A Fluorogenic Reagent, 7-Phenylsulfonyl-4-(2,1,3-benzoxadiazolyl) Isocyanate for Alcohols, with Development Based on the Empirical Method for Prediction

During the course of our studies, we found the relationship between the fluorescence characteristics (the fluorescence intensity and the maximum excitation and emission wavelengths) of benzofurazan compounds and the sum and difference of Hammett substituent constants (σp) at the 4- and 7- positions. This prompted us to design a useful fluorogenic derivatization reagent having the benzofurazan skeleton for alcohols along this line of thought. Accordingly, the fluorogenic derivatization reagents, which have no fluorescence themselves, 7-N,N-dimethylaminosulfonyl-4-(2,1,3-benzoxadiazolyl) isocyanate (DBD-NCO), 7-phenylsulfonyl-4-(2,1,3-benzoxadiazolyl) isocyanate (PSBD-NCO), and 7-methylsulfonyl-4-(2,1,3-benzoxadiazolyl) isocyanate (MSBD-NCO), were synthesized. Among the derivatives derived from the three reagents, that from PSBD-NCO was most strongly fluorescent. PSBD-NCO reacted with 1-octanol within 4 h in acetonitrile solution in the absence of a catalyst at 60 °C. The derivatives with four alcohols (1-octanol, 1-nonanol, 1-decanol, and 1-undecanol) were separated on a reversed-phase column and detected fluorimetrically at 490 nm with the excitation at 368 nm. The detection limits were at the 10-femtomole level. PSBD-NCO was superior to other fluorescent-labeling reagents with regard to the avoidance of the interfering peaks derived from the reagents themselves and degradation products in the chromatogram. The effectiveness of our approach is disccussed in terms of the development of new fluorogenic reagents.     

Fluorogenic Zn(II) and chromogenic Fe(II) sensors based on terpyridine-substituted tetraphenylethenes with aggregation-induced emission characteristics

Terpyridine-containing tetraphenylethenes (TPEs) are synthesized and their optical and metal sensing properties are investigated. They are practically nonluminescent in the solution state but become highly emissive as nanoparticle suspensions in poor solvents or thin films in the solid state, demonstrating a novel phenomenon of aggregation-induced emission (AIE). The emission of the nanoaggregates of TPEs is pH-sensitive: it is decreased and eventually quenched upon protonation of their terpyridine units because of their AIE nature. The TPEs can work as "turn-off" fluorescent chemosensors for metal ions and display different fluorescence responses to various metal ions. A characteristic red shift in the emission spectra is observed in the presence of Zn(2+), which facilitates the discrimination of Zn(2+) from other metal ions. Because of the metal-to-ligand-charge-transfer process, terpyridine-substituted TPEs display an obvious magenta color upon selectively binding with Fe(2+), allowing a rapid identification of Fe(2+) in the aqueous media by naked eyes.     

A Relatively Simple Test for the Direct Determination of the Cysteine Content in Photographic Gelatin Using a Thiol-Specific Fluorogenic Reagent

Abstract

This report describes the development and validation of a direct measurement of cysteine in photographic gelatin using a fluorogenic reagent, ammonium 7-fluoro-2,1,3-benzoxadiazole 4-sulphonate (SBD-F). This unique analytical approach greatly simplifies the measurement of cysteine without sacrificing the quality of the information obtained. No complicated acid hydrolysis or difficult high-performance liquid chromatographic separations are required. SBD-F is water soluble and thiol specific. SBD-Fhas many excellent features which allow direct labeling of the cysteine thiol in gelatin solutions under controlled laboratory conditions. At phi 8.0 the reaction kinetics arc complete in 1 hour at 60 °C. Additionally, the probe is not naturally fluorescent and thus no separation step is required for removal of unbound reagent. The analytical test is both simple and rapid. This method allows determination of cysteine content by fluorescence emission in less than 2 hours.     

Mercury(II) selective membrane electrode based on 1,3-bis(2-methoxybenzene)triazene

A plasticized poly (vinyl chloride) membrane electrode based on 1,3-bis(2-methoxybenzene)triazene (MBT) for highly selective determination of mercury(II) has been developed. The electrode showed a good Nernstian response (30.2 ± 0.3 mV decade^− 1) over a wide concentration range (1.0 × 10^− 7−1.0 × 10^− 2 mol L^− 1). The limit of detection was 5.0 × 10^− 8 mol L^− 1. The electrode has a response time about 15 s and can be used for at least 1 month without observing any deviation from Nernstain response. The proposed electrode revealed an excellent selectivity toward mercury(II) ion over a wide variety of alkali, alkaline earth, transition, and heavy metal ions and could be used in the pH range 2.6–4.2. The electrode was used in the determination of Hg²⁺ in aqueous samples and as an indicator electrode in potentiometric titration of Hg(II) ions.     

Highly Selective Potentiometric Membrane Sensor for Hg(II) Based on Bis(Benzoyl Acetone) Diethylene Triamine

A new ion selective PVC membrane sensor is described based on bis(benzoyl acetone) diethylene triamine as a potentiometric sensor for Hg²⁺ ions. The membrane having bis(benzoyl acetone) diethylene triamine as an electroactive material, sodium tetraphenyl phthalate (NaTPB), and dibutyl phthalate (DBP) as an anion excluder in PVC matrix in the percentage ratio 4.21:2.11:60.25:33.43 (Ionophore:NaTPB:DBP:PVC) (w/w) of exhibits a linear response to Hg²⁺ of 1.0 times 10^-6 to 1.0 times 10^-1 M with a limit of detection of 3.7 times 10^-7 M and with a slope of 29.8 plusmn 1.0 mV/decade over the pH range of 2.0-11.5. Selectivity coefficients for Hg(II) relative to a numbers of potential interfering ions were investigated. The sensor is highly selective for Hg²⁺ ions over a large number of mono-, bi-, and trivalent cations. Normal interferents like Ag⁺ and Cd²⁺ do not interfere in the working of the sensor. The sensor has been found to be chemically inert to other ions and showing a fast response time of 1 s and was used over a period of three months with a good reproducibility. The sensor was successfully applied to determine mercury(II) in water samples with satisfactory results.     

Selective extraction of zinc(II) over iron(II) from spent hydrochloric acid pickling effluents by liquid-liquid extraction

The selective removal of zinc(II) over iron(II) by liquid–liquid extraction from spent hydrochloric acid pickling effluents produced by the zinc hot-dip galvanizing industry was studied at room temperature. Two distinct effluents were investigated: effluent 1 containing 70.2 g/L of Zn, 92.2 g/L of Fe and pH 0.6, and effluent 2 containing 33.9 g/L of Zn, 203.9 g/L of Fe and 2 M HCl. The following extractants were compared: TBP (tri-n-butyl phosphate), Cyanex 272 [bis(2,4,4-trimethylpentyl)phosphinic acid], Cyanex 301 [bis(2,4,4-trimethylpentyl) dithiophosphinic acid] and Cyanex 302 [bis(2,4,4-trimethylpentyl) monothiophosphinic acid]. The best separation results were obtained for extractants TBP and Cyanex 301. Around 92.5% of zinc and 11.2% of iron were extracted from effluent 1 in one single contact using 100% (v/v) of TBP. With Cyanex 301, around 80–95% of zinc and less than 10% of iron were extracted from effluent 2 at pH 0.3–1.0. For Cyanex 272, the highest extraction yield for zinc (70% of zinc with 20% of iron extraction) was found at pH 2.4. Cyanex 302 presented low metal extraction levels (below 10%) and slow phase disengagement characteristics. Reactions for the extraction of zinc with TBP and Cyanex 301 from hydrochloric acid solution were proposed.     

A simplified two-fluid theory for helium(II)

We construct the equations for the incompressible two-fluid model of He(II). These equations provide a set of partial differential equations governing the thermomechanical behaviour of liquid helium below the λ-point. This set of equations is similar but slightly simpler than the equations originally proposed by Landau [1]. Following the standard approach of continuum mixture theory, we derive thermodynamic restrictions on the incompressible two-fluid model. Finally, we establish conditions which ensure that classical solutions of certain initial-boundary value problems for the simplified theory depend continuously on the initial data.     

Preconcentration and Voltammetric Determination of Mercury(II) at a Chemically Modified Glassy Carbon Electrode

In this work, the organic compound 2-mercaptobenzimidazole was covalently bound on the surface of a glassy carbon rod, via silanization, yielding a material capable of selectively complexing Hg(2+) ions. This material was applied as an electrode for voltammetric determination of mercury(II) following its nonelectrolytic preconcentration. After exchanging the medium, the voltammetric measurements were carried out by anodic stripping in the differential pulse mode (pulse amplitude, 50 mV; scan rate, 1.25 mV s(-)(1)) using 10(-)(2) mol L(-)(1) NaSCN solution as supporting electrolyte. An anodic stripping peak was obtained at 0.06 V (vs SCE) by scanning the potential from -0.3 to +0.3 V. After a 5 min preconcentration period in a pH 4.0 Hg(2+) solution, this electrode shows increasing voltammetric response in the range 0.1-2.2 μg mL(-)(1), with a relative standard deviation of 5% and a practical detection limit of 0.1 μg mL(-)(1) (5.0 × 10(-)(7) mol dm(-)(3)). Compared with the conventional stripping approach, this chemically modified glassy carbon electrode procedure presented good discrimination against interference from Cu(II) in up to 10-fold molar excess.     

Selective gold-nanoparticle-based "turn-on" fluorescent sensors for detection of mercury(II) in aqueous solution

A new gold-nanoparticle (AuNP)-based sensor for detecting Hg(II) ions in aqueous solution has been developed. Rhodamine B (RB) molecules that are highly fluorescent in bulk solution fluoresce weakly when they are adsorbed onto AuNP surfaces as a result of fluorescence resonance energy transfer and collision with AuNPs. In the presence of metal ions such as Hg(II), RB molecules are released from the AuNP surface and thus restore the florescence of RB. The modulation of the photoluminescence quenching efficiency of RB-AuNPs in the presence of Hg(II) ions can achieve a large turn-on fluorescence enhancement (400-fold) in aqueous solution, and the entire detection takes less than 10 min. We have improved the selectivity of the probe further by modifying the AuNP surfaces with thiol ligands (mercaptopropionic acid, mercaptosuccinic acid, and homocystine) and adding a chelating ligand (2,6-pyridinedicarboxylic acid) to the sample solutions. Under the optimum conditions, the selectivity of this system for Hg(II) over other metal ions in aqueous solutions is remarkably high (50-fold or more), and its LOD for Hg(II) in the matrix pond water is 2.0 ppb. Our approach demonstrated the feasibility of using the developed nanosensor for rapid determination of Hg(II) in aqueous environmental samples and in batteries.     

Cystine-modified biomass for Cd(II) and Pb(II) biosorption

The surface of dried biomass of baker's yeast was modified by crosslinking cystine with glutaraldehyde. X-ray photoelectron spectroscopy and microscope were used to characterize the modified biomass. The adsorption capacity of the modified biomass for Cd(2+) and Pb(2+) showed an increase compared with the pristine biomass due to the presence of cystine on the biomass surface. Experimental data showed that the adsorption of the two metal ions increased with time until equilibrium was achieved. The adsorption capacities for Cd(2+) and Pb(2+) were 11.63 and 45.87 mg g(-1), respectively, which were determined from the Langmuir isotherm. The loaded biosorbent was regenerated using HCl solution and could be used repeatedly at six times with little loss of uptake capacity. FTIR spectroscopy revealed that carboxyl, amide, and hydroxyl groups on the biomass surface were involved in the adsorption of Cd(2+) and Pb(2+).     

Selective elimination of lead(II) ions by alginate/polyurethane composite foams

A new type of adsorbent which is capable of selectively adsorbing lead(II) ions (Pb(2+)) was developed. The adsorbent was generated by reaction of sodium alginate with NB-9000B, a polyisocyanate type of prepolymer of polyurethane. The adsorbent was a hydrophilic and flexible alginate/polyurethane composite foam (ALG/PUCF) with the alginate chemically immobilized in the cell walls of the foam. Acid-base titration was used to quantify the concentration of carboxyl groups, which are present on the alginate molecules of the ALG/PUCF, functioning as the essential sites for binding Pb(2+). For the optimized ALG/PUCF, the carboxyl was found to be 38.2+/-1.2mumol/g of dry weight. The capacity for adsorbing Pb(2+) ions in 1.0g of dry weight of the optimized ALG/PUCF was found to be 16.0+/-2.1mumol, indicating that ion exchange was the essential mechanism for adsorbing Pb(2+) ions. The adsorption capacity was found to be highly sensitive to the pH of the sample solution; lower pH (<3) significantly decreased the adsorption. Competing ions such as Mg(2+), Ca(2+), and Cd(2+) also caused a decrease in selectivity and capacity for Pb(2+) adsorption, although the effect was less pronounced than the effect of pH. The ALG/PUCF is highly stable, flexible and easy to use. ALG/PUCF is also reusable after regeneration with ethylenediamine-N,N,N',N'-tetraacetic acid, disodium salt (EDTA-2Na). Due to these features, this adsorbent may be highly useful for elimination of Pb(2+) ions from contaminated water.     

Development of a New Selective Optical Sensor for Cd(II) Ions Based on 4-Hydroxy Salophen

A new sensor membrane based on immobilization of 4-hydroxy salophen on triacetyl cellulose has been developed for the determination of Cd(II) ions that displays excellent performance. The sensing membrane is capable of spectrophotometric determining of Cd(II) with an outstanding high selectivity over a dynamic range between 1.0$,times 10^{-6}$ and 5.0$,times 10^{-2}$ mol L$^{-1}$ with a limit of detection of 5.3 $,times 10^{-7}~$mol L $^{-1}$ (0.06 $mu$g mL $^{-1}$ The sensor shows a fast response time ($≪ {5}~$ min) and the membrane can be used for more than two months without observing any major deviation. The optode revealed very good selectivity with respect to many cations including alkali, alkaline earth, transition and heavy metal ions. The proposed sensor could be used to determine cadmium ions in water and waste water samples. Different experimental parameters such as variable affecting on sensor preparation and pH of the sample solution plus response time were studied. The optodes developed in the present work were found to be stable, cost effective, easy to prepare, and efficient for direct determination of Cd(II) in a variety of aqueous samples using spectrophotometry, with satisfactory results.      

A novel starch-based adsorbent for removing toxic Hg(II) and Pb(II) ions from aqueous solution

A novel effective starch-based adsorbent was prepared through two common reactions, which included the esterification of starch with excess maleic anhydride in the presence of pyridine and the cross-linking reaction of the obtained macromonomer with acrylic acid by using potassium persulphate as initiator. The percentage of carboxylic groups of the macromonomer ranged from 14% to 33.4%. The cross-linking degree of the adsorbent was tailored with the amount of acrylic acid which varied from 10 wt% to 80 wt%. Both Fourier transform infrared spectra and thermogravimetric analysis results verified the structure of the adsorbent. The maximum gel fraction and swelling ratio of the adsorbent were about 72% and 6.25, respectively, and they were able to be adjusted with the amount of monomers. The weight loss percentage of the adsorbent could reach 96.9% after immersing in the buffer solution that contained α-amylase for 14 h. It was found that the adsorption capacities of the adsorbent for lead and mercury ions could be 123.2 and 131.2 mg/g, respectively. In addition, the adsorbent was able to remove ca. 51-90% Pb(II) and Hg(II) ions that existed in the decoctions of four medicinal herbals.     

Molecular Imprinted BiVO4 Microswimmers for Selective Target Recognition and Removal

Analogous to photosynthetic systems, photoactive semiconductor-based micro/nanoswimmers display biomimetic features that enable unique light harvesting and energy conversion functions and interactions with their surroundings. However, these artificial swimmers are usually non-selective and provide ineffective target recognition, resulting in poor surface analyte binding that affects the overall reactivity and motion efficiency. Here, the surface engineering of light-driven BiVO₄ microswimmers by molecular imprinting polymerization is presented. After embedding surface recognition sites, the modified microswimmers can self-propel in a solution of a target molecule, without requiring toxic fuels, and degrade the target selectively in a pollutant mixture. These findings show that optimizing the design of semiconductor-based microswimmers with specific target recognition cavities on their surface is a promising strategy to achieve selective capture and degradation of organic pollutants, which is otherwise impossible because of the non-selective behavior of photogenerated reactive radicals. Moreover, this study provides a unique strategy to enhance the motion capabilities of single-component photocatalytic microswimmers in a specific chemical environment.     

Selective adsorption behavior of Pb(II) by mesoporous silica SBA-15-supported Pb(II)-imprinted polymer based on surface molecularly imprinting technique

In this study, a new Pb(II) ion-imprinted polymer (Pb(II)-IIP), which can be used for selective adsorption of Pb(II) from aqueous solutions, was successfully prepared based on the supported material of ordered mesoporous silica SBA-15 with the help of surface molecular imprinting technology. The prepared polymer was characterized by Fourier transmission infrared spectrometry, X-ray diffraction, transmission electron microscope and nitrogen adsorption-desorption isotherm. The results showed that the synthesized polymer possessed high ordered mesoporous structure. The adsorption behavior of the adsorbents for Pb(II) was investigated using batch experiments. The Pb(II)-IIP showed fast kinetics, high selectivity and satisfied adsorption capacity for adsorption of Pb(II). Under the optimum experimental condition, Pb(II) adsorption process over Pb(II)-IIP follows pseudo-second-order reaction kinetics and follows the Langmuir adsorption isotherm. In addition, the thermodynamic parameters calculated from the adsorption data suggested that the adsorption of Pb(II) onto Pb(II)-IIP was a spontaneous and exothermic nature of the process.     

Magnetic gamma-Fe(2)O(3) nanoparticles coated with poly-l-cysteine for chelation of As(III), Cu(II), Cd(II), Ni(II), Pb(II) and Zn(II)

An anaerobic attached-growth bioreactor (AAGBR) of 3.52 L was operated for 510 days to treat sulfide-laden organic wastewater where nitrate and nitrite were introduced as electron acceptors. When the influent sulfide was kept at 200mg S(2-)-S/L and organic carbon was increased from 20 to 33.6 mg C/L, and the hydraulic retention time decreased from 41.4 to 2.67 h, the removal rates of sulfide and organic carbon reached 99.9% and 91.8% at the loading rates of 1800 mg S(2-)-S/(Ld) and 302.4 mg C/(Ld), respectively. Simultaneously, the introduced electron acceptors of nitrate and nitrite were, respectively, removed by 99.9% and 99.9% at the loading rates of 472.5 mg NO(3)(-)-N/(Ld) and 180 mg NO(2)(-)-N/(Ld). Inside the AAGBR, both autotrophic and heterotrophic denitrification processes were noted to take place. When the influent organic carbon was increased from 20 to 33.6 mg C/L, the nitrate and nitrite consumed for heterotrophic denitrification accounted for 27.3% and 48.5%, respectively. This simultaneous autotrophic and heterotrophic desulfurization-denitrification process has provided a demonstration of the possibility to eliminate sulfide and organic carbon with the presence of nitrate and nitrite.