Addition Of Sulfide Ions Research Articles

Silver nanoparticles capped with carbon dots as a fluorescent probe for the highly sensitive "off-on" sensing of sulfide ions in water.

The present study illustrates the synthesis of silver nanoparticles capped with carbon dots (AgNPs-CDs) and their application towards the sensitive and selective sensing of sulfide ions by colorimetry and spectrofluorimetry methods. The CDs were prepared from l-asparagine by pyrolysis at 234°C. The as-synthesized CDs were then utilized as reducing and capping agents for the synthesis of AgNPs-CDs by the wet chemical method. The size of the AgNPs-CDs was found to be ~ 5.2nm. They show a characteristic surface plasmon resonance band at 417nm and emission maximum at 441nm when excited at 348nm. Since the AgNPs were formed on the surface of CDs, the emission intensity of AgNPs-CDs was drastically decreased in contrast to that of CDs. The as-synthesized AgNPs-CDs were then successfully used for the sensitive and selective determination of sulfide ions. The addition of 0.1μM sulfide ions to AgNPs-CDs leads to a decrease in the absorbance intensity at 417nm aside turning from yellow to colorless. In the contrary, the emission was "turned on" after the addition of sulfide ions. The decrease in the absorbance and increase in the emission were attributed to the rapid formation of Ag2S. Finally, the practical application of the present method was demonstrated by determining dissolved H2S in tap water samples.

PH triggered green synthesized silver nanoparticles toward selective colorimetric detection of kanamycin and hazardous sulfide ions

The interaction among the biologically synthesized silver nanoparticles (AgNPs) and industrially useful antibiotic kanamycin or environmentally hazardous sulfide ions led to the development of a possible colorimetric sensor for the selective detection of kanamycin and sulfide ions. In this study, a facile green protocol toward the synthesis of silver nanoparticles (AgNPs) was established while Epigallocatechin gallate (EGCG) was used as reducing and stabilizing agents, for the first time. The as-synthesized nanoparticles were characterized by UV–visible spectroscopy, high resolution transmission electron microscopy (HR-TEM) and dynamic light scattering (DLS) techniques. Detection of kanamycin and sulfide ions was established based on the SPR technique. The yellow color of the AgNPs solution turned to reddish pink in the presence of kanamycin, accompanying the decrease in intensity of SPR band. In contrast, AgNPs solution turned to colorless upon the addition of sulfide ions. The sensitivity and selectivity of AgNPs toward other interference antibiotics/anions were studied. Moreover, the effect of the concentration of kanamycin and sulfide ions in the nanoparticle solution was investigated and the LOD (limit of detection) for kanamycin and sulfide ions were found to be 0.96 μM and 1.62 μM, respectively. The results indicate that the proposed technique is very efficient for the colorimetric detection of kanamycin and sulfide ions.

Kinetics of dissolution of hydrogenated carbon steel in electrolytes with pH close to neutral

The kinetics of dissolution of hydrogenated carbon steel in the NS4 solution simulating electrolyte under a layered coating of underground pipework is considered. It is shown that hydrogenation of metal accelerates active iron dissolution in media with pH close to neutral values. Addition of sulfide ions into the NS4 solution causes a significant negative shift in the steel corrosion potential and an increase in anodic current in two regions of potential: the prepassive state and in the vicinity of the metal corrosion potential. The cause of the accelerating effect of sulfide is hydrogenation of steel.

Graphene quantum dots combined with copper(II) ions as a fluorescent probe for turn-on detection of sulfide ions

A fluorescent probe for the sensitive and selective determination of sulfide ions is presented. It is based on the use of graphene quantum dots (GQDs) which emit strong and stable blue fluorescence even at high ionic strength. Copper(II) ions cause aggregation of the GQDs and thereby quench fluorescence. The GQDs-Cu(II) aggregates can be dissociated by adding sulfide ions, and this results in fluorescence turn on. The change of fluorescence intensity is proportional to the concentration of sulfide ions. Under optimal conditions, the increase in fluorescence intensity on addition of sulfide ions is linearly related (r 2 = 0.9943) to the concentration of sulfide ions in the range from 0.20 to 20 μM, and the limit of detection is 0.10 μM (at 3 σ/s). The fluorescent probe is highly selective for sulfide ions over some potentially interfering ions. The method was successfully applied to the determination of sulfide ions in real water samples and gave recoveries between 103.0 and 113.0 %.

Electrochemical Behavior of X52 Steel in a CO2 Environment in the Presence of Acetate and sulfide

The objective of this study is to evaluate the combined effect of sulfide and acetate on the corrosion behavior of X52 steel in a CO2 environment. The tests were conducted in a 0.5 M NaCl solution (25 °C). Corrosion rate and behavior were investigated using the following three electrochemical techniques: (a) linear polarization resistance, (b) potentiodynamic polarization, and (c) electrochemical impedance spectroscopy. The morphology of surface corrosion products were analyzed using field emission scanning electron microscopy/energy dispersive spectroscopy and X-ray diffraction tests. The results show that the addition of sulfide ions decreased the corrosion rate of X52 steel sample. The inhibitive effect of sulfide ions was related to protective pyrite FeS layer on the electrode surface. Furthermore, in the presence of sulfide, acetate increased the X52 steel corrosion rate by enhancing the cathodic reaction. On the contrary, in the absence of sulfide, acetate decreased the corrosion rate of the X52 steel sample when the pH solution was increased.

Full-Color Tuning of Surface Plasmon Resonance by Compositional Variation of Au@Ag Core–Shell Nanocubes with Sulfides

In the present study, we demonstrate the precise tuning of surface plasmon resonance over the full visible range by compositional variation of the nanoparticles. The addition of sulfide ions into the Au@Ag core-shell nanocubes generates stable Au@Ag/Ag(2)S core-shell nanoparticles at room temperature, and the plasmon extinction maximum shifts to the longer wavelength covering the entire visible range of 500-750 nm. Based on the optical property, the Au@Ag core-shell nanocubes are employed as a colorimetric sensing framework for sulfide detection in water. The detection limit is measured to be 10 ppb by UV-vis spectroscopy and 200 ppb by naked eyes. Such nanoparticles would be useful for decoration and sensing purposes, due to their precise color tunability and high stability.

Regularities of gold anodic dissolution in thiocarbamide solutions

It is shown that the gold dissolution in thiocarbamide electrolytes containing sulfide ions in the pH range from 1 to 4 proceeds with a current efficiently of almost 100%, and a change in solution acidity has a weak effect on the process. The oxidation of thiocarbamide to formamidine disulfide proceeds at the potentials around 1.1 V and depends on the pH of solution. When the pH value is raised, the thiocarbamide oxidation potential shifts in the negative direction and approaches the potential of gold dissolution. It is found that, in the absence of catalytically active species, the gold dissolution rate in thiocarbamide solutions in the pH range from 6 to 10 is vary low. At these pH values, as well as in the acidic solutions, an addition of less than 10−4 M sulfide ions to thiocarbamide electrolyte accelerates the gold dissolution at the potentials about 0.6 V. It is shown that sulfide ions in the concentration above 10−4 M inhibit the process. At pH 11, the gold dissolution proceeds also with no special addition of sulfide ions. This is associated with the formation of sulfide ions as a result of accelerated decomposition of thiocarbamide and formamidine disulfide with increasing pH value. It is found that in the pH range from 12 to 13, the processes of gold dissolution and thiocarbamide oxidation are inhibited as a result of the formation of passive film on the electrode surface. Probably, the film consists of elemental sulfur.

Effect of Sulfide Ions on the Corrosion Behaviour of Mild Steel in Acetate Buffer

The corrosion behaviour of mild steel was investigated in acidic acetate buffer solution using impendance and potential measurements. It was found that there are two dissolution rates resulting from the duplex nature of the formed oxides. The dissolution rates were found to depend on the dissolving acetate buffer solution pH and the dissolution temperature. In all cases, the film thickness was found to decrease with time of corrosion according to the relation Cm-1 = (Cm0)-1 - kdt1/2. It was found that addition of sulfide ions increases the dissolution rate and increases the rate of hydrogen evolution reaction but does not affect the mechanism of cathodic process. The role of sulfide ions on the corrosion behaviour of steel in acetate buffer solutions is revealed by the complex plane impendance analysis.