II), Bi Research Articles

Modulating NFO@N‐MWCNTs/CC Interfaces to Construct Multilevel Synergistic Sites (Ni/Fe‐O‐N‐C) for Multi‐Heavy Metal Ions Sensing

AbstractA hierarchical heterogeneous composite electrode of NiFe2O4@nitrogen‐doped multi‐walled carbon nanotubes/carbon cloth (NFO@N‐MWCNTs/CC) is prepared via a dip‐coating method, followed by a hydrothermal process. The flexible carbon cloth (CC) substrate provides robust support and the cross‐linked nitrogen‐doped multi‐walled carbon nanotubes (N‐MWCNTs) on the CC form a highly porous network with a large specific area that facilitates electron‐transfer. The stable support strengthens the framework and prevents pore structure disorder within the porous network, that could lead to the structural instability of the active sites. The decorated NiFe2O4 nanoparticles offer abundant active sites for enhanced electrocatalytic activity. Benefiting from the synergistic effect of the 3D hierarchical heterogeneous microstructure and multilevel bimetallic oxide active site (Ni/Fe‐O‐N‐C) constructs, the NFO@N‐MWCNTs/CC electrode achieves stable detection of multiple heavy metal ions (HMIs) with high reproducibility. The modified electrode allowed stable detection of multiple heavy metal ions with high reproducibility. The sensitivities of the electrode for Cd(II), Pb(II), Bi(III), and Hg(II) are 344.98, 441.02, 176.484, and 371.099 µA µm−1, respectively. The assay recoveries ranged from 95.3% to 106.8%, highlighting its practical applicability. This study provides innovative composites and theoretical insights to facilitate further advances in the simultaneous high‐performance detection of heavy metal ions.

4-[(E)-2-(1-Pyrenyl)Vinyl]Pyridine Complexes: How to Modulate the Toxicity of Heavy Metal Ions to Target Microbial Infections.

Pyrene derivatives are regularly proposed for use in biochemistry as dyes due to their photochemical characteristics. Their antibacterial properties are, however, much less well understood. New complexes based on 4-[(E)-2-(1-pyrenyl)vinyl]pyridine (PyPe) have been synthesized with metal ions that are known to possess antimicrobial properties, such as zinc(II), cadmium(II), and mercury(II). The metal ion salts, free ligand, combinations thereof, and the coordination compounds themselves were tested for their antibacterial properties through microdilution assays. We found that the ligand is able to modulate the antibacterial properties of transition metal ions, depending on the complex stability, the distance between the ligand and the metal ions, and the metal ions themselves. The coordination by the ligand weakened the antibacterial properties of heavy metal ions (Cd(II), Hg(II), Bi(III)), allowing the bacteria to survive higher concentrations thereof. Mixing the ligand and the metal ion salts without forming the complex beforehand enhanced the antibacterial properties of the cations. Being non-cytotoxic itself, the ligand therefore balances the biological consequences of heavy metal ions between toxicity and therapeutic weapons, depending on its use as a coordinating ligand or simple adjuvant.

Solvent Extraction with Cyanex 923 to Remove Arsenic(V) from Solutions.

The removal of harmful arsenic(V) from aqueous solutions using Cyanex 923 (solvation extractant) was investigated using various experimental variables: equilibration time, the acidity of the aqueous phase, temperature, extractant and arsenic concentrations, and O/A ratio. Cyanex 923 extracted As(V) (and sulfuric acid) from acidic solutions; however, it could not be used to remove the metal from slightly acid or neutral solutions. The extraction of arsenic is exothermic and responded to the formation of H3AsO4·nL species in the organic phase (L represents the extractant, and the stoichiometric factor, n = 1 or 2, depends on the acidity of the aqueous phase). Extraction isotherms are derived from the experimental results. Both arsenic and sulfuric acid loaded onto the organic phase can be stripped with water, and stripping isotherms are also derived from the experimental results. The selectivity of the system against the presence of other metals (Cu(II), Ni(II), Bi(III), and Sb(III)) is investigated, and the ability of Cyanex 923 to extract As(V) and sulfuric acid compared to the use of other P=O-based solvation reagents, such dibutyl butylphosphonate (DBBP) and tri-butyl phosphate (TBP), is also investigated.

Synergistic enhancement of peroxymonosulfate activation by bimetallic (Bi, Fe) supported NaHCO3 activated and urea-modified biochar for sulfamethoxazole degradation: DFT calculations, toxicity assessments, and mechanistic studies

Advanced oxidation processes based on Fenton-like reactions to activate peroxymonosulfate (PMS) for degrading antibiotics face challenges due to insufficient PMS activation and Fe (III)/Fe (II) recycling. Therefore, developing iron-based bimetallic catalyst for sufficient PMS activation and Fe (III)/Fe (II) recycling is critical. Herein, bimetallic (Bi, Fe) NPs supported NaHCO3 activated and urea-modified biochar (Bi-Fe/N-BC) composite were synthesized through two-step hydrothermal method. The Bi-Fe/N-BC/PMS system reached 96.6% conversion, which is approximately 6.01 times greater than BC (k = 0.0110 min−1), 2.44 times greater than N-BC (k = 0.0273 min−1), and 1.84 times greater than Bi-Fe/BC (k = 0.0362 min−1) and 1.78 times greater than Bi-Fe/N-BC system (k = 0.0374). The enhanced performance could be attributed to Fe (III)/Fe (II) recycling facilitated by Bi (I)/Bi (III) and Bi (II)/Bi (III) couples and the formation of nitrogen-active sites, which resulted in synergistic enhancement between the non-radical and radical mechanisms. Furthermore, the composite Bi-Fe/N-BC exhibited a higher surface area (147.50 m2/g) than Bi-Fe/BC (103.26 m2/g), increasing the number of active sites accessible for PMS activation. Reactive species analysis revealed the presence of SO4•─, •OH, O2•−, and 1O2 species, with SO4•─ and 1O2 were major contributors. The impact of coexisting inorganic anions revealed that the HCO3− ion exhibited the most pronounced inhibitory effect due to the production of less reactive CO3•─ radical. This study combined experimental and computational methods to enrich our understanding of the activation mechanisms, transformation pathways, toxicity of intermediates, and factors governing the N-BC-supported Bi-Fe/PMS system.

Double deposition/accumulation and double stripping steps system as a new way of decreasing the detection limit and elimination of interferences in stripping voltammetry of inorganic ions: A review

AbstractThe article reviews an application of double deposition/accumulation and stripping steps as a new and beneficial manner of decreasing a detection limit and/or interferences elimination in stripping voltammetric determination of inorganic ions: Pb(II), Cd(II), Tl(I), U(VI), Au(III), As(III), Se(IV), In(III), Co(II), Cu(II), Bi(III) and Ga(III). A simple design of four‐electrodes system, containing two working electrodes differing in their surface area, allows for conducting two preconcentration and two stripping steps in one measurement cycle and in one voltammetric cell. Considerable analytes preconcentration and, consequently, an increase of sensitivity of determinations was obtained by conducting the first stripping step in a small volume of a solution near the microelectrode surface. An appropriate selection of the conditions of the first deposition/accumulation and the first stripping steps allowed for a minimization/elimination of interference effects. The proposed procedures allows for ultra‐trace levels determinations of mentioned inorganic ions (often impossible to determine by means of traditional three‐electrodes systems) without additional preconcentration outside the electrochemical cell and with the use of mercury‐free electrodes.

Synthesis of metal anthranilate complexes: catalytic and antipathogenic studies

BackgroundAnthranilic acid is an active compound with diverse biological activities such as anti-inflammatory, antineoplastic, anti-malarial and α-glucosidase inhibitory properties. It can also chelate transition metals to form complexes with applications as antipathogens, photoluminescent materials, corrosion inhibitors, and catalysts.ResultsAnthranilic acid complexes (1–10) of Zn(II), Bi(III), Ag(I), Fe(II), Co(II), Cu(II), Mn(II), Al, Ni(II), and Cr(III) were synthesized and characterized using thermogravimetric (TGA), elemental analysis, FT-IR, UV–vis spectrometry, mass spectrometry and magnetic susceptibility. The morphology and size of metal complex (1–10) particles were determined by scanning electron microscope (SEM) and the surface area was determined by BET analysis. TGA and CHN analysis data indicated that the stoichiometries of complexes were 1:2 metal/ligand except for Ag(I), Al and Bi. Furthermore, DFT study was performed to optimize the structure of selected complexes. The complexes (1–10) were evaluated for their catalytic activity in the reduction of 4-nitrophenol (4-NP), antibacterial activity against S. aureus, P. aeroginosa and E. coli as well as their antifungal activity against F. solani and A. niger. The complexes were also tested against the second-stage juveniles (J2) root-knot nematodes.ConclusionCo(II) complex 5 and Cu(II) complex 6 showed high catalytic activity for the reduction of 4-NP to 4-aminophenol (4-AP). Ag(I) complex 3 showed the best activity against the pathogens that were tested namely clinically important bacteria S. aureus, P. aeroginosa and E. coli, commercially important fungi F. solani and A. niger and J2 root-knot nematodes M. javanica.

Bismuth Redox Catalysis: An Emerging Main-Group Platform for Organic Synthesis.

Bismuth has recently been shown to be able to maneuver between different oxidation states, enabling access to unique redox cycles that can be harnessed in the context of organic synthesis. Indeed, various catalytic Bi redox platforms have been discovered and revealed emerging opportunities in the field of main group redox catalysis. The goal of this perspective is to provide an overview of the synthetic methodologies that have been developed to date, which capitalize on the Bi redox cycling. Recent catalytic methods via low-valent Bi(II)/Bi(III), Bi(I)/Bi(III), and high-valent Bi(III)/Bi(V) redox couples are covered as well as their underlying mechanisms and key intermediates. In addition, we illustrate different design strategies stabilizing low-valent and high-valent bismuth species, and highlight the characteristic reactivity of bismuth complexes, compared to the lighter p-block and d-block elements. Although it is not redox catalysis in nature, we also discuss a recent example of non-Lewis acid, redox-neutral Bi(III) catalysis proceeding through catalytic organometallic steps. We close by discussing opportunities and future directions in this emerging field of catalysis. We hope that this Perspective will provide synthetic chemists with guiding principles for the future development of catalytic transformations employing bismuth.

The first utilization of graphene nano-sheets and synthesized Fe3O4 nanoparticles as a synergistic electrodeposition platform for simultaneous voltammetric determination of some toxic heavy metal ions in various real environmental water samples

An environmentally-friendly, inexpensive, and high-throughput method was developed for the simultaneous determination of three important heavy metal ions including Pb(II), Bi(III) and Cu(II). Those can cause synergistic toxicological effects in animals and humans. Magnetite (Fe3O4) nanoparticles were synthesized and characterized. A carbon paste electrode (CPE) modified with Fe3O4 NPs and graphene nanosheets (Fe3O4:Gr) was established. Its surface and electrochemical characterizations were described using scan electron spectroscopy (SEM), cyclic voltammetry and electrochemical impedance spectroscopy (EIS). The charge transfer resistance values were 154.83, 77.71, 60.00 and 3.39 KΩ for CPE, 5%(w/w) Gr/CPE, 2%(w/w) Fe3O4/CPE and [2%(w/w) Fe3O4:5%(w/w) Gr]/CPE revealing that the latter has greatly enhance electron transfer process. Following preconcentration by electrolytic deposition of such metal ions at [2%(w/w)Fe3O4:5%(w/w)Gr]/CPE at −0.7 V for 60 s in acetate buffer (pH 3.60), three distinguished anodic peaks were appeared at −0.55, 0.00 and 0.15 V due to oxidation of the deposited Pb, Bi and Cu, respectively. LOD values of 59, 44 and 55 ng L−1 for Pb(II), Bi(III) and Cu(II), respectively are much lower than the safety values set by World Health Organization in drinking water. This sensor displays good selectivity in presence of potentially interfering other metal ions, stability for 30 days with RSD of ≤ 5.25% and reproducibility of electrodes with R ± RSD% of (98.94 ± 1.28–99.67 ± 1.12), (98.04 ± 1.35–100.30 ± 1.15) and (98.16 ± 1.55–99.67 ± 1.18) for Pb(II), Bi(III) and Cu(II), respectively. It was also applied successfully in trace determination of such polluted metal ions in real samples such as Tap water, some bottled natural water samples, river and seawater samples.

Copper-Loaded Layered Bismuth Subcarbonate-Efficient Multifunctional Heterogeneous Catalyst for Concerted C-S/C-N Heterocyclization.

An efficient self-supported Cu(II)Bi(III) bimetallic catalyst with a layered structure was designed and developed. By careful characterization of the as-prepared material, the host structure was identified to exhibit a Sillen-type bismutite framework, with copper(II) ions being loaded as guests. The heterogeneous catalyst enabled C–N and C–S arylations under mild reaction conditions and with high chemoselectivities, thus furnishing valuable phenothiazines via heterocyclization with wide substrate tolerance. As corroborated by detailed catalytic studies, the cooperative, bifunctional catalyst, bearing Lewis acid sites along with copper(II) catalytic sites, facilitated an intriguing concerted C–N/C–S heterocyclization mechanism. The heterogeneous nature of the catalytic reactions was verified experimentally. Importantly, the catalyst was successfully recycled and reused multiple times, persevering its original structural order as well as its initial activity.

Reduced texaphyrin: A ratiometric optical sensor for heavy metals in aqueous solution.

We report here a water-soluble metal cation sensor system based on the as-prepared or reduced form of an expanded porphyrin, texaphyrin. Upon metal complexation, a change in the redox state of the ligand occurs that is accompanied by a color change from red to green. Although long employed for synthesis in organic media, we have now found that this complexation-driven redox behavior may be used to achieve the naked eye detectable colorimetric sensing of several number of less-common metal ions in aqueous media. Exposure to In(III), Hg(II), Cd(II), Mn(II), Bi(III), Co(II), and Pb(II) cations leads to a colorimetric response within 10 min. This process is selective for Hg(II) under conditions of competitive analysis. Furthermore, among the subset of response-producing cations, In(III) proved unique in giving rise to a ratiometric change in the ligand-based fluorescence features, including an overall increase in intensity. The cation selectivity observed in aqueous media stands in contrast to what is seen in organic solvents, where a wide range of texaphyrin metal complexes may be prepared. The formation of metal cation complexes under the present aqueous conditions was confirmed by reversed phase high-performance liquid chromatography, ultra-violet-visible absorption and fluorescence spectroscopies, and high-resolution mass spectrometry.

Sorption Properties of a Magnetic Composite Based on Modified Carbon Nanotubes: Influence of the Synthesis Conditions

The performance of a magnetic composite sorbent consisting of magnetic nanoparticles and carbon nanotubes (CNTs) in sorption of toxic metal ions [Be(II), Bi(III), Cd(II), Cr(III)] was studied in relation to the conditions of preparing the composite and its constituents. The pH dependence of the sorption of the metal ions was studied, and the sorption capacity of the composites containing CNTs of different morphology was determined. Be(II) and Cr(III) are taken up from aqueous solutions at pH 6, and Cd(II) and Bi(III), at pH 4.0–5.0. The composite containing CNTs prepared by catalytic pyrolysis of ethanol vapor on the Ni catalyst, CNT(Ni), exhibits the highest, and the sorbent containing CNTs synthesized on the Fe catalyst, CNT(Fe), the lowest sorption capacity. The sorption capacity of the composite containing CNTs prepared on the Co catalyst, CNT(Co), is intermediate. The dependence of the sorption ability of the composite on the ratio of its constituents was studied. The minimal content of magnetic nanoparticles ensuring the magnetism required for the efficient phase separation is 10% relative to the total sorbent weight. At this composition, the sorption capacity of the composite for Be(II), Bi(III), Cd(II), and Cr(III) is the highest: 8.0, 7.0, 6.2, and 6.7 mg g−1, respectively. Despite lower sorption capacity of magnetic sorbents based on CNT(Fe) and CNT(Co), they can also be successfully used for removing toxic elements from aqueous media by static magnetic solid-phase extraction both in sample preparation for analysis and in treatment of various water reservoirs.

Highly Selective Solid‐Phase Extraction of Pb(II) by Ion‐Imprinted Superparamagnetic Mesoporous Silica

AbstractPb (II)‐imprinted superparamagnetic mesoporous silica (SPMS) adsorbent has been synthesized and characterized. The thiol functionalized SPMS offered a fast adsorption kinetics for Pb(II) and equilibrium was achieved in just 20 min at pH 8.0. The adsorption isotherm data fits well with Langmuir model with a maximum adsorption capacity of 377.36 mg g−1. The selectivity co‐efficients of imprinted adsorbent for Pb(II)/Cu(II) and Pb(II)/Bi(III) were 3.36 and 3.05 times higher than that of non‐imprinted adsorbent. The imprinted adsorbent was employed for the solid phase extraction of Pb(II) and its detection by graphite furnace atomic absorption spectrometry (GFAAS).The parameters affecting the determination of Pb(II) were also well investigated and optimized. A linear relationship between the Pb(II) concentration and the absorbance was found in the range of 0.8‐500 ng mL−1 with a detection limit of 0.25 ng mL−1. The imprinted adsorbent was applied to the determination of Pb(II) in two certified sediment samples with satisfactory results, which indicates that Pb(II)‐imprinted superparamagnetic mesoporous silica adsorbent possess promising features of a viable adsorbent for the preconcentration of Pb(II) ions in complex matrices.

An in situ approach for the synthesis of a gum ghatti-g-interpenetrating terpolymer network hydrogel for the high-performance adsorption mechanism evaluation of Cd(ii), Pb(ii), Bi(iii) and Sb(iii)

Unorthodox synthesis of natural polymer-g-terpolymer superadsorbent for exclusion of M(ii/iii).

Ferrocenyl chalcone-based Schiff bases and their metal complexes: Highly efficient, solvent-free synthesis, characterization, biological research

This study highlights the synthesis and characterization of Schiff base ligands namely 1-ferrocenyl-3- (2-furyl) propenone diamino (thio) urea and selected metal complexes including Pb(Ⅱ), Bi(Ⅲ), Cu(Ⅱ), Cr(Ⅲ), Ba(Ⅱ), Cd (Ⅱ), Fe(Ⅱ), Ni(Ⅱ), Sn(Ⅱ), Nd(Ⅱ) as a central metal. The stoichiometric ratios of the prepared complexes were estimated using complementary techniques such as elemental analyses (C,H,N), FT-IR and molar conductivity. Furthermore, their physicochemical studies were carried out using thermal TGA. Antimicrobial activities of both the Schiff base ligand and its metal complexes were tested against strains of Gram (-ve), such as E. coli and S. aureus and MRSA, C. albicans and A. flavus fungi. The investigated Schiff base complexes showed higher activity and stability than their corresponding Schiff base ligands and the addition of ferrocene group also achieved the function of drug superposition. Moreover, the prepared Schiff base ligand and its Cu(II) and Cd(II)and Ni(II) complexes have been evaluated for their anticancer activities against two cancer cell lines namely mouse leukemia cells (P-388) and lung cancer (A-549) cell lines.

Determination of copper in urine by diffuse reflectance spectroscopy

A possibility of determining copper(II) after adsorption on polyacrylonitrile fiber filled with a KU-2 cation exchanger with immobilized 1-(2-pyridylazo)-2-naphthol (PANF–KU-2–PAN) is studied. The diffuse reflectance spectra of the carrier discs before and after the adsorption of copper in the batch mode are recorded. The dependences of the analytical signals of the copper complex on PANF–KU-2–PAN on adsorption conditions are studied. The conditions for determining 0.05–0.40 μg/mL of copper(II) by measuring diffuse reflection coefficient at 640 nm or visually by a color scale after the adsorption of copper from 20 mL of a solution containing 0.01 M of HCl are found. The determination of 0.1 μg/mL of copper does not interfered with equal amounts of Co, Zn, and Pb and double amounts of Ag, Fe(III), Cd, Mn(II), Bi(III), and Cr(III). The procedure is used for urine analysis. The following conditions of the preparation of urine samples for the determination of copper were selected: boiling with hydrogen peroxide followed by acidification to pH 2. A procedure for determining copper in urine with a limit of detection of 0.03 μg/mL was developed; the relative standard deviation does not exceed 25%; the duration of analysis of 5–6 samples is 30–35 min.

Lead(II) Binding in Metallothioneins.

Heavy metal exposure has long been associated with metallothionein (MT) regulation and its functions. MT is a ubiquitous, cysteine-rich protein that is involved in homeostatic metal response for the essential metals zinc and copper, as well as detoxification of heavy metals; the most commonly proposed being cadmium. MT binds in vivo to a number of metals in addition to zinc, cadmium and copper, such as bismuth. In vitro, metallation with a wide range of metals (especially mercury, arsenic, and lead) has been reported using a variety of analytical methods. To fully understand MT and its role with lead metabolism, we will describe how MT interacts with a wide variety of metals that bind in vitro. In general, affinity to the metal-binding cysteine residues of MT follows that of metal binding to thiols: Zn(II) < Pb(II) < Cd (II) < Cu(I) < Ag(I) < Hg(II) < Bi(III). To introduce the metal binding properties that we feel directly relate to the metallation of metallothionein by Pb(II), we will explore MT's interactions with metals long known as toxic, particularly, Cd(II), Hg(II), and As(III), along with xenobiotic metals, and how these metal-binding studies complement those of lead binding. Lead's effects on an organism's physiological functions are not fully understood, but it is known that chronic exposure inflicts amongst other factors pernicious anemia and developmental issues in the brain, especially in children who are more vulnerable to its toxic effects. Understanding the interaction of lead with metallothioneins throughout the biosphere, from bacteria, to algae, to fish, to humans, is important in determining pathways for lead to enter and damage physiologically significant protein function, and thereby its toxicity.

Development of liquid-liquid extraction and separation method for ruthenium(III) with 2-octylaminopyridine from succinate media: Analysis of catalysts

Ruthenium(III) has been efficiently extracted from 0.05 M sodium succinate at pH 9.5 by 2-octylaminopyridine in xylene and stripped with aqueous 10% (w/v) thiourea solution and determined spectrophotometrically. Various parameters viz., pH, weak acid concentration, reagent concentration, stripping agents, contact time, loading capacity, aq.: org. volume ratio, solvent has been thoroughly investigated for quantitative extraction of ruthenium(III). The utility of method was analyzed by separating the ruthenium(III) from binary mixture along with the base metals like Cu(II), Ag(I), Fe(II), Co(II), Bi(III), Zn(II), Ni(II), Se(IV), Te(IV), Al(III) and Hg(II) as well as platinum group metals (PGMs). Ruthenium(III) was also separated from ternary mixtures like Os(VIII), Pd(II); Pd(II), Pt(IV); Pd(II), Au(III); Pd(II), Cu(II); Fe(II), Cu(II); Ni(II), Cu(II); Co(II), Ni(II); Se(IV), Te(IV); Rh(III), Pd(II); Fe(III), Os(VIII). The stoichiometry 1: 2: 1 (metal: succinate: extractant) of the proposed complex was determined by slope analysis method by plotting graph of logD[Ru(III)] versus logC[2-OAP] and logD[Ru(III)] versus logC[succinate]. The interference of various cations and anions has been studied in detail and the statistical evaluations of the experimental results are reported. The method was successfully applied for the analysis of ruthenium in various catalysts, synthetic mixtures corresponding to the composition of alloys and minerals.

Quasi-epitaxial Metal-Halide Perovskite Ligand Shells on PbS Nanocrystals.

Epitaxial growth techniques enable nearly defect free heterostructures with coherent interfaces, which are of utmost importance for high performance electronic devices. While high-vacuum technology-based growth techniques are state-of-the art, here we pursue a purely solution processed approach to obtain nanocrystals with eptaxially coherent and quasi-lattice matched inorganic ligand shells. Octahedral metal-halide clusters, respectively 0-dimensional perovskites, were employed as ligands to match the coordination geometry of the PbS cubic rock-salt lattice. Different clusters (CH3NH3+)(6-x)[M(x+)Hal6](6-x)- (Mx+ = Pb(II), Bi(III), Mn(II), In(III), Hal = Cl, I) were attached to the nanocrystal surfaces via a scalable phase transfer procedure. The ligand attachment and coherence of the formed PbS/ligand core/shell interface was confirmed by combining the results from transmission electron microscopy, small-angle X-ray scattering, nuclear magnetic resonance spectroscopy and powder X-ray diffraction. The lattice mismatch between ligand shell and nanocrystal core plays a key role in performance. In photoconducting devices the best performance (detectivity of 2 × 1011 cm Hz 1/2/W with > 110 kHz bandwidth) was obtained with (CH3NH3)3BiI6 ligands, providing the smallest relative lattice mismatch of ca. -1%. PbS nanocrystals with such ligands exhibited in millimeter sized bulk samples in the form of pressed pellets a relatively high carrier mobility for nanocrystal solids of ∼1.3 cm2/(V s), a carrier lifetime of ∼70 μs, and a low residual carrier concentration of 2.6 × 1013 cm-3. Thus, by selection of ligands with appropriate geometry and bond lengths optimized quasi-epitaxial ligand shells were formed on nanocrystals, which are beneficial for applications in optoelectronics.

Simultaneous determination of seven metal ions in water samples by solid-phase extraction on polyacrylonitrile activated carbon fibres

A new solid-phase extraction method utilising polyacrylonitrile activated carbon fibres (PAN-ACFs) as adsorbent was developed for the preconcentration of trace metal ions prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The PAN-ACFs oxidised with nitric acid were characterised by FT-IR, XRD, SEM and BET analysis. Then the resulting PAN-ACFs were used as solid-phase adsorbent for simultaneously determination of trace Al(III), Be(II), Bi(III), Cr(III), Cu(II), Fe(III) and Pb(II) ions in aqueous solutions. The influences of the analytical parameters on the recoveries of the studied ions were investigated. The optimum experimental conditions of the proposed method were pH: 6.0; eluent concentration and volume: 3.0 mL of 1.5 mol L−1 nitric acid; flow rates of sample and eluent solution: 1.5 mL min−1. The preconcentration factors were found to be 67 for Al(III), Bi(III); 83 for Cr(III), Cu(II), Fe(III) and 50 for Be(II), Pb(II). The precision of this method was in range of 1.5%~3.5% and the detection limit of this metal ions was between 0.06~1.50 μg L−1. The developed method was validated by the analysis of a certified reference sample and successfully applied to the determination of trace metal ions in water samples with satisfactory results.

Organic Solvent-Free Cloud Point Extraction-like Methodology Using Aggregation of Graphene Oxide

Because of its unique properties and capability of formation of well-dispersed aqueous colloids in aqueous phase, graphene oxide can be used for the efficient preconcentration of heavy metal ions prior to their determination. The complete collection of graphene oxide colloids from water has generally been considered to be insurmountable. Here, graphene oxide aggregation triggered by introducing NaCl was used to develop a novel organic solvent-free cloud point extraction-like method for the determination of trace toxic metals. The graphene oxide sheets were uniformly dispersed in aqueous samples or standard solutions for a fast and efficient adsorption of Pb(II), Cd(II), Bi(III), and Sb(III) owing to its hydrophilic character and the electrostatic repulsion among the graphene oxide sheets, and its aggregation immediately occurred when the electrostatic repulsion was eliminated via adding NaCl to neutralize the excessive negative charges on the surface of graphene oxide sheets. The aggregates of graphene oxide and analytes ions were separated and treated with hydrochloric acid to form a slurry solution. The slurry solution was pumped to mix with KBH4 solution to generate hydrides, which were subsequently separated from the liquid phase and directed to an atomic fluorescence spectrometer or directly introduced to an inductively coupled plasma optical emission spectrometer for detection. On the basis of a 50 mL sample volume, the limits of detection of 0.01, 0.002, 0.01, and 0.006 ng mL(-1) were obtained for Pb, Cd, Bi, and Sb, respectively, when using atomic fluorescence spectrometry, providing 35-, 8-, 36-, and 37-fold improvements over the conventional method. Detection limits of 0.6, 0.15, 0.1, and 1.0 ng mL(-1) were obtained with the use of slurry sampling inductively coupled plasma optical emission spectrometry. The method was applied for analysis of two Certified Reference Materials and three water samples for these elements.