Presence Of Other Metal Ions Research Articles

Biosorption of Cd(II) from synthetic wastewater using dry biofilms from biotrickling filters

Biofilms wasted from biotrickling filters was dried and used as biosorbent for Cd(II) removal from aqueous solutions. The adsorption condition and effect, adsorption isotherms and kinetics of Cd(II) removal were investigated, and the effects of competitive metal ions on Cd(II) removal were also examined. Results showed that the dry waste biofilms reached the maximum adsorption capacity of 42 mg/g of Cd(II) at 25 °C for 120 min when the initial concentration of Cd(II) and their pH were 50 mg/L and 6.0, respectively. Under these conditions, the removal efficiency of Cd(II) reached to 89.3% when the biosorbent dosage was 2.0 g/L. The Langmuir isotherm model correlated with the isotherm data better than the Freundlich isotherm model, and the pseudo-second-order model fitted the kinetic data better than the pseudo-first-order model. These results indicated that the adsorption was monolayer accompanied with chemical adsorption. In the presence of other metal ions, divalent metal ions of Ca and Zn inhibited the performance of Cd(II) biosorption significantly, while Na(I), K(I) and Fe(III) which had a higher or lower valence than Ca(II) affected slightly when containing 50 mg/L Cd(II), 0.5 g/L adsorbent dosage and pH 6.0. The analyses of scanning electron microscopy and Fourier transform infrared spectroscopy illuminated that the biosorbent had porous structures and the amide group was the majorly responsible for Cd(II) removal. Dry biofilms were novel sorbents for effective removal Cd(II), and it could be reused and recycled if necessary.

Highly selective and sensitive fluorogenic ferric probes based on aggregation-enhanced emission with − SiMe3 substituted polybenzene

In this study, thiophene was linked to polybenzene to generate novel fluorescent probes, namely 3,4-diphenyl-2,5-di(2-thienyl)phenyl-trimethylsilane (DPTB-TMS) with a −SiMe3 substituent and 3,4-diphenyl-2,5-di(2-thienyl)phenyl (DPTB) without the −SiMe3 substituent, respectively. Both of the two compounds exhibit aggregation-enhanced emission (AEE) properties in tetrahydrofuran/water mixtures due to restricted intramolecular rotation of the peripheral groups, which make the two compounds good candidates for the detection of Fe3+ ions in aqueous-based solutions. The fluorescence intensity of the two compounds decreases immediately and obviously upon addition of a trace amount of Fe3+, and decreases continuously as the amount of Fe3+ increases. The fluorescence was quenched to 92% of its initial intensity when the amount of Fe3+ ions reached 6μmol for DPTB-TMS and to 80% for DPTB in the systems, indicating that the compound with the −SiMe3 group is a more effective probe. The detection limit was found to be 1.17μM (65ppb). The detection mechanism is proposed to be static quenching. DPTB-TMS is highly efficient for the detection of ferric ions even in the presence of other metal ions. In addition, the method is also successfully applied to the detection of ferric ions in water, blood serum, or solid films. This indicates that these polybenzene compounds can be applied as low-cost, high selectivity, and high efficiency Fe3+ probes in water or in clinical applications.

Colorimetric Detection of Mercury(II) Ion in Aqueous Solution Using Silver Nanoparticles.

Novel green-chemistry synthesis of silver nanoparticles (AgNPs) is introduced as a low-cost, rapid and easy-to-use analytical method for mercury ion detection. Aqueous fruit extract of water apple (Syzygium aqueum) was used for the first time as bioreductant to synthesize stable AgNPs. The prepared AgNPs have a yellowish-brown color with a surface plasmon resonance peak at 420 nm. The addition of Hg(II) ions then changes the AgNPs color to colorless. The color change was in proportion to the concentration of Hg(II) ions. The presence of other metal ions in the system was also evaluated. The proposed method shows good selectivity and sensitivity towards Hg(II) ions. Using UV-visible spectrophotometry, the detection limit of the developed method was 8.5 × 10-7 M. The proposed method has been successfully applied for determination of Hg(II) ions in tap and lake water samples with precision better than 5%.

A coumarin based azo-phenol ligand as efficient fluorescent “OFF-ON-OFF” chemosensor for sequential detection of Mg2+ and F−: Application in live cell imaging and as molecular logic gate

A novel coumarin based azo-phenol ligand (H2L) has been synthesized and characterized by several spectroscopic techniques. An almost 16 fold enhancement of emission intensity has been observed upon gradual addition of Mg2+ to H2L in DMSO:H2O (1:5v/v) medium while it has no significant effect in emission intensity even in presence of other metal ions. The emission intensity of L-Mg2+ complex has almost quenched on gradual addition of F− to it. The limit of detection for both Mg2+ and F− are of 10−8M order, hence the newly developed chemosensor is highly efficient in detecting Mg2+ and F− in very minute levels. The chemosensor can even detect Mg2+ in the intracellular region of human lung cancer cells (A549 cells).

A new Schiff base as a turn‐off fluorescent sensor for Cu2+ and its photophysical properties

A new Schiff base receptor 1 was synthesized and its photophysical properties were investigated by absorption, emission and excitation techniques. Furthermore, its chromogenic and fluorogenic sensing abilities towards various metal ions were examined. Receptor 1 selectively detects Cu2+ ion through fluorescence quenching and detection was not inhibited in the presence of other metal ions. From fluorescence titration, the limit of detection of receptor 1 as a fluorescent 'turn-off' sensor for the analysis of Cu2+ was estimated to be 0.35μM.

Highly selective and sensitive detection of Cr6+ ions using size-specific label-free gold nanoparticles

Gold nanoparticles (AuNPs) of various sizes were synthesized by modifying the citrate concentration; 45nm AuNPs were found to respond to Cr6+ ions selectively. Label-free AuNPs, 45nm, showed localized surface plasmon resonance bands at 530nm, which decreased linearly upon addition of Cr6+. The addition of Cr6+ also resulted in the appearance of a new band at 750nm, along with a visible color change in the solution from wine red to violet. The decrease in absorbance and color change were due to AuNP aggregation upon coordination of Cr6+. The detection limit for Cr6+ was 0.4nM, and excellent selectivity was observed in the presence of other metal ions and anions. The binding site and sensing mechanism for Cr6+ and label-free AuNPs were characterized by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry. This method was applied to tap, pond, and waste water samples, and validated using inductively coupled plasma-optical emission spectrometry, illustrating the utility of the sensitive, selective, and simple AuNP sensor in the detection of Cr6+.

Functionalized chitosan biosorbents with ultra-high performance, mechanical strength and tunable selectivity for heavy metals in wastewater treatment

Water pollution is the most challenging issue facing mankind nowadays as a result of ever-increasing population and steadily improving life standards. More and more wastewater without effective treatments is arbitrarily discharged into the aquatic environment, which causes irreversible damage and incalculable loss. Especially, the industrial wastewater containing heavy metal ions, such as copper (Cu), cobalt (Co), and manganese (Mn), are toxic to human and living organisms even at low concentrations. A highly efficient and selective removal method has been long sought for heavy metal ions wastewater treatment. In this study, a highly monodispersed polyethylenimine-chitosan (PEI-CS) biosorbent, synthesized by an integrated process with facile microfluidic emulsion, chemical crosslinking, solvent extraction and chemical modification, was used as an efficient adsorbent to remove heavy metal ion from contaminated water. The as-prepared biosorbents demonstrated ultra-high adsorption capacity of 146mgg−1 towards Cu ions, almost triple the performance reported in literature. Besides, PEI-CS biosorbents were also endowed with good mechanical strength, excellent adsorption selectivity towards targeted ion in the presence of other metal ions with different valence states, and high reusability. Therefore, the newly developed PEI-CS biosorbents is a highly promising candidate for wastewater treatment with heavy metal ions.

A highly selective benzildihydrazone based Schiff base chromogenic chemosensor for rapid detection of Cu2+ in aqueous solution

Schiff base sensors have the advantage of being used through easy, fast, cost-effective and reliable optical methods for sensing toxic metal ions in the environment. In this work, a, simple but highly specific benzildihydrazone based smart probe (1E,2E)-1,2-diphenyl-1,2-bis((E)-(pyridin-2-ylmethylene)hydrazono)ethane (L) has been used for colorimetric detection of Cu2+ at physiological pH range. Binding interaction between L and various metal ions has been established by UV–Vis spectroscopic measurements, showing favourable coordination towards Cu2+ and almost no interference with the presence of other metal ions, i.e., Na+, K+, Mg2+, Ba2+, Mn2+, Fe3+, Co2+, Ni2+, Zn2+, Cd2+, Pb2+ Ag+ and Al3+. L exhibited binding-induced colour change from colourless to reddish yellow with a detection limit of 3.66×10−7M, measured by spectroscopic methods, while colorimetric changes could be observed at naked eye for concentrations as low as 2.5×10−6M. L has been successfully applied for the determination of Cu2+ in real samples.

A novel luminescent chemical sensor for the determination of Pb2+ and Cu2+ ions

Silica xerogel surface grafted with aminopropyl (PrNH2) groups was additionally treated by cetyltrimethylammonium bromide (CTAB) surfactant and ascorbic acid (asc) in alkaline solution. This material symbolized as SiO2-PrNH2-CTAB/asc, proved to be a stable luminescent material, exhibited an emission band peaked at 393nm under excitation wavelength 335nm. Time evolution of the band intensity suggests changes of defect concentration on the silica surface owing to modification reaction with alkaline mixture of CTAB and asc. After this treatment the material could serve as a luminescence recognition element revealing selectively Cu2+ cations in presence of other metal ions in solutions. On the other hand, emission spectra excited by wavelength 236nm confirmed selectively presence of Pb2+ and simultaneously Cu2+ cations in aqueous solutions. In this way the luminescent material could play the role of INHIBIT and YES logic gates for both the mentioned cations.

Br-PADAP embedded in cellulose acetate electrospun nanofibers: Colorimetric sensor strips for visual uranyl recognition

In this work, a new visual colorimetric strip based on cellulose acetate nanofiber mats modified by 2-(5-Bromo-2-pyridylazo)-5-(diethylamino) phenol was successfully prepared via electrospinning technology. The prepared colorimetric strip showed high sensitivity towards UO22+ with the yellow-to-purple color change signal. Upon the optimal conditions of solution pH at 6.0 and response time for 80min, the detection limit for UO22+ can reach 50 ppb. Moreover, the strip also exhibited excellent anti-interference ability in the presence of other metal ions. In order to achieve the quantitative detection for UO22+, a color-differentiation map was established, which was prepared from converted H values. Finally, the strip was also used to detect UO22+ in the seawater and showed high sensitivity.

Ca2+ ion sensing by a piperidin-4-one derivative and the effect of β-cyclodextrin complexation on the sensing

In this paper, we report the turn-on fluorescence based Ca2+ ion sensing by an anthracene piperidin-4-one derivative. The compound is obtained using a simple two step synthesis. The compound is characterized using NMR and mass spectral methods. The host-guest complex formation of the compound with β-cyclodextrin is prepared and characterized using fluorescence and 2D ROESY spectroscopy. The compound forms the inclusion complex with a 1:1 stoichiometry. The structure of the host-guest complex is proposed. The Ca2+ ion selectivity of the compound in its free form and cyclodextrin-bound forms are studied. In both the forms, the piperidin-4-one derivative senses Ca2+ and in the case of the cyclodextrin encapsulated form it shows a better competitive binding of Ca2+ in the presence of other metal ions.

An Electrochemical Sensing Platform for the Trace Level Detection of Copper

The present work is aimed at the development of highly sensitive electrochemical sensor based on immobilization of 1-phenyl-N-(thiophen-2-ylmethyl)ethanamine (PTE) on glassy carbon electrode (PTEGCE) for the detection of cupric ions (Cu2+), employing electrochemical impedance spectroscopy (EIS) differential pulse anodic stripping voltammetry (DPASV) and square wave anodic stripping voltammetry (SWASV). Several experimental parameters were optimized including concentration of the modifier, pH, and scan rate, number of cycles, accumulation time, deposition potential and supporting electrolytes. The designed sensor showed nice voltammetric response in media of different pH, demonstrated good percentage recoveries and exhibited remarkable electrocatalytic activity. The designed sensor was also not interfered much by the presence of other metal ions. A wide linear range with very low limit of detection as compared to the reported methods reveal the applicability of our designed sensor as a preferred analytical tool. The limit of detection as low as 0.11 nM was obtained using PTEGCE. We expect that these results will let the chemists to apply this sensor for various metallic, organic and organometallic toxins with slight modification.

Simultaneous removal of Pb(II), Cd(II) and Cu(II) from aqueous solutions by adsorption on Triticum aestivum - a green approach

The presence of heavy metals in industrial effluents as a single component is generally very rare. The present study provides information about adsorption behaviour of lead, cadmium and copper in single and multi-component system using triticum aestivum (wheat straw) as adsorbent. It has been shown that adsorption of a certain metal ion is greatly affected by the presence of other metal ions. Effects of process parameters (adsorbent dose, contact time, pH, agitation speed etc.) have been studied. pH 4-6 have been found suitable for metal removal. Adsorption mechanism has been evaluated using five adsorption isotherm models (Langmuir, Freundlich, Temkin, Harkin- Jura and Halsey Isotherms). Removal of cadmium in multi-component system is greater as compared in single component system indicating the metal competition for adsorption sites. Kinetic and thermodynamic parameters have also been calculated and obtained results were found closely related to the reported literature. Positive values of ?H° for lead, cadmium and copper shows feasibility of the process and the spontaneous nature of adsorption.

Highly fluorescent silver oxide/C- dots nanocomposite as selective and sensitive probe for highly efficient detection of Fe(III) ions

Well crystalline Ag2O/C- dots quasispherical nanoparticles were synthesized by facile hydrothermal process assisted photo reaction. These were characterized in detail in terms of their morphological, structural, compositional and optical properties by UV–vis spectroscopy, Fourier transformation infra-red spectroscopy (FTIR), Photoluminescence (PL), Powder X-ray diffraction (XRD), Transmission electron microscopy (TEM), Field Emission Scanning electron microscopy (FESEM) X-ray photoelectron spectroscopy (XPS) and Dynamic light scattering (DLS). These hydrophilic nanoparticles exhibit excellent photostability even after a month. The obtained Ag2O/C- dots exhibited a prominent emission at the wavelength of 455nm, at optimum excitation wavelength of 370nm. The quenching of fluorescence intensity Ag2O/C- dots upon addition of Fe3+ ions prompted to develop susceptible method for quantifying the presence of Fe3+ ions in aqueous medium. With optimized conditions, the fluorescence intensity versus concentration of Fe3+ ions gave a linear correlation, as per Stern–Volmer equation. The linear range from the calibration curve and the limit of detection were found to be 0.09–1.66μM and 2.5nM, respectively. It was noteworthy to mention that the synthesized Ag2O/C- dots exhibit promising capability to be used as fluorescent probes for determination of Fe3+ ions in aqueous solutions, which is not interfered by the presence of other metal ions.

Bay Functionalized Perylenediimide with Pyridine Positional Isomers: NIR Absorption and Selective Colorimetric/Fluorescent Sensing of Fe3+ and Al3+ Ions.

Bay functionalized perylene diimide substituted with pyridine isomers, (2-pyridine (2HMP-PDI), 3-pyridine (3-HMP-PDI) and 4-pyridine (4-HMP-PDI)) have been synthesized and explored for selective coloro/fluorimetric sensing of heavy transition metal ions. HMP-PDIs showed strong NIR absorption (760-765nm) in DMF. The absorption and fluorescence of HMP-PDIs have been tuned by make use of pyridine isomers. Reddish-orange color was observed for 2-HMP-PDI (λmax=437, 551, 765nm) whereas 4-HMP-PDI exhibited light green (λmax=432, 522, 765nm). 3-HMP-PDI showed orange-yellow (λmax=431, 524, 762nm). The fluorescence spectra of 2-, 3- and 4-HMP-PDI showed λmax at 585, 538, 546nm, respectively. Interestingly, HMP-PDI dyes showed selective color change (intense pink color) and fluorescence quenching for Fe3+ and Al3+ metal ions in DMF. Absorbance spectra revealed complete disappearance of NIR absorption and intensification/appearance of new peak at lower wavelength. The concentration dependent studies suggest that 4-HMP-PDI can detect up to 36.52ppb of Fe3+ and 43.12ppb of Al3+ colorimetrically. The interference studies in presence of other metal ions confirmed the good selectivity for Fe3+ and Al3+. The mechanistic studies indicate that Lewis acidic character of Fe3+ and Al3+ ions were responsible for selective color change and fluorescence quenching.

Novel reversible fluorescent probe for relay recognition of Zn2+ and PPi in aqueous medium and living cells

Abstract A new fluorescent probe 4′-hydroxy-3′-((8-quinolineimino) methyl)-4-biphenylcarbonitrile (L) has been synthesized for the sequential detection of Zn 2+ and PPi in aqueous ethanolic (3/2 v/v) HEPES buffer (pH 7.1). Addition of Zn 2+ to the solution of L resulted in a red shift (Δλ = 18 nm) with a pronounced enhancement in the fluorescence intensity, while there was no enhancement in presence of other metal ions. The subsequent addition of PPi anion can switch off the fluorescence signal by bringing the Zn 2+ ion out of the coordination cavity of the chemosensor L. No interference was observed from other anions, making the L–Zn 2+ ensemble a highly sensitive and selective PPi probe. The detection limit is 5.31 × 10 −8 M and 9.41 × 10 −8 M for Zn 2+ and PPi, respectively. The sensing process is reversible and the probe may be recycled for further use. Cell imaging studies demonstrate that this sensor is capable of sensing Zn 2+ and PPi in living cells.

Reversible ‘turn off’ fluorescence response of Cu2+ ions towards 2-pyridyl quinoline based chemosensor with visible colour change

A novel chemosensor, 4(1H-benzo[d]imidazol-2-yl)-2-(pyridin-2-yl)quinoline is described which could selectively detect Cu2+ ions. Addition of Cu2+ ions changes solution of chemosensor from colourless to yellow which is clearly visible to the naked eyes. Fluorescence of chemosensor was quenched by 18 folds in presence of Cu2+ ions. Cu2+ ions sensing property of chemosensor was remained unaffected in presence of other metal ions (Na+, Mg2+, K+, Mn2+, Ca2+, Fe2+, Co2+, Zn2+, Cd2+, Ba2+, Hg2+ and Pb2+). Moreover, the sensing of Cu2+ was found to be reversible, since the Cu2+ induced quenching of emission spectra was reversed upon addition of EDTA. The stoichiometry of binding of chemosensor and Cu2+ was determined by Job‘s plot which was found to be 1:1 and further it was confirmed by ESI-MS analysis. Binding of Cu2+ ions to chemosensor was studied over the wide pH range and the result demonstrated maximum fluorescence quenching in the pH range of 3.0–10. The binding association constant (Ka) value determined from Benesi–Hildebrand equation was 3.38×105M−1.

A novel thiophene functionalized silicon-cored compounds: Aggregation-induced emission enhancement and aqueous fluorogenic Fe3+ probes in bovine serum albumin

“Silicon-cored” compounds are well known for their high value glass transition temperature, high thermal stability and excellent optical properties, but the excellent optical properties was not used for fluorogenic probes especially for Fe3+ probe. In this paper, a novel Fe3+ probe based on thiophene functionalized silane, namely, bis[3,4-diphenyl-2,5-di(2-Thienyl)phenyl]methylphenylsilane (MPS) was designed and synthesized. MPS exhibits aggregation-induced emission enhancement (AIEE) property in water/tetrahydrofuran mixtures because of restricted intramolecular rotation. The abnormal optical properties enable MPS to detect Fe3+ in aqueous-based solutions. The binding behavior of MPS aggregates to Fe3+ and other transition metal ions were studied through UV–vis, fluorescence spectroscopy, and scanning electron microscopy. Exceptional fluorescence quenching of MPS occurred during Fe3+ binding. The calculated detection limit was at ppb level, and the complex ratio of MPS to Fe3+ is approximately 1:1. MPS has both exemplary activity and high selectivity toward Fe3+ even in the presence of other metal ions. The test conditions were also expanded from water to bovine serum albumin and solid films. This study was an advancement for the application of “silicon-cored” compounds and provides guidance for using simple, low-cost, and high-selectivity Fe3+ probes in aqueous solutions and in clinical applications.

Study of the AlS4Pc-Polylysine Ion Pair, a Red-Fluorescent Probe: Its High Specificity, Large Concentration Range Response to Bismuth Ion, and Application.

Tetrasulfonated aluminum phthalocyanine (AlS4Pc), a strongly red-emitting compound, shows high detection sensitivity, little effect of photobleaching, and photochemical stability, making it an excellent red-fluorescent probe. We have observed that in acid media, a low concentration of poly-L-lysine (PLL) has a strong fluorescence-quenching effect on AlS4Pc, forming the ion-pair complex as AlS4Pc-PLL with almost no fluorescence. However, in the presence of Bi3+, the fluorescence of AlS4Pc-PLL dramatically recovers and the emission is visual because of the remarkable recovery. Screening experiments with other metal ions reveal that only Bi3+ can restore the fluorescence of the AlS4Pc-PLL complex. The presence of other metal ions does not result in the recovery of fluorescence, indicating the high specificity of the response to Bi3+ of AlS4Pc-PLL. This is the key finding of the present study. It was also observed that the response to Bi3+ of AlS4Pc-PLL exhibits a linear relationship over a large concentration range (three orders of magnitude). Based on these findings, we have established a new quantitative analysis method for Bi3+ with high specificity and high sensitivity, using the ion-pair AlS4Pc-PLL complex as a red-fluorescent probe, and we discuss the reaction mechanism. The detection limit of this method is 0.0021 mg L-1 The linear relationship applies to the range of 0.007-34.9 mg L-1 with a correlation coefficient of 0.9993. The method established addresses the complex operation and time-consuming problems in traditional methods and is thus suitable for real applications. Satisfactory results have been obtained when the method was applied to the measurement of real samples. This study further expands the scope of new applications of phthalocyanine-based red-fluorescent probes in analytical sciences.

2H1NA/β-cyclodextrin inclusion complex: Preparation, characterization and chemosensory application for detecting Ag+

ABSTRACTThe inclusion complex of 2-hydroxy-1-naphthoic acid (2H1NA) with β-cyclodextrin (β-CD) has been investigated using UV-visible and fluorescence spectral techniques in liquid states, FTIR, NMR, XRD and SEM techniques in solid state, molecular docking techniques in virtual states. The binding constants of for the formation of 1:1 2H1NA:β-CD inclusion complex is estimated by UV-visible and fluorescence spectral techniques. The chemosensory power of 2H1NA:β-CD complex was investigated thoroughly for various metal cations and we found the emission of complex showed a drastic increase in the intensity for Ag+. Competition experiments of 2H1NA:β-CD complex with Ag+ in presence of other metal ions (Na+, K+, Hg+, Al2+, Ca2+, Ba2+, Cd2+, Co2+, Fe2+, Hg2+, Mg2+, Mn2+, Ni2+, Pb2+, Sn2+, Ti2+, Zn2+, Cr3+, Fe3+) showed that no significant variation was found in the fluoresce intensity of 2H1NA:β-CD complex upon adding all other cations. The linearity range, LOD and LOQ are determined from the selectivity and sensitivity studies for Ag+. Our result suggests that the 2H1NA:β-CD inclusion complex would be promising material for developing solid state sensory device for sensing Ag+.