Silica-coated Magnetic Nanoparticles Research Articles

Enhanced Versatility in Thorium Removal: Mesoporous Silica-Coated Magnetic Nanoparticles Functionalized by Phenanthroline Diamide as a Selective Adsorbent.

In order to promote the sustainable development of nuclear energy through thorium (Th(IV)) recycling, we synthesized SiO2-coated magnetic functional nanocomposites (SiO2@Fe3O4) that were modified with 2,9-diamide-1,10-phenanthroline (DAPhen) to serve as an adsorbent for Th(IV) removal. SiO2@Fe3O4-DAPhen showed effective Th(IV) adsorption in both weakly and strongly acidic solutions. Owing to its porous structure that facilitated rapid adsorption kinetics, equilibrium was achieved within 5 and 0.5 min at pH 3 and 1 mol L-1 HNO3, respectively. In weakly acidic solutions, Th(IV) primarily formed chemical coordination bonds with DAPhen groups, while in strongly acidic solutions, the dominant interaction was electrostatic attraction. Density functional theory (DFT) calculations indicated that electrostatic attraction was weaker compared to chemical coordination, resulting in reduced diffusion resistance and consequently faster adsorption rates in strongly acidic solutions. Furthermore, SiO2@Fe3O4-DAPhen exhibited a high adsorption capacity for Th(IV); it removed Th(IV) through chelation and electrostatic attraction at pH 3 and 1 mol L-1 HNO3, with maximum adsorption capacities of 833.3 and 1465.7 mg g-1, respectively. SiO2@Fe3O4-DAPhen also demonstrated excellent tolerance to salinity, adsorption selectivity, and radiation resistance, thereby highlighting its practical potential for Th(IV) removal in diverse contaminated water sources. Hence, SiO2@Fe3O4-DAPhen represents a promising choice for the rapid and efficient removal of Th(IV).

Oxidation of C–H bond of benzylic position in aromatic substrates by dehydroacetic acid based on an Iron (III) complex covalently anchored on Fe3O4 nanoparticles

In this study, the authors synthesize a novel mononuclear catalyst consisting of an iron (III) complex based on a dehydroacetic acid (DHA) ligand that is covalently anchored to silica-coated magnetic nanoparticles, and characterize it by using XPS, XRD, FT-IR, TGA, VSM, SEM, TEM, EDX, and ICP analyses. This heterogeneously homogenized catalyst was used for the effective and selective catalytic oxidation of a diverse range of C–H bonds of the benzylic position of aromatic substrates in water at room temperature. To the best of our knowledge, this is the first report of the DHA anchored on a nanomagnet. The DHA ligand tuned the Lewis acidity of the center of the metal, and this led to a greater dispersion of the catalyst in the aqueous solution. The magnetic catalyst was easily recovered by using a permanent magnet and reused for at least six cycles without a significant reduction in the conversion. The leaching test of the catalyst was also investigated during this process, and the results illustrated that the oxidation of the C–H bond occurred via a heterogeneous pathway.

Magnetic nanoadsorbent functionalized with aminophosphonic acid for NdIII ion extraction from aqueous media

The adsorption performance of a new magnetic nanoadsorbent of Nd3+ was investigated. First, the nanoadsorbent was synthesized by chemical coprecipitation, and covered with a silica layer by the sol–gel method to obtain the silica-coated magnetic nanoparticles (MNP@SiO2). Subsequently, it was functionalized with nitrilotris(methylene)triphosphonic acid(NTMP), obtaining the goal aminophosphonic-functionalized nanoadsorbent (MNP@SiO2-NTMP). The functionalized nanoadsorbent was characterized using TEM, XRD, VSM, TGA, ATR-FTIR, EDS, and zeta potential measurements, confirming its nanoscale size, superparamagnetic behavior, and the presence of surface amino-phosphonic groups. The influence of different operational parameters on neodymium adsorption was investigated. The highest adsorption capacity of neodymium(III) was approximately 18 mg·g−1 at pH 6.8, using an adsorbent dose of 1 g·L-1, a neodymium concentration of 100 mg·L-1, and a contact time of 15 min at room temperature. The neodymium(III) adsorption onto MNP@SiO2-NTMP followed a pseudosecond-order model, suggesting chemisorption mechanisms as the rate-limiting step. Batch experimental results showed that Nd3+ adsorption onto MNP@SiO2-NTMP was independent of the ionic strength, indicating the formation of inner-sphere surface complexes.Furthermore, the adsorption thermodynamic analyses suggested that neodymium adsorption was exothermic, entropy decreasing, and more favorable at low temperatures. The best adsorbent regeneration and neodymium desorption from the loaded adsorbent was achieved using acidic solutions of H2SO4, exhibiting excellent adsorbent reusability throughout the four adsorption–desorption cycles. The MNP@SiO2-NTMP was an effective adsorbent material for extracting neodymium(III) from dilute aqueous solutions. Therefore, it is expected that MNP@SiO2-NTMP can potentially be used in more sustainable recovery methods of neodymium from secondary sources, for example, from leaching solutions of NdFeB magnet scraps.

Silica-magnetite nanoparticles: Synthesis, characterization and nucleic acid separation potential

Silica-coated magnetic nanoparticles can be utilized for the magnetic separation of nucleic acids, which is an important step in many clinical procedures. A series of silica-functionalized superparamagnetic iron oxide nanoparticles (SiO2@MNPs) was synthesized to efficiently separate nucleic acids for the sensitive detection of viral infections. Magnetite nanoparticles (MNPs) coated with different thicknesses of silica layer resulting from different ratios of tetraethylorthosilicate (TEOS) precursor to magnetite (TEOS/MNPs = 0.4, 1.0, 2.0, 3.0, 4.0, 5.0 ml/g) have been selected for characterization of their physico-chemical properties and biological activities. The SiO2@MNPs' morphology, size, magnetic and surface properties, cytotoxicity and nucleic acid binding propensity were determined to select the ones with the highest RNA separation potential. Our results showed that RNA-binding properties and magnetic separation efficiency are nanoparticle size-dependent. The highest binding and separation efficiencies were detected for the smaller SiO2@MNPs with TEOS/MNPs (v/w) ratios equal to 1.0 and 2.0. These nanoparticles are promising candidates for clinical application relevant to RNA viruses.

Cobalt-Doped Mesoporous Silica Coated Magnetic Nanoparticles Promoting Accelerated Bone Healing in Distraction Osteogenesis.

Large bone abnormalities are commonly treated using distraction osteogenesis (DO), but it is not suitable for a long-term application; therefore, there is an urgent need for adjuvant therapy that can accelerate bone repair. We have synthesized mesoporous silica-coated magnetic nanoparticles doped with cobalt ions (Co-MMSNs) and assessed their capacity to quicken bone regrowth in a mouse model of DO. Furthermore, local injection of the Co-MMSNs significantly accelerated bone healing in DO, as demonstrated by X-ray imaging, micro-CT, mechanical tests, histological evaluation, and immunochemical analysis. In vitro, the Co-MMSNs exhibited good biocompatibility and induced angiogenic gene expression and osteogenic development in bone mesenchymal stem cells. And the Co-MMSNs can promote bone regeneration in a rat DO model. This study demonstrated the significant potential of Co-MMSNs to shorten the DO treatment duration and effectively reduce the incidence of complications.

Surface imprinted bio-nanocomposites for affinity separation of a cellular DNA repair protein.

Apurinic/apyrimidinic endonuclease 1 (APE1) is a multifunctional DNA repair protein localized in different subcellular compartments. The mechanisms responsible for the highly regulated subcellular localization and "interactomes" of this protein are not fully understood but have been closely correlated to the posttranslational modifications in different biological context. In this work, we attempted to develop a bio-nanocomposite with antibody-like properties that could capture APE1 from cellular matrices to enable the comprehensive study of this protein. By fixing the template APE1 on the avidin-modified surface of silica-coated magnetic nanoparticles, we first added 3-aminophenylboronic acid to react with the glycosyl residues of avidin, followed by addition of 2-acrylamido-2-methylpropane sulfonic acid as the second functional monomer to perform the first step imprinting reaction. To further enhance the affinity and selectivity of the binding sites, we carried out the second step imprinting reaction with dopamine as the functional monomer. After the polymerization, we modified the nonimprinted sites with methoxypoly (ethylene glycol) amine (mPEG-NH2 ). The resulting molecularly imprinted polymer-based bio-nanocomposite showed high affinity, specificity, and capacity for template APE1. It allowed for the extraction of APE1 from the cell lysates with high recovery and purity. Moreover, the bound protein could be effectively released from the bio-nanocomposite with high activity. The bio-nanocomposite offers a very useful tool for the separation of APE1 from various complex biological samples.

Cyano-2-oxopyridines: Green synthesis, cytotoxicity evaluation and molecular docking study

An efficient four-component and one-pot synthesis of 1,6-diamino-3,5-dicyano-2-oxopyridine compounds were investigated in the presence of three catalysts such as bulk and nanosheet graphitic carbon nitride and IS@SMNPs (piperazinium ionic salt attached on silica-coated magnetic nanoparticle) as recyclable heterogeneous catalysts. From the results, the magnetic nanocatalyst was the best among examined catalysts. The highest yield (85%) and the shortest reaction time (40 min) were obtained (for the four-component reaction between benzaldehyde, malononitrile, ethyl cyanoacetate and hydrazine hydrate) in the presence of 50 mg of‏ ‏IS@SMNPs at room temperature. Recycling of IS@SMNPs was tested, and after the fifth cycle, 80% yield was obtained. Good yields in a short time, simple recycling, and being environmentally friendly are advantages of the magnetic catalyst. MTT assay screened the cytotoxicity of 6a, 6b, 6e, and 6h derivatives against two carcinoma cell lines, such as HeLa and MCF-7 (estrogen receptor-dependent). 6h and 6b exhibited the most potent cytotoxicity, respectively, and 6b showed the lowest one against both cell lines. The interactions of selected derivatives and Genistein (an estrogen receptor inhibitor) in the active site of estrogen receptor-α were predicted using molecular docking. The docking results of synthetic compounds illustrated similar interactions to redocked Genistein in the active site, and compounds 6e and 6h had the highest binding affinity.

Green synthesis of silica-coated magnetic nanocarriers for simultaneous purification-immobilization of β-1,3-xylanase

Tailoring magnetic nanocarriers with tunable properties is of great significance for the development of multifunctional candidate materials in numerous fields. Herein, we report a one-pot biomimetic silicification-based method for the synthesis of silica-coated magnetic nanoparticles. The synthesis process was mild, low cost, and highly efficient, which took only about 21 min compared with 4.5–120 h in other literature. Then, the carriers had been characterized by VSM, SEM, TEM, XRD, FT-IR, and EDS to confirm their function. To evaluate the usefulness of the carriers, they were adopted to couple the purification and immobilization of β-1,3-xylanase from the cell lysate in a single step with high immobilization yield (92.8 %) and high activity recovery (82.4 %). The immobilized enzyme also retained 58.4 % of the initial activity after 10 cycles and displayed good storage properties, and improved thermal stability, which would be promising in algae biomass bioconversion as well as other diverse applications.

Rapid and sensitive detection of Pectobacterium carotovorum subsp. carotovorum in fresh produce using silica-coated magnetic nanoparticles combined with filtration-based real-time PCR

Pectobacterium carotovorum subsp. carotovorum (Pcc) possesses a powerful enzymatic mechanism that destroys plant-cell walls. Therefore, Pcc is the etiology of soft-rot disease in several crops and is recognized as one of the most important pathogens in agriculture. Soft-rot is difficult to control at the source when infection occurs. Thus, it is essential to develop sensitivity monitoring and diagnostic methods for timely control measures. Molecular detection methods, such as real-time polymerase chain reaction (PCR), are widely used for detecting Pcc. However, because Pcc is present at low levels in initial soft-rot infection, enrichment and efficient pathogen-separation methods are needed for sensitive monitoring. In this study, filtration was used as a pretreatment method for pathogen concentration, and silica-coated magnetic nanoparticles (SMN)- based real-time PCR was employed to detect low levels of Pcc in fresh produce. As a result, 102 CFU/10 mL was detected by various DNA-extraction methods in pure culture, whereas SMN detected up to 101 CFU/10 mL. In addition, when DNA was extracted using SMN after filtration using a cellulose acetate filter, the sensitivity of real-time PCR was improved to 10° CFU/10 mL. In conclusion, the pretreatment method including SMN, and concentration procedures increased the detection sensitivity by 100-fold; in potato and chicory, 101 CFU/g was detected at a frequency of 90% of the samples, and 10° CFU/g was detected at 70%; and in Kimchi Cabbage, 101 CFU/g was detected at 100% and 10° CFU/g was detected at 80%.

TEMPO and a co-reductant mediated aerobic epoxidation of olefins using a new magnetically recoverable iron(III) bis(phenol)diamine complex: experimental and computational studies.

A magnetically recoverable catalyst of an iron(III) bis(phenol) diamine complex immobilized onto amine functionalized silica-coated magnetic nanoparticles has been synthesized. The catalyst was characterized using FESEM, TEM and XRD which confirmed the nano structure of the catalyst. The physicochemical techniques of ICP, FT-IR, XPS, EDS and TGA proved the loading of the ligand and metal complex on silica-coated magnetic nanoparticles. Using the prepared heterogeneous catalyst, aerobic epoxidation reactions of different alkenes have been investigated in the presence of SO32- as a reducing agent. Moreover, using TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) to discover the mechanism of the aerobic epoxidation of olefins, a new TEMPO-assisted route has been explored. Both of the reaction pathways led to a moderate to high percentage yield of epoxides in water at room temperature. For further understanding mechanistic aspects, density functional theory (DFT) computational studies have been performed. The DFT calculations confirm the suggested mechanism for the title reaction and show the electron density in the vicinity of Fe(II) in the presence of TEMPO as a co-catalyst was more than that in the presence of SO32-.

New iron(iii) complex of bis-bidentate-anchored diacyl resorcinol on a Fe3O4 nanomagnet: C-H bond oxygenation, oxidative cleavage of alkenes and benzoxazole synthesis.

We have synthesized a novel, bis-bidentate, covalently anchored, 4,6-diacetyl resorcinol (DAR) ligand on silica-coated magnetic Fe3O4 nanoparticles and the corresponding bi-metallic iron(iii) complex (Fe3O4@SiO2-APTESFe2LDAR). Both the chemical nature and the structure of the homogeneously heterogenized catalyst were investigated using physico-chemical techniques. The results obtained by XPS, XRD, FT-IR, TGA, VSM, SEM, TEM, EDX, ICP and AAS revealed a magnetic core, a silica layer and the grafting of a binuclear iron complex on the Fe3O4@SiO2-APTES, as well as its thermodynamic stability. Despite many reports of metal complexes on different supports, there are no reports of anchored, bi-metallic complexes. To the best of our knowledge, this is the first report of a bi-active site catalyst covalently attached to a support. This study focuses on the catalytic activity of an as-synthesized, bi-active site catalyst for C-H bond oxygenation, the oxidative cleavage of alkenes, and the multicomponent, one-pot synthesis of benzoxazole derivatives with excellent yields from readily available starting materials. Our results indicated high conversion rates and selectivity under mild reaction conditions and simple separation using a magnetic field. The leaching and recyclability tests of the catalyst were investigated for the above processes, which indicated that all the reactions proceed via a heterogeneous pathway and that the catalyst is recyclable without any tangible loss in catalytic activity for at least 8, 5 and 5 cycles for C-H bond oxygenation, C[double bond, length as m-dash]C bond cleavage and benzoxazole synthesis, respectively.

Fully Integrated Microfluidic Biosensor with Finger Actuation for the Ultrasensitive Detection of Escherichia coli O157:H7.

A portable microfluidic biosensor was developed for the detection of E. coli O157:H7 using finger actuation. The chip was assembled with three functional zones, immunomagnetic separation, nucleic acid extraction and purification, and signal detection. First, antibody-modified magnetic nanoparticles (MNPs) were used to separate the target bacteria from the sample. The captured bacteria were then lysed and silica-coated MNPs were used to absorb DNA, followed by washing and eluting to obtain purified DNA. The obtained DNA was subjected to amplification and fluorescence detection based on the recombinase polymerase amplification-clustered regularly interspaced short palindromic repeat-associated protein/Cas12a reaction. The fluorescence images were collected and analyzed using a smartphone app under a 3D-printed detection device. It could quantitatively detect E. coli O157:H7 from 102 to 108 CFU/mL in 2.5 h with a limit of detection (LOD) of 10 CFU/mL. The recovery rate ranged from 104 to 120%. Overall, the biosensor realizes "sample-in and answer-out" assay for E. coli O157:H7 and eliminates the need for external pumps and skilled personnel.

A multi-component approach for co-immobilization of lipases on silica-coated magnetic nanoparticles: improving biodiesel production from waste cooking oil.

The capability of multi-component reactions in rapid immobilization of enzymes was considered for co-immobilization of Thermomyces lanuginous lipase (TLL) and Candida antarctica lipase B (CALB) [TLL: CALB]; Rhizomucor miehei lipase (RML) and CALB [RML: CALB] on amine-functionalized silica-coated magnetic nanoparticles (Fe3O4@SiO2-NH2). Immobilization of different ratios of lipases was performed within 3h under mild conditions; producing specific activity ranging from 29 to 35 U/mg for TLL:CALB and 21-34 U/mg for RML:CALB. The co-immobilized derivatives showed improved co-solvent and thermal stability compared to the corresponding free enzymes. All the derivatives were also used to catalyze the transesterification of waste cooking oil with methanol to produce biodiesel (fatty acid methyl esters). Response surface method (RSM) and a central composite rotatable design (CCRD) were used to study the effects of different factors on the FAME yield. Fe3O4@SiO2-NH2-RML-CALB and Fe3O4@SiO2-NH2-TLL-CALB had maximum FAME yields of 99-80%, respectively.

In Vivo Capsid Engineering of Bacteriophages for Oriented Surface Conjugation.

The current state-of-the-art in bacteriophage (phage) immobilization onto magnetic particles is limited to techniques that are less expensive and/or facile but nonspecific or those that are more expensive and/or complicated but ensure capsid-down orientation of the phages, as necessary to preserve infectivity and performance in subsequent applications (e.g., therapeutics, detection). These cost, complexity, and effectiveness limitations constitute the major hurdles that limit the scale-up of phage-based strategies and thus their accessibility in low-resource settings. Here, we report a plasmid-based technique that incorporates a silica-binding protein, L2, into the T7 phage capsid, during viral assembly, with and without inclusion of a flexible linker peptide, allowing for targeted binding of the phage capsid to silica without requiring the direct modification of the phage genome. L2-tagged phages were then immobilized onto silica-coated magnetic nanoparticles. Inclusion of the flexible linker between the phage capsid protein and the L2 protein improved immobilization density compared to both wild type T7 phages and L2-tagged phages without the flexible linker. Taken together, this work demonstrates phage capsid modification without engineering the phage genome, which provides an important step toward reducing the cost and increasing the specificity/directionality of phage immobilization methods and could be more broadly applied in the future for other phages for a range of other capsid tags and nanomaterials.

Dose-enhancement of MCF 7 cell line radiotherapy using silica-iron oxide nanocomposite

Cancer radiotherapy is one of the most effective regimens of cancer treatments, but cancer cell radioresistance remains a concern. Radiosensitizers can selectively improve the efficacy of radiotherapy and reduce inherent damage. The purpose of this work is to evaluate the effect of silica-coated iron oxide magnetic nanoparticles (SIONPs) as a radiosensitizer and compare their therapeutic effect with that of Iron oxide magnetic nanoparticles (IONPs). IONPs and SIONPs were characterized using several physical techniques such as a transmission electron microscope (TEM) and Vibrating sample magnetometer (VSM). MTT and DNA double-strand breaks (Comet) assays have been used to detect the cytotoxicity, cell viability, and DNA damage of MCF-7 cells, which were treated with different concentrations of prepared nanoparticles and exposed to an X-ray beam. In this study, an efficient radiosensitizer, SIONPs, was successfully prepared and characterized. With 0.5 Gy dose, dose enhancement factor (DEF) values of cells treated with 5 and 10 μg/ml of IONPs were 1 and 1.09, respectively, while those treated with SIONPs at these concentrations had DEF of 1.21 and 1.32, respectively. Results demonstrated that SIONPs provide a potential for improving the radiosensitivity of breast cancer.

Vancomycin-conjugated polydopamine-coated magnetic nanoparticles for molecular diagnostics of Gram-positive bacteria in whole blood

BackgroundSepsis is caused mainly by infection in the blood with a broad range of bacterial species. It can be diagnosed by molecular diagnostics once compounds in the blood that interfere with molecular diagnostics are removed. However, this removal relies on ultracentrifugation. Immunomagnetic separation (IMS), which typically uses antibody-conjugated silica-coated magnetic nanoparticles (Ab-SiO2-MNPs), has been widely applied to isolate specific pathogens in various types of samples, such as food and environmental samples. However, its direct use in blood samples containing bacteria is limited due to the aggregation of SiO2-MNPs in the blood and inability to isolate multiple species of bacteria causing sepsis.ResultsIn this study, we report the synthesis of vancomycin-conjugated polydopamine-coated (van-PDA-MNPs) enabling preconcentration of multiple bacterial species from blood without aggregation. The presence of PDA and van on MNPs was verified using transmission electron microscopy, X-ray photoelectron spectroscopy, and energy disruptive spectroscopy. Unlike van-SiO2-MNPs, van-PDA-MNPs did not aggregate in the blood. Van-PDA-MNPs were able to preconcentrate several species of Gram-positive bacteria in the blood, lowering the limit of detection (LOD) to 10 colony forming units/mL by polymerase chain reaction (PCR) and quantitative PCR (qPCR). This is 10 times more sensitive than the LOD obtained by PCR and qPCR using van-SiO2-MNPs.ConclusionThese results suggest that PDA-MNPs can avoid aggregation in blood and be conjugated with receptors, thereby improving the sensitivity of molecular diagnostics of bacteria in blood samples.

A novel and efficient magnetically recoverable copper catalyst [MNPs-guanidine-bis(ethanol)-Cu] for Pd-free Sonogashira coupling reaction

We designed and fabricated a copper complex immobilized on the surface of silica-coated magnetic nanoparticles modified with guanidine-bis ethanol (prepared via the ring-opening reaction of MNPs-guanidine with epoxide). FT-IR spectroscopy, Scanning electron microscope (SEM, Transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDS), Thermogravimetric analysis (TGA), Vibrating sample magnetometer (VSM), X-ray diffraction (XRD), Elemental mapping, Atomic absorption spectroscopy (AAS), Inductively Coupled Plasma Optical Emission spectroscopy (ICP-OES) and Elemental mapping-analysis were used to characterize the structure of MNPs-guanidine-bis(ethanol)-Cu nanocatalyst. The MNPs-guanidine-bis(ethanol)-Cu nanocomposite showed high catalytic activity in the Pd-free Sonogashira cross-coupling reactions. The MNPs-guanidine-bis(ethanol)-Cu catalyst was consistent toward a variety of aryl halides bearing amine, acid, aldehyde, nitro, etc., functional groups, where high-to-excellent yields were obtained for all substrates. The copper nanocatalyst could be easily recovered by a simple magnetic separation and recycled at least 8 times without deterioration in catalytic activity.

Preparation of novel bifunctionalized magnetic nanoparticles for sequential speciation analysis of inorganic arsenic

An amino- and mercapto-bifunctionalized magnetic nanocomposite (SMNPs-(NH2 + SH)) was synthesized by modification of silica-coated magnetic nanoparticles (SMNPs) via one-pot co-condensation of 3-aminopropyltriethoxysilane (APTES) and 3-mercaptopropyltrimethoxysilane (MPTMS) for the first time. The bifunctional magnetic nanomaterial was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectrometry, X-ray photoelectric spectroscopy, elemental analysis, thermogravimetric analysis and vibrating sample magnetometry, etc. The prepared SMNPs-(NH2 + SH) nanocomposite was employed as magnetic solid-phase extraction (MSPE) sorbent for speciation of inorganic arsenic without any pre-oxidation or pre-reduction process. Different optimal conditions for the MSPE including sample solution pH and volume, adsorbent amount, loading time, eluent composition and volume, and elution time were investigated systematically. As(V) and As(III) were adsorbed simultaneously at pH 4.0, and then desorbed sequentially by 3 % (v/v) HNO3 and 3 % (v/v) HNO3 with 4 % (m/v) mercaptosuccinic acid followed by inductively coupled plasma-mass spectrometry (ICP-MS) analysis with the limits of detection of 15.2 and 24.5 ng/L respectively at an enrichment factor of 10 fold. The reliability of the stepwise speciation strategy based on SMNPs-(NH2 + SH) was validated by analyzing inorganic arsenic species in certified reference material of environmental water as well as mixed standard solutions of As(V) and As(III), and the results were in good accordance with the certified or standard values. The applicability of the SMNPs-(NH2 + SH)-MSPE-ICP-MS method for speciation analysis of inorganic arsenic was evaluated in spiked tap, rain, lake and river water samples at the recoveries of 92 %–102 % and 92 %–100 % with the relative standard deviations of 3.6 %–7.4 % and 2.3 %–8.2 % for As(V) and As(III) respectively. In consideration of the merits of single adsorbent, facile preparation, easy operation and no invasion to labile inorganic arsenic, the bifunctional material based MSPE protocol is attractive for speciation analysis of arsenic in real environmental samples.

Fe3O4@SiO2@VAN Nanoadsorbent Followed by GC-MS for the Determination of Polycyclic Aromatic Hydrocarbons at Ultra-Trace Levels in Environmental Water Samples.

In the present study, silica-coated magnetic nanoparticles functionalized with vancomycin (Fe3O4@SiO2@VAN) were synthesized. The Fe3O4@SiO2@VAN nanocomposite was used as a sorbent for the magnetic solid-phase extraction (MSPE) of polycyclic aromatic hydrocarbons (PAHs) from environmental water, followed by GC-MS. The nanocomposite was characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, and nitrogen sorption. Various experimental parameters were optimized, including extraction condition and desorption condition. Results show that Fe3O4@SiO2@VAN combined the advantages of nanomaterials and magnetic separation technology, showing excellent dispersibility and high selectivity for PAHs in environmental water sample. Under the optimal extraction conditions, an analytical method was established with the sensitive limit of detection (LOD) of 0.03–0.16 μg L−1. The method was successfully applied for the analysis of environmental water samples. The relative standard deviations (%) were in the range of 0.50–12.82%, and the extraction recovery (%) was in the range of 82.48% and 116.32%. MSPE-coupled gas chromatography–mass spectrometry quantification of PAHs is an accurate and repeatable method for the monitoring of PAH accumulation in environmental water samples. It also provides an effective strategy for the tracing and quantification of other environmental pollutants in complex samples.

Tribromide immobilized on surface of magnetic nanoparticles modified tris(triazine-triamine): A versatile and highly active catalyst for oxidation of sulfides and oxidative coupling of thiols

In this article, we show that tribromide heterogenized on the surface of silica-coated magnetic nanoparticles modified with N2,N4,N6-tris(aminomethyl)-1,3,5-triazine-2,4,6-triamine [Fe3O4@SiO2-tris(triazine-triamine)-Br3] is a novel and efficient reusable nanocatalyst for the oxidation of sulfides to sulfoxides and oxidative coupling of thiols to disulfides using hydrogen peroxide as green oxidant. The structure of the as-fabricated Fe3O4@SiO2-tris(triazine-triamine)-Br3 was characterized by a series of spectroscopic techniques including FT-IR spectroscopy, SEM, TEM, EDX, VSM, XRD and TGA techniques. TEM and SEM analysis confirmed that the typical silica shell thickness was assessed to be around 20 nm. Recycling studies revealed that the Fe3O4@SiO2-tris(triazine-triamine)-Br3 could be easily recovered by a simple magnetic separation and recycled at least 6 times without deterioration in catalytic activity.