Metallic Ions In Aqueous Solution Research Articles

Hydrothermal Synthesis to Water-stable Luminescent Carbon Dots from Acerola Fruit for Photoluminescent Composites Preparation and its Application as Sensors

Carbon dots (C-dots) possess the attractive properties of high stability, low toxicity, good water solubility, simple synthetic routes as well as size and excitation-dependent photoluminescence (PL).The aim of this work was to synthesize photoluminescent C-dots by hydrothermal method using acerola fruit (Malpighiaemarginata) as a row material, since this fruit contains large number of organic molecules. Studies about the optimal synthesis conditions were performed, where these organic molecules were converted into C-dots by hydrothermal carbonization at 180 ºC for 18 h. The C-dots exhibited a green emission light at 459 nm when excited under UV-light ( λ ex= 370 nm). These nanomaterials were also successfully used to prepare C-dots/poly (vinyl alcohol) luminescent composites (C-dots/PVA). Both C-dots and C-dots/PVA composite films were investigated by using colorimetric visual sensor for Fe3+ metal ions detection. The results show that the prepared C-dots and C-dots/poly presented strong green emission light. The emission spectra of above materials were quenched in the presence of Fe3+ ions. Thus, highly specific “turn off” fluorescence sensing of Fe3+ was achieved using fluorescent C-dots. Regarding, this work describe that the polymeric films as sensors of metallic ions in aqueous solution appears as a new perspectives to design new composite materials.

Facile aerobic construction of iron based ferromagnetic nanostructures by a novel microbial nanofactory isolated from tropical freshwater wetlands

BackgroundIron based ferromagnetic nanoparticles (IONP) have found a wide range of application in microelectronics, chemotherapeutic cell targeting, and as contrast enhancers in MRI. As such, the design of well-defined monodisperse IONPs is crucial to ensure effectiveness in these applications. Although these nanostructures are currently manufactured using chemical and physical processes, these methods are not environmentally conducive and weigh heavily on energy and outlays. Certain microorganisms have the innate ability to reduce metallic ions in aqueous solution and generate nano-sized IONP’s with narrow size distribution. Harnessing this potential is a way forward in constructing microbial nanofactories, capable of churning out high yields of well-defined IONP’s with physico-chemical characteristics on par with the synthetically produced ones.ResultsIn this work, we report the molecular characterization of an actinomycetes, isolated from tropical freshwater wetlands sediments, that demonstrated rapid aerobic extracellular reduction of ferric ions to generate iron based nanoparticles. Characterization of these nanoparticles was carried out using Field Emission Scanning Electron Microscope with energy dispersive X-ray spectroscopy (FESEM–EDX), Field Emission Transmission Electron Microscope (FETEM), Ultraviolet–Visible (UV–Vis) Spectrophotometer, dynamic light scattering (DLS) and Fourier transform infrared spectroscopy (FTIR). This process was carried out at room temperature and humidity and under aerobic conditions and could be developed as an environmental friendly, cost effective bioprocess for the production of IONP’s.ConclusionWhile it is undeniable that iron reducing microorganisms confer a largely untapped resource as potent nanofactories, these bioprocesses are largely anaerobic and hampered by the low reaction rates, highly stringent microbial cultural conditions and polydispersed nanostructures. In this work, the novel isolate demonstrated rapid, aerobic reduction of ferric ions in its extracellular matrix, resulting in IONPs of relatively narrow size distribution which are easily extracted and purified without the need for convoluted procedures. It is therefore hoped that this isolate could be potentially developed as an effective nanofactory in the future.

Nacrelike-structured multilayered polyelectrolyte/calcium carbonate nanocomposite membrane via Ca-incorporated layer-by-layer-assembly and CO2-induced biomineralization

The separation of metallic ions in particular heavy metallic ions in aqueous solution is a great challenge in membrane science. Herein, a simple and facile strategy—Ca2+-incorporated layer-by-layer (LbL) assembly and CO2-induced biomineralization was developed and applied to the preparation of nacrelike-structured multilayered PEI/PSS-CaCO3 nanocomposite membrane on PAN substrate. These nanocomposite membranes showed higher rejection (≥99.3%) and permeable flux (≥49.1Lm−2MPa−1h−1) for divalent metallic ions such as Mg2+, Cu2+, Ca2+, Ni2+, Zn2+, and Cd2+ in aqueous solution compared to the multilayer PEI/PSS or PEI/PSS-CaCO3 membrane prepared by alternate soaking process. High rejection and flux can be attributed to the following three aspects: (i) The incorporation of Ca2+ into PEI and PSS greatly reduces the formation of crosslinked structure of PEI and PSS and probably induces the ordered arrays of amine and sulfonate groups from PEI and PSS on membrane; (ii) Due to limited Ca2+ ions source and spatial limitation of crosslinking of PEI/PSS phase the nanostructured CaCO3 was in-situ formed after CO2-induced biomineralization and created some additional short paths (the bulgy section of PEI/PSS layer) that are beneficial to the permeability of membrane; (iii) Due to the calcification of incorporated Ca2+ ions the formed H+ ions makes amine and sulfonate groups further protonation that improves surface hydrophilicity of membrane. On the basis of a long-term performance stability, high rejection and flux, the nacrelike-structured multilayered PEI/PSS-CaCO3 nanocomposite membrane can be used as a promising membrane in industry for the separation of metallic ions in aqueous solution.

Abiotic degradation of glyphosate into aminomethylphosphonic acid in the presence of metals.

Glyphosate [N-phosphono-methylglycine (PMG)] is the most used herbicide worldwide, particularly since the development of transgenic glyphosate-resistant (GR) crops. Aminomethylphosphonic acid (AMPA) is the main glyphosate metabolite, and it may be responsible for GR crop damage upon PMG application. PMG degradation into AMPA has hitherto been reckoned mainly as a biological process, produced by soil microorganisms (bacteria and fungi) and plants. In this work, we use density functional calculations to identify the vibrational bands of PMG and AMPA in surface-enhanced Raman spectroscopy (SERS) and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra experiments. SERS shows the presence of AMPA after glyphosate is deposited from aqueous solution on different metallic surfaces. AMPA is also detected in ATR-FTIR experiments when PMG interacts with metallic ions in aqueous solution. These results reveal an abiotic degradation process of glyphosate into AMPA, where metals play a crucial role.

Catalytic Ozonation of Citric Acid by Metallic Ions in Aqueous Solution

Ozonation of citric acid in water catalyzed by different ions from the first row of transition metals (Mn2+, Co2+, Ti4+, Fe2+, Cu2+, Ni2+ and Zn2+) was investigated at room temperature. The results showed that at pH=2, where the decomposition of citric acid is negligible by only ozone, the following order of efficiency of metallic ions for the decomposition of citric acid by ozone, and also for the TOC removal, was obtained: Mn2+ > Co2+ > Ti4+ > Fe2+. Cu2+, Ni2+ and Zn2+ showed negligible efficiency under the same experimental conditions. At pH=5.5, Mn2+ and Co2+ showed slightly higher efficiency than at pH=2 while Ti4+ and Fe2+ showed insignificant effect at this pH value. On the other hand, at pH=7 the investigated catalysts showed no obvious catalytic efficiency for the decomposition of citric acid by ozone.

197Au Mössbauer Study of Bimetallic Nanoparticles Prepared by Sonochemical Technique

By ultrasonic wave irradiation, the metallic ions in aqueous solution are reduced to metallic nanoparticles. Using the mixture solution of Au and Pd ions, core(Au)–shell(Pd) structured nanoparticles are prepared. 197Au Mossbauer spectra of core–shell structured nanoparticles contains two components, one is pure Au component due to the inner part of the Au core and the other is the positive isomer shift component due to the alloy layer at the interface of Au core and Pd shell. The thickness of the alloy layer is 0.5∼0.7 nm.

Structured supports for noble catalytic metals: stainless steel fabrics and foils, and carbon fabrics

Conventional structured catalytic structures are constituted by a ceramic or metallic monolith whose wall surface is covered by a porous coating on which the active metal is deposited. To simplify the deposition procedures it is proposed to deposit the active metal on the bare surface of the carrier. The metal deposition is accomplished by the chemical reduction of metallic ions in aqueous solution. Catalytically active systems obtained by anchoring palladium (or ruthenium) on stainless steel supports or carbon fabrics are described. Their activity depends on the operating parameters of the deposition procedure.

Metal colloids employed in the SERS of biomolecules: activation when exciting in the visible and near-infrared regions

Silver, gold and copper colloids have been employed in the study of the nucleic bases cytosine, guanine, their alkyl derivatives 1-methylcytosine, 5-methylcytosine, 1,5-dimethylcytosine, 7-methylcytosine and 9-ethylguanosine. Cytidine, 5′-cytidinemonophosphate and 5′-adenosinemonophosphate have been also studied using silver and copper colloids. The interaction and orientation of these compounds on the metal colloids are interpreted on the basis of the SER spectra obtained, and further compared with interactions with the corresponding metallic ions in aqueous solution. Transmission electronic microscopy and ultraviolet-visible absorption spectroscopy were also employed to characterize the silver and copper colloids before and after aggregation by 1,5-dimethylcytosine. Information on the aggregation process is presented. The activation effect of chloride, perchlorate and nitrate anions on the silver colloids employed is studied for both the visible and near-infrared regions. An assessment of the effectiveness of each colloid is made at different excitation lines. Finally, an explanation of the mechanism through which these anions exert their activation effect is given on the basis of the morphologies of the particles contained in the colloid.

Formation mechanism of tapering of crystals: a comparative study between potassium dihydrogen phosphate crystals and natural quartz crystals

A comparative study on the tapering of natural quartz and potassium dihydrogen phosphate (KDP) crystals has been made. Both tapered natural quartz crystals and KDP crystals display similar surface microtopography featuring a large number of tiny elongated growth islands and striations on the tapered regions. In addition to the well accepted fact that trivalent metallic ions in aqueous solution can cause the tapering of KDP crystals, we find that Pb 2+ has the same effect. This possibly originates from preferentially settled impurities and embryonic crystallites along the edges between two major faces.

Determination of lead and copper in kerosene by electrothermal atomic absorption spectrometry: stabilization of metals in organic media by a three-component solution

The instability of copper and lead in kerosene and in analytical organic solutions is the main problem with their direct determination. When propan-1-ol is added to a mixture of kerosene and water a homogenous three-component solution is obtained. It was verified that the metals in this solution placed in an autosampler cup are stable for at least 3 h in a closed calibrated flask and remain stable for at least 24 h. The three-component solutions containing purified kerosene and enriched with metallic ions in aqueous solution or with copper or lead cyclohexanebutyrate or tetraethyllead are also stable. In spite of some differences in the absorption pulses, the maximum pyrolysis temperatures, characteristic masses and precision are similar for the three-component solutions in comparison to aqueous solutions.

Complex formation between poly(vinyl alcohol) and metallic ions in aqueous solution

AbstractAs the basic research for the study of complex reactions in polymers, the complex formation of poly(vinyl alcohol) (PVA) with copper and other metals was tried. Spectroscopy, pH titration, and elementary analysis were employed in the reaction of PVA and Cu(II) ions in aqueous solution. The complexing protonation was found in the higher pH region (above 7.0), and the maximum absorptions at 640 and 260 nm were observed. These ϵmax were proportional to the concentrations of Cu(II) ions bound to the hydroxyl groups of PVA. Formation constants of the PVA–Cu(II) complexes were measured by applying a modified Bjerrum's method. The effects of the ratio Tcu2+/THL, the anions in copper salts, and the degree of polymerization on the formation constants were studied. Four hydroxyl groups combined with one Cu(II) ion in the pH range above 7.0. The stability constants for the complexes of PVA with bivalent transition metallic ions were in agreement with the Irving‐William's series. The changes in viscosity, solubility, tacticity, mechanochemical phenomenon, and the other properties based on the complex formation are discussed.

Study of Detergency. XVIII.

It is well known that alkaline earth metallic ions in aqueous solution influences to detergency.In this report, an investigation was made on the detergency of LAS to triglycerides in the presence of Ca ion. It was found that there is a concentration of Ca ion to give the maximum detergency, which increases in proportion to the concentration of LAS.Namely, there is an optimum ratio between the concentration of Ca ion and Na ion in LAS on detergency, and it is independent of the concentration of LAS.This fact suggests us that Na salt of LAS and Ca salt formed by double decomposition of a part of LAS with Ca ion in aqueous solution form a kind of complex micell, which may increase the adsorption of LAS on soil.It is considered that LAS is not only adsorbed on the surface of soil but penetrates into the soil to form a sort of liquid crystal, and that the adsorption of LAS to soil decreases the adhesive energy between soil and glass to lower the interfacial tention between soil and aqueous solution of LAS, and may improve the detergency of the system.

Study of Detergency. XIII.

It is well known that alkaline earth metallic ions in aqueous solution influences to detergency.In this report, an investigation was made on the detergency of LAS to triglycerides in the presence of Ca ion. It was found that there is a concentration of Ca ion to give the maximum detergency, which increases in proportion to the concentration of LAS.Namely, there is an optimum ratio between the concentration of Ca ion and Na ion in LAS on detergency, and it is independent of the concentration of LAS.This fact suggests us that Na salt of LAS and Ca salt formed by double decomposition of a part of LAS with Ca ion in aqueous solution form a kind of complex micell, which may increase the adsorption of LAS on soil.It is considered that LAS is not only adsorbed on the surface of soil but penetrates into the soil to form a sort of liquid crystal, and that the adsorption of LAS to soil decreases the adhesive energy between soil and glass to lower the interfacial tention between soil and aqueous solution of LAS, and may improve the detergency of the system.

Hydroxyaldimines and hydroxyketimines as organic precipitants

The paper introduces several o-hydroxyaldimines and o-hydroxyketimines as new organic precipitants for different metallic ions in aqueous solution. Careful studies of the reaction of these ligands with different metallic ions show that these are well suited for the detection of small amounts of several metallic ions in solutions. Like salicylimine, β-hydroxynaphthaldimines and o-hydroxyacetophenonimines are suitable for the estimation of copper and nickel in aqueous solution.