Lanthanide sorbent based on magnetite nanoparticles functionalized with organophosphorus extractants

In this work, an adsorbent was prepared based on the attachment of organophosphorus acid extractants, namely, D2EHPA, CYANEX 272, and CYANEX 301, to the surface of superparamagnetic magnetite (Fe₃O₄) nanoparticles. The synthesized nanoparticles were coated with oleic acid, first by a chemisorption mechanism and later by the respective extractant via physical adsorption. The obtained core–shell functionalized magnetite nanoparticle composites were characterized by dynamic light scattering, scanning electron microscopy, transmission electron microscopy, thermogravimetry, infrared absorption and vibrating sample magnetometry. All the prepared nanoparticles exhibited a high saturation magnetization capacity that varied between 72 and 46 emu g⁻¹ and decreased as the magnetite nanoparticle was coated with oleic acid and functionalized. The scope of this study also included adsorption tests for lanthanum, cerium, praseodymium, and neodymium and the corresponding analysis of their results. Sorption tests indicated that the functionalized nanoparticles were able to extract the four studied lanthanide metal ions, although the best extraction performance was observed when the sorbent was functionalized with CYANEX 272, which resulted in a loading capacity of approximately 12–14 mg_La/g_MNP. The magnetization of the synthesized nanoparticles was verified during the separation of the lanthanide-loaded sorbent from the raffinate by using a conventional magnet.     

Kinetic sorption study of Cerium (IV) on magnetite nanoparticles

Magnetite nanoparticles (Fe₃O₄) and humic acid-coated magnetite nanoparticles (Fe₃O₄/HA) were prepared by co-precipitation method for cerium ions removal from aqueous solution. The success of preparation in nanoscale was confirmed by x-ray diffraction (XRD) and transmission electron microscopy (TEM). The TEM image shows that the size of Fe₃O₄ is around 15 nm and the presence of humic acid reduces the magnetite aggregation and stabilizes the magnetite suspension. Adsorption studies with respect to various process variables such as contact time, pH, and temperature were investigated by batch technique. The sorption kinetics and isotherms of Fe₃O₄ and Fe₃O₄/HA for Ce (IV) ions show that the sorption kinetics follow the pseudo-second-order and Langmuir isotherm models for both sorbents. The maximum capacities (Q_max) of Ce (IV) onto Fe₃O₄ and Fe₃O₄/HA were found to be 160 and 280 mg/g, respectively. The thermodynamic parameters (ΔG^o, ΔH^o and ΔS^o) were calculated, and the results revealed that the sorption process of Ce (IV) ions on both Fe₃O₄ and Fe₃O₄/HA are spontaneous, endothermic for Fe₃O₄ and exothermic for Fe₃O₄/HA.     

Simultaneous synthesis of polyaniline nanorods and magnetite nanoparticles via self-assembly method

In this work, polyaniline (PANI) nanorods and magnetite (Fe₃O₄) nanoparticles have been synthesised by using ammonium persulphate as oxidant via in-situ chemical oxidative polymerisation of aniline in presence of excess of organic sulphonic acid. The resulting PANI/Fe₃O₄ nanocomposites materials were characterised using X-ray diffraction, UV-visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, vibrating sampling magnetometer and thermogravimetric analysis. Spectroscopic results indicated the successful formation of PANI/Fe₃O₄ nanocomposites. As obtained, PANI/Fe₃O₄ nanocomposites have Fe₃O₄ particle size in the range of 3.2–7?nm. Morphologies of PANI/Fe₃O₄ nanocomposites were found to be dependent on the molar ratio of aniline to organic acid. Under certain polymerisation conditions, PANI rods like structures were obtained. PANI/Fe₃O₄ nanocomposites have superparamagnetism and higher thermal stability.     

Polymer-grafted magnetite nanoparticles via a facile in situ solution radical polymerisation

Polymer-grafted magnetic nanoparticles were prepared via in situ solution radical polymerisation. The oleic acid modified magnetic nanoparticles were prepared by the coprecipitation of magnetic nanoparticles in the presence of oleic acid. Then they were used as comonomers in the polymerisation of styrene. The products were characterised with Fourier transform infrared spectroscopy, thermogravimetric analysis and transmission electron microscope. The effect of the OA-MNPs added on the conversion of styrene (C%), the percentage of grafting (PG%) and the magnetic properties of the polystyrene/magnetic nanoparticles composites (PS/MNPs) were also investigated.     

A cholesterol biosensor based on gold nanoparticles decorated functionalized graphene nanoplatelets

The fabrication of a cholesterol biosensor using gold nanoparticles decorated graphene nanoplatelets has been reported. Thermally exfoliated graphene nanoplatelets act as a suitable support for the deposition of Au nanoparticles. Cholesterol biosensor electrodes have been constructed with nafion solubilized functionalized graphene nanoplatelets (f-G) as well as Au nanoparticles decorated f-G, immobilized over glassy carbon electrode. f-G and Au/f-G thin film deposited glassy carbon electrodes were further functionalized with cholesterol oxidase by physical adsorption. Au nanoparticles dispersed over f-G demonstrate the ability to substantially raise the response current. The fabricated electrodes have been tested for their electrochemical performance at a potential of 0.2 V. The fabricated Au/f-G based cholesterol biosensor exhibits sensitivity of 314 nA/μM cm² for the detection of cholesterol with a linear response up to 135 μM. Furthermore, it has been observed that the biosensor exhibits a good anti-interference ability and favorable stability over a month's period.     

Photoelectrochemical,optical and magnetic properties of magnetite nanoparticles

Magnetite magnetic nanoparticles are prepared using olive leaf extract as a green reducing and stabilizing agents. After reaction the product is heated up to get rid of the organic compounds and get pure magnetite nanoparticles. Differential scanning calorimetry is used to study the phase transformation as a function of heating temperature. Scanning electron microscope and high resolution transmission electron microscope show spherical and crystallized nanoparticles with a size of 5 nm. X-ray diffraction and Raman and x-ray photoelectron spectroscopy indicate the formation of Magnetite phase with high cristallinity and purity. The synthesized Magnetite nanoparticles are semiconductors with gap energy around 2 eV. Observed by transmission electron microscope graphite rods with stacked carbon disks are decorated with the prepared nanoparticles and show enhanced photocurrent. The vibrating sample magnetometer measurements indicate that the prepared Magnetite nanoparticles have superparamagnetic behavior. These results are very promising for clinical and water splitting applications.     

Fabrication of photoactive heterostructures based on quantum dots decorated with Au nanoparticles

Silica based multifunctional heterostructures, exhibiting near infrared (NIR) absorption (650–1200 nm) and luminescence in the visible region, represent innovative nanosystems useful for diagnostic or theranostic applications. Herein, colloidal synthetic procedures are applied to design a photoactive multifunctional nanosystem. Luminescent silica (SiO₂) coated quantum dots (QDs) have been used as versatile nanoplatforms to assemble on their surface gold (Au) seeds, further grown into Au spackled structures. The synthesized nanostructures combine the QD emission in the visible region, and, concomitantly, the distinctive NIR absorption of Au nanodomains. The possibility of having multiple QDs in a single heterostructure, the SiO₂ shell thickness, and the extent of Au deposition onto SiO₂ surface have been carefully controlled. The work shows that a single QD entrapped in 16 nm thick SiO₂ shell, coated with Au speckles, represents the most suitable geometry to preserve the QD emission in the visible region and to generate NIR absorption from metal NPs. The resulting architectures present a biomedical potential as an effective optical multimodal probes and as promising therapeutic agents due to the Au NP mediated photothermal effect.     

Strong adsorption of chlorotetracycline on magnetite nanoparticles

In this work, environmentally friendly magnetite nanoparticles (Fe₃O₄ MNPs) were used to adsorb chlorotetracycline (CTC) from aqueous media. Fe₃O₄ MNPs exhibit ultrahigh adsorption ability to this widely used antibiotic. The adsorption behavior of CTC on Fe₃O₄ MNPs fitted the pseudo-second-order kinetics model, and the adsorption equilibrium was achieved within 10 h. The maximum Langmuir adsorption capacity of CTC on Fe₃O₄ (476 mg g⁻¹) was obtained at pH 6.5. Thermodynamic parameters calculated from the adsorption data at different temperature showed that the adsorption reaction was endothermic and spontaneous. Low concentration of NaCl and foreign divalent cations hardly affected the adsorption. Negative effect of coexisting humic acid (HA) on CTC adsorption was also observed when the concentration of HA was lower than 20 mg L⁻¹. But high concentration of HA (>20 mg L⁻¹) increased the CTC adsorption on Fe₃O₄ MNPs. The matrix effect of several environmental water samples on CTC adsorption was not evident. Fe₃O₄ MNPs were regenerated by treatment with H₂O₂ or calcination at 400 °C in N₂ atmosphere after separation from water solution by an external magnet. This research provided a high efficient and reusable adsorbent to remove CTC selectively from aqueous media.     

An efficient method for decoration of the multiwalled carbon nanotubes with nearly monodispersed magnetite nanoparticles

A one-pot method has been developed to prepare magnetite nanoparticles decorated carbon nanotubes (CNTs) by thermal decomposition of iron chloride on CNTs templates in diethylene glycol. The morphological and structural characterizations indicate that magnetite nanoparticles are coated on the surfaces of the CNTs to form CNT-based nanocomposites. The density of magnetite nanoparticles on CNTs could be easily tuned by adjusting the weight ratio of iron chloride to CNTs. Magnetic measurements showed that the nanocomposites are superparamagnetic at room temperature and the magnetic properties of the samples can also be tuned by adjusting preparing conditions. The nanocomposites can be readily dispersed in water to form a stable solution and can be manipulated using an external magnetic field. As-synthesized nanocomposites may have potential applications in target–drug delivery, detection and separations, and in clinical diagnosis.     

镁铝铁层状金属氢氧化物固相萃取有机磷农药的研究

建立镁铝铁层状金属氢氧化物(Mg-Al-Fe-LDH)复合材料固相萃取气相色谱质谱法(GC-MS)测定水中的敌敌畏,乐果,氯吡硫磷,水胺硫磷的分析方法.复合材料用量为2 g,萃取12 min,二氯甲烷作为洗脱剂,洗脱剂用量为2 mL,洗脱时间1 min,4种农药的质量浓度在0.01～10 ng/mL范围内与峰面积线性关...     

Strategy of fabricating enriched gold nanoparticles based on electrochemical methods

In this work, we report a new and clean electrochemical pathway to prepare enriched gold nanoparticles in aqueous solutions via the aid of chitosan without addition of any other stabilizer and reductant. First, an Au substrate was cycled in a deoxygenated aqueous solution containing 0.1 N NaCl and 1 g/L chitosan from − 0.28 to + 1.22 V vs Ag/AgCl at 500 mV/s with 500 scans. Then the Au working electrode was immediately replaced by a Pt electrode, and a cathodic overpotential of 0.6 V from the open circuit potential (OCP) of ca. 0.84 V vs Ag/AgCl was applied under sonification to synthesize Au nanoparticles. Experimental results indicate the concentration and the particle sizes of prepared Au nanoparticles are ca. 50 ppm and 10 nm in diameter, respectively. No aggregation of Au nanoparticles is observed in an ambient atmosphere for at least 3 months.     

影响贵金属纳米颗粒表面等离子体共振因素评述

贵金属纳米颗粒具有可调的共振吸收谱,被广泛用于光能传送器、近场扫描光学显微学、表面增强谱学、化学和生物传感器等。系统地评述了颗粒尺寸、颗粒分布、颗粒形状、颗粒体积分数、颗粒组成和颗粒结构等因素对金属纳米颗粒等离子体共振吸收性能的影响,有利于深入理解等离子体共振吸收的物理实质和实现对等离子体共振频率的调控。     

Piezoelectric immunosensor based on gold nanoparticles capped with mixed self-assembled monolayer for detection of carcinoembryonic antigen

It is very important for a piezoelectric immunosensor to increase specific binding and decrease nonspecific adsorption. This study presents the development of such a piezoelectric immunosensor for the detection of carcinoembryonic antigen. An AT-cut quartz crystal's Au electrode surface was first modified with homogenous self-assembled monolayer of cysteamine (CE). Gold nanoparticles capped with mixed self-assembled monolayer of CE and MH (6-mercapto-1-haxanol) were then attached to the CE monolayer via glutaraldehyde (GA). Antibodies were immobilized onto a mixed self-assembled monolayer of CE and MH with GA as a reactive intermediate too. The binding of target antigens onto the immobilized antibodies decreased the sensor's resonant frequency, and the frequency shift was correlated to the antigen concentration. The stepwise assembly of the immunosensor was characterized by means of cyclic voltammetry technique. This immunoassay was shown to be specific and sensitive, thus providing a viable alternative to carcinoembryonic antigen detection method.     

A synthesis of fluorescent starch based on carbon nanoparticles for fingerprints detection

A pyrolysis method for synthesizing carbon nanoparticles (CNPs) were developed by using malic acid and ammonium oxalate as raw materials. The incorporation of a minor amount of carbon nanoparticles into starch powder imparts remarkable color-tunability. Based on this phenomenon, an environment friendly fluorescent starch powder for detecting latent fingerprints in non-porous surfaces was prepared. The fingerprints on different non-porous surfaces developed with this powder showed very good fluorescent images under ultraviolet excitation. The method using fluorescent starch powder as fluorescent marks is simple, rapid and green. Experimental results illustrated the effectiveness of proposed methods, enabling its practical applications in forensic sciences.     

Effect of ferrous/ferric ions molar ratio on reaction mechanism for hydrothermal synthesis of magnetite nanoparticles

Magnetite nanoparticles were prepared by hydrothermal synthesis under various initial ferrous/ferric molar ratios without adding any oxidizing and reducing agents in order to clarify effects of the molar ratio on the reaction mechanism for the formation of magnetite nanoparticles. The magnetite nanoparticles prepared were characterized by a scanning electron microscope, powder X-ray diffractometer, and superconducting quantum interference device (SQUID). At the molar ratio corresponding to the stoichiometric ratio in the synthesis reaction of magnetite from ferrous hydroxide and goethite, the nucleation of magnetite crystals progressed rapidly in an initial stage of the hydrothermal synthesis, resulting in formation of the magnetite nanoparticles having a smaller size and a lower crystallinity. On the other hand, at higher molar ratios, the particle size and crystallinity increased with increasing molar ratio because using surplus ferrous hydroxide the crystallites of magnetite nanoparticles grew up slowly under hydrothermal conditions according to the Schikorr reaction. The magnetite nanoparticles prepared under various molar ratios had good magnetic properties regardless of the molar ratio.     

Biomimetic fabrication of gold nanoparticles on templated indole-3-acetic acid based nanofibers

Self-assembly of the phytohormone indole-3-acetic acid (IAA) was examined in aqueous solutions of varying pH values. Further, it was observed that IAA biomimetically reduced Au ions leading to the formation of Au nanoparticles at a pH range of 4-9. It was found that at a pH range of 4-7, uniform spherical gold nanoparticles in the size ranges of 20-30 nm were obtained, while under basic conditions, a high degree of aggregation was observed. In addition, we conjugated IAA with the organic linker 1,4-diaminobutane in order to enhance the attachment of Au ions to the IAA moiety via the free amino group and examined its self-assembly. In general, higher yields of nanofibers were formed upon self-assembly of the amide conjugate, with lengths in the micron range. Further, it was observed that the Au nanoparticles formed in the presence of the self-assembled amide conjugates were uniformly coated, leading to the formation of uniform gold nanowires. Thus, a new class of materials based on IAA and IAA-amide conjugates could be efficiently used for formation of gold nanoparticles using environmentally friendly mild synthetic methods in the absence of harsh reducing agents. Such materials may have potential applications in optoelectronics, bioimaging and sensing.     

Impedimetric biosensor based on magnetic nanoparticles for electrochemical detection of dopamine

One of the difficulties which limit the use of electrochemical sensors for detection of dopamine is the interference from ascorbic acid. We have sought to address this problem through the synthesis and characterization of a suitable electrode material based on magnetic nanoparticles. The interference from the ascorbic acid was overcome by fabricating a negatively charged electrode surface using PEGylated arginine functionalized magnetic nanoparticles (PA-MNPs). The nanoparticles were characterized by various techniques viz., X-ray diffraction, FT-Infrared spectroscopy, transmission electron microscopy and vibrating sample magnetometer. The electrochemical behavior of the proposed sensor was investigated by cyclic voltammetry and the sensor showed high sensitivity and selectivity for dopamine. The response mechanism of the modified electrode is based on the interaction between the negatively charged electrode and the positively charged dopamine. Under optimized conditions, linear calibration plots were obtained for amperometric detection of dopamine (DA) over the concentration range of 1–9 mM dopamine, with a linear correlation coefficient of 0.9836, sensitivity of 121 μA/mM and a detection limit of 7.25 μM. Electrochemical impedance spectroscopy (EIS) has been used to study the interface properties of modified electrodes. The value of the polarization resistance (R_p) increases linearly with dopamine concentration in the range of 10 μM to 1 mM and the limit of detection (LOD) was calculated to be 14.1 μM. High sensitivity and selectivity, micromolar detection limit, high reproducibility, along with ease of preparation of the electrode surface make this system suitable for the determination of DA in pharmaceutical and clinical preparations.     

Synthesis and characterization of Ag/polyaniline core-shell nanocomposites based on silver nanoparticles colloid

Ag/polyaniline core-shell nanocomposites were successfully synthesized via in situ chemical oxidation polymerization of aniline based on mercaptocarboxylic acid capped Ag nanoparticles colloid. The morphology and structure of the products were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and UV-Vis spectra. A possible formation mechanism of the Ag/polyaniline core-shell nanocomposites was also proposed.