Reductive immobilization and long-term remobilization of radioactive pertechnetate using bio-macromolecules stabilized zero valent iron nanoparticles

Reductive immobilization of radioactive pertechnetate (⁹⁹TcO₄^?) in simulated groundwater was studied by prepared carboxymethyl cellulose (CMC) and starch stabilized zero valent iron nanoparticles (nZVI), and long-term remobilization of reduced Tc was also evaluated under anoxic and oxic conditions. The stabilized nZVI can effectively reduce soluble ⁹⁹Tc(VII) to insoluble ⁹⁹Tc(IV), and they can be easily delivered into a contaminated groundwater zone and facilitate in situ remediation. In this study, CMC-stabilized nZVI showed higher reactivity than that using starch as the stabilizer. Batch experiments indicated that more than 99% of ⁹⁹Tc(VII) (C₀ = 12 mg/mL) was reduced and removed from groundwater by CMC-stabilized nZVI with a CMC content of 0.2% (w/w) at a broad pH of 5–8. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses further confirmed that ⁹⁹Tc(VII)O₄^? transformed into ⁹⁹Tc(IV)O₂ (s). The presence of bicarbonate exhibited insignificant effect on Tc immobilization, while humic acid (HA) inhibited reaction mainly due to retardation on electron transfer and formation of Tc(IV)-HA complexes. More interesting, the immobilized Tc(IV) remained insoluble even after 120 d under anoxic condition, while only ～21% was remobilized when exposed to air. Therefore, bio-macromolecules stabilized nZVI nanoparticles could be a viable alternative for in situ remediation of radioactive contamination in groundwater.     

Reductive immobilization and long-term remobilization of radioactive pertechnetate using bio-macromolecules stabilized zero valent iron nanoparticles

Carboxymethyl cellulose-and starch-stabilized nZVI nanoparticles were prepared and showed high efficiency for reductive immobilization of ⁹⁹TcO₄^- in simulated groundwater.     

Mechanism and influence factors of 2,4-D dechlorination by sodium citrate-activated bimetallic palladium-zero valent iron nanoparticles

Nanoscale zero-valent iron (nZVI) has high removal efficiency and strong reductive ability to organic contaminants, but this reactivity soon ceases and is attributed to rapid passivation of the nZVI surface due to the formation of iron oxides. In the present study, bimetallic palladium-zero valent iron nanoparticles were activated with sodium citrate (SC-nPd/Fe) to enhance 2,4-D dechlorination from aqueous solutions. FTIR and XRD analyses showed that there was no passivation layer on the surface of nZVI after the addition of SC, and XPS analysis confirmed the nZVI after the reaction still maintained high reactivity and surface Pd ratio. The existence of SC facilitated the transfer of electrons from Fe⁰ to contaminants, thus accelerating the reductive dechlorination of 2,4-D. The dechlorination efficiency of 2,4-D on nPd/Fe was only 56.4% in 210 min, while complete dechlorination could be achieved on SC-nPd/Fe under the same conditions, and simultaneously 97.1% of phenoxyacetic acid (PA) was generated. Moreover, the effect of reaction conditions on the dechlorination such as Pd ratio, SC dosage, initial pH and temperature was also investigated, and it was well described by pseudo-first-order kinetic model. In particular, The chelating abilities of SC is similar to EDTA, but it is an environmentally-friendly chelating agent. Findings from the present study suggested that the SC could be a promising substitute for application in the remediation of 2,4-D contained water.     

Characterization of iron hydroxide/oxide nanoparticles prepared in microemulsions stabilized with cationic/non-ionic surfactant mixtures

Iron oxide-hydroxide (α-Fe(2)O(3); Fe(OH)(3)) nanoparticles have been prepared by a microemulsion route using ammonia (NH(3)) solution or tetrabutylammonium hydroxide (TBAH) as precipitants. The iron oxide-hydroxide nanoparticles obtained were characterized by TGA, N(2) sorptiometry, XRD, IR, SEM, HR-TEM, and DLS techniques. Properties such as specific surface area (S(BET)), pore sizes and shapes, average particle size and distribution, crystallite structure, and thermal stability were determined. The properties of nanoparticles prepared using NH(3) and TBAH were compared after drying at 100°C and after being calcined in the temperature range 250-1100°C. It was found that the suspensions prepared using TBAH suffered immediate separation while those prepared using NH(3) resulted in very stable suspensions. Also, it was found that TBAH did not offer any advantage over NH(3) either in terms of specific surface area or in particle size of the prepared nanoparticles. Hence, the later part of the study was concentrated on the NH(3)-precipitated nanoparticles with particular emphasis on finding the most favorable, W (water-to-surfactant ratio) and/or surfactant concentration, S, to obtain the best conditions in terms of higher surface areas and narrower particle size distribution. It was found that the prepared suspension consisted of monodisperse nanoparticles (standard deviations <10%) and after separation and drying, high surface area powders were obtained. The highest surface area (315 m(2) g(-1)) was obtained when the smallest W (=20) and highest S (=0.20 mol L(-1)) were employed.     

Preparation of sterically stabilized gold nanoparticles for plasmonic applications

Plasmonic nanoparticles such as those of gold or silver have been recently investigated as a possible way to improve light absorption in thin film solar cells. Here, a simple method for the preparation of spherical plasmonic gold nanoparticles in the form of a colloidal solution is presented. The nanoparticle diameter is controlled in the range from several nm to tens of nm depending on the synthesis parameters with the size dispersion down to 14 %. The synthesis is based on thermal decomposition and reduction of the chloroauric acid in the presence of a stabilizing capping agent (surfactant) that is very slowly injected into the hot solvent. The surfactant prevents uncontrolled nanoparticle aggregation during the growth process. The nanoparticle size and shape depend on the type of the stabilizing agent. Surfactants with different lengths of the hydrocarbon chains such as Z-octa-9-decenylamine (oleylamine) with AgNO₃ and polyvinylpyrrolidone with AgNO₃ were used for the steric stabilization. Hydrodynamic diameter of the gold nanoparticles in the colloidal solution was determined by dynamic light scattering while the size of the nanoparticle metallic core was found by small-angle X-ray scattering. The UV-VIS-NIR spectrophotometer measurements revealed a plasmon resonance absorption in the 500–600 nm range. Self-assembled nanoparticle arrays on a silicon substrate were prepared by drop casting followed by spontaneous evaporation of the solvent and by a modified Langmuir-Blodgett deposition. The degree of perfection of the self-assembled arrays was analyzed by scanning electron microscopy and grazing-incidence small-angle X-ray scattering. Homogeneous close-packed hexagonal ordering of the nanoparticles stretching over large areas was evidenced. These results document the viability of the proposed nanoparticle synthesis for the preparation of high-quality plasmonic templates for thin film solar cells with enhanced power conversion efficiency, surface enhanced Raman scattering, and other applications.     

Catalytic conversions of chloroolefins over iron oxide nanoparticles 2. Isomerization of dichlorobutenes over iron oxide nanoparticles stabilized on the surface of ultradispersed poly(tetrafluoroethylene)

Nanosized iron oxides stabilized on the surface of ultradispersed poly(tetrafluoroethylene) (UPTFE) granules were synthesized by the thermal destruction of iron formate in boiling bed of UPTFE on the surface of heated mineral oil. The particle size of nanoparticles (∼6 nm) containing 5, 10, and 16 wt.% Fe depends weakly on the temperature of synthesis and iron to polymer ratio. The metal state is determined by the synthesis conditions. The nanoparticles synthesized at 280 °C consist mainly of the Fe₃O₄ and Fe₂O₃ phases. The samples obtained at 320 °C also contain iron(II) oxide. The catalytic properties of the obtained samples were tested in dichlorobutene isomerization. Unlike isomerization on the iron oxide nanoparticles supported on silica gel, reaction over the UPTFE supports proceeds without an induction period. The sample with 10 wt.% Fe containing magnetically ordered γ-Fe₂O₃ nanoparticles possesses the highest catalytic activity. Fast electron exchange between the iron ions in different oxidation states and high defectiveness of the nanoparticles contribute, most likely, to the catalytic activity. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1383–1390, June, 2005.     

Recycling nanoparticles stabilized in water-in-CO2 microemulsions for catalytic hydrogenations

Catalytic hydrogenations of olefins took place effectively in supercritical CO2 with Pd0 nanoparticles dispersed in the fluid phase using a water-in-CO2 microemulsion consisting of water, sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as a surfactant, and 1-octanol as a cosolvent. The hydrogenated products dissolved in supercritical CO2 can be separated from the octanol solution containing AOT microemulsions with Pd0 nanoparticles by phase separation (upper phase, supercritical CO2 with hydrogenated products; lower phase, 1-octanol containing AOT microemulsions with Pd0 nanoparticles) accompanied by reduction of CO2 pressure. After collecting the hydrogenated products by flowing the upper CO2 phase to a collection vessel, the Pd0 nanoparticles remaining in the lower phase can be redispersed into supercritical CO2 by pressurizing the system to a pressure where a homogeneous phase is attained. The redispersed nanoparticles can be reused as catalysts for the next runs of the hydrogenations. Triphenylethylene was hydrogenated to 1,1,2-triphenylethane at conversions of 100% (1st-3rd runs), >99% (4th run), and >96% (5th run) using the recycled Pd0 nanoparticles. The feasibility of using other organic solvents as cosolvents is also studied in the present paper.     

Functionalized carbon dots as sensors for gold nanoparticles in spiked samples: Formation of nanohybrids

This paper reports the synthesis, passivation and functionalization of luminescent carbon dots (CDs) possessing surface thiol ending groups. A simple procedure involving amidation of passivated carbon dots (p-CDs) with cysteamine boosts their photoluminescent properties and enables their use as easily controlled fluorescent nanosensors for determining citrate–gold nanoparticles (AuNPs). The mechanism behind the quenching phenomenon was established from fluorescence measurements at high temperatures and lifetime tests, and found to involve static quenching leading to the formation of CD–AuNP nanohybrids. A method for determining AuNPs in complex matrices was developed and validated by application to spiked drinking water and mussel tissues. The limits of detection and quantitation for AuNPs thus obtained were 0.20 and 0.66 nmol L^–1, respectively.     

Sulfur nanoparticles stabilized in the presence of water-soluble polymers

1. Download high-res image (188KB)
2. Download full-size image

     

Polyion complex stabilized palladium nanoparticles for Suzuki and Heck reaction in water

Palladium nanoparticles stabilized by a polyion complex composed of poly{4-chloromethylstyrene-co-(4-vinylbenzyl) tributylammonium chloride} and poly(acrylic acid) were easily recovered by filtration after pH treatment. The polyion complex stabilized palladium nanoparticles have high catalytic activity for the Suzuki and Heck reactions in water.     

A novel route for immobilization of oligonucleotides onto modified silica nanoparticles

A novel approach for immobilization of probe oligonucleotides that uses zirconium phosphate modified silica nanoparticles is proposed. The surface modification of nanoparticles was carried out in two stages. Initially binding of Zr4+ to the surface of silica nanoparticles and later treated with phosphoric acid for terminal phosphate groups. Oligonucleotide probes modified with amine group at 5'-end were strongly binds to the phosphate terminated silica nanoparticles with imidazole in presence of 0.1 mol L(-1) EDC [N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide], as phosphate groups are more reactive towards amine group. Various studies, i.e., synthesis of silica nanoparticles, their surface modification, probe immobilization, measurement of hybridization and effect of bovine serum albumin (BSA) were carried out during optimization of reaction conditions. The significant reduction in the background signal was observed by treating the probe modified silica nanoparticles with bovine serum albumin prior to hybridization. The probe modified silica nanoparticles were retained their properties and the hybridization was induced by exposure of single-stranded DNA (ssDNA) containing silica nanoparticles to the complementary DNA in solution. The decrease in the fluorescence signal for one mismatch and three mismatch was observed upon hybridization of probe with target DNAs, while there was no response for the random target ssDNA under the same experimental conditions. The intensity of fluorescence signal was linear to the concentration of target DNA ranging from 3.9 x 10(-9) to 3.0 x 10(-6)mol L(-1). A detection limit of 1.22 x 10(-9) mol L(-1) of oligonucleotides can be estimated. The proposed hybridization assay is simple and possesses good analytical characteristics and it can provide an effective and efficient route in the development of DNA biosensors and biochips.     

Simulation of block copolymer stabilized nanoparticles in a two-solvent system

In this paper, by using Brownian Dynamics simulation, we investigate in general terms the behavior of a nanoparticle stabilized by a block copolymer in the presence of an oil-water interface. We investigate the probability of sticking to the interface, the density distribution of the copolymer across the interface and the area occupied by the stabilized nanoparticle at the interface. By using representative snapshots of the stabilized nanoparticle, derived from the density distribution, we find that the nanoparticle stabilized by a block copolymer, with the hydrophobic side of it tethered to the nanoparticle, prefers sitting at the oil-phase, and thus has a contact angle that is tested to be larger than 90 degrees for most of the cases, even if the hydrophobe content is less than 50%. Thus we find the architecture of a block-copolymer attachment to have a significant effect on the emulsion type that would result.     

Functionalization of thioctic acid-capped gold nanoparticles for specific immobilization of histidine-tagged proteins

This paper presents an efficient strategy for the specific immobilization of fully functional proteins onto the surface of nanoparticles. Thioctic acid-derivatized gold clusters are used as a scaffold for further stepwise modification, leading to a cobalt(II)-terminated ligand shell. A histidine tag introduced by genetic engineering into a protein is coordinated to this transition metal ion. The specific immobilization has been demonstrated for the cases of a genetically engineered horseradish peroxidase and ferredoxin-NADP(+) reductase, confirming the attachment of the fully functional proteins to the Co(II)-terminated nanointerface. The absence of nonspecific protein adsorption and the specificity of the binding site have been verified using several analogues of the enzymes without the histidine tag.     

Core-shell microgel stabilized silver nanoparticles for catalytic reduction of aryl nitro compounds

Silver nanoparticles loaded into shell of poly (styrene-N-isopropylmethacrylamide-co-acrylic acid) core shell [P (SNA-CS)] gel particles were synthesized and analyzed by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), ultraviolet–visible spectroscopy (UV–vis) and dynamic light scattering (DLS). Catalytic activity of Ag@P (SNA-CS) particles was investigated by reducing p-nitroaniline (p-NA) into p-aminoaniline (p-AA) in the presence of sodium borohydride (NaBH₄) reductant. Molecules of the substrate adsorbed on the surface of silver nanoparticles interact with borohydride ions (BH₄⁻) to form p-AA. Other nitroarenes like o-nitroaniline (o-NA), p-nitrophenol (p-NP) o-nitrophenol (o-NP), 2,4-dinitrophenol(2,4-DNP) were also reduced into their corresponding aryl amines using Ag@P (SNA-CS) composite microgels as catalyst. Reported catalyst efficiently reduced the nitro aromatic compounds individually as well as simultaneously at ambient temperature. Effect of different reaction conditions (catalyst dose, concentration of NaBH₄ and concentration of p-NA) on reaction completion time, value of apparent rate constant (k_app) and reduction efficiency of the catalyst for reduction of p-NA was also demonstrated. Ag@P (SNA-CS) catalyst was found to be able to retain activity up to four cycles.     

Supramolecular immobilization of redox enzymes on cyclodextrin-coated magnetic nanoparticles for biosensing applications

Mono-6-formyl-β-cyclodextrin moieties were attached to (3-aminopropyl)triethoxysilane-coated superparamagnetic Fe(3)O(4) nanoparticles by reductive alkylation with NaBH(3)CN. The oligosaccharide-capped core-shell nanoparticles were employed as support for the supramolecular immobilization of two different adamantane-modified enzymes, tyrosinase and xanthine oxidase, through host-guest interactions. The enzyme-modified nanomaterial was further used to magnetically modify carbon paste electrodes for constructing amperometric biosensors toward cathecol and xanthine. The tyrosinase and xanthine oxidase based biosensors showed excellent electroanalytical behaviours, with linear ranges of 100nM-12μM cathecol and 5.0-120μM xanthine, sensitivities of 12mA/M and 130mA/M, and low detection limits of 22nM and 2.0μM, respectively. The supramolecular nature of the immobilization approach was confirmed by electroanalytical methods.     

Sensitive adsorptive stripping voltammetric procedure of Imatinib determination in spiked urine samples using solid lead microelectrode

This article reports for the first time the application of solid lead microelectrode for organic compound determination. The proposed sensor was used for anticancer drug Imatinib quantification by adsorptive stripping voltammetry. Procedure of Imatinib determination was developed utilizing advantages ensured by solid lead microelectrode: reusability and durability for a long period of time and its ecological character as compared to film electrodes. The detection limit of Imatinib determination was calculated to be 1.9 × 10⁻¹⁰ mol L⁻¹. The analytical usability of the developed procedure was confirmed by acceptable recoveries of Imatinib determination in spiked urine samples.     

Size effects in carbidization of iron nanoparticles

The dynamics and kinetics of formation of iron carbides in Fe/SiO₂ catalysts during the hydrogenation of CO and in a topochemical reaction between Fe and CO was studied. The effective activation energy of carbide formation was found to increase as the size of iron particles decreased. Alternative hypotheses explaining the observed size effect are suggested.     

Microwave-assisted synthesis of ultra-small iron oxide nanoparticles for biomedicine

1. Download high-res image (138KB)
2. Download full-size image

     

Spectral and photochemical characteristics of CdSe nanoparticles stabilized in polymer-containing media

The optical characteristics of CdSe nanoparticles, produced in aqueous solutions and polymer films in the reaction of cadmium chloride and sodium selenosulfate, were studied. The main parameters that make it possible to vary the forbidden band width were identified. The absorption, photoluminescence, Raman, and nonstationary decolorization spectra of CdSe nanoparticles of various sizes were analyzed. It was demonstrated that under the conditions of pulsed irradiation the CdSe nanoparticles are capable of accumulating excess electrons and inducing redox transformations in components of the solution (oxygen, methylviologen, and sulfite ions). __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 3, pp. 150–155, May–June, 2006.     

Dispersion of thiol stabilized gold nanoparticles in lyotropic liquid crystalline systems

A new method of forming stable dispersions of alkanethiol and aromatic thiol stabilized gold nanoparticles in two different lyotropic liquid crystalline mediums, namely, a columnar hexagonal phase made up of a Triton X-100/water system and an inverse columnar hexagonal phase made up of pure AOT, are presented. The dispersions have been characterized using small-angle X-ray scattering (SAXS) and polarizing optical microscopy. Our studies show that the gold nanoparticles are distributed outside the columns formed by both the surfactants. Such dispersions can find applications in the study of nanoparticles as well as in the development of devices based on some unique properties of metal nanoparticles.