Online Monitoring of Bromate in Ozonized Water Without a Previous Separation Process

The use of ozonation for the purification of drinking water can lead to the formation of bromate. The US Environmental Protection Agency and the European Directive for human drinking water has lowered the regulatory level for bromate down to 10 μg l⁻¹, such that methods must be developed for monitoring the formation of bromate, particularly in on-site situations. In the present work we report a fluorometric method for the determination of bromate based on the reaction with carbostyril-124, a compound that shows florescence mainly at pH values above 4 and, when bromated, generates a non-fluorescent product. The reaction can thus be used as an indirect method for determination of the ion. The proposed method, which uses the flow injection (FI) technique, allows online application and kinetic control of the variables affecting the process, together with shorter reaction times, and it provides maximum sensitivity and selectivity. Under optimum conditions, it is possible to determine the analyte within the 4–200 μg l⁻¹ range, with a limit of detection of 0.9 μg l⁻¹ and a relative standard deviation (n = 12, [] = 5 and 30 μg l⁻¹) of 3.2% and 2.6% respectively. The determination rate was ten samples per hour.     

Synthesis of Functionalized ZnSe Nanoparticles and Their Applications in the Determination of Bovine Serum Albumin

Luminescent quantum dots (QDs)-semiconductor nanocrystals were promising alternative to organic dyes for fluorescence-based applications. In this paper, we developed procedures to use mercaptoacetic acid (MAA) to modify ZnSe nanoparticles and made the nanoparticles to be soluble for the quantitative and selective determination of bovine serum albumin (BSA). Maximum fluorescence intensity was produced at pH 7.0, with excitation and emission wavelengths at 242 and 348 nm, respectively. Under optimal conditions, the straight line equation: ^△ F = 0.38 + 0.34 C (μg/ml) was found between the relative fluorescence intensity and the concentration of BSA in the range of 9.6–124.8 μg/ml, and the limit of detection was 2 μg/ml.     

Electrochemical synthesis of multi-armed CuO nanoparticles and their remarkable bactericidal potential against waterborne bacteria

Copper (II) oxide multi-armed nanoparticles composed of 500–1000 nm long radiating nanospicules with 100–200 nm width near the base and 50–100 nm width at the tapered ends and ~25 nm thickness were synthesized by electrochemical deposition in the presence of an oxidant followed by calcination at 150 °C. The nanoparticles were characterized using SEM/EDX for morphology and composition, Raman spectroscopy for compound identification, and broth culture method for antibacterial efficacy. The CuO nanoparticles have shown remarkable bactericidal efficacy against Gram-positive and -negative waterborne disease causing bacteria like Escherichia coli, Salmonella typhi, staphylococcus aureus and Bacillus subtilis. E. coli has been chosen as representative species for waterborne disease causing bacteria. In antibacterial tests 500 μg/mL nano CuO killed 3 × 10⁸ CFU/mL E. coli bacteria within 4 h of exposure. Moreover, 8.3 × 10⁶ CFU/mL E. coli were killed by 100 and 10 μg/mL nano CuO within 15 min and 4 h of exposure, respectively. Antibacterial activity of nano CuO has been found many-fold compared with commercial bulk CuO. The fate of nanoparticles after antibacterial test has also been studied. The synthesized CuO nanoparticles are expected to have potential antibacterial applications in water purification and in paints and coatings used on frequently touched surfaces and fabrics in hospital settings.     

Application of Functionalized ZnSe Nanoparticles to Determinate Heavy Metal Ions

In this paper, ZnSe nanoparticles, which were modified with mercaptoacetic acid (MAA), worked as novel fluorescence sensors for the quantitative determination of copper(II) and nickel(II). Under the optimal conditions, the fluorescence intensities of functionalized ZnSe nanoparticles were quenched by the addtion of copper(II) or nickel(II) ions, there were linear relationships between the relative fluorescence intensity (logF₀/F) and the concentration in the range of 140–2,000 μg/L for copper(II) (R = 0.9973) and 30–1,000 μg/L for nickel(II) (R = 0.9992), the limits of detection were 50 μg/L and 5 μg/L, respectively.     

Effect of the initial temperature on the threshold of laser initiation of pentaerythritol tetranitrate seeded with aluminum nanoparticles

The effect of temperature on the threshold of explosive decomposition of pentaerythritol tetranitrate samples with a density of ρ = 1.73 g/cm³ containing 0.1 wt % 100- to 120-nm aluminum particles under the action of laser pulses (λ = 1.06 μm, τ = 20 ns) is examined. A model capable of describing the experimental results is proposed, according to which the explosive decomposition of the samples is associated with the absorption of laser radiation by structural defects of pentaerythritol tetranitrate and aluminum nanoparticles. It is demonstrated that, at 300 K, explosion initiation is largely determined by the heating of aluminum nanoparticles with the formation of chemical decomposition kernels nearby.     

Conventional and First Derivative Synchronous Fluorometric Determination of Ethamsylate in Pharmaceutical Preparations and Biological Fluids. Application to Stability Studies

Two simple, accurate and highly sensitive spectrofluorometric methods were developed for the determination of ethamsylate (ETM). Method I is based on measuring the native fluorescence of ethamsylate in water at 354 nm after excitation at 302 nm. The calibration plot was rectilinear over the range of 0.05–1 μg/mL for ETM with limits of detection and quantitation of 7.9 and 26 ng/mL, respectively. Method II involved synchronous and first derivative synchronous fluorometric methods for the simultaneous determination of ethamsylate (ETM) and hydroquinone (HQ) which is considered as an impurity and/or acidic degradation product. The synchronous fluorescence of both the drug and its impurity were measured in methanol at Δ λ of 40 nm. The peak amplitudes (¹D) were estimated at 293.85 or 334.17 nm for ETM and at 309.05 nm for HQ. Good linearity was obtained for ETM over the ranges 0.1–1.4 μg/mL and 0.1–1.0 μg/mL at 293.85 and 334.17 nm, respectively. For HQ, the calibration plot was rectilinear over the range of 0.01–0.14 μg/mL at 309.05 nm. Limits of detection were 20, 2.01 ng/mL and limits of quantitation were 60, 6.7 ng/mL for ETM and HQ by method II, respectively. Both methods were successfully applied to commercial ampoules and tablets. The results were in good agreement with those obtained by the reference method. Method I was utilized to study the stability of ETM and its degradation kinetics using peroxide. The apparent first-order rate constant, half-life times and activation energy of the degradation process were calculated. Method I was further extended to the in-vitro and in-vivo determination of ETM in spiked and real plasma samples. The mean% recoveries were 99.57 ± 3.85 and 89.39 ± 5.93 for spiked and real human plasma, respectively.     

An Indirect Competitive Fluorescence Immunoassay for Determination of Dicyclohexyl Phthalate in Water Samples

A sensitive and specific indirect competitive fluorescence immunoassays (FIA) has been developed for the quantitative determination of dicyclohexyl phthalate (DCHP) using an antigen-coated plate format. The polyclonal antibodies raised against dicyclohexyl 4-amino phthalate conjugated to bovine serum albumin (BSA) by the amino diazotization linkage method. Antiserum with a sufficiently high titer was generated in rabbits and fluorescein isothiocyanate (FITC) was used as sensitive labels to construct the fluorescence immunoassay (FIA) for measurement of targeted compounds. Under optimized FIA condition, the quantitative working range was from 0.1 to 200 μg L⁻¹ with a limit of detection of 0.05 μg L⁻¹. Other similar phthalate compounds do not interfere significantly in the analysis using this immunoassay technique, and the cross-reactivity rates were less than 10%. Four kinds of water samples (tap water, lake water, river water and leachate) had been detected in this assay, the recovery was 91.3–107.8%. The proposed fluorescence immunoassay turned out to be a powerful tool for monitoring of dicyclohexyl phthalate in water samples at trace level.     

In-situ bioconjugation in stationary media and in liquid flow by femtosecond laser ablation

In-situ functionalization of gold nanoparticles with fluorophore-tagged oligonucleotides is studied by comparing femtosecond laser ablation in stationary liquid and in biomolecule flow. Femtosecond laser pulses induce significant degradation to sensitive biomolecules when ablating gold in a stationary solution of oligonucleotides. Contrary, in-situ conjugation of nanoparticles in biomolecule flow considerably reduces the degree of degradation studied by gel electrophoresis and UV–Vis spectrometry. Ablating gold with 100 μJ femtosecond laser pulses DNA sequence does not degrade, while the degree of fluorophore tag degradation was 84% in stationary solution compared to 5% for 1 mL/min liquid flow. It is concluded that femtosecond laser-induced degradation of biomolecules is triggered by absorption of nanoparticle conjugates suspended in the colloid and not by ablation of the target. Quenching of nanoparticle size appears from 0.5 μM biomolecule concentration for 0.3 μg/s nanoparticle productivity indicating the successful surface functionalization. Finally, increasing the liquid flow rate from stationary to 450 mL/min enhances nanoparticle productivity from 0.2 μg/s to 1.5 μg/s, as increasing liquid flow allows removal of light absorbing nanoparticles from the ablation zone, avoiding attenuation of subsequent laser photons.     

Resonance Scattering Spectral Detection of Catalase Activity Using Au@Ag Nanoparticle as Probe and Coupling Catalase Catalytic Reaction with Fenton Reaction

The Au_coreAg_shell (Au@Ag) nanoparticles in size of 30 nm were prepared using 10 nm gold nanoparticles as seeds at 90°C, and were purified by high-speed centrifugation to remove the excess trisodium citrate to obtain Au@Ag nanoprobe. In the medium of pH 4.0 acetate buffer solution—7.2 μmol/L H₂O₂–67 μmol/L Fe(II), Au@Ag nanoparticles exhibited a resonance scattering (RS) peak at 538 nm. Upon addition of Catalase (Ct), the system produced hydroxyl radical that oxidized the Au@Ag nanoprobe to form the AuAg nanoparticles with partly bare nanogold. Those AuAg nanoparticles aggregated to large nanoclusters that led to the RS peak wavelength red-shift and its RS peak intensity enhanced. The catalase activity (C) is linear to the enhanced RS intensity (ΔI) in the range of 6 to 2,800 U/L, with regression equation of ΔI = 0.168 C-0.2, the correlation coefficient of 0.9952, and detection limit of 2.8 U/L. This method was applied to the detection of serum samples, and the results were agreement with that of the spectrophotometry. A new catalytic mechanism of catalase was proposed with oxywater principle that was agreement with the results of resonance scattering spectroscopy, absorption spectrophotometry, transmission electron microscopy and laser scattering.     

Silicon nanoparticles generated by femtosecond laser ablation in a liquid environment

Silicon nanoparticles were generated by femtosecond laser [387 nm, 180 fs, 1 kHz, pulse energy = 3.5 μJ (fluence = 0.8 J/cm²)] ablation of silicon in deionized water. Nanoparticles with diameters from ~5 up to ~200 nm were observed to be formed in the colloidal solution. Their size distribution follows log-normal function with statistical median diameter of ≈20 nm. Longer ablation time leads to a narrowing of the nanoparticle size distribution due to the interaction of the ablating laser beam with the produced nanoparticles. Raman spectroscopy measurements confirm that the nanoparticles exhibit phonon quantum confinement effects and indicate that under the present conditions of ablation they are partially amorphous.     

Spectrophotometric determination of copper(II) in pharmaceutical,biological and water samples by 4-(2′-benzothiazolylazo)-salicylic acid

A highly sensitive method is proposed to determine copper(II) ions by forming a stable complex through their interaction with 4-(2′-benzothiazolylazo)-salicylic acid (BTAS) at room temperature and pH of about 5.0. The complex gave a maximum absorption at λ = 485 nm with a molar absorptivity coefficient of 2.35·10⁴ l/(mol·cm). The linear range for the copper determination is 0.63–5.04 mg/l. The method can be applied to determine copper ions in different biological specimens like some drugs and water samples.     

Simultaneous Determination of Labetalol and Furosemide by First-Derivative Synchronous Spectrofluorimetry

A rapid, simple and highly sensitive first derivative synchronous spectrofluorimetric method was developed for the simultaneous analysis of a binary mixture of labetalol HCl (LBT) and furosemide (FUR) without prior separation. The method was based upon measuring the first derivative of synchronous fluorescence spectra of the two drugs at Δλ =130 nm in aqueous ethanol (55% V/V). The different experimental parameters affecting the synchronous fluorescence of the studied drugs were carefully studied and optimized. The first derivative amplitude-concentration plots were rectilinear over the range of 0.10 to 1.00 μg/mL and 0.05–0.50 μg/mL with lower detection limits of 0.0149 and 7×10⁻³ μg/mL and quantification limits of 0.045 and 0.021 μg/mL for LBT and FUR, respectively. The proposed method was successfully applied for the determination of the studied drugs in synthetic mixtures. The results obtained were in good agreement with those obtained by the reference methods.     

Systematic evaluation of biocompatibility of magnetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles with six different mammalian cell lines

This article systematically evaluated the biocompatibility of multiple mammalian cell lines to 11-nm DMSA-coated Fe₃O₄ magnetic nanoparticles (MNPs). Cells including RAW264.7, THP-1, Hepa1-6, HepG2, HL-7702, and HeLa were incubated with six different concentrations (0, 20, 30, 40, 50, and 100 μg/mL) of MNPs for 48 h, and then the cell labeling, iron loading, cell viability, apoptosis, cycle, and oxidative stress were all quantitatively evaluated. The results revealed that all the cells were effectively labeled by the nanoparticles; however, the iron loading of RAW264.7 was significantly higher than that of other cells at any dose. The proliferations of all the cells were not significantly suppressed by MNPs at the studied dose except HepG2 that was exposed to 100 μg/mL MNPs. The investigation of oxidative stress demonstrated that the levels of total superoxide dismutase and xanthine oxidase had no significant changes in all the cells treated by all the doses of MNPs, while the levels of malonyldialdehyde activity of MNP-treated cells significantly increased. The nanoparticles did not produce any significant effect on cell cycles at any of the doses, but resulted in significant apoptosis of THP-1 and HepG2 cells at the highest concentration of 100 μg/mL. At a concentration of 30 μg/mL which was used in human studies with an intravascular nanoparticle imaging agent (Combidex), the nanoparticles efficiently labeled all the cells studied, but did not produce any significant influence on their viability, oxidative stress, and apoptosis and cycle. Therefore, the nanoparticles were concluded with better biocompatibility, which provided some useful information for its clinical applications.     

Silica coating of Co–Pt alloy nanoparticles prepared in the presence of poly(vinylpyrrolidone)

This article describes a method for silica coating of Co–Pt alloy nanoparticles prepared in the presence of poly(vinylpyrrolidone) (PVP) as a stabilizer. The Co–Pt nanoparticles were prepared in an aqueous solution at 25–80 °C from CoCl₂ (3.0 × 10⁻⁴ M), H₂PtCl₆ (3.0 × 10⁻⁴ M), PVP (0–10 g/L), and NaBH₄ (4.8 × 10⁻³–2.4 × 10⁻² M). The silica coating was performed for the Co–Pt nanoparticle colloid containing the PVP ([Co] = [Pt] = 3.0 × 10⁻⁵ M) at 25 °C in (1/4) (v/v) water/ethanol solution with tetraethoxyorthosilicate (TEOS) (7.2 × 10⁻⁵–7.2 × 10⁻³ M) and ammonia (0.1–1.0 M). Silica particles, which had an average size of 43 nm and contained multiple cores of Co–Pt nanoparticles with a size of ca. 8 nm, were produced at 1.4 × 10⁻³ M TEOS and 0.5 M ammonia after the preparation of Co–Pt nanoparticles at 80 °C, 5 g/L PVP, and 2.4 × 10⁻² M NaBH₄. Their core particles were fcc Co–Pt alloy crystallites. Their saturation magnetization was 2.0-emu/g sample, and their coercive field was 12 Oe.     

Study of iron oxide nanoparticles in soil for remediation of arsenic

There is a growing interest in the use of nanoparticles for environmental applications due to their unique physical and chemical properties. One possible application is the removal of contaminants from water. In this study, the use of iron oxide nanoparticles (19.3 nm magnetite and 37.0 nm hematite) were examined to remove arsenate and arsenite through column studies. The columns contained 1.5 or 15 wt% iron oxide nanoparticles and soil. Arsenic experiments were conducted with 1.5 wt% iron oxides at 1.5 and 6 mL/h with initial arsenate and arsenite concentrations of 100 μg/L. Arsenic release occurred after 400 PV, and 100% release was reached. A long-term study was conducted with 15 wt% magnetite nanoparticles in soil at 0.3 mL/h with an initial arsenate concentration of 100 μg/L. A negligible arsenate concentration occurred for 3559.6 pore volumes (PVs) (132.1 d). Eventually, the arsenate concentration reached about 20% after 9884.1 PV (207.9 d). A retardation factor of about 6742 was calculated indicating strong adsorption of arsenic to the magnetite nanoparticles in the column. Also, increased adsorption was observed after flow interruption. Other experiments showed that arsenic and 12 other metals (V, Cr, Co, Mn, Se, Mo, Cd, Pb, Sb, Tl, Th, U) could be simultaneously removed by the iron oxide nanoparticles in soil. Effluent concentrations were less than 10% for six out of the 12 metals. Desorption experiment showed partial irreversible sorption of arsenic to the iron oxide nanoparticle surface. Strong adsorption, large retardation factor, and resistant desorption suggest that magnetite and hematite nanoparticles have the potential to be used to remove arsenic in sandy soil possibly through in situ techniques.     

Detection of biotin–avidin affinity binding by exploiting a self-referenced system composed of upconverting luminescent nanoparticles and gold nanoparticles

We demonstrate an affinity system based on the interaction of two types of nanoparticles. The first consists of upconverting luminescent NaYF₄:Yb,Er nanoparticles (UCNPs) with a size of 40–100 nm, absorbing light in the infrared and showing luminescence at 521, 543 and at 657 nm. The second consists of (red) gold nanoparticles (Au-NPs) with a size of about 50 nm and capable of absorbing the green luminescence of the UCNPs. By labeling the UCNPs with avidin and the AuNPs with biotin we have established a model system for a self referenced affinity system applicable to sensing in biological samples. In the presence of avidin-modified UCNPs, the biotinylated Au-NPs can be detected in the range from 12 to 250 μg mL⁻¹ by ratioing the intensity of the red (analyte-independent) emission to that of the green (analyte-dependent) emission band. The nanoparticles were characterized in terms of size and composition using transmission electron microscopy, thermogravimetry, and FTIR spectroscopy.     

ICP-MS: a powerful technique for quantitative determination of gold nanoparticles without previous dissolving

A direct and simple inductively coupled plasma mass spectroscopy (ICP-MS) method for the determination of gold nanoparticles (AuNP) with different particle sizes ranging from 5 to 20 nm and suspended in aqueous solutions is described. The results show no significant difference compared to the determination of the same AuNPs after digestion, as claimed by the literature. The obtained limit of quantification of the method is 0.15 μg/L Au(III) that corresponds to 4.40 × 10⁹ AuNP/L, considering spherical AuNPs 15 nm sized. Spike recovery experiments have shown that the sample matrix is a significant factor influencing the accuracy of the measurement. Spike recoveries from 93% to 95% are found for AuNP samples prepared in trisodium citrate, while for deionized H₂O a spike recovery of around 80% was obtained. The sample preparation mode along with the ICP-MS parameters have been optimized and found to be crucial so as to achieve the required accuracy for the direct quantification of AuNP suspensions. The effect of the nanoparticle size upon the ICP-MS signal also was studied, and only significant differences due to the chemical environment and not to the AuNPs size were found.     

A Coumarin-Based Fluorescent Chemosensor for Zn<Superscript>2+</Superscript> in Aqueous Ethanol Media

A coumarin-based fluorescent chemosensor 1 for Zn²⁺ was designed and synthesized. Compound 1 exhibits lower background fluorescence due to intramolecular photoinduced electron transfer. However, upon mixing with Zn²⁺ in 30% (v/v) aqueous ethanol, a “turn-on” fluorescence emission is observed. The fluorescence emission increases linearly with Zn²⁺ concentration in the range 0.5–10 μmol L⁻¹ with a detection limit of 0.29 μmol L⁻¹. No remarkable emission enhancement was, however, observed for other metal ions. The proposed chemosensor was applied to the determination of Zn²⁺ in water samples with satisfactory results.     

Anisotropic gold nanoparticles and gold plates biosynthesis using alfalfa extracts

Industrial and medical applications for gold nanoparticles are extensive, yet highly dependent on their chemical and structural properties. Thus, harnessing the size and shape of nanoparticles plays an important role in nanoscience and nanotechnology. Anisotropic polyhedra and nanoplates were biosynthesized via reduction of 3 mM AuCl₄ ⁻ solution at room temperature. Alfalfa biomass extracts prepared in water and in isopropanol separately were used as reducing agents at pH 3.5 and 3.0, respectively. Nanoparticles observed in the isopropanol extract presented a size range of 30–60 nm, and the morphologies present included 30 nm decahedra and 15 nm icosahedra. Gold nanoplates produced in the water extract were mainly triangular, ranging from 500 nm to 4 μm in size. The resulting nanoparticles and nanoplates can be potentially used in the study of their unique physical properties and for the mechanisms of formation using alfalfa biomass extracts.     

One-step synthesis and antibacterial property of water-soluble silver nanoparticles by CGJ bio-template

In this article, a new synthetic method of nanoparticles with fresh Chinese gooseberry juice (CGJ) as bio-template was developed. One-step synthesis of highly water-soluble silver nanoparticles at room temperature without using any harmful reducing agents and special capping agent was fulfilled with this method. In the process, the products were obtained by adding AgNO₃ to CGJ, which was used as reducing agent, capping agent, and the bio-template. The products of silver nanoparticles with diameter of 10–30 nm have strong water solubility and excellent antibiotic function. With the same concentration 0.047 μg mL⁻¹, the antibacterial effect of water-soluble silver particles by fresh CGJ was 53%, whereas only 27% for silver nanoparticles synthesized using the template method of fresh onion inner squama coat (OISC). The excellent water solubility of the products would enable them have better applications in the bio-medical field. The synthetic method would also have potential application in preparing other highly water-soluble particles, because of its simple apparatus, high yield, mild conditions, and facile operation.