Ions In Aqueous Media Research Articles

Colorimetric detection of Co ions by a poly(vinyl alcohol)-based hydrogel using color coordinate

An organic-inorganic hybridized, poly(vinyl alcohol) (PVA)-based hydrogel was used to detect Co ions in aqueous medium. As a sensing probe, 5-dimethylamino-2-(2-pyridylazo)phenol (DMAP) was immobilized in the hydrogel. The hydrogel was prepared by the freeze-thawing method after a sol-gel reaction of DMAP, tetraethyl orthosilicate, and PVA. The color of the DMAP-PVA hydrogel changed from yellow to purple upon exposure to Co ions, the color change of the hydrogel was quantified through colorimetric analysis according to the concentrations of Co ions. The red, green, and blue (RGB) values were extracted from the photographic images of the hydrogel obtained by a stereoscopic microscope, and the RGB% and H values were calculated through the RGB values. The RGB% of the DMAP-PVA hydrogel increased with increasing Co ion concentration. In addition, the DMAP-PVA hydrogel did not show significant changes in RGB% values upon exposure to other metal ions, indicative of selectivity. For quantitative measurement of the Co ion concentration, the H value was used because it decreased linearly with increasing Co ion concentration. The DMAP-PVA hydrogel could easily detect Co ions with good specificity, easy synthesis, and portability. The intense color change was visually detected upon exposure to Co ions, even on a dried solid surface, as well as in aqueous solutions, indicating potential use in a nuclear facility.

2-Chloroquinoline-3-carbaldehyde modified nanoporous SBA-15-propylamine (SBA-Pr-NCQ) as a selective and sensitive Ag+ ion sensor in aqueous media

Design and synthesis of a mesoporous silica material functionalized with 2-chloroquinoline-3-carbaldehyde (SBA-Pr-NCQ) were developed. The pore structure of functionalized structure SBA-Pr-NCQ was characterized by different techniques. Fluorescence features of SBA-Pr-NCQ were verified by adding different metal ions in aqueous media and demonstrated good sensitivity and selectivity for Ag+ cations. The competition test displayed that the fluorescence response of the structure was specific for Ag+ cations. Additionally, the high detection limit of 7.6 × 10−6 M proved the good linear relationship between the fluorescence intensity of modified structure (SBA-Pr-NCQ) and the concentration of Ag+

Core@shell quantum dots as a fluorescent probe for the detection of cholesterol and heavy metal ions in aqueous media

In this paper, CuInS2@ZnS ([email protected]) core-shell quantum dots (QDs) were applied for the detection of heavy metals and bioanalytes. These Glutathione (GSH) capped [email protected] QDs with an average size of 3.8 nm were treated using different biologically important biomolecule analytes, such as ascorbic acid (AA), citric acid (CA), oxalic acid (OA), cholesterol (Ch), cysteine (Cy), dextrose (Dx) and urea (U). According to spectroscopic analysis, the addition of cholesterol showed photoluminescence (PL) spectra of QDs remains unchanged at the main peak position 600 nm but generates a new peak at 487 nm with cholesterol dependent enhancement. Furthermore, the addition of citric acid contributes to PL quenching in the core-shell QDs without any spectral shift. Likewise, the interaction of [email protected] QDs with different physiologically important heavy metal ions (HMI) was systematically studied as a luminescence probe. It was found out that the PL emission of [email protected] QDs was effectively quenched by copper (Cu2+) ion with significant spectral shift detected. However, Hg2+ ions also lead to PL quenching at nanomolar level but with no spectral shift observed. According to these results, [email protected] QDs are selectively sensitive to cholesterol, citric acid, Cu2+ and Hg2+ ions with satisfactory detection limit at nM level.

1,3-Dimethylvioluric acid as a colorimetric chemosensor for the selective detection of Fe3+ metal ion in aqueous medium

We have reported the synthesis, solvatochromic and metal sensing properties of 1,3-dimethylvioluric acid (DMVA). The DMVA shows a colour change from colourless to a blue colour with the addition of Fe 3+ metal ion. The structural properties and binding modes of DMVA and it's Fe 3+ complex is studied at different pH using UV-vis spectroscopy. The cyclic voltammetry of Fe 3+ -DMVA complex shows reversibility in nature. The binding constant value as obtained by plotting Benesi–Hildebrand DMVA with Fe 3+ cation found is to be 1.5736×10 3 M −1 . Job's plot behavior of DMVA with Fe 3+ cation shows binding at 3:1 molar stoichiometry. The LOD & LOQ values for DMVA with Fe 3+ cations are found to be 66.9349 nM and 202.8356 nM, respectively. The LOD value is very promising and able to defect the Fe 3+ is a very low concentration as compared to earlier reported.

SBA-Pr-Is-TAP Functionalized Nanostructured Silica as a Highly Selective Fluorescent Chemosensor for Fe3+ and Cr2O72- Ions in Aqueous Media.

SBA-Pr-Is-TAP was synthesized via functionalization of SBA-15. The synthesized hybrid nanomaterial was characterized by various techniques including FT-IR, TGA, XRD, SEM, and BET. SBA-Pr-Is-TAP could precisely bind Fe3+ and Cr2O72− ions among a range of different species in aqueous media, consequently acting as a nanoporous chemosensor of Fe3+ and Cr2O72− ions. An excellent linear relation was observed between the nanoporous chemosensor and ion concentrations, with acceptable detection limits of 2.43 × 10−6 M and 3.96 × 10−7 M for Fe3+ and Cr2O72− ions respectively.

Acoustic and Viscometric Studies of Atropine Sulphate with Life Essential 3d- Transition Metal Ions in Aqueous Medium

In the present paper, the ultrasonic velocity u, density ρ and viscosity η measurements of the drug atropine sulphate in aqueous solutions of Cu(II) and Co(II) metal ions at  298.15 K/1atm at a wide range of concentrations (0.01M-0.1M) are reported. They constitute a valuable source of information viz. inter-relationship of system composition, intermolecular interactions and the physical properties of the solute and solvent investigated. The observed values of u, ρ and η were found in the range of 1500-1550 ms-1, 1000-1040 kgm-3 and 0.8900-1.300 Nsm-2 respectively. The effect of concentration on u, ρ and η in all ternary systems of metal ions were found to be positive. Acoustical parameters such as isentropic compressibility Ks, intermolecular free length Lf, specific acoustic impedance Z, relative association RA, free volume Vf, internal pressure πi, viscous relaxation time τ, Gibb’s free energy ΔG, attenuation coefficient α, Rao’s constant Rm, and Wada’s constant w were calculated from the experimental data. It was found that all the parameters increased with increasing concentration except Vf, Lf and Ks. On the basis of the Jones-Dole equation, viscosity data were analyzed and the values of the Falkenhagen coefficient A and Jones-Dole B coefficient were evaluated. The variations in these parameters are discussed in terms of hydrophilic-hydrophilic/hydrophilic-hydrophobic interactions in these systems along with the structure-making/breaking behaviour of the drug.

2,6-bis(E)-4-methylbenzylidine)-cyclohexan-1-one as a Fluorescent-on Sensor for Ultra Selective Detection of Chromium Ion in Aqueous Media.

The ligand 2,6-bis(E)-4-methylbenzylidine)-cyclohexan-1-one sensor has been synthesized as a fluorescence-on sensor/probe for the trace level detection of chromium III ion. The synthesized ligand was characterized by FTIR, 1H-NMR spectroscopy, and fluorimetery. The sensor exhibited an ultra-selective response to chromium among the tested heavy metal ions. Different parameters were optimized like pH, effect of concentration of sensor C, metal ion and contact time. The binding stoichiometry of C:Cr3+ was calculated to be 2:1 (Job's plot) with a significantly low detection limit of 2.3 × 10- 9M. Sensor C were practically employed for detection of chromium in spiked water samples.

Near-infrared benzodiazoles as small molecule environmentally-sensitive fluorophores

The development of fluorophores emitting in the near-infrared spectral window has gained increased attention given their suitable features for biological imaging. In this work, we have optimised a general and straightforward synthetic approach to prepare a small library of near-infrared-emitting C-bridged nitrobenzodiazoles using commercial precursors. C-bridged benzodiazoles have low molecular weight and neutral character as important features that are not common in most near-infrared dyes. We have investigated their fluorescence response in the presence of a wide array of 60 different biomolecules and identified compound 3i as a potential chemosensor to discriminate between Fe2+ and Fe3+ ions in aqueous media.

Synthesis, crystal structure, CN– ion recognition property and computational studies of a novel hydrazinyl-dihydroimidazole Schiff base

A novel hydrazinyl-dihydroimidazole receptor, (E)-2-(2-(thiophen-2-ylmethylene)hydrazinyl)-4,5-dihydro-1H-imidazol-3-ium bromide (L) has been presented as a colorimetric chemosensor for rapid and selective and sensitive detection of CN– ions in aqueous medium. L has been characterized by FTIR, UV–Vis, 1H NMR, 13C NMR, EI-MS spectrometry, elemental analyses and single crystal X-ray diffraction studies. Interaction of L with CN– ion provides remarkable color change from colorless to yellow along with change in the absorption maxima, enabling naked-eye sensing without the use of any expensive instrument. 1:1 binding stoichiometry of chemosensor L towards cyanide ion has been confirmed by Job’s plot analysis. The limit of detection the chemosensor L has been found 0.89 µM, which is lower than the maximum permissible level of CN– in drinking water set by WHO. The other competitive anions (OAc-, F-, Cl-, Br-, I-, H2PO4-, NO2-, NO3-, SO42-, HSO4- and N3-) showed negligible interference for detection of cyanide ion. The sensing mechanism has been accounted by deprotonation from the exocyclic –NH site of the receptor L, which was confirmed by an 1H NMR titration experiment and DFT studies. L can be successfully applied in colorimetric test kit experiment and for the determination of CN− ions in real samples.

BODIPY immobilized MCM-41 based material: A reusable solid optical sensor for selective detection and removal of Hg(II) in water

In this paper, 4,4-difluoro-8-(4-hydroxyphenyl)-4-bora-3a,4a-diaza-s-indacene (L) was immobilized on MCM-41 to develop a pioneering colorimetric and spectrophotometric heterogeneous sensing material L-propylsilyl@MCM-41 (2) for Hg2+ ions in aqueous media. The synthesized fluorescent sensing material 2 shows overall emission intensity change ca. 89.8% selectively for Hg2+ ions over other competitive metal ions. The binding constant (ka) of L-propylsilyl@MCM-41 (2) for Hg2+ ion was determined to be 1.133 × 103 mol L-1 with a limit of detection 0.83 µM in an aqueous medium at neutral pH. A portable chemosensor kit has been prepared by coating a thin layer of 2 onto a glass film that shows an immediate colour change from yellow to pink. Further, the inductively coupled plasma spectrometry (ICP) analysis confirms that L-propylsilyl@MCM-41 (2) can be a conceivably useful and effective agent for selective detection and rapid removal of Hg2+ ions up to 98.75% from water samples.

Determination of Chromium(VI), Chromium(III), Arsenic(V), Aluminum(III), Iron(II), and Manganese(II) by Colorimetry and Surface-Enhanced Raman Scattering (SERS) Using Ferulic Acid Functionalized Silver Nanoparticles

Plasmonic nanoparticles having localized surface plasmon resonance in the visible and infrared region are potential candidates for the fabrication of simple, rapid, selective and specific metal ion detection systems based on colorimetry and surface-enhanced Raman spectroscopy. The study describes simple approaches for selective colorimetric and surface-enhanced Raman scattering determination of aluminum(III), chromium (VI), chromiun(III), manganese (II), iron(II) and arsenic (V) ions in aqueous medium using ferulic acid functionalized silver nanoparticles (F-AgNPs) synthesized by chemical reduction and microwave assisted method. The analysis of photographs reveals that ferulic acid functionalized silver nanoparticles synthesized by chemical reduction (C-F-AgNPs) sensitively detect Al(III) ions in aqueous media while nanoparticles synthesized by microwave reduction method can be used to determine As(V), Mn(II) and Fe(II) ions. In addition, C-F-AgNPs also enhance the Raman spectral profile of the water samples spiked by Cr(III) ions giving a peculiar vibration spectral feature that assists in the detection of Cr(III) ion in aqueous medium. Moreover, ferulic acid functionalized silver nanoparticles synthesized by the microwave assisted method (M-F-AgNPs) increase the intensity of Raman bands in the spectral profile of the water samples spiked with Cr(VI) and Mn(II) ions. The specific and selective interactions of F-AgNPs with the Cr(VI), Cr(III), Mn(II), Fe(II), Al(III) and As(V) leading to the aggregation of the dispersed silver nanoparticles enable their determination in aqueous media . The results of the present study shows the potential of F-AgNPs based sensor probes toward conceptualizing and fabricating simple, rapid and cost effective detection tools onsite determination of metal ions in aqueous media.

Lignin-mediated green synthesis of functionalized gold nanoparticles via pulsed laser technique for selective colorimetric detection of lead ions in aqueous media

A versatile green synthesis technique of pulsed laser irradiation and the sonochemical process was used for the production of functionalized gold nanoparticles (Au NPs) in the presence of lignin matrixes. In this study, the futuristic advantages of the lignin biopolymer were explored for the preparation of zero-valent Au NPs in the absence of any other reducing agents. The resulting lignin functionalized Au NPs (L-Auf NPs) were characterized via high-resolution transmission electron microscopy, X-ray diffraction, UV–vis spectroscopy, and Fourier-transform infrared spectroscopy. The optimum lignin concentration can generate uniformly dispersed crystalline L-Auf NPs. The optimized L-Auf (1–5) NPs permit the selective colorimetric detection of heavy metal ions; thus, the L-Auf (1–5) NPs demonstrated a highly selective colorimetric sensing tendency toward Pb2+ ions within a short time interval among the various metal ions (Pb2+, Fe3+, Cu2+, Cr6+, Co2+, Ag2+, Ca2+, Cd2+, Ba2+, and Hg2+). The prominent color change of L-Auf NPs from red wine to purple indicates the detection of Pb2+ ions. This robust characteristic nature of L-Auf (1–5) NPs can also detect very low concentrations of 1.8 μM in the linear range of 0.1–1 mM. Hence, the outcome of this study coincides with existing studies and indicates that L-Auf (1–5) NPs can also be used as effective sensors for the rapid and selective detection of Pb2+ ions via the colorimetric analysis using the real environmental samples.

A Pencil-Drawn Electronic Tongue for Environmental Applications.

We report on the development of a simple and cost-effective potentiometric sensor array that is based on manual “drawing” on the polymeric support with the pencils composed of graphite and different types of zeolites. The sensor array demonstrates distinct sensitivity towards a variety of inorganic ions in aqueous media. This multisensor system has been successfully applied to quantitative analysis of 100 real-life surface waters sampled in Mahananda and Hooghly rivers in the West Bengal state (India). Partial least squares regression has been utilized to relate responses of the sensors to the values of different water quality parameters. It has been found that the developed sensor array, or electronic tongue, is capable of quantifying total hardness, total alkalinity, and calcium content in the samples, with the mean relative errors below 18%.

Graphene oxide and Fe3O4 composite synthesis, characterization and adsorption efficiency evaluation for NO3¯ and PO43¯ ions in aqueous medium

In view of auspicious adsorption efficiency of nanocomposites (NCs), nanocomposites of graphene oxide (GO) were prepared with Fe3O4 by ultrasonic-assisted co-precipitation procedure and characterized by Fourier Transform Infra-red (FTIR), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Energy Dispersive X-Ray (EDX). The GO-Fe3O4 NCs were employed for adsorptive elimination of nitrate (NO3¯) and phosphate (PO43¯) ions from aqueous medium as a function of pH (1-10), GO-Fe3O4 NCs dose (0.05-0.1 g), contact time (0-1444 min) and ions concentration (10-100 mg L-1). Among kinetic and isotherms models, NO3¯ and PO43¯ ions removal followed the pseudo second order and Freundlich isotherm models. The maximum elimination capacity was achived up to 89 and 93 (%) for NO3¯ and PO43¯ ions, respectively at optimum operating conditions viz. pH 2, ions inital concentration 100 mg L-1, NCs dose 0.5 g and contact time 120 min. For the optimization of process variables response surface methodology (RSM) was emplyed. The results revealed that GO-Fe3O4 NCs have promising adsorption capacity for NO3¯ and PO43¯ ions and can be employed for the removal of NO3¯ and PO43¯ ions from effluents.

Curcumin immobilized metal organic framework based fluorescent nanoprobe for selective sensing and bioimaging of Fe(II)

Curcumin immobilized zeolitic imidazolate framework-8 (Cmim@ZIF-8) based probe has been reported in order to detect Fe(II) ions in aqueous medium. The Cmim@ZIF-8 nanoprobe was synthesized by a one pot process and characterized by various techniques such as X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscope and Brunauer−Emmett−Teller surface area measurement. The prepared material (Cmim@ZIF-8) was tested against various monovalent and divalent metal ions and found to be selective for detection of Fe(II). Cmim@ZIF-8 exhibit turn off fluorescence intensity with Fe(II) ions due to displacement of Curcumin indicator from ZIF-8 surface with a detection limit of 7.64 μM. Furthermore, Cmim@ZIF-8 was successfully utilised to detect Fe(II) in live HepG2 cells through fluorescence confocal imaging.

Surface functionalized GdVO4:Eu3+ nanocrystals as turn-off luminescent probe for selective sensing of Cu2+ ions: role of pH

Poly(ethylene glycol) bis(carboxymethyl) ether (PEG-diacid) functionalized GdVO4:Eu3+ (5 at%) nanocrystals have been synthesized by polyol method. X-ray diffraction and transmission electron microscopy were used for the structural and morphology characterization of GdVO4:Eu3+ samples. Fourier transform infrared spectroscopy confirms the functionalization of nanocrystal surface by PEG-diacid. The resonance energy transfer from the vanadate (VO43−) to Eu3+ results in enhanced red emission. The GdVO4:Eu3+ as luminescent probe can selectively detect the presence of Cu2+ ions out of various metal ions investigated. Upon addition of Cu2+ ions, photoluminescence intensity of Eu3+ reduces instantaneously more than 90%, which is related to energy transfer from Eu3+ to Cu2+ ions. This shows the fast response during sensing. Surface functionalized particles shows a significant sensitivity as compared to the non-functionalized particles. These probes show more favourable in the alkaline aqueous medium for sensing. The possibility of reabsorption is ruled out. The limit of detection is about 9 nM of Cu2+ with the first response time and this method will be useful in selective sensing of Cu2+ ions in aqueous medium.

Hydrophilic graphene quantum dots as turn-off fluorescent nanoprobes for toxic heavy metal ions detection in aqueous media

Efforts are being made to develop fast, cost-effective and sensitive sensor to detect water contamination by toxic heavy metal ions. The oxygenated functional groups decorated graphene quantum dots (GQDs) effectively enhances the aqueous solubility and considered as a more desirable and simple sensing material with high sensitivity. Here, photoluminescence (PL) property of GQDs has been employed to devise an optical nanosensor for the detection of toxic heavy metal ions in aqueous media. Hydrothermal method was employed to synthesize highly fluorescent and water soluble GQDs. The fluorescence intensity reduces with the increase in toxic heavy metal ions concentration. The observed PL was analyzed by the Stern-Volmer equation to study the fluorescent quenching mechanism of the system. Nonlinear behavior of Stern-Volmer plot suggests that the reduction in the fluorescent intensity is due to the combination of dynamic and static processes. The fluorescence quenching results showed that, the as synthesized GQDs are an efficient fluorescent probe for heavy metal ions viz. Hg2+, Cd2+ and Pb2+ with the detection limit of 1.171 μM, 2.455 μM and 2.011 μM respectively. This study shows the viability of GQDs as promising material for sensing the heavy metal ions in aqueous solution.

Fluorescence properties of yellow light emitting carbon quantum dots and their application for effective recognition of heavy metal ions in aqueous medium

AbstractWater‐dispersible and fluorescence‐stable carbon quantum dots (CQDs) have been synthesized at gram scale using pyrene as carbon precursor by employing the bottom‐up approach. X‐ray diffraction, FTIR, Raman spectroscopy and UV visible spectroscopy confirm the formation of CQDs. TEM images shows that size of the CQDs ranges from 2 to 5 nm. A detailed study of their optical and fluorescence characteristics was performed. Their aqueous dispersion radiates bright yellow light under UV lamp (365 nm). The research work includes derivation of their excitation wavelength, observation of influence of dilution on fluorescence and monitoring of emission intensity for about 4 months. The CQDs can effectively recognize the presence of heavy metal ions in aqueous medium at neutral pH via fluorescence quenching.

Highly selective colorimetric fluorescent probe for detecting nitrite in aqueous solution

Nitrite (NO2− ions) is a common pollutant in water and soil environment. Developing a rapid and accurate detection method for NO2− ions is always an important task. Herein, a switch-off colorimetric fluorescent probe P-NO2− was presented as the specific monitoring of NO2− ions in aqueous media. Once NO2− ions was added to the probe P-NO2− solution, the solution color changed very quickly, which was from yellow to colorless. And, the fluorescent intensity (580 nm) decreased obviously. The probe P-NO2− could test NO2− ions quantitatively (0.5–10 μM), and the detection limit was 75 nM according to 3σ/slope. Moreover, this new probe could also be used to determinate NO2− ions in the soil solution samples, river and lake water.

A benzothiazole-based receptor for colorimetric detection of Cu2+ and S2− ions in aqueous media

A benzothiazole-based azo compound was synthesized and evaluated as a probe for the selective sensing of cations and anions. The probe (PA) could detect Cu2+ ions in aqueous media selectively, without interference from other cations and with a limit of detection of 0.43 μM. The resultant complex, PA-Cu2+, could be used as a secondary probe for detecting S2− ions in aqueous media in the presence of other interfering anions through a cation displacement process.