloration of fluorescent detection was attributed to the coexistence of TPE and PAR in the microgels. PAR absorbed both excitation and emission fluorescence of TPE moieties, resulting in low fluorescence intensity of the microgels. After adding Cu2+, the interaction between PAR and Cu2+ changed the UV absorption intensity and position of PAR, hence leading to the change of fluorescence spectrum and color of the microgels.

A highly sensitive and selective ON-OFF fluorescent sensor based on functionalized magnetite nanoparticles for detection of Cr(VI) metal ions in the aqueous medium

Herein, we developed a very sensitive and selective fluorescent magnetic nanoparticle sensor for the selective detection of Cr(VI) metal ions in aqueous solutions. Detection of Cr(VI) metal ions is based on fluorescence quenching mechanism of the BODIPY compound bearing magnetic nanoparticles in aqueous media. The newly synthesized BODIPY compound was characterized by 1H and 13C NMR. The morphology, chemical and physical properties of the prepared nanoparticles were performed by energy-dispersive X-ray (EDX), thermo gravimetric analysis (TGA), transmission electron microscopy (TEM), FT-IR spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Fluorescence and UV–visible spectroscopies were used to investigate the selectivity of the BODIPY immobilized magnetic nanoparticle and used to detect Cr(VI) metal ion in aqueous solutions. According to the characterization, the magnetic fluorescent super magnetic iron oxide nanoparticles (F-SPION) were revealed that the average particle diameter was about 18 nm. The newly prepared fluorescent superparamagnetic nanoparticle (F-SPION) showed a fluorescence quenching response against Cr(VI) metal ions at pH 1 medium. The response of the magnetic fluorescent nanoparticle to target metal ion, Cr(VI), was highly selective, while possible interactions from other metal cations were insignificant. The fluorescence quenching of F-SPION in presence of Cr(VI) was completed in the first 5 min. These features provide potential uses of the prepared F-SPION as a new class of useful sensors for environmental applications.