Detection In Aqueous Media Research Articles

Novel Schiff base (DBDDP) selective detection of Fe (III): Dispersed in aqueous solution and encapsulated in silica cross-linked micellar nanoparticles in living cell

This work demonstrated the synthesis of (4E)-4-(4-(diphenylamino)benzylideneamino)-1,2-dihydro-1,5- dimethyl-2-phenylpyrazol-3-one (DBDDP) for Fe (III) detection in aqueous media and in the core of silica cross-linked micellar nanoparticles in living cells. The free DBDDP performed fluorescence enhancement due to Fe (III)-promoted hydrolysis in a mixed aqueous solution, while the DBDDP-doped silica cross-linked micellar nanoparticles (DBDDP-SCMNPs) performed an electron-transfer based fluorescence quenching of Fe (III) in living cells. The quenching fluorescence of DBDDP-SCMNPs and the concentration of Fe (III) exhibited a linear correlation, which was in accordance with the Stern-Volmer equation. Moreover, DBDDP-SCMNPs showed a low limit of detection (LOD) of 0.1 ppm and an excellent selectivity against other metal ions. Due to the good solubility and biocompatibility, DBDDP-SCMNPs could be applied as fluorescence quenching nanosensors in living cells.

Imprinted polymer coated impedimetric nitrate sensor for real- time water quality monitoring

The need to determine the nitrate-nitrogen (N) concentration in water with more advanced, inexpensive and accurate sensing systems is pressing. Existing sensing systems are costly, and due to their limitations, they are difficult to use in a continuous real-time monitoring program. Ion-imprinted polymer (IIPs) is a useful technique, which allows the development of low-cost sensors with selective recognition elements. Current research has confirmed that IIPs can be combined into interdigital sensor platforms, for nitrate-N detection in aqueous media. The sensing method is based on electrochemical impedance spectroscopy (EIS) with IIP coating material, and allowing the precise detection of nitrate-N in the range of 1–10 (mg/L). Unknown samples are measured to validate the sensing method. An earlier reported sensing system is used to determine the unknown sample, which is compared with commercial sensors. Results were validated using the standard UV-spectrometric method.

Azinphos-methyl detection in aqueous medium using cadmium-based three-dimensional MOF

Azinphos-methyl detection in aqueous medium using cadmium-based three-dimensional MOF

A luminescent Eu(III)-based metal-organic framework as a highly effective sensor for cation and anion detections

Abstract An efficient turn-on fluorescent sensor has been developed by a luminescent metal-organic framework Eu(O-cpia)(phen) (1) with 5-(2-carboxy-phenoxy)- 1,3-benzenedicarboxylic acid (O-cpiaH3) and 1,10-phenanthroline (phen). It displayed a high selectivity for Fe3+, PO43− and F− detection in aqueous medium at a long excitation wavelength of 348 nm. Moreover, luminescence sensing of complex 1 for Fe3+, PO43− and F− ions is totally not influenced by the presence of other conventional ions.

A novel turn-on fluorescent probe for cyanide detection in aqueous media based on a BODIPY-hemicyanine conjugate

Abstract A novel BODIPY-hemicyanine based fluorescent probe 1 for cyanide (CN − ) detection was designed and synthesized. Among the tested anions, the probe showed high selectivity towards CN − . Only addition of CN − to probe 1 in aqueous solution (V H2O /V EtOH = 1/1) could result in a remarkable blue shift of the absorption band from 385 nm to 265 nm and induce 20-fold fluorescence enhancement at 515 nm. The sensing mechanism was based on nucleophilic addition between CN − and indolium group, which was confirmed by 1 H NMR and mass spectrum analysis. Plot of fluorescence intensity as a function of CN − concentrations exhibited a good linear relationship in the range of 0–10 μM, with a detection limit to be 1.53 ppb. Moreover, the proposed sensing approach could work in a wide pH range from 5.0–9.0 and reach an equilibrium instantaneously. Finally, probe 1 was successfully applied in detection of CN − in natural water samples and on test paper strips with satisfactory results.

Coumarin Based Receptor for Naked Eye Detection of Inorganic Fluoride Ion in Aqueous Media

In this communication, we wish to report the design, synthesis and real life applications of coumarin based “naked eye” artificial receptor for fluoride ion detection in aqueous media. Amongst easy-to-synthesize 1-(1-(substituted-2-oxo-2H-chromen-3-yl)-ethylidene)-thiosemicarbazide (receptors A-E), receptor B exhibited remarkable colour change from yellow to pink instantly upon addition of fluoride salt (sodium fluoride) 1×10-5 M (0.19 ppm), in aqueous media. Interestingly, receptor B also gave distinct and discernible colour changes perceivable even with naked eye at different fluoride ion (sodium salt) concentrations (viz., <1.5, 1.5–5 and >5 ppm) fluoride in water which allows a semi-quantitative data to be generated for fluoride contaminated drinking water. Preliminary investigation with everyday commodity items like toothpaste and mouthwash clearly show visual colour change, which may be helpful for detecting presence of fluoride in these items. This method is so simple that it has the potential for being developed as a tool for detecting different levels of fluoride in ground water, especially suitable for rural areas, where the literacy rate is low. The working pH range of receptor B was found to be 6.5–7.5. The binding constant of receptor for fluoride ion was found to be 1.38×105 M-1.

A water-soluble near-infrared (NIR) fluorescence activation probe for efficient detection of dissolved carbon dioxide

A near-infrared (NIR) fluorescent “turn-on” probe is presented for dissolved carbon dioxide (dCO2) detection in aqueous medium. This probe is based on perylene bisimide-functionalized hyperbranched polyethylenimine (PBI-HPEI) polymer, which exhibits typical NIR fluorescence due to the excimer emission of π–π stacked PBI fluorophores. Both UV–vis absorption and fluorescent spectroscopy studies reveal that the PBI-HPEI polymer shows significantly dCO2-sensitive NIR emission via a known photoinduced electron transfer (PET) mechanism. Importantly, this sensory system is characterized with facile synthesis, fast response, excellent water-solubility and wide linear detection concentration range. It is thus capable of detecting dCO2 even in real-world carbonated beverages and drinking water samples. Additionally, in view of the modular design principle of the present fluorescent polymer with typical NIR excimer emission of π–π stacked PBI molecules, the proposed strategy is expected to be applicable to the fabrication of novel versatile NIR-emitting sensory materials.

Turn-on fluorescent sensor for Zinc and Cadmium ions based on quinolone and its sequential response to phosphate

Sequential fluorescence sensing of Zn2+/Cd2+ ions and phosphate anion by new quinoline based sensors(L1 and L2) have been presented. Sensors exhibit highly selective fluorescence “turn-on” sensing properties to Zn2+/Cd2+ ions in CH3OH/H2O(1/1, v/v, Tris, 10mol·L−1, pH 7.4) solution with a 1:1 binding stoichiometry. The complexes display high selectivity to H2PO4- and HPO42- anions through fluorescence “turn-off” respond. The results of Zn2+/Cd2+ ions and phosphate anion sequential recognition via fluorescence changes make sensors L1 and L2 have potential utility for Zn2+/ Cd2+ ions and phosphate anion detection in aqueous media.

P-Aminothiophenol-coated CdSe/ZnS quantum dots as a turn-on fluorescent probe for pH detection in aqueous media

Since controlling hydrogen ion concentration (i.e. pH) is fairly important in various fields, developing a facile pH detection method is highly desired. Owing to the superior optical properties, semiconductor quantum dots (QDs) have been developed as a promising alternative for organic fluorophores in fluorescence analysis. In this study, a hydrophilic p-aminothiophenol (pATP) capped CdSe/ZnS QDs (denoted as pATP-QDs) as a selective “turn-on” fluorescence probe for pH in aqueous media is reported. The pATP-QDs probe easily obtained via ligand exchange are characterized by various analytic techniques including ultraviolet-visible, fourier transform infrared, fluorescence, time-resolved fluorescence spectroscopies, and transmission electron microscope etc. pATP-QDs exhibits weak fluorescence since pATP acts as an effective hole trapper. As an organic base, pATP easily binds to proton and the formation of pATP-H+ complex alters the energetic position of HOMO for pATP, which enables pATP-QDs unfavorable for the effective hole transfer. Thus, the QDs photoluminescence (PL) was switched on. PL “off-on” mode, high PL quantum yield of QDs as well as extremely high stability of pATP-H+ complex (logKs =7.47) enables pATP-QDs to exhibit an excellent pH detection performance. Under optimal conditions, the present probe exhibits a good linear relationship between fluorescence response and pH values in pH range 3.2–6.0. Furthermore, the present probe exhibits a high selectivity for proton over other common cations and has been successfully used for pH detection in real water samples.

Solvothermal synthesis of CoS/reduced porous graphene oxide nanocomposite for selective colorimetric detection of Hg(II) ion in aqueous medium

Metal sulphide nanoparticles (NPs) have great potential applications in environmental remediation as they can oxidize peroxidase substrates like 3,3ʹ,5,5ʹ-tetramethylbenzidine (TMB) due to the production of hydroxide radicals (OH) via the Fenton reaction in presence of H2O2. Their good binding affinity toward heavy metal ions through their S-containing sites, causes the blockage of the active sites of the catalyst and inhibits the oxidation process of peroxidase substrate. This property can be used for the sensing of heavy metal ions. Herein, a cobalt sulphide (CoS) decorated porous reduced graphene oxide (p-rGO) nanocomposite is proposed as a novel matrix for heavy metal ions detection in aqueous medium. The nanocomposite was fabricated by adopting a simple and easy solvothermal approach. After determination of the kinetics of the as-synthesized nanocomposite for the oxidation of TMB in presence of H2O2, the matrix was further used for the colorimetric detection of heavy metal (Hg, Pb, Cd) ions in aqueous medium. Depending on the metal ion, a detection limit of 14.23nM for Hg(II) could be reached. Furthermore, the synthesized nanocomposite was successfully utilized for the detection of heavy metal ions present in real samples.

An Ionic 1,4-Bis(styryl)benzene-Based Fluorescent Probe for Mercury(II) Detection in Water via Deprotection of the Thioacetal Group.

Highly sensitive and selective mercury detection in aqueous media is urgently needed because mercury poisoning usually results from exposure to water-soluble forms of mercury by inhalation and/or ingesting. An ionic conjugated oligoelectrolye (M1Q) based on 1,4-bis(styryl)benzene was synthesized as a fluorescent mercury(II) probe. The thioacetal moiety and quaternized ammonium group were incorporated for Hg2+ recognition and water solubility. A neutral Hg2+ probe (M1) was also prepared based on the same molecular backbone, and their sensor characteristics were investigated in a mixture of acetonitrile/water and in water. In the presence of Hg2+, the thioacetal group was converted to aldehyde functionality, and the resulting photoluminescence intensity decreased. In water, M1Q successfully demonstrated highly sensitive detection, showing a binding toward Hg2+ that was ~15 times stronger and a signal on/off ratio twice as high, compared to M1 in acetonitrile/water. The thioacetal deprotection by Hg2+ ions was substantially facilitated in water without an organic cosolvent. The limit of detection was measured to be 7 nM with a detection range of 10–180 nM in 100% aqueous medium.

A highly selective fluorescent chemosensor based on naphthalimide and Schiff base units for Cu2+ detection in aqueous medium

Abstract A new Schiff base, 4-allylamine-N-(N-5-methylsalicylidene)-1,8-naphthalimide (1), has been designed and synthesized by combining a 1,8-naphthalimide moiety as a fluorophore and a Schiff base as a recognition group. Its photophysical properties were investigated by absorption and fluorescence spectroscopy, and this sensor exhibits a high fluorescence quantum yield of 0.75–0.91 inorganic solvents of different polarity. It also shows high selectivity for Cu2+ over other ions with fluorescence quenching in aqueous medium (pH=7.2). The reason for this phenomenon (fluorescence quenching) is attributed to the formation of a 1:1 complex between 1 and Cu2+ according to the Job plot and fluorescence titration. The sensor can be applied to the quantification of Cu2+ in a linear fashion from 0.5 to 5 μM with a detection limit of 0.23 μM. Additionally, the association constant (K a) between Cu2+ and 1 is 1.328×106 M− 1 in aqueous media.

A dual-response fluorescent probe for Zn2+ and Al3+ detection in aqueous media: pH-dependent selectivity and practical application

A Schiff base-type fluorescent probe (1) consist of 2-hydroxynaphthaldehyde and glutamide moieties has been designed and synthesized for detection Zn2+ and Al3+. The probe shows pH dependent dual-selectivity for Zn2+ and Al3+ in Tris-HCl buffer, viz. that can selectively recognized Zn2+ at pH 7.4 and Al3+ at pH 6.0, respectively. From Job's plots and MS data, the stoichiometric ratios of the probe with Zn2+ and Al3+ appeared to be 1:1 and 2:1, respectively. The probe can detect as low as 5.5 × 10−8 M−1 Zn2+ and 1.27 × 10−7 M−1 Al3+, whereas respective association constants are 4.27 × 104 M−1 and 3.50 × 109 M−1. Furthermore, it is also confirmed that the probe has good cell-permeability and could thus be used to selectively sense intracellular Zn2+ and Al3+ by bioimaging in different pH environment. Finally the probe has been used successfully for determination of the analytes in real drug samples.

Bioinspired materials based on glutathione-functionalized SBA-15 for electrochemical Cd(II) detection

In this work, glutathione was grafted on mesoporous silica materials by silanization with (3-mercaptopropyl)trimethoxysilane, subsequent reaction with 2,2′-dipyridyldisulphide and a final treatment with glutathione. The obtained glutathione-functionalized materials have been characterized by powder X-ray diffraction, FT-IR, scanning electron microscopy, transmission electron microscopy, nitrogen gas sorption and X-ray fluorescence. In addition, the hybrid materials were used in the preparation of modified carbon paste electrodes MCPE by mixing quantities of glutathione-containing materials with paraffin oil and graphite for Cd(II) detection in aqueous media by square wave adsorptive stripping voltammetry. Two materials were used for the preparation of MCPE, (A) the first material was obtained by the grafting of glutathione on the pyridyldisulphide pending ligand of the mesoporous material, (B) the second one, was obtained by grafting a cadmium-glutathione complex on the pyridyldisulphide pending ligand of the mesoporous material. For the latter, elimination of cadmium ions was carried out by treatment with HCl 2 M for 2 h and wash with MilliQ water before preparing the MCPE. To achieve the most accurate and sensitive Cd(II) electrochemical measurements, optimization of the operating parameters in pre concentration and detection steps was performed. The responses are pH dependent, being the optimal conditions 120 s of electrolysis time in buffer solution (pH 6.4). The voltammetric responses increase linearly with the pre concentration time and with metal ion concentrations ranging from 1 to 100 ppb. The metal detection limits were 2 and 4 ppb for materials (A) and (B), respectively, after 5 min pre concentration time.

Zn2+-cyclen-based complex enable a selective detection of single-stranded thymine-rich DNA in aqueous buffer

It is a big challenge to develop fluorescent probes for selective detection of DNA with specific sequences in aqueous buffers. We report a new tetraphenylethene-based Zn2+-cyclen complex (TPECyZn), and a chemo-sensing ensemble of the Zn complex with phenol red. TPECyZn showed significant fluorescence enhancement upon binding to thymine-rich DNA in HEPES buffers. But its selectivity was not high enough to eliminate the interference from some random DNA. By constructing the chemo-sensing ensemble of TPECyZn with phenol red, the background fluorescence was eliminated due to the energy transfer from TPECyZn to phenol red. Moreover, this chemo-sensing ensemble revealed high selectivity in detecting thymine-rich single-stranded DNA over other DNA in aqueous buffer. It can detect poly deoxythymidylic acid sequence as short as 2 nt. This detection in aqueous media makes this probe feasible in real application.

Novel magnetite nanoparticle based on BODIPY as fluorescent hybrid material for Ag(I) detection in aqueous medium

This manuscript describes a highly selective and ultra-sensitive detection of Ag(I) in aqueous solution using amine coated magnetite nanoparticles modified boron-dipyrromethene by spectrofluorometer. Fe3O4 nanoparticles were synthesized by co-precipitation of Fe2+and Fe3+in an ammonia solution. Amine modified Fe3O4 was prepared by using (3-aminopropyl)triethoxysilane as silanization agent. The covalent binding of boron-dipyrromethene to amine modified Fe3O4 was confirmed by means of Fourier Transform infrared spectroscopy, transmission electron microscopy, dynamic light scattering, UV–vis and fluorimeter measurements and obtained nanoparticle-boron dipyrromethene structure. The binding abilities of nanoparticle-boron dipyrromethene towards different metal ions have been investigated by some spectroscopic methods as UV–vis, fluorescence spectroscopy, Job plot, etc. and the novel surface displayed high selectivity and sensitivity for Ag(I) among all tested metals.

Biocompatible ZnS:Mn quantum dots for reactive oxygen generation and detection in aqueous media.

We report here the versatility of Mn-doped ZnS quantum dots (ZnS:Mn QDs) synthesized in aqueous medium for generating reactive oxygen species and for detecting cells. Our experiments provide evidence leading to the elimination of Cd-based cores in CdSe/ZnS systems by substitution of Mn-doped ZnS. Advanced electron microscopy, X-ray diffraction, and optical spectroscopy were applied to elucidate the formation, morphology, and dispersion of the products. We study for the first time the ability of ZnS:Mn QDs to act as immobilizing agents for Tyrosinase (Tyr) enzyme. It was found that ZnS:Mn QDs show no deactivation of Tyr enzyme, which efficiently catalyzed the hydrogen peroxide (H2O2) oxidation and its eventual reduction (−0.063 V vs. Ag/AgCl) on the biosensor surface. The biosensor showed a linear response in the range of 12 μmol/L–0.1 mmol/L at low operation potential. Our observations are explained in terms of a catalase-cycled kinetic mechanism based on the binding of H2O2 to the axial position of one of the active copper sites of the oxy-Tyr during the catalase cycle to produce deoxy-Tyr. A singlet oxygen quantum yield of 0.62 in buffer and 0.54 in water was found when ZnS:Mn QDs were employed as a photosensitizer in the presence of a chemical scavenger and a standard dye. These results are consistent with a chemical trapping energy transfer mechanism. Our results also indicate that ZnS:Mn QDs are well tolerated by HeLa Cells reaching cell viabilities as high as 88 % at 300 µg/mL of QDs for 24 h of incubation. The ability of ZnS:Mn QDs as luminescent nanoprobes for bioimaging is also discussed.Graphical

Spectroscopic and theoretical evaluation of solvent-assisted, cyanide selectivity of chromogenic sensors grounded on mesitylene platform and their biological applications

A series of mesitylene based ratiometric chromogenic sensors (1–3) have been synthesized and evaluated for selective cyanide detection in aqueous medium. Low hydration energy and high basicity of CN− in water is shown to be responsible for selective behavior of probes in the aqueous medium. Spectroscopic and theoretical studies endorse frozen proton transfer as the sensing mechanism. The compounds also show considerable antimicrobial activity.

A novel OFET-based biosensor for the selective and sensitive detection of lactate levels.

Biosensors based on organic field effect transistors (OFETs) are one of the more promising device applications in organic electronics. However, OFET-based biosensors are still in their early stages of development compared to other electrochemical biosensors. This study is the first to report on an extended-gate type organic field effect transistor (OFET) for lactate detection in aqueous media. Here, the extended-gate electrode of the OFET was modified with layers of a lactate oxidase and a horseradish peroxidase osmium-redox polymer on a flexible plastic film substrate for an enzymatic redox reaction of lactate. The device exhibited both high selectivity and sensitivity. The limit of detection (LOD) and the limit of quantification (LOQ) were estimated to be 66 nM and 220 nM, respectively, which are the sufficient detection limit for practical sensor applications. The obtained results confirm that extended-gate type OFET devices are applicable to enzyme-based biosensors for detecting lactate levels.

A disposable electrochemical sensor based on bifunctional periodic mesoporous organosilica for the determination of lead in drinking waters

A new bifunctional disulfide- and tetrasulfide-bridged periodic mesoporous organosilica (PMO) with mercaptothiazoline ligand was synthesized and employed to prepare chemically modified carbon paste electrodes for Pb(II) detection in aqueous media by square wave adsorptive stripping voltammetry. To demonstrate the real interest of bifunctionalization, carbon paste electrodes were prepared with disulfide- and tetrasulfide-bridged PMO without mercaptothiazoline ligand. Results showed the importance of bifunctionalization of PMOs to improve the sensitivity for the determination of Pb(II) in water samples. To achieve the most accurate and sensitive Pb(II) measurements, optimization of the operating parameters in preconcentration and detection steps was performed. Finally, the modified carbon paste electrode prepared with bifunctional disulfide-bridged PMO with mercaptothiazoline ligand was applied to determine Pb(II) in different water samples without any pretreatment. Using this electrode, the optimal operating conditions were 120 s of electrolysis time in HCl 0.4 M. In these conditions, the voltammetric signal increased linearly with the preconcentration time from 1 to 10 min. Under optimized conditions, the linear range was 2–100 μg/L (R 2 = 0.9943) with a detection limit of 0.5 μg/L (for 5-min preconcentration time). Good reproducibility was achieved on both single and equally prepared electrodes. The accuracy of the method was validated by analysing Pb(II) in different drinking and natural water samples, with spiked recoveries in the range of 95–105 ± 10 %. The results demonstrated that the prepared electrochemical sensor exhibited selectivity, fast response time and exceptional long-time stability.