Corrigendum to 'Exploration of the adsorption capability by doping Pb@ZnFe2O4 nanocomposites (NCs) for decontamination of dye from textile wastewater' [Heliyon, 5(2019) 2412].

[This corrects the article DOI: 10.1016/j.heliyon.2019.e02412.].

High-Selectivity Hydrogen Gas Sensors based on Mesoporous PbOx -ZnO Nanocomposites.

Hydrogen heralded as a promising renewable and environmentally friendly energy carrier, carries inherent risks owing to its highly flammable nature. A mere 4 % concentration of hydrogen in the air can trigger an explosion. To counteract this peril, a composite material comprising PbOX -ZnO (2 : 1) was synthesized, characterized, and subsequently employed to fabricate a hydrogen sensing device. Various analytical tools were used to characterize as-deposited materials, including X-ray diffraction, Scanning electron microscopy /Energy Dispersive X-ray Spectroscopy, Transmission electron microscopy UV-Vis Reflectance Spectroscopy and Fourier-transform infrared spectroscopy. The device exhibited favorable properties, such as good selectivity, stability, and a low detection limit for hydrogen. At ambient room temperature, the device demonstrated a sensing signal reaching 468.7, with a response time (T90) of 155 seconds and a recovery time (Tr90) of 69 seconds when exposed to a hydrogen concentration of 5 ppm. This performance underscores the device's rapid and effective response to hydrogen exposure. Moreover, the PbOX-ZnO (2 : 1) composite-based device exhibited a detection limit of 2.4 ppm, functioning accurately within a linear range spanning from 5 ppm to 50 ppm. This capability confirms its precision in accurately detecting hydrogen concentrations within this designated range.

A colorimetric chemosensor for distinct color change with (E)-2-(1-(3-aminophenyl)ethylideneamino)benzenethiol to detect Cu2+ in real water samples.

The study reports the synthesis of chemosensor (E)-2-(1-(3-aminophenyl)ethylideneamino)benzenethiol (C1), a highly sensitive, colorimetric metal probe that shows distinct selectivity for the detection of Cu2+ ion in various real water samples. Upon complexation with Cu2+ in CH3OH/H2O (60:40 v/v) (aqueous methanol), the C1 demonstrate significant enhancement in the absorption at 250 nm and 300 nm with a color change from light yellow to brown which was visualized using naked-eye. Therefore, these properties make C1 as an effective candidate for on-site Cu2+ ions detection. The emission spectrum of C1 illustrated "TURN-ON" recognition of Cu2+ with a limit of detection (LOD) of 46 nM. Furthermore, Density Functional Theory (DFT) calculations were performed to better understand the interactions between C1 and Cu2+. The obtained results suggested that the electron clouds present around the -NH2 in nitrogen and sulfur in -SH play a pivotal role in the formation of a stable complex. The computational results were in good agreement with the experimental UV-visible spectrometry results.

Statistical physics double-layer models for the experimental study and theoretical modeling of methyl orange dye adsorption on AlMnTiO nanocomposite.

A Al2O3/MnO2/TiO2 (AlMnTiO) nanocomposite was synthesized using the thermal coprecipitation method and the adsorption performance of methyl orange (MO) dye from aqueous solution was carried out. Single-parameter optimization was used to explore the properties of AlMnTiO nanocomposite parameters on dye adsorption, including dose of adsorbent, solution pH, contact duration, and starting MO concentration. The model is the appropriate adsorption isotherm for the equilibrium process using a pseudo-second-order kinetic model property. Langmuir plot had a Qmax (mg/g) of 198.4 and best fitted (R2=0.990) among different isotherm models. The relevant parameters were computed using the dual-energy binary-layer statistical physics model. The statistical physics binary-layer model yield n (stoichiometric coefficient) values of 0.410, 0.440, and 0.453, all values are below 1, demonstrating the multi-docking process. AlMnTiO nanocomposite was regenerated up to six times, making the material extremely cost-effective. Using AlMnTiO nanocomposite, MO dye was removed from wastewater both in the laboratory and on the industrial scale.

A Colorimetric Distinct Color Change Cu(II) 4-{[1-(2,5-dihydroxyphenyl)ethylidene]amino}-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one Chemosensor and its Application as a Paper Test Kit.

In the current research work "4-{[1-(2,5-dihydroxyphenyl)ethylidene]amino}-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one" chemosensor (C1) synthesized by condensation reaction using "4-amino-1,2-dihydro-1,5-dimethyl-2-phenylpyrazol-3-one" and "2,5-dihydroxy actophenone" was used as the effective sensor of metal ion. The C1 shows absorption peak at 326 nm due to the C = C bond (π-π* transition), while the absorption peak at 364 nm is caused by the C = O bond (n-π* transition). In the presence of copper, C1 only demonstrated a redshift in absorption peak from 364 to 425 nm. Even in the presence of other competing metal ions, the hypsochromic shift of the absorption band and the quenching of the fluorescence emission intensity were different for detecting Cu2+, in CH3OH-H2O (v/v = 6:4). The capacity of the C1 to bind with Cu2+ was further proved using DFT simulations. The complex C1 + Cu2+ has a HOMO-LUMO energy gap of 2.8002 eV, which is lesser than C1 (2.9991 eV) showing improvement in the stability of the C1 + Cu2+ complex. Using the Benesi-Hildebrand and Scatchard plots, calculated Kb values were to be 47,340 and 48369 M-1 respectively, showing the creation of stable complexation between Cu2+ and C1 with 1:1 stoichiometry. The limit of detection (LOD) for Cu2+ ion was 649 nM. Strip sheets were also built and tested to detect varying amounts of Cu2+ in aqueous solution, and their color change suggested that they might be used for on-site Cu2+ detection in polluted water.

Adsorption of Magenta Dye on PbO Doped MgZnO: Interpretation of Statistical Physics Parameters Using Double-Layer Models.

This article reports the synthesis of PbO doped MgZnO (PbO@MgZnO) by a co-precipitation method, followed by an ultrasonication process. PbO@MgZnO demonstrates a significant adsorption capability toward Magenta Dye (MD). The greatest adsorption capability was optimized by varying parameters such as pH, MD concentration, and adsorbent dose. The kinetics study illustrates that the adsorption of MD on PbO@MgZnO follows the pseudo-second-order. The isotherm study revealed that Langmuir is best fitted for the adsorption, but with little difference in the R2 value of Langmuir and Freundlich, the adsorption process cloud be single or multi-layer. The maximum adsorption capacity was found to be 333.33 mg/g. The negative ΔG refers to the spontaneity of MD adsorption on PbO@MgZnO. The steric parameters from statistical physics models also favor the multi-layer adsorption mechanism. As a function of solution temperature, the parameter n pattern has values of n = 0.395, 0.290, and 0.280 for 298, 308, and 318 K, respectively (i.e., all values were below 1). Therefore, horizontal molecule positioning and multiple locking mechanisms were implicated during interactions between MD and PbO@MgZnO active sites.

Adsorption of Congo Red on Pb doped FexOy: experimental study and theoretical modeling via double-layer statistical physics models.

Size-controlled Pb0.06Fe0.7O3 nanoparticles (Pb-FeONPs) were fabricated by the thermal co-precipitation method and characterized by FE-SEM, EDX, XRD, and IR techniques. The SEM and XRD images showed the average size distribution and average crystallite size of 19.21 nm and 4.9 nm, respectively. The kinetic model of Congo Red (CR) adsorption onto Pb-FeONPs was verified and found to be a pseudo-second-order reaction. The Langmuir plot was better fitted (R2 = 0.990) than other isotherm models with a Qmax (mg/g) of 500 for Congo Red (CR) dye in 40 min. The double-layer statistical physics model based on two energies was used to calculate the significant parameters. The n (stoichiometric coefficient) values obtained from the statistical physics double-layer model were found to be 0.599, 0.593, and 0.565, which are less than 1, indicating the multi-docking process. The regeneration of Pb-FeONPs was used for up to 5 cycles effectively, making the material highly economical. The Pb-FeONPs were fruitfully applied for the removal of CR dye from wastewater on a laboratory and industrial scale.

A Selective Ratiometric Receptor 2-((E)-(3-(prop-1-en-2-yl)phenylimino)methyl)-4-nitrophenol for the Detection of Cu2+ ions Supported By DFT Studies.

A Schiff-base 2-((E)-(3-(prop-1-en-2-yl)phenylimino)methyl)-4-nitrophenol (Receptor 1) colorimetric probe was synthesized and its UV-visible and fluorescence spectral properties for the sensing of Cu+ 2 ions in CH3OH/H2O (60:40,v/v) solvent system was explored. The Receptor 1 showed the discriminating spectral behavior with the addition of Cu2+ ions solution. The other metal ions showed no significant effect towards Receptor 1. Moreover, the addition of Cu2+ ions to the Receptor 1 demonstrated the shift in the peak towards longer wavelength of 405 nm due to the ligand to metal charge transfer (LMCT) effect. The red-shift and new peak at 405 nm are due to the deprotonation of the -OH group and formation of complex and O-Cu covalent bond, respectively. A slight increase in the Cu2+ ion concentration exhibited strong absorption and fluorescence properties, leading to the spontaneous change in color from pale yellow to orange. Additionally, Density Functional Theory (DFT) studies were performed to investigate the interaction of Cu2+ ions with Receptor 1. The decrease in the energies (3.59062 kcal/mol to 0.36028 kcal/mol) of Cu2+-Receptor-1 complex compared to Receptor 1 confirms the strong interaction with high stability. The association constant (Ka) of Cu2+-Receptor-1 complex was found as 175000 M- 1. The limit of detection (LOD) was calculated and noted as 179 nM.

A Mini Review on Organic Chemosensors for Cation Recognition (2013-19).

Colorimetric and ratiometric fluorescent probe for cations gain very well attention by the chemist, biologist and environmentalist. Metals has two sides, first is biolgical active for living creature and toxic nature for the ecosystem. From last three decades the scientists are contiously trying to find out the best solution for the detection of cations at micro as well as nanomolar levels. In the present review we discussed the colorimetric and ratiometric fluorescent probe synthesized by the authors in almost half decade.

Corrigendum to "Exploration of the adsorption capability by doping Pb@ZnFe2O4 nanocomposites (NCs) for decontamination of dye from textile wastewater" [Heliyon Volume 5, Issue 9, September 2019, e02412].

[This corrects the article DOI: 10.1016/j.heliyon.2019.e02412.].

Exploration of the adsorption capability by doping Pb@ZnFe2O4 nanocomposites (NCs) for decontamination of dye from textile wastewater.

In the present research article we explore the synthesis method and adsorption capability of ZnFe oxides nanocomposites by using Pb as dopant. A conventional and simple batch adsorption method is selected and optimized. Pb@ZnFe2O4 NCs were fabricated by facile method i.e. co-precipitation method and characterized by FESEM, XRD, IR, EDX. The removal of dye has monitored by UV method. An outstanding result is obtained as adsorption efficiency of 1042 mg g-1 shows more significant performance than currently available bench-mark adsorbents. The optimized parameters pH 7.1, Adsorbent Mass: 50 mg, Initial Dye Concentration: 150 mg/l and Agitation Time: 90 min results in 96.49 % removal of CR (Congo red) dye. A CCD (central composite design) is applied to evaluate the role of adsorption variables. Based on its excellent performance, cost effectiveness, facile fabrication and large surface area, the Pb@ZnFe2O4 has considerable potential for the manufacture of cost effective and efficient adsorbents for environmental applications.

Fluorescence Chemosensor for HSO4 (-) Ion Based on Pyrrole-Substituted Salicylimine Zn (2+) Complex: Nanomolar Detection.

A novel pyrrole-substituted salicylimine zinc (II) ion complex has been synthesized and evaluated its anion binding affinity. The probe 4 has high selectivity for HSO4 (-) over other anions in CH3OH:H2O (70:30, v/v) solvent system. The emission intensity of 4 was quenched upon addition of HSO4 (-). The probe 4 is highly selective for HSO4 (-) with a detection limit of 40 nm. Photoinduced electron transfer (PET) is responsible for observed change. The binding affinity of 4 for HSO4 (-) was further authenticated through ratiometric change in absorbance profile.

A chemosensor showing discriminating fluorescent response for highly selective and nanomolar detection of Cu²âº and Zn²âº and its application in molecular logic gate.

A fluorescent based receptor (4Z)-4-(4-diethylamino)-2-hydroxybenzylidene amino)-1,2dihydro-1,5-dimethyl-2-phenylpyrazol-3-one (receptor 3) was developed for the highly selective and sensitive detection of Cu(2+) and Zn(2+) in semi-aqueous system. The fluorescence of receptor 3 was enhanced and quenched, respectively, with the addition of Zn(2+) and Cu(2+) ions over other surveyed cations. The receptor formed host-guest complexes in 1:1 stoichiometry with the detection limit of 5 nM and 15 nM for Cu(2+) and Zn(2+) ions, respectively. Further, we have effectively utilized the two metal ions (Cu(2+) and Zn(2+)) as chemical inputs for the manufacture of INHIBIT type logic gate at molecular level using the fluorescence responses of receptor 3 at 450 nm.

Pyrrole-coupled salicylimine-based fluorescence "turn on" probe for highly selective recognition of Zn²âº ions in mixed aqueous media: Application in living cell imaging.

Cation sensing behaviour of a pyrrole-based derivative (2-hydroxyl 3 methyl 6 isopropyl benzaldehyde}-3,4-dimethyl-1H-pyrrole-2-carbohydrazide (receptor 3) has been explored and is found to be selective towards Zn(2+) over a variety of tested cations. The receptor 3 has shown high selectivity and sensitivity towards Zn(2+) over the other alkali, alkaline earth and transition metal ions. In the presence of Zn(2+), absorption band of receptor 3 has shown the red shift. The sensing behaviour has been suggested to continue via enhancement process which has further been supported by UV-vis absorption and theoretical density functional theory (DFT) calculations indicating the formation of a 1:1 complex between the pyrrole based receptor 3 and Zn(2+). The present work is presenting a highly selective dual channel colorimetric sensor for zinc with great sensitivity. The developed sensor was successfully applied to image intracellular Zn(2+) in living cells.

A novel phthalazine based highly selective chromogenic and fluorogenic chemosensor for Co(2+) in semi-aqueous medium: application in cancer cell imaging.

A new phthalazine based chemosensor was developed for the highly selective and sensitive detection of Co(2+) in the mixed solvent system, CH3CN-H2O (1 : 1, v/v). In the presence of Co(2+), the colour of the solution changed from yellow to green; the absorption maxima of was red-shifted from 383 nm to 435 nm, and the fluorescence of at 550 nm was significantly enhanced. The sensor showed a detection limit down to 25 nM by forming a complex species with Co(2+) in 1 : 1 stoichiometry. Furthermore, by means of confocal laser scanning microscopy experiments, it has demonstrated that it can be used as a fluorescent probe for monitoring Co(2+) in living cells.

Highly sensitive ratiometric chemosensor for selective 'naked-eye' nanomolar detection of Co(2+) in semi-aqueous media.

An easy-to-prepare chemosensor, (E)-1-(phthalazine-4-yl)-2-(1-(pyridine-2-yl)ethylidene) hydrazine (3), structurally characterized by single X-ray crystallography, is developed for the selective and sensitive detection of Co(2+) in aqueous media. Chemosensor 3 shows both absorption and fluorescence responses to Co(2+) by forming a 1:1 complex (among the surveyed metal ions) with a detection limit down to 50 nM. It can also be used as a 'naked-eye' sensor due to the outstanding visible and emission color changes from yellow to red and blue to orange, respectively.

"Turn-on" fluorescent dipodal chemosensor for nano-molar detection of Zn(2+): application in living cells imaging.

A malonohydrazide derivative bearing an imine and phenolic group was synthesized and had a high affinity and selectivity towards Zn(2+). The recognition properties of receptor 1 were evaluated using absorbance and fluorescence spectroscopy. The 1:1 stoichiometry of 1.Zn(2+) was confirmed from job's plot, mass spectra and density functional theory (DFT). The detection of Zn(2+) in intracellular environment of HeLa cell through confocal microscopy was successfully applied for live cell imaging.

Fluorescent and chromogenic receptor bearing amine and hydroxyl functionality for iron (III) detection in aqueous solution.

The noncyclic 2,2'-[ethane-1,2-diylbis (iminomethanediyl)]diphenol (4) fluorescent receptor bearing two amine and hydroxyl groups have been designed and investigated for their binding properties towards various cations. The fluorescent spectral measurements revealed that receptor 4 is a selective fluorescent sensor for Fe(3+) ions but not for metal ions such as Cr(3+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), Pb(2+) and Bi(3+). The binding ability was confirmed with spectroscopic methods and density functional theory calculation (DFT). This straightforward and cost effective receptor provides rapid detection of Fe(3+) ions at concentrations as low as 2.5 µM and expected to be useful to design efficient chemically and biological sensor.

Highly selective and sensitive receptor for Fe3+ probing.

A new fluorescent receptor 1,1'-(4-methylbenzene-1,3-diyl)bis[3-(2-sulfanylphenyl)urea] (1) has been designed and synthesized. The receptor showed excellent selectivity for Fe(3+) in DMSO/H2O (8:2, v/v) solvent system over other commonly coexistent metal ions. The binding constant (Ka) of receptor with Fe(3+) was calculated to be 11,250 M(-1), 12,970 M(-1) and 12,970 M(-1) using Benesi-Hildebrand, Scatchard and Connor plot, respectively. The experimental results have been further supported by the detailed DFT calculations.

Al3+ selective colorimetric and fluorescent red shifting chemosensor: application in living cell imaging.

We report the development of a fluorescent probe based on the benzothiazole unit to monitor intracellular Al(3+) levels in living cells. The fluorescent probe exhibits a fluorescence response towards Al(3+) under physiological conditions with high sensitivity and selectivity and even facilitates naked-eye detection of Al(3+). The fluorescence intensity was significantly quenched with red shifting upon addition of 0.5 equiv. of Al(3+). The simple and cost effective receptor avails rapid detection of Al(3+) ions at concentrations as low as 0.42 µM and is expected to be effective for the design of efficient biological sensor.