Ions In Aqueous Media Research Articles

Electrochemical detection of mercuric(ii) ions in aqueous media using glassy carbon electrode modified with synthesized tribenzamides and silver nanoparticles.

This study reports the synthesis, characterization, and mercuric ion detection ability of novel tribenzamides having flexible and rigid moieties. N-{4-[2-(1,3-Benzoxazolyl)]phenyl}-3,5-N,N′-bis(4-alkyloxybenzoyl)benzamides (TBa-TBc) were synthesized from newly synthesized diamine, N-(1,3-benzoxazol-2-yl-phenyl)-3,5-diaminobenzamide (BODA) and p-alkoxybenzoic acids (p-ABA) by amidation reaction. Structural characterization of the synthesized compounds was done through spectroscopic techniques (FT-IR and NMR). The synthesized tribenzamides along with silver nanoparticles were used for modification of a glassy carbon electrode. Square wave anodic stripping voltammetry was carried out to test the performance of the modified electrode for mercuric ion detection. The designed sensor was found to demonstrate the qualities of sensitivity, selectivity, reproducibility and anti-interference ability. The sensing platform helped in detecting femtomolar concentrations of mercuric ions which are much below the level declared toxic by the World Health Organization.

A phenazine-imidazole based ratiometric fluorescent probe for Cd2+ ions and its application in in vivo imaging.

A new phenazine-imidazole based Schiff base (PIS) fluorescent probe has been developed for the ratiometric detection of Cd2+ ions in aqueous media at physiological pH. PIS upon binding with Cd2+ ions shows red shifted fluorescence and thereby, permits ratiometric detection of Cd(II) ions. A detection limit down to 2.10 × 10-8 M was determined for Cd2+ quantitation. Also, the accompanying apparent fluorescence color change (from yellow to orange red) is noticeable to the naked eye under a UV-lamp. The sensing mechanism could be attributed to the 1 : 1 PIS-Cd complexation, followed by extension of the conjugation due to better planarity and modulation of the charge transfer efficiency in the probe. This was complemented by solvatochromism and density functional theory calculations. Furthermore, PIS was used to detect Cd2+ in Oxya chinensis cells, zebrafish larvae and live tissues of Arabidopsis thaliana under a fluorescence microscope, showing great potential in analyzing living biosystems.

Comparative 4f-4f Spectral Analysis of Simultaneous Complexation of Pr(III) with L-Tryptophan in Presence and Absence of Ca2+ and Zn2+ Ions in Aqueous Medium: Energy, Intensity and Kinetic Studies

The spectral analysis of the complexation of praseodymium (Pr3+) with L-tryptophan in various aqueous solvent applying a quantitative probe of 4f-4f transition spectra. The study is carried out by calculating various energy interaction parameters such as the nephelauxetic effect (β), percent covalency (δ), bonding parameter (b1/2), Slater-Condon (Fk) and intensity parameters like oscillator strength (P) and intensity of Judd-Ofelt parameters Tλ (λ = 2, 4, 6). The paramagnetic behaviour of Pr3+ shows 3H4→1D2, 3H4→3P0, 3H4→3P1, 3H4→3P2 types of specific 4f-4f absorption bands and are observed at the visible reason of 427-610 nm. The intensities of 4f-4f transition bands rise on the addition of Ca2+ and Zn2+ ions toward the complexation of praseodymium (Pr3+):Try and extended result in the case of Ca2+ ion compared to the Zn2+ ion due to increase in the interaction between ligand and 4f orbital of metal ions. These bands on immediate minor’s coordination change around praseodymium (Pr3+) found to be highly sensitive due to the formation of heterobimetallic complex between L-tryptophan (Try) with Pr3+ in the existence of Zn2+ and Ca2+ ions. The complexation of Try with Pr3+ in the presence of Zn2+ and Ca2+ ions are monitors simultaneously from the sensitivity of the bands using energy parameters and oscillator strength. The rate of heterobimetallic complexation of both Zn2+ and Ca2+ ions was calculated from the 4f-4f transition at different temperatures. The thermodynamic parameters and activation energy calculated from the rate constants from different temperatures are more favourable in case of Try form complex with Pr3+ in the presence of Ca2+ ion as compared to Zn2+ ion.

Multiple heteroatom-doped photoluminescent carbon dots for ratiometric detection of Hg2+ ions in cell imaging and environmental applications.

Photoluminescence detection and imaging of Hg2+ ions in the biochemical living system are of great importance. In this study, a new photoluminescent probe based on nitrogen (N), sulfur (S), and boron (B) multiple heteroatom co-doped carbon dots (NSB-CDs) is synthesized for the ratiometric detection of Hg2+ ions. The prepared NSB-CDs possess good aqueous solubility, excellent pH and ionic stability, excitation dependency, and high quantum yield (QY = 17.6%). The ratiometric photoluminescent sensor NSB-CDs exhibit high selectivity, sensitivity, and interference towards Hg2+ ions over other metal ions. After adding Hg2+ ions, the emission intensity of the NSB-CDs exhibits a large redshift from 452 to 496 nm (up to 44 nm), corresponding to a notable change from blue to green emission in aqueous solutions. The association constant (Ka), the limit of detection (LOD), and the limit of quantification (LOQ) for NSB-CDs/Hg2+ complex are calculated to be 3.6 × 104 M-1, 3.1 × 10-9 M, and 10.4 × 10-9 M, respectively, in the range of 0-30 × 10-6 M. The live cell bioimaging of HCT-116 cells with NSB-CDs validates the application of multicolor imaging for the detection of Hg2+ ions in aqueous media and biological systems. Moreover, the potential use of the NSB-CDs/Hg2+ complex for real sample analysis is demonstrated.

Schiff bases bearing amino acids for selective detection of Pb2+ ions in aqueous medium

Lead toxicity is the never-ending and everyday growing problem of the world. It is reported to be a life-threatening poison for infants and children. Although the number of receptors are reported in the literature the wildness of toxicity is intense, which is somewhat like the ever-increasing gap between demand and supply. The C1 (2-[(5-Bromo-2-hydroxy benzylidene)-amino]-3 -(1H-imidazol-4-yl)-propionic acid) and C2 (2-Amino-5-[N'-(5-bromo-2-hydroxy-benzylidene)-guanidino]-pentanoic acid) were prepared to test their capability as lead (Pb) sensors. The probes C1 and C2 were synthesized by treating bromo salicylaldehyde with amino acids histidine and arginine at room temperature. The Schiff bases formed show significant binding with Pb2+ions in the aqueous medium. The lowest detection limit is 20 ng/ml of both sensors. As lead toxicity is fatal to infants and kids and both amino acids viz., arginine and histidine are a common component of total parental nutrition in infants and kids. Thus, amino acids substituted C1-C2 probes are of great significance for the development of molecular drugs to treat lead poisoning especially in infants, and extensively for the human body.

Sensing Cd(II) Using a Disposable Optical Sensor Based on a Schiff Base Immobilisation on a Polymer-Inclusion Membrane. Applications in Water and Art Paint Samples.

A disposable colour-changeable optical sensor based on an interesting polymer inclusion-membrane (PIM) was designed to determine Cd(II) ions in aqueous medium. The Schiff base 2-acetylpyridine benzoylhydrazone (2-APBH) immobilised on the polymer membrane was used as a sensing molecule. The amounts of the PIM components were optimised by a 32 fractional factorial design with two central points and two blocks. The best optical sensor composition consisted of 2.5 g of poly(vinylchloride) (PVC) as a base polymer, 3 mL of tributyl phosphate (TBP) as a plasticiser, and 0.02 g of 2-APBH as a reagent. The sensor showed a good linear response in the range from 0.02 mg L−1 (limit of detection) to 1 mg L−1 of Cd(II) under the following experimental conditions: pH 9.5 (adjusted using ammonium chloride buffer solution at 0.337 mol L−1), 60 min of exposure time plus 2 min of sonication (pulses at 2 s intervals), and 10 min of short-term stability. The relative standard deviation of the method was determined to be 4.04% for 0.4 mg L−1 of Cd(II). The optical sensor was successfully applied to the determination of Cd(II) in natural-water and art-paint samples.

Triazole-linked pyrene appended xylofuranose derivatives for selective detection of Au3+ ions in aqueous medium and DFT calculations

The sugar-modified simple fluorometric sensors 1 and 2 for detection of Au3+ in the aqueous acetonitrile have been reported. The sensors are double-responsive (absorbance and fluorescence) selective Au3+ sensors in CH3CN-H2O (1:1, v/v). Both the sensors exhibited remarkable selectivity and excellent sensitivity (limit of detection values are 0.53 µM for 1 and 0.83 µM for 2). The stoichiometry of each complex was established by Job's plot and supported by the ESI-mass spectrum of the complex. Finally, the coordination mode of each sensor with Au3+ ions was supported by DFT calculations in CH3CN-H2O (1:1, v/v) medium. The energy-optimized structures of 1-Au3+ and 2-Au3+ suggested that sensors 1 and 2 followed different binding modes with Au3+ ions in the aqueous acetonitrile medium, which account for the ESI-MS spectra of the complexes. Interestingly, we observed that fluorometric sugar derivatives 1 and 2 did not show any specific selectivity towards metal ions in CH3CN.

Synthesis and characterization of 4-Halobenzylidene malanonitriles for optical detection of Nickel (II) ions in aqueous solution

In this work, we have developed fluorescent detection techniques for the determination of Ni2+ ions in aqueous medium with sensitivity using metal coordinating fluorescent molecules namely 4-Halobenzylidene malanonitrile. The halogen substituted benzylidene malanonitile were synthesised Knoevenagel condensation reaction of various halogen substituted aromatic aldehydes with malanonitrile and products were characterised by IR and NMR spectroscopy. The obtained benzylidene malanonitiles and are exhibited a fluorescent emission with a peak of 430 nm, 440 nm and 448 nm for chloro, bromo and fluoro substituted compounds, respectively. The intensity of optical emission of the studied molecules is increased proportional to the addition of Ni2+ ions. The effect of different halogen substitution on the fluorescence behaviour of benylidene malononitrile has also been investigated. The synthesised title compounds showed a lowest detection limit of 10−20 M for the Nickel (II) ions in aqueous solution under UV–Vis absorption spectra. The molecule 4- Bromobenzylidene malanonitrile exhibited a lowest detection limit of 10−19 M for the Nickel (II) ions in, aqueous solution, photoluminescence analysis.

Morus nigra-derived hydrophilic carbon dots for the highly selective and sensitive detection of ferric ion in aqueous media and human colon cancer cell imaging

Strongly fluorescent hydrophilic carbon dots (CDs) were synthesized through a one-step hydrothermal route using polysaccharide-rich Morus nigra fruit as the carbon source. These Morus nigra CDs (M-CDs) were extensively characterized using various analytical techniques to determine their structural and optical properties. The as-synthesized M-CDs were determined to be monodispersed with a mean diameter of 4.5 nm. Aqueous M-CD dispersions are brownish-yellow in color in daylight and emit bright cyan-blue light upon exposure to ultraviolet light. The M-CDs exhibit typical excitation-dependent emission behavior, with a high quantum yield of 24%. The analytical data show that the as-synthesized M-CDs exhibit strong fluorescence (FLR) and are very optically stable. Hence, the as-synthesized M-CDs are expected to use as fluorescent sensors for the highly selective and sensitive detection of Fe3+ ions by the fluorescence quenching mechanism. The quenching rate was linearly dependent on Fe3+ concentration, with a Fe3+ detection limit of 0.47 μM and a 5–30 µm detection range. Moreover, human colon cancer (HTC-116) cells were stained with the prepared M-CDs for 12 and 24 h for cell viability and microscopic analyses. The M-CDs-conjugated HTC-116 cells were brightly multicolor illuminated, emitting blue, green, and red light when excited through 405-, 488-, and 555-nm filters with distinct excitation ranges, respectively. This study provides a new route for the large-scale synthesis of highly fluorescent CDs for diverse applications using green sources and one-step hydrothermal carbonization procedures.

Fluorene based fluorescent and colorimetric chemosensors for selective detection of cyanide ions in aqueous medium and application of logic gate

Rising detrimental effects of cyanide due to its frequent large-scale utilization demand rapid and sensitive detection of cyanide ions. Herein, two new fluorene based chemosensors 1 and 2 have been developed through the Suzuki–Miyaura coupling reaction for fluorescence enhancement based selective detection of cyanide with sensitivity levels down to 0.2 ppb and 0.4 ppb, respectively. The plausible sensing mechanism is based on Michael type adduct formation due to the reaction of cyanide with chemosensors and was confirmed by 1H NMR titration, Job’s plot, dynamic light scattering (DLS), and density functional theory (DFT) calculations. Chemosensors 1 and 2 showed excellent linear response towards CN¯ ions (0–100 nM) in the Benesi–Hildebrand plot with association constants (Ka) 1.61 × 106 and 7.1 × 105 M¯1, respectively that corresponds to their favorable chemical reaction. Excellent selectivity of chemosensors for cyanide in the presence of other interferences was investigated through fluorescence emission, UV–Visible, and DFT analysis. Surprisingly, an immediate reversible colorimetric change upon alternate shaking and steadiness of chemosensor − CN¯ solution was noticed indicating that chemosensors can act as promising recyclable sensors for colorimetric on-site detection of CN¯. Meanwhile, chemosensors 1 and 2 displayed highly selective colorimetric detection of CN¯ under daylight and UV radiations (365 nm). Further, cyanide responsive test kits were fabricated that provided a low-cost and portable method for on-site detection of CN¯ ions in an aqueous medium. Finally, chemosensors were successfully applied for designing logic gates, and detection of cyanide in industrial waste and food samples.

A Cd(II) Luminescent Coordination Grid as a Multiresponsive Fluorescence Sensor for Cr(VI) Oxyanions and Cr(III), Fe(III), and Al(III) in Aqueous Medium.

Hydro(solvo)thermal reactions of Cd(NO3)2, N-(pyridin-3-ylmethyl)-4-(pyridin-4-yl)-1,8-naphthalimide (NI-mbpy-34), and 5-bromobenzene-1,3-dicarboxylic acid (Br-1,3-H2bdc) afforded a luminescent coordination polymer, {[Cd(Br-1,3-bdc)(NI-mbpy-34)(H2O)]∙2H2O}n (1). Single-crystal X-ray diffraction analysis showed that 1 features a two-dimensional (2-D) gridlike sql layer with the point symbol of (44·62), where the Cd(II) center adopts a {CdO5N2} pentagonal bipyramidal geometry. Thermogravimetric (TG) analysis confirmed the thermal stability of 1 up to about 340 °C, whereas XRPD patterns proved the maintenance of crystallinity and framework integrity of 1 in CH2Cl2, H2O, CH3OH, and toluene. Photoluminescence studies indicated that 1 displayed intense blue fluorescence emissions in both solid-state and H2O suspension-phase. Owing to the good fluorescent properties, 1 could serve as an excellent turn-off fluorescence sensor for selective and sensitive Cr(VI) detection in water, with LOD = 15.15 μM for CrO42− and 14.91 μM for Cr2O72−, through energy competition absorption mechanism. In addition, 1 could also sensitively detect Cr3+, Fe3+, and Al3+ ions in aqueous medium via fluorescence-enhancement responses, with LOD = 2.81 μM for Cr3+, 3.82 μM for Fe3+, and 3.37 μM for Al3+, mainly through an absorbance-caused enhancement (ACE) mechanism.

Multiplexed detection of aqueous Cd2+, Pb2+ and Cu2+ ions at mercury-on-graphene film modified electrode by DPASV

With the ever-increasing influence of heavy metal ions in environmental pollution, it is highly desirable to develop facile, rapid, and low-cost methods for the multiplexed detection of heavy metal ions in aqueous media sensitively and quantitatively. In this study, we report a facile electrochemical method for the selective, quantitative and multiplexed detection of cadmium (Cd2+), lead (Pb2+), and copper (Cu2+) ions in aqueous media. In this method, a glassy carbon electrode (GCE) is modified first with reduced graphene oxide(rGO) microflaks followed by the controlled in situ electro-deposition of a very thin mercury film. The final working electrode, denoted as (Hg|rGO)film|GCE, was employed as the detector for reported multiplexed detection of multi-ions, taking advantages of the well-established polaragraphic principles. The rGO layer was known to be capable of significantly increasing the heterogeneous interface electron-transfer rate and therefore the detection sensitivity, while the highly dispersed over-potentials of heavy metal ions on mercury allowed the multiplexed detection of several heavy metals ions at different working potentials. The differential pulse anodic stripping voltammetry (DPASV) was employed as the detection mode to further boost up the detection sensitivity. Very good quantitative relationships were observed between the peak current in DPASV and the concentration of the ions being detected. The cross-interference in the multiplexed detection was found negligible. The limit of detections (LODs) of Cd2+, Pb2+, and Cu2+ ions in aqueous phase at the (Hg/rGO)film/GCE working electrode were found to be 0.17, 0.18 and 0.69 μg/L, respectively.

Platinum(II)‐mediated disulfide/thiolate interconversion in organic disulfides: Density functional theory thermodynamic study

AbstractWe present a complete Density Functional Theory (DFT) study of the thermodynamics of the reactions of disulfides (l‐cystine, cystamine, dl‐homocystine, and 3,3′‐dithiodipropionic acid) with Pt(II) ions in aqueous media. SMD solvation model was fitted to take into account the solvation effects of the medium. DFT calculations predict the oxidative addition reaction with the formation of thiolate complexes of Pt(IV)—[PtCl4(S‐R)2] which is consistent with experimental data. We propose a theoretical model that rationalizes the experimental data on Pt(II) interactions with homological disulfides. The role of explicit solvation in reactions is also investigated. We propose that the stability of S,S′‐binuclear disulfide complexes correlates with the redistribution of charges on sulfur atoms. We compared MN15 and PBE0 functionals for the calculation of equilibrium constants.

A bifunctional 3D porous Zn-MOF: Fluorescence recognition of Fe3+ and adsorption of congo red/methyl orange dyes in aqueous medium

Fe3+ Herein, a bifunctional 3D porous metal-organic framework (Zn-MOF) was synthesized based on the solvothermal reaction of tri(p-carboxyphenyl)phosphane oxide (H3L) and Zn salts, and characterized by powder X-ray diffraction (PXRD), thermogravimetric (TG), Infrared (IR), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET). The results show that Zn-MOF has high stability and its specific surface area and pore size are 102.36 m2 g−1 and 2.94 nm, respectively. Meanwhile, Zn-MOF exhibited excellent adsorption performance for Congo red (CR) and Methyl orange (MO) dyes. The adsorption of CR dyes by Zn-MOF is mainly due to the sedimentation caused by gravity of large molecules formed by hydrogen bonding between –NH2 in CR dye molecules and μ3-OH- in Zn-MOF, while the adsorption of MO by Zn-MOF is mainly attributed to that the larger pore size of Zn-MOF is conducive to MO dye molecules into the channels of Zn-MOF. At the same time, a series of fluorescence experiments showed that Zn-MOF can also sensitively recognize Fe3+ ion in aqueous medium with the limit of detection of 0.09716 μM, which is inferior to the previously reported values. Furthermore, the recognition mechanism of Zn-MOF for Fe3+ ion is mainly ascribed to the internal filtering effect (IFE) by the characterization of PXRD, UV–vis and fluorescence lifetime.

Synthesis of SBA-Pr-NHC as a selective fluorescent sensor for the detection of Ag+ ion in aqueous media

SBA-Pr-NHC as a novel silica-based chemosensor was synthesized through the functionalization of mesoporous silica SBA-15 material with 4-hydroxy-2-oxo-2H-chromene-3-carbaldehyde, which was successfully immobilized to the surface of mesoporous silica, and its hexagonal mesoporous structure has been preserved. Photoluminescence spectroscopy was applied to study the sensing behavior of SBA-Pr-NHC, which displayed high selectivity for sensing Ag+ ion in aqueous media. After the addition of trace amounts of Ag+ ions into the aqueous solution, a significant enhancement of fluorescence emission has occurred with the detection limits of 2.4 × 10−5 M.

Luminescence quenching of Ru(II)-diimine complexes with Cr(VI) ions: Steady-state and time-resolved studies

Luminescence quenching of [Ru(bpy)(CN)4]2−, [Ru(phen)(CN)4]2−, [Ru(bpy)3]2+ and [Ru(phen)3]2+ by hexavalent chromium ion in aqueous media were investigated by steady-state and time-resolved measurements. Effect of pH on the luminescence quenching process is also investigated. It has been found that luminescence changes due to the interaction of all Ru(II) complexes with Cr(VI) ions were high at pH values less than or equal to 5.0 and negligible at pH ≥ 8.0. The experimental data of the quenching process were analyzed using Stern–Volmer (S–V) equations. The steady state luminescence emission data shows an upward curvature, indicating that the quenching is preceded by both dynamic and static quenching. For all studied complexes, the lifetime of the excited 3MLCT state decreases with increasing Cr(VI) concentration implying that the diffusion is mainly responsible for the quenching process. The Stern–Volmer dynamic quenching constants (KD) and the bimolecular quenching rate constant for the quenching process (kq) were calculated by applying the Stern–Volmer equation to the luminescence decay data. The bimolecular quenching rate constants (Kq) were found to increase in the order [Ru(bpy)(CN)4]2− < [Ru(phen)(CN)4]2− < [Ru(phen)3]2+ < [Ru(bpy)3]2+ which correlates will with the oxidation potentials of Ru(II) complexes. The association constants for Ru(II)-Cr(VI) system were calculated using the Benesi-Hildebrand equation and found to be 3.0 × 103, 2.5 × 103, 1.2 × 103, 7.1 × 103 M−1 for [Ru(bpy)(CN)4]2−, [Ru(phen)(CN)4]2−, [Ru(bpy)3]2+ and [Ru(phen)3]2+ respectively, which is interpreted in terms of the dynamic (diffusion) and the sphere of action (static) quenching models.

Building carbazole-decorated styrene–acrylic copolymer latexes and films for iron(III) ion detection

The detection and sensing of trace iron(III) ions is a crucial but challenging task. Herein, we report a facile strategy to build carbazole-based copolymer latexes and films via semi-continuous emulsion copolymerization for the selective detection of iron(III) ions. Carbazole-decorated styrene–acrylic copolymer latexes were synthesized by the copolymerization of styrene, acrylates, and N-vinylcarbazole (NVCz) under mild conditions. The effects of the comonomer composition on emulsion copolymerization and the properties of the copolymer latexes/films were studied. The obtained copolymer latexes exhibit homogeneous spheres through regulating the NVCz content from 0 to 5 wt%. Notably, the copolymers exhibited the characteristic emission of carbazole in both latex and solution form, and the emission intensity can be easily tuned by varying the NVCz content. Surprisingly, higher carbazole content led to differences in the excitation and emission peaks of the latex and solution, resulting from the formation of an excimer in the latex. Moreover, the fluorescence of the latex and film can be selectively and effectively quenched by trace amounts of iron(III) ions in aqueous media. The limits of detection (LODs) of the copolymer latex and film were 1.90 and 1.71 μM, respectively. These results illustrate that the carbazole-decorated styrene–acrylic copolymer prepared employing a facile, inexpensive, scalable and environment-friendly procedure can be used to fabricate high-performance photoelectric devices and high-efficiency fluorescent sensors. Carbazole-decorated styrene–acrylic copolymer latexes were prepared by simple and environment-friendly emulsion polymerization. The obtained copolymer exhibit characteristic emission of carbazole in both latex and solution, and their emission intensity can be well tuned by varying NVCz content and selectively quenched by trace amounts of Fe 3+ . • Preparation of carbazole-decorated styrene-acrylic copolymer via emulsion polymerization. • Regulation of the emission intensity through varying N-vinylcarbazole content. • Application of the prepared copolymer latexes/films for fluorescence sensing. • Selective Fe 3+ ions detection via fluorescence quenching.

Design and synthesis of a novel chemosensor for simultaneous detection of CN−, HCO3− and AcO− anions and Fe2+ cation in an organic-aqueous environment: An experimental and Density Functional Theory studies

• A novel Schiff base ligand, namely 2-((E)-(2-(1H-indol-3-yl)ethylimino)methyl)-4-((E)-(2-nitrophenyl)diazenyl)phenol (L) was synthesized. • The receptor (L) (5 × 10 −5 M) in DMF solution exhibited very good sensing behavior towards CNˉ, HCO 3 −, AcO− and Fe2+ ions. • The stabilization energy of the optimized complexes was more negative than the energy of free receptor (L) proving the greater stability of the formed complexes. • The reversibility of the synthesized receptor (L) was successfully approved. • The receptor (L) can be candidate as an operational colorimetric chemosensor with low-cost detection, high selectivity and nice reversibility in DMF solutions. A new azo–azomethine chemosensor, 2-((E)-(2-(1H-indol-3-yl)ethylimino)methyl)-4-((E)-(2-nitrophenyl)diazenyl)phenol, L, was synthesized and characterized by Infrared spectroscopy (IR), Ultraviolet–visible spectroscopy (UV-Visible) and Nuclear magnetic resonance spectroscopy (NMR) methods. The sensory properties of this Schiff base compound (L) were investigated in Dimethyl sulfoxide (DMSO)/H 2 O (9.5:0.5 v/v) solution. It was selectively sensitive to CN ˉ and HCO 3 ˉ and AcO ˉ anions, and in the presence of them, the color of solution L through deprotonating mechanism changed from yellow to orange. This chemosensor also sensitive to Fe 2+ . Then, by using Job's method and Benesi–Hildebrand equation, the binding stoichiometry of L with anions and binding constant (k a ) were determined (CN − : 1:1, 3.47×10 +5 ; HCO 3 − : 1:1, 2.44×10 +5 ; AcO − : 1:1, 1.76×10 +5 ), respectively. Also, the Limit of Detection (LOD) was calculated. Finally, the observed experimental results were confirmed by Density Functional Theory (DFT) calculations. A new Schiff base chemosensor, 2-((E)-(2-(1H-indol-3-yl)ethylimino)methyl)-4-((E)-(2-nitrophenyl)diazenyl)phenol, L, was synthesized. The L sensor successfully detected both cations (Fe 2+ ) and anions (AcO ˉ , CN ˉ , HCO 3 ˉ ) by the naked-eye and UV–Vis spectroscopy in an organic-aqueous environment. Through DFT calculations, the experimental results were confirmed. So, we believe that L can be an efficient sensor for detecting said ions in aqueous media.

The complexation of levofloxacin hemihydrate with divalent metal ions in aqueous medium at variable temperatures: Combined UV–Visible spectroscopic and DFT studies

Herein, we have studied the binding of levofloxacin hemihydrate (LFH) drug with different metal ions e.g., alkali earth metal ions and transition metal ions through spectrophotometry and Density Function Theory (DFT) studies. The binding constant (Kf) of LFH with alkali earth metal ions was observed to be increased with the boost of temperature while the opposite trend was observed in the case of transition metal ions. The Kf values were experienced to be reduced with the increase of size of the alkali earth metal ions. The Kf values in case of transition metal follow the order Cu2+ > Ni2+ > Co2+ > Zn2+. The Gibbs free energy (ΔG0) of binding values reveal that binding phenomena are spontaneous in nature. The values of enthalpy (ΔH0) and entropy (ΔS0) of binding suggest that hydrophobic interactions are the key forces for the binding of LFH and alkali earth metal ions while electrostatic, dipole-dipole, ion-dipole, and hydrogen bonding are the key forces in case of transition metal ions. The enthalpy-entropy compensation parameters were also estimated and explained in detail. From the DFT study, the bond lengths, bond angles, HOMO and LUMO orbitals energy, band gap, hardness, and the highest wavelengths of the drug/ drug-metal complexes have been calculated and explained with appropriate reasoning.

A new and efficient diaminopyrimidine-based colorimetric and fluorescence chemosensor for the highly selective and sensitive detection of Cu2+ in aqueous media and living cells

In this paper, a new and effective diaminopyrimidine-based chemosensor (DAPCS) was developed for the highly selective and ultra-sensitive detection of Cu2+ ion in aqueous media and living cell. Characterization and structure determining of DAPCS was determined by UV–Vis, FTIR and NMR analyses. It is observed that DAPCS and Cu (II) forms a ligand to metal charge transfer (LMCT) complex which produces distinguishable red color. The results also indicate that the DAPCS easily interacts with Cu2+ ion to form a 1:1 stoichiometry complex (DAPCS -Cu2+), resulting in a bathochromic shift in absorption maximum (429 nm to 449 nm) and remarkable quenching fluorescence intensity at the wavelength of 501 nm in DMSO-H2O solution. Furthermore, the detection limit of DAPCS towards Cu2+ was calculated to be 3.19 µM. Meanwhile, DAPCS was applied as fluorescent probe for detection of Cu2+ ions with the detection limit of 0.014 µM. The optimal pH range of probe DAPCS for quantitative analysis of Cu2+ ions was 9–11, which renders it suitable for detection of Cu2+ under physiological conditions. Additionally, the DAPCS could be applied to detect Cu2+ in real water samples and in HeLa cells, indicating the practical uses of DAPCS in real analyses.