Evaluation of cerium doped tin oxide nanoparticles as a sensitive sensor for selective detection and extraction of cobalt

Chemo-sensor technology demands to design a single, preconcentrator based sensing system having higher sensitivity, sufficient selectivity and efficient removal of metal ions with simple operating and recognition methodology. Here we effectively deliberated Ce doped SnO₂ nanoparticles based sensing system which can be exploited for the recognition and extraction of Co(II) ions in a single step by strong interaction between Ce doped SnO₂ nanoparticles and Co(II). The sensing ability of Ce doped SnO₂ nanoparticles were deliberated for a selective removal of cobalt using inductively coupled plasma-optical emission spectrometry. The sensing ability of Ce doped SnO₂ is studied for various metal ions, such as Cd(II), Co(II), Cr(III), Cu(II), Fe(III), Ni(II) and Zn(II) but the designed sensor was most selective toward Co(II) which was 5000 time more sensitive to Co(II) rather than different interfering metal ions. In addition, the desorption study for regeneration of Ce doped SnO₂ nanoparticles was carried out. This novel approach provides a new route for simultaneous detection and removal of Co(II) in a single step and can be a time and cost alternative tool for environmental safety.     

Poly(thymine)-templated copper nanoparticles as a fluorescence probe for highly selective and rapid detection of cysteine

A highly selective and rapid analytical method was proposed to detect cysteine in aqueous solution by using poly(thymine)-templated copper nanoparticles. In a neutral aqueous condition, the fluorescence of poly(thymine)-templated copper nanoparticles could be quenched by cysteine in 10?min effectively coexisting with common biological small molecules. Under the optimal experimental condition, the present assay allowed for the selective determination of cysteine in the range of 12.5–100?µM, with a detection limit of 7.3?µM. The results indicated that the poly(thymine)-templated copper nanoparticles probe would find potential application in bioanalysis.     

Label-free tungsten disulfide quantum dots as a fluorescent sensing platform for highly efficient detection of copper(Ⅱ) ions

A fluorescent probe for the sensitive and selective determination of copper ion(Cu~(2+)) is presented. It is based on the use of tungsten disulfide quantum dots(WS_2 QDs) which is independent of the p H of solution and emits strong blue fluorescence. Copper ions could cause aggregation of the WS_2 QDs and lead to fluorescence quenching of WS_2 QDs. The change of fluorescence intensity is proportional to the concentration of Cu~(2+), and the limit of detection is 0.4 μM. The fluorescent probe is highly selective for Cu~(2+) over some potentially interfering ions. These results indicate that WS_2 QDs,as a fluorescent sensing platform, can meet the selective requirements for biomedical and environmental application.     

Ultrasound-electrospinning-assisted fabrication and sensing evaluation of a novel membrane as ultrasensitive sensor for copper (II) ions detection in aqueous environment

The present study has reported an optimized fabrication and application of a novel PVA/TEOS/Schiff base nanofibers membrane as a highly sensitive copper (II) ions in aqueous environment. Here in, for first time, an ultrasound-assisted synthesized symmetric Schiff base has been immobilized on a hybrid polyvinyl alcohol (PVA) and TEOS using electrospinning technique for detection and filtration of copper ions. For this purpose, various working parameters were evaluated and finally the optimized nano fibers membrane was synthesized with 72 nm thickness and PVA/TEOS/Schiff base ratio of (wt%) 8:6:1. The optimized sample named PTLNFM has been employed successfully as an ultra sensitive chemosensor for Cu (II) detection in real samples. The immobilized Schiff base used as a chelating agent could detect copper (II) in the range from 9.34 × 10⁻⁸ to 1.15 × 10⁻⁵ mol L⁻¹ with the following correlation equation: Absorbance = 0.066 [Cu²⁺] × 10⁻⁶ + 0.095 and R² = 0.992 and LOD of 1.27 × 10⁻⁸ mol L⁻¹ which was lower than most of the reported detection limits in the previous literatures. Validity of this method has been carried out by analysis of Cu²⁺ in real samples with satisfying recoveries of over 96.11–99.24%.The developed membrane could be offered for diverse use such as medical or industrial applications.     

Mercaptopropionic acid capped CdSe/ZnS quantum dots as fluorescence probe for lead(II)

MPA stabilized CdSe/ZnS NCs was applied as a fluorescent probe for the sensitive detection of Pb²⁺ in water. The microreaction was demonstrated as a facile method for the reproducible synthesis of CdSe/ZnS NCs with a high quantum yield. The good stability of CdSe/ZnS NCs was proved by the significant maintaining of photoluminescent (PL) after the ligand exchange with MPA, and was further demonstrated by the excellent PL property in water solution with various pH values. The cation exchange of Zn with Pb led to the linear quenching of PL with the concentration of Pb²⁺, which provided as an opportunity to apply MPA stabilized CdSe/ZnS NCs as fluorescent probes for Pb²⁺. A facile method by adjustment of QDs concentration was demonstrated as a suitable way to approach different detection limits. The detection limits of 0.03 and 3.3 μM were achieved by setting QDs solutions with the absorbance of the first exciton peak as 0.05 and 0.15, respectively.     

Ultrasonic-assisted synthesis of the nanostructures of a Co(II) metal organic framework as a highly sensitive fluorescence probe of phenol derivatives

Nanostructures of a metal-organic framework with chemical formula, [Co(BDC)(L*)]_n.DMF (TMU-40), BDC = 1,4-benzendicarboxylate, L* = 5,6-dipyridin-4-yl-1,2,3,4-tetrahydropyrazine, under ultrasonic irradiation at ambient temperature and atmospheric pressure were prepared and characterized by Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Sonication time, concentration of initial reagents and ultrasonic generator power effects on the size and morphology of nano-structured compounds were studied. TMU-40 (for Tarbiat Modares University) displayed a good potential as a luminescent sensor against phenol derivatives consist of phenol, 4-aminophenol, 4-methylphenol and 4-chlorophenol. Nano-sized TMU-40 showed the better sensing performance in comparison to its bulk phase. The nano TMU-40 displayed very selective and sensitive in detection of phenol derivatives. The detection limit amounts of 15 nM and 63 nM were achieved for 4-aminophenol in nano TMU-40 and bulk TMU-40, respectively. The special structure and fluorescent character of L* ligand and high surface area of nano MOF provide an effective interaction between MOF and phenolic analytes to selectively and sensitively detect of the analyte molecules.     

Wavelength selective detection using excitonic resonances in GaAs/AlGaAs P-I-(MQW)-N structures

The quantum confined Stark effect causes a strong wavelength and voltage dependence of photocurrent near excitonic resonances which is used to study the wavelength selectivity of p-i(MQW)-n photodiode. For a parallel input of optical bits each coming at a different wavelength, the selectivity is considered good if the state of a λ_i wavelength bit can be detected regardless of the λ_j (j ≠ i) state of the bits. Photocurrent is found to have very good selectivity if λ_j bits are all zero, i.e. the optical information is serial. However, we find that differential photocurrent (Δ I_ph/ΔV) provides a good selectivity for random states of λ_j bits (i.e. parallel input). Four channel selectivity is demonstrated at 200K. Specially designed quantum well structures can greatly improve this selectivity.     

Mono(pyridine-N-oxide) analog of DOTA as a suitable organic reagent for a sensitive and selective fluorimetric determination of Ln(III) ions

The mono(pyridine-N-oxide) analog of the H₄dota macrocylic ligand, H₃do3a-py^NO, is capable of forming thermodynamically stable and kinetically inert Ln(III) complexes. Its Eu(III) and Tb(III) complexes display a strong long-lived fluorescence as a result of the antenna effect of the pyridine-N-oxide fluorophore in the reagent. It is shown that H₃do3a-py^NO can be used as a fluorogenic reagent for the determination of Eu(III) and Tb(III) at pH 6.5 and c_L=1 mM. At an excitation wavelength of 286 nm, the emission maxima are 615 nm (Eu(III)-complex), and 547 nm (Tb(III)complex). Detection limits are at concentrations around 1.0 μM and linearity of the method spans over 2 orders of magnitude. The method was applied to artificial and real samples (spiked mineral waters, extracts from cathode ray tube luminophore dust) and gave satisfactory results. The method is simple, rapid, and hardly interfered by other metal ions.     

An electrochemical sensor based on carbon nanotubes and a new Schiff base for selective determination of dopamine in the presence of uric acid, folic acid, and acetaminophen

In this paper, the electrochemical properties of a carbon paste electrode modified by a synthesized Schiff base, 2,2′-[1,4-phenylenediyl-bis(nitrilomethyl-idene)]-bis(4-hydroxyphenol), and carbon nanotubes were studied by cyclic voltammetry. The modified electrode was used as an electrochemical sensor for catalytic oxidation of dopamine (DA). Differential pulse voltammetry (DPV) of DA by this electrochemical sensor exhibited two linear dynamic ranges with a detection limit (3σ) of 0.42 μM. Also, the selectivity of the prepared electrochemical sensor was checked for determination of DA in the presence of uric acid (UA), folic acid (FA), and acetaminophen (AC). The DPV results indicate that the proposed sensor can be used for simultaneous determination of DA, UA, and FA and also simultaneous determination of DA and AC. Finally, the proposed electrochemical sensor was used for determinations of these substances in real sample.     

Nanocomposite of p-type conductive polymer/Cu (II)-based metal-organic frameworks as a novel and hybrid electrode material for highly capacitive pseudocapacitors

In this paper firstly, Cu (II)-based metal-organic framework (MOF; Cu-bipy-BTC, bipy = 2,2′-bipyridine, BTC = 1,3,5-tricarboxylate) was synthesized using chemical approach and then fabricated hybrid poly ortho aminophenol (POAP)/Cu-bipy-BTC films by electropolymerization of POAP in the presence of Cu-bipy-BTC nanoparticles to serve as the active electrode for electrochemical storage device. Surface analysis and electrochemical analysis have been used for characterization of POAP/Cu-bipy-BTC composite film. Different electrochemical methods including galvanostatic charge–discharge experiments, cyclic voltammetry, and electrochemical impedance spectroscopy are carried out in order to investigate the performance of the system. This work introduces new nanocomposite materials for electrochemical redox capacitors with advantages including ease synthesis, high active surface area, and stability in an aqueous electrolyte.     

Molecular engineered silica surfaces with an assembled anthracene monolayer as a fluorescent sensor for organic copper(II) salts

A novel fluorescence film has been fabricated by covalently coupling anthracene on a glass plate surface via a long flexible “Y” type spacer. Fluorescence measurement demonstrated that the emission of the film is dominated by anthracene monomer emission, and the emission can be selectively quenched by organic copper(II) salts including copper acetate, copper citrate, copper tartrate, etc. Addition of inorganic copper(II) salts like Cu(NO₃)₂, CuSO₄, CuCl₂, etc., however, has little effect upon the emission of the film. This observation was explained by considering the screening effect of the spacer layer, or spacer clusters, or even spacers adopting compact coiled conformation. Different from the reported fluorescence films with similar structures, immobilization of anthracene via a “Y” type spacer on a glass plate surface makes the fluorophore moieties exist in two different states, that is some of them were embedded within the spacer structures, and some of them might stay out of the structures. This hypothesis has been confirmed by model system, solvent effect and quenching mechanism studies. The emission of the film is sensitive to the presence of organic copper(II) salts like copper acetate. The response of the film to copper acetate is fully reversible. Presence of other inorganic salts, including Pb(Ac)₂, Cd(Ac)₂, Zn(Ac)₂, and inorganic copper(II) salts has little effect upon the sensing performance of the film to copper acetate.     

A Co-Crystallised Cobalt(II) Cluster of Pyridinedicarboxylic Acid (PDC) as a Luminescent Material for Selective Sensing of Methanol

A luminescent Cobalt(II) co-crystal [Co₁₃(PDC)₁₆(H₂O)₂₄.7H₂O] 1 (where H₂PDC?=?2,6-pyridinedicarboxylic acid) have been prepared by oven-heating and slow evaporation of solvent. Single crystal X-ray diffraction (SCXRD) analysis revealed that 1 is a mixture of complexes that crystallizes in the triclinic space group P-1 and the geometry around the Co(II) ions is octahedral. The structure is extensively imbued with hydrogen bonding that helps in stabilizing the complex. Thermogravimetric analysis indicates that 1 is thermally stable up to 364 ^οC. The luminescence properties of 1 revealed a strong emission centered at 437 nm (λex?=?345 nm) assigned to ligand to metal charge transfer (LMCT). The luminescence sensing of 1 towards volatile organic molecules were also examined. However, 1 displayed a turn off towards methanol compared to other molecules with high quenching efficiency and low limit of detection (3.5?×?10^?4 vol%). The results show excellent selectively and high sensitivity. Powder X-ray diffraction studies revealed that the structural integrity of the complex was maintained after exposure to methanol vapour. Theoretical studies also revealed small binding energy (?413.2 au) and low energy gap (1.19) for 1-CH₃OH adduct.

     

Sonochemical synthesis and structural characterization of a new nanostructured Co(II) supramolecular coordination polymer with Lewis base sites as a new catalyst for Knoevenagel condensation

A new Co(II) mixed-ligand coordination supramolecular polymer with composition [Co₂(ppda)(4-bpdh)₂(NO₃)₂]_n (1) (where, ppda = p-phenylenediacrylic acid, 4-bpdh = 2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene) was synthesized using solvothermal, mechanochemical and sonochemical methods. Compound 1 and the new nanostructure have been characterized by single-crystal X-ray, infrared spectroscopy (IR), powder X-ray diffraction (PXRD) analysis and scanning electron microscopy (SEM). The thermal stability of compound 1 was also studied by thermal gravimetric analysis (TGA). The surface area of these compounds was determined by BET. The single-crystal X-ray data shows a new interesting two-dimensional coordination polymer (CP). In addition, the effect of various sonication concentrations of initial reagents, power of ultrasound irradiation and also the time on the size and morphology of nano-structured coordination polymer 1 were evaluated. Moreover, it has been demonstrated that the nanostructure of the CP1 can be used as a catalyst in Knoevenagel condensation reaction.     

Evaluation of carbon-supported copper phthalocyanine (CuPc/C) as a cathode catalyst for fuel cells using Nafion as an electrolyte

Carbon-supported copper phthalocyanine (CuPc/C) nanoclusters, as a novel suitable cathode catalyst in polymer electrolyte membrane fuel cells, have been synthesized via a combined solvent impregnation and milling procedure along with high-temperature treatment. For optimizing the electrocatalytic activity of the catalyst obtained, the electrode with varying Nafion ionomer contents in the catalyst layer was screened by cyclic voltammetry and linear sweep voltammetry employing a rotating disk electrode technique to investigate the effect of Nafion ionomer as for alkaline electrolyte. For comparative purposes, electrode with various contents of available anion-ionomer was also investigated. The results revealed that the content of Nafion ionomer can affect the oxygen reduction reaction activity of the CuPc/C catalyst and an optimal content of Nafion ionomer was around 3.5?×?10¹?μg?cm^?2, which corresponds well with the electrode prepared using available anion-ionomer. The electrode prepared using Nafion ionomer can produce a comparable performance to that of using available anion-ionomer, giving an onset potential at 0.1 V with a half-wave potential of ?0.03 V. Furthermore, Koutechy–Levich analysis showed that the value of electron transfer number is in the range of 3.40 to 3.74 when using electrode with varying Nafion ionomer contents from 2.5?×?10¹ to 1.6?×?10²?μg?cm^?2. The membrane electrode assembly fabricated with the CuPc/C cathode catalyst with a loading of 3.6 mg?cm^?2 and a Nafion membrane immersed in 3 M KOH for 48 h produced a power density of 3.8 mW?cm^?2 at room temperature.     

A time-domain approach for damage detection in beam structures using vibration data with a moving oscillator as an excitation source

The problem of detecting local/distributed change of stiffness in bridge structures using ambient vibration data is considered. The vibration induced by a vehicle moving on the bridge is taken to be the excitation source. A validated finite element model for the bridge structure in its undamaged state is assumed to be available. Alterations to be made to this initial model, to reflect the changes in bridge behaviour due to occurrence of damage, are determined using a time-domain approach. The study takes into account complicating features arising out of dynamic interactions between vehicle and the bridge, bridge deck unevenness, spatial incompleteness of measured data and presence of measurement noise. The inclusion of vehicle inertia, stiffness and damping characteristics into the analysis makes the system time variant, which, in turn, necessitates treatment of the damage detection problem in time domain. The efficacy of the procedures developed is demonstrated by considering detection of localized/distributed damages in a beam-moving oscillator model using synthetically generated vibration data.     

A dive counting density estimation method for Blainville’s beaked whale (Mesoplodon densirostris) using a bottom-mounted hydrophone field as applied to a Mid-Frequency Active (MFA) sonar operation

We present a passive acoustic method for estimating the density of echolocating cetaceans that dive synchronously, based on isolation of dive starts using a field of distributed bottom-mounted hydrophones. The method assumes that all dive starts of the target species within a defined area are detected, and that independent estimates of dive rate and group size are available. We apply the method to estimate the density of Blainville’s beaked whales (Mesoplodon densirostris) at the Atlantic Undersea Test and Evaluation Center (AUTEC) in the Bahamas during the time of a multi-ship active sonar exercise. Estimated densities for the 65 h before the exercise, 68 h during, 65 h after, and the final 43 h monitored were 16.99 (95% CI 13.47-21.43), 4.76 (3.78-6.00), 8.67 (6.87-10.94), and 24.75 (19.62-31.23) respectively, illustrating a possible avoidance reaction. Results for the 65 h before were compared with those from the click count density estimation algorithm developed by Marques et al. [Marques T, Thomas L, Ward J, DiMarzio N, Tyack P. Estimating cetacean population density using fixed passive acoustic sensors. An example with Blainville’s beaked whales. J Acoust Soc Am 2009;125(4):1982-1994]. The click count-based estimate was 19.23 animals/1000 km² (95% CI 12.69-29.13)—similar (13% higher), but with higher variance (CV 21% for click count method versus 12% for the dive count method). We discuss potential reasons for the differences, and compare the utility of the two methods. For both, obtaining reliable estimates of the factors that scale the measured quantity (dive starts or detected clicks) to density is the key hurdle. Defining the area monitored in the dive count method can also be problematic, particularly if the array is small.     

Solvothermal synthesis of Cd(OH)2 and CdO nanocrystals and application as a new electrochemical sensor for simultaneous determination of norfloxacin and lomefloxacin

Cadmium hydroxide (Cd(OH)₂) microcrystals were synthesized in ethanol–water medium by using cadmium chloride as cadmium source and 1,10-phenanthroline as complexation agent under solvothermal condition. The sample was characterized by FT-IR, X-ray diffraction (XRD), scanning electron microscopy (SEM) and TEM. The as-prepared Cd(OH)₂ product were transformed to hexagonal CdO nanocubes by thermal treatment in air at 500 °C. The possible growth mechanism for the formation of different morphologies at basic medium has been proposed. DPV experiments were carried out for the simultaneous determination of norfloxacin and lomefloxacin in the acetate buffer solution with pH 4.5.